核医学课件：4甲状腺显像

1、 Thyroid Imaging Classification and principle of thyroid imaging Imaging agents and their features, imaging methods Normal and abnormal imaging Clinical application of thyroid imaging Contents The first part Classification and principle of thyroid imaging The Classification of thyroid imagingThe Cla

2、ssification of thyroid imaging Thyroid static imagingThyroid dynamic imaging Principle of static thyroid imaging Administrating an agent(131I-NaI or 99mTcO4- ) which can be trapped and accumulated selectively by thyroid when entering the body of patients. Certain time after administration, Detecting

3、 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 thyroid 131I or 99mTc r r r r Principle of dynamic thyroid imaging iv administration imging agent( 99mTcO4-) flow with blood in vein to he

4、art 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 blood- flow(speed and amount), reflecting the function of thyroid The second part

5、 Imaging agents and their futrers, imaging methods Imaging agents and their characteristics Iodine-131(131I): v Long physical half-life(8.04d) v -rays occupy 90%,r-rays only occupy 10% of its emission v The energy of principal r-ray is high(364 Kev) v A relatively high irradiation dose to the thyroi

6、d and whole-body v Easily obtained and with lower cost v Mainly be used for detecting ectopic thyroid tissue and metastasis of thyroid carcinoma v The scanning must be performed at least 24h after oral 131I Iodine-123(123I): It decays by electron capture with a r-photon (energy is 159 Kev, which is

7、very suitable for imaging). Physical half-life is 13.27h High 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 cost Lower irradiation dose to the thyroid and whole-body Disadvantage is its unspecif

8、ic Methods of imaging 1).Asking the disease history and palpating the thyroid of patients before the examination. 2). Administration of radiopharmaceuticals(or imaging agents) agentsthe route of administrati on The dose of agentsthe time of imaging 99mTcO4- iv(as bolus)185-370MBq(5-10mci)immidiately

9、 or 20-30min 131I-NaI oral1.85-3.7MBq(50-100uci) or 74-148MBq(2-3mci) 24-72h Table 1 Comparision of two agents Static imaging is begin at certain time after administration of imaging agents. From these images, mainly obtaining the information such as site,morphology,size and function of thyroid(fig

10、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 administration ,

11、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 imaging Fig3. posture of imaging The third part Normal and abnormal ima

12、ging present 1) 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 height

13、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 seen i

14、n 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, even i

15、n the pelvis(Fig8). (4) The abnormal of distribution vThe 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 decreas

16、ed 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.) 8-12

17、s after 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 thyro

18、id is uniform. 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 r

19、adioactivity 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 hyperfunctio

20、n adenoma or malignant disease. And on conversely, may be benign disease.(Fig16,17,18) 4. Abnormal dynamic imaging The fouth part Clinical application of thyrod imaging Clinical application 1.Evaluation the function of thyroid(Fig19,20) Table2. Comparision of two disease dynamic static pass time is

21、shorten diffuse 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) vEctopic thyroid which is a congenital abnormality ,may be found in the base o

22、f tongue, sublingual, substernal, even in 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) A B 3.Identification of the funct

23、ion and property of the thyroid nodule hot nodule warm nodule cool and cold nodule vAppearance: 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

24、,focal thincken,one lobe compensatory),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 ,

25、 Thyroiditis The incidence of malignant is about 4-5%. (3).Cool or cold nodule Appearance: 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 possi

26、bility are benign diseases(cyst,hemorrhage,etc) Type of noduleCommon diseasesmalignant Hot 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

27、the surrounding normal thyroid tissue) thyroid tumors with functions normal , Nodular goiter , Thyroiditis 4%5% Cool nodule Cold nodule (focally decreased of activity or no radioactivity ) Thyroid cyst , Cystic thyroid tumors , Most thyroid cancer , Chronic lymphocytic thyroiditis , Bleeding or calc

28、ification in thyroid nodules 10%-20% (Solitary nodule) Tab 2. Identification of the function and property of the thyroid nodule 4.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 combin

29、ing with dynamic imaging Case 1. A:imaging with 99mTc .B:imaging with 99mTc -MIBI AB CD Case 2. C:imaging with 201Tl .D:imaging with 99mTc 5.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). A B 6.Evaluation the weight of thyroid It is necessary to evaluate the weight of thyroid in patients preparing to accept 131I therapy. Usual