Prospective Comparison of the Performance of MRI Versus CT in the Detection and Evaluation of Peritoneal Surface Malignancies

Abstract

Background: The performance of MRI versus CT in the detection and evaluation of peritoneal surface malignancies (PSM) remains unclear in the current literature. Our study is the first prospective study in an Asian center comparing the two imaging modalities, validated against intra-operative findings. Methods: A total of 36 patients with PSM eligible for CRS-HIPEC underwent both MRI and CT scans up to 6 weeks before the operation. The scans were assessed for the presence and distribution of PSM and scored using the peritoneal cancer index (PCI), which were compared against PCI determined at surgery. Results: Both MRI and CT were 100% sensitive and specific in detecting the overall presence of PSM. Across all peritoneal regions, the sensitivity and specificity for PSM detection was 49.1% and 93.0% for MRI, compared to 47.8% and 95.1% for CT (p = 0.76). MRI was more sensitive than CT for small bowel disease, although the difference did not reach statistical significance. Comparing PCI on imaging with intra-operative PCI, the mean difference was found to be −3.4 ± 5.4 (p < 0.01) for MRI, and −3.9 ± 4.1 (p < 0.01) for CT. The correlation between imaging and intra-operative PCI was poor, with a concordance coefficient of 0.76 and 0.79 for MRI and CT, respectively. Within individual peritoneal regions, there was also poor agreement between imaging and intra-operative PCI for both modalities, other than in regions 1 and 3. Conclusion: MRI and CT are comparable in the detection and evaluation of PSM. While sensitive in the overall detection of PSM, they are likely to underestimate the true disease burden.

Keywords: computed tomography; cytoreductive surgery; intraperitoneal chemotherapy; magnetic resonance imaging; peritoneal cancer index; peritoneal metastases.

Figure 1

Total peritoneal cancer index score by individual patient.

Figure 2

Agreement between imaging and intra-operative total peritoneal cancer index score. Scatterplot of (a) MRI and (b) CT against intra-operative score. Scatterplot of difference from intra-operative score for (c) MRI and (d) CT. Percentage change of (e) MRI and (f) CT score from intra-operative score by individual patients with 10% accuracy bound. p-values in (b,c) were based on paired t-test, testing whether mean differences were different from zero.

Figure 3

A 61-year-old female with mucinous appendiceal neoplasm, a small amount of fluid is noted within the lesser sac on (a) CT and (b) T2W MRI. Enhancement within the fluid, however, is barely appreciated on the (c) portal venous phase of the MRI, but becomes clearly apparent on the (d) delayed MRI.

Figure 4

A 55-year-old female with PMP. (a) CT reveals no significant abnormality, but MRI performed on the same day demonstrates a thin enhancing line surrounding the liver on the (b) portal venous phase, which becomes more apparent on the (c) delayed phase.

Figure 5

A 67-year-old male with metastatic colonic adenocarcinoma and gastric serosa peritoneal deposits. The deposits are not as well seen on (a) CT, as denoted by the white circle, but are more apparent on MRI, including the (b) T2W, (c) delayed, and (d) DWI sequences secondary to the superior soft tissue contrast.

Figure 6

A 61-year-old female with subtle recurrent primary peritoneal carcinoma, a tiny deposit is only well seen on the (b) DWI as a hyperintense focus at the falciform ligament (white arrow). A rim-enhancing nodule is barely seen on (a) CT, as well as the (c) portal venous and (d) delayed phases on MRI (white circles).

Figure 7

A 44-year-old male with recurrent mucinous appendiceal tumor; the hypodense fluid is not well seen on the (a) CT at Morrison’s pouch but easily seen on the (b) T2W MRI, where the fluid also appears to be loculated, suggestive of a tumor deposit as opposed to bland ascites. Similarly, the pocket of fluid among small bowel loops is not as well appreciated on (c) CT but is well seen on (d) T2W MRI.

Figure 8

The superior spatial resolution of (a) CT is demonstrated here as irregular soft tissue stranding within the greater omentum, which is not appreciated on (b) delayed and (c) DW-MRI performed on the same day.

Figure 9

A 63-year-old male with malignant epithelioid mesothelioma. An enhancing perihepatic nodule is well demarcated on (a) CT but not visualized on (b) T2W, (c) portal venous or (d) delayed phases on MRI performed on the same day, due to motion artifacts.

Figure 10

A fairly large soft tissue density peritoneal deposit is well seen on (a) CT, as it is surrounded by hypodense fat. Despite its large size, it is obscured on MRI with (b) delayed, (c) DWI, and (d) ADC sequences, primarily due to motion artifacts.