Visser Eric P, Philippens Mariëlle E P, Kienhorst Laura, Kaanders Johannes H A M, Corstens Frans H M, de Geus-Oei Lioe-Fee, Oyen Wim J G
Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
J Nucl Med. 2008 Jun;49(6):892-8. doi: 10.2967/jnumed.107.049585. Epub 2008 May 15.
Tumor delineation using noninvasive medical imaging modalities is important to determine the target volume in radiation treatment planning and to evaluate treatment response. It is expected that combined use of CT and functional information from 18F-FDG PET will improve tumor delineation. However, until now, tumor delineation using PET has been based on static images of 18F-FDG standardized uptake values (SUVs). 18F-FDG uptake depends not only on tumor physiology but also on blood supply, distribution volume, and competitive uptake processes in other tissues. Moreover, 18F-FDG uptake in tumor tissue and in surrounding healthy tissue depends on the time after injection. Therefore, it is expected that the glucose metabolic rate (MRglu) derived from dynamic PET scans gives a better representation of the tumor activity than does SUV. The aim of this study was to determine tumor volumes in MRglu maps and to compare them with the values from SUV maps.
Twenty-nine lesions in 16 dynamic 18F-FDG PET scans in 13 patients with non-small cell lung carcinoma were analyzed. MRglu values were calculated on a voxel-by-voxel basis using the standard 2-compartment 18F-FDG model with trapping in the linear approximation (Patlak analysis). The blood input function was obtained by arterial sampling. Tumor volumes were determined in SUV maps of the last time frame and in MRglu maps using 3-dimensional isocontours at 50% of the maximum SUV and the maximum MRglu, respectively.
Tumor volumes based on SUV contouring ranged from 1.31 to 52.16 cm3, with a median of 8.57 cm3. Volumes based on MRglu ranged from 0.95 to 37.29 cm3, with a median of 3.14 cm3. For all lesions, the MRglu volumes were significantly smaller than the SUV volumes. The percentage differences (defined as 100% x (V MRglu - V SUV)/V SUV, where V is volume) ranged from -12.8% to -84.8%, with a median of -32.8%.
Tumor volumes from MRglu maps were significantly smaller than SUV-based volumes. These findings can be of importance for PET-based radiotherapy planning and therapy response monitoring.
使用非侵入性医学成像模态进行肿瘤勾画对于确定放射治疗计划中的靶区体积以及评估治疗反应非常重要。预计将CT与18F-FDG PET的功能信息联合使用会改善肿瘤勾画。然而，到目前为止，使用PET进行肿瘤勾画一直基于18F-FDG标准化摄取值（SUV）的静态图像。18F-FDG摄取不仅取决于肿瘤生理学，还取决于血液供应、分布容积以及其他组织中的竞争性摄取过程。此外，肿瘤组织和周围健康组织中的18F-FDG摄取取决于注射后的时间。因此，预计从动态PET扫描得出的葡萄糖代谢率（MRglu）比SUV能更好地反映肿瘤活性。本研究的目的是确定MRglu图中的肿瘤体积并将其与SUV图中的值进行比较。
分析了13例非小细胞肺癌患者的16次动态18F-FDG PET扫描中的29个病灶。使用标准的两室18F-FDG模型并采用线性近似下的捕获法（Patlak分析）逐体素计算MRglu值。通过动脉采样获得血液输入函数。分别使用最大SUV和最大MRglu的50%处的三维等轮廓线在最后一个时间帧的SUV图和MRglu图中确定肿瘤体积。
基于SUV轮廓勾画的肿瘤体积范围为1.31至52.16 cm³，中位数为8.57 cm³。基于MRglu的体积范围为0.95至37.29 cm³，中位数为3.14 cm³。对于所有病灶，MRglu体积显著小于SUV体积。百分比差异（定义为100%×(V MRglu - V SUV)/V SUV，其中V为体积）范围为-12.8%至-84.8%，中位数为-32.8%。
MRglu图中的肿瘤体积显著小于基于SUV的体积。这些发现对于基于PET的放射治疗计划和治疗反应监测可能具有重要意义。
