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Prostate diffusion MRI with minimal echo time using eddy current nulled convex optimized diffusion encoding
Author(s) -
Zhang Zhaohuan,
Moulin Kevin,
Aliotta Eric,
Shakeri Sepideh,
Afshari Mirak Sohrab,
Hosseiny Melina,
Raman Steven,
Ennis Daniel B.,
Wu Holden H.
Publication year - 2020
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.26960
Subject(s) - diffusion mri , effective diffusion coefficient , nuclear magnetic resonance , prostate cancer , prostate , nuclear medicine , signal to noise ratio (imaging) , image quality , imaging phantom , diffusion , spin echo , wilcoxon signed rank test , magnetic resonance imaging , medicine , physics , optics , radiology , computer science , artificial intelligence , mann–whitney u test , cancer , image (mathematics) , thermodynamics
Background Prostate diffusion‐weighted imaging (DWI) using monopolar encoding is sensitive to eddy‐current‐induced distortion artifacts. Twice‐refocused bipolar encoding suppresses eddy current artifacts, but increases echo time (TE), leading to lower signal‐to‐noise ratio (SNR). Optimization of the diffusion encoding might improve prostate DWI. Purpose To evaluate eddy current nulled convex optimized diffusion encoding (ENCODE) for prostate DWI with minimal TE. Study Type Prospective cohort study. Population A diffusion phantom, an ex vivo prostate specimen, 10 healthy male subjects (27 ± 3 years old), and five prostate cancer patients (62 ± 7 years old). Field Strength/Sequence 3T; single‐shot spin‐echo echoplanar DWI. Assessment Eddy‐current artifacts, TE, SNR, apparent diffusion coefficient (ADC), and image quality scores from three independent readers were compared between monopolar, bipolar, and ENCODE prostate DWI for standard‐resolution (1.6 × 1.6 mm 2 , partial Fourier factor [pF] = 6/8) and higher‐resolution protocols (1.6 × 1.6 mm 2 , pF = off; 1.0 × 1.0 mm 2 , pF = 6/8). Statistical Testing SNR and ADC differences between techniques were tested with Kruskal–Wallis and Wilcoxon signed‐rank tests ( P < 0.05 considered significant). Results Eddy current suppression with ENCODE was comparable to bipolar encoding (mean coefficient of variation across three diffusion directions of 9.4% and 9%). For a standard‐resolution protocol, ENCODE achieved similar TE as monopolar and reduced TE by 14 msec compared to bipolar, resulting in 27% and 29% higher mean SNR in prostate transition zone (TZ) and peripheral zone (PZ) ( P < 0.05) compared to bipolar, respectively. For higher‐resolution protocols, ENCODE achieved the shortest TE (67 msec), with 17–21% and 58–70% higher mean SNR compared to monopolar (TE = 77 msec) and bipolar (TE = 102 msec) in PZ and TZ ( P < 0.05). No significant differences were found in mean TZ ( P = 0.91) and PZ ADC ( P = 0.94) between the three techniques. ENCODE achieved similar or higher image quality scores than bipolar DWI in patients, with mean intraclass correlation coefficient of 0.77 for overall quality between three independent readers. Data Conclusion ENCODE minimizes TE (improves SNR) and reduces eddy‐current distortion for prostate DWI compared to monopolar and bipolar encoding. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:1526–1539.