Anderson Carryn M, Sun Wenqing, Buatti John M, Maley Joan E, Policeni Bruno, Mott Sarah L, Bayouth John E
Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA.
Department of Radiology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA.
Jacobs J Radiat Oncol. 2014 Sep;1(1):006.
To compare the interobserver and intermodality differences in image-based identification of head and neck primary site gross tumor volumes (GTV). Modalities compared include: contrast-enhanced CT, F-18 fluorodeoxyglucose positron emission tomography (PET/CT) and contrast-enhanced MRI.
Fourteen patients were simulated after immobilization for all 3 imaging modalities (CT, PET/CT, MRI). Three radiation oncologists (RO) contoured GTVs as seen on each modality. The GTV was contoured first on the contrast-enhanced CT (considered the standard), then on PET/CT, and finally on post-contrast T1 MRI. Interobserver and intermodality variability were analyzed by volume, intersection, union, and volume overlap ratio (VOR).
Analysis of RO contours revealed the average volume for CT-, PET/CT-, and MRI-derived GTVs were 45cc, 35cc and 49cc, respectively. In 93% of cases PET/CT-derived GTVs had the smallest volume and in 57% of cases MRI-derived GTVs had the largest volume. CT showed the largest variation in target definition (standard deviation amongst observers 35%) compared to PET/CT (28%) and MRI (27%). The VOR was largest (indicating greatest interobserver agreement) in PET/CT (46%), followed by MRI (36%), followed by CT (34%). For each observer, the least agreement in GTV definition occurred between MRI & PET/CT (average VOR = 41%), compared to CT & PET/CT (48%) and CT & MRI (47%).
A nonsignificant interobserver difference in GTVs for each modality was seen. Among three modalities, CT was least consistent, while PET/CT-derived GTVs had the smallest volumes and were most consistent. MRI combined with PET/CT provided the least agreement in GTVs generated. The significance of these differences for head & neck cancer is important to explore as we move to volume-based treatment planning based on multi-modality imaging as a standard method for treatment delivery.
比较头颈部原发部位大体肿瘤体积（GTV）基于图像识别的观察者间差异和模态间差异。所比较的模态包括：增强CT、F-18氟脱氧葡萄糖正电子发射断层扫描（PET/CT）和增强MRI。
14例患者在固定后接受了所有3种成像模态（CT、PET/CT、MRI）的模拟。3名放射肿瘤学家（RO）勾勒出每种模态下所见的GTV。首先在增强CT上勾勒GTV（视为标准），然后在PET/CT上，最后在增强后T1 MRI上。通过体积、交集、并集和体积重叠率（VOR）分析观察者间和模态间的变异性。
对RO勾勒结果的分析显示，CT、PET/CT和MRI得出的GTV平均体积分别为45cc、35cc和49cc。在93%的病例中，PET/CT得出的GTV体积最小，在57%的病例中，MRI得出的GTV体积最大。与PET/CT（28%）和MRI（27%）相比，CT在靶区定义上的变化最大（观察者间标准差为35%）。PET/CT的VOR最大（表明观察者间一致性最高），为46%，其次是MRI（36%），然后是CT（34%）。对于每位观察者，GTV定义在MRI和PET/CT之间的一致性最低（平均VOR = 41%），相比之下，CT和PET/CT之间为48%，CT和MRI之间为47%。
每种模态的GTV观察者间差异无统计学意义。在三种模态中，CT最不一致，而PET/CT得出的GTV体积最小且最一致。MRI与PET/CT结合得出的GTV一致性最低。随着我们转向基于多模态成像的基于体积的治疗计划作为标准治疗交付方法，探索这些差异对头颈部癌的意义很重要。
