Paras P, Hamilton D R, Evans C, Herrera N E, Lagunas-Solar M C
Int J Nucl Med Biol. 1983;10(2-3):111-5. doi: 10.1016/0047-0740(83)90010-4.
Iodine-123 (123I), an accelerator-produced radionuclide, gained wide acceptance recently in medical applications. Radionuclide dose calibrators are commonly used to assay radioactivities of radiopharmaceuticals, and should be maintained to read within +/- 5%, both for constancy and accuracy. Radionuclidic impurities present in commercial 123I preparations may produce an assay error larger than 10%. The type and quantity of impurities depend on the mode of production of 123I. The impurities can be reduced by either increasing the energy of the proton beam (over 60 MeV) and using the 127I (p,5n) 133Xe leads to 123I indirect reaction or using lower energies and highly enriched (better than 99%) 124Te (or 122Te) target for the direct production of 123I via 124Te (p, 2n) 123I or 122Te (d, n) 123I. A survey of radionuclide calibrators was undertaken to investigate the extent of the 123I assay error due to impurities present in commercially available preparations of 123I. Results from 24 calibrators indicate that the activity of a (p, 2n) 123I capsule is overestimated on average by 22% two half-lives after calibration time, while the activity of a (p, 5n) 123I capsule remains within the accuracy of the radionuclide calibrator of +/- 5%. The 124I fraction increases significantly with time during the useful life of a (p, 2n) 123I capsule introducing large 123I assay errors.
碘-123（¹²³I）是一种由加速器产生的放射性核素，最近在医学应用中得到了广泛认可。放射性核素剂量校准器通常用于测定放射性药物的放射性，并且为了保证稳定性和准确性，其读数应保持在±5%以内。市售¹²³I制剂中存在的放射性核素杂质可能会产生大于10%的测定误差。杂质的类型和数量取决于¹²³I的生产方式。通过提高质子束能量（超过60 MeV）并使用¹²⁷I（p，5n）¹³³Xe生成¹²³I的间接反应，或者使用较低能量和高富集度（优于99%）的¹²⁴Te（或¹²²Te）靶材通过¹²⁴Te（p，2n）¹²³I或¹²²Te（d，n）¹²³I直接生产¹²³I，可以减少杂质。对放射性核素校准器进行了一项调查，以研究市售¹²³I制剂中存在的杂质导致的¹²³I测定误差程度。24台校准器的结果表明，在校准时间后的两个半衰期，（p，2n）¹²³I胶囊的活度平均被高估22%，而（p，5n）¹²³I胶囊的活度仍在放射性核素校准器±5%的精度范围内。在（p，2n）¹²³I胶囊的使用寿命期间，¹²⁴I的比例会随着时间显著增加，从而导致较大的¹²³I测定误差。
