Department of Radiation Oncology, Fudan University Shanghai Cancer Center, China.
Radiother Oncol. 2013 Oct;109(1):71-6. doi: 10.1016/j.radonc.2013.08.033. Epub 2013 Sep 20.
Efficient tumor volume delineation by the combined use of PET/CT scanning is necessary for the proper treatment of non-small cell lung cancer (NSCLC). To understand the effect of variation in background intensity on PET-based gross tumor volume (GTV) delineation, we determined the background standard uptake values (SUVs) in normal lung, aorta (blood pool), and liver tissues and determined GTVs using different methods.
Thirty-seven previously untreated patients with pathologically confirmed NSCLC underwent PET/CT scanning with (18)F-fluorodeoxyglucose ((18)F-FDG). To obtain (18)F-FDG uptake values in normal tissues, regions of interest in the lung lobes (left upper, left lower, right upper, right middle, and right lower), aorta, and liver zones (left, intermediate, and right) were measured. The coefficient of variation (CV) of the SUV was measured for each normal structure. The CT-based GTV (GTV(CT)) was considered as the standard to which all PET-based GTVs were compared, and the correlation coefficient was analyzed to compare GTV obtained by the various delineation methods. Linear and logarithmic regression analyses were used to determine the relationship between GTV(CT) and GTV(PET).
Normal lung tissue showed a significantly lower SUV and less stability than tissue of the aorta or liver. For the lung, aorta, and liver, the maximum SUV (SUV(max)) was 0.82 ± 0.32, 2.35 ± 0.37, and 3.24 ± 0.50 (CV: 38.79%, 15.82%, and 15.30%) and average SUV (SUV(ave)) was 0.49 ± 0.18, 1.68 ± 0.32, and 2.34 ± 0.36 (CV: 36.38%, 18.92%, and 15.44%), respectively. The SUVs of the lung varied from lobe to lobe. The GTV delineation method using the SUV(ave) of the lung lobe in which the tumor was found as background in the source-to-background ratio (SBR) method showed the best correlation with the volume of CT-based GTV (r=0.81).
Our results show vast variation in the SUV among normal tissues, as well as in the different lung lobes. The tumor volume delineated using the SBR method correlated well with the CT-based tumor volume. We conclude that it is reasonable and precise to contour GTV in patients with NSCLC after taking into account the background intensity of the lung lobe in which the tumor is found.
通过联合使用 PET/CT 扫描，高效地对肿瘤体积进行描绘，这对于非小细胞肺癌（NSCLC）的恰当治疗是必要的。为了理解背景强度变化对基于 PET 的大体肿瘤体积（GTV）描绘的影响，我们测定了正常肺、主动脉（血池）和肝脏组织中的背景标准摄取值（SUV），并采用不同方法测定了 GTV。
37 例经病理证实的 NSCLC 患者接受了（18）F-氟代脱氧葡萄糖（（18）F-FDG）PET/CT 扫描。为了获得正常组织中的（18）F-FDG 摄取值，对肺叶（左肺上叶、左肺下叶、右肺上叶、右肺中叶和右肺下叶）、主动脉和肝脏区（左、中、右）进行了感兴趣区（ROI）测量。对每个正常结构的 SUV 变异系数（CV）进行了测量。将基于 CT 的 GTV（GTV（CT））作为标准，与所有基于 PET 的 GTV 进行了比较，并对各种描绘方法的相关系数进行了分析。采用线性和对数回归分析来确定 GTV（CT）与 GTV（PET）之间的关系。
与主动脉或肝脏组织相比，正常肺组织的 SUV 更低且稳定性更差。对于肺、主动脉和肝脏，最大 SUV（SUV（max））分别为 0.82±0.32、2.35±0.37 和 3.24±0.50（CV：38.79%、15.82%和 15.30%），平均 SUV（SUV（ave））分别为 0.49±0.18、1.68±0.32 和 2.34±0.36（CV：36.38%、18.92%和 15.44%）。肺的 SUV 会因肺叶的不同而有所差异。在源-背景比（SBR）方法中，采用肿瘤所在肺叶的 SUV（ave）作为背景的 GTV 描绘方法与基于 CT 的 GTV 体积的相关性最好（r=0.81）。
我们的结果表明，正常组织之间以及不同肺叶之间的 SUV 存在很大的差异。采用 SBR 方法描绘的肿瘤体积与基于 CT 的肿瘤体积很好地相关。我们得出的结论是，在考虑到肿瘤所在肺叶的背景强度后，对 NSCLC 患者的 GTV 进行描绘是合理且精确的。
