The association between bone density evaluated on CT or MRI versus the gold standard dual-energy X-ray absorptiometry (DEXA) in the lumbar spine and hip: a meta-analysis.

INTRODUCTION: CT-based Hounsfield units (HU) and MRI-based vertebral bone quality (VBQ)-scores are opportunistic markers of bone mineral density and potential alternatives for dual-energy X-ray absorptiometry (DEXA). RESEARCH QUESTION: What is the correlation between HU values and VBQ-scores in relation to DEXA, and what is the corresponding area-under-the-curve (AUC)-based diagnostic discrimination to detect osteopenia and osteoporosis? MATERIAL AND METHODS: PubMed, Embase, Web of Science, Cochrane Library, and CINAHL were searched through August 2025 for studies reporting correlations between DEXA and CT and/or MRI or the AUC-based diagnostic discrimination of CT and/or MRI to detect osteopenia and osteoporosis. Random effects models were used to calculate pooled correlation coefficients and AUC values along with 95% confidence intervals. RESULTS: Forty-three studies, including 8222 patients, were analyzed. HU demonstrated stronger correlations with DEXA T-scores than the VBQ-score (maximum correlation coefficient: 0.741 (95% CI: 0.578-0.847) vs. -0.476 (95% CI: -0.548 to -0.398) and greater AUC-based diagnostic discrimination for osteopenia and osteoporosis (maximum AUC: 0.875 (95% CI: 0.841-0.909) vs. 0.806 (95% CI: 0.684-0.929) across all vertebrae and DEXA sites. Correlation and AUC-based diagnostic discrimination of HU were consistent across vertebrae, with slightly better results at L2 and the mean of L1-L4. VBQ-score correlations were highest at L1 and gradually decreased from L1 to L4. DISCUSSION AND CONCLUSION: When CT is available, HU appears to be the better-supported opportunistic marker for low BMD than VBQ. All vertebrae demonstrated comparable correlation and AUC-based diagnostic discrimination, with L2 HU and the mean of L1-L4 HU showing slightly superior results.