核医学 甲状腺显像

3）The normal 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 ,could be seen in multinodular goiter and congenital absence of one lobe(Fig6).
can obtain the image of thyroid(site,morphology,size,function).
r
r
r
131I or
99mTc
r
Trapped by thyroid
Principle of dynamic thyroid imaging
• iv administration imging agent( 99mTcO4-) in vein to heart to artery system
3. Normal dynamic imaging(Fig4.)
8-12s 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 thyroid is uniform.
Thyroid Imaging
Duan Dong
Department of Nuclear Medicine The First Affiliated Hospital of Chongqing Medical University
Contents
➢Classification and principle of thyroid imaging ➢Imaging agents and their features, imaging methods ➢Normal and abnormal imaging ➢Clinical application of thyroid imaging
(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 in the pelvis(Fig8).
Methods of imaging
1).Asking the disease history and palpating the thyroid of patients before the examination.
2). Administration of radiopharmaceuticals(or imaging agents)
Fig3. posture of imaging
The third part
Normal and abnormal imaging present
1. Normal static imaging(Fig 5)
1) The normal site of thyroid image is in the middle of neck.
Fig2.Dynamic imaging of thyroid
4).The posture of imaging
Supine , neck extended, and detecting in anterior， sometimes in left or right anterior oblique posture.
159 Kev, which is 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 unspecific
Table 1 Comparision of two agents
agents 99mTcO4131I-NaI
the route of administrati on
The dose of agents the time of imaging
iv(as bolus) 185-370MBq(5-10mci) immidiately or
Sometimes tomographic imaging or SPET/CT images fusion is necessary to identify suspicious focus shown in planar imaging.
Fig1.Static imaging of thyroid
The first part
Classification and principle of thyroid imaging
The Classification of thyroid imaging
①Thyroid static imaging
②Thyroid dynamic imaging
Principle of static thyroid imaging
(4) The abnormal of distribution
❖The 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.
• 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 the r-ray emitted by radionuclides in the thyroid with certain nuclear device,then we
❖The radioactivity was focally increased or decreased 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)
20-30min
oral
1.85-3.7MBq(50-100uci) 24-72h
or
74-148MBq(2-3mci)
3).The acquisition of images.
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 1).
The second part
Imaging agents and their futrers, imaging methods
Imaging agents and their characteristics
Iodine-131(131I):
❖ Long physical half-life(8.04d) ❖ β-rays occupy 90%,r-rays only occupy 10% of its emission ❖ The energy of principal r-ray is high(364 Kev) ❖ A relatively high irradiation dose to the thyroid and whole-body ❖ Easily obtained and with lower cost ❖ Mainly be used for detecting ectopic thyroid tissue and
2) It’s 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 acquisition of images.
➢Dynamic thyroid imaging is begin at the same time with intravenous administration ,and acquire the images continually ,2s per frame ,sum to 20 frames.(Fig.2)
artery
to thyroid
flow with blood to ted by radionuclides and acquire the images continually with certain nuclear device. By these images we can obtain the information of thyroid’s bloodflow(speed and amount), reflecting the function of thyroid
metastasis of thyroid carcinoma ❖ 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