Transarterial radioembolization (TARE) is a locoregional radiopharmaceutical therapy based on the delivery of radioactive ⁹⁰Y microspheres to liver tumors. The importance of personalized dosimetry to make TARE safer and more effective has been demonstrated in recent clinical studies, stressing the need for quantification of the dose–response relationship to ultimately optimize the administered activity before treatment and image it after treatment. ⁹⁰Y dosimetric studies are challenging because of the lack of accurate and precise methods but are best realized with PET combined with Monte Carlo simulations and other image modalities to calculate a segmental dose distribution. The aim of this study was to assess the suitability of imaging ⁹⁰Y PET patients with the total-body PET/CT uEXPLORER and to investigate possible improvements in TARE ⁹⁰Y PET-based dosimetry. The uEXPLORER is the first commercially available ultra-high-resolution (171 cps/kBq) total-body digital PET/CT device with a 194-cm axial PET field of view that enables the whole body to be scanned at a single bed position. Methods: Two PET/CT scanners were evaluated in this study: the Biograph mCT and the total-body uEXPLORER. Images of a National Electrical Manufacturers Association (NEMA) image-quality phantom and 2 patients were reconstructed using our standard clinical oncology protocol. A late portal phase contrast-enhanced CT scan was used to contour the liver segments and create corresponding volumes of interest. To calculate the absorbed dose, Monte Carlo simulations were performed using Geant4 Application for Tomographic Emission (GATE). The absorbed dose and dose–volume histograms were calculated for all 6 spheres (diameters ranging from 10 to 37 mm) of the NEMA phantom, the liver segments, and the entire liver. Differences between the phantom doses and an analytic ground truth were quantified through the root mean squared error. Results: The uEXPLORER showed a higher signal-to-noise ratio at 10- and 13-mm diameters, consistent with its high spatial resolution and system sensitivity. The total liver-absorbed dose showed excellent agreement between the uEXPLORER and the mCT for both patients, with differences lower than 0.2%. Larger differences of up to 60% were observed when comparing the liver segment doses. All dose–volume histograms were in good agreement, with narrower tails for the uEXPLORER in all segments, indicating lower image noise. Conclusion: This patient study is compelling for the use of total-body ⁹⁰Y PET for liver dosimetry. The uEXPLORER scanner showed a better signal-to-noise ratio than mCT, especially in lower-count regions of interest, which is expected to improve dose quantification and tumor dosimetry.

经动脉放射栓塞术 (TARE) 是一种基于向肝脏肿瘤输送放射性⁹⁰ Y 微球体的局部放射性药物疗法。个性化剂量测定使 TARE 更安全、更有效的重要性已在最近的临床研究中得到证实，强调需要量化剂量-反应关系，以最终优化治疗前的管理活动并在治疗后对其进行成像。^{由于缺乏准确和精确的方法， 90} Y 剂量学研究具有挑战性，但最好通过 PET 结合蒙特卡罗模拟和其他图像模式来计算分段剂量分布。本研究的目的是评估成像^{90的适用性}使用全身 PET/CT uEXPLORER 的 Y PET 患者，并研究基于 TARE ⁹⁰ Y PET 的剂量测定的可能改进。uEXPLORER 是第一款商用超高分辨率 (171 cps/kBq) 全身数字 PET/CT 设备，具有 194 厘米的轴向 PET 视野，可以在单床位扫描全身。方法：本研究评估了两种 PET/CT 扫描仪：Biograph mCT 和全身 uEXPLORER。使用我们的标准临床肿瘤学协议重建了国家电气制造商协会 (NEMA) 图像质量模型和 2 名患者的图像。晚期门静脉期对比增强 CT 扫描用于绘制肝段轮廓并创建相应的感兴趣体积。为了计算吸收剂量，使用 Geant4 断层扫描发射应用程序 (GATE) 进行了蒙特卡罗模拟。计算了 NEMA 体模、肝段和整个肝脏的所有 6 个球体（直径范围为 10 至 37 毫米）的吸收剂量和剂量体积直方图。通过均方根误差量化幻影剂量和分析地面实况之间的差异。结果：uEXPLORER 在 10 和 13 毫米直径处显示出更高的信噪比，与其高空间分辨率和系统灵敏度一致。两名患者的 uEXPLORER 和 mCT 之间的肝脏总吸收剂量显示出极好的一致性，差异低于 0.2%。比较肝段剂量时观察到高达 60% 的较大差异。所有剂量-体积直方图都非常一致，uEXPLORER 在所有部分的尾部都较窄，表明图像噪声较低。结论：这项患者研究对于使用全身⁹⁰Y PET 用于肝脏剂量测定。uEXPLORER 扫描仪显示出比 mCT 更好的信噪比，尤其是在较低计数的感兴趣区域，这有望改善剂量量化和肿瘤剂量测定。