Treatment planning for a synchrotron-based radiotherapy modality

Contrast enhanced radiotherapy (CERT) achieves biologically localised dose enhancement through the preferential uptake of high-Z media by the tumour cells. A treatment planning software originally developed for boron neutron capture therapy (BNCT) has been developed to evaluate treatment plans for CERT. A realistic test case of a brain tumour based on actual CT scans was used to calculate dose distributions with and without the presence of an iodinated contrast medium. An enhancement of dose was observed at all depths with the introduction of iodine and the corresponding dose enhancement factors were calculated for various concentrations.     

环境电离辐射体源表面剂量率的MC模拟计算及实验比较

目的　对核工业地质勘查计量站的 8个圆柱型环境电离辐射体源和两个本底模型上方不同高度处的空气吸收剂量率进行较为准确的定值。方法　采用蒙特卡罗软件MCNP ,对上述环境电离辐射体源和本底模型上方的空气吸收剂量率进行了模拟计算 ,采用 1台高气压电离室剂量率仪对各环境电离辐射体源和本底模型上方不同高度处的空气吸收剂量率进行了实测 ,模拟计算结果与实测结果以及其他工作者过去所作的剂量率测量和计算结果进行了比较。结果　MC模拟计算值与其他工作者得到的空气吸收剂量率理论值吻合较好 ,最大偏差小于 10 % ,一般偏差小于±5 %。结论　只要各种输入参数准确 ,采用MC模拟计算 ,可以得到辐射体源和本底模型上方不同高度处较准确 (3%不确定度 )的空气吸收剂量率模拟计算值。     

Microwave Spectroscopy of Myocardial Ischemia and Infarction. 2. Biophysical Reconstruction

The proposed dielectrical relaxation model of the myocardium in the microwave spectrum has been verified both on test solutions and on normal canine myocardium. Furthermore, the model was utilized to reconstruct the changes in tissue properties (including myocardial bulk resistance and water content) following myocardial acute ischemia and chronic infarction. It was shown that the reconstructed myocardial resistance and water content correlate dynamically with the process of the development of acute myocardial ischemic injury. In chronic cases the reconstructed resistance and water content of infarcted myocardium are significantly different from that of normal myocardium: the resistance is lower and water content is higher than in normal myocardium. © 2000 Biomedical Engineering Society. PAC00: 8764-t, 8719Xx     

In vivo characteristics of low molecular weight copoly (D,L-lactic acid) formulations with controlled release of LH-RH agonist

Amorphous and crystalline copolymers with a relatively low molecular weight of 1800 were synthesized by direct copolycondensation of D-lactic acid and L-lactic acid in the absence of a catalyst, to evaluate their in vivo capabilities as biodegradable carriers for drug delivery systems. A luteinizing hormone-releasing hormone agonist, des-Gly10-(D-Leu6)-LH-RH ethylamide, was incorporated in a fine cylindrical copolymer formulation, under melt-pressing technique, a mild heat-pressure condition. This formulation was implanted subcutaneously in the back of male rats. The rate of in vivo degradation of amorphous copolymer was much faster than that of crystalline copolymer. Contrary to this tendency, the in vivo release of the drug from this amorphous formulation was held constant over a longer period, compared with the crystalline formulation. This can be closely related to the difference in dispersion of the drug in the formulation.     

2018—2020年参加全国放射性核素γ能谱考核结果分析

目的 保证γ放射性核素实验室活动和结果的有效性,提高实验室γ放射性核素检测的能力。方法 对影响全国γ放射性核素考核结果的相对偏差、准确度、精确度、相对合成不确定度进行统计分析。结果 本实验室2018—2020年全国γ放射性核素考核上报结果均满足合格要求,其中2019年被评为优秀,2018—2020年11个测量结果相对偏差最大为18.01%,2018年|Z_检验|≤1、U_检验≤2.58,2019年|Z_检验|≤1、U_检验≤1,2020年U_检验≤1、U_rel≤20%。结论 本实验室采用的放射性核素γ能谱分析方法正确,检测数据准确、可靠。