Diffusion volume (DV) measurement in endometrial and cervical cancer: A new MRI parameter in the evaluation of the tumor grading and the risk classification

A new MRI parameter representative of active tumor burden is proposed: diffusion volume (DV), defined as the sum of all the voxels within a tumor with apparent diffusion coefficient (ADC) values within a specific range. The aims of the study were:(a)to calculate DV on ADC maps in patients with cervical/endometrial cancer;(b)to correlate DV with histological grade(G)and risk classification;(c)to evaluate intra/inter-observer agreement of DV calculation. Fifty-three patients with endometrial(n=28)and cervical(n=25)cancers under-went pelvic MRI with DWI sequences.Both endometrial and cervical tumors were classified on the basis of G (G1/G2/G3) and FIGO staging (low/medium/high-risk). A semi-automated segmentation procedure was used to calculate the DV. A freehand closed ROI out- lined the whole visible tumor on the most representative slice of ADC maps defined as the slice with the maximum diameter of the solid neoplastic component. Successively,two thresholds were generated on the basis of the mean and standard deviation (SD) of the ADC values: lower threshold (LT = “mean minus three SD”)and higher threshold (HT = “mean plus one SD”).The closed ROI was expanded in 3D, including all the contiguous voxels with ADC values in the range LT-HT × 10–3 mm2 /s. A Kruskal–Wallis test was used to assess the differences in DV among G and risk groups. Intra-/inter-observer variability for DV measurement was analyzed according to the method of Bland and Altman and the intraclass-correlation–coefficient (ICC). DV is an accurate index for the assessment of G and risk classification of cervical/endometrial cancers with low intra-/inter-observer variability.