A diffusion-prepared reduced FOV sequence for prostate MRI near metallic implants

Area of Science:

• Radiology
• Medical Imaging
• Prostate Cancer Diagnostics

Background:

• Metallic total hip replacements (THRs) cause artifacts in standard diffusion-weighted imaging (DWI) for prostate MRI.
• Echo Planar Imaging (EPI), commonly used for DWI, is particularly susceptible to distortion and signal dropout near THRs.

Purpose of the Study:

• To develop a diffusion-weighted imaging (DWI) sequence for prostate cancer screening in patients with metallic total hip replacements (THRs).
• To achieve clinically feasible scan times while avoiding artifacts common with conventional Echo Planar Imaging (EPI).

Main Methods:

• A reduced field of view (FOV) diffusion-prepared sequence utilizing high radiofrequency (RF) bandwidth pulses and stimulated echo pathways was developed.
• Slice-select gradient reversal created a reduced FOV, and a 3D RF-spoiled gradient echo readout imaged the prepared magnetization.
• The sequence was validated in phantoms, healthy volunteers (with/without THRs), and patients undergoing prostate MRI.

Main Results:

• The proposed sequence demonstrated robustness against shading and distortion artifacts in the presence of off-resonance, unlike standard DWI-EPI.
• Apparent diffusion coefficient (ADC) estimates from the new sequence were comparable to those from conventional DWI-EPI.

Conclusions:

• Distortionless diffusion-weighted imaging of the prostate is achievable in patients with THRs using conventional 3T MRI.
• The technique allows for prostate cancer screening with a b-value of 800 s/mm², 1.7x1.7x4 mm³ resolution, in a 6-minute scan time.