Abstract
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Objectives To evaluate peritoneal carcinomatosis (PC) in patients (pts) with different primary tumors by diffusion-weighted (DW) MRI and 18F-FDG PET in correlation to histopathology.
Methods 43 pts with histologically proven PC underwent clinically indicated 18F-FDG PET/CT and immediately thereafter MR/PET of the abdomen with a new simultaneous whole-body MR/PET system (Biograph mMR, 3T, Siemens). Attenuation correction of MR/PET data was segmentation based with fat-water separation. In 22/43 pts measurable PC lesions >1.5 cm were selected for analysis. Patients with small-volume PC and examinations < 2 months after chemotherapy were excluded. In every patient up to 4 lesions were evaluated on co-registered MR/PET datasets by a manually placed 2D freehand ROI. For the analysis the minimum and mean apparent diffusion coefficient (ADC, b-values: 50, 800) and the maximum and mean standardized uptake value (SUV) were calculated. For correlation of ADC and SUV the Spearman’s rho was used, for comparison of groups the Wilcoxon test was applied.
Results The MR/PET images were of diagnostic quality in all patients. The analysis, based on 49 PC lesions in 20 patients, revealed a moderate but significant inverse correlation of ADC and SUV (SUVmax/ADCmin rho=-0,46, p=0,0008; SUVmean/ADCmean rho=-0,62, p<0,0001). The evaluation of histological subgroups displayed significant differences of ADC and SUV in peritoneal deposits of colorectal carcinoma and serous ovarian cancer. Two patients with mucinous ovarian cancer and signet ring carcinoma, respectively, displayed comparatively high ADC and low SUV values.
Conclusions The moderate correlation of ADC and SUV in PC suggests a rather complementary role of DWI and FDG-PET in this setting. The heterogeneity of water diffusivity and glucose metabolism in PC from different primary tumors has to be considered in image interpretation.
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