Cassano Bartolomeo, Miseo Ludovica, Ungania Sara, D'Andrea Marco, Murtas Federica, Pacilio Massimiliano, Bottero Marta, Maccora Daria, Sciuto Rosa, Vallati Giulio Eugenio, Soriani Antonella, Iaccarino Giuseppe
Department of Research, Diagnosis and Innovative Technologies, Medical Physics Unit, IRCCS Regina Elena National Cancer Institute, Rome, Italy.
Post Graduation School of Medical Physics, Tor Vergata, Rome, Italy.
EJNMMI Phys. 2025 Jul 3;12(1):64. doi: 10.1186/s40658-025-00779-8.
Ho-poly-L-lactic acid microspheres (Ho-PLLA) offer the advantage of using the same microspheres for both Scout and Therapeutic Administrations (SA and TA) in radioembolization compared to Y. This study aimed to quantify and correct dead time (DT) effects in dose estimation and assess the predictive power of SA on TA.
A 1.9 GBq Ho-PLLA activity source was placed in a CIRS phantom and imaged over a week until activity reached 83 MBq, assessing DT effects. Fifteen patients with a single hepatic lesion underwent SA and TA two weeks apart with following SPECT/CT imaging. The mean absorbed dose (AD) and distribution were calculated using the Local Energy Deposition (LED) method for liver, healthy liver (HL) and tumor contours. Three methods were compared for TA AD estimation: no DT correction (M1), whole-image DT correction (M2), and DT correction only for tumor ROI counts (M3). Linear correlation and percentage differences (ΔD%) between SA and TA AD were analyzed. AD distributions in SA and TA were rigidly registered for gamma index analysis (Dose Difference of 10% and Distance to Agreement of 10 mm).
DT effects were significant for activity above 250 MBq (> 11.5%). Strong linear correlations between mean AD values in SA and TA were observed across methods. ΔD% between SA and TA for the liver contour was - 8.6% (M1), 21.5% (M2), and 8.2% (M3). For the HL contour, ΔD% was 8.1% (M1) and 39.0% (M2), while for the tumor contour, it was - 20.1% (M1) and 0.0% (M2). Gamma index pass rates for the liver contour were 76% (M1), 89% (M2), and 92% (M3); for the HL contour, 80% (M1) and 75% (M2); and for the tumor contour, 70% (M1) and 87% (M2).
DT significantly affects TA dose estimation, particularly in tumors. Proper DT correction improves the accuracy of dosimetric evaluation of Ho-PLLA for TA in liver and metastases, yielding dose values closer to those obtained in SA, despite the latter not being corrected for DT.
与钇相比，钬聚左旋乳酸微球（Ho-PLLA）在放射性栓塞的 Scout 和治疗给药（SA 和 TA）中使用相同微球具有优势。本研究旨在量化和校正剂量估计中的死时间（DT）效应，并评估 SA 对 TA 的预测能力。
将一个 1.9 GBq 的 Ho-PLLA 活度源置于 CIRS 体模中，并在一周内进行成像，直至活度降至 83 MBq，评估 DT 效应。15 例有单个肝损伤的患者相隔两周分别接受 SA 和 TA，随后进行 SPECT/CT 成像。使用局部能量沉积（LED）方法计算肝脏、健康肝脏（HL）和肿瘤轮廓的平均吸收剂量（AD）及分布。比较了三种用于 TA 吸收剂量估计的方法：无 DT 校正（M1）、全图像 DT 校正（M2）以及仅对肿瘤感兴趣区计数进行 DT 校正（M3）。分析了 SA 和 TA 吸收剂量之间的线性相关性和百分比差异（ΔD%）。对 SA 和 TA 中的吸收剂量分布进行刚性配准以进行伽马指数分析（剂量差异 10%，距离一致性 10 mm）。
活度高于 250 MBq 时，DT 效应显著（> 11.5%）。各方法中 SA 和 TA 的平均吸收剂量值之间均观察到强线性相关性。肝脏轮廓的 SA 和 TA 之间的 ΔD%为 - 8.6%（M1）、21.5%（M2）和 8.2%（M3）。对于 HL 轮廓，ΔD%为 8.1%（M1）和 39.0%（M2），而对于肿瘤轮廓，为 - 20.1%（M1）和 0.0%（M2）。肝脏轮廓的伽马指数通过率分别为 76%（M1）、89%（M2）和 92%（M3）；HL 轮廓为 80%（M1）和 75%（M2）；肿瘤轮廓为 70%（M1）和 87%（M2）。
DT 显著影响 TA 剂量估计，尤其是在肿瘤中。适当的 DT 校正可提高 Ho-PLLA 在肝脏和转移灶中 TA 剂量学评估的准确性，使剂量值更接近 SA 中获得的值，尽管 SA 未进行 DT 校正。
