前言:[氟-18]去氧葡萄糖是正電子斷層攝影中最常用的核醫藥物之一，其代謝路徑終點為膀胱，而膀胱是所有器官當中累積最高劑量者。本研究之目的即是發展一精確的動態膀胱假體，使之能有效地評估膀胱劑量累積情形，供臨床給藥時之參考。
材料與方法:本研究之膀胱假體是針對人體膀胱的生理特性而設計，假體內部以水填充，將表面貼有TLD的氣球置入假體內，再以不同流速將適當濃度的18F-FDG徐徐注入。該假體可同時評估影響膀胱吸收劑量之各項因子，主要為：尿液活性濃度、尿液產生速率、排尿次數與時間、注射藥物前起始尿液的體積、殘餘尿液體積等。本研究也利用加馬光子劑量轉換的觀念，發展出計算膀胱吸收劑量之數學計算模式，此模式可方便地運用於臨床計算上。
結果與討論:本研究採用熱發光劑量計來評估膀胱吸收劑量情形，證明為一可行的方法。經由數學計算模式所求得之膀胱吸收劑量，與實際所量測之結果加以比較，發現偏差皆在5%之滿意度內。本計算模式所具有之吸收劑量預測功能，對臨床評估十分方便。
結論:雖然本動態膀胱假體能有效評估吸收劑量，惟仍無法有效模擬人體膀胱動態變化情形。為克服不同核醫藥物在體內有不同代謝分佈問題，本研究將在未來利用正電予斷層影像的資訊，取得膀胱內尿液活性與時間的關係，進而運用本劑量模式，發展一套可供臨床應用計算的方法。因為本研究建立在膀胱假體的基礎上，對於具有相同核種之核醫藥物，本劑量計算模式應可一併適用。

Background: The use of 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) in conjunction with positron emission tomography (PET) has been widely used for years in nuclear medicine. The highest radiation dose received by the human organ from the use of the radiotracer is the bladder wall, which approximates 20% of the total injected dose. The purposes of this study are to propose a dynamic urinary bladder phantom, which can effectively estimate the cumulated absorbed dose of the bladder and to develop a mathematical model for bladder wall absorbed dose evaluation.
Material and Methods: A dynamic bladder phantom was proposed according to the physiological features of the human bladder. The phantom was filled with water, and ten TLD disks are roundly attached to the wall of a balloon, which simulates a dynamic bladder, for dose measurement. The 18F-FDG with various concentrations can be either IV drip-feed into or sucked-out from the balloon bladder. In the study, five major factors affecting the absorbed dose evaluation are critically examined respectively, and they are the concentration of 18F-FDG in urine, the urine production rate, the frequency and duration of urine voiding, the initial urine volume and the residual urine volume. The TLD-photon absorbed dose conversion factor was considered to develop a bladder dose calculation model as it can be applied in the clinical study.
Results and Discussion: It was shown that the phantom can evaluate the bladder absorbed dose effectively. The calculated results showed deviations less than 5% from experimental data, and considered as satisfactorily accept- able. The proposed model proved to be a convenient and unique way to estimate the clinical bladder absorbed dose.
Conclusion: Although the phantom has potential in evaluating the bladder doses, it is not an optimal simulation to the dynamic human bladder. To overcome the different biodistributions among radiopharmaceuticals, the time-activi-ty relationship of the bladder urine taken from the PET imaging will be the next goal of the study. With the development, the proposed model would be more applicable to the bladder wall dose evaluation clinically.