PDF(Pubmed)
Abstract：
BACKGROUND: Although the importance of quantitative SPECT has increased tremendously due to newly developed therapeutic radiopharmaceuticals, there are still no accreditation programs to harmonize SPECT imaging. Work is currently underway to develop an accreditation for quantitative 177Lu SPECT/CT. The aim of this study is to verify whether the positioning of the spheres within the phantom has an influence on the recovery and thus needs to be considered in SPECT harmonization. In addition, the effects of these recovery coefficients on a potential partial volume correction as well as absorbed-dose estimates are investigated.
METHODS: Using a low-dose CT of a SPECT/CT acquisition, a computerized version of the NEMA body phantom was created using a semi-automatic threshold-based method. Based on the mass-density map, the detector orbit, and the sphere centers, realistic SPECT acquisitions of all possible 720 sphere configurations of both the PET and the SPECT versions of the NEMA Body Phantom were generated using Monte Carlo simulations. SPECT reconstructions with different numbers of updates were performed without (CASToR) and with resolution modeling (STIR). Recovery coefficients were calculated for all permutations, reconstruction methods, and phantoms, and their dependence on the sphere positioning was investigated. Finally, the simulation-based findings were validated using SPECT/CT acquisitions of six different sphere configurations.
RESULTS: Our analysis shows that sphere positioning has a significant impact on the recovery for both of the reconstruction methods and the phantom type. Although resolution modeling resulted in significantly higher recovery, the relative variation in recovery within the 720 permutations was even larger. When examining the extreme values of the recovery, reconstructions without resolution modeling were influenced primarily by the sphere position, while with resolution modeling the volume of the two adjacent spheres had a larger influence. The SPECT measurements confirmed these observations, and the recovery curves showed good overall agreement with the simulated data.
CONCLUSIONS: Our study shows that sphere positioning has a significant impact on the recovery obtained in NEMA sphere phantom measurements and should therefore be considered in a future SPECT accreditation. Furthermore, the single-measurement method normally performed for PVC should be reconsidered to account for the position dependency.
METHODS: Using a low-dose CT of a SPECT/CT acquisition, a computerized version of the NEMA body phantom was created using a semi-automatic threshold-based method. Based on the mass-density map, the detector orbit, and the sphere centers, realistic SPECT acquisitions of all possible 720 sphere configurations of both the PET and the SPECT versions of the NEMA Body Phantom were generated using Monte Carlo simulations. SPECT reconstructions with different numbers of updates were performed without (CASToR) and with resolution modeling (STIR). Recovery coefficients were calculated for all permutations, reconstruction methods, and phantoms, and their dependence on the sphere positioning was investigated. Finally, the simulation-based findings were validated using SPECT/CT acquisitions of six different sphere configurations.
RESULTS: Our analysis shows that sphere positioning has a significant impact on the recovery for both of the reconstruction methods and the phantom type. Although resolution modeling resulted in significantly higher recovery, the relative variation in recovery within the 720 permutations was even larger. When examining the extreme values of the recovery, reconstructions without resolution modeling were influenced primarily by the sphere position, while with resolution modeling the volume of the two adjacent spheres had a larger influence. The SPECT measurements confirmed these observations, and the recovery curves showed good overall agreement with the simulated data.
CONCLUSIONS: Our study shows that sphere positioning has a significant impact on the recovery obtained in NEMA sphere phantom measurements and should therefore be considered in a future SPECT accreditation. Furthermore, the single-measurement method normally performed for PVC should be reconsidered to account for the position dependency.
摘要：
背景：尽管由于新开发的治疗性放射性药物，定量SPECT的重要性大大增加，仍然没有统一SPECT成像的认证计划.目前正在开发177LuSPECT/CT定量认证的工作。这项研究的目的是验证球体在体模内的定位是否对恢复有影响，因此需要在SPECT协调中加以考虑。此外,研究了这些恢复系数对潜在的部分体积校正以及吸收剂量估计的影响。
方法：使用SPECT/CT采集的低剂量CT，NEMA体模的计算机化版本是使用半自动基于阈值的方法创建的。根据质量密度图,探测器轨道,球体的中心，使用蒙特卡罗模拟生成PET和NEMA身体幻像的SPECT版本的所有可能的720球体配置的真实SPECT采集。在没有（CASToR）和分辨率建模（STIR）的情况下，进行了不同更新次数的SPECT重建。计算所有排列的恢复系数，重建方法,和幻影，并研究了它们对球体定位的依赖性。最后,采用SPECT/CT采集的6种不同球体结构对基于模拟的研究结果进行了验证.
结果：我们的分析表明，对于两种重建方法和体模类型，球体定位对恢复都有重大影响。尽管分辨率建模导致了显着更高的恢复，720排列中恢复的相对差异甚至更大.当检查恢复的极值时，没有分辨率建模的重建主要受球体位置的影响，而分辨率建模的两个相邻球体的体积有较大的影响。SPECT测量结果证实了这些观察结果,回收率曲线与模拟数据总体吻合良好。
结论：我们的研究表明，球体定位对NEMA球体体模测量中获得的回收率具有重大影响，因此应在未来的SPECT认证中予以考虑。此外，应重新考虑通常对PVC进行的单一测量方法，以考虑位置依赖性。
方法：使用SPECT/CT采集的低剂量CT，NEMA体模的计算机化版本是使用半自动基于阈值的方法创建的。根据质量密度图,探测器轨道,球体的中心，使用蒙特卡罗模拟生成PET和NEMA身体幻像的SPECT版本的所有可能的720球体配置的真实SPECT采集。在没有（CASToR）和分辨率建模（STIR）的情况下，进行了不同更新次数的SPECT重建。计算所有排列的恢复系数，重建方法,和幻影，并研究了它们对球体定位的依赖性。最后,采用SPECT/CT采集的6种不同球体结构对基于模拟的研究结果进行了验证.
结果：我们的分析表明，对于两种重建方法和体模类型，球体定位对恢复都有重大影响。尽管分辨率建模导致了显着更高的恢复，720排列中恢复的相对差异甚至更大.当检查恢复的极值时，没有分辨率建模的重建主要受球体位置的影响，而分辨率建模的两个相邻球体的体积有较大的影响。SPECT测量结果证实了这些观察结果,回收率曲线与模拟数据总体吻合良好。
结论：我们的研究表明，球体定位对NEMA球体体模测量中获得的回收率具有重大影响，因此应在未来的SPECT认证中予以考虑。此外，应重新考虑通常对PVC进行的单一测量方法，以考虑位置依赖性。
