Faculty of Natural Sciences, Shumen University, Shumen, Bulgaria. Legnaro National Laboratories, INFN, Legnaro, (Padua), Italy. Permanent address: 115 Universitetska str., Faculty of Natural Sciences, University of Shumen, 9712 Shumen, Bulgaria. Author to whom any correspondence should be addressed.
Phys Med Biol. 2018 Sep 19;63(18):185021. doi: 10.1088/1361-6560/aadc88.
Evaluation of the radioisotopic purity of technetium-99m (Tc) produced in GBq amounts by proton bombardment of enriched molibdenum-100 (Mo) metallic targets at low proton energies (i.e. within 15-20 MeV) is conducted. This energy range was chosen since it is easily achievable by many conventional medical cyclotrons already available in the nuclear medicine departments of hospitals. The main motivation for such a study is in the framework of the research activities at the international level that have been conducted over the last few years to develop alternative production routes for the most widespread radioisotope used in medical imaging. The analysis of technetium isotopes and isomeric states (Tc) present in the pertechnetate saline NaTcO solutions, obtained after the extraction/purification procedure, reveals radionuclidic purity levels basically in compliance with the limits recently issued by European Pharmacopoeia 9.3 (2018 Sodium pertechnetate (Tc) injection 4801-3). Moreover, the impact of Tc contaminant nuclides on the final image quality is thoroughly evaluated, analyzing the emitted high-energy gamma rays and their influence on the image quality. The spatial resolution of images from cyclotron-produced Tc acquired with a mini-gamma camera was determined and compared with that obtained using technetium-99m solutions eluted from standard Mo/Tc generators. The effect of the increased image background contribution due to Compton-scattered higher-energy gamma rays (E > 200 keV), which could cause image-contrast deterioration, was also studied. It is concluded that, due to the high radionuclidic purity of cyclotron-produced Tc using Mo(p,2n)Tc reaction at a proton beam energy in the range 15.7-19.4 MeV, the resulting image properties are well comparable with those from the generator-eluted Tc.
评估了在低质子能量（即 15-20 MeV 范围内）下，用质子轰击富钼-100（Mo）金属靶产生的 99m 锝（Tc）的放射性同位素纯度。选择这个能量范围是因为许多医院核医学部门现有的常规医用回旋加速器很容易达到这个能量范围。进行这项研究的主要动机是在过去几年中，国际上开展了研究活动，以开发用于医学成像的最广泛使用的放射性同位素的替代生产途径。对经提取/纯化程序后从高锝酸盐盐 NaTcO 溶液中获得的 Tc 同位素和同质异能态（Tc）的分析表明，放射性核素纯度水平基本符合欧洲药典 9.3（2018 年锝（Tc）过氧酸盐注射液 4801-3）最近发布的限制。此外，通过分析发射的高能伽马射线及其对图像质量的影响，彻底评估了 Tc 污染物核素对最终图像质量的影响。用小型伽马相机获取的回旋加速器产生的 Tc 的图像空间分辨率进行了测定，并与从标准 Mo/Tc 发生器洗脱的 Tc 溶液获得的图像分辨率进行了比较。还研究了由于 Compton 散射的高能伽马射线（E>200 keV）引起的图像背景贡献增加对图像质量的影响，这可能导致图像对比度恶化。研究结果表明，由于在 15.7-19.4 MeV 的质子束能量范围内，用 Mo(p,2n)Tc 反应产生的回旋加速器产生的 Tc 的放射性核素纯度高，因此产生的图像特性与发生器洗脱的 Tc 相比非常相似。
