Joint Department of Physics, Royal Marsden NHSFT, Sutton, United Kingdom; The Institute of Cancer Research, London, United Kingdom.
Joint Department of Physics, Royal Marsden NHSFT, Sutton, United Kingdom; The Institute of Cancer Research, London, United Kingdom.
Phys Med. 2021 Sep;89:1-10. doi: 10.1016/j.ejmp.2021.07.026. Epub 2021 Jul 30.
The aims of this study were to develop and apply a method to correct for the differences in partial volume effects of pre-therapy Technetium-99 m (Tc)-MAA SPECT and post-therapy Yttrium-90 (Y) bremsstrahlung SPECT imaging in selective internal radiation therapy, and to use this method to improve quantitative comparison of predicted and delivered Y absorbed doses.
The spatial resolution of Tc SPECT data was converted to that of Y SPECT data using a function calculated from Tc and Y point spread functions. This resolution conversion method (RCM) was first applied to Tc and Y SPECT phantom data to validate the method, and then to clinical data to assess the power of Tc SPECT imaging to predict the therapeutic absorbed dose.
The maximum difference between absorbed doses to phantom spheres was 178%. This was reduced to 27% after the RCM was applied. The clinical data demonstrated differences within 38% for mean absorbed doses delivered to the normal liver, which were reduced to 20% after application of the RCM. Analysis of clinical data showed that therapeutic absorbed doses delivered to tumours greater than 100 cm were predicted to within 52%, although there were differences of up to 210% for smaller tumours, even after the RCM was applied.
The RCM was successfully verified using phantom data. Analysis of the clinical data established that the Tc pre-therapy imaging was predictive of the Y absorbed dose to the normal liver to within 20%, but had poor predictability for tumours smaller than 100 cm.
本研究的目的是开发并应用一种方法，以校正选择性内部放射治疗中治疗前锝-99m（Tc）-MAA SPECT 和治疗后钇-90（Y）韧致辐射 SPECT 成像的部分容积效应差异，并使用该方法改善预测和交付的 Y 吸收剂量的定量比较。
使用从 Tc 和 Y 点扩散函数计算的函数将 Tc SPECT 数据的空间分辨率转换为 Y SPECT 数据。该分辨率转换方法（RCM）首先应用于 Tc 和 Y SPECT 体模数据以验证该方法，然后应用于临床数据以评估 Tc SPECT 成像预测治疗吸收剂量的能力。
体模球体的吸收剂量最大差异为 178%。应用 RCM 后，该差异减少至 27%。临床数据显示，正常肝脏的平均吸收剂量差异在 38%以内，应用 RCM 后减少至 20%。临床数据分析表明，大于 100cm 的肿瘤的治疗吸收剂量的预测值在 52%以内，尽管较小的肿瘤的预测值差异高达 210%，即使应用了 RCM。
RCM 已成功通过体模数据验证。对临床数据的分析表明，Tc 治疗前成像可以预测正常肝脏的 Y 吸收剂量，误差在 20%以内，但对于小于 100cm 的肿瘤，预测能力较差。
