Delineation of tumorous tissue in peritoneal metastases using diffusion-weighted imaging

This journal suppl. entitled: Book of Abstracts ESMRMB 2015 (e-only)PURPOSE/INTRODUCTION: The accurate detection of peritoneal metastases is vital in treatment planning and outcome evaluation1. The additional metabolic and functional information provided by diffusion weighted imaging (DWI) compared to conventional MR imaging make the segmentation of tumor more effective2. The aim of this study is to propose an alternative tumorous tissue delineation method by virtue of tissue segmentation using apparent diffusion coefficient (ADC). SUBJECTS AND METHODS: In the eighteen homogeneous lesions identified from six patients with peritoneal metastases, gross tumor volume (GTV) was estimated from manually drawn volume-of-interest (VOI) on diffusion-weighted (DW) images (GTVADC). Within each VOI, K-means clustering was performed to delineate timorous tissue with high cellularity. The volume of tumor with high cellularity obtained from ADC map alone (HCTVADC) as well as that obtained from both non-diffusion-weighted (b0) image and ADC maps (HCTVb0+ADC) were estimated. GTVADC, HCTVADC and HCTVb0+ADC were compared with metabolic tumor volume (MTV) obtained from PET/CT using a threshold of 45 % of the maximum standard uptake value (SUV) of individual patient. RESULTS: GTVADC (p = 0.004) and HCTVb0+ADC (p = 0.001) were statistically different from MTV. No significant difference was found between HCTVADC and MTV (p = 0.729). HCTVADC also showed a high agreement with MTV (intraclass correlation coefficient = 0.99). DISCUSSION/CONCLUSION: ADC is a potential alternative to PET/CT in differentiating tumorous tissues with high cellularity in metastases that are homogeneous in nature. References: 1. Low RN: MR imaging of the peritoneal spread of malignancy. Abdom Imaging; 32:267–83. 2. Soussan M, Des Guetz G, Barrau V, et al. Comparison of FDGPET/CT and MR with diffusion-weighted imaging for assessing peritoneal carcinomatosis from gastrointestinal malignancy. Eur Radiol 2012;22:1479–87. doi:10.1007/s00330-012-2397-2