Diffusion-weighted imaging (DWI) of breast lesions is usually quantified using a mono-exponential model such as the apparent diffusion coefficient (ADC) or a bi-exponential model such as intravoxel incoherent motion (IVIM), the latter quantifying molecular diffusion more accurately and additionally providing microperfusion properties of breast lesions [1-3]. Both the ADC and IVIM have been deployed to discriminate benign from malignant lesions using different strategies. Recently, increased diagnostic performance of IVIM was found compared to the ADC, and increased sensitivity was suggested when combining information of molecular...

Twenty-eight consecutive patients with breast lesions ≥ 1 cm were examined with 1.5T DWI (b=0,50,200,500,800,1000 s/mm2) between July 2012 and June 2013. Lesions were classified by histopathology or follow-up and non-mass lesions were excluded. Offline IVIM voxel-by-voxel analysis (Matlab, The Mathworks, Natick, MA, USA) yielded molecular diffusion (Dslow), microperfusion (Dfast) and respective fractions (fslow/fast) using equation 1 (Fig. 1). For each lesion, voxels were selected by drawing a large ROI around each lesion on the b = 0 s/mm2 DWI image (Fig. 2). Then, Dslow,...

Twenty-four breast mass lesions were found: 10 benign (fibroadenoma/adenosis) and 14 malignant (12 IDCs; 1 ILC; 1 Plyllodes). Malignancy was correctly identified when using the following decision algorithm and optimized thresholds: Dslow < 1.58x10-3 mm2/s AND Dfast < 0.068 mm2/s AND ffast < 66.5%; otherwise benign. Optimal discrimination was obtained when respectively 70%, 10% and 2% of the highest voxel values within the ROI were analyzed. All lesions were correctly identified as benign or malignant (Fig. 3).

In conclusion, this preliminary study demonstrates the design of a diagnostic test to differentiate benign from malignant breast mass lesions with minimal false negative outcomes by combining all three IVIM parameters in a single test. A prospective study should establish the sensitivity and specificity of this new approach.

Hildebrand Dijkstra, MSc works as a Medical Physicist in the department of Radiology of the University Medical Center Groningen (UMCG) in The Netherlands. Besides that, he is affiliated with the Center of Medical Imaging - North East Netherlands (CMI-NEN) as a PhD student in the field of Diffusion Weighted Imaging and post-processing. E-mail: [email protected]

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