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

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Abstract

Background:

To 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 Methods:

Patients (n = 176) with breast lesions (≥1 cm) and known pathology were prospectively examined (1.5 Tesla) with DWI (b = 0, 50, 200, 500, 800, 1000 s/mm2) 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 (Dslow), microperfusion (Dfast), and the fraction of Dfast (ffast). 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.

Results:

In the training set, optimal thresholds were 1.44 × 10−3 mm2/s (Dslow), 18.55 × 10−3 mm2/s (Dfast), 0.247 (ffast) and 2.00 × 10−3 mm2/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 (P ≤ 0.0034) without inter-reader differences (P = 1.000).

Conclusion:

The 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.

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