前言：以衰變公式計算鉈-201的放射活度時常發現計算值偏高，此問題肇因於忽略不純核種，尤其是鉈-200，以及游離腔偵測高能量加馬光子的靈敏度增高的影響。本研究之目的在於引導出－修正函數以修正使用衰變公式計算的鉈-201放射活度，以改善鉈-201氯化亞鉈生產時分裝活度的精確性。材料與方法：來自八批新生產的鉈-201氯化亞鉈樣品以一Capintec CRC-12同位素校正儀量測鉈-201放射活度，並以一配備高純度鍺偵檢器之多頻道脈高分析系統分析各放射核種之放射活度分率。
結果：根據各樣品第一次量測鉈-201放射活度並以衰變公式計算之各時間點放射活度計算值明顯逐漸比實剛值偏高，證實由於鉈-201放射活度的放大影響了第一次鉈-201放射活度的量測值。藉由定義鉈-201對鉈-201相對靈敏度(本研完使用的游離腔導出值為2.752±0.19)，我們導出一修正函數F(fl, f2, t)，以作為衰變公式計算的鉈-201放射活度修正。
結論：使用本研究導出的修正函數及加馬能譜分析獲得的鉈-200及鉈-201之放射活度分率，我們已能精確修正鉈-201放射活度依據衰變公式進行的計算。

Background: 201TI radioactivity calculation are often found to be overestimated. The problem comes from the ignorance of contributions of radionuclidic impurities, particularly from 200TI, and the energy-dependent sensitivity of the ionization chamber to detect the high energy gamma photons emitted from these impure radionuclides. The aim of this study was to derive a modification function for accurate measurement of 201TI radioactivity in production.
Materials and Methods: Eight 201TI -TICI samples from freshly prepared batch were subject to measuring their radioactivity with a Capintec CRC isotope calibrator, and to analyzing their gamma spectra with a HPGe detector equipped MCA system in order to determine the radioactivity fraction for each detected radionuclide.
Results and Discussion: The calculated radioactivities, based on the first time measured radioactivity by the decay equation, at various time periods were compared with radioactivity measured. The results confirmed the overestimation of the first measurement resulting from the exaggerated radioactivity of 200TI impurity. By defining the relative sensitivity of 200TI to 201TI, which was found to be 2.752+0.19 for the ionization chamber used in this study, a modification function, F( fl, f2, t), has been derived.
Conclusion: By usin9 the modification function and radioactivity fractions of 201TI and 201TI, the 201TI radioactivities measured with an ionization chamber could be precisely calculated by the decay equation.