Deloar H M, Watabe H, Nakamura T, Narita Y, Yamadera A, Fujiwara T, Itoh M
Cyclotron and Radioisotope Center, Tohoku University, Aramaki, Japan.
J Nucl Med. 1997 Oct;38(10):1603-13.
In the steady state method, 15O-labeled gases (C15O2, 15O2 and C15O) are administered to the body by continuous inhalation in various clinical PET studies. During inhalation, the nasal cavity and major airway may obtain a substantial amount of dose, being the source organs as well as the target organs. The internal absorbed dose to those organs and their contribution to the other target organs have not been calculated by the MIRD method. To calculate the internal dose in the MIRD method, the S values, the absorbed doses per unit of cumulated activities from nasal cavity and major airway to the other organs and vice versa, are needed, and these values are not available.
In this study, we introduced a mathematical model of the nasal cavity and major airway to calculate their S values to 23 target organs and from 11 source organs to them. Individual experiments were performed to measure the total uptake percentage and body surface doses of 15O-labeled gases from continuous inhalation.
Using the body surface doses measured by thermoluminescent dosimeters, the cumulated activities of 11 source organs were estimated with the mathematical transformation method, and then the internal absorbed doses in 23 target organs were calculated by the MIRD method. Our experimental results were compared with the other results, and good agreements were observed.
Among the target organs, the critical organ is the airway, and the absorbed dose is 2.57 x 10(-2) mGy.MBq-1.
在稳态法中，在各种临床正电子发射断层扫描（PET）研究中，通过持续吸入将15O标记的气体（C15O2、15O2和C15O）施用于人体。在吸入过程中，鼻腔和主要气道可能会获得大量剂量，既是源器官也是靶器官。尚未通过医学内照射剂量（MIRD）方法计算这些器官的内吸收剂量及其对其他靶器官的贡献。为了用MIRD方法计算内剂量，需要S值，即从鼻腔和主要气道到其他器官以及反之从其他器官到鼻腔和主要气道的每单位累积活度的吸收剂量，而这些值无法获得。
在本研究中，我们引入了鼻腔和主要气道的数学模型，以计算它们到23个靶器官以及从11个源器官到它们的S值。进行了单独实验，以测量持续吸入15O标记气体的总摄取百分比和体表剂量。
使用热释光剂量计测量的体表剂量，通过数学变换方法估算了11个源器官的累积活度，然后用MIRD方法计算了23个靶器官的内吸收剂量。我们的实验结果与其他结果进行了比较，观察到了良好的一致性。
在靶器官中，关键器官是气道，吸收剂量为2.57×10(-2) mGy·MBq-1。
