Samuel A M, Rajashekharrao B
Radiation Safety Systems Division, Bhabha Atomic Research Centre, Parel, Bombay, India.
J Nucl Med. 1994 Dec;35(12):1944-50.
The influence of cumulative absorbed dose, initial dose rate and mass of the remnant thyroid tissue on outcome of radioiodine treatment was assessed to determine an optimum value of absorbed dose and initial dose rate predictive of successful ablation.
In 87 patients with thyroid carcinoma treated with 0.85-9.55 GBq (23-258 mCi) of 131I to ablate residual thyroid tissue, the cumulative absorbed dose and the initial dose rate were calculated. Following therapy, the parameters of radioactive iodine uptake and effective half-life were determined in each patient from the surface neck exposure rates measured using a beta/gamma exposure rate meter. Mass of the thyroid remnant was determined from rectilinear images after scatter correction obtained from phantom studies.
Sixty-eight patients showed complete ablation and 19 showed partial ablation of the thyroid remnant after radioiodine therapy. The cumulative absorbed doses delivered to the tissue in completely ablated and partially ablated groups were not significantly different (0.6 > p > 0.5). The initial dose rate delivered to the tissue in both groups, however, showed a significant difference (0.05 > p > 0.02). An initial dose rate of 3 Gy/hr or more completely ablated up to 5 g of tissue in 54 out of 62 patients (87.1%). Dose rate above 3 Gy/hr and cumulative doses above 300 Gy resulted in ablation in 50% of patients with more than 5 g of tissue.
In patients receiving 131I to ablate thyroid remnant, the initial dose rate and the tissue mass are determinants of successful treatment response.
评估累积吸收剂量、初始剂量率和残余甲状腺组织质量对放射性碘治疗结果的影响，以确定预测成功消融的吸收剂量和初始剂量率的最佳值。
对87例接受0.85 - 9.55 GBq（23 - 258 mCi）¹³¹I治疗以消融残余甲状腺组织的甲状腺癌患者，计算累积吸收剂量和初始剂量率。治疗后，使用β/γ照射率仪通过测量颈部表面照射率，确定每位患者的放射性碘摄取参数和有效半衰期。通过体模研究获得的散射校正后的直线图像确定甲状腺残余质量。
放射性碘治疗后，68例患者甲状腺残余完全消融，19例部分消融。完全消融组和部分消融组组织所接受的累积吸收剂量无显著差异（0.6＞p＞0.5）。然而，两组组织的初始剂量率存在显著差异（0.05＞p＞0.02）。62例患者中有54例（87.1%）初始剂量率为3 Gy/hr或更高时可完全消融达5 g的组织。剂量率高于3 Gy/hr且累积剂量高于300 Gy时，50%超过5 g组织的患者实现消融。
在接受¹³¹I消融甲状腺残余的患者中，初始剂量率和组织质量是治疗成功反应的决定因素。
