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

摘要

id="p-1">Previously, we showed that a CT window and level setting of 1,600 and -300 Hounsfield units, respectively, and autocontouring using an 18F-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 18F-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_CT) was contoured manually using only CT information. The second set (GTV_Auto) was autocontoured using a 50% intensity level for 18F-FDG PET images. The third set (GTV_Manual) was manually contoured using a visual method on PET images. The other 4 sets combined CT and 18F-FDG PET images fused to one another to become composite volumes: GTV_CT+Auto, GTV_CT+Manual, GTV_CTa?’Auto, and GTV_CT-Manual. To quantitate the degree to which CT and 18F-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_CT, GTV_Auto, GTV_Manual, GTV_CT+Auto, GTV_CT+Manual, GTV_CT-Auto, and GTV_CT-Manual were 6.96, 2.42, 4.37, 7.46, 10.17, 2.21, and 3.38 cm3, respectively. The median matching indexes of GTV_CT versus GTV_CT+Auto, GTV_Auto versus GTV_CT+Auto, GTV_CT versus GTV_CT+Manual, and GTV_Manual versus GTV_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_CT, GTV_Auto, GTV_Manual, GTV_CT+Auto, and GTV_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 18F-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 18F-FDG PET to check for any missed disease.