Votaw J R, Ansari M S, Mason N S, Schmidt D, de Paulis T, Holburn G, Clanton J A, Votaw D B, Manning R G, Kessler R M
Department of Radiology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
J Nucl Med. 1995 Jul;36(7):1316-21.
Substituted benzamides have been shown to have very high affinity and specificity for the dopamine D2 receptor. One of these is radiolabeled epidepride, an iodine-substituted benzamide currently under evaluation as a SPECT imaging agent. Detailed estimates of the radiation absorbed dose to 26 organs and the whole body from [123I]epidepride have been calculated.
The dosimetry calculations use a combination of in vivo uptake and biodistribution data from one rhesus monkey and seven humans to estimate residence times in eight organs. The computer program MIRDOSE2 was used to calculate the dosimetry.
Results indicate that 75% of the radioactivity is cleared through the urinary tract while the remaining radioactivity clears through the gallbladder and intestinal tract. The radiation absorbed dose can be minimized by administering a high lipid content meal 1.5 hr postinjection to empty the gallbladder and by giving large volumes of fluids throughout the study to induce increased urinary output.
By emptying the gallbladder and urinary bladder, the lower large intestine becomes the critical organ, 0.102 mGy/MBq (0.38 rad/mCi) followed by the upper large intestine, 0.092 mGy/MBq (0.34 rad/mCi). The effective dose equivalent is 0.025 mSv/MBq (0.092 rem/mCi).
已证明取代苯甲酰胺对多巴胺D2受体具有非常高的亲和力和特异性。其中一种是放射性标记的表哌立得，一种碘取代的苯甲酰胺，目前正在作为单光子发射计算机断层扫描（SPECT）成像剂进行评估。已计算出[123I]表哌立得对26个器官和全身的辐射吸收剂量的详细估计值。
剂量学计算结合了一只恒河猴和七名人类的体内摄取和生物分布数据，以估计八个器官中的停留时间。使用计算机程序MIRDOSE2进行剂量学计算。
结果表明，75%的放射性通过尿路清除，其余放射性通过胆囊和肠道清除。通过在注射后1.5小时给予高脂餐以排空胆囊，并在整个研究过程中给予大量液体以增加尿量，可以使辐射吸收剂量最小化。
通过排空胆囊和膀胱，降结肠成为关键器官，辐射吸收剂量为0.102 mGy/MBq（0.38 rad/mCi），其次是升结肠，为0.092 mGy/MBq（0.34 rad/mCi）。有效剂量当量为0.025 mSv/MBq（0.092 rem/mCi）。
