Diffusivity in breast malignancies analyzed for b > 1000 s/mm<sup>2</sup> at 1 mm in‐plane resolutions: Insight from Gaussian and <scp>non‐Gaussian</scp> behaviors
Mārtiņš Otikovs, Noam Nissan, Edna Furman‐Haran, Debbie Anaby, Tanir M. Allweis, Ravit Agassi, Miri Sklair‐Levy, Lucio Frydman
Abstract
Abstract Diffusion‐weighted imaging (DWI) can improve breast cancer characterizations, but often suffers from low image quality –particularly at informative b > 1000 s/mm 2 values. The aim of this study was to evaluate multishot approaches characterizing Gaussian and non‐Gaussian diffusivities in breast cancer. This was a prospective study, in which 15 subjects, including 13 patients with biopsy‐confirmed breast cancers, were enrolled. DWI was acquired at 3 T using echo planar imaging (EPI) with and without zoomed excitations, readout‐segmented EPI (RESOLVE), and spatiotemporal encoding (SPEN); dynamic contrast‐enhanced (DCE) data were collected using three‐dimensional gradient‐echo T 1 weighting; anatomies were evaluated with T 2 ‐weighted two‐dimensional turbo spin‐echo. Congruence between malignancies delineated by DCE was assessed against high‐resolution DWI scans with b‐values in the 0–1800 s/mm 2 range, as well as against apparent diffusion coefficient (ADC) and kurtosis maps. Data were evaluated by independent magnetic resonance scientists with 3–20 years of experience, and radiologists with 6 and 20 years of experience in breast MRI. Malignancies were assessed from ADC and kurtosis maps, using paired t tests after confirming that these values had a Gaussian distribution. Agreements between DWI and DCE datasets were also evaluated using Sorensen–Dice similarity coefficients. Cancerous and normal tissues were clearly separable by ADCs: by SPEN their average values were (1.03 ± 0.17) × 10 −3 and (1.69 ± 0.19) × 10 −3 mm 2 /s ( p < 0.0001); by RESOLVE these values were (1.16 ± 0.16) × 10 −3 and (1.52 ± 0.14) × 10 −3 ( p = 0.00026). Kurtosis also distinguished lesions ( K = 0.64 ± 0.15) from normal tissues ( K = 0.45 ± 0.05), but only when measured by SPEN ( p = 0.0008). The best statistical agreement with DCE‐highlighted regions arose for SPEN‐based DWIs recorded with b = 1800 s/mm 2 (Sorensen–Dice coefficient = 0.67); DWI data recorded with b = 850 and 1200 s/mm 2 , led to lower coefficients. Both ADC and kurtosis maps highlighted the breast malignancies, with ADCs providing a more significant separation. The most promising alternative for contrast‐free delineations of the cancerous lesions arose from b = 1800 s/mm 2 DWI. Level of Evidence 2. Technical Efficacy Stage 3.