1、 Thyroid Imaging Duan DongDepartment of Nuclear MedicineThe First Affiliated Hospital of Chongqing Medical UniversityClassification and principle of thyroid imagingImaging agents and their features,imaging methodsNormal and abnormal imaging Clinical application of thyroid imagingContentsThe first pa
2、rtClassification and principle of thyroid imagingThe Classification of thyroid imagingThe Classification of thyroid imagingThyroid static imagingThyroid dynamic imagingPrinciple of static thyroid imaging Administrating an agent(131I-NaI or 99mTcO4-)which can be trapped and accumulated selectively by
3、 thyroid when entering the body of patients.Certain time after administration,Detecting the r-ray emitted by radionuclides in the thyroid with certain nuclear device,then we can obtain the image of thyroid(site,morphology,size,function).Trapped by thyroid131I or 99mTcrrrrPrinciple of dynamic thyroid
4、 imaging iv administration imging agent(99mTcO4-)flow with blood in vein to heart to artery system to thyroidal artery to thyroid Detecting the r-ray emitted by radionuclides and acquire the images continually with certain nuclear device.By these images we can obtain the information of thyroids bloo
5、d-flow(speed and amount),reflecting the function of thyroidThe second partImaging agents and their futrers,imaging methodsImaging agents and their characteristicsIodine-131(131I):v Long physical half-life(8.04d)v-rays occupy 90%,r-rays only occupy 10%of its emissionv The energy of principal r-ray is
6、 high(364 Kev)v A relatively high irradiation dose to the thyroid and whole-body v Easily obtained and with lower costv Mainly be used for detecting ectopic thyroid tissue and metastasis of thyroid carcinomav The scanning must be performed at least 24h after oral 131I Iodine-123(123I):It decays by e
7、lectron capture with a r-photon(energy is 159 Kev,which is very suitable for imaging).Physical half-life is 13.27hHigh cost(produced by cyclotron)Technetium 99m(99mTc)It decays by pure r-rays(energy is 140 Kev)Short Physical half-life(6.02h)Easily obtained and lower costLower irradiation dose to the
8、 thyroid and whole-bodyDisadvantage is its non-specificity Methods of imaging1).Asking the disease history and palpating the thyroid of patients before the examination.2).Administration of radiopharmaceuticals(or imaging agents)agentsthe route of administrationThe dose of agentsthe time of imaging99
9、mTcO4-iv(as bolus)185-370MBq(5-10mci)immidiately or20-30min131I-NaIoral1.85-3.7MBq(50-100uci)or74-148MBq(2-3mci)24-72hTable 1 Comparision of two agents Static imaging is begin at certain time(30min or 24h）after administration of imaging agents.From these images,mainly obtaining the information such
10、as site,morphology,size and function of thyroid(fig 1).Fig1.Static imaging of thyroid 3).The acquisition of images.Sometimes tomographic imaging or SPET/CT images fusion is necessary to identify suspicious focus shown in planar imaging.3).The acquisition of images.Dynamic thyroid imaging is begin at
11、 the same time with intravenous administration,and acquire the images continually,2s per frame,sum to 20 frames.(Fig.2)Fig2.Dynamic imaging of thyroid Supine,neck extended,and detecting in anterior，sometimes in left or right anterior oblique posture.4).The posture of imagingFig3.posture of imagingTh
12、e third partNormal and abnormal imaging present1)The normal site of thyroid image is in the middle of neck.1.Normal static imaging(Fig 5)2)Its shape like a butterfly(have two lobes,which usually were joined by the isthmus).and sometimes the pyramidal lobe can be found in some normal people.3）The nor
13、mal size:the mean height is 4.5cm,width is 2.5cm of two lobes.4）The distribution of imaging agents should be uniform.5）If imaging agent is 99mTc,the images of salivary gland and mucosa of mouth,nasopharynx,usually can be seen.2.Abnormal Static images(1)abnormal of morphology:irregular or incomplete,
14、could be seen in multinodular goiter and congenital absence of one lobe(Fig6).(2)The abnormal of size:usually enlarge,be seen in hyperthyroid and multinodular goiter(Fig7).(3)The abnormal of site:seen in ectopic thyroid,the image of thyroid may occur in the base of tongue,or sublingual,or substernal
15、,even in the pelvis(Fig8).(4)The abnormal of distributionvThe radioactivity was diffuse increased in the whole thyroid(seen in hyperthyroid).Fig9.vThe radioactivity was diffuse decreased in the whole thyroid(seen in hypothyroid or thyroiditis).Fig10.vThe radioactivity was focally increased or decrea
16、sed in the thyroid(seen in thyroid nodules),we define it by the relative amount of radioactivity present as follows:Hot nodule:higher than normal tissue(Fig11)cool or cold nodule:lower than normal tissue or no(Fig12)warm nodule:equal to normal tissue(Fig13)3.Normal dynamic imaging(Fig4.)8-12s after
17、intravenous administration,the images of bilateral carotid artery can be seen,then 2-6s after this the image of thyroid is shown,and later,which gradually strengthen and can be seen clearly.The mean pass time from carotid artery to thyroid is 2.5-7.5s.The distribution of agents in thyroid is uniform
18、.Fig4.Normal dynamic imaging of thyroid The image of thyroid is shown early and the radioactivity is increased,which indicate that the blood-flow or the function of thyroid is increased,usually seen in GD.(Fig14)If the pass time from carotid artery to thyroid is prolonged and the radioactivity is de
19、creased,which indicate the blood-flow or the function of thyroid is decreased,usually seen in hypothyroid.(Figi5)To a nodule in thyroid,if its radioactivity is higher or its image is shown earlier than the normal part,it indicates that the nodule may be autonomous hyperfunction adenoma or malignant
20、disease.And on conversely,may be benign disease.(Fig16,17,18)4.Abnormal dynamic imagingThe fouth partClinical application of thyrod imaging Clinical application 1.Evaluation the function of thyroid(Fig19,20)Table2.Comparision of two disease dynamic static pass time is shorten diffuse increased hyper
21、thyroid (the blood-flow is of activity increased)hypothyroid pass time is prolonged diffuse decreased (the blood-flow is of activity decreased)2.Diagnosing of ectopic thyroid(with 131I)vEctopic thyroid which is a congenital abnormality,may be found in the base of tongue,sublingual,substernal,even in
22、 the pelvis.vIf there is no image of thyroid in the normal site,and a tissue which can uptake 131I was found in other site,we can diagnose.(Fig21.)Fig21.Ectopic thyroid(A:Sublingual thyroid,B:Substernal thyroid goiter)AB3.Identification of the function and property of the thyroid nodule hot nodulewa
23、rm nodulecool and cold nodulevAppearance:the radioactivity was focally increased comparing with the surrounding thyroid tissue.vClinical significance:almost all hot nodules are toward benign disease(such as autonomous hyperfunctioning adenomal,focal thincken,one lobe compensatory),the incidence of m
24、alignant is less than 1%.(1)Hot nodule:(2).Warm nodule Appearance:The relative amount of radioactivity in nodule is equal to surrounding thyroid tissue.Clinical significance:maybe:thyroid tumors with functions normal,Nodular goiter,ThyroiditisThe incidence of malignant is about 4-5%.(3).Cool or cold
25、 noduleAppearance:The relative amount of radioactivity in nodule is less or no compared with the normal thyroid tissue.Clinical significance:The incidence of malignant is about 10-20%(especially solitary nodule).Other possibility are benign diseases(cyst,hemorrhage,etc)Type of noduleCommon diseasesm
26、alignantHot nodule (focally increased of radioactivity)Autonomous hyperfunctioning adenoma(Plummer disease),Congenital absence of compensatory function of leaf 1%Warm nodule (the radioactivity of nodule is equal to the surrounding normal thyroid tissue)thyroid tumors with functions normal,Nodular go
27、iter,Thyroiditis4%5%Cool noduleCold nodule (focally decreased of activity or no radioactivity)Thyroid cyst,Cystic thyroid tumors,Most thyroid cancer,Chronic lymphocytic thyroiditis,Bleeding or calcification in thyroid nodules10%-20%(Solitary nodule)Tab 2.Identification of the function and property o
28、f the thyroid nodule4.Identifying the property of thyroid cool or cold nodule(1).Applying tumor-locating imaging agents(such as 67Ga,201Tl,99mTc-MIBI,99mTc-DMSA).(2)Static imaging combining with dynamic imagingCase 1.A:imaging with 99mTc.B:imaging with 99mTc-MIBIABCDCase 2.C:imaging with 201Tl.D:ima
29、ging with 99mTc5.Identifying the cervical mass If the mass can uptake agents or the morphology of thyroid is incomplete,or the distribution of agents in thyroid is not uniform,it indicates the mass may come from or be correlated with thyroid(A).On conversely,the mass is not correlated with thyroid(B
30、).AB6.Evaluation the weight of thyroid It is necessary to evaluate the weight of thyroid in patients preparing to accept 131I therapy.Usually calculate the weight of the thyroid as the follow formula:W=SHK W(g):weight of thyroid S(cm2):superficies of thyroid H(cm):mean height of thyroid bi-lobes K:a
31、 coefficient,usually vary in 0.23-0.32 7.Auxiliary diagnosis of subacute thyroiditisearly stage:foccally or diffuse dicreased of radioactivity in throidRAIU T3 T4 seperate phenomenarecovery stage:radioactivity gradually return to normal8.Detecting the metastases of thyroid carcinoma(131I)v80%of thyr
32、oid cancers are well differentiated(such as papillary,follicular)and have the ability to concentrate radioiodine,and their metastases can also concentrate radioiodine.vThis examination usually was performed after total or subtotal thyroidectomy subsequent with 131I ablation.Fig23.Diffuse pulmonary metastases come from thyroid carcinoma(A:Chest radiograph,B:Whole-body scan with 131I imaging).A BFig24.Metastases of thyroid carcinoma(A:to lung and cervical lymph nodes.B:to cervical lymph nodes).A B
