Diffusion-weighted MRI of metastatic liver lesions: is there a difference between hypervascular and hypovascular metastases?

Abstract

Background Different perfusion characteristics and histopathologic features of liver metastasis may potentially lead to different diffusion-weighted magnetic resonance imaging (DW-MRI) characteristics which can affect the performance of DW-MRI in their diagnosis. Purpose To compare ADC values of hypervascular and hypovascular metastases and the added value of DW-MRI to T2-weighted (T2-w) images in their detection. Material and Methods In this retrospective study, 46 patients (21 with hypervascular, 25 with hypovascular liver metastases) who had undergone abdominal MRI were included. Two independent observers first reviewed T2-w images only and then T2-w + DW-MR images and recorded number of metastases in each session. Lesion detection rate was compared using McNemar test. ADC of metastases in each patient was measured and compared between hypo- and hypervascular lesions using t-test. Results A total of 153 hypervascular and 187 hypovascular metastases were detected at consensus review. Two observers detected significantly more hypervascular metastases on T2-w + DW-MR image review session compared to T2-w image only review session (reader 1: 148 [96.7%] vs. 129 [84.3%], P = 0.002; reader 2: 125 [81.9%] vs. 113 [73.8%], P = 0.004). Detection rate of hypovascular metastases was similar between two sessions for both observers (reader 1: 180 [96.2%] vs. 184 [98.4%]; reader 2: 176 [94.1%] vs. 180 [96.2%], P > 0.05). The mean ADC value of hypervascular metastases was significantly lower than mean ADC value of hypovascular metastases (1.23+/−0.31 × 10−3 mm2/s vs. 1.49+/−0.19 × 10−3 mm2/s) ( P = 0.001). Conclusion Liver metastases are not a homogenous group of lesions with uniform DW-MRI features. Hypervascular metastases demonstrate significantly lower ADC values compared to hypovascular metastases. DW-MRI improved detection of hypervascular metastases compared to T2-w images alone and is a useful adjunct to T2-w images for their detection.