Strong-Gradient Diffusion-Weighted Imaging of Prostate Cancer Using an Inside-Out Nonlinear Gradient Coil

Area of Science:

• Magnetic Resonance Imaging
• Medical Physics
• Radiology

Background:

• Prostate diffusion-weighted imaging (DWI) is crucial for detecting prostate cancer.
• Current DWI techniques can be limited by image quality and lesion conspicuity.
• Advanced gradient coil technology may overcome these limitations.

Purpose of the Study:

• To evaluate an inside-out nonlinear gradient coil for enhanced prostate DWI.
• To assess improvements in image quality, lesion conspicuity, and signal-to-noise ratio (SNR).
• To validate apparent diffusion coefficient (ADC) map accuracy.

Main Methods:

• Developed and applied an inside-out nonlinear gradient coil for DWI with Echo Planar Imaging (EPI) readout.
• Investigated and corrected for geometric distortion and eddy currents.
• Acquired DWI data using protocols with b_max=1000 and 3000 s/mm², minimizing echo time (TE).
• Compared nonlinear gradient results with linear gradient acquisitions in volunteers and patients.

Main Results:

• Nonlinear gradient DWI showed reduced artifacts after corrections.
• Apparent diffusion coefficient (ADC) maps demonstrated good agreement between linear and nonlinear gradients.
• Significantly reduced echo time (TE) from 57-72 ms to 42-54 ms.
• Increased signal-to-noise ratio (SNR) by 3%-38% (median 16-26%).
• Improved lesion contrast-to-noise ratio (CNR) by a median of 133-217% and lesion-to-normal-tissue contrast ratio by 23%.

Conclusions:

• The inside-out nonlinear gradient coil significantly enhances prostate DWI quality.
• This technology improves lesion conspicuity and SNR, aiding in prostate cancer detection.
• The method offers a promising advancement for clinical prostate MRI.