Sparse-SEMAC: rapid and improved SEMAC metal implant imaging using SPARSE-SENSE acceleration.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Device Technology
• Radiology

Background:

• Metal implants cause significant artifacts in MRI scans, limiting diagnostic capabilities.
• Standard SEMAC (Simultaneous multi-slice Echo-Planar Imaging with Controlled aliasing) techniques offer some artifact reduction but are limited by scan time.
• Accelerated MRI techniques are crucial for improving patient throughput and diagnostic accuracy.

Purpose of the Study:

• To develop and evaluate an accelerated SEMAC (Sparse-SEMAC) technique for metal implant MRI.
• To reduce scan time and improve the correction of metal artifacts in patients with hip implants.
• To assess the feasibility of Sparse-SEMAC for clinical use.

Main Methods:

• Developed a Sparse-SEMAC pulse sequence utilizing pseudorandom k_y-k_z undersampling and multicoil encoding for eight-fold acceleration.
• Integrated an inline image reconstruction for efficient processing.
• Compared Sparse-SEMAC with standard SEMAC in three patients with hip implants using high-resolution Proton Density (PD) and lower-resolution STIR sequences.
• Evaluated image quality through consensus reading by two expert musculoskeletal radiologists.

Main Results:

• Sparse-SEMAC achieved an eight-fold acceleration, resulting in a two-fold reduction in scan time compared to standard SEMAC.
• The technique demonstrated improved correction of metal artifacts for hip implants.
• Spatial resolution was maintained without degradation.
• SEMAC-encoding steps (SES) were 15 for Sparse-SEMAC and 9 for Standard-SEMAC.

Conclusions:

• Sparse-SEMAC offers significant acceleration, enabling clinically feasible MRI examination times.
• The method provides enhanced correction of metal distortion artifacts.
• This technique holds promise for improving MRI utility in patients with metallic implants.