Nusynowitz M L
University of Texas Medical Branch, Galveston 77555-0793, USA.
Lippincotts Prim Care Pract. 1999 Nov-Dec;3(6):546-55; quiz 556-8.
Four modalities are being used to image the thyroid gland: (1) scintigraphy ("scanning"), employing one of several currently available radiopharmaceuticals, (2) ultrasound (US), (3) computed tomography (CT, "CAT" scan), and (4) magnetic resonance imaging (MRI). The first method, scintigraphy, provides an image of the spatial distribution of thyroid functional attributes, the nature of which are dependent on the interaction between the particular radiopharmaceutical employed and the tissue in question, whereas the latter three modalities provide an image of the spatial distribution of structural attributes such as the varying degrees of echogenicity of the tissues examined or the differential tissue attenuation of an x-ray beam, which permits visualization of the structures. A fifth modality, fluorescent thyroid scanning, in which fluorescence of the iodide within the thyroid gland is induced by low-dose external radiation and which gives an image of iodine distribution, is generally unavailable and only rarely used. For most patients, the combination of careful history, skilled physical examination, tests of thyroid function (and serum thyroglobulin and calcitonin for cancer evaluation), fine needle aspiration biopsy, and scintigraphy provide the most cost-effective means of evaluating the thyroid gland and its diseases. Of the four modalities currently used to image the thyroid gland--scintigraphy, ultrasound, computerized tomography, and magnetic resonance imaging--only scintigraphy has the widest application. It is employed to determine gland size, locate thyroid tissue, evaluate nodules and masses, determine the cause of a painful tender gland, differentiate various forms of goiter, detect differentiated thyroid carcinoma and gland remnants, assess suppressibility or stimulatability of the gland, and identify nonfunctioning cancers. Ultrasonography, computed tomography, and magnetic resonance imaging are not useful in differentiating between benign and malignant nodules, and their sensitivity in detecting impalpable nodules is not clinically useful, because nodules less than 1 to 1.5 cm in diameter are only rarely clinically significant. These modalities have limited utility in the evaluation of the thyroid gland: they are useful in sizing known lesions and for the detection of cervical lymphadenopathy in thyroid cancer cases.
（1）闪烁扫描法（“扫描”），使用几种现有的放射性药物之一；（2）超声（US）；（3）计算机断层扫描（CT，“CAT”扫描）；以及（4）磁共振成像（MRI）。第一种方法，即闪烁扫描法，可提供甲状腺功能属性的空间分布图像，其性质取决于所使用的特定放射性药物与相关组织之间的相互作用，而后三种方式则提供结构属性的空间分布图像，例如所检查组织不同程度的回声性或X线束的组织衰减差异，从而使结构得以可视化。第五种方式，荧光甲状腺扫描，通过低剂量外部辐射诱导甲状腺内碘化物的荧光并给出碘分布图像，一般无法使用且很少被采用。对于大多数患者而言，详细的病史、熟练的体格检查、甲状腺功能测试（以及用于癌症评估的血清甲状腺球蛋白和降钙素）、细针穿刺活检以及闪烁扫描法相结合，提供了评估甲状腺及其疾病最具成本效益的方法。在目前用于甲状腺成像的四种方式——闪烁扫描法、超声、计算机断层扫描和磁共振成像——中，只有闪烁扫描法应用最为广泛。它用于确定腺体大小、定位甲状腺组织、评估结节和肿块、确定疼痛性压痛腺体的病因、区分各种形式的甲状腺肿、检测分化型甲状腺癌和腺体残余、评估腺体的可抑制性或可刺激性以及识别无功能的癌症。超声检查、计算机断层扫描和磁共振成像在区分良性和恶性结节方面并无用处，并且它们在检测不可触及结节方面的敏感性在临床上并无实际用途，因为直径小于1至1.5厘米的结节临床上很少具有重要意义。这些方式在甲状腺评估中的作用有限：它们在测量已知病变大小以及检测甲状腺癌病例中的颈部淋巴结病方面有用。
