Multilevel Lumbar CT Attenuation Beyond L1: Comparison with QCT-Derived Volumetric Bone Mineral Density and Prevalent Fragility Fracture Status in a Diagnostic Referral Cohort
Aug 2026· Diagnostics· Vol 16, pp. 2640· 0 citations· 49 references
Medicine
TL;DR
Multilevel lumbar, reference-adjusted HU assessment beyond isolated L1 improves the identification of QCT-defined osteoporosis and the discrimination of prevalent fragility fracture status and provides a practical marker of trabecular bone quality beyond isolated L1.
Abstract
Background/Objectives: CT-based trabecular attenuation in Hounsfield units (HU) is used as a surrogate marker of bone quality, but most approaches rely on a single vertebral level, usually L1, where local abnormalities may limit reliability and availability. This study evaluated whether multilevel lumbar, reference-adjusted HU assessment beyond isolated L1 improves the identification of QCT-defined osteoporosis and the discrimination of prevalent fragility fracture status. Methods: Between 2021 and March 2024, 800 patients referred for evaluation of bone mineral density underwent QCT of the lumbar spine with a calibration phantom. Cancellous attenuation was measured in HU at L1–L3 using manually positioned ellipsoid regions of interest, with predefined adjacent levels (T12, L4) substituted when a target vertebra was unsuitable. Single-level HU, the mean multilevel HU value and the lowest valid HU value were compared with QCT-defined osteoporosis and prevalent fragility fracture status (vertebral or sacral) using ROC analyses and pairwise DeLong testing. Results: Mean multilevel HU correlated closely with mean vBMD (Spearman ρ = 0.988; p < 0.001); as both derive from the same acquisition, the same vertebral bodies and the same phantom, this reflects a strong association between two related measurements rather than validation against an independent standard. Osteoporosis was present in 483 patients (60.4%). Mean multilevel HU was associated with osteoporosis with an AUC of 0.996 (95% CI, 0.993–0.998) at an internally derived cut-off of ≤99.6 HU. In the 699 patients with a valid L1 measurement, in whom a paired comparison was possible, mean multilevel HU exceeded isolated L1-HU (0.992; p = 0.0028). For fracture status, the AUC was 0.975 (0.966–0.983) at ≤80.5 HU, without advantage over L1-HU (p = 0.816). A valid value was obtainable in all 800 patients versus 699 (87.4%) with L1 alone. All patients with a fracture had a vBMD below the osteoporosis threshold, so this endpoint is structurally dependent on the densitometric one. Conclusions: Multilevel lumbar HU assessment provides a practical marker of trabecular bone quality beyond isolated L1. Its principal advantage is measurement availability rather than a clinically meaningful gain in discrimination. The reported thresholds are internally derived, cohort- and protocol-specific, and require external validation.
OBJECTIVE
This study compared Hounsfield unit (HU) measurements obtained from different regions of interest (ROIs) on lumbar CT for assessing bone mineral density (BMD) and discriminating osteoporosis and thoracolumbar fragility fracture status, aiming to evaluate whether ROI selection meaningfully influences HU-based assessment.
METHODS
Five HU measurement methods were evaluated using lumbar CT. Their correlations with dual-energy X-ray absorptiometry (DEXA)-derived BMD and their discriminative performance for osteoporosis and thoracolumbar fragility fracture status were analyzed. Receiver operating characteristic (ROC) curves were constructed, and pairwise comparisons of areas under the curve (AUCs) were performed using the DeLong test. A sensitivity analysis was additionally conducted after excluding substituted vertebral levels and recalculating mean lumbar HU using only non-substituted vertebrae.
RESULTS
All five HU measurement methods showed significant correlations with DEXA-derived BMD, and no statistically significant differences in discriminative performance were observed among the five ROI methods in the primary analysis. In the sensitivity analysis excluding substituted vertebral levels, the AUCs remained comparable across methods for osteoporosis (0.816-0.826) and thoracolumbar fragility fracture status (0.677-0.689), with all pairwise DeLong tests showing no statistically significant differences (all p > 0.05).
CONCLUSION
Different lumbar CT ROI methods demonstrated comparable performance in assessing BMD and discriminating thoracolumbar fragility fracture status, and sensitivity analysis confirmed that exclusion of substituted vertebral levels did not materially affect the results. No ROI method showed statistically significant superiority, suggesting that ROI selection may be guided by clinical feasibility and workflow convenience rather than by diagnostic performance alone.
ADVANCES IN KNOWLEDGE
This study compares five commonly used lumbar CT HU measurement methods and shows that their performance is broadly similar. The findings suggest that ROI selection may be guided primarily by clinical feasibility and workflow convenience, although further external validation is required before routine clinical application.
Both HU and VBQ offer useful assessments of vertebral bone quality, but HU provides higher and more stable diagnostic accuracy, demonstrating higher sensitivity, specificity, and accuracy for detecting osteopenia and osteoporosis.
Omar Lubbad, Akram Hagos, Laila Lubbad et al.· European Radiology· 0 citations
Background/Objectives: This study aimed to evaluate whether artificial intelligence-derived vertebral volumetric bone mineral density (AI-vBMD) and paraspinal intermuscular adipose tissue (IMAT) ratio from routine computed tomography (CT) could identify moderate-to-severe vertebral compression fractures (VCFs) in breast cancer survivors, and whether paraspinal IMAT ratio and routinely available clinical variables improved diagnostic performance. Methods: This retrospective study included 275 women with breast cancer who underwent routine non-contrast CT and lumbar quantitative computed tomography (QCT). Hounsfield unit-derived volumetric bone mineral density (HU-vBMD) was derived using a QCT-referenced HU-to-vBMD conversion equation, whereas AI-vBMD and paraspinal IMAT ratio were extracted using automated software. Moderate-to-severe VCF was defined as Genant grade ≥ 2. Agreement with QCT-vBMD was assessed using correlation, intraclass correlation coefficient (ICC), and Bland–Altman analysis. Model discrimination was evaluated using receiver operating characteristic analysis and DeLong tests. Results: Moderate-to-severe VCF was present in 75 patients (27.3%). HU-vBMD and AI-vBMD showed excellent agreement with QCT-vBMD (ICC, 0.978 and 0.987, respectively). AI-vBMD outperformed HU-vBMD for identifying VCFs (AUC, 0.738 vs. 0.714; p < 0.001). IMAT ratio showed comparable standalone discrimination to AI-vBMD (AUC, 0.760 vs. 0.738; p = 0.604). Adding IMAT ratio to AI-vBMD improved discrimination (AUC, 0.786 vs. 0.738; p = 0.038). The full model incorporating clinical covariates achieved the highest AUC (0.828; 95% CI, 0.778–0.878). Conclusions: AI-vBMD and paraspinal IMAT ratio automatically extracted from routine CT improved the diagnostic assessment of prevalent moderate-to-severe VCFs in breast cancer survivors. This study supports an automated CT-based approach that integrates vertebral bone density and paraspinal muscle–fat information for opportunistic identification of clinically relevant VCFs.
Chen Wan, Lingquan Kong, Jie Hao et al.· Journal of Clinical Medicine· 0 citations
The nomogram developed based on conventional clinical data in this study, has undergone internal validation and demonstrated efficacy in predicting NVCF following PVP, and serves as a valuable decision-making tool for clinicians.
Yiqi Wu, Qing Song, Canwei Hu et al.· Frontiers in Medicine· 0 citations
VBQ can serve as an opportunistic exploratory screening marker of low BMD and FBQcsf may complement VBQ by identifying early marrow-related changes, although further validation is required.
Margrit Elis Müller, João Paulo Colhado Ferreira, Laura Mulazzani Minuzzi Macedo et al.· Skeletal Radiology· 0 citations
RATIONALE AND OBJECTIVES
Low-dose computed tomography (LDCT) is standard for lung cancer screening, yet validated fracture risk thresholds for 100-kVp protocols have not been established in health check-up cohorts. We evaluated whether L1 vertebral attenuation on 100-kVp LDCT predicts 10-year fragility fracture incidence.
MATERIALS AND METHODS
This retrospective cohort study included 1464 women age ≥50 years (median follow-up: 10.1 years). L1 Hounsfield Units (HU) were measured on 100-kVp LDCT by two independent readers. References value for normal and low bone mineral density (BMD) was derived from a separate calibration cohort (n = 246) with paired LDCT-Dual-energy X-ray absorptiometry (DXA) data (AUC 0.841). Endpoints included incident vertebral fractures and composite major fragility fractures.
RESULTS
HU = 160 (AUC = 0.841) stratified the whole group into normal BMD (>160 HU; n = 952) and low BMD (≤160 HU; n = 512). At 10 years, cumulative vertebral fracture incidence was 38.2 vs. 2.8% in low vs. normal BMD groups; composite fractures reached 48.1% vs. 6.3%. The incidence rate ratio was 3.46 (95% CI: 2.62-4.57) for vertebral fractures and 2.72 (95% CI: 2.14-3.46) for all fragility fractures. On multivariable Cox regression adjusting for age, body mass index, and comorbidities, low BMD (≤160 HU) remained an independent predictor of vertebral fracture (adjusted HR: 2.54; 95% CI: 1.33-4.85; p = 0.005).
CONCLUSION
L1 attenuation ≤160 HU on 100-kVp LDCT identified postmenopausal women at three-fold higher fragility fracture risk, with performance comparable to Fracture Risk Assessment Tool without BMD. In this healthy screenee cohort, L1 HU serves as the primary bone health signal, enabling early identification of at-risk individuals within existing LDCT workflows at no additional cost.