核醫(yī)學(xué)教學(xué)課件：08-甲狀腺顯像

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 p

2、artClassification and principle of thyroid imagingThe Classification of thyroid imagingThyroid static imagingThyroid dynamic imagingPrinciple of static thyroid imagingAdministrating an agent(131I-NaI or 99mTcO4- ) which can be trapped and accumulated selectively by thyroid when entering the body of

3、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 imagingiv administration imging a

4、gent( 99mTcO4-) flow with blood in vein to heart to artery system to thyroidal artery to thyroidDetecting 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 blood-flow(speed and amount), reflect

5、ing the function of thyroidThe second partImaging agents and their futrers, imaging methodsImaging agents and their characteristicsIodine-131(131I): Long physical half-life(8.04d)-rays occupy 90%,r-rays only occupy 10% of its emissionThe energy of principal r-ray is high(364 Kev)A relatively high ir

6、radiation dose to the thyroid and whole-body Easily obtained and with lower costMainly be used for detecting ectopic thyroid tissue and metastasis of thyroid carcinomaThe scanning must be performed at least 24h after oral 131I Iodine-123(123I):It decays by electron capture with a r-photon (energy is

7、 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 thyroid and whole-bodyDisadvantage is

8、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 imaging99mTcO4-iv(as bolus)185-370MBq(5-10mci)i

9、mmidiately 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 as site,morphology,size and functi

10、on 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 the same time with intravenous

11、 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 imagingThe third partNormal and a

12、bnormal 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 normal size: the mean

13、 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 ,could be s

14、een 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, ev

15、en in the pelvis(Fig8).(4) The abnormal of distributionThe radioactivity was diffuse increased in the whole thyroid (seen in hyperthyroid).Fig9.The radioactivity was diffuse decreased in the whole thyroid(seen in hypothyroid or thyroiditis).Fig10.The radioactivity was focally increased or decreased

16、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 u

18、niform.Fig4. Normal dynamic imaging of thyroidThe 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 radioactivi

19、ty is decreased, 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 o

20、r malignant 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 diffu

21、se increased hyperthyroid ( 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)Ectopic thyroid which is a congenital abnormality ,may be found in the base of tongue, sublin

22、gual, substernal, even in the pelvis.If 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 t

23、he thyroid nodule hot nodulewarm nodulecool and cold noduleAppearance: the radioactivity was focally increased comparing with the surrounding thyroid tissue.Clinical significance :almost all hot nodules are toward benign disease(such as autonomous hyperfunctioning adenomal,focal thincken,one lobe co

24、mpensatory),the incidence of malignant 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

25、malignant is about 4-5%.(3).Cool or cold 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,h

26、emorrhage,etc) Type of noduleCommon diseasesmalignantHot 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 tiss

27、ue) thyroid tumors with functions normal , Nodular goiter , 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% (S

28、olitary nodule) Tab 2. Identification of the function and property of 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

29、with 99mTc .B:imaging with 99mTc -MIBIABCDCase 2. C:imaging with 201Tl .D:imaging 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).AB6.Evaluation the weight of thyroid It is necessary to evaluate the weight of thyroid in patients preparing to accept 131I therapy. Usually calc