Diagnostic value of whole-body MRI with diffusion-weighted sequence for detection of peritoneal metastases in colorectal malignancy

Objective:To assess the diagnostic accuracy of whole-body MRI using diffusion-weighted sequence(WB-DWI)to determine the peritoneal cancer index(PCI)in correlation with surgical and histopathological findings.Methods:Twenty-seven patients underwent preoperative WB-MRI,followed by cytoreductive surgery for primary tumors of the appendix(n=15),colorectum(n=12),and associated peritoneal disease.A total of 351 regions were retrospectively reviewed.The sensitivity,specificity,and accuracy were calculated at 13 anatomical sites.The WB-DWI PCI and PCI type were compared with surgical and histopathological findings.Results:No statistical difference was found between the WB-DWI PCI and surgical PCI(P=0.574).WB-DWI correctly predicted the PCI type in 24 of 27 patients with high accuracy(88.9%),including 10 of 10 patients with small-volume tumor,12 of 14 with moderate-volume tumor,and 2 of 3 with large-volume tumor.WB-DWI correctly depicted tumors in 163 of 203 regions,with 40false-negative and 23 false-positive regions.The overall sensitivity,specificity,and accuracy of WB-DWI for the detection of peritoneal tumors were 80.3%,84.5%,and 82.1%,respectively.For lesions<0.5 cm in diameter,WB-DWI demonstrated good sensitivity(69.4%).Conclusions:WB-DWI accurately predicted PCI before surgery in patients undergoing evaluation for cytoreductive surgery.