Ravichandran R, Binukumar Jp, Saadi Amal Al
Medical Physics Unit, National Oncology Center, Royal Hospital, Muscat-111, Oman.
Indian J Nucl Med. 2010 Apr;25(2):49-52. doi: 10.4103/0972-3919.72686.
In medical applications of radioisotopes, for calculations of whole body doses and radiation safety applications, there is a need to estimate radioactive body burden. Local recommendations in Oman stipulate the need for hospitalization of patients treated for radioactive-iodine ((131) I) with activities above 400 MBq. MATERIALS #ENTITYSTARTX00026;
A study of body burden estimation from sequentially measured exposure rates from patients treated for carcinoma thyroid and hyperthyroidism was undertaken. A digital auto-ranging beta gamma survey instrument calibrated for measurement of exposure rates is used in this study.
The mean measured exposure rates at 1 m in μSv/h immediately after administration and at 24 h intervals are used for estimation of effective half time of clearance of administered activity. For patients with post-operative thyroid carcinoma, the variation of body burden with time post-administration indicated tri-exponential clearance pattern, with T(½eff) values 14.4 h, 22 h, and 41.3 h. For patients treated for thyrotoxicosis, the body burden showed slow delayed clearance with a T(½eff) - 111.4 h, and exposure rates did not show appreciable fall off after 48 h.
在放射性同位素的医学应用中，为了计算全身剂量和进行辐射安全应用，需要估计体内放射性负荷。阿曼的当地建议规定，接受放射性碘（（131）I）治疗且活度超过400 MBq的患者需要住院治疗。
对接受甲状腺癌和甲状腺功能亢进治疗的患者依次测量的暴露率进行体内负荷估计研究。本研究使用了一台经过校准用于测量暴露率的数字自动量程βγ测量仪。
给药后立即及每隔24小时在1米处测量的平均暴露率（单位为μSv/h）用于估计给药活度的有效清除半衰期。对于术后甲状腺癌患者，给药后体内负荷随时间的变化呈现三指数清除模式，有效半衰期（T(½eff)）值分别为14.4小时、22小时和41.3小时。对于接受甲状腺毒症治疗的患者，体内负荷显示出缓慢的延迟清除，有效半衰期（T(½eff)）为111.4小时，且48小时后暴露率没有明显下降。
