18F-PSMA-1007 唾液腺剂量学：不同剂量计算方法比较及患者间与患者内变异性评估
$^{18}$F-PSMA-1007 salivary gland dosimetry: Comparison between different methods for dose calculation and assessment of inter- and intra-patient variability
AI总结：
该研究比较了多种剂量学方法计算 18F-PSMA-1007 注射后唾液腺吸收剂量的准确性，发现简化方法显著低估剂量且患者间及组分间变异大，强调应使用蒙特卡罗模拟并考虑单个腺体组分的特定质量。
摘要：
唾液腺（SGs）的剂量学通常采用简化计算方法和近似几何结构来实施。我们的目标是比较注射 18F-PSMA-1007 后计算唾液腺吸收剂量（ADs）的不同剂量学方法，并评估不同患者之间以及单个唾液腺组分之间的吸收剂量变异。五名前列腺癌复发患者在注射 18F-PSMA-1007 后 0.5、2 和 4 小时接受了头颈部 PET/CT 采集。在 CT 上分割腮腺和下颌下腺以得出唾液腺体积和质量，同时使用 PET 数据推导时间积分活度系数。单个唾液腺组分或总唾液腺（tSG）的平均吸收剂量采用以下方法计算：i）使用 GATE/GEANT4 进行直接蒙特卡罗（MC）模拟；ii）OLINDA/EXM 2.1 的球体模型（SM），采用患者特异性或标准 ICRP89 器官质量（SMstd）；iii）椭球模型（EM）；iv）MIRD 方法，使用来自 OLINDA/EXM 2.1 和 OpenDose 合作的器官 S 因子，包含或不包含源自唾液腺外部的交叉照射贡献。计算了唾液腺组分之间的最大百分比吸收剂量差异（δmax）和患者之间的最大百分比吸收剂量差异（Δmax）。与 MC 相比，所有方法均显著低估了单个唾液腺组分的吸收剂量（平均相对差异在 -14.5% 至 -30.4% 之间）。使用 MC、SM 和 EM 时，δmax 从未低于 25%（最高达 113%）。使用 SMstd 获得的 δmax 高达 702%。关于总唾液腺，只有当考虑来自身体其余部分或头部其余部分的交叉照射时，才能获得在 MC 结果 10% 以内的结果。患者之间的 Δmax 范围在 58% 至 78% 之间。鉴于单个唾液腺组分在患者内和患者间存在较大的变异性，应始终考虑其特定质量。
英文摘要：
Dosimetry of salivary glands (SGs) is usually implemented using simplified calculation approaches and approximated geometries. Our aims were to compare different dosimetry methods to calculate SGs absorbed doses (ADs) following 18F-PSMA-1007 injection, and to assess the AD variation across patients and single SG components. Five patients with prostate cancer recurrence underwent PET/CT acquisitions of the head and neck, 0.5, 2 and 4 hours after 18F-PSMA-1007 injection. Parotid and submandibular glands were segmented on CT to derive SGs volumes and masses, while PETs were used to derive Time-Integrated Activity Coefficients. Average ADs to single SG components or total SG (tSG) were calculated with the following methods: i) direct Monte Carlo (MC) simulation with GATE/GEANT4; ii) spherical model (SM) of OLINDA/EXM 2.1, adopting either patient-specific or standard ICRP89 organ masses (SMstd); iii) ellipsoidal model (EM); iv) MIRD approach with organ S-factors from OLINDA/EXM 2.1 and OpenDose collaboration, with or without contribution from cross irradiation originating outside the SGs. The maximum percent AD difference across SG components (δmax) and across patients (Δmax) were calculated. Compared to MC, ADs to single SG components were significantly underestimated by all methods (average relative differences between -14.5% and -30.4%). Using MC, SM and EM, δmax were never below 25% (up to 113%). δmax up to 702% were obtained with SMstd. Concerning tSG, results within 10% of the MC were obtained only if cross irradiation from the remainder of the body or from the remainder of the head was accounted for. The Δmax ranged between 58% and 78% across patients. Specific masses of single SG components should always be considered given their large intra- and inter- patient variability.
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