Multicentre analysis of blood flow values of normal liver in CT perfusion examinations of patients with colorectal cancer

Purpose: Despite CT perfusion (CTp) has already proved to be a useful tool in oncology, the lack of standardization prevents its use in the clinical practice, and especially using different equipment. In this multicentre study, we wanted to estimate to what extent using different CT machines can affect computation of perfusion values in normal liver. Methods and Materials: These patients belong to a large multicentre study on CTp (PIXEL). 30 patients (age range 46-85 years) with colorectal cancer, free from any liver disease, who did not develop liver metastases in the follow-up, underwent liver axial CTp in three Centres (10 patients each), with the same acquisition protocol. A large region of interest was drawn on one section, and voxel-based blood flow (BF) values were calculated using the same software. Mean BF values of each patient were computed and Tukey test (p-value≤0.05) was applied to evaluate whether Centres introduce variability on computation of the averaged perfusion values. Results: Mean BF (mL/min/100g) values for each Centre were 34.4±7.8, 38.4±9.9, 30.8±6.3, respectively, with ranges 22.8÷47.4, 26.4÷51.2, 21.4÷37.5. Statistical tests assessed that the mean perfusion values of the second and third Centre differ, and this difference was not to be attributed to within-patients variability. Conclusion: Perfusion values of normal liver in patients with colorectal cancer are often used as the “control” to check for the existence of predictive biomarkers. Despite using the same software, the preliminary results of this multicentre study suggest that a normalization has to be performed before comparing results between Centres.