Comparison between IGTVs based on ten phases of 4DCT and nine PET-CT SUV thresholds in primary thoracic esophageal cancer

Abstract

Objective To compare the volume,conformity index (CI),and degree of inclusion (DI) between internal gross tumor volumes (IGTVs) delineated based on ten phases of four-dimensional computed tomography (4DCT) and nine positron emission tomography (PET)-CT standardized uptake value (SUV) thresholds.Methods Fifteen patients with thoracic esophageal cancer sequentially underwent 3DCT,4DCT,and FDG PET-CT of the thorax simulation.IGTVs were delineated on ten phases of 4DCT images and then combined to obtain IGTV10.IGTVPET2.0,IGTVPET2.5,IGTVPET3.0,IGTVPET3.5,IGTVPET20％,IGTVPET25％,IGTVPET30％,IGTVPET35％,and IGTVPET40％ were delineated on PET images based on different SUV thresholds (≥2.0,2.5,3.0,and 3.5) and percentages of SUVmax (≥20％,25％,30％,35％,and 40％).The volume,CI,and DI were compared between IGTVs by paired t test.The correlations of centroid distance with CI and DI were determined by Pearson correlation analysis.Results The volumes of IGTVPET2.5 and IGTVPET20％ were similar to that of IGTV10,with volume ratios of 0.92(P =0.985) and 1.08 (P =0.886),respectively.The CIs of IGTVPET2.0 vs IGTV10,IGTVPET2.5 vs IGTV10,and IGTVPET20％ vs IGTV10 were similar (0.53,0.52,and 0.53 ; P =0.432,1.00,and 0.414),but they were significantly higher than the CIs of other IGTVPET vs IGTV10 (0.33-0.50,P =0.000-0.047).No significant differences existed between the DIs of IGTV10 in IGTVPET2.5 (0.67) and IGTV10 in IGTVPET20％ (0.70)(P =0.542) and between the DIs of IGTVPET2.5 in IGTV10 (0.74) and IGTVPET20％ in IGTV10 (0.72) (P=0.539).Conclusions IGTVPET2.5 and IGTVPET20％ have similar volumes and good spatial matching compared with IGTV10. Key words: Tomography, positron-emission, fluorodeoxyglucose ; Standardized uptake value; Tomography, X-ray computed, four-dimensional; Internal gross target volume; Esophageal neoplasms/radiotherapy