Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Feasibility of Diffusion Weighting with a Local Inside-Out Nonlinear Gradient Coil for Prostate MRI

Version 1 : Received: 23 November 2020 / Approved: 25 November 2020 / Online: 25 November 2020 (14:23:27 CET)
Version 2 : Received: 11 February 2021 / Approved: 12 February 2021 / Online: 12 February 2021 (08:51:40 CET)

How to cite: Bhuiyan, E.; Dewdney, A.; Weinreb, J.; Galiana, G. Feasibility of Diffusion Weighting with a Local Inside-Out Nonlinear Gradient Coil for Prostate MRI. Preprints 2020, 2020110647 (doi: 10.20944/preprints202011.0647.v1). Bhuiyan, E.; Dewdney, A.; Weinreb, J.; Galiana, G. Feasibility of Diffusion Weighting with a Local Inside-Out Nonlinear Gradient Coil for Prostate MRI. Preprints 2020, 2020110647 (doi: 10.20944/preprints202011.0647.v1).

Abstract

Purpose: Prostate cancer remains the 2nd 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 image quality is directly related to low gradient ampli-tudes, since weak gradients must be compensated with long echo times. Methods: We propose a new type of MRl 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 ADC maps diffusion 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 CNR 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.

Subject Areas

nonlinear gradients; diffusion imaging; prostate imaging

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