Accelerated MRI of the Lumbar Spine Using Compressed Sensing: Quality and Efficiency

Abstract

Background: Decreasing MRI scan time is a key factor to increase patient comfort and compliance as well as the productivity of MRI scanners.

Purpose/hypothesis: Compressed sensing (CS) should significantly accelerate 3D scans. This study evaluated the clinical application and cost effectiveness of accelerated 3D T₂ sequences of the lumbar spine.

Study type: Prospective, cross-sectional, observational.

Population: Twenty healthy volunteers and 10 patients.

Field strength/sequence: A 3D T₂ TSE sequence, identical 3D sequences with three different parallel imaging and CS accelerating factors, and 2D TSE sequences as a clinical reference were obtained on a 3T scanner.

Assessment: Three readers evaluated the sequences for delineation of anatomical structures and image quality. A quantitative analysis consisting of root mean square error, structural similarity index, signal-to-noise ratio, and contrast-to-noise ratio were performed. The scan times were used to calculate cost differences for each sequence.

Statistical tests: An analysis of variance with repeated measurements and the Friedman test were used to test for potential differences between the sequences. Post-hoc analysis was made with the chi-squared and Tukey-Kramer test.

Results: CS with factor 4.5 results in unchanged image quality compared to the T₂ TSE for volunteers and patients (overall image impression: 4.75 vs. 4.20 [P = 0.73] and 4.90 vs. 4.47 [P = 0.44]). The CS 4.5 scan is 167 seconds (-39%) faster than the 3D and 216.5 seconds (-45%) faster than the 2D sequences. No significant differences was found for the diagnostic certainty in the volunteers and patients between 2D TSE and 3D CS 4.5 (P = 0.89 and P = 0.43). A reduction of scan time to 148 seconds (CS 8) was still rated acceptable for most diagnosis.

Data conclusion: CS accelerates the 3D T₂ without compromising image quality. The 3D sequences offer comparable diagnostic quality to the clinical 2D standard with less scan time (-45%), potentially increasing the productivity of MRI scanners.

Level of evidence: 1 Technical Efficacy: Stage 6 J. Magn. Reson. Imaging 2019;49:e164-e175.

Keywords: accelerated MRI scans; clinical standard; cost-benefit analysis; lumbar spine; magnetic resonance imaging; three-dimensional imaging.