Evaluation of the peritoneal carcinomatosis index with CT and MRI

Background The aim was to determine the incremental value of MRI compared with CT in the preoperative estimation of the peritoneal carcinomatosis index (PCI). Methods CT and MRI examinations of patients with peritoneal carcinomatosis were evaluated. CT images were first analysed by two observers who determined a first PCI (PCICT). Then, the two observers reviewed MRI examinations in combination with CT and determined a second PCI (PCICT + MRI). The sensitivity and negative predictive value of the two imaging sets were determined using surgery as a reference standard (PCIRef). Results CT plus MRI was more accurate in predicting the surgical PCI than CT alone. The absolute difference between PCICT + MRI and PCIRef was lower than that between PCICT and PCIRef (mean(s.d.) 3·96(4·10) versus 4·89(4·73); P = 0·010). The number of true‐positive findings increased from 106 to 125 for reader 1 and from 117 to 132 for reader 2 with the adjunct of MRI. For both readers, an increased sensitivity was obtained when both MRI and CT were used (from 63 to 81 per cent for reader 1; from 44 to 81 per cent for reader 2). The increase in sensitivity was greater for patients with a moderate volume of disease. Conclusion The combination of CT and MRI improved the preoperative estimation of PCI compared with CT alone. Combination useful