Commercial software upgrades may significantly alter Perfusion CT parameter values in colorectal cancer

Objective : To determine how commercial software platform upgrades impact on derived parameters for colorectal cancer. Materials and methods Following ethical approval, 30 patients with suspected colorectal cancer underwent Perfusion CT using integrated 64 detector PET/CT before surgery. Analysis was performed using software based on modified distributed parameter analysis (Perfusion software version 4; Perfusion 4.0), then repeated using the previous version (Perfusion software version 3; Perfusion 3.0). Tumour blood flow (BF), blood volume (BV), mean transit time (MTT) and permeability surface area product (PS) were determined for identical regions-of-interest. Slice-by-slice and ‘whole tumour’ variance was assessed by Bland-Altman analysis. Results : Mean BF, BV and PS was 20.4%, 59.5%, and 106% higher, and MTT 14.3% shorter for Perfusion 4.0 than Perfusion 3.0. The mean difference (95% limits of agreement) were +13.5 (−44.9 to 72.0), +2.61 (−0.06 to 5.28), −1.23 (−6.83 to 4.36), and +14.2 (−4.43 to 32.8) for BF, BV, MTT and PS respectively. Within subject coefficient of variation was 36.6%, 38.0%, 27.4% and 60.6% for BF, BV, MTT and PS respectively indicating moderate to poor agreement. Conclusion : Software version upgrades of the same software platform may result in significantly different parameter values, requiring adjustments for cross-version comparison.