Autocontouring and Manual Contouring: Which Is the Better Method for Target Delineation Using ^sup 18^F-FDG PET/CT in Non-Small Cell Lung Cancer?

摘要

Previously, we showed that a CT window and level setting of 1,600 and -300 Hounsfield units, respectively, and autocontouring using an ^sup 18^F-FDG PET 50% intensity level correlated best with pathologic results. The aim of this study was to compare this autocontouring with manual contouring, to determine which method is better. Methods: Seventeen patients with non-small cell lung cancer underwent ^sup 18^F-FDG PET/CT before surgery. The maximum diameter on pathologic examination was determined. Seven sets of gross tumor volumes (GTVs) were defined. The first set (GTV^sub CT^) was contoured manually using only CT information. The second set (GTV^sub Auto^) was autocontoured using a 50% intensity level for ^sup 18^F-FDG PET images. The third set (GTV^sub Manual^) was manually contoured using a visual method on PET images. The other 4 sets combined CT and ^sup 18^F-FDG PET images fused to one another to become composite volumes: GTV^sub CT+Auto^, GTV^sub CT+Manual,^ GTV^sub CT-Auto^, and GTV^sub CT-Manual^. To quantitate the degree to which CT and ^sup 18^F-FDG PET defined the same region of interest, a matching index was calculated for each case. The maximum diameter of GTV was compared with the maximum diameter on pathologic examination. Results: The median GTV^sub CT^, GTV^sub Auto^, GTV^sub Manual^, GTV^sub CT+Auto^, GTV^sub CT+Manual^, GTV^sub CT-Auto^, and GTV^sub CT-Manual^ were 6.96, 2.42, 4.37, 7.46, 10.17, 2.21, and 3.38 cm^sup 3^, respectively. The median matching indexes of GTV^sub CT^ versus GTV^sub CT+Auto^, GTV^sub Auto^ versus GTV^sub CT+Auto^, GTV^sub CT^ versus GTV^sub CT+Manual^, and GTV^sub Manual^ versus GTV^sub CT+Manual^ were 0.86, 0.65, 0.88, and 0.81, respectively. Compared with the maximum diameter on pathologic examination, the correlations of GTV^sub CT^, GTV^sub Auto^, GTV^sub Manual^, GTV^sub CT+Auto^, and GTV^sub CT+Manual^ were 0.87, 0.83, 0.93, 0.86, and 0.94, respectively. Conclusion: The matching index was higher for manual contouring than for autocontouring using a 50% intensity level on ^sup 18^F-FDG PET images. When using a 50% intensity level to contour the target of non-small cell lung cancer, one should also consider using manual contouring of ^sup 18^F-FDG PET to check for any missed disease. [PUBLICATION ABSTRACT] Show less