Quantitative Evaluation of Segmentation- and Atlas-Based Attenuation Correction for PET/MR on Pediatric Patients
Quantitative Evaluation of Segmentation- and Atlas-Based Attenuation Correction for PET/MR on Pediatric Patients
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DOI：
10.2967/jnumed.114.149476
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发表时间：
2015-07-01
影响因子：
9.3
通讯作者：
Pichler, Bernd J.
中科院分区：
文献类型：
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作者：
Bezrukov, Ilja;Schmidt, Holger;Pichler, Bernd J.
儿科成像被认为是组合PET/MR成像系统的关键应用。由于现有的基于MR的衰减校正方法不是专门为儿科患者设计的，因此我们评估了2个潜在影响因素的影响：衰减系数的患者间和患者内变异性以及解剖变异性。此外，我们使用成人和儿科图谱（分别为SEGwBONEad和SEGwBONEpe）对儿科患者的PET数据评价了3种基于MR的衰减校正方法（不使用SEGbase）和使用骨预测的定量准确性。研究方法：根据不同组织类型的CT数据集中的感兴趣体积（VOI），评估了儿科（5-17岁，n = 17）和成人（27-66岁，n = 16）患者群体之间和内部衰减系数的变异性。通过计算骨组织、肺和软组织区域基于CT的衰减图的平均差异，在SEGwBONEad/pe衰减图上评估解剖变异性。对具有生理性摄取的VOI和具有胸部和腹部/骨盆中升高的摄取的80%等轮廓VOI进行PET定量评价。评估了每个VOI组和方法的患者间和患者内偏倚变异性。结果如下：在肺和股骨中，发现成人和儿童集体之间的平均VOI Hounsfield单位值和线性衰减系数存在统计学显著差异。使用儿科图谱预测衰减图显示骨组织误差减少，骨结构描绘更好。PET定量准确性评价显示，在SEGbase生理摄取的情况下，骨髓和股骨相邻VOI的平均标准化摄取值的平均误差为-14% +/- 5%和-23% +/- 6%，具有统计学显著性，使用SEGwBONEpe衰减图可将其降低至0% +/- 4%和-1% +/- 5%。所有方法的软组织VOI偏倚均小于5%。肺VOI显示所有方法的高SD在15%的范围内。对于摄取升高的VOI，除胸部外，平均值和SD均小于5%。结论：使用儿科患者专用图谱可改善骨区域的衰减图预测，并降低股骨相邻VOI的患者间偏倚变化。对于肺部，其中儿科集体的患者内变化较高，患者或组特异性衰减系数可能会提高衰减图的准确性。当忽略骨组织时，骨髓和股骨相邻VOI中-14%和-23%的平均误差会影响这些区域的PET定量。
Pediatric imaging is regarded as a key application for combined PET/MR imaging systems. Because existing MR-based attenuation-correction methods were not designed specifically for pediatric patients, we assessed the impact of 2 potentially influential factors: inter- and intrapatient variability of attenuation coefficients and anatomic variability. Furthermore, we evaluated the quantification accuracy of 3 methods for MR-based attenuation correction without (SEGbase) and with bone prediction using an adult and a pediatric atlas (SEGwBONEad and SEGwBONEpe, respectively) on PET data of pediatric patients. Methods: The variability of attenuation coefficients between and within pediatric (5-17 y, n = 17) and adult (27-66 y, n = 16) patient collectives was assessed on volumes of interest (VOIs) in CT datasets for different tissue types. Anatomic variability was assessed on SEGwBONEad/pe attenuation maps by computing mean differences to CT-based attenuation maps for regions of bone tissue, lungs, and soft tissue. PET quantification was evaluated on VOIs with physiologic uptake and on 80% isocontour VOIs with elevated uptake in the thorax and abdomen/pelvis. Inter- and intrapatient variability of the bias was assessed for each VOI group and method. Results: Statistically significant differences in mean VOI Hounsfield unit values and linear attenuation coefficients between adult and pediatric collectives were found in the lungs and femur. The prediction of attenuation maps using the pediatric atlas showed a reduced error in bone tissue and better delineation of bone structure. Evaluation of PET quantification accuracy showed statistically significant mean errors in mean standardized uptake values of -14% +/- 5% and -23% +/- 6% in bone marrow and femur-adjacent VOIs with physiologic uptake for SEGbase, which could be reduced to 0% +/- 4% and -1% +/- 5% using SEGwBONEpe attenuation maps. Bias in soft-tissue VOIs was less than 5% for all methods. Lung VOIs showed high SDs in the range of 15% for all methods. For VOIs with elevated uptake, mean and SD were less than 5% except in the thorax. Conclusion: The use of a dedicated atlas for the pediatric patient collective resulted in improved attenuation map prediction in osseous regions and reduced interpatient bias variation in femur-adjacent VOIs. For the lungs, in which intrapatient variation was higher for the pediatric collective, a patient- or group-specific attenuation coefficient might improve attenuation map accuracy. Mean errors of -14% and -23% in bone marrow and femur-adjacent VOIs can affect PET quantification in these regions when bone tissue is ignored.