Fat quantification in MRI-defined lumbar muscles

Some studies suggest fat infiltration in the lumbar muscles (LM) is associated with lower back pain (LBP) in adults. Usually fat in MRI-defined lumbar muscles is qualitatively valuated by visual grading via a 3 point scale, whereas a quantitative continuous (0 - 100%) approach may provide a greater insight. In this paper, we propose a method to precisely quantify the fat content / infiltration in a user-defined region of the lumbar muscles, which may aid better diagnosis. The key steps are segmenting the region of interest (ROI) from the lumbar muscles, identifying the fatty regions in the segmented region based on the selected threshold and softness levels, computing the parameters (such as total and region-wise fat content percentage, total-cross sectional area (TCSA), functional cross- sectional area (FCSA)) and exporting the computations and associated patient information from the MRI, into a atabase. A standalone application using MATLAB R2010a was developed to perform the required computations along with an intuitive GUI

Structural changes of lumbar muscles in non-specific low back pain

Background: Lumbar muscle dysfunction due to pain might be related to altered lumbar muscle structure. Macroscopically, muscle degeneration in low back pain (LBP) is characterized by a decrease in cross-sectional area and an increase in fat infiltration in the lumbar paraspinal muscles. In addition microscopic changes, such as changes in fiber distribution, might occur. Inconsistencies in results from different studies make it difficult to draw firm conclusions on which structural changes are present in the different types of non-specific LBP. Insights regarding structural muscle alterations in LBP are, however, important for prevention and treatment of non-specific LBP. Objective: The goal of this article is to review which macro- and/or microscopic structural alterations of the lumbar muscles occur in case of non-specific chronic low back pain (CLBP), recurrent low back pain (RLBP), and acute low back pain (ALBP). Study Design: Systematic review. Setting: All selected studies were case-control studies. Methods: A systematic literature search was conducted in the databases PubMed and Web of Science. Only full texts of original studies regarding structural alterations (atrophy, fat infiltration, and fiber type distribution) in lumbar muscles of patients with non-specific LBP compared to healthy controls were included. All included articles were scored on methodological quality. Results: Fifteen studies were found eligible after screening title, abstract, and full text for inclusion and exclusion criteria. In CLBP, moderate evidence of atrophy was found in the multifidus; whereas, results in the paraspinal and the erector spinae muscle remain inconclusive. Also moderate evidence occurred in RLBP and ALBP, where no atrophy was shown in any lumbar muscle. Conflicting results were seen in undefined LBP groups. Results concerning fat infiltration were inconsistent in CLBP. On the other hand, there is moderate evidence in RLBP that fat infiltration does not occur, although a larger muscle fat index was found in the erector spinae, multifidus, and paraspinal muscles, reflecting an increased relative amount of intramuscular lipids in RLBP. However, no studies were found investigating fat infiltration in ALBP. Restricted evidence indicates no abnormalities in fiber type in the paraspinal muscles in CLBP. No studies have examined fiber type in ALBP and RLBP. Limitations: Lack of clarity concerning patient definitions, exact LBP symptoms, and applied methods. Conclusions: The results indicate atrophy in CLBP in the multifidus and paraspinal muscles but not in the erector spinae. No atrophy was shown in RLBP and ALBP. Fat infiltration did not occur in RLBP, but results in CLBP were inconsistent. No abnormalities in fiber type in the paraspinal muscles were found in CLBP

An interactive segmentation tool for quantifying fat in lumbar muscles using axial lumbar-spine MRI

In this paper we present an interactive tool that can be used to quantify fat infiltration in lumbar muscles, which is useful in studying fat infiltration and lower back pain (LBP) in adults. Currently, a qualitative assessment by visual grading via a 5-point scale is used to study fat infiltration in lumbar muscles from an axial view of lumbar-spine MR Images. However, a quantitative approach (on a continuous scale of 0–100%) may provide a greater insight. In this paper, we propose a method to precisely quantify the fat deposition/infiltration in a user-defined region of the lumbar muscles, which may aid better diagnosis and analysis. The key steps are interactively segmenting the region of interest (ROI) from the lumbar muscles using the well known livewire technique, identifying fatty regions in the segmented region based on variable-selection of threshold and softness levels, automatically detecting the center of the spinal column and fragmenting the lumbar muscles into smaller regions with reference to the center of the spinal column, computing key parameters [such as total and region-wise fat content percentage, total-cross sectional area (TCSA) and functional cross-sectional area (FCSA)] and exporting the computations and associated patient information from the MRI, into a database. A standalone application using MATLAB R2014a was developed to perform the required computations along with an intuitive graphical user interface (GUI)

Manually defining regions of interest when quantifying paravertebral muscles fatty infiltration from axial magnetic resonance imaging : a proposed method for the lumbar spine with anatomical cross-reference

Background: There is increasing interest in paravertebral muscle composition as a potential prognostic and diagnostic element in lumbar spine health. As a consequence, it is becoming popular to use magnetic resonance imaging (MRI) to examine muscle volume and fatty infiltration in lumbar paravertebral muscles to assess both age-related change and their clinical relevance in low back pain (LBP). A variety of imaging methods exist for both measuring key variables (fat, muscle) and for defining regions of interest, making pooled comparisons between studies difficult and rendering post-production analysis of MRIs confusing. We therefore propose and define a method as an option for use as a standardized MRI procedure for measuring lumbar paravertebral muscle composition, and to stimulate discussion towards establishing consensus for the analysis of skeletal muscle composition amongst clinician researchers. Method: In this descriptive methodological study we explain our method by providing an examination of regional lumbar morphology, followed by a detailed description of the proposed technique. Identification of paravertebral muscles and vertebral anatomy includes axial E12 sheet-plastinates from cadaveric material, combined with a series of axial MRIs that encompass sequencing commonly used for investigations of muscle quality (fat-water DIXON, T1-, and T2-weighted) to illustrate regional morphology; these images are shown for L1 and L4 levels to highlight differences in regional morphology. The method for defining regions of interest (ROI) for multifidus (MF), and erector spinae (ES) is then described. Results: Our method for defining ROIs for lumbar paravertebral muscles on axial MRIs is outlined and discussed in relation to existing literature. The method provides a foundation for standardising the quantification of muscle quality that particularly centres on examining fatty infiltration and composition. We provide recommendations relating to imaging parameters that should additionally inform a priori decisions when planning studies examining lumbar muscle tissues with MRI. Conclusions: We intend this method to provide a platform towards developing and delivering meaningful comparisons between MRI data on lumbar paravertebral muscle quality

Reliability of quantifying the spatial distribution of fatty infiltration in lumbar paravertebral muscles using a new segmentation method for T1-weighted MRI

Background: To our knowledge, there are no methods allowing for quantification of the spatial distribution of lumbar paravertebral muscle fatty infiltration (FI) in the transverse plane. There is an increasing emphasis on muscle tissues as modifiable factors in lumbar spine health. Population datasets based on conventional T1-weighted (T1-W) magnetic resonance imaging (MRI) represent a valuable resource for examining all spinal tissues, and methods with reliability are needed. The aim of our study was to determine the reliability of a novel method quantifying lumbar paravertebral muscle fat content based on conventional T1-W MRI. Methods: Axial 3-Tesla T1W MRIs from ten adult subjects (3W, 7M; mean age 52.8 ± SD 7.2 years) were randomly selected from the large prospective cross-sectional Hong Kong Population-based Disc Degeneration Cohort study examining lumbar spine degeneration. The selected sample included subjects with mixed imaging-determined disc degeneration and low back pain history. Two raters with MRI lumbar paravertebral muscle analysis experience (R1 > 250 h and R2 > 1000 h) repeat-measured the image-set a week apart. Multifidus and erector spinae (spinalis, longissimus and iliocostalis) were manually outlined together on a single-slice from the inferior vertebral end-plates of L1 to L5 using a semi-automated, quartile-defining (Q1-4 (medial to lateral) and Qmean) MatLab-based programme. Bland-Altman plots and intra-class correlation coefficients (ICC) with 95 % confidence intervals (CI) describe intra- and inter-rater reliability according to lumbar level, quartile, and side, and combined level and quartile. Results: There was good intra- (ICC = 0.88; CI: 0.87-0.90) and inter-rater agreement (ICC = 0.82; CI: 0.80-0.84). Intra-rater values for Qmean (ICC; CI) were higher at L5 (0.89; 0.79-0.94) than L1 (0.61; 0.37-0.78). Higher intra-rater values for L1-5 were shown at Q1 (0.93; 0.91-0.95) than Q3 (0.83; 0.78-0.87) or Q4 (0.81; 0.76-0.85), and on the right (0.91; 0.90-0.93) than left (0.85; 0.83-0.88). Similar observations were made for inter-rater values in terms of lumbar level and quartile, with no differences between sides shown. Conclusions: In our study of ten cases we demonstrate a reliable method to quantify the spatial distribution of fat content in lumbar paravertebral muscles based on T1W MRI. Understanding the geography of fat content in these muscles may offer additional insight in determining and improving spinal health. The clinical relevance and application of this method require testing across various populations to build on the early feasibility established in this study

Validation of 3D spino-pelvic muscle reconstructions based on dedicated MRI sequences for fat-water quantification

 Objectives: To evaluate a protocol, including MRI acquisition with dedicated sequences for fat-water quantification and semi-automatic segmentation, for 3D geometry measurement and fat infiltration of key muscles of the spino-pelvic complex. Materials and Methods: MRI Protocol: Two axial acquisitions from the thoraco-lumbar region to the patella were obtained: one T1 weighted and one based on the Dixon method, permitted to evaluate the proportion of fat inside each muscle. Muscle Reconstruction: With Muscl’X software, 3D reconstructions of 18 muscles or groups of muscles were obtained identifying their contours on a limited number of axial images (DPSO Method); 3D references were obtained only on T1 acquisitions identifying the contour of the muscles on all axial images. Evaluation: For two volunteers, three operators completed reconstructions three times across three sessions. Each reconstruction was projected on the reference to calculate the ‘point to surface’ error. Mean and maximal axial section, muscle volume, and muscle length calculated from the reconstructions were compared to reference values, and intra- and inter-operator variability for those parameters were evaluated. Results: 2xRMS ‘point to surface’ error was below 3 mm, on average. The agreement between the two methods was variable between muscles [-4.50; 8.00 %] for the mean axial section, the length and the volume. Intra- and inter-operator variability were less than 5% and comparison of variability for the Fat and T1 reconstructions did not reveal any significant differences. Discussion: Excellent inter- and intra-operator reliability was demonstrated for 3D muscular reconstruction using the DPSO method and Dixon images that allowed generation of patient-specific musculoskeletal models. Fondation Paristech, ISS

Magnetic resonance imaging evaluation of age and level dependence of multifidus fatty infiltration in normal Indian healthy volunteers

Background: Multifidus is one of the main stabilizers of lumbar spine. Fatty infiltration of multifidus varies with the age, sex, side and level of spine studied. The present study aims at the evaluation and comparison of the trends of multifidus fatty infiltration in normal population at various levels in both genders, side and different decade groups in healthy individual volunteers.Methods: Twenty-five normal healthy volunteers equally distributed across different age groups (3rd-7th decades) formed the healthy study group. In step 1, normal population magnetic resonance (MR) images are collected and evaluated individually. In step 2, fatty infiltration of all people ascending in age was calculated at each lumbar level and on either side. In step 3, normal population were divided into decades and fatty infiltration at each decade and segment wise comparison was done. In step 4, statistical analysis of significance was done between the groups. All the T2 MR images were measured using Image j 1.50i software. Exclusion criteria included no proper visualization of paraspinal musculature in the T2 MR images. Associated conditions affecting the degeneration (other lytic lesions/vertebral fractures-healed or unhealed). Other etiology included disc prolapse, listhesis, infections, tumors, and trauma. For each MRI scan, at least 3 cuts for each segment were obtained in which the central cut will be selected for measurement.Results: In study population, at all age groups the multifidus fatty infiltration (MFI) at all given levels upper lumbar levels (L1-2, L2-3) showed less fatty infiltration than lower levels. With increasing age there is increase in MFI in all levels. On either side, as the age increases fat % increases and in individual people as the segment going caudal the fat % increases. At each segment left side has more fat % than right side and overall fat % increase from L1 to S1 levels. As decades increases fat % increases in each individual segment, and also fat % increases from cephalad to caudal. There is a rapid increase in fat % transition from 4th to 5th decade. Overall fat % increase is seen from L1 to S1 in each decade. Females L1-2 to L3-4 does not show significant fat % increase. There are more fat % in females than males in lower lumbar levels, but the body mass index (BMI), daily activities may be a confounding factor.Conclusions: Lumbar paravertebral muscle fat content increases with aging, in healthy volunteers 3nd to 7th decade of age. Women, low lumbar levels, left side the multifidus muscle are most affected

Quantification of intramuscular fat in patients with late-onset Pompe disease by conventional magnetic resonance imaging for the long-term follow-up of enzyme replacement therapy

OBJECTIVE: The objective of this study was to evaluate a quantitative method based on conventional T1-weighted magnetic resonance (MR) imaging to assess fatty muscular degeneration in patients with late-onset Pompe disease and to compare it with semi-quantitative visual evaluation (the Mercuri score). In addition, a long-term retrospective data analysis was performed to evaluate treatment response to enzyme replacement therapy with alglucosidase alfa. METHODS: MR images of the lumbar spine were acquired in 41 patients diagnosed with late-onset Pompe disease from 2006 through 2015. Two independent readers retrospectively evaluated fatty degeneration of the psoas and paraspinal muscles by applying the Mercuri score. Quantitative semi-automated muscle and fat tissue separation was performed, and inter-observer agreement and correlations with clinical parameters were assessed. Follow-up examinations were performed in 13 patients treated with alglucosidase alfa after a median of 39 months; in 7/13 patients, an additional follow-up examination was completed after a median of 63 months. RESULTS: Inter-observer agreement was high. Measurements derived from the quantitative method correlated well with Medical Research Council scores of muscle strength, with moderate correlations found for the 6-minute walk test, the 4-step stair climb test, and spirometry in the supine position. A significant increase in the MR-derived fat fraction of the psoas muscle was found between baseline and follow-up 1 (P = 0.016), as was a significant decrease in the performance on the 6-minute walk test (P = 0.006) and 4-step stair climb test (P = 0.034), as well as plasma creatine kinase (P = 0.016). No statistically significant difference in clinical or MR-derived parameters was found between follow-up 1 and follow-up 2. CONCLUSIONS: Quantification of fatty muscle degeneration using the semi-automated method can provide a more detailed overview of disease progression than semi-quantitative Mercuri scoring. MR-derived data correlated with clinical symptoms and patient exercise capacity. After an initial worsening, the fat fraction of the psoas muscle and performance on the 6-minute walk test stayed constant during long-term follow-up under enzyme replacement therapy