Faculty of Science, Mohammed V University in Rabat, Rabat.
Nuclear Medicine Department, Oncology and Hematology Hospital, Mohammed VI University Hospital, Marrakesh, Morocco.
Nucl Med Commun. 2023 Nov 1;44(11):959-967. doi: 10.1097/MNM.0000000000001750. Epub 2023 Aug 24.
223 Ra is a promising α-emitting radionuclide for prostate cancer metastasis palliative treatment. Post-injection scintigraphy is of major importance to verify the concentration of the radiopharmaceutical in the targeted sites. Given the low activity administered to patients, the choice of acquisition parameters, including the collimator type, the energy window's width and the photopeak energy to be used, is primordial for the image quality. The purpose of our work was to select the SPECT configuration suitable for 223 Ra post-injection scintigraphy.
We conducted simulation studies with a Symbia T6 Siemens SPECT-CT, available in our department. 223 Ra photons energy spectra were assessed for low energy high resolution (LEHR), medium energy (ME) and high energy (HE) collimators. Then, depending on the energy window, we calculated the scatter fraction, the sensitivity and the spatial resolution.
Scatter fraction was low for all collimators; however, the contribution of photons that scattered more than twice under the low energy photopeaks was important in the case of LEHR. Sensitivity's best values were obtained in the case of the LEHR collimator; nevertheless, the spatial resolution was very low for this collimator. The latter was best for ME and HE collimators.
A combination between a good sensitivity, a high spatial resolution and a low scatter fraction has been determined in the case of the ME collimator, followed by HE collimator as an alternative. To increase the image acquisition statistics with ME collimator, we recommend to use simultaneous energy windows: 20% centered at 82 keV, 20% centered at 154 keV and 20% centered at 270 keV.
223Ra 是一种有前途的用于前列腺癌转移姑息治疗的α发射放射性核素。注射后闪烁显像对于验证放射性药物在靶向部位的浓度非常重要。鉴于给予患者的放射性活度低，选择采集参数，包括准直器类型、能窗宽度和要使用的光电峰能量，对于图像质量至关重要。我们的工作目的是选择适合 223Ra 注射后闪烁显像的 SPECT 配置。
我们在我们部门可用的 Symbia T6 西门子 SPECT-CT 上进行了模拟研究。评估了低能高分辨率（LEHR）、中能（ME）和高能（HE）准直器的 223Ra 光子能谱。然后，根据能窗，我们计算了散射分数、灵敏度和空间分辨率。
所有准直器的散射分数都较低；然而，在 LEHR 情况下，在低能光电峰下散射两次以上的光子的贡献很重要。LEHR 准直器获得了最佳的灵敏度值；然而，该准直器的空间分辨率非常低。ME 和 HE 准直器的空间分辨率最好。
在 ME 准直器的情况下，确定了良好的灵敏度、高空间分辨率和低散射分数之间的组合，其次是 HE 准直器作为替代。为了使用 ME 准直器增加图像采集统计数据，我们建议使用同时的能窗：20% 中心在 82keV，20% 中心在 154keV，20% 中心在 270keV。
