Purpose

This study evaluates the quantitative effect of improved MR-based attenuation correction (AC), including bone segmentation and the HUGE method for truncation correction in PET/MR whole-body hybrid imaging specifically of oncologic patients with bone metastasis and using various radiotracers.

Methods

Twenty-three patients that underwent altogether 28 whole-body PET/MR examinations with findings of bone metastasis were included in this study. Different radiotracers (¹⁸F-FDG, ⁶⁸Ga-PSMA, ⁶⁸Ga-DOTATOC, ¹²⁴I–MIBG) were injected according to appropriate clinical indications. Each of the 28 whole-body PET datasets was reconstructed three times using AC with (1) standard four-compartment μ-maps (background air, lung, muscle, and soft tissue), (2) five-compartment μ-maps (adding bone), and (3) six-compartment μ-maps (adding bone and HUGE truncation correction). The SUV_max of each detected bone lesion was measured in each reconstruction to evaluate the quantitative impact of improved MR-based AC. Relative difference images between four- and six-compartment μ-maps were calculated. MR-based HUGE truncation correction was compared with the PET-based MLAA truncation correction method in all patients.

Results

Overall, 69 bone lesions were detected and evaluated. The mean increase in relative difference over all 69 lesions in SUV_max was 5.4 ± 6.4% when comparing the improved six-compartment AC with the standard four-compartment AC. Maximal relative difference of 28.4% was measured in one lesion. Truncation correction with HUGE worked robust and resulted in realistic body contouring in all 28 exams and for all 4 different radiotracers. Truncation correction with MLAA revealed overestimations of arm tissue volume in all PET/MR exams with ¹⁸F-FDG radiotracer and failed in all other exams with radiotracers ⁶⁸Ga-PSMA, ⁶⁸Ga-DOTATOC, and ¹²⁴I- MIBG due to limitations in body contour detection.

Conclusion

Improved MR-based AC, including bone segmentation and HUGE truncation correction in whole-body PET/MR on patients with bone lesions and using various radiotracers, is important to ensure best possible diagnostic image quality and accurate PET quantification. The HUGE method for truncation correction based on MR worked robust and results in realistic body contouring, independent of the radiotracers used.

中文翻译：

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使用各种放射性示踪剂评估全身PET / MR对骨转移患者改善的衰减校正的效果。

目的

这项研究评估了改进的基于MR的衰减校正（AC）的定量效果，其中包括在PET / MR全身混合成像中，特别是肿瘤转移和使用各种放射性示踪剂的PET / MR全身混合成像中的骨分割和HUGE截断校正方法。

方法

本研究纳入了总共进行了28次全身PET / MR检查并发现骨转移的23例患者。根据适当的临床指征，注射了不同的放射性示踪剂（¹⁸ F-FDG，⁶⁸ Ga-PSMA，⁶⁸ Ga-DOTATOC，¹²⁴ I–MIBG）。使用AC使用（1）标准四室μ-图（背景空气，肺，肌肉和软组织），（2）五室μ-图（添加骨骼），以及（3）六格μ-图（添加骨骼和巨大的截断校正）。SUV_最大在每次重建中测量每个检测到的骨病变的面积，以评估改进的基于MR的AC的定量影响。计算了四室和六室μ图之间的相对差异图像。在所有患者中，将基于MR的HUGE截断校正与基于PET的MLAA截断校正方法进行了比较。

结果

总体上，检测并评估了69个骨病变。当将改良的六室AC与标准四室AC进行比较时，SUV _max的全部69个病灶的相对差异的平均增加为5.4±6.4％。在一个病变中测得的最大相对差异为28.4％。使用HUGE进行截断校正的效果很好，并且在所有28项检查以及所有4种不同的放射性示踪剂中得出了逼真的人体轮廓。MLAA截断校正显示，在所有¹⁸ F-FDG放射性示踪剂的PET / MR检查中，手臂组织体积被高估，而在其他所有放射性示踪剂⁶⁸ Ga-PSMA，⁶⁸ Ga-DOTATOC和¹²⁴ I-MIBG检查中均未通过，原因是身体受到限制轮廓检测。

结论

改进的基于MR的AC，包括对患有骨病变的患者的全身PET / MR以及使用各种放射性示踪剂的全身分割和巨大的截断校正，对于确保最佳的诊断图像质量和准确的PET定量非常重要。基于MR的HUGE截断校正方法工作稳健，并实现了逼真的人体轮廓，与使用的放射性示踪剂无关。