Kriwanek Florian, Ulbrich Leo, Lechner Wolfgang, Lütgendorf-Caucig Carola, Konrad Stefan, Waldstein Cora, Herrmann Harald, Georg Dietmar, Widder Joachim, Traub-Weidinger Tatjana, Rausch Ivo
Division of Nuclear Medicine, Department of Biomedical Imaging and Image Guided Therapy, Medical University of Vienna, 1090 Vienna, Austria.
Department of Radiation Oncology, Medical University of Vienna, 1090 Vienna, Austria.
Cancers (Basel). 2022 Sep 13;14(18):4435. doi: 10.3390/cancers14184435.
Aim: The aim of this study was to assess the effects of including somatostatin receptor agonist (SSTR) PET imaging in meningioma radiotherapy planning by means of changes in inter-observer variability (IOV). Further, the possibility of using threshold-based delineation approaches for semiautomatic tumor volume definition was assessed. Patients and Methods: Sixteen patients with meningioma undergoing fractionated radiotherapy were delineated by five radiation oncologists. IOV was calculated by comparing each delineation to a consensus delineation, based on the simultaneous truth and performance level estimation (STAPLE) algorithm. The consensus delineation was used to adapt a threshold-based delineation, based on a maximization of the mean Dice coefficient. To test the threshold-based approach, seven patients with SSTR-positive meningioma were additionally evaluated as a validation group. Results: The average Dice coefficients for delineations based on MRI alone was 0.84 ± 0.12. For delineation based on MRI + PET, a significantly higher dice coefficient of 0.87 ± 0.08 was found (p < 0.001). The Hausdorff distance decreased from 10.96 ± 11.98 mm to 8.83 ± 12.21 mm (p < 0.001) when adding PET for the lesion delineation. The best threshold value for a threshold-based delineation was found to be 14.0% of the SUVmax, with an average Dice coefficient of 0.50 ± 0.19 compared to the consensus delineation. In the validation cohort, a Dice coefficient of 0.56 ± 0.29 and a Hausdorff coefficient of 27.15 ± 21.54 mm were found for the threshold-based approach. Conclusions: SSTR-PET added to standard imaging with CT and MRI reduces the IOV in radiotherapy planning for patients with meningioma. When using a threshold-based approach for PET-based delineation of meningioma, a relatively low threshold of 14.0% of the SUVmax was found to provide the best agreement with a consensus delineation.
本研究旨在通过观察观察者间变异性（IOV）的变化，评估在脑膜瘤放射治疗计划中纳入生长抑素受体激动剂（SSTR）PET成像的效果。此外，还评估了使用基于阈值的划定方法进行半自动肿瘤体积定义的可能性。
5名放射肿瘤学家对16例接受分次放射治疗的脑膜瘤患者进行了划定。基于同时真相与性能水平估计（STAPLE）算法，通过将每个划定与共识划定进行比较来计算IOV。基于平均Dice系数最大化，使用共识划定来调整基于阈值的划定。为了测试基于阈值的方法，另外7例SSTR阳性脑膜瘤患者作为验证组进行了评估。
仅基于MRI的划定的平均Dice系数为0.84±0.12。基于MRI + PET的划定，发现Dice系数显著更高，为0.87±0.08（p < 0.001）。在病变划定中添加PET时，豪斯多夫距离从10.96±11.98毫米降至8.83±12.21毫米（p < 0.001）。发现基于阈值的划定的最佳阈值为SUVmax的14.0%，与共识划定相比，平均Dice系数为0.50±0.19。在验证队列中，基于阈值的方法的Dice系数为0.56±0.29，豪斯多夫系数为27.15±21.54毫米。
在CT和MRI的标准成像中加入SSTR-PET可降低脑膜瘤患者放射治疗计划中的IOV。在使用基于阈值的方法对基于PET的脑膜瘤进行划定时，发现相对较低的阈值SUVmax的14.0%与共识划定的一致性最佳。
