Feasibility of diffusion weighting with a local inside‐out nonlinear gradient coil for prostate MRI. Issue 10 (24th September 2021)

• Record Type: Journal Article
• Authors: Hoque Bhuiyan, Enamul; Dewdney, Andrew; Weinreb, Jeffrey; Galiana, Gigi
• Is Part Of: Medical physics. Volume 48:Issue 10(2021)
• Page Start: 5804
• Page End: 5818
• Publication Date: 2021-09-24
• Subjects: apparent diffusion coefficient (ADC) -- diffusion‐weighted imaging (DWI) -- nonlinear gradient -- prostate cancer -- system design; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1002/mp.15100
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract: Purpose: Prostate cancer remains the second leading cancer killer of men, yet it is also a disease with a high rate of overtreatment. Diffusion‐weighted imaging (DWI) has shown promise as a reliable, grade‐sensitive imaging method, but it is limited by low image quality. Currently, DWI quality image is directly related to low gradient amplitudes, since weak gradients must be compensated with long echo times. Methods: We propose a new type of MRI accessory, an "inside‐out" and nonlinear gradient, whose sole purpose is to deliver diffusion encoding to a region of interest. Performance was simulated in OPERA and the resulting fields were used to simulate DWI with two‐compartment and kurtosis models. Experiments with a nonlinear head gradient prove the accuracy of DWI and apparent diffusion coefficient (ADC) maps encoded with nonlinear gradients. Results: Simulations validated thermal and mechanical safety while showing a 5‐ to 10‐fold increase in gradient strength over prostate. With these strengths, lesion contrast to noise ratio in ADC maps approximately doubled for a range of anatomical positions. Proof‐of‐principle experiments show that spatially varying b‐values can be corrected for accurate DWI and ADC. Conclusions: Dedicated nonlinear diffusion encoding hardware could improve prostate DWI.