Total-liver-volume perfusion CT using 3-D image fusion to improve detection and characterization of liver metastases

The purpose of this study was to evaluate the feasibility of a total-liver-volume perfusion CT (CTP) technique for the detection and characterization of liver metastases. Twenty patients underwent helical CT of the total liver volume before and 11 times after intravenous contrast-material injection. To decrease distortion artifacts, all phases were co-registered using 3-D image fusion before creating blood-flow maps. Lesion-based sensitivity and specificity for liver metastases of first the conventional four phases (unenhanced, arterial, portal venous, and equilibrium) and later all 12 phases including blood-flow maps were determined as compared to intraoperative ultrasound and surgical exploration. Arterial and portal venous perfusion was calculated for normal-appearing and metastatic liver tissue. Total-liver-volume perfusion values were comparable to studies using single-level CTP. Compared to four-phase CT, total -liver-volume CTP increased sensitivity to 89.2 from 78.4% (P = 0.046) and specificity to 82.6 from 78.3% (P = 0.074). Total -liver-volume CTP is a noninvasive, quantitative, and feasible technique. Preliminary results suggest an improved detection of liver metastases for CTP compared to four-phase CT.