Tibdewal Anil, Patil Mangesh, Misra Shagun, Purandare Nilendu, Rangarajan Venkatesh, Mummudi Naveen, Karimundackal George, Jiwnani Sabita, Agarwal Jaiprakash
Department of Radiation Oncology, Tata Memorial Hospital, Homi Bhabha National Institute, Mumbai, Maharashtra, India.
Department of Nuclear Medicine, Tata Memorial Hospital, Homi Bhabha National Institute, Mumbai, Maharashtra, India.
Indian J Nucl Med. 2021 Jan-Mar;36(1):7-13. doi: 10.4103/ijnm.IJNM_134_20. Epub 2021 Mar 4.
Incorporating F-fluorodeoxyglucose positron emission tomography-computed tomography (F-FDG-PET/CT) for gross tumor volume (GTV) delineation is challenging due to varying tumor edge based on the set threshold of the standardized uptake value (SUV). This study aims to determine an optimal SUV threshold that correlates best with the pathological tumor size.
From January 2013 to July 2014, 25 consecutive patients of operable nonsmall-cell lung cancer (NSCLC) who underwent stagingF-FDG-PET/CT before surgical resection were included in the test cohort and 12 patients in the validation cohort. GTVs were delineated on the staging PET/CT by automatic delineation using various percentage threshold of maximum SUV (SUVmax) and absolute SUV. The maximum pathological tumor diameter was then matched with the maximum auto-delineated tumor diameter with varying SUV thresholds. First-order linear regression and Bland-Altman plots were used to obtain an optimal SUV threshold for each patient. Three radiation oncologists with varying degrees of experiences also delineated GTVs with the visual aid of PET/CT to assess interobserver variation in delineation.
In the test set, the mean optimal percentage threshold for GTV was SUVmax of 35.6%±18.6% and absolute SUV of 4.35 ± 1.7. In the validation set, the mean optimal percentage threshold SUV and absolute SUV were 36.9 ± 16.9 and 4.1 ± 1.6, respectively. After a combined analysis of all 37 patients, the mean optimal threshold was 36% ± 17.9% and 4.27 ± 1.7, respectively. Using Bland-Altman plots, auto-contouring with 40% SUVmax and SUV 4 was in greater agreement with the pathological tumor diameter.
Automatic GTV delineation on PETCT in NSCLC with percentage threshold SUV of 40% and absolute SUV of 4 correlated best with pathological tumor size. Auto-contouring using these thresholds will increase the precision of radiotherapy contouring of GTV and will save time.
由于基于标准化摄取值（SUV）设定的阈值不同，肿瘤边缘各异，因此将氟脱氧葡萄糖正电子发射断层扫描 - 计算机断层扫描（F-FDG-PET/CT）纳入大体肿瘤体积（GTV）勾画具有挑战性。本研究旨在确定与病理肿瘤大小相关性最佳的最佳SUV阈值。
2013年1月至2014年7月，将25例手术切除前接受分期F-FDG-PET/CT检查的可手术切除的非小细胞肺癌（NSCLC）患者纳入测试队列，12例患者纳入验证队列。通过使用最大SUV（SUVmax）和绝对SUV的各种百分比阈值进行自动勾画，在分期PET/CT上勾画GTV。然后将最大病理肿瘤直径与具有不同SUV阈值的最大自动勾画肿瘤直径进行匹配。使用一阶线性回归和Bland-Altman图为每位患者获得最佳SUV阈值。三位经验程度不同的放射肿瘤学家也借助PET/CT的视觉辅助来勾画GTV，以评估勾画过程中的观察者间差异。
在测试集中，GTV的平均最佳百分比阈值为SUVmax 35.6%±18.6%，绝对SUV为4.35±1.7。在验证集中，平均最佳百分比阈值SUV和绝对SUV分别为36.9±16.9和4.1±1.6。对所有37例患者进行综合分析后，平均最佳阈值分别为36%±17.9%和4.27±1.7。使用Bland-Altman图，SUVmax 40%和SUV 4的自动轮廓与病理肿瘤直径的一致性更高。
在NSCLC的PETCT上，SUV百分比阈值为40%且绝对SUV为4时自动勾画GTV与病理肿瘤大小的相关性最佳。使用这些阈值进行自动轮廓勾画将提高GTV放射治疗轮廓勾画的精度并节省时间。
