Transarterial radioembolization (TARE) effectively treats unresectable primary and metastatic liver tumors through intra‐arterial injection of Yttrium‐90 (⁹⁰Y) beta particle emitting microspheres which implant around the tumor. Current dosimetry models are highly simplistic and there is a large need for an image‐based dosimetry post‐TARE, which would improve treatment safety and efficacy. Current post‐TARE imaging is ⁹⁰Y bremsstrahlung SPECT/CT and we study the use of these images for dosimetry. Retrospective image review of ten patients having a Philips Healthcare^TM SPECT/CT following TARE SIR‐Spheres® implantation. Emission series with attenuation correction were resampled to 3 mm resolution and used to create image‐based dose distributions. Dose distributions and analysis were performed in MIM Software SurePlan^TM utilizing SurePlan^TM Local Deposition Method (LDM) and a dose convolution method (WFBH). We sought to implement a patient‐specific background subtraction prior to dose calculation to make these noisy bremsstrahlung SPECT images suitable for post‐TARE dosimetry. On average the percentage of mean background counts to maximum count in the image across all patients was 9.4 ± 4.9% (maximum = 7.6%, minimum = 2.3%). Absolute dose increased and profile line width decreased as background subtraction value increased. The average value of the LDM and WFBH dose methods was statistically the same. As background subtraction value increased, the DVH curves become unrealistic and distorted. Background subtraction on bremsstrahlung SPECT image has a large effect on post‐TARE dosimetry. The background contour defined provides a systematic estimate to the activity background that accounts for the scanner and patient conditions at the time of the image study and is easily implemented using commercially available software. Using the mean count in the background contour as a subtraction across the entire image gave the most realistic dose distributions. This methodology is independent of microsphere and software manufacturer allowing for use with any available products or tools.

中文翻译：

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经动脉放射栓塞后的回顾性SPECT / CT剂量

经动脉内注射Yttrium- 90（⁹⁰ Y）β粒子发射微球，将其植入肿瘤周围，经动脉放射栓塞（TARE）可有效治疗无法切除的原发性和转移性肝肿瘤。当前的剂量学模型非常简单，并且急需在TARE之后使用基于图像的剂量学，以提高治疗的安全性和有效性。当前的TARE后成像是⁹⁰ Y致SPECT / CT，我们研究了这些图像在剂量测定中的用途。回顾性分析10例具有Philips Healthcare ^TM的患者TARESIR-Spheres®植入后的SPECT / CT。带有衰减校正的发射序列被重新采样到3 mm分辨率，并用于创建基于图像的剂量分布。使用SurePlan ^TM在MIM软件SurePlan ^TM中进行剂量分布和分析局部沉积法（LDM）和剂量卷积法（WFBH）。我们试图在剂量计算之前实施针对患者的本底扣除，以使这些嘈杂的致辐射SPECT图像适合于TARE剂量测定。在所有患者中，图像中平均背景计数相对于最大计数的百分比平均为9.4±4.9％（最大值= 7.6％，最小值= 2.3％）。随着背景扣除值的增加，绝对剂量增加，轮廓线宽度减小。LDM和WFBH剂量方法的平均值在统计学上是相同的。随着背景减法值的增加，DVH曲线变得不现实且失真。致辐射SPECT图像的背景减法对去皮后剂量测定有很大影响。定义的背景轮廓为活动背景提供了系统的估算，该估算考虑了图像研究时的扫描仪和患者状况，并且可以使用市售软件轻松实现。使用背景轮廓中的平均值作为整个图像的减法，可以得出最真实的剂量分布。这种方法独立于微球和软件制造商，允许与任何可用的产品或工具一起使用。