SELF-STUDY TEST

Radiobiology and Radiation ProtectionQuestions are taken from the Nuclear Medicine Self-StudyProgramI,

published by The Society of Nuclear MedicineDIRECTIONS

The followingitems consist of a question or incomplete statement followedby five lettered answers or completions.Select the one lettered answer or completion that is best in each case. Answers may be found on page 1182.

25. MakrigiorgosGM, AdelsteinSJ, KassisAl. Limitationsof conventionalinternal dosimetry at the cellular level. JNuclMed i989;30:1856—1864.

26. FenechM, MorleyA. Measurementofmicronuclei in lymphocytes.MzaatRes l985;i47:29—36.

27. Aimassy Z, Krepinsky AB, Bianco A, Kotcies Gi. The present state andperspectives of micronucleus assay in radiation protection. A review. ApplRadiat Isot l987;38:241—249.

28. Cole A. Absorptionof 20-eV to 50,000-eVelectronbeams in air andplastic. Radia: Res 1969;38:7—33.

29. Kassis Al, Adeistein Si, Haydock C, Sastry KSR. Thallium-201: an experimental and a theoretical radiobiological approach to dosimetry. I Nuci

Med 1983;24:l164—1175.30. FeinendegenLE.High LET-emittersand their relativebiologicaleffective

ness. In: SchubigerPA, Hasler PH, eds. Radionuclidesfor therapy. Proceedings ofthe 4th Bottstein colloquium; Villigen, Switzerland; June 13—14,1986:39—57.

31. Cole J, ArIeti CF, Green MHL Ct al. Comparative human cellular mdiosensitivity. II. The survival following gamma-irradiation of unstimulated(G0) T-iymphocytes, T-lymphocyte lines, lymphoibiastoid cell lines andfibroblasts from normal donors@from ataxia-telangiectasia patients andfrom ataxia-telangiectasia heterozygotes. mt i Radiat Biol l988;54:929—943.

Truestatements concerning radiation-induced thyroidcancerinclude:

I . Alltypesofthyroidcancerareincreasedinincidencebyradiation exposure.

2. Itis unlikelyto develop as a consequence ofadministrationof 1311in dosesusedin the diagnosisor therapyofthyrotoxicosis.

3. Itcan be distinguishedfromthatoccurring spontaneously.4. It ismorelikelytoresultfromexposuretothethyroiddur

ing adolescence than in early childhood.5. Itis more common followingexternal than internalradia

tion exposure.

True statements concerning probability of causation (PC)calculations for radiation-induced cancers include:

6. Theypertaintoaparticularcancerdiagnosedata particular timefollowinga particularradiationexposure.

7. The PC is equal to the relativeriskfor radiation-inducedcancerdividedbythesumofthatriskandthespontaneousrisk.

8. They may be applied to patients exposed to diagnosticand therapeuticradiation.

9. Theyconsiderage,sex,andcigarettesmokinghabitsaswellas radiation exposure.

10. Theyare basedon the linear—quadraticmodelforallcancers.

Iodine-131therapy forcarcinoma ofthe thyroidhas been shownto cause

I I . excessdeathsfromcancerofthebladder.12. excessdeathsfromleukemia.13. increasedincidenceofmalignantsalivaryglandtumors.14. reducedfertility.I 5. overtevidenceofgeneticdamage.

True statements concerning 1311therapy for thyroid cancerInclude:

I 6. Radiationeffectsontheparathyroidglandsoccurinabout10% of patients.

17. The limitingtissueresponseoccursinthe bonemarrow.18. Radiationnephritisoccursinabout5% ofpatients.19. Cytogeneticchangesincirculatinglymphocytesaredirect

ly related to the blood dose.20. Radiation-inducedvomitingoccurs in more than 20% of

patients.

Radiation-relatedeffectsfrom high-dose32@therapyofpolycythemia vera include:

21. thyroidcancer22. leukemia23. leukopenia

Truestatements regarding radiationtherapy withradiolabeledmonoclonal antibodies include:

24. Itis effectiveprimarytherapy for several types ofcancer.25. The radiation dose distributionwithina typical tumor is

sufficientlyuniformtoensureatumoricidaldosethroughout the tumorvolume.

26. The doseto normaltissues does notlimittheeffectivenessof radiolabeled monoclonal antibodies as a sole methodof treatment.

27. Alpha-emittingradionuclides are preferred.

For radiation protection purposes it is generally assumed thata dose to a portion ofthe bone marrow can be averaged overthe entire marrow. Concerning this concept,

28. a dose of 800 rads to 40% of the marrow is equivalentto 320 rads to the whole marrow.

29. the dose calculatedinthisfashionisthe same asthe meanmarrow dose.

30. the assumption isconsistentwitha dose-response modelincorporatingquadraticterms.

31. the assumptionapplies if partialbody doses are highenoughto killcells.

32. the assumptionisthe basisofthe dose equivalentconcept.

(continued on page 1182)

1174 The Journal of Nuclear Medicine•Vol.33 •No. 6 •June 1992

by on March 31, 2020. For personal use only. jnm.snmjournals.org Downloaded from

SELF.STUDY TEST

Radiobiology and Radiation ProtectionQuestionsaretakenfromthe NuclearMedicineSelf-StudyProgramI,

published by The SoCietyof Nuclear Medicine

SELF-STUDY

Skeletal NuclearTESTMedicineAN$WIR$

1989;l73:469—475.6. HashimotoY, StassenJM,LcclefB,ct al. Thrombosisimagingwithan I-

123-labeled F(ab'h fragment ofan antihuman fibrin monoclonal antibodyin a rabbit model. Radiology 1989;ill:223—226.

7. Rosebrougji SF, McAfee JO, Grossman ZD, et al. Thrombosis imagins@acomparison of radiolabeled GC4 and T2G1S fibiin-specific monoclonalantibodies. JNuclMed 1990;31:1048-l054.

8. Rubin RH, FischmanAS,NeedlemanM, et al. Radiolabeled,nonspecific,polyclonai human immunogiobulin in the detection offocal inflammationby scintigraphy with gallium-87 citrate and technetium-99m-iabeled albumm. JNuclMed 1989;30:385—389.

9. KairemoK.JA,WiklundTA, LiewendahiK, MiettinenM, HeikkonenJJ,Ct al. Imaging ofsoft-tissue sarcoma with indium-ill-labeled monocionalantimyosin Fab fragments. INuc/Med i990,3i:23-3l.

10. FlschmanAJ. When magic ballets ricochet [Editorial].I NucI Medl990;3l:32—33.

Yournuclear medicine clinic operates from 8AMto 5PMMonday through Friday and is closed on Saturdays and Sundays.On Friday afternoon at 1PMa technologist who was preparing 9@mTcmacroaggregated albumin dropped the (99mTc]pertechnetate stock vial. The vial, which contained 20 GBq(about 500 mCi) of (99mTcJpertechnetate, broke and its contents splashed on the floor, the wall, and the adjacent cabinets.The contaminated area was infrontofthe radioactive materialstorage and waste disposal area, which is about 4 m from thedose preparation area and the dose calibrator. Which of thefollowing statements concerning this accident are true?

33. Theamountof99―Tcspilledistoolargetobe ignoredandto be allowed to decay to background levels.

34. The amountof O9mTcspilledis sufficientlygreat thattheperson whocleans up the debris and decontaminates theareashouldwearleadgloves,a leadapron,andspecialdisposable clothing.

35. Theexposurerate(mR/hour)inthedosecalibrator/dosepreparationareawill be sufficientlygreatto requirethatworkinthisareabediscontinuedfortheremainderoftheday.

36. Thecontaminatedareashouldbecompletelydecontaminatedtobackgroundlevelsbeforeleavingfortheweekendso thathousekeepingpersonnelwill not be exposedtoexcessive radiation levels.

ITIN$ 1—5iRdlatlon-lnducd ThyroIdCancerANSWERS:1, F; 2, T;a F; 4, F; 5, TThyrcidcancer,in @spapillaryform,isthepredominantradia@on-inducedentity, with a lesser increase in follicular cancer. The incidences ofmedullaryand anaplasticcancersare not increasedby radiationexposurs The etiologyofindividualcases ofthyroidcancer cannot be attnbutedtoradiationbyanypathologicalcriteriacurrentlyknown.Exposureto1311hasnotbeenshowntocauseanincreasedincidenceofthyroidcancerinmedicallytreatedhumansubjects,whereasx-raytherapyhasbeen shownto be a potent cause, especially inthe youngest exposedindividuals,femalesbeingmoresensitivethanmales.Adolescentsareless sensitivethan youngerchildren.The relativeriskfollowingexternalirradiationisat leastthreetimesgreaterthanthatfollowingirradiationby internal emitters.

1. Schneider AB, Recant w, Pinsky SM, Ryo UY, Bekerman c, Shore-FreedmanE. Radia@on-induced thyrcid carcinoma. clinical course and results of therapyin 296 patienta Ann Intern Med 1986;105:405-412.

2. ShoreRE,WoodardED,PasternackBS,HempiemanLH.Radiationand hostfactors in human thyroid tumors fciI@ing thymus irradiation. Health Phys1980;38:451-465.

ITIMI S—lOiCalculatIngProbabllftyof CausationANSWERS:6,@7,1@8,F;9,1@10,FThe radioepidemiologictablesthat provideprobat@lftyofcausation (PC)values were designed to estimate the likelihood that a person who hasorhashada “radiation-related―cancerandwhoreceiveda specificdoseof radiationpriorto itsonsetdevelopedthediseaseasa resultoftheirradialon.Proba@yofcausalontablaspertalntoaparticularcancerin a particular individual.

Therelativeriskperunitofradiationdosecanbeusedtodeterminethe PC that a given cancer is the result of a previous exposure; this iscalculated by use of the following relationship:

PC—R/(1+ A),

whereAistherelati@riskduetoradiationexposureandthespontaneousriskis1.

Patientsexposedto diagnosticandtherapeutic radiationare differentfromthe general populationto some degree. Because ofselectionfactors otherthan radiation, PC values based on radiation risk factors and

(contlnusd on page 1215)

1182 The Journal of Nuclear Medicine•Vol.33 •No. 6 •June1992

REFERENCES

I. Hui KY, Haber E, Matsuda GR. Monoclonalantibodies to a syntheticfibrin-like peptide bind to human fibrin, but no fibrinogen. Sciencei983,222:l129—1132.

2. Rosebrough SF, Grossman ZD, McAfee JG, et al. Aged venous thrombi;radioimmunoimagingwith fibnn-specific monoclonal antibody. Radiologyl987;l62:575—577.

3. Knight LC, Maurer AH, Ammar IA, et al. Evaluation of indium-illlabeledanti-fibrinantibodyfor imagingvascularthrombi.J NuclMedi98829:494-502.

4. Rosebrough SF, Grossman ZD, McAfeeJG, et al. Thrombus ima@ngwithindium-ill and iodine-13i-iabeledfibrin-specificmonoclonal antibodyanditsF(ab'handF(ab)fragments.JNuclMed 198829:l2l2—l222.

5. Jung M, IGetterK, DudczakR, et al. Deep vein thmmbosis scintigraphicdiagnosiswith In-ill-labeled monoclonal anti-fibrin antibodies. Radiology

(continued from page 1174)

by on March 31, 2020. For personal use only. jnm.snmjournals.org Downloaded from

SELF-STUDY TEST ANSWERS

rests. These relatively simple meas- the patient relatively stationary during a, so far, unavoidable but often tolerures usually, but not always, maintainthe patient probably within a centimeter and/or a few degrees betweenthe transmission and emission measurements. This has been verified atour institution in a number of casesby carrying our two blood-pool imaging procedures before and aftermeasurements to verify the correctposition ofthe patient. This approachoffers the added advantage of keeping

transmission and emission measurements, in addition to maintainingalignment between emission andtransmission images.

It is very useful to know the magnitude of the effect produced by misalignment as a function of patienttranslations and/or rotations. Withproper care, these motions can be keptto a minimum, under which circumstances the described effect introduces

able source of error.

M.M. Ter-PogossianWashington University

St. Louis, Missouri

REFERENCE

1. Thompson Ci, Ranger N, Evans AC, Gjedde A.Validation of simultaneous PET emission andtransmission scans. J Nuci Med 1991;32:154—160.

(continuedfrompage 1182)

baselineratesin the generalpopulation would not apply. For instance,anorgantransplantpatientmaybeata muchgreaterrisk,asmuchas30 timeshigher insome cases, forcancer duringhisor her lifetimecompared with a typical member of the population.

Becauseof theestablishedvariationin incidenceforspontaneousandradiation-inducedcancer, PC tables must take into account both ageand sex. Becausetobacco smoking (particularlycigarettesmoking) isthesinglemostimportantexternalriskfactorforhumancancer,estimatedto cause 25%_40% of all cancer deaths in the U.S., it is alsotakenintoaccount.

Theweightof radiobiologicalevidencefavorsa linear—quadraticdoseresponse to low-LET radiation for most cancers. Thyroid cancer andfemale breastcancer are exceptionsin that the epidemiologic data forthese cancers strongly favor a linear dose response.Reference1_ Gur D, Wald N. Probability of causation tables and their possible implications

forthepracticeof radiologyRadiology1986:158:853-854.

ITEMS 11—15:RIsks of 1311Therapy for Thyroid CarcinomaANSWERS: 11, T; 12, 1@13, F; 14, F; 15, FEdmondsand Smithhavereportedthefollow-up of258 patientstreatedwith high doses of 131lfor thyroid cancer.They observed a small butsignificant excess of deaths from cancer of the bladder and fromleukemia. Despite the high levels of irradiation of the salivary glands,no malignanciesand only one adenoma were found. No evidence ofreduced fertility or of overt genetic damage has been reported in individuals (and their offspring) treated with 131lfor thyroid cancerReferences1. Edmonds CJ. Smith T The long-term hazards ofthe treatment ofthyroid cancer

with radioiodine. Br J Radio! 1986:59:45-512. SakarSD. BeierwaltesWH.GillSR CowleyBJ Subsequent fertilityand birlh

historiesofchildrenandadolescentstreatedwith1311forthyroidcancerJ Nuc!Med 1976:17:460-464.

ITEMS 16-20: Adverse Effects of 131@ Therapy for ThyroidCarcinomaANSWERS: 16, F; 17, T 18, F; 19, T, 20, FUndesirable side-effects of radiation therapy with internal emitters aremuch less prominent than those encountered with external beam radiation therapyor chemotherapy.The parathyroidgland is rarelyclinicallyimpaired by eventhe highest dose proceduresto the thyroid with 1311;only isolated cases of hypoparathyroidismhave been reported. Thelimitingtissue dose is that to the bone marrow,which receivesapproximately 0.5 rad/mCi of 131ladministered to the patient with thyroid cancer.Radiationnephritis is not a reportedcomplication of 131I therapy (or ofother nuclear medicinetherapy).Mild nauseamayoccur, but vomitingis a rare complication (<lOb). Cytogenetic changes in circulating lymphocytesoccurafterinternalirradiationastheydo afterexternalradiation exposure.Theirfrequency iscorrelatedwith the exposureto blood.Reference1 EdmondsCJ,SmithT Thelong-termhazardsofthe treatmentofthyroid cancer

withradioiodine.BrJ Radio!1986:59:45-51

ITEMS 21-23: AdverseEffectsof32@Therapyof PolycythemiaVeraANSWERS: 21, F; 22, T 23, TPhosphorus-32administeredas the phosphate in high doses to treatpolycythemiavera has the desired effect of decreasing the number ofcirculating plateletsand erythrocytes.Leukopenia,predominantly lymphopenia,isnotedaswithanyotherhighwhole-bodyradiationexposure.Leukemiadoesoccur in increasedfrequencyin thesepatients,althoughit is not certain whether this is due to the radiation exposure per se or

to the longer lifespan of 32P-treatedpatients,giving more time for thenaturalevolutiontoleukemiathatoccursinthis diease.Noelevatedmcidenceofthyroidcancerhasbeen reportedin patientswithpolycythemiavera treated with 32@

ITEMS 24-27: Therapywith RadlolabeledMonoclonalAntibodiesANSWERS:24, F: 25. F: 26. F: 27, FRadiolabeled monoclonal antibodies show great promise for use indiagnosis. However,the tumor-to-background ratios achieved withradiolabeledmonoclonalantibodiesgenerallyhavebeentoo lowto permituseof theseagentsasthe solemeansof treatmentoftumor metastases.The radiosensitivityof the bone marrow usually limitsthe ability to obtama full therapeuticeffect.Nonuniformdose distributionis due in partto regionalbloodflowvariations,whichalongwithantigenicheterogeneity.nonspecificityoftumor-associatedantigens,andchangingantigeniccompositionoftumors, limmtthecurrentutilityof monoclonalantibodytherapy.Because it is difficult to ensure that antibodies will bind to each cell ofthe tumor.the useof radmonuclidesemittingshort-range,high-LETradiations (e.g., alpha particles)is not optimal. Beta emissionis more likelyto result in a more uniform dose distribution within the tumor.References1 Carrasquillo JA. Krohn KA. Beaummer P et al Diagnosis and therapy for solid

tumors with radmolabeledantibodies and immune fragments Cancer TreatRep1984.68317-328

2 Grossman ZD. Rosebrough SF ClinicalRadioimmunoimaging Orlando. FLGrune& Stratton.1988

3 Maners AW.Sanders MM. Pappas AA Current status of radmoligandantibodiesin the treatment of malignancy Ann C!in Lab Sc' 1988.1853-57

4 OrderSE Radmoimmunoglobulmntherapyofcancer Compr Ther1984.10 9-18

5. Vaughan AT.Anderson P Dykes PW. Chapman CE. Bradwell AR Limitationsof the killing of tumours using radiolabelied antibodies Br J Radiol1987.60 567-578

ITEMS 28-32: Dose-EquivalentConceptwith Bone MarrowExposureANSWERS: 28. T: 29, T: 30. F: 31. F: 32. FThereiscontroversyregardingthecomparabilityof riskcoefficientsbasedon partial-bodyradiationexposurewiththose basedon whole-bodyexposure.For the purposes of radiationprotection. it has been assumedthat a dose to a portion of the bone marrowcould be ‘‘averaged'‘overthe entire marrow (i.e., as in the example in the question. a dose of 800rads to 400/o of the marrow would be equivalent to a dose of 320 radsto the whole marrow).

(continuedon page 1242)

MisalignmentBetween PET Transmission and EmissionScans •Ter-Pogossian 1215

by on March 31, 2020. For personal use only. jnm.snmjournals.org Downloaded from

SELF-STUDY TEST ANSWERS

For further in-depth information, refer to the syllabus pages in Nuclear Medicine Self-Study I.

Med l98627:1830—1836.2. Garcia E, Van Train K. Maddahi J, et al. Quantification of rotational

thallium-20l myocardial tomography. I NuciMed 1985;26:17—26.3. O'Brien A, Gemmell H. Effectiveness of oblique section display in thaI

lium-20l myocardialtomography.NuciMed Comm 1986;7:609—6l6.4. DePasquale E, Nody A, DePucy E, et a!. Quantitative rotational Tl-201

tomography for identifying and localizing coronary artery disease. CircuIaiion 1988;77:316—327.

5. Tamaki N, Yonekura Y, Mukai T, et al. Segmentalanalysis of stressthallium myocardial emission tomography for localization of coronaryarterydisease. EurlNuclMed 1984;9:99—l05.

6. SendaM,YonekuraY,TamakiN,et al.Axialresolutionandthevalueofthe interpolatingscan in multislicepositroncomputedtomography.IEEETrans Med Imaging 19854:44—51.

7. HicksK, Ganti G, Mullani N, Gould KL. Automatedquantitationofthree-dimensionalcardiacpositronemissiontomographyfor routine dinical use.JNucIMed l989;30:l787—l797.

8. RaylmanR, HutchinsG, SchwaigerM,ParadiseA.Axialsamplingrequire

(continued on page 1215)

ments for 3-dimensionalquantificationof myocardialfunctionwith positron emissiontomography.IEEE TransNuc/Sci 1989;36:l030—1033.

9. SchaferR@,RabinerLW.A digitalsignalprocessingapproachtointerpolation. ProcIEEE 1973;61:692—702.

10. Carter WH. Image sampling and interpolation. SPIE l983;397:477—486.1 1. Keys RG. Cubic convolution interpolation for digital image processing.

IEEE TransAcoust,Speech,SignalProcessing1981ASSP-29:1153—1160.12. Macland E. On the comparison of interpolation methods. IEEE Trans

Med Imaging1988;7:213—217.13. Gambhir S. Quantitation ofthe physical factors affecting the tracer kinetic

modeling ofcardiac positron emission tomography data. PhD dissertation.University ofCalifornia, Los Angeles 1990.

14. BardY.Noniinearparamezerestimwion,1stedition.NewYork:AcademicPress;1974:341.

15. Karp J, Muehllehner G, MankofFD, et al. Tomograph with volumeimaging capability. I NuciMed l990;31:617-627.

16.MullaniN, GouldK, HartzR, et al. Designandperformanceof posicam6.5 BGO positroncamera.JNucIMed 1990;31:610—616.

This concept is consistentwith the@@ mean marrow dose,'â€w̃hich incorporates a linear dose-response model (500 rads to 50% the marrow would have the same effect as 250 rads to 100% of the marrow).Such an approach isclearly inconsistentwith a dose model that incorporates terms that are quadratic or otherwise nonlinear (the modelassumesthat 50 rads to 10% of an organ is equivalentto 5 radsto thewholeorgan—alinearextrapolation).Furthermore,if partial-bodydosesare high enough to kill a significantnumber of cells, the hypothesisissurely invalid.

Thedose-equivalentconcept is not relatedto partialorgan irradiation,but provides a method of expressingall kinds of radiation exposureson a common scale for calculating the effectiveabsorbed dose.R•for•nc•s1 InternationalCommissionon RadiologicalProtectionRadiosensitivityaridSpa

fial Distribution of Dose, Publication 14.New York. Pergamon. 1969.2 Rosenstein M. OrganDoses in DiagnosticRadiology.U.S.Departmentof

Health, Education, and Welfare, HEW Publication (FDA) 76-803. Washington.D.C.: U.S. Government Printing Office, 1976.

3 ShleienB.TuckerTT,JohnsonDW.Themeanactivemarrowdosetotheadultpopulationof the UnitedStatesfrom diagnosticradiology.HealthPhys1978:34.587-601.

ITEMS 33—36:Management of eemTcSpillANSWERS:33, T;34, F; 35, F; 36, FTheamountof99@―Tcspilled,20 GBq, isslightlymorethan 500 mCi.Thisclearlyisa majorspill,and itcannotbe ignoredunderanycircumstances.The exposure rate constant for @mTcis approximately70 mR/hr/Ciat1 m, from which it can be calculated that the exposure rate at the dosepreparationarea (4 m from a spill of 0.5Ci)will be on the order of about2 mR/hr.Thisisnotanalarminglyhighexposurerate,andworkinthisareacancontinueasnecessary.However,it wouldmostassuredlybeinconsistentwith ALARA philosophyto ignorethe spilland to allowpersonnelto continueto work in the areawithouteffortsto reduceexposurelevels.

Because of the large activity of 99Tcinvolvedand the relativelyhigh. probability ofcontaminating large areas of the nuclear medicine clinic

and hospitalifthe contaminationi@renotcontained,mostradiationsafetyofficerswould agree that some decontaminationis necessary.The activity is not so large, however,that extraordinary precautions must betakenduring the clean-up.Thefirststep is to containthe contamination,

i.e., prevent it from spreading beyond the immediatearea of the spill.The person who dropped the vial should have immediately placedenough absorbent materialon the spill to soak up all of the liquid onthe floor.He or she should then havecalled for assistanceand remained in the areauntila surveymeterwasbroughtto check for contamination of clothing and shoes.The second step should be stopping worklong enough to plan how best to proceed. Becausethe radiopharmaceutical is not significantlyvolatile,so long as people are excludedfromthe contaminated area, there is no immediate hazard to anyone.Thethird step is to put on disposable foot covers, two pairs of disposableplasticgloves,and eithera laboratorycoat or a surgicalscrub suit.Thefourth step is to quickly removeall of the broken glass and wet absorbent materialand place these into a heavy plastic bag or two nestedthin plastic bags; the plastic glovesshould be placed in the bag afterall of the other debris has been picked up. The fifth step is to attemptto removethe remaining superficial contaminationon the walls,cabinets,and floor.All of thesecontaminatedmaterialsshould be removedfromtheclinicareaand placed inan approvedradioactivewastestorageareaoverthe weekendfor decay.The dose rate in the area of the spill.which now will be substantiallylowerthan initially,should be reassessed witha surveymeter.Atthis point most radiationsafetyofficersprobably would recommend labeling the area with the proper radioactivematerialscautionsigns,cautioningnuclearmedicinepersonnelto avoidthe areaof the spill for the remainderof the day and over the weekend.and allowingthe 99mTcto decay over the weekend.The contaminatedregions of the floor might also be covered with polyethylenesheetingto further reduce the likelihood of dissemination.

If the accident had occurred on Monday morning insteadof Fridayafternoon,thefirstfivestepsfor handlingthespillshouldbethesame.In fact, this would be true regardlessof the time of the weekor the activityof @9mTcinvolved.However,becausethe areawillbe occupied moreintensivelyduring the 24-48 hr necessaryfor 99Tcto decay,greaterattention must be paid to the dose rate from the residualcontaminationandto determinewhetheranyofthe residualcontaminationis removableand might be disseminatedon individuals'shoesor clothing.The radiation safetyofficershouldsurveythe laboratoryand make recommendations about avoidanceof the contaminatedareasor other adjustmentsin work practices that will be required until the contamination has decayedcompletely.

1242 The Journal of Nuclear Medicine •Vol. 33 •No. 6 •June1992

by on March 31, 2020. For personal use only. jnm.snmjournals.org Downloaded from

1992;33:1174-1242.J Nucl Med.     Self-Study Test: Radiobiology and Radiation Protection

http://jnm.snmjournals.org/content/33/6/1174.citationThis article and updated information are available at:

  http://jnm.snmjournals.org/site/subscriptions/online.xhtml

Information about subscriptions to JNM can be found at:  

http://jnm.snmjournals.org/site/misc/permission.xhtmlInformation about reproducing figures, tables, or other portions of this article can be found online at:

(Print ISSN: 0161-5505, Online ISSN: 2159-662X)1850 Samuel Morse Drive, Reston, VA 20190.SNMMI | Society of Nuclear Medicine and Molecular Imaging

is published monthly.The Journal of Nuclear Medicine

© Copyright 1992 SNMMI; all rights reserved.

by on March 31, 2020. For personal use only. jnm.snmjournals.org Downloaded from