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Abstract：
OBJECTIVE: This study aimed to assess the accuracy of patient-specific absorbed dose calculations for tumours and organs at risk in radiopharmaceutical therapy planning, utilizing hybrid planar-SPECT/CT imaging.
METHODS: Three Monte Carlo (MC) simulated digital patient phantoms were created, with time-activity data for mIBG labelled to I-123 (LEHR and ME collimators) and I-131 (HE collimator). The study assessed the accuracy of the mean absorbed doses for I-131-mIBG therapy treatment planning. Multiple planar whole-body (WB) images were simulated (between 1 to 72 h post-injection (p.i)). The geometric-mean image of the anterior and posterior WB images was calculated, with scatter and attenuation corrections applied. Time-activity curves were created for regions of interest over the liver and two tumours (diameters: 3.0 cm and 5.0 cm) in the WB images. A corresponding SPECT study was simulated at 24 h p.i and reconstructed using the OS-EM algorithm, incorporating scatter, attenuation, collimator-detector response, septal scatter and penetration corrections. MC voxel-based absorbed dose rate calculations used two image sets, (i) the activity distribution represented by the SPECT images and (ii) the activity distribution from the SPECT images distributed uniformly within the volume of interest. Mean absorbed doses were calculated considering photon and charged particle emissions, and beta emissions only. True absorbed doses were calculated by MC voxel-based dosimetry of the known activity distributions for reference.
RESULTS: Considering photon and charged particle emissions, mean absorbed dose accuracies across all three radionuclide-collimator combinations of 3.8 ± 5.5% and 0.1 ± 0.9% (liver), 5.2 ± 10.0% and 4.3 ± 1.7% (3.0 cm tumour) and 15.0 ± 5.8% and 2.6 ± 0.6% (5.0 cm tumour) were obtained for image set (i) and (ii) respectively. Considering charged particle emissions, accuracies of 2.7 ± 4.1% and 5.7 ± 0.7% (liver), 3.2 ± 10.2% and 9.1 ± 1.7% (3.0 cm tumour) and 13.6 ± 5.7% and 7.0 ± 0.6% (5.0 cm tumour) were obtained for image set (i) and (ii) respectively.
CONCLUSIONS: The hybrid WB planar-SPECT/CT method proved accurate for I-131-mIBG dosimetry, suggesting its potential for personalized treatment planning.
METHODS: Three Monte Carlo (MC) simulated digital patient phantoms were created, with time-activity data for mIBG labelled to I-123 (LEHR and ME collimators) and I-131 (HE collimator). The study assessed the accuracy of the mean absorbed doses for I-131-mIBG therapy treatment planning. Multiple planar whole-body (WB) images were simulated (between 1 to 72 h post-injection (p.i)). The geometric-mean image of the anterior and posterior WB images was calculated, with scatter and attenuation corrections applied. Time-activity curves were created for regions of interest over the liver and two tumours (diameters: 3.0 cm and 5.0 cm) in the WB images. A corresponding SPECT study was simulated at 24 h p.i and reconstructed using the OS-EM algorithm, incorporating scatter, attenuation, collimator-detector response, septal scatter and penetration corrections. MC voxel-based absorbed dose rate calculations used two image sets, (i) the activity distribution represented by the SPECT images and (ii) the activity distribution from the SPECT images distributed uniformly within the volume of interest. Mean absorbed doses were calculated considering photon and charged particle emissions, and beta emissions only. True absorbed doses were calculated by MC voxel-based dosimetry of the known activity distributions for reference.
RESULTS: Considering photon and charged particle emissions, mean absorbed dose accuracies across all three radionuclide-collimator combinations of 3.8 ± 5.5% and 0.1 ± 0.9% (liver), 5.2 ± 10.0% and 4.3 ± 1.7% (3.0 cm tumour) and 15.0 ± 5.8% and 2.6 ± 0.6% (5.0 cm tumour) were obtained for image set (i) and (ii) respectively. Considering charged particle emissions, accuracies of 2.7 ± 4.1% and 5.7 ± 0.7% (liver), 3.2 ± 10.2% and 9.1 ± 1.7% (3.0 cm tumour) and 13.6 ± 5.7% and 7.0 ± 0.6% (5.0 cm tumour) were obtained for image set (i) and (ii) respectively.
CONCLUSIONS: The hybrid WB planar-SPECT/CT method proved accurate for I-131-mIBG dosimetry, suggesting its potential for personalized treatment planning.
摘要：
目的：本研究旨在评估放射性药物治疗计划中肿瘤和危险器官患者特定吸收剂量计算的准确性，利用混合平面-SPECT/CT成像。
方法：创建了三个蒙特卡洛（MC）模拟数字患者体模，将mIBG的时间活动数据标记为I-123（LEHR和ME准直器）和I-131（HE准直器）。该研究评估了I-131-mIBG治疗计划的平均吸收剂量的准确性。模拟了多个平面全身（WB）图像（注射后1至72小时之间（p。i)).计算前后WB图像的几何平均图像，应用散射和衰减校正。在WB图像中针对肝脏上的感兴趣区域和两个肿瘤(直径:3.0cm和5.0cm)创建时间-活性曲线。在24hp.i时模拟了相应的SPECT研究，并使用OS-EM算法进行了重建，结合散射，衰减，准直器-探测器响应，间隔散射和穿透校正。基于MC体素的吸收剂量率计算使用两个图像集，(i)由SPECT图像表示的活动分布和(ii)来自在感兴趣体积内均匀分布的SPECT图像的活动分布。考虑光子和带电粒子发射，计算平均吸收剂量，只有β排放。通过基于MC体素的已知活性分布的剂量测定法计算真实吸收剂量，以供参考。
结果：考虑到光子和带电粒子的发射，所有三个放射性核素准直仪组合的平均吸收剂量精度为3.8±5.5％和0.1±0.9％（肝脏），对于图像集(i)和(ii),分别获得5.2±10.0%和4.3±1.7%(3.0cm肿瘤)和15.0±5.8%和2.6±0.6%(5.0cm肿瘤)。考虑到带电粒子的排放,准确率为2.7±4.1%和5.7±0.7%(肝脏)，对于图像集(i)和(ii),分别获得3.2±10.2%和9.1±1.7%(3.0cm肿瘤)和13.6±5.7%和7.0±0.6%(5.0cm肿瘤)。
结论：混合WB平面-SPECT/CT方法被证明对I-131-mIBG剂量测定是准确的，表明其个性化治疗计划的潜力。
方法：创建了三个蒙特卡洛（MC）模拟数字患者体模，将mIBG的时间活动数据标记为I-123（LEHR和ME准直器）和I-131（HE准直器）。该研究评估了I-131-mIBG治疗计划的平均吸收剂量的准确性。模拟了多个平面全身（WB）图像（注射后1至72小时之间（p。i)).计算前后WB图像的几何平均图像，应用散射和衰减校正。在WB图像中针对肝脏上的感兴趣区域和两个肿瘤(直径:3.0cm和5.0cm)创建时间-活性曲线。在24hp.i时模拟了相应的SPECT研究，并使用OS-EM算法进行了重建，结合散射，衰减，准直器-探测器响应，间隔散射和穿透校正。基于MC体素的吸收剂量率计算使用两个图像集，(i)由SPECT图像表示的活动分布和(ii)来自在感兴趣体积内均匀分布的SPECT图像的活动分布。考虑光子和带电粒子发射，计算平均吸收剂量，只有β排放。通过基于MC体素的已知活性分布的剂量测定法计算真实吸收剂量，以供参考。
结果：考虑到光子和带电粒子的发射，所有三个放射性核素准直仪组合的平均吸收剂量精度为3.8±5.5％和0.1±0.9％（肝脏），对于图像集(i)和(ii),分别获得5.2±10.0%和4.3±1.7%(3.0cm肿瘤)和15.0±5.8%和2.6±0.6%(5.0cm肿瘤)。考虑到带电粒子的排放,准确率为2.7±4.1%和5.7±0.7%(肝脏)，对于图像集(i)和(ii),分别获得3.2±10.2%和9.1±1.7%(3.0cm肿瘤)和13.6±5.7%和7.0±0.6%(5.0cm肿瘤)。
结论：混合WB平面-SPECT/CT方法被证明对I-131-mIBG剂量测定是准确的，表明其个性化治疗计划的潜力。
