Intervertebral disc degeneration associated with vertebral marrow fat, assessed using quantitative magnetic resonance imaging

Correlation of R2* with fat fraction and bone mineral density and its role in quantitative assessment of osteoporosis

OBJECTIVES

To investigate the correlation of R2* with vertebral fat fraction (FF) and bone mineral density (BMD), and to explore its role in the quantitative assessment of osteoporosis (OP).

METHODS

A total of 83 patients with low back pain (59.77 ± 7.46 years, 30 males) were enrolled, which underwent lumbar MRI in IDEAL-IQ sequences and quantitative computed tomography (QCT) scanning within 48h. The FF, R2*, and BMD of all 415 lumbar vertebrae were respectively measured. According to BMD, all vertebrae were divided into BMD normal, osteopenia, and OP groups, and the difference of FF and R2* among groups was analyzed by one-way ANOVA. The correlation between R2*, FF, and BMD was analyzed by Pearson's test. Taking BMD as the gold standard, the efficacies for FF and R2* in diagnosis of OP and osteopenia were assessed by receiver operating characteristic curve, and their area under the curve (AUC) was compared with DeLong's test.

RESULTS

The FF and R2* were statistically different among groups (F values of 102.521 and 11.323, both p < 0.05), and R2* were significantly correlated with FF and BMD, respectively (r values of -0.219 and 0.290, both p < 0.05). In diagnosis of OP and osteopenia, the AUCs were 0.776 and 0.778 for FF and 0.638 and 0.560 for R2*, and the AUCs of R2* were lower than those of FF, with Z values of 4.030 and 4.087, both p < 0.001.

CONCLUSION

R2* is significantly correlated with FF and BMD and can be used as a complement to FF and BMD for quantitative assessment of OP.

KEY POINTS

• R2* based on IDEAL-IQ sequences has a definite but weak linear relationship with FF and BMD. • FF is significantly correlated with BMD and can effectively evaluate BMAT. • R2* can be used as a complement to FF and BMD for fine quantification of bone mineral loss and bone marrow fat conversion.

Associations between vertebral bone marrow fat and sagittal spine alignment as assessed by chemical shift-encoding-based water-fat MRI

BACKGROUND

The relationship between sagittal spine alignment and vertebral bone marrow fat is unknown. We aimed to assess the relationship between vertebral bone marrow fat and sagittal spine alignment using chemical shift-encoding-based water-fat magnetic resonance imaging (MRI).

METHODS

A total of 181 asymptomatic volunteers were recruited for whole spine X-ray and lumbar MRI. Spine typing was performed according to the Roussouly classification and measurement of vertebral fat fraction based on the chemical shift-encoding-based water-fat MRI. One-way analysis of variance (ANOVA) was used to analyze the differences in vertebral fat fraction between spine types. The post hoc least significant difference (LSD) test was utilized for subgroup comparison after ANOVA.

RESULTS

Overall, the vertebral fat fraction increased from L1 to L5 and was the same for each spine type. The vertebral fat fraction was the highest in type 1 and lowest in type 4 at all levels. ANOVA revealed statistically significant differences in fat fraction among different spine types at L4 and L5 (P < .05). The post hoc LSD test showed that the fat fraction of L4 was significantly different (P < .05) between type 1 and type 4 as well as between type 2 and type 4. The fat fraction of L5 was significantly different between type 1 and type 3, between type 1 and type 4, and between type 2 and type 4 (P < .05).

CONCLUSION

Our study found that vertebral bone marrow fat is associated with sagittal spine alignment, which may serve as a new additional explanation for the association of sagittal alignment with spinal degeneration.

Accuracy and applicability of dual-energy computed tomography in quantifying vertebral bone marrow adipose tissue compared with magnetic resonance imaging

Objectives

To evaluate the accuracy of dual-energy computed tomography (DECT) in quantifying bone marrow adipose tissue (BMAT) and its applicability in the study of osteoporosis (OP).

Methods

A total of 83 patients with low back pain (59.77 ± 7.46 years, 30 males) were enrolled. All patients underwent lumbar DECT and magnetic resonance imaging (MRI) scanning within 48 h, and the vertebral fat fraction (FF) was quantitatively measured, recorded as DECT-FF and MRI-FF. A standard quantitative computed tomography (QCT) phantom was positioned under the waist during DECT procedure to realize the quantization of bone mineral density (BMD). The intraclass correlation coefficient (ICC) and Bland–Altman method was used to evaluate the agreement between DECT-FF and MRI-FF. The Pearson test was used to study the correlation between DECT-FF, MRI-FF, and BMD. With BMD as a gold standard, the diagnostic efficacy of DECT-FF and MRI-FF in different OP degrees was compared by receiver operating characteristic (ROC) curve and DeLong test.

Results

The values of DECT-FF and MRI-FF agreed well (ICC = 0.918). DECT-FF and MRI-FF correlated with BMD, with r values of −0.660 and −0.669, respectively (p < 0.05). In the diagnosis of OP and osteopenia, the areas under curve (AUC) of DECT-FF was, respectively, 0.791 and 0.710, and that of MRI-FF was 0.807 and 0.708, and there was no significant difference between AUCs of two FF values (with Z values of 0.503 and 0.066, all p > 0.05).

Conclusion

DECT can accurately quantify the BMAT of vertebrae and has the same applicability as MRI in the study of OP.

Degenerative Lumbar Spine Disease: Imaging and Biomechanics

Chronic low back pain (CLBP) is one of the most common diagnoses encountered when considering years lived with disability. The degenerative changes of the lumbar spine include a wide spectrum of morphological modifications visible on imaging, some of them often asymptomatic or not consistent with symptoms. Phenotyping by considering both clinical and imaging biomarkers can improve the management of CLBP. Depending on the clinical presentation, imaging helps determine the most likely anatomical nociceptive source, thereby enhancing the therapeutic approach by targeting a specific lesion. Three pathologic conditions with an approach based on our experience can be described: (1) pure painful syndromes related to single nociceptive sources (e.g., disk pain, active disk pain, and facet joint osteoarthritis pain), (2) multifactorial painful syndromes, representing a combination of several nociceptive sources (such as lumbar spinal stenosis pain, foraminal stenosis pain, and instability pain), and (3) nonspecific CLBP, often explained by postural (muscular) syndromes.

Repeatability and Image Quality of IDEAL-IQ in Human Lumbar Vertebrae for Fat and Iron Quantification across Acquisition Parameters

Echo asymmetry and least square estimation-IQ (IDEAL-IQ) were used to quantify fat and iron to verify the effects of collection parameters on repeatability and image quality of water and fat in human vertebral body. Six IDEAL-IQ sequences were used to scan 48 healthy adult women. Reproducibility of fat and iron quantification and image quality were assessed for six IDEAL-IQ sequences. The results showed that the correlation index (0.987, 0.721) of FF and R2∗ between scans of sequence 2 was higher than that of other sequences, and the consistency of fat quantification was better than that of iron (0.860 vs. 0.579) (P < 0.001). Sequence 2 had the highest image quality score (4.9) and the lowest CV score (9.2%). In the FF figure, SNR (18.8) and CNR (17.8 ± 6.4) were the highest, while CV was the lowest (36.7%, 36.1%). In the R2∗ figure, sequence 3 had the highest SNR (21.8) and CNR (20.5), but its CV (51.8% and 56.1%) was significantly higher than that of sequence 2. The occurrence of fat-water exchange (FWS) was lowest in sequence 2 and sequence 4 (0, N = 96). In conclusion, the fat quantification of IDEAL-IQ was robust to the changes of collection parameters, and section thickness (ST) had a certain effect on maintaining good repeatability of R2∗ quantification. The higher the ST was, the better the image quality of FF and R2∗ was maintained and stable and the less the occurrence of FWS.

Advances in research on fat infiltration and lumbar intervertebral disc degeneration

Low back pain (LBP) is a disabling condition with no available cure, severely affecting patients' quality of life. Intervertebral disc degeneration (IVDD) is the leading cause of chronic low back pain (CLBP). IVDD is a common and recurrent condition in spine surgery. Disc degeneration is closely associated with intervertebral disc inflammation. The intervertebral disc is an avascular tissue in the human body. Transitioning from hematopoietic bone marrow to bone marrow fat may initiate an inflammatory response as we age, resulting in bone marrow lesions in vertebrae. In addition, the development of LBP is closely associated with spinal stability imbalance. An excellent functional state of paraspinal muscles (PSMs) plays a vital role in maintaining spinal stability. Studies have shown that the diminished function of PSMs is mainly associated with increased fat content, but whether the fat content of PSMs is related to the degree of disc degeneration is still under study. Given the vital role of PSMs lesions in CLBP, it is crucial to elucidate the interaction between PSMs changes and CLBP. Therefore, this article reviews the advances in the relationship and the underlying mechanisms between IVDD and PSMs fatty infiltration in patients with CLBP.

[Value of a nomogram model based on IDEAL-IQ for predicting early bone mass loss]

OBJECTIVE

To assess the diagnostic efficiency of a nomogram model based on iterative decomposition of water and fat with echo asymmetry and least-squares estimation- iron quantification (IDEAL- IQ) for predicting early bone loss of the lumbar vertebrae.

METHODS

Fifty-nine volunteers and patients with osteoporosis underwent examinations with both dual-energy X-ray absorptiometry (DXA) to determine bone mineral density (BMD) of L1-4 vertebrae and lumbar magnetic resonance imaging (MRI) with IDEAL-IQ sequence for measurement of bone marrow FF of L1-4 vertebrae. According to the results of DXA, the subjects were divided into normal bone mass group (n=23) and osteopenia group (n=36). The FF values of the two groups were compared and the diagnostic efficacy of the FF value was evaluated using ROC curve analysis. Multivariate logistic regression analysis was used to identify the independent factors for predicting bone mass loss, and a visual nomogram model was constructed and its diagnostic efficiency was assessed.

RESULTS

The FF value of the vertebrae was significant lower in normal bone mass group than in osteopenia group [(38.84±6.75)% vs (51.96±7.65)%, P < 0.05). ROC curve analysis showed that the AUC of the FF value for differentiating normal bone mass and osteopenia was 0.797 with a cutoff value of 46.85%, a sensitivity of 73.91% and a specificity of 80.56%. Multivariate logistics regression analysis identified the FF value, age and BMI as the independent factors for predicting bone mass loss. The diagnostic AUC of the nomogram model was 0.954 (95% CI: 0.806-0.957), and the predicted probability of the model was in good agreement with the actual probability. Decision curve analysis showed that the nomogram model could provide more net benefit than the FF vale alone.

CONCLUSION

FF value of MRI IDEAL- IQ sequence can reflect bone marrow fat content of the vertebral body, and the nomogram model incorporating the FF value, age, and BMI can further improve the predictive efficiency to provide a visual modality for predicting early bone mass loss.

MicroRNA‑200c‑3p suppresses intervertebral disc degeneration by targeting RAP2C/ERK signaling

Intervertebral disc degeneration (IDD) is a major cause of lower back pain. The high morbidity associated with this disease diminishes the quality of life of those who are affected. MicroRNAs (miRs) play crucial roles in various diseases, including IDD. However, the mechanism via which miR‑200c‑3p plays a role in the development of IDD remains unknown. The present study aimed to investigate the effect of miR‑200c‑3p on the progression of IDD and the underlying mechanism. The expression level of miR‑200c‑3p was evaluated in intervertebral disc tissues from patients with IDD. To construct the IDD cell model, the nucleus pulposus (NP) cells were treated with lipopolysaccharide (LPS) 24 h following transfection with miR‑200c‑3p mimic or inhibitor. A luciferase activity assay was performed, while reverse transcription‑quantitative PCR and western blotting were conducted to determine the RNA and protein expression levels, respectively. The expression level of miR‑200c‑3p in the intervertebral disc tissues of patients with IDD was lower than that of normal subjects. LPS treatment reduced the expression level of miR‑200c‑3p in NP cells. Moreover, miR‑200c‑3p mimic inhibited LPS‑induced NP cell apoptosis. It was found that miR‑200c‑3p attenuated inflammatory cytokine levels and extracellular matrix (ECM) degradation in NP cells. Furthermore, miR‑200c‑3p targeted Ras‑related protein 2C (RAP2C) in NP cells. RAP2C promoted apoptosis, inflammatory cytokine levels and ECM degradation by activating ERK signaling. Knockdown of RAP2C and inhibition of ERK signaling by SCH772984 partially reversed the proinflammatory effect of the miR‑200c‑3p inhibitor on LPS‑treated NP cells. Thus, miR‑200c‑3p inhibits NP cell apoptosis, inflammatory cytokine levels and ECM degradation in IDD by targeting RAP2C/ERK signaling.