Detection and characterization of liver lesions in patients with colorectal cancer with diffusion weighted MR imaging

Abstract

4071 Background: In patients with colorectal cancer detection and differentiation of liver metastases is important for further treatment decissions. Recently diffusion weighted MR imaging (DWI) was introduced as an new technique for liver tumor detection and characterzation. DWI is sensitive to molecular diffusion which is the random thermal motion of molecules (Brownian motion). MR imaging is the only method by which molecular diffusion processes can be evaluated in vivo. New techniques, such as breath-hold imaging or respiratory triggered single shot echo-planar-imaging (EPI) allow to extent DWI to abdominal organs, especially the liver. First results show that DWI can be used for the reliable detection of small subcentimeter liver lesions. We evaluated this new imaging method with regard to liver lesion detection and lesion characterization in patients with colorectal cancer. Methods: 115 consecutive patients with colorectal cancer and suspected liver metastases were evaluated with multi slice-CT and MRI at 1.5 Tesla using T1- and T2-weighted pulse sequences as well as DWI with respiratory triggered single shot echo-planar-imaging (EPI). Images were analyzed by two experienced radiologist blinded to the clinical results. Results for lesion detection for CT and DWI-MRI were compared using ROC analysis. Furthermore, in a subset of 60 patients diffusion coefficients (ADCs) were calculated for the differentiation of liver lesions (benign vs malignant). Results: For lesion detection ROC analysis showed superiority (p< 0.05) of DWI as compared to MS-CT. Especially metastases with diameters of smaller 1 cm were better detected with DWI-MRI as compared to MS-CT (p < 0.02). Results for differentiation show mean ADC-values of 1.24 for normal liver while malignant tumors have ADCs of 1.04–1.22 and benign lesions such as hemangiomas or cysts of 1.9 to 3.0, respectively. Furthermore, therapeutic changes were made in 20 % of patients based on DWI. Conclusions: MR imaging using DWI is more sensitive than multi- detector row CT in the detection and characterization of liver metatstases from colorectal cancer. Thus, it can be used as a new method for liver lesion detection and characterization as well as for optimal treatment planning. No significant financial relationships to disclose.