Abstract
ObjectiveTo investigate the in vivo applicability of non-contrast-enhanced hydroxyapatite (HA)-specific bone mineral density (BMD) measurements based on dual-layer CT (DLCT).MethodsA spine phantom containing three artificial vertebral bodies with known HA densities was measured to obtain spectral data using DLCT and quantitative CT (QCT), simulating different patient positions and grades of obesity. BMD was calculated from virtual monoenergetic images at 50 and 200 keV. HA-specific BMD values of 174 vertebrae in 33 patients (66 ± 18 years; 33% women) were determined in non-contrast routine DLCT and compared with corresponding QCT-based BMD values.ResultsExamining the phantom, HA-specific BMD measurements were on a par with QCT measurements. In vivo measurements revealed strong correlations between DLCT and QCT (r = 0.987 [95% confidence interval, 0.963–1.000]; p < 0.001) and substantial agreement in a Bland–Altman plot.ConclusionDLCT-based HA-specific BMD measurements were comparable with QCT measurements in in vivo analyses. This suggests that opportunistic DLCT-based BMD measurements are an alternative to QCT, without requiring phantoms and specific protocols.Key Points• DLCT-based hydroxyapatite-specific BMD measurements show a substantial agreement with QCT-based BMD measurements in vivo.• DLCT-based hydroxyapatite-specific measurements are on a par with QCT in spine phantom measurements.• Opportunistic DLCT-based BMD measurements may be a feasible alternative for QCT, without requiring dedicated examination protocols or a phantom.
Highlights
Fragility fractures are the main symptom of osteoporosis and frequently occur in the thoracic and lumbar spine
Ex vivo dual-layer CT (DLCT)-based phantom measurements represent the angles between the linear regression line of the high-dose calibration scan for different bone mineral density (BMD) and the linear regression of the 18 scans in different setups for each BMD
Means of differences between BMD scan results and manufacturer-specified values averaged for all different scan settings tended to be lower for DLCT (3.9 mg/ml HA) compared with those of quantitative CT (QCT) (4.8 mg/ml HA) (Table 1), this difference was not statistically significant (p = 0.152)
Summary
Fragility fractures are the main symptom of osteoporosis and frequently occur in the thoracic and lumbar spine. Dual-energy x-ray absorptiometry (DXA) and quantitative CT (QCT), the current clinical standards, are known to have limitations such as high susceptibility to confounders like body size or vascular calcifications and limited availability or relatively high radiation doses, respectively [5]. These methods are under-used with participation rates for DXA of only 30% and 4% in eligible women and men over 65 years, respectively [6]. Since osteoporosis is considered to be an underdiagnosed and undertreated condition [1], opportunistic screening would enhance the identification of individuals with low BMD being at risk for spinal fractures and would enable the prevention of major fragility fractures by an early initiation of therapy, e.g., with pharmacological treatment
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