Semi-automated quantitative intravoxel incoherent motion analysis and its implementation in breast diffusion-weighted imaging

BackgroundTo optimize and validate intravoxel incoherent motion (IVIM) modeled diffusion-weighted imaging (DWI) compared with the apparent diffusion coefficient (ADC) for semi-automated analysis of breast lesions using a multi-reader setup.

Materials and MethodsPatients (n=176) with breast lesions (1cm) and known pathology were prospectively examined (1.5 Tesla) with DWI (b=0, 50, 200, 500, 800, 1000 s/mm(2)) between November 2008 and July 2014 and grouped into a training and test set. Three independent readers applied a semi-automated procedure for setting regions-of-interest for each lesion and recorded ADC and IVIM parameters: molecular diffusion (D-slow), microperfusion (D-fast), and the fraction of D-fast (f(fast)). In the training set (24 lesions, 12 benign), a semi-automated method was optimized to yield maximum true negatives (TN) with minimal false negatives (FN): only the optimal fraction (Fo) of voxels in the lesions was used and optimal thresholds were determined. The optimal Fo and thresholds were then applied to a consecutive test set (139 lesions, 23 benign) to obtain specificity and sensitivity.

ResultsIn the training set, optimal thresholds were 1.44x10(-3) mm(2)/s (D-slow), 18.55x10(-3) mm(2)/s (D-fast), 0.247 (f(fast)) and 2.00x10(-3) mm(2)/s (ADC) with Fo set to 0.61, 0.85, 1.0, and 1.0, respectively, this resulted in TN=5 (IVIM) and TN=1 (ADC), with FN=0. In the test set, sensitivity and specificity among the readers were 90.5-93.1% and 43.5-52.2%, respectively, for IVIM, and 94.8-95.7% and 13.0-21.7% for ADC (P0.0034) without inter-reader differences (P=1.000).

ConclusionThe presented semi-automated method for breast lesion evaluation is reader independent and yields significantly higher specificity for IVIM compared with the ADC. J. Magn. Reson. Imaging 2016;43:1122-1131.