,radioisotopes in ,medicine ,the ,understanding the ,atom ,series ,nuclear energy is playing a vital role in the life of every man1 woman1 and child in the ,united ,states today4 ,in the years ahead it will affect increasingly all the peoples of the earth4 ,it is essential that all ,americans gain an understanding of this vital force if they are to discharge thoughtfully their responsibilities as citizens and if they are to realize fully the myriad benefits that nuclear energy offers them4 ,the ,united ,states ,atomic ,energy ,commission provides this booklet to help you achieve such understanding4 ,illustration3 ,edward ,j4 ,brunenkant ,edward ,j4 ,brunenkant1 ,director ,division of ,technical ,information ,,united ,,states ,,atomic ,,energy ,,commission ,dr4 ,glenn ,t4 ,seaborg1 ,chairman ,james ,t4 ,ramey ,wilfrid ,e4 ,johnson ,dr4 ,theos ,j4 ,thompson ,dr4 ,clarence ,e4 ,larson ,radioisotopes in ,medicine by ,earl ,w4 ,phelan ,,contents ,,introduction #a ,history #a ,what ,is ,radiation8 #e ,what ,is ,radioactivity8 #e ,what ,are ,radioisotopes8 #f ,how ,are ,radioisotopes ,used8 #g ,what ,do ,we ,mean by ,tracer ,atoms8 #i ,,diagnosis #aa ,pinpointing ,disease #aa ,arsenic-#gd #ad ,chromium-#ea #ae ,cobalt-#fj #af ,iodine-#aca #ah ,iron-#ei #bc ,phosphorus-#cb #bd ,sodium-#bd #be ,technetium-#iim #bf ,thulium-#agj and ,gamma ,radiography #bg ,tritium #bh ,activation ,analysis #cj ,summary #cj ,,therapy #ca ,a ,successful ,case #ca ,general ,principles #cb ,iodine-#aca and ,iodine-#acb #cb ,boron-#aj #cc ,phosphorus-#cb #ce ,gold-#aih #cg ,beads1 ,needles1 and ,applicators #ch ,teletherapy #da ,,conclusions #dc ,,appendix #dd ,,suggested ,,references #dg ,united ,states ,atomic ,energy ,commission ,division of ,technical ,information ,library of ,congress ,catalog ,card ,number3 #ff-fbgdi #aiff ,illustration3 ,,the ,,cover ,this multi-detector positron scanner is used to locate tumors4 ,a radioisotope-labeled substance is injected into the body and subsequently concentrates in the tumor tissue4 ,the radioisotope emits positrons that immediately decay and produce two gamma rays that travel in opposite directions4 ,these rays are detected simultaneously on a pair of opposing detection crystals and a line is established along which the tumor is located4 ,this method is one of many ways doctors use radioisotopes to combat disease4 ,in this1 as in many other procedures described in this booklet1 the patient remains comfortable at all times4 ,illustration3 ,,the ,,author ,earl ,w4 ,phelan is ,professor of ,chemistry at ,tusculum ,college1 ,greeneville1 ,tennessee4 ,from #aieb to #aife1 he served as ,staff ,assistant in the ,laboratory ,director's ,office at ,argonne ,national ,laboratory1 where his duties included editing the ,argonne ,reviews and supplying information to students4 ,for #bb years prior to moving to ,argonne he served as ,head of the ,chemistry ,department of the ,valdosta ,state ,college ,in ,georgia4 ,he received his ,b4,s4 and ,ph4,d4 degrees from ,cornell ,university4 ,radioisotopes in ,medicine ,by ,,earl ,w4 ,,phelan ,,introduction ,history ,the history of the use of radioisotopes for medical purposes is filled with names of ,nobel ,prize winners4 ,it is inspiring to read how great minds attacked puzzling phenomena1 worked out the theoretical and practical implications of what they observed1 and were rewarded by the highest honor in science4 ,for example1 in #ahie a ,german physicist1 ,wilhelm ,konrad ,roentgen1 noticed that certain crystals became luminescent when they were in the vicinity of a highly evacuated electric-discharge tube4 ,objects placed between the tube and the crystals screened out some of the invisible radiation that caused this effect1 and he observed that the greater the density of the object so placed1 the greater the screening effect4 ,he called this new radiation ,x rays1 because x was the standard algebraic symbol for an unknown quantity4 ,his discovery won him the first ,nobel ,prize in physics in #aija4 ,illustration3 ,wilhelm ,roentgen ,a ,french physicist1 ,antoine ,henri ,becquerel1 newly appointed to the chair of physics at the ,ecole ,polytechnique in ,paris1 saw that this discovery opened up a new field for research and set to work on some of its ramifications4 ,one of the evident features of the production of ,x rays was the fact that while they were being created1 the glass of the vacuum tube gave off a greenish phosphorescent glow4 ,this suggested to several physicists that substances which become phosphorescent upon exposure to visible light might give off ,x rays along with the phosphorescence4 ,becquerel experimented with this by exposing various crystals to sunlight and then placing each of them on a black paper envelope enclosing an unexposed photographic plate4 ,if any ,x rays were thus produced1 he reasoned1 they would penetrate the wrapping and create a developable spot of exposure on the plate4 ,to his delight1 he indeed observed just this effect when he used a phosphorescent material1 uranium potassium sulfate4 ,then he made a confusing discovery4 ,for several days there was no sunshine1 so he could not expose the phosphorescent material4 ,for no particular reason 7other than that there was nothing else to do7 ,becquerel developed a plate that had been in contact with uranium material in a dark drawer1 even though there had been no phosphorescence4 ,the telltale black spot marking the position of the mineral nevertheless appeared on the developed plate6 ,his conclusion was that uranium in its normal state gave off ,x rays or something similar4 ,illustration3 ,henri ,becquerel ,at this point1 ,pierre ,curie1 a friend of ,becquerel and also a professor of physics in ,paris1 suggested to one of his graduate students1 his young bride1 ,marie1 that she study this new phenomenon4 ,she found that both uranium and thorium possessed this property of radioactivity1 but also1 surprisingly1 that some uranium minerals were more radioactive than uranium itself4 ,through a tedious series of chemical separations1 she obtained from pitchblende 7a uranium ore7 small amounts of two new elements1 polonium and radium1 and showed that they possessed far greater radioactivity than uranium itself4 ,for this work ,becquerel and the two ,curies were jointly awarded the ,nobel ,prize in physics in #aijc4 ,illustration3 ,pierre and ,marie ,curie ,at the outset1 ,roentgen had noticed that although ,x rays passed through human tissue without causing any immediate sensation1 they definitely affected the skin and underlying cells4 ,soon after exposure1 it was evident that ,x rays could cause redness of the skin1 blistering1 and even ulceration1 either in single doses or in repeated smaller doses4 ,in spite of the hazards#a involved1 early experimenters determined that ,x rays could destroy cancer tissues more rapidly than they affected healthy organs1 so a basis was established quite soon for one of ,medicine's few methods of curing or at least restraining cancer4 ,the work of the ,curies in turn stimulated many studies of the effect of radioactivity4 ,it was not long before experimenters learned that naturally radioactive elements--like radium--were also useful in cancer therapy4 ,these elements emitted gamma rays1#b which are like ,x rays but usually are even more penetrating1 and their application often could be controlled better than ,x rays4 ,slowly1 over the years1 reliable methods were developed for treatment with these radioactive sources1 and instruments were designed for measuring the quantity of radiation received by the patient4 ,illustration3 ,frederic and ,irene ,joliot-,curie ,the next momentous advance was made by ,frederic ,joliot1 a ,french chemist who married ,irene ,curie1 daughter of ,pierre and ,marie ,curie4 ,he discovered in #aicd that when aluminum was bombarded with alpha particles#c from a radioactive source1 emission of positrons 7positive electrons7 was induced4 ,moreover1 the emission continued long after the alpha source was removed4 ,this was the first example of artificially induced radioactivity1 and it stimulated a new flood of discoveries4 ,frederic and ,irene ,joliot-,curie won the ,nobel ,prize in chemistry in #aice for this work4 ,others who followed this discovery with the development of additional ways to create artificial radioactivity were two ,americans1 ,h4 ,richard ,crane and ,c4 ,c4 ,lauritsen1 the ,british scientists1 ,john ,cockcroft and ,e4 ,t4 ,s4 ,walton1 and an ,american1 ,robert ,j4 ,van de ,graaff4 ,ernest ,o4 ,lawrence1 an ,american physicist1 invented the cyclotron 7or 8atom smasher071 a powerful source of high-energy particles that induced radioactivity in whatever target materials they impinged upon4 ,enrico ,fermi1 an ,italian physicist1 seized upon the idea of using the newly discovered neutron 7an electrically neutral particle7 and showed that bombardment with neutrons also could induce radioactivity in a target substance4 ,cockcroft and ,walton1 ,lawrence1 and ,fermi all won ,nobel ,prizes for their work4 ,patient application of these new sources of bombarding particles resulted in the creation of small quantities of hundreds of radioactive isotopic species1 each with distinctive characteristics4 ,in turn1 as we shall see1 many ways to use radioisotopes have been developed in medical therapy1 diagnosis1 and research4 ,by now1 more than #cjjj hospitals hold licenses from the ,atomic ,energy ,commission to use radioisotopes4 ,in addition1 many thousands of doctors1 dentists1 and hospitals have ,x-ray machines that they use for some of the same broad purposes4 ,one of the results of all this is that every month new uses of radioisotopes are developed4 ,more persons are trained every year in methods of radioisotope use and more manufacturers are producing and packaging radioactive materials4 ,this booklet tells some of the successes achieved with these materials for medical purposes4 ,what ,is ,radiation8 ,radiation is the propagation of radiant energy in the form of waves or particles4 ,it includes electromagnetic radiation ranging from radio waves1 infrared heat waves1 visible light1 ultraviolet light1 and ,x rays to gamma rays4 ,it may also include beams of particles of which electrons1 positrons1 neutrons1 protons1 deuterons1 and alpha particles are the best known4#d ,what ,is ,radioactivity8 ,it took several years following the basic discovery by ,becquerel1 and the work of many investigators1 to systematize the information about this phenomenon4 ,radioactivity is defined as the property1 possessed by some materials1 of spontaneously emitting alpha or beta particles or gamma rays as the unstable 7or radioactive7 nuclei of their atoms disintegrate4 ,what ,are ,radioisotopes8 ,illustration3 ,frederick ,soddy ,in the #aith ,century an ,englishman1 ,john ,dalton1 put forth his atomic theory1 which stated that all atoms of the same element were exactly alike4 ,this remained unchallenged for #ajj years1 until experiments by the ,british chemist1 ,frederick ,soddy1 proved conclusively that the element neon consisted of two different kinds of atoms4 ,all were alike in chemical behavior but some had an atomic weight 7their mass relative to other atoms7 of #bj and some a weight of #bb4 ,he coined the word isotope to describe one of two or more atoms having the same atomic number but different atomic weights4#e ,radioisotopes are isotopes that are unstable1 or radioactive1 and give off radiation spontaneously4 ,many radioisotopes are produced by bombarding suitable targets with neutrons now readily available inside atomic reactors4 ,some of them1 however1 are more satisfactorily created by the action of protons1 deuterons1 or other subatomic particles that have been given high velocities in a cyclotron or similar accelerator4 ,radioactivity is a process that is practically uninfluenced by any of the factors1 such as temperature and pressure1 that are used to control the rate of chemical reactions4 ,the rate of radioactive decay appears to be affected only by the structure of the unstable 7decaying7 nucleus4 ,each radioisotope has its own half-life1 which is the time it takes for one half the number of atoms present to decay4 ,these half-lives vary from fractions of a second to millions of years1 depending only upon the atom4 ,we shall see that the half-life is one factor considered in choosing a particular isotope for certain uses4 ,illustration3 ,,half-,,life ,,pattern ,,of ,,strontium-#ij ,percent of #ajj #ej #be #ab4e #f4ge ,radioactivity ,beginning #a #b #c #d of ,life ,half-life ,half-lives ,half-lives ,half-lives #bh years #ef years #hd years #aab years ,most artificially made radioisotopes have relatively short half-lives4 ,this makes them useful in two ways4 ,first1 it means that very little material is needed to obtain a significant number of disintegrations4 ,it should be evident that1 with any given number of radioactive atoms1 the number of disintegrations per second will be inversely proportional to the half-life4 ,second1 by the time #aj half-lives have elapsed1 the number of disintegrations per second will have dwindled to _/ the original number1 and the amount of radioactive material is so small it is usually no longer significant4 7,note the decrease in the figure above47 ,how ,are ,radioisotopes ,used8 ,a radioisotope may be used either as a source of radiation energy 7energy is always released during decay71 or as a tracer3 an identifying and readily detectable marker material4 ,the location of this material during a given treatment can be determined with a suitable instrument even though an unweighably small amount of it is present in a mixture with other materials4 ,on the following pages we will discuss medical uses of individual radioisotopes--first those used as tracers and then those used for their energy4 ,in general1 tracers are used for analysis and diagnosis1 and radiant-energy emitters are used for treatment 7therapy74 ,radioisotopes offer two advantages4 ,first1 they can be used in extremely small amounts4 ,as little as one-billionth of a gram can be measured with suitable apparatus4 ,secondly1 they can be directed to various definitely known parts of the body4 ,for example1 radioactive sodium iodide behaves in the body just the same as normal sodium iodide found in the iodized salt used in many homes4 ,the iodine concentrates in the thyroid gland where it is converted to the hormone thyroxin4 ,other radioactive1 or 8tagged01 atoms can be routed to bone marrow1 red blood cells1 the liver1 the kidneys1 or made to remain in the blood stream1 where they are measured using suitable instruments4#f ,of the three types of radiation1 alpha particles 7helium nuclei7 are of such low penetrating power that they cannot be used for measurement from outside the body4 ,beta particles 7electrons7 have a moderate penetrating power1 therefore they produce useful therapeutic results in the vicinity of their release1 and they can be detected by sensitive counting devices4 ,gamma rays are highly energetic1 and they can be readily detected by counters--radiation measurement devices--used outside the body4 ,illustration3 ,relative penetration of alpha1 beta1 and gamma radiation4 ,for comparison1 a sheet of paper stops alpha particles1 a block of wood stops beta particles1 and a thick concrete wall stops gamma rays4 ,in one way or another1 the key to the usefulness of radioisotopes lies in the energy of the radiation4 ,when radiation is used for treatment1 the energy absorbed by the body is used either to destroy tissue1 particularly cancer1 or to suppress some function of the body4 ,properly calculated and applied doses of radiation can be used to produce the desired effect with minimum side reactions4 ,expressed in terms of the usual work or heat units1 ergs or calories1 the amount of energy associated with a radiation dose is small4 ,the significance lies in the fact that this energy is released in such a way as to produce important changes in the molecular composition of individual cells within the body4 ,what ,do ,we ,mean by ,tracer ,atoms8 ,when a radioisotope is used as a tracer1 the energy of the radiation triggers the counting device1 and the exact amount of energy from each disintegrating atom is measured4 ,this differentiates the substance being traced from other materials naturally present4 ,illustration3 ,this is the first photoscanner1 which was developed in #aied at the ,university of ,pennsylvania and was retired from service in #aifc4 ,when gamma rays emitted by a tracer isotope in the patient's body struck the scanner1 a flashing light produced a dot on photographic film4 ,the intensity of the light varied with the counting rate and thus diseased tissues that differed little from normal tissue except in their uptake of an isotope could be discerned4 ,with one conspicuous exception1 it is impossible for a chemist to distinguish any one atom of an element from another4 ,once ordinary salt gets into the blood stream1 for example1 it normally has no characteristic by which anyone can decide what its source was1 or which sodium atoms were added to the blood and which were already present4 ,the exception to this is the case in which some of the atoms are 8tagged0 by being made radioactive4 ,then the radioactive atoms are readily identified and their quantity can be measured with a counting device4 ,a radioactive tracer1 it is apparent1 corresponds in chemical nature and behavior to the thing it traces4 ,it is a true part of it1 and the body treats the tagged and untagged material in the same way4 ,a molecule of hemoglobin carrying a radioactive iron atom is still hemoglobin1 and the body processes affect it just as they do an untagged hemoglobin molecule4 ,the difference is that a scientist can use counting devices to follow the tracer molecules wherever they go4 ,illustration3 ,one of the first scans made by a photoscanner4 ,the photorecording 7dark bands71 superimposed on an ,x-ray picture for orientation1 shows radioactivity in a cancer in the patient's neck4 ,it should be evident that tracers used in diagnosis--to identify disease or improper body function--are present in such small quantities that they are relatively harmless4 ,their effects are analogous to those from the radiation that every one of us continually receives from natural sources within and without the body4 ,therapeutic doses--those given for medical treatment--by contrast1 are given to patients with a disease that is in need of control1 that is1 the physician desires to destroy selectively cells or tissues that are abnormal4 ,in these cases1 therefore1 the skill and experience of the attending physician must be applied to limit the effects to the desired benefits1 without damage to healthy organs4 ,this booklet is devoted to these two functions of radioisotopes1 diagnosis and therapy2 the field of medical research using radioactive tools is so large that it requires separate coverage4#g ,,diagnosis ,pinpointing ,disease ,mr4 ,peters1 #ce-year-old father of four and a resident of ,chicago's northwest side1 went to a ,chicago hospital one winter day after persistent headaches had made his life miserable4 ,routine examinations showed nothing amiss and his doctor ordered a 8brain scan0 in the hospital's department of nuclear medicine4 ,thirty minutes before 8scan time01 ,mr4 ,peters was given1 by intravenous injection1 a minute amount of radioactive technetium4 ,this radiochemical had been structured so that1 if there were a tumor in his cranium1 the radioisotopes would be attracted to it4 ,then he was positioned so an instrument called a scanner could pass close to his head4 ,as the motor-driven scanner passed back and forth1 it picked up the gamma rays being emitted by the radioactive technetium1 much as a ,geiger counter detects other radiation4 ,these rays were recorded as black blocks on sensitized film inside the scanner4 ,the result was a piece of exposed film that1 when developed1 bore an architectural likeness or image of ,mr4 ,peters' cranium4 ,illustration3 ,the inset picture shows a brain scan made with a positron scintillation camera4 ,a tumor is indicated by light area above ear4 7,light area in facial region is caused by uptake in bone and extracellular space47 ,the photograph shows a patient1 completely comfortable1 receiving a brain scan on one of the three rectilinear scanning devices in the nuclear medicine laboratory of a hospital4 ,mr4 ,peters1 who admitted to no pain or other adverse reaction from the scanning1 was photographed by the scanner from the front and both sides4 ,the procedure took less than an hour4 ,the developed film showed that the technetium had concentrated in one spot1 indicating definitely that a tumor was present4 ,comparison of front and side views made it possible to pinpoint the location exactly4 ,surgery followed to remove the tumor4 ,today1 thanks to sound and early diagnosis1 ,mr4 ,peters is well and back on the job4 ,his case is an example of how radioisotopes are used in hospitals and medical centers for diagnosis4 ,illustration3 ,the first whole body scanner1 which was developed at the ,donner ,laboratory in #aieb and is still being used4 ,the lead collimator contains #aj scintillation counters and moves across the subject4 ,the bed is moved and serial scans are made and then joined together to form a head-to-toe picture of the subject4 ,illustration3 ,the diagram shows a scan and the parts of a scanner4 7,also see page #ba47 ,in one representative hospital1 #ag different kinds of radioisotope measurements are available to aid physicians in making their diagnoses4 ,all the methods use tracer quantities of materials4 ,other hospitals may use only a few of them1 some may use even more4 ,in any case they are merely tools to augment the doctors' skill4 ,examples of measurements that can be made include blood volume1 blood circulation rate1 red blood cell turnover1 glandular activity1 location of cancerous tissue1 and rates of formation of bone tissue or blood cells4 ,of the more than #ajj different radioisotopes that have been used by doctors during the past #cj years1 five have received by far the greatest attention4 ,these are iodine-#aca1 phosphorus-#cb1 gold-#aih1 chromium-#ea1 and iron-#ei4 ,some others have important uses1 too1 but have been less widely employed than these five4 ,the use of individual radioisotopes in making important diagnostic tests makes a fascinating story4 ,typical instances will be described in the following pages4 ,illustration3 ,a differential multi-detector developed at ,brookhaven ,national ,laboratory locates brain tumors with positron-emitting isotopes4 ,by using many pairs of detection crystals1 the device shortens the scanning time and increases accuracy4 7,see cover for another type of positron scanner47 ,arsenic-#gd ,brain tumors tend to concentrate certain ions 7charged atoms or molecules74 ,when these ions are gamma-ray emitters1 it is possible to take advantage of the penetrating power of their gamma rays to locate the tumor with a scanning device located outside the skull4 ,arsenic-#gd and copper-#fd are isotopes emitting positrons1#h which have one peculiar property4 ,immediately after a positron is emitted from a nucleus it decays1 producing two gamma rays that travel in exactly opposite directions4 ,the scanning device has two detectors called scintillation counters1 one mounted on each side of the patient's head4 ,the electrical circuitry in the scanner is such that only those gamma rays are counted that impinge simultaneously on both counters4 ,this procedure eliminates most of the 8noise01 or scattered and background radiation4 ,chromium-#ea ,because chromium1 in the molecule sodium chromate1 attaches itself to red blood cells1 it is useful in several kinds of tests4 ,the procedures are slightly complicated1 but yield useful information4 ,in one1 a sample of the patient's blood is withdrawn1 stabilized with heparin 7to prevent clotting7 and incubated with a tracer of radioactive sodium chromate4 ,excess chromate that is not taken up by the cells is reduced and washed away4 ,then the radioactivity of the cells is measured1 just before injection into the patient4 ,after a suitable time to permit thorough mixing of the added material throughout the blood stream1 a new blood sample is taken and its radioactivity is measured4 ,the total volume of red blood cells then can be calculated by dividing the total radioactivity of the injected sample by the activity per milliliter of the second sample4 ,illustration3 ,spleen scans made with red blood cells1 which had been altered by heat treatment and tagged with chromium-#ea4 ,such damaged cells are selectively removed by the spleen4 ,a is a normal spleen4 ,b shows an abscess in the spleen4 ,note dark ring of radioactivity surrounding the lighter area of decreased activity at the central portion of spleen4 ,in certain types of anemia the patient's red blood cells die before completing the usual red-cell lifetime of about #abj days4 ,to diagnose this1 red cells are tagged with chromium-#ea 7,cr7 in the manner just described4 ,then some of them are injected back into the patient and an identical sample is injected into a compatible normal individual4 ,if the tracer shows that the cells' survival time is too short in both recipients to the same degree1 the conclusion is that the red cells themselves must be abnormal4 ,on the other hand1 if the cell-survival time is normal in the normal individual and too short in the patient1 the diagnosis is that the patient's blood contains some substance that destroys the red cells4 ,when chromium trichloride1 ,cr,cl1 is used as the tagging agent1 the chromium is bound almost exclusively to plasma proteins1 rather than the red cells4 ,chromium-#ea may thus be used for estimating the volume of plasma circulating in the heart and blood vessels4 ,the same type of computation is carried on for red cells 7after correction for a small amount of chromium taken up by the red blood cells74 ,this procedure is easy to carry out because the radioactive chromium chloride is injected directly into a vein4 ,an ingenious automatic device has been devised for computing a patient's total blood volume using the ,cr measurement of the red blood cell volume as its basis4 ,this determination of total blood volume is of course necessary in deciding whether blood or plasma transfusions are needed in cases involving bleeding1 burns1 or surgical shock4 ,this ,cr procedure was used during the ,korean ,war to determine how much blood had been lost by wounded patients1 and helped to save many1 many lives4 ,for several years1 iodine-#aca has been used as a tracer in determining cardiac output1 which is the rate of blood flow from the heart4 ,it has appeared recently that red blood cells tagged with ,cr are more satisfactory for this measurement than iodine-labeled albumin in the blood serum4 ,it is obvious that the blood-flow rate is an extremely important physiological quantity1 and a doctor must know it to treat either heart ailments or circulatory disturbances4 ,in contrast to the iodine-#aca procedure1 which requires that an artery be punctured and blood samples be removed regularly for measurement1 chromium labeling merely requires that a radiation counter be mounted on the outside of the chest over the aorta 7main artery leaving the heart74 ,a sample of labeled red blood cells is introduced into a vein1 and the recording device counts the radioactivity appearing in the aorta as a function of time4 ,eventually1 of course1 the counting rate 7the number of radioactive disintegrations per second7 levels off when the indicator sample has become mixed uniformly in the blood stream4 ,from the shape of the curve on which the data are recorded during the measurements taken before that time1 the operator calculates the heart output per second4 ,illustration3 ,in this cardiac output study a probe is positioned over the heart and the passage of iodine-#aca labeled human serum albumin through this area is recorded4 ,obstetricians caring for expectant mothers use red cells tagged with ,cr to find the exact location of the placenta4 ,for example1 in the condition known as placenta previa1 the placenta--the organ within the uterus by which nourishment is transferred from the mother's blood to that of the unborn child--may be placed in such a position that fatal bleeding can occur4 ,a radiation-counting instrument placed over the lower abdomen gives information about the exact location of the placenta4 ,if an abnormal situation exists1 the attending physician is then alert and ready to cope with it4 ,the advantages of chromium over iodine-#aca1 which has also been used1 are that smaller doses are required1 and that there is no transfer of radioactivity to the fetal circulation4 ,still another common measurement using ,cr-labeled red blood cells is the determination of the amount and location of bleeding from the gastrointestinal tract 7the stomach and bowels74 ,the amount is found by simple measurement of chromium in the blood that appears in the stools4 ,to find the location is slightly more complicated4 ,the intestinal contents are sampled at different levels through an inserted tube1 and the radiation of the samples determined separately4 ,finally1 gastrointestinal loss of protein can be measured with the aid of ,cr-labeled blood serum4 ,the serum is treated with ,cr,cl and then injected into a vein4 ,in several very serious ailments there is serious loss of blood protein through the intestines4 ,in these conditions the ,cr level in the intestinal excretions is high1 and this alerts the doctor to apply remedial measures4 ,cobalt-#fj ,vitamin ,b is a cobalt compound4 ,normally the few milligrams of ,b in the body are stored in the liver and released to the blood stream as needed4 ,in pernicious anemia1 a potentially fatal but curable disease1 the ,b content of the blood falls from the usual level of #cjj-ijj micromicrograms per milliliter 7ml7 to #j to #ajj micromicrograms per ml4 ,the administration of massive doses of ,b is the only known remedy for this condition4 ,if the ,b is labeled with radioactive cobalt1 its passage into the blood stream may be observed by several different methods4 ,the simplest is to give the ,b by mouth1 and after about #h hours study the level of cobalt radioactivity in the blood4 ,cobalt-#fj has been used for several years1 but recently cobalt-#eh has been found more satisfactory4 ,it has a half-life of #gb days while ,co has a #e4c-year half-life4 ,this reduces greatly the amount of radiation to the patient's liver by the retained radioactivity4 ,iodine-#aca ,like chromium-#ea1 iodine is a versatile tracer element4 ,it is used to determine blood volume1 cardiac output1 plasma volume1 liver activity1 fat metabolism1 thyroid cancer metastases1 brain tumors1 and the size1 shape1 and activity of the thyroid gland4 ,illustration3 ,a linear photoscanner produced these pictures of 7,a7 a normal thyroid1 7,b7 an enlarged thyroid1 and 7,c7 a cancerous thyroid4 ,because of its unique connection with the thyroid gland1 iodine-#aca is most valuable in measurements connected with that organ4 ,thyroxin1 an iodine compound1 is manufactured in the thyroid gland1 and transferred by the blood stream to the body tissues4 ,the thyroxin helps to govern the oxygen consumption of the body and therefore helps control its metabolism4 ,proper production of thyroxin is essential to the proper utilization of nutrients4 ,lowered metabolism means increased body weight4 ,lowered thyroid activity may mean expansion of the gland1 causing one form of goiter4 ,iodine-#aca behaves in the body just as the natural non-radioactive isotope1 iodine-#abg1 does1 but the radioactivity permits observation from outside the body with some form of radiation counter4 ,iodine can exist in the body in many different chemical compounds1 and the counter can tell where it is but not in what form4 ,hence chemical manipulation is necessary in applying this technique to different diagnostic procedures4 ,the thyroid gland1 which is located at the base of the neck1 is very efficient in trapping inorganic iodide from the blood stream1 concentrating and storing the iodine-containing material and gradually releasing it to the blood stream in the form of protein-bound iodine 7,,pbi74 ,one of the common diagnostic procedures for determining thyroid function1 therefore1 is to measure the percentage of an administered dose of ,i that is taken up by the gland4 ,usually the patient is given a very small dose of radioactive sodium iodide solution to drink1 and two hours later the amount of iodine in the gland is determined by measuring the radiation coming from the neck area4 ,in hyperthyroidism1 or high thyroid gland activity1 the gland removes iodide ions from the blood stream more rapidly than normal4 ,illustration3 ,screening test for ,hyperthyroidism ,oral dose ,i ,graph of ,uptake in #a hour 7,percent of administered dose7 versus ,uptake in #bd hours 7,percent of administered dose7 ,illustration3 ,it is especially important in isotope studies on infants and small children that the radiation exposure be low4 ,by carrying out studies in the whole body counter room1 the administered dose can be greatly reduced4 ,the photographs illustrate a technique of measuring radioiodine uptake in the thyroid gland with extremely small amounts of a mixture of iodine-#aca and iodine-#abe4 ,a shows a small television set that is mounted above the crystal in such a way that good viewing requires that the head be kept in the desired position4 ,this helps solve the problem of keeping small children still during a #ae-minute counting period4 ,b shows a child in position for a thyroid uptake study4 ,this simple procedure has been used widely4 ,one difficulty in using it is that its success is dependent upon the time interval between injection and measurement4 ,an overactive gland both concentrates iodine rapidly and also discharges it back to the blood stream as ,,pbi more rapidly than normal4 ,modifications of the test have been made to compare the amount of iodine-#aca that was administered with the amount circulating in the blood as ,,pbi4 ,the system acquires chemical separation of the two forms of iodine from a sample of blood removed from a vein1 followed by separate counting4 ,this computation of the 8conversion ratio0 of radioactive plasma ,,pbi to plasma-total ,i gives results that are less subject to misinterpretation4 ,to determine local activity in small portions of the thyroid1 an automatic scanner is used4 ,a collimator#i shields the detector 7a ,geiger-,mller tube or scintillating crystal7 so that only those impulses originating within a very small area are accepted by the instrument4 ,the detector is then moved back and forth slowly over the entire area and the radiation is automatically recorded at definite intervals1 creating a 8map0 of the active area4 ,in cases where lumps1 or nodules1 have been discovered in the thyroid1 the map is quite helpful in distinguishing between cancerous and benign nodules4 ,the former are almost always less radioactive than surrounding tissues4 ,illustration3 ,seven serial scans made with the whole body scanner were put together to provide a whole body scan of this patient with thyroid cancer that had spread to the lung4 ,one millicurie of iodine-#aca was administered and the scan made #gb hours later4 ,note the uptake in the lung4 ,this patient was successfully treated with large doses of iodine-#aca4 ,fragments of cancerous thyroid tissue may migrate to other parts of the body and grow there4 ,these new cancers are known as metastatic cancers and are a signal of an advanced state of disease4 ,in such a situation even complete surgical removal of the original cancer may not save the patient4 ,if these metastases are capable of concentrating iodine 7less than #aj of them are71 they can be located by scanning the whole body in the manner that was just described4 ,when a thyroid cancer is discovered1 therefore1 a doctor may look for metastases before deciding to operate4 ,human blood serum albumin labeled with ,i is used for measurement of the volume of circulating plasma4 ,the procedure is quite similar to that used with radioactive chromium4 ,iodinated human serum albumin labeled with ,i is injected into a vein4 ,then1 after allowing time for complete mixing of the sample with the blood1 a second sample is counted using a scintillation counter4 ,illustration3 ,time-lapse motion pictures of the liver of a #c-year-old girl were made with the scintillation camera #a hour after injection of #ej microcuries of iodine-#aca-labeled rose bengal dye4 ,this child was born without a bile-duct system and an artificial bile duct had been created surgically4 ,she developed symptoms that caused concern that the duct had closed4 ,these scans show the mass of material containing the radioactive material 7small light area7 moving downward and to the right1 indicating that the duct was still open4 ,for many years1 a dye known as rose bengal has been used in testing liver function4 ,about #aj years ago this procedure was improved by labeling the dye with ,i4 ,when this dye is injected into a vein it goes to the liver1 which removes it from the blood stream and transfers it to the intestines to be excreted4 ,the rate of disappearance of the dye from the blood stream is therefore a measure of the liver activity4 ,immediately after administration of the radioactive dye1 counts are recorded1 preferably continuously from several sites with shielded1 collimated detectors4 ,one counter is placed over the side of the head or the thigh to record the clearance of the dye from the blood stream4 ,a second is placed over the liver1 and a third over the abdomen to record the passage of the dye into the small intestine4 ,human serum albumin labeled with ,i is sometimes used for location of brain tumors4 ,it appears that tumors alter a normal 8barrier0 between the brain and blood in such a manner that the labeled albumin can penetrate tumorous tissues although it would be excluded from healthy brain tissue4 ,illustration3 ,showing3 #a ,human serum albumin labeled with ,i #b ,tumor selectively localizes labeled albumin #c ,survey of gamma radiation 7,standard points7 ,the brain behaves almost uniquely among body tissues in that a 8blood-brain barrier0 exists1 so that substances injected into the blood stream will not pass into brain cells although they will pass readily into muscular tissue4 ,this blood-brain barrier does not exist in brain tumors4 ,a systematic scanning of the skull then permits location of these cancerous 8hot spots04 ,iron-#ei ,iron is a necessary constituent of red blood cells1 so its radioactive form1 ,fe1 has been used frequently in measurement of the rate of formation of red cells1 the lifetime of red cells1 and red cell volumes4 ,the labeling is more difficult than labeling with chromium for the same purposes1 so this procedure no longer has the importance it once had4 ,on the other hand1 direct measurement of absorption of iron by the digestive tract can be accomplished only by using ,fe4 ,in achlorhydria the gastric juice in the stomach is deficient in hydrochloric acid1 and this condition has been shown to lower the iron absorption4 ,a normal diet contains much more iron than the body needs1 but in special cases1 sometimes called 8tired blood0 in advertising for medicines1 iron compounds are prescribed for the patient4 ,if ,fe is included1 its appearance in the blood stream can be monitored and the effectiveness of the medication noted4 ,illustration3 ,this multiple-port scintillation counter is used for iron-kinetic studies4 ,the tracer dose of iron-#ei is administered into the arm vein and then the activities in the bone marrow1 liver1 and spleen are recorded simultaneously with counters positioned over these areas1 and show distribution of iron-#ei as a function of time4 ,when the data are analyzed in conjunction with iron-#ei content in blood1 information can be obtained about sites of red blood cell production and destruction4 ,phosphorus-#cb ,the phosphate ion is a normal constituent of the blood4 ,in many kinds of tumors1 phosphates seem to be present in the cancerous tissue in a concentration several times that of the surrounding healthy tissue4 ,this offers a way of using phosphorus-#cb to distinguish between cancer cells and their neighbors4 ,due to the fact that ,p gives off beta rays but no gammas1 the counter must be placed very close to the suspected tissue1 since beta particles have very little penetrating power4 ,this fact limits the use of the test to skin cancers or to cancers exposed by surgery4 ,some kinds of brain tumors1 for instance1 are difficult to distinguish visually from the healthy brain tissue4 ,in such cases1 the patient may be given ,p labeled phosphate intravenously some hours before surgery4 ,a tiny beta-sensitive probe counter then can be moved about within the operative site to indicate to the surgeon the limits of the cancerous area4 ,sodium-#bd ,normal blood is about #a sodium chloride or ordinary salt4 ,this fact makes possible the use of ,na in some measurements of the blood and other fluids4 ,the figure illustrates this technique4 ,a sample of ,na,cl solution is injected into a vein in an arm or leg4 ,the time the radioisotope arrives at another part of the body is detected with a shielded radiation counter4 ,the elapsed time is a good indication of the presence or absence of constrictions or obstructions in the circulatory system4 ,illustration3 ,showing #a ,na,cl solution injected #b ,blood carries ,na,cl to both legs #c ,high reading--good circulation ,site of constriction #d ,low reading--poor circulation ,the passage of blood through the heart may also be measured with the aid of sodium-#bd4 ,since this isotope emits gamma rays1 measurement is done using counters on the outside of the body1 placed at appropriate locations above the different sections of the heart4 ,illustration3 ,showing3 #a ,na intravenously injected ,to lungs1 ,to body1 ,from arm1 ,from right lung1 ,from left lung #b ,geiger counter detects radiations from ,na #c ,ink writing recorder shows route of ,na ,technetium-#iim ,because of its short half-life of six hours1 technetium-#iim#aj is coming into use for diagnosis using scanning devices1 particularly for brain tumors4 ,it lasts such a short time it obviously cannot be kept in stock1 so it is prepared by the beta decay of molybdenum-#ii4aa ,a stock of molybdenum is kept in a shielded container in which it undergoes radioactive decay yielding technetium4 ,every morning1 as the technetium is needed1 it is extracted from its parent by a brine solution4 ,this general procedure of extracting a short-lived isotope from its parent is also used in other cases4 ,we shall see later that radon gas is obtained by an analogous method from its parent1 radium4 ,illustration3 ,using a 8nuclear cow0 to get technetium from its parent isotope4 ,the 8cow0 is being fed saltwater through a tube4 ,the saltwater drains through a high-radiation 7hot7 isotope4 ,the resultant drip-off is a daughter such as technetium-#iim4 ,this new1 mild isotope can be mixed with other elements and these become the day's supply of radioisotopes for other scans4 ,technetium-#iim decays in #f hours4 ,thus greater amounts1 with less possibility of injury1 can be administered and a better picture results4 ,thulium-#agj and ,gamma ,radiography ,for years it has been recognized that there would be many uses for a truly portable device for taking ,x-ray pictures--one that could be carried by the doctor to the bedside or to the scene of an accident4 ,conventional ,x-ray equipment has been in use by doctors for many years1 and highly efficient apparatus has become indispensable1 especially in treating bone conditions4 ,there is1 however1 a need for a means of examining patients who cannot be moved to a hospital ,x-ray room1 and are located where electric current sources are not available4 ,a few years ago1 a unit was devised that weighed only a few pounds1 and could take 8,x-ray pictures0 7actually gamma radiographs7 using the gamma rays from the radioisotope thulium-#agj4 ,the thulium source is kept inside a lead shield1 but a photographic shutter-release cable can be pressed to move it momentarily over an open port in the shielding4 ,the picture is taken with an exposure of a few seconds4 ,a somewhat similar device uses strontium-#ij as the source of beta radiation that in turn stimulates the emission of gamma rays from a target within the instrument4 ,illustration3 ,a technician holds an inexpensive portable ,x-ray unit that was developed by the ,argonne ,national ,laboratory4 ,compare its size with the standard ,x-ray machine shown at left and above4 ,still more recently1 ,i has been used very successfully in a portable device as a low-energy gamma source for radiography4 ,the gamma rays from this source are sufficiently penetrating for photographing the arms and legs1 and the necessary shielding is easily supplied to protect the operator4 ,by contrast with larger devices1 the gamma-ray source can be as small as one-tenth millimeter in diameter1 virtually a point source2 this makes possible maximum sharpness of image4 ,the latest device1 using up to one curie#ab of ,i1 weighs #b pounds1 yet has adequate shielding for the operator4 ,it is truly portable4 ,if this ,x-ray source is combined with a rapid developing photographic film1 a physician can be completely freed from dependence upon the hospital laboratory for emergency ,x rays4 ,a finished print can be ready for inspection in #aj seconds4 ,the doctor thus can decide quickly whether it is safe to move an accident victim1 for instance4 ,in military operations1 similarly1 it becomes a simple matter to examine wounded soldiers in the field where conventional equipment is not available4 ,tritium ,more than #cj years ago1 when deuterium 7heavy hydrogen7 was first discovered1 heavy water 7,d,o7 was used for the determination of total body water4 ,a small sample of heavy water was given either intravenously or orally1 and time was allowed for it to mix uniformly with all the water in the body 7about #d to #f hours74 ,a sample was then obtained of the mixed water and analyzed for its heavy water content4 ,this procedure was useful but it was hard to make an accurate analysis of low concentrations of heavy water4 ,more recently1 however1 tritium 7,h7 7radioactive hydrogen7 has been produced in abundance4 ,its oxide1 tritiated water 7,h,o71 is chemically almost the same as ordinary water1 but physically it may be distinguished by the beta rays given off by the tritium4 ,this very soft 7low-energy7 beta ray requires the use of special counting equipment1 either a windowless flow-gas counter or a liquid scintillator1 but with the proper techniques accurate measurement is possible4 ,the total body water can then be computed by the general isotope dilution formula used for measuring blood plasma volume4 ,illustration3 ,the total body water is determined by the dilution method using tritiated water4 ,this technician is purifying a urine sample so that the tritium content can be determined and the total body water calculated4 ,activation ,analysis ,another booklet in this series1 ,neutron ,activation ,analysis1 discusses a new process by which microscopic quantities of many different materials may be analyzed accurately4 ,neutron irradiation of these samples changes some of their atoms to radioactive isotopes4 ,a multichannel analyzer instrument gives a record of the concentration of any of about #ej of the known elements4 ,one use of this technique involved the analysis of a hair from ,napoleon's head4 ,more than #ajj years after his death it was shown that the ,french ,emperor had been given arsenic in large quantities and that this possibly caused his death4 ,the ways in which activation analysis can be applied to medical diagnosis are at present largely limited to toxicology1 the study of poisons1 but the future may bring new possibilities4 ,knowledge is still being sought1 for example1 about the physiological role played by minute quantities of some of the elements found in the body4 ,the ability to determine accurately a few parts per million of 8trace elements0 in the various tissues and body fluids is expected to provide much useful information as to the functions of these materials4 ,summary ,a large number of different radioisotopes have been used for measurement of disease conditions in the human body4 ,they may measure liquid volumes1 rates of flow or rates of transfer through organs or membranes2 they may show the behavior of internal organs2 they may differentiate between normal and malignant tissues4 ,hundreds of hospitals are now making thousands of these tests annually4 ,this does not mean that all the diagnostic problems have been solved4 ,much of the work is on an experimental rather than a routine basis4 ,improvements in techniques are still being made4 ,as quantities of radioisotopes available for these purposes grow1 and as the cost continues to drop1 it is expected there will be still more applications4 ,finally1 this does not mean we no longer need the doctor's diagnostic skill4 ,all radioisotope procedures are merely tools to aid the skilled physician4 ,as the practice of medicine has changed from an art to a science1 radioisotopes have played a useful part4 ,,therapy ,a ,successful ,case ,a doctor recently told this story about a cancer patient who was cured by irradiation with cobalt-#fj4 8,a #ge-year-old white male patient1 who had been hoarse for one month1 was treated unsuccessfully with the usual medications given for a bad cold4 ,finally1 examination of his larynx revealed an ulcerated swelling on the right vocal cord4 ,a biopsy 7microscopic examination of a tissue sample7 was made1 and it was found the swelling was a squamous-cell cancer4 8,daily radiation treatment using a cobalt-#fj device was started and continued for #ca days4 ,this was in ,september #aiei4 ,the cobalt-#fj unit is one that can be operated by remote control4 ,it positions radioactive cobalt over a collimator1 which determines the size of the radiation beam reaching the patient4 ,the machine may be made to rotate around the patient or can be used at any desired angle or position4 ,illustration3 ,showing3 ,co source ,tungsten alloy shielding ,shutter ,counterweight and personnel shield 8,when the treatment series was in progress1 the patient's voice was temporarily made worse1 but it returned to normal within two months after the treatment ended4 ,the radiation destroyed the cancerous growth1 and frequent examinations over #f years since have failed to reveal any regrowth4 8,the treatment spared the patient's vocal cords1 and his voice1 airway1 and food passage were preserved40 ,this dramatic tale with a happy ending is a good one with which to start a discussion of how doctors use radioisotopes for treatment of disease4 ,general ,principles ,radioisotopes have an important role in the treatment of disease1 particularly cancer4 ,it is still believed that cancer is not one but several diseases with possible multiple causes4 ,great progress is being made in development of chemicals for relief of cancer4 ,nevertheless1 radiation and surgery are still the main methods for treating cancer1 and there are many conditions in which relief can be obtained through use of radiation4 ,moreover1 the imaginative use of radioisotopes gives much greater flexibility in radiation therapy4 ,this is expected to be true for some years to come even as progress continues4 ,radioisotopes serve as concentrated sources of radiation and frequently are localized within the diseased cells or organs4 ,the dose can be computed to yield the maximum therapeutic effect without harming adjacent healthy tissues4 ,let us see some of the ways in which this is done4 ,iodine-#aca and ,iodine-#acb ,iodine1 as was mentioned earlier1 concentrates in the thyroid gland1 and is converted there to protein-bound iodine that is slowly released to the blood stream4 ,iodine-#aca1 in concentrations much higher than those used in diagnostic tests1 will irradiate thyroid cells1 thereby damage them1 and reduce the activity of an overactive thyroid 7hyperthyroidism74 ,the energy is released within the affected gland1 and much of it is absorbed there4 ,iodine-#aca has a half-life of #h4a days4 ,in contrast1 ,i has a half-life of only #b4cc hours4 ,what this means is that the same weight of radioactive ,i will give a greater radiation dose than ,i would1 and lose its activity rapidly enough to present much less hazard by the time the iodine is released to the blood stream4 ,iodine-#acb is therefore often preferred for treatment of this sort4 ,boron-#aj ,boron-#aj has been used experimentally in the treatment of inoperable brain tumors4 ,glioblastoma multiforme1 a particularly malignant form of cancer1 is an invariably fatal disease in which the patient has a probable life expectancy of only #a year4 ,the tumor extends roots into normal tissues to such an extent that it is virtually impossible for the surgeon to remove all malignant tissue even if he removes enough normal brain to affect the functioning of the patient seriously4 ,with or without operation the patient dies within months4 ,this is therefore a case in which any improvement at all is significantly helpful4 ,the blood-brain barrier that was mentioned earlier minimizes the passages of many materials into normal brain tissues4 ,but when some organic or inorganic compounds1 such as the boron compounds1 are injected into the blood stream1 they will pass readily into brain tumors and not move into normal brain cells4 ,boron-#aj absorbs slow neutrons readily1 and becomes boron-#aa1 which disintegrates almost immediately into alpha particles and a lithium isotope4 ,alpha particles1 remember1 have very little penetrating power1 so all the energy of the alpha radioactivity is expended within the individual tumor cells4 ,this is an ideal situation1 for it makes possible destruction of tumor cells with virtually no harm to normal cells1 even when the two kinds are closely intermingled4 ,slow neutrons pass through the human body with very little damage1 so a fairly strong dose of them can be safely applied to the head4 ,many of them will be absorbed by the boron-#aj1 and maximum destruction of the cancer will occur1 along with minimum hazard to the patient4 ,this treatment is accomplished by placing the head of the patient in a beam of slow neutrons emerging from a nuclear reactor a few minutes after the boron-#aj compound has been injected into a vein4 ,illustration3 ,,sequence ,,of ,,events ,,in ,,neutron ,,capture ,,therapy ,,using ,,boron-#aj ,neutron capture treatment of a brain tumor1 using the ,brookhaven ,national ,laboratory research reactor 7center74 ,control console ,treatment port 7shutter shown open7 ,observation window ,patient treatment room ,shutter elevator 7hydraulic7 ,control rod drives ,heavy concrete shield ,control rods ,experimental holes ,reactor core ,cooling air ,cooling water ,illustration3 7#a7 ,a lead shutter shields the patient from reactor neutrons4 ,illustration3 7#b7 ,a compound containing the stable element boron is injected into the bloodstream2 the tumor absorbs most of the boron4 ,illustration3 7#c7 ,after #h minutes1 when the tumor is saturated1 the shutter is removed and neutrons bombard the brain1 splitting boron atoms so that fragments destroy tumor tissue4 ,illustration3 7#d7 ,twenty minutes later the shutter is closed and the treatment ends4 ,the difficulty is that most boron compounds themselves are poisonous to human tissues1 and only small concentrations can be tolerated in the blood4 ,efforts have been made1 with some success1 to synthesize new boron compounds that have the greatest possible degree of selective absorption by the tumors4 ,both organic and inorganic compounds have been tried1 and the degree of selectivity has been shown to be much greater for some than for others4 ,so far it is too early to say that any cures have been brought about1 but results have been very encouraging4 ,the ideal drug1 one which will make possible complete destruction of the cancer without harming the patient1 is probably still to be devised4 ,phosphorus-#cb ,another disease which is peculiarly open to attack by radioisotopes is polycythemia vera4 ,this is an insidious ailment of a chronic1 slowly progressive nature1 characterized by an abnormal increase in the number of red blood cells1 an increase in total blood volume1 enlargement of the spleen1 and a tendency for bleeding to occur4 ,there is some indication that it may be related to leukemia4 ,until recent years there was no very satisfactory treatment of this malady4 ,the ancient practice of bleeding was as useful as anything1 giving temporary relief but not striking at the underlying cause4 ,there is still no true cure1 but the use of phosphorus-#cb has been very effective in causing disappearance of symptoms for periods from months to years1 lengthening the patient's life considerably4 ,the purpose of the ,p treatment 7using a sodium-radiophosphate solution7 is not to destroy the excess of red cells1 as had been tried with some drugs1 but rather to slow down their formation and thereby get at the basic cause4 ,phosphorus-#cb emits pure beta rays having an average path in tissue only #b millimeters long4 ,its half-life is #ad4c days4 ,when it is given intravenously it mixes rapidly with the circulating blood and slowly accumulates in tissues that utilize phosphates in their metabolism4 ,this brings appreciable concentration in the blood-forming tissues 7about twice as much in blood cells as in general body cells74 ,illustration3 ,showing3 #a ,patient drinks ,p in water solution #b ,p selectively absorbed ,blood cell production in bone marrow ,illustration3 ,survival of polycythemia vera patients after ,p therapy4 ,no4 cases #bja ,average age #eb ,median survival #ac4b ,survival for #e years #ia4e #aj years #gj4j ,one other pertinent fact is that these rapidly dividing hematopoietic cells are extremely sensitive to radiation4 7,hematopoietic cells are those that are actively forming blood cells and are therefore those that should be attacked selectively47 ,the dose required is of course many times that needed for diagnostic studies1 and careful observation of the results is necessary to determine that exactly the desired effect has been obtained4 ,there exists some controversy over this course of treatment4 ,no one denies that the lives of patients have been lengthened notably4 ,nevertheless since the purpose of the procedure is to reduce red cell formation1 there exists the hazard of too great a reduction1 and the possibility of causing leukemia 7a disease of too few red cells74 ,there may be a small increase in the number of cases of leukemia among those treated with ,p compared with the general population4 ,the controversy arises over whether the ,p treatment caused the leukemia1 or whether it merely prolonged the lives of the patients until leukemia appeared as it would have in these persons even without treatment4 ,this is probably quibbling1 and many doctors believe that the slight unproven risk is worth taking to produce the admitted lengthy freedom from symptoms4 ,gold-#aih ,the last ailment we shall discuss in this section is the accumulation of large quantities of excess fluid in the chest and abdominal cavities from their linings1 as a consequence of the growth of certain types of malignant tumors4 ,frequent surgical drainage was at one time the only very useful treatment1 and of course this was both uncomfortable and dangerous4 ,the use of radioactive colloidal suspensions1 primarily colloidal gold-#aih1 has been quite successful in palliative treatment3 ,it does not cure1 but it does give marked relief4 ,illustration3 ,showing3 ,colloidal gold in shield ,saline solution ,to peritoneal or pleural cavity ,radioactive colloids 7a colloid is a suspension of one very finely divided substance in some other medium7 can be introduced into the abdominal cavity1 where they may remain suspended or settle out upon the lining4 ,in either case1 since they are not dissolved1 they do not pass through the membranes or cell walls but remain within the cavity4 ,through its destructive and retarding effect on the cancer cells the radiation inhibits the oozing of fluids4 ,gold-#aih offers several advantages in such cases4 ,it has a short half-life 7#b4g days72 it is chemically inert and therefore nontoxic2 and it emits beta and gamma radiation that is almost entirely absorbed by the tissues in its immediate neighborhood4 ,the results have been very encouraging4 ,there is admittedly no evidence of any cures1 or even lengthening of life1 but there has been marked reduction of discomfort and control of the oozing in over two-thirds of the cases treated4 ,beads1 ,needles1 and ,applicators ,radium salts were the first materials to be used for radiation treatment of cancer4 ,being both very expensive and very long-lived1 they could not be injected but were used in temporary implants4 ,radium salts in powder form were packed into tiny hollow needles about #a centimeter long1 which were then sealed tightly to prevent the escape of radon gas4 ,as radium decays 7half-life #afbj years7 it becomes gaseous radon4 ,the latter is also radioactive1 so it must be prevented from escaping4 ,these gold needles could be inserted into tumors and left there until the desired dosage had been administered4 ,one difficulty in radium treatment was that the needles were so tiny that on numerous occasions they were lost1 having been thrown out with the dressings4 ,then1 both because of their value and their hazard1 a frantic search ensued when this happened1 not always ending successfully4 ,illustration3 ,the needle used for implantation of yttrium-#ij pellets into the pituitary gland is shown in the top photograph4 ,in the center ,x ray the needle is in place and the pellets have just been passed through it into the bone area surrounding the pituitary gland4 ,the bottom ,x ray shows the needle withdrawn and the pellets within the bone4 ,the fact that radon1 the daughter of radium1 is constantly produced from its parent1 helped to eliminate some of this difficulty4 ,radium could be kept in solution1 decaying constantly to yield radon4 ,the latter1 with a half-life of #d days1 could be sealed into gold seeds #c by #j4e millimeters and left in the patient without much risk1 even if he failed to return for its removal at exactly the appointed time4 ,the cost was low even if the seeds were lost4 ,during the last #bj years1 other highly radioactive sources have been developed that have been used successfully4 ,cobalt-#fj is one popular material4 ,cobalt-#ei can be neutron-irradiated in a reactor to yield cobalt-#fj with such a high specific activity that a small cylinder of it is more radioactive than the entire world's supply of radium4 ,cobalt-#fj has been encapsulated in gold or silver needles1 sometimes of special shapes for adaptation to specific tumors such as carcinoma of the cervix4 ,sometimes needles have been spaced at intervals on plastic ribbon that adapts itself readily to the shape of the organ treated4 ,gold-#aih is also an interesting isotope4 ,since it is chemically inert in the body1 it needs no protective coating1 and as is the case with radon1 its short half-life makes its use simpler in that the time of removal is not of critical importance4 ,ceramic beads made of yttrium-#ij oxide are a moderately new development4 ,one very successful application of this material has been for the destruction of the pituitary gland4 ,cancer may be described as the runaway growth of cells4 ,the secretions of the pituitary gland serve to stimulate cell reproduction1 so it was reasoned that destruction of this gland might well slow down growth of a tumor elsewhere in the body4 ,the trouble was that the pituitary is small and located at the base of the brain4 ,surgical removal had brought dramatic relief 7not cure7 to many patients1 but the surgery itself was difficult and hazardous4 ,tiny yttrium-#ij oxide beads1 glasslike in nature1 can be implanted directly in the gland with much less difficulty and risk1 and do the work of destroying the gland with little damage to its surroundings4 ,the key to the success of yttrium-#ij is the fact that it is a beta-emitter1 and beta rays have so little penetrating power that their effect is limited to the immediate area of the implant4 ,teletherapy ,over #bjj teletherapy units are now in use in the ,united ,states for treatment of patients by using very high intensity sources of cobalt-#fj 7usually7 or cesium-#acg4 ,units carrying sources with intensities of more than a thousand curies are common4 ,illustration3 ,the cobalt-#fj unit at the ,m4 ,d4 ,anderson ,hospital and ,tumor ,institute in ,houston1 ,texas1 employs a #cjjj-;curie source4 ,this unit has a mechanism that allows for rotation therapy about a stationary patient4 ,many different treatment positions are possible4 ,this patient1 shown in position for therapy1 has above her chest an auxiliary diaphragm that consists of an expanded metal tray on which blocks of either tungsten or lead are placed to absorb gamma rays and thus shape the field of treatment4 ,in this case they allow for irradiation of the portions of the neck and chest delineated by the lines visible on the patient4 ,since a curie is the amount of radioactivity in a gram of radium that is in equilibrium with its decay products1 a #ajjj-;curie source is comparable to #b pounds of pure radium4 ,neglecting for the moment the scarcity and enormous cost of that much radium 7millions of dollars71 we have to consider that it would be large in volume and consequently difficult to apply4 ,radiation from such a quantity cannot be focussed2 consequently1 either much of it will fall upon healthy tissue surrounding the cancer or much of it will be wasted if a narrow passage through the shield is aimed at the tumor4 ,in contrast1 a tiny cobalt source provides just as much radiation and more if it can be brought to bear upon the exact spot to be treated4 ,illustration3 ,diagram of teletherapy unit ,most interesting of all is the principle by which internal cancers can be treated with a minimum of damage to the skin4 ,deep x-irradiation has always been the approved treatment for deep-lying cancers1 but until recently this required very cumbersome units4 ,with the modern rotational device shown in the diagram1 a very narrow beam is aimed at the patient while the source is mounted upon a carrier that revolves completely around him4 ,the patient is positioned carefully so that the lesion to be treated is exactly at the center of the circular path of the carrier4 ,the result is that the beam strikes its internal target during the entire circular orbit1 but the same amount of radiation is spread out over a belt of skin and tissue all the way around the patient4 ,the damage to any one skin cell is minimized4 ,the advantage of this device over an earlier device1 in which the patient was revolved in a stationary beam1 is that the mechanical equipment is much simpler4 ,,conclusions ,in summary1 then1 we may say that radioisotopes play an important role in medicine4 ,for the diagnostician1 small harmless quantities of many isotopes serve as tools to aid him in gaining information about normal and abnormal life processes4 ,the usefulness of this information depends upon his ingenuity in devising questions to be answered1 apparatus to measure the results1 and explanations for the results4 ,for therapeutic uses1 on the other hand1 the important thing to remember is that radiation damages many kinds of cells1 especially while they are in the process of division 7reproduction74#ac ,cancer cells are self-reproducing cells1 but do so in an uncontrolled manner4 ,hence cancer cells are particularly vulnerable to radiation4 ,this treatment requires potent sources and correspondingly increases the hazards of use4 ,in all cases1 the use of these potentially hazardous materials belongs under the supervision of the ,u4 ,s4 ,atomic ,energy ,commission4#ad ,licenses are issued by the ,commission after investigation of the training1 ability1 and facilities possessed by prospective users of dangerous quantities4 ,at regular intervals courses are given to train individuals in the techniques necessary for safe handling1 and graduates of these courses are now located in laboratories all over the country4 ,the future of this field cannot be predicted with certainty4 ,research in hundreds of laboratories is continuing to add to our knowledge1 through new apparatus1 new techniques1 and new experiments4 ,necessarily the number of totally new fields is becoming smaller1 but most certainly the number of cases using procedures already established is bound to increase4 ,we foresee steady improvement and growth in all uses of radioisotopes in medicine4 ,,appendix ,measuring ,instruments#ae ,the measurement of radioactivity must be accomplished indirectly1 so use is made of the physical1 chemical1 and electrical effects of radiation on materials4 ,one commonly used effect is that of ionization4 ,alpha and beta particles ionize gases through which they pass1 thereby making the gases electrically conductive4 ,a family of counters uses this principle3 the ionization chamber1 the proportional counter1 and the ,geiger-,mller counter4 ,certain crystals1 sodium iodide being an excellent example1 emit flashes of visible light when struck by ionizing radiation4 ,these crystals are used in scintillation counters4 ,ionization ,chambers ,one of a pair of electrodes is a wire located centrally within a cylinder4 ,the other electrode is the wall of the chamber4 ,radiation ionizes the gas within the chamber1 permitting the passage of current between the electrodes4 ,the thickness of a window in the chamber wall determines the type of radiation it can measure4 ,only gamma rays will pass through a heavy metal wall1 glass windows will admit all gammas and most betas1 and plastic 7,mylar7 windows are necessary to admit alpha particles4 ,counters of this type1 when properly calibrated1 will measure the total amount of radiation received by the body of the wearer4 ,proportional ,counters ,this is a type of ionization chamber in which the intensity of the electrical pulse it produces is proportional to the energy of the incoming particle4 ,this makes it possible to record alpha particles and discriminate against gamma rays4 ,geiger-,mller ,counters ,these have been widely used and are versatile in their applications4 ,the potential difference between the electrodes in the ,geiger-,mller tube 7similar to an ionization chamber7 is high4 ,a single alpha or beta particle ionizes some of the gas within the chamber4 ,in turn these ions strike other gas molecules producing secondary ionization4 ,the result is an 8avalanche0 or high-intensity pulse of electricity passing between the electrodes4 ,these pulses can be counted electrically and recorded on a meter at rates up to several thousand per minute4 ,scintillation ,counters ,since the development of the photoelectric tube and the photomultiplier tube 7a combination of photoelectric cell and amplifier71 the scintillation counter has become the most popular instrument for most purposes described in this booklet4 ,the flash of light produced when an individual ionizing particle or ray strikes a sodium-iodide crystal is noted by a photoelectric cell4 ,the intensity of the flash is a measure of the energy of the radiation1 so the voltage of the output of the photomultiplier tube is a measure of the wavelength of the original gamma ray4 ,the scintillation counter can observe up to a million counts per minute and discriminate sharply between gamma rays of different energies4 ,with proper windows it can be used for alpha or beta counts as well4 ,solid ,state ,counters ,the latest development is a tiny silicon 7transistor-type7 diode detector that can be made as small as a grain of sand and placed within the body with very little discomfort4 ,scanners ,many of the applications described in this booklet require accurate knowledge of the exact location of the radioactive source within the body4 ,commonly a detecting tube is used having a collimating shield so that it accepts only that radiation that strikes it head-on4 ,a motor-driven carrier moves the counter linearly at a slow rate4 ,radiation is counted and whenever the count reaches the predetermined amount--from one count to many--an electric impulse causes a synchronously moving pen to make a dot on a chart4 ,the scanner1 upon reaching the end of a line moves down to the next line and starts over1 eventually producing a complete record of the radiation sources it has passed over4 ,,suggested ,,references ,technical ,books ,radioactive ,isotopes in ,medicine and ,biology1 ,solomon ,silver1 ,lea ,febiger1 ,philadelphia1 ,pennsylvania #aiajf1 #aifb1 #cdg pp41 #h4jj4 ,atomic ,medicine1 ,charles ,f4 ,behrens and ,e4 ,richard ,king 7,eds471 ,the ,williams ,wilkins ,company1 ,baltimore1 ,maryland #babjb1 #aifd1 #gff pp41 #ah4jj4 ,the ,practice of ,nuclear ,medicine1 ,william ,h4 ,blahd1 ,franz ,k4 ,bauer1 and ,benedict ,cassen1 ,charles ,c4 ,thomas1 ,publisher1 ,springfield1 ,illinois #fbgjc1 #aieh1 #dcb pp41 #ab4ej4 ,progress in ,atomic ,medicine1 ,john ,h4 ,lawrence 7,ed471 ,grune ,stratton1 ,inc41 ,new ,york #ajjaf1 #aife1 volume #a1 #bdj pp41 #i4ge4 ,radiation ,biology and ,medicine1 ,walter ,d4 ,claus 7,ed471 ,addison-,wesley ,publishing ,company1 ,reading1 ,massachusetts #jahfg1 #aieh1 #idd pp41 #ag4ej4 ,part #g1 ,medical ,uses of ,atomic ,radiation1 pp4 #dga-ehi4 ,radioisotopes and ,radiation1 ,john ,h4 ,lawrence1 ,bernard ,manowitz1 and ,benjamin ,s4 ,loeb1 ,mc,graw-,hill ,book ,company1 ,new ,york #ajjcf1 #aifd1 #aca pp41 #ah4jj4 ,chapter #a1 ,medical ,diagnosis and ,research1 pp4 #e-de2 ,chapter #b1 ,medical ,therapy1 pp4 #di-fb4 ,popular ,books ,atoms ,today and ,tomorrow 7revised edition71 ,margaret ,o4 ,hyde1 ,mc,graw-,hill ,book ,company1 ,inc41 ,new ,york #ajjcf1 #aiff1 #afj pp41 #c4be4 ,chapter #i1 ,the ,doctor and the ,atom1 pp4 #gi-aja4 ,atomic ,energy in ,medicine1 ,k4 ,e4 ,halnan1 ,philosophical ,library1 ,inc41 ,new ,york #ajjaf1 #aieh1 #aeg pp41 #f4jj4 7,out of print but available through libraries47 ,teach ,yourself ,atomic ,physics1 ,james ,m4 ,valentine1 ,the ,macmillan ,company1 ,new ,york #ajjaa1 #aifa1 #aib pp41 #a4ie4 7,out of print but available through libraries47 ,chapter ,x1 ,medical and ,biological ,uses of ,radioactive ,isotopes1 pp4 #agc-ahd4 ,atoms for ,peace1 ,david ,o4 ,woodbury1 ,dodd1 ,mead ,company1 ,new ,york #ajjaf1 #aife1 #bei pp41 #d4ej4 ,pp4 #agd-aia4 ,the ,atom at ,work1 ,jacob ,sacks1 ,the ,ronald ,press ,company1 ,new ,york #ajjaj1 #aief1 #cda pp41 #e4ej4 ,chapter #ac1 ,radioactive ,isotopes in ,hospital and ,clinic1 pp4 #bdd-bfd4 ,articles ,ionizing ,radiation and ,medicine1 ,s4 ,warren1 ,scientific ,american1 #bja3 #afd 7,september #aiei74 ,nuclear ,nurses ,learn to ,tame the ,atom1 ,w4 ,mc,gaffin1 ,today's ,health1 #cg3 #fb 7,december #aiei74 ,how ,isotopes ,aid ,medicine in ,tracking ,down ,your ,ailments1 ,j4 ,foster1 ,today's ,health1 #db3 #dj 7,may #aifd74 ,nuclear ,energy as a ,medical ,tool1 ,g4 ,w4 ,tressel1 ,today's ,health1 #dc3 #ej 7,may #aife74 ,reports ,radioisotopes in ,medicine 7,,sria-#ac71 ,stanford ,research ,institute1 ,clearinghouse for ,federal ,scientific and ,technical ,information1 #ebhe ,port ,royal ,road1 ,springfield1 ,virginia #bbaea1 #aiei1 #ahj pp41 #c4jj4 ,the following reports are available from the ,superintendent of ,documents1 ,u4 ,s4 ,government ,printing ,office1 ,washington1 ,d4 ,c4 #bjdjb4 ,isotopes and ,radiation ,technology 7,fall #aifc71 ,p4 ,s4 ,baker1 ,a4 ,f4 ,rupp1 and ,associates1 ,oak ,ridge ,national ,laboratory1 ,u4 ,s4 ,atomic ,energy ,commission1 #abc pp41 #j4gj4 ,radioisotopes in ,medicine 7,,oro-#abe71 ,gould ,a4 ,andrews1 ,marshall ,brucer1 and ,elizabeth ,b4 ,anderson1 #aief1 #hag pp41 #f4jj4 ,applications of ,radioisotopes and ,radiation in the ,life ,sciences1 ,hearings before the ,subcommittee on ,research1 ,development1 and ,radiation of the ,joint ,committee on ,atomic ,energy1 #hgth ,congress1 #ast ,session1 #aifa1 #eac pp41 #a4ej2 ,summary ,analysis of the ,hearings1 #bc pp41 #j4ae4 ,motion ,pictures ,available for loan without charge from the ,,aec ,headquarters ,film ,library1 ,division of ,public ,information1 ,u4 ,s4 ,atomic ,energy ,commission1 ,washington1 ,d4 ,c4 #bjede and from other ,,aec film libraries4 ,radioisotope ,applications in ,medicine1 #bf minutes1 black and white1 sound1 #aifd4 ,produced by the ,educational ,broadcasting ,corporation under the joint direction of the ,u4 ,s4 ,atomic ,energy ,commission's ,divisions of ,isotopes ,development and ,nuclear ,education and ,training1 and the ,oak ,ridge ,institute of ,nuclear ,studies4 ,this film traces the development of the use of radioisotopes and radiation in the field of medicine from the early work of ,hevesy to the present4 ,descriptions of the following are given3 study of cholesterol and arteriosclerosis2 cobalt labeled vitamin ,b used to study pernicious anemia2 history of iodine radioisotopes and the thyroid2 brain tumor localization2 determination of body fluid volumes2 red cell lifetime2 and use of radioisotopes for the treatment of various diseases4 ,medicine1 #bj minutes1 sound1 color1 #aieg4 ,produced by the ,u4 ,s4 ,information ,agency4 ,four illustrations of the use of radioactive materials in diagnosis and therapy are given3 exact preoperative location of brain tumor2 scanning and charting of thyroids2 cancer therapy research2 and the study of blood diseases and hardening of the arteries4 ,radiation ,protection in ,nuclear ,medicine1 #de minutes1 sound1 color1 #aifb4 ,produced by the ,fordel ,films for the ,bureau of ,medicine and ,surgery of the ,u4 ,s4 ,navy4 ,this semitechnical film demonstrates the procedures devised for naval hospitals to protect against the gamma radiation emitted from materials used in radiation therapy4 ,the following films in the ,magic of the ,atom ,series were produced by the ,handel ,film ,corporation4 ,they are each #ab minutes long1 have sound1 and are in black and white4 ,the ,atom and the ,doctor 7#aied7 shows three applications of radioisotopes in medicine3 testing for leukemia and other blood disorders with radioiron2 diagnosis of thyroid conditions with radioiodine2 and cancer research and therapy with radiogallium4 ,the ,atom in the ,hospital 7#aifa7 7available in color and black and white7 illustrates the following facilities at the ,city of ,hope ,medical ,center in ,los ,angeles3 the stationary cobalt source that is used to treat various forms of malignancies2 a rotational therapy unit called the 8cesium ring01 which revolves around the patient and focuses its beam on the diseased area2 and the total-body irradiation chamber for studying the effects of radiation on living things4 ,research with these facilities is explained4 ,atomic ,biology for ,medicine 7#aief7 explains experiments performed to discover effects of radiation on mammals4 ,atoms for ,health 7#aief7 outlines two methods of diagnosis and treatment possible with radiation3 a diagnostic test of the liver1 and cancer therapy with a radioactive cobalt device4 ,case histories are presented step-by-step4 ,radiation3 ,silent ,servant of ,mankind 7#aief7 depicts four uses of controlled radiation that can benefit mankind3 bombardment of plants from a radioactive cobalt source to induce genetic changes for study and crop improvement2 irradiation of deep-seated tumors with a beam from a particle accelerator2 therapy of thyroid cancer with radioactive iodine2 and possibilities for treating brain tumors4 ,,photo ,,credits ,cover ,courtesy ,brookhaven ,national ,laboratory ,page #a ,general ,electric ,company #b1 #c1 #d ,discovery of the ,elements4 ,mary ,elvira ,weeks1 ,journal of ,chemical ,education #f ,nobel ,institute #ab ,chicago ,wesley ,memorial ,hospital 7main photo7 #ac ,lawrence ,radiation ,laboratory 7,,lrl7 #ad ,brookhaven ,national ,laboratory #ag ,,lrl #ba ,,lrl #bb ,los ,alamos ,scientific ,laboratory #bd ,,lrl #bh ,argonne ,national ,laboratory #ci ,paul ,v4 ,harper1 ,m4 ,d4 #da ,university of ,texas1 ,m4 ,d4 ,anderson ,hospital and ,tumor ,institute ,this booklet is one of the 8,understanding the ,atom0 ,series4 ,comments are invited on this booklet and others in the series2 please send them to the ,division of ,technical ,information1 ,u4 ,s4 ,atomic ,energy ,commission1 ,washington1 ,d4 ,c4 #bjede4 ,published as part of the ,,aec's educational assistance program1 the series includes these titles3 ,accelerators ,animals in ,atomic ,research ,atomic ,fuel ,atomic ,power ,safety ,atoms at the ,science ,fair ,atoms in ,agriculture ,atoms1 ,nature1 and ,man ,books on ,atomic ,energy for ,adults and ,children ,careers in ,atomic ,energy ,computers ,controlled ,nuclear ,fusion ,cryogenics1 ,the ,uncommon ,cold ,direct ,conversion of ,energy ,fallout ,from ,nuclear ,tests ,food ,preservation by ,irradiation ,genetic ,effects of ,radiation ,index to the ,,uas ,series ,lasers ,microstructure of ,matter ,neutron ,activation ,analysis ,nondestructive ,testing ,nuclear ,clocks ,nuclear ,energy for ,desalting ,nuclear ,power and ,merchant ,shipping ,nuclear ,power ,plants ,nuclear ,propulsion for ,space ,nuclear ,reactors ,nuclear ,terms1 ,a ,brief ,glossary ,our ,atomic ,world ,plowshare ,plutonium ,power from ,radioisotopes ,power ,reactors in ,small ,packages ,radioactive ,wastes ,radioisotopes and ,life ,processes ,radioisotopes in ,industry ,radioisotopes in ,medicine ,,snap1 ,nuclear ,space ,reactors ,sources of ,nuclear ,fuel ,space ,radiation ,spectroscopy ,synthetic ,transuranium ,elements ,the ,atom and the ,ocean ,the ,chemistry of the ,noble ,gases ,the ,elusive ,neutrino ,the ,first ,reactor ,the ,natural ,radiation ,environment ,whole ,body ,counters ,your ,body and ,radiation ,a single copy of any one booklet1 or of no more than three different booklets1 may be obtained free by writing to3 ,,usaec1 ,p4 ,o4 ,,box #fb1 ,,oak ,,ridge1 ,,tennessee #cghcj ,complete sets of the series are available to school and public librarians1 and to teachers who can make them available for reference or for use by groups4 ,requests should be made on school or library letterheads and indicate the proposed use4 ,students and teachers who need other material on specific aspects of nuclear science1 or references to other reading material1 may also write to the ,oak ,ridge address4 ,requests should state the topic of interest exactly1 and the use intended4 ,in all requests1 include 8,zip ,code0 in return address4 ,printed in the ,united ,states of ,america ,,usaec ,division of ,technical ,information ,extension1 ,oak ,ridge1 ,tennessee ,,footnotes #a,the early dangers from use of ,x rays1 due to incomplete understanding and inadequate shielding1 have now been eliminated4 #b;,gamma rays are high-energy electromagnetic radiation4 #c;,alpha particles are large positively charged particles1 identical to helium nuclei4 ,for definitions of unfamiliar words see ,nuclear ,terms1 ,a ,brief ,glossary1 a companion booklet in this series4 #d;,for detailed descriptions of these waves and particles1 see ,our ,atomic ,world1 a companion booklet in this series4 #e;,an equivalent statement is that nuclei of isotopes have the same number of protons but different numbers of neutrons4 #f,see ,appendix for a description of types of radiation-detection instruments4 #g,see ,radioisotopes and ,life ,processes1 another booklet in this series1 for a discussion of one area of biomedical research4 #h;,a positron is an 8antielectron04 ,it has the mass of an electron but a positive charge4 #i;,a collimator is a focusing device consisting of a series of slits between blocks of shielding material4 ,consult the ,appendix for descriptions of other instruments mentioned here4 #aj,the superscript m after this isotope indicates an excited state of the atom4 #aa;,as radioactive nuclei disintegrate1 they change to other radioactive forms--their 8daughter0 products4 ,every radioisotope is thus part of a chain or series of steps that ends with a stable form4 ,technetium-#iim is a daughter product of molybdenum-#ii2 it decays by a process known as isomeric transition to a state of lower energy and longer half-life4 #ab,the curie is the basic unit of radiation intensity4 ,one curie is approximately the amount of radioactivity in #a gram of radium4 #ac,see ,your ,body and ,radiation and ,the ,genetic ,effects of ,radiation1 other booklets in this series1 for detailed explanations of radiation effects4 #ad,the use of radium is not under ,,aec control4 #ae,one family of measuring instruments is described in ,whole ,body ,counters1 another booklet in this series4 ,these are large devices that make use of scintillating crystals or liquids4 ,transcriber's ,notes --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,where possible1 ,,utf superscript and subscript numbers are used2 some e-reader fonts may not support these characters4 --,in the text version only1 underlined or italicized text is delimited by underscores4 --,in the text version only1 superscript text is preceded by caret and delimited by brackets4 --,in the text version only1 subscripted text is preceded by underscore and delimited by brackets4