Imaging of the thyroid: Recent advances

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1 [Downloded free from on Wednesdy, Septemer 28, 2016, IP: ] IJEM_185_11R4 Review Article Imging of the thyroid: Recent dvnces Viks Chudhry, Shhin Bno 1 Deprtment of Rdiodignosis, Employees Stte Insurnce Corportion (ESIC) Model Hospitl, Gurgon , Hryn, 1 Deprtment of Rdiodignosis, Ldy Hrdinge Medicl College nd Associted Smt. Suchet Kriplni nd Klwti Hospitls, New Delhi, Indi ABSTRACT Although thyroid scintigrphy nd ultrsound continues to e the minsty of the dignostic imging of the thyroid glnd, there hve een severl recent dvnces tht re of interest to oth rdiologists nd endocrinologists. In this review rticle, the uthors discuss recent progress in imging of the thyroid y use of rdionuclide imging including single photon-emission computed tomogrphy/ positron emission tomogrphy, ultrsonogrphy (USG), USG elstogrphy, computed tomogrphy (CT), mgnetic resonnce imging (MRI), nd opticl coherence tomogrphy. Key words: Mgnetic resonnce imging, opticl coherence tomogrphy, rdionuclide imging, thyroid imging, recent dvnces, ultrsonogrphy, ultrsound elstogrphy, computed tomogrphy Introduction The thyroid glnd plys criticl role in regulting metolic functions including hert rte nd crdic output, lipid metolism, het regultion, nd skeletl growth. Recent dvnces in thyroid imging hve considerly improved the dignosis, tretment, follow-up, nd prognosis of high prevlence thyroid diseses such s thyroid nodule, goiter, thyroiditis, nd thyroid cncer tht ffect the norml thyroid function. The reltive roles of vrious imging modlities in the evlution of vrious thyroid diseses re discussed here. Techniques of Thyroid Imging Rdionuclide imging Rdionuclide imging (RNI) hs een prt of the thyroid evlution for mny yers. Now, it plys centrl role in Quick Response Code: Access this rticle online Wesite: DOI: / the evlution of thyroid disese s it provides excellent functionl informtion out the thyroid glnd. The most frequently used isotopes for thyroid scintigrphy re 99m Technetium pertechnette, 131 Iodine, 18 fluoro-deoxyglucose, nd gllium-67. Rdionuclide scnning using 99m Technetium pertechnette nd 131 Iodine is used in the evlution of focl thyroid nodule s hot, wrm, or cold on the sis of reltive uptke of rdioctive isotope y the nodule [Figures 1 4]. 131 Iodine, in ddition, is lso used in the tretment of ptients with thyroid cncer to evlute for residul/recurrent disese, to ssess distnt metstsis, nd in the follow-up of ptients fter thyroidectomy. Gllium-67 is prticulrly useful in ssessing thyroid lymphom. [1,2] Positron emission tomogrphy Two new rdionuclide techniques, nmely positron emission tomogrphy (PET) nd single-photon emission computed tomogrphy (SPECT) re of potentil interest in imging of the thyroid. F18-fluorodeoxyglucose-PET ( 18 F-FDG-PET) is well estlished imging modlity in oncology. Its gretest utility is in the evlution of thyroid cncers with dedifferentited tumors which re iodine scintigrphy negtive ut FDG- PET positive (in contrst to indolent slow growing thyroid tumors which re iodine scintigrphy positive ut FDG-PET negtive). [3,4] 18 F-FDG-PET hs een found Corresponding Author: Dr. Viks Chudhry, Deprtment of Rdiodignosis, Employees Stte Insurnce Corportion (ESIC) Model Hospitl, Gurgon , Hryn, Indi. E-mil: dr_vikschudhry@yhoo.com Indin Journl of Endocrinology nd Metolism / My-Jun 2012 / Vol 16 Issue 3 371

2 [Downloded free from on Wednesdy, Septemer 28, 2016, IP: ] Chudhry nd Bno: Thyroid imging Figure 1: Multinodulr goiter. 99m Technetium pertechnette (Tc-99m) scintigrphy imge of thyroid glnd, of 48-yer-old femle ptient with multinodulr goiter, shows multiple hot (thick rrow) nd cold nodules (thin rrow) involving oth the loes of the glnd (left>right). Figure 2: Foliculr crcinom. Tc-99m scintigrphy imge of thyroid glnd, of 55-yer-old femle ptient with plple right sided neck mss, revels lrge non-functioning cold nodule in right upper pole (rrow). The dignosis of folliculr crcinom ws mde on histopthology fter resection of the nodule Figure 3: Folliculr denom. Tc-99m scintigrphy imge of thyroid glnd, of 47-yer-old femle ptient with plple left-sided neck mss, demonstrtes n ill-defined re of incresed ctivity in left lower pole consistent with hot nodule (rrow). The dignosis of folliculr denom ws mde on histopthology fter resection of the nodule Figure 4: Grves disese. Tc-99m scintigrphy imge of thyroid glnd, of 32-yer-old mle ptient who presented with neck mss nd proptosis, demonstrtes enlrged thyroid glnd with diffuse incresed uptke of the trcer to e the most ccurte method for detecting recurrent or metsttic medullry thyroid crcinom (MTC) in ptients with n elevted clcitonin level (tumor mrker for MTC) postopertively, when other rdionuclide nd cross-sectionl imging techniques fil to loclize the tumor or metsttic disese. It is lso superior to other imging modlities in loclizing cervicl nd medistinl lymph node involvement. [5-7] The comintion of PET with CT or MRI (PET/CT or PET/MRI) which llows fusion of functionl nd ntomic informtion hs very promising role in the evlution of thyroid cncer. The sensitivity nd specificity of FDG PET-CT to detect the suspected occult lesions nd residul/recurrent well-differentited thyroid cncer (DTC) is very high. Currently, whole-ody FDG PET-CT is recommended for ssessing the metstses of DTC in ptients with rdioiodine negtive scns nd elevted serum thyrogloulin (Tg) levels. This is prticulrly useful in guiding tretment decisions. [8,9] FDG PET is lso useful in differentiting incidentlom (show focl uptke of FDG y the glnd) from thyroiditis nd/or hypothyroidism (show diffuse uptke of FDG y the glnd); nd mlignnt thyroid nodule (show high FDG vidity, pproching 100%) from enign nodule (show low FDG vidity, ~30%). [3,10,11] 372 Indin Journl of Endocrinology nd Metolism / My-Jun 2012 / Vol 16 Issue 3

3 [Downloded free from on Wednesdy, Septemer 28, 2016, IP: ] Chudhry nd Bno: Thyroid imging Single photon emission computed tomogrphy SPECT is currently used with incresed frequency due to its ility to provide the three-dimensionl informtion which improves the overll sensitivity for detection nd locliztion of thyroid lesion. 131 I SPECT-CT hs een found to e more ccurte thn FDG PET-CT in loclizing the regionl nd distnt metstsis nd in detecting residul/ recurrent disese in the cse of well-differentited thyroid cncer. The most importnt dvntge of fusion FDG PET-CT nd 131 I SPECT-CT is detection of metstsis in norml sized lymph nodes. [9] The mjor drwck of FDG-PET is its poor specificity to differentite etween infective or inflmmtory processes nd the neoplsm, s well s its poor sensitivity to detect micrometstses nd tumor sites in well-differentited thyroid cncers tht concentrte iodine. The mjor drwck with 131 I SPECT is tht vrious physiologicl vrints my mimic disese. [9] Ultrsonogrphy Ultrsonogrphy is generlly the first choice nd the most sensitive imging modlity for dignosing intrthyroid lesions. Becuse of its superficil loction, the thyroid glnd is idelly suited for high-frequency sonogrphy (using 7-13 MHz trnsducer) which fcilittes the detection of cliniclly non-plple nodules of 2-3 mm size nd llows more ccurte morphologicl chrcteriztion of the lesion. It is lso used to determine the size nd numer of thyroid nodules, to ssess the volume of thyroid tissue in cses of thyromegly, nd to differentite thyroid msses from djcent non-thyroid msses. Addition of color nd spectrl Doppler imging tht determines the vsculr pttern of thyroid diseses hs een found to e very useful tool in screening the thyroid nodule for mlignncy. A nodule with exclusively centrl vsculr pttern is chrcterized s mlignnt, while nodule with predominntly perinodulr pttern is generlly enign. The gry scle ultrsonogrphic pttern ssocited with thyroid crcinom includes solid, hypoechoic mss tht is tller thn wide, hs n irregulr mrgin nd microclcifictions ut sent hlo sign. The improved gry scle nd Doppler sonogrphy hs incresed the ccurcy nd specificity of ultrsound for thyroid diseses [Figures 5-8]. This comintion is lso helpful in evlution of cervicl lymphdenopthy. Metsttic lymph nodes pper hypoechoic nd show lck of centrl hilr echogenicity nd vsculrity. [3,12-15] Ultrsound elstogrphy Ultrsound (US) elstogrphy mesures the tissue elsticity nd differentites etween enign nd mlignnt nodule on the sis of consistency of the lesion. A enign nodule is softer nd hence deforms more esily, wheres the mlignnt nodule is hrder nd hence deforms less when compressed y ultrsound proe. Cystic nodules nd nodules hving clcified shell re excluded from the US elstogrphic evlution. US elstogrphy hs high predictive vlue in chrcterizing n indeterminte nodule s mlignnt with its effectiveness lmost comprle to fine-needle spirtion cytology (FNAC). [3,15-17] Other improvements in ultrsonogrphy Use of specific contrst (e.g. SonoVue) nd pulse inversion hrmonic imging hs further improved the efficcy of ultrsound to chrcterize thyroid nodule. [18] Ultrsonogrphy-guided fine needle spirtion iopsy (FNAB) is prticulrly helpful in the cse of nonplple or smll nodules or the nodules tht re difficult to ccess nd is preferle to plption-guided FNAB y mny pthologists for pproprite nodule selection. [19] Min limittion with use of USG is significnt overlp etween enign nd mlignnt thyroid nodules; hence, FNAB is necessry in mny cses with equivocl findings. [19] US elstogrphy lso hs limittion in ssessing lesions tht re not surrounded y dequte norml tissue. [15] Computed tomogrphy nd mgnetic resonnce imging Computed tomogrphy (CT) nd mgnetic resonnce imging (MRI) hve n djuvnt role in the evlution of thyroid disese. CT nd MRI re less sensitive thn USG in detecting nd chrcterizing intrthyroid lesions s enign nd mlignnt. They re prticulrly used for stging thyroid cncer s they re useful in evluting regionl lymphdenopthy, ssessing loco-regionl extension of the tumor (prticulrly involving trche nd esophgus), spred of disese into the medistinum or retrotrchel region nd detecting pulmonry nd heptic metstses. CT nd MR imging re lso recommended to evlute the occult metstses (medistinl or retrophyngel) in post-thyroidectomy follow-up cses with elevted serum Tg level nd negtive sonogrphic finding. [1,20,21] CT, in prticulr, is most sensitive in detecting intrglndulr clcifiction [Figure 9]. Fusion PET-CT nd PET-MRI ply promising role in the evlution of thyroid cncer. [9] Diffusion-weighted imging (DWI) my e helpful in differentiting enign nd mlignnt nodules. Benign nodules hve higher pprent diffusion coefficient (ADC) vlues thn mlignnt ones. [22] MR spectroscopy using long echo-time (TE) hs een proved to e sensitive method in differentiting thyroid crcinom from enign folliculr lesion. Choline pek is identified in lmost ll crcinoms, with rised choline/cretine rtio rnging from 1.6 in well Indin Journl of Endocrinology nd Metolism / My-Jun 2012 / Vol 16 Issue 3 373

4 [Downloded free from on Wednesdy, Septemer 28, 2016, IP: ] Chudhry nd Bno: Thyroid imging Figure 5: Hshimoto s thyroiditis. Trnsverse gry-scle ultrsound () nd color Doppler () neck, of 35-yer-old femle ptient, who presented with fetures of hypothyroidism nd hd ntithyroid ntiodies positive for the disese, demonstrtes diffuse enlrgement of thyroid glnd with liner echogenic firous nds (rrowheds) ut norml vsculrity. Note smll hypoechoic lymph node (rrow) in posterior spect of inferior pole of left loe of the thyroid glnd Figure 6: Folliculr lesion thyroid. Trnsverse gry-scle ultrsound () nd color Doppler () neck, of 40-yer-old femle ptient, shows lrge well circumscried iso-hypoechoic solid thyroid nodule with multiple internl cystic spces (rrow) nd oth centrl nd peripherl vsculrity Figure 7: Benign thyroid nodule with lrge intrtumorl cyst. Trnsverse gry-scle ultrsound () nd color Doppler () neck, of 55-yer-old femle ptient, revel well-circumscried right-sided thyroid nodule (rrow) with lrge intrtumorl cyst nd solid peripherl component which shows incresed vsculrity. The lesion demonstrtes thin hypoechoic rim nd posterior coustic enhncement Figure 8: Multinodulr goiter. Trnsverse gry-scle ultrsound () nd color Doppler () neck, of 50-yer-old femle ptient, shows enlrgement of oth thyroid loes nd isthmus y multiple iso-hyperechoic solid nodules (rrowheds). There is mrked increse in vsculrity within the glnd differentited crcinom to 9.4 in nplstic crcinom. The norml thyroid tissue nd enign folliculr lesions generlly demonstrte no choline pek.[23] mgnifiction resulting in cellulr imging. OCT/OCM system uses infrred light in fier ctive device tht llows visuliztion of microstructures of glnd (1-15 µm cellulr rnge) nd provides high resolution imges comprle with those otined using histopthologic methods. OCT nd OCM cn clerly differentite etween enign nd mlignnt thyroid tissue using intrinsic opticl contrst.[24,25] Opticl coherence tomogrphy nd opticl coherence microscopy Opticl coherence tomogrphy (OCT) nd opticl coherence microscopy (OCM) re emerging imging technologies sed on inherent opticl contrst. OCT provides high-resolution, rel-time, cross-sectionl imging of tissues. OCM is n extension of OCT nd provides high 374 Conclusion In generl, the thyroid imging hs evolved from erly Indin Journl of Endocrinology nd Metolism / My-Jun 2012 / Vol 16 Issue 3

5 [Downloded free from on Wednesdy, Septemer 28, 2016, IP: ] Chudhry nd Bno: Thyroid imging c Figure 9: Multinodulr goiter. Plin xil () nd contrst-enhnced xil () nd coronl (c) CT scn neck region, of 52-yer-old femle ptient, shows enlrgement of ilterl thyroid loes due to presence of multiple non-enhncing hypodense (thin white rrows) nd clcified thyroid nodules (thin lck rrows) rdionuclide thyroid scnning to the development of the dvnced technique of SPECT, PET nd fusion imging. The dvncement in cross-sectionl techniques such s USG, CT nd MRI hs further improved the evlution of intrthyroid pthologies. OCT hs supplemented the imging for etter selection of ptients for opertion. Acknowledgement The uthors would like to thnk Dr. Deep Prjpti for providing Tc-99m scintigrphy imges. We lso thnk Dr. Deepti Jin for the unconditionl support. References 1. Hopkins CR, Reding CC. Thyroid nd prthyroid imging. Semin Ultrsound CT MR 1995;16: Gtes JD, Benvides LC, Shriver CD, Peoples GE, Stojdinovic A. Preopertive thyroid ultrsound in ll ptients undergoing prthyroidectomy?. J Surg Res 2009;155: Soto GD, Hlperin I, Squrci M, Lomen F, Domingo MP. Updte in thyroid imging: The expnding world of thyroid imging nd its trnsltion to clinicl prctice. Hormones (Athens) 2010;9: Feine U, Lietzenmyer R, Hnke JP, Held J, Wöhrle H, Müller- Schuenurg W. Fluorine-18-FDG nd iodine-131-iodide uptke in thyroid cncer. J Nucl Med 1996;37: Ersoy R, Krko A, Atsever T. Imging techniques for metsttic thyroid medullry cncer. Turk J Endocrinol Met 2002;4: Reding CC, Gormn CA. Thyroid imging techniques. Clin L Med 1993;13: Heshmti HM, Ghri H, Vn Heerden JA, Sizemore GW. Advnces nd controversies in the dignosis nd mngement of medullry thyroid crcinom. Am J Med 1997;103: Zoller M, Kohlfuerst S, Igerc I, Kresnik E, Glloeitsch HJ, Gomez I, et l. Comined PET/CT in the follow-up of differentited thyroid crcinom: Wht is the impct of ech modlity?. Eur J Nucl Med Mol Imging 2007;34: Wong KK, Zrzhevsky N, Chill JM, Frey KA, Avrm AM. Hyrid SPECT-CT nd PET-CT imging of differentited thyroid crcinom. Br J Rdiol 2009;82: Vn den Bruel A, Mes A, De Potter T, Mortelmns L, Drijkoningen M, Vn DB, et l. Clinicl relevnce of thyroid fluorodeoxyglucosewhole ody positron emission tomogrphy incidentlom. J Clin Endocrinol Met 2002;87: De Geus-Oei LF, Pieters GF, Bonenkmp JJ, Mudde AH, Bleeker- Rovers CP, Corstens FH, et l. 18F-FDG PET reduces unnecessry hemithyroidectomies for thyroid nodules with inconclusive cytologic results. J Nucl Med 2006;47: Gooding GA. Sonogrphy of the thyroid nd prthyroid. Rdiol Clin North Am 1993;31: Kerr L. High resolution thyroid ultrsound: The vlue of color doppler. Ultrsound Q 1994;12: Hong JK, Lee WK, Lee M, Johnson D, Frrell S. US Fetures of thyroid mlignncy: Perls nd pitflls. Rdiogrphics 2007;27: Rgo T, Vitti P. Role of thyroid ultrsound in the dignostic evlution of thyroid nodules. Best Prct Res Clin Endocrinol Met 2008;22: Rgo T, Sntini F, Scutri M, Pincher A, Vitti P. Elstogrphy: New developments in ultrsound for predicting mlignncy in thyroid nodules. J Clin Endocrinol Met 2007;92: Lyshchik A, Higshi T, Asto R, Tnk S, Ito J, Mi JJ, et l. Thyroid glnd tumor dignosis t US elstogrphy. Rdiology 2005;237: Brtolott TV, Midiri M, Qui E, Bertolotto M, Gli M, Cdemrtiri F, et l. Benign focl liver lesions: Spectrum of findings on SonoVue enhnced pulse-inversion ultrsonogrphy. Eur Rdiol 2005;15: Frtes MC, Benson CB, Chroneu JW, Cis ES, Clrk OH, Colemn BG, et l. Mngement of thyroid nodules detected t US: Society of Rdiologists in Ultrsound consensus conference sttement. Rdiology 2005;237: Imnishi Y, Ehr N, Mori J, Shimokw M, Skuym K, Ishikw T, et l. Mesurement of thyroid iodine y CT. J Comput Assist Tomogr 1991;15: Americn Thyroid Assocition (ATA) Guidelines Tskforce on Thyroid Nodules nd Differentited Thyroid Cncer, Cooper DS, Doherty GM, Hugen BR, Kloos RT, Lee SL, et l. Revised Americn Thyroid Assocition mngement guidelines for ptients with thyroid nodules nd differentited thyroid cncer. Thyroid 2009;19: Bozgeyik Z, Coskun S, Dgli AF, Ozkn Y, Shpz F, Ogur E. Diffusion-weighted MR imging of thyroid nodules. Neurordiology 2009;51: King AD, Yeung DK, Ahuj AT, Tse GM, Chn AB, Lm SS, et l. In vivo 1H MR spectroscopy of thyroid crcinom. Eur J Rdiol 2005;54: Indin Journl of Endocrinology nd Metolism / My-Jun 2012 / Vol 16 Issue 3 375

6 [Downloded free from on Wednesdy, Septemer 28, 2016, IP: ] Chudhry nd Bno: Thyroid imging 24. Zhou C, Wng Y, Aguirre AD, Tsi TH, Cohen DW, Connolly JL. Ex vivo imging of humn thyroid pthology using integrted opticl coherence tomogrphy nd opticl coherence microscopy. J Biomed Opt 2010;15: Pntnowitz L, Hsiung PL, Ko TH, Schneider K, Herz PR, Fujimoto JG, et l. High-resolution imging of the thyroid glnd using opticl coherence tomogrphy. Hed Neck 2004;26: Cite this rticle s: Chudhry V, Bno S. Imging of the thyroid: Recent dvnces. Indin J Endocr Met 2012;16: Source of Support: Nil, Conflict of Interest: Nil. Author Help: Reference checking fcility The mnuscript system ( llows the uthors to check nd verify the ccurcy nd style of references. The tool checks the references with PuMed s per predefined style. Authors re encourged to use this fcility, efore sumitting rticles to the journl. The style s well s iliogrphic elements should e 100% ccurte, to help get the references verified from the system. Even single spelling error or ddition of issue numer/month of puliction will led to n error when verifying the reference. Exmple of correct style Shehn P, O lery G, Lee G, Fitzgion J. Cystic cervicl metstses: Incidence nd dignosis using fine needle spirtion iopsy. Otolryngol Hed Neck Surg 2002;127: Only the references from journls indexed in PuMed will e checked. Enter ech reference in new line, without seril numer. Add up to mximum of 15 references t time. If the reference is correct for its iliogrphic elements nd punctutions, it will e shown s CORRECT nd link to the correct rticle in PuMed will e given. If ny of the iliogrphic elements re missing, incorrect or extr (such s issue numer), it will e shown s INCORRECT nd link to possile rticles in PuMed will e given. 376 Indin Journl of Endocrinology nd Metolism / My-Jun 2012 / Vol 16 Issue 3