IAEA-152 THYROID RADIONUCLIDE UPTAKE MEASUREMENTS PAPERS PRESENTE PANEA T DA L MEETING ORGANIZEE TH Y DB INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, AUSTRIA ,197 Y 17-21MA 1 A TECHNICAL REPORT PUBLISHED BY THE INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, 1973 The IAEA does not maintain stocks of reports in this series. However, microfiche copies of these reports can be obtained from INIS Microfiche Clearinghouse International Atomic Energy Agency Kärntner Rin1 g1 P.O. Box 590 A-1011 Vienna, Austria on prepayment of US $0.65 or against one lAEAmicrofiche service coupon. PLEAS AWARE EB E THAT MISSINE TH F GO L PAGEAL THIN SI S DOCUMENT WERE ORIGINALLY BLANK POREWORD Tests of thyroid function based on measurements of the uptake of radioiodine by the gland (thyroid uptake tests) con- stituted one of the first diagnostic applications of radioactive tracers and have been widely used in the diagnosis and investiga- tio thyroif o n d diseases n I96 I Internationae . 0th l Atomic Energy Agency invited a group of consultants to draw up a standardized procedure for such uptake measurements. The recommendations of this group related primarily to measurements of the uptake of I 24 hours after its oral administration - the basis of the thyroid uptake test most commonly performe werd I96n i an de 0 - publishen i d a number of scientific journals. Durin ensuine gth g decade thyroid uptake tests underwent con- siderable development. New radionuclides were utilized, new instru- ment d techniquean s measuremene th r fo s uptakf o t e were devisedd ,an n increasina g emphasi places swa uptakn o d e measurements made relatively soon after administration of the radioactive tracer. Parallel development took plac n testi e s f radioinvolvino e -us e gth nuclides but based on measurements of parameters other than uptake. In view of these advances the Agency decided in 1970 to convene a second panel of experts to review the status of thyroid uptake tests and to up-date, and where necessary amend, the I960 recommendations. ThiAgency'e th s t panea t s lme Headquarter y Ma 1 2 so t fro 7 1 m s repor it 197bee s d ha t1nan submitte publicatior fo d scientifio t n c journal Englishe th n si , French, Russia d Spanisnan h languagese Th . various working papers presented durin meetinge gth , which contain information supplementary to that given in the report, have been gathered togethe thin ri s document orden ,i r thae tb they ma y available to all interested persons. CONTENTS I CLINICAL ASPECTS Clinical requirements for thyroid radioisotope uptake measurement s ......................................... 1 . WAlexandeD . d J.Gan r . Shimrains Observation e rationalth n o s r thyroifo e d uptake measurement polemia : s c ............................7 . C.C. Harri J.Kd an s . Goodrich I I CHOIC RADIONUCLIDP O E E Radioiodine dosimetry and the use of radioiodines other than ^-^1 in thyroid diagnosis. ................ 13 H.N. Wellma d R.Tan n . Anger. Jr , Thyroid 1-131 uptake measurements and the determina- tion of effective half-life of 1-131 in patients with the rapeutic doses... ................................. 31 H. Kakehi . Saegus. TatenK Y , d oan a III EARLY UPTAKE MEASUREMENTS 99 m The measurement of thyroid uptake using To ........ 41 A. W.O. Goolden, H.I. Glas d E.Dan s . Williams 1 3 1 99m The measurement of the thyroid uptake of Tc , I and 2j a-t early times after isotope administration. 63 J.G. Shimmin W.Dd san . Alexander e measuremenTh kinetie th f o tc constant describing the thyroidal concentratio d organinan c "bindinf o g iodide and pertechnetate. ............................ 75 J.G. Shimmins, J.¥.K. Robertson, W.D. Alexanded ran J . Lazarus Quantitative scintigraph e stud th earlf o yn i y y thyroid uptake ......................................1 9 . B. Bok IV LATE UPTAKE MEASUREMENTS The performance of the IAEA standard collimator for thyroid radioiodine uptake measurements with fadio- nuclides other than 131i. ............................ 121 R.G. Daou Spectral region assessment of the influence of thyroid dept thyroin o h d radioiodine uptake. ........5 13 . H.N. Wellman, J. Tieman and E.L. Saenger Method of measuring thyroid 1-131 uptake by a digitized scintigram of thyroid gland. ............... 149 H. SaegusKakehK d an ia Thyroid 1-131 uptake measurement with a scintillation camera. .............................................. 157 H. Kakehi and K. Saegusa SELECTED BIBLIOGRAPHY 165 CLINICAL REQUIREMENT THYROIR SFO D RADIOISOTOPE UPTAKE MEASUREMENTS ¥.D. Alexander and J.G. Shimmins University Department of Medicine Gardiner Institute; Western Regional Hospital Board Regional Departmen Clinicaf o t l Physic d Bio-Engineerinsan g Glasgow, Scotland ABSTRACT This paper discusses the clinical requirements for thyroid uptake tests in relation to other tests of thyroid function, with particular reference to the assessment of the response of the thyrotoxic patient to therapy. The 20-minute thyroid up- take test is especially useful for the latter purpose since t i indicate underlyine th s g functiona lthyroi e statth f s o ea d distinct fro s ratit m f hormono e e production usee r b fo dn ca , repeated assessment s i itsel d an sf unaffecte antithyroiy "b d d drugs. Introduction Thyroid function tests have been of great value in the diagnosis of thyroid disease t untibu , l recently the/have bee managen i littlf no e eus - ment. If in the thyrotoxic patient one wants to confirm the clinical diagnosis, then thyroid functio ne othe th test n e usefulro ar shand , If ., one want knoo t s w whether drug r destructivo s e treatment will ultimately giv bese eth t results, then thyroid function test usualle ar s y of no help whatever. Help is needed because each form of treatment of thyrotoxicosis has a major disadvantage. As far as radioiodine therapy is concerned the chief trouble has been the high incidence of late hypothy- roidism. After subtotal thyroidectom incidence yth f relapseo hypod ean - thyroidism taken together has generally been considerable. The chief I problem with antithyroid drug therapy is that half the patients relapse after completin normaga l cours treatmentf eo coule on df I predic. t a t e beginningth r durino , firsmonthse w gth fe t treatmenf o , t which patients would relapse and which would remain euthyroid after longterm antithy- roid drug therapy, then treatment could be rationalized by using radio- iodine or surgery for those patients unsuitable for drug therapy. Diagnostie cUs Chemical measurements (PBI, thyroxine iodine, free thyroxine index) are used more frequently than thyroid radioiodine uptake measure- ments. But considerable use of thyroid uptake measurements continues. In one clinic the monthly figures were - Thyroxine iodine estimations 500 Thyroid radioiodine uptake 50 Initial assessemen f Graveso t ' disease We have reexamined the question whether any of the features of thyrotoxicosis observed at the initial assessment correlate with a good prognosis after antithyroid drug therapy. Factors "which sho wsignifia - cant difference in the group of patients who remained euthyroid after completion of treatment include goiter size, 2-minute thyroid radioiodine uptake, 20-minute thyroid radioiodine uptake, and protein-bound iodine. Assessment of response during antithyroid drug treatment When assessing the response to treatment during antithyroid drug therap requiree yon s informatio fouf no r different kings. 1. Is the patient hyper- eu- or hypothyroid, i.e., what is the level of thyroid hormone production? 2. What is the underlying functional state of the thyroid as distinct from the level of thyroid hormone production? 3. What is the prognosis, i.e., is the patient drug-responsive and suitabl r longterefo m antithyroid dru grelapsee therapysh s i r -o , pron betted ean r treate operatioy db r radioiodineno ? f longterI . 4 m antithyroid drug therap s beinyi g given, when nca treatment be discontinued? The 20-minute thyroid uptake during antithyroid drug therapye Th . ZO-minute thyroid radioiodine uptake measures a different parameter of iodine metabolism compared with conventional uptake measurements •whic s speciahha l clinical valu patientn ei s receiving antithyroid drug therapy. This is because it reflects principally the iodide trapping functioaccumulatioe thyroide th th , f e. o n . e i ,th iodidy f nb o n eio thyroid gland. Radioiodine test thif o s s type allow assessmenf o t thyroid function during treatment with antithyroid drugs, and are unique than i t they indicat underlyine eth g functional thyroie statth f eo s da distinct from the level of thyroid hormone production (Figs. 1 and 2). The tracer dose has to be given intravenously since otherwise the rate of absorptio t wouln gu fro e dm th interfer e 'wit resule teste hth th f .o t Perhap s fai i dra o t t ri s analog n wa y betwee 20-minute nth e uptake and the ESR during treatment of tuberculosis or rheumatic fever. The ESR reflects the activity of the tuberculous disease and when it returns normagoof o t o s di prognostit i l c significance. However, thero n s ei guarantee that the ESR will not rise again, the result of reactivation of 3 diseasee t th seemi d an s, that exactl same yth e 20-minut s trueth i f eo e thyroid uptake in thyrotoxicosis (Figs. 3 and 4). Assessmen f Responso t e After Antithyroid Treatment After antithyroid drug therapy is discontinued, it is usually unnecessary to make measurements of both thyroid uptake and circulating hormone. The latter alone is sufficient since the values are concordant. However, in three patients unexpected results were observed. 20 Ml N. FREE T •IVROXINE UPTAKE0/ IN DEX Ml . .M •30 é" 20 Uptah«m M 0 2 %A •20 s HI Tniodothyrofiin» 10 -10 \\ —————— C'-*>\ .