A radioisotope (RI) or its labeled compound is administered into the body as a tracer to the organ or tissue of interest, and its radioactivity is measured from outside the body to record the distribution on film or paper. This examination method is called scintigraphy or scintiscan. A scintigraphy scanner (also called a rectilinear scanner) or a scintigraphy camera is used to record the scintigram. In a scintigram, areas where the radioisotope is concentrated appear dark (positive image). Areas in an organ that has taken up the isotope but has not taken up the isotope appear white (negative image). When gallium citrate ( 67 Ga), which has an affinity for cancer, is used, a positive image is often obtained. Therefore, the position, size, shape, internal structure, and presence or absence of cancer of various organs can be determined from the findings of the scintigram. A scintigraphy camera can perform examinations in a shorter time than a scintigraphy scanner, and changes in the image over time can also be observed. Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information |
検査の目的とする臓器,組織に適切な放射性同位元素 (RI) あるいはその標識化合物をトレーサーとして体内に投与し,その放射能を体外から測定して分布状態をフィルムあるいは紙上に記録した画像をいう。この検査法をシンチグラフィーまたはシンチスキャンと呼ぶ。シンチグラムを記録するための装置は,シンチスキャナ (レクティリニア・スキャナともいう) やシンチカメラが用いられる。シンチグラムでは,放射性同位元素が濃縮した部位は濃く写る (陽性像) 。同位元素を取込んだ臓器内にそれを取込まない部位があると,白く抜けて写る (陰性像) 。なお,癌に親和性がある 67Ga (クエン酸ガリウム) などを用いると,陽性像を示すことが多い。したがって,シンチグラムの所見から,各種臓器の位置,大きさ,形,内部構造,癌の有無などを知ることができる。シンチスキャナよりもシンチカメラのほうが短時間で検査でき,経時的な像の変化も観察できる。
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