Imaging Evaluation of Fat Infiltration in Paraspinal Muscles on MRI: A Systematic Review with a Focus on Methodology

Abstract

Purpose: Numerous studies have applied a variety of methods to assess paraspinal muscle degeneration. However, the methodological differences in imaging evaluation may lead to imprecise or inconsistent results. This article aimed to provide a pragmatic summary review of the current imaging modalities, measurement protocols, and imaging parameters in the evaluation of paraspinal muscle fat infiltration (FI) in MRI studies.Methods: Web of Science, EMBASE, and PubMed were searched from January 2005 to March 2020 to identify studies that examined the FI of paraspinal muscles on MRI among patients with lumbar degenerative diseases.Results: Intramyocellular lipids measured by magnetic resonance spectroscopy and FI measured by chemical-shift MRI were both correlated to low back pain and several degenerative lumbar diseases, whereas results on the relationship between FI and degenerative lumbar pathologies using conventional MRI were conflicting. Multi-segment measurement of FI at the lesion segment and adjacent segments could be a prognostic indicator for lumbar surgery. Most studies adopted the center of the intervertebral disc or endplate as the level of slice to evaluate the FI. Compared with visual semiquantitative assessment, quantitative parameters appeared to be precise for eliminating individual or modality differences. It has been demonstrated that fat CSA/total CSA (based on area) and muscle-fat index (based on signal intensity) as quantitative FI parameters are associated with multiple lumbar diseases and clinical outcomes after surgery. Conclusion:Having a good command of the methodology of paraspinal muscle FI on MRI was effective for diagnosis and prognosis in clinical practice.

Association of Paraspinal Muscle CSA and PDFF Measurements With Lumbar Intervertebral Disk Degeneration in Patients With Chronic Low Back Pain

“…Yanik et al quantified the fat content of multifidus muscle in patients with CLBP and asymptomatic subjects by conventional MRI, and the results were consistent with this study (33,44,45). On the basis of the previous research, we manually delineated the edge of the muscle as the ROI, and further applied the multi-echo Dixon method, which corrected the main magnetic field inhomogeneity effect, T2* effect, T1 effect and other confounding factors, in order to make the quantification of paraspinal muscle fat content is more accurate, better repeatability and reliability (46)(47)(48). In order to minimize the possible impact of the slightly differences in spatial resolutions of T2 and PDFF images, we selected the layers at the center of the L4/5 and L5/S1 intervertebral discs as much as possible to delineate the ROI of the paraspinal muscles.…”

T2 mapping and fat quantification of lumbar paraspinal muscle in ankylosing spondylitis: a case control study

“…Studies revealed that the evaluation of fatty infiltration in lower lumbar segments can be best represented that of the entire lumbar region and could reflect the morbid state of patients with low back pain [ 34 , 38 ]. In addition, an inaccuracy of measurement and classification can occur at the L5/S1 level due to lumbosacral angulation [ 33 ].…”

“…The MRI protocol for lumbar vertebral muscles included localizers, sagittal T1-weighted image, sagittal short-T1 inversion recovery, axial T2 mapping with and without frequency-selective fat saturation (fatsat), and T2 IDEAL sequences. According to information obtained from previous studies, the amount of intramuscular fat significantly increases in the lower lumbar segments for the multifidus (MF) and erector spinae (ES) muscles compared with the upper lumbar segments, and measurement and classification at the L5/S1 level might be inaccurate due to lumbosacral angulation [ 33 , 34 ]; therefore, only the superior aspect levels of the L3/L4 and L4/L5 intervertebral disks were included in this study. For the axial T2 IDEAL sequence, the following pulse sequences were used: TE, 68 ms; TR, 4850 ms; echo train length, 12; slice thickness, 5 mm; no gap; FOV, 400 × 400 mm; matrix, 256 × 192; NEX, 1; bandwidth, 31.25 kHz; total slices, 10; and acquisition time, 4 min 7 s. Axial T2 mapping sequence with and without fat saturation was acquired (TR, 1000 ms; FOV, 400 × 400 mm; NEX, 1; slice thickness, 5 mm; no gap; matrix, 256 × 192; bandwidth, 31.25 kHz; total slices, 10; and acquisition time, 6 min 28 s) based on multiple echoes (9.7, 19.5, 29.2, 38.9, 48.7, 58.4, 68.2, 77.9 ms).…”

Predictors for the restoration of the sagittal spinal malalignment in patients with lumbar stenosis after short-segment decompression and fusion surgery

“…The fCSA of muscle was measured by the thresholding technique. rCSA was calculated by fCSA ratio to correspond level of lumbar CSA to eliminated personal difference [ 18 ].…”