Abstract
ObjectivesOsteoporosis remains under-diagnosed, which may be improved by opportunistic bone mineral density (BMD) measurements on CT. However, correcting for the influence of intravenous iodine-based contrast agent is challenging. The purpose of this study was to assess the diagnostic accuracy of iodine-corrected vertebral BMD measurements derived from non-dedicated contrast-enhanced phantomless dual-layer spectral CT (DLCT) examinations.MethodsVertebral volumetric DLCT-BMD was measured in native, arterial, and portal-venous scans of 132 patients (63 ± 16 years; 32% women) using virtual monoenergetic images (50 and 200 keV). For comparison, conventional BMD was determined using an asynchronous QCT calibration. Additionally, iodine densities were measured in the abdominal aorta (AA), inferior vena cava, and vena portae (VP) on each CT phase to adjust for iodine-related measurement errors in multivariable linear regressions and a generalized estimated equation, and conversion equations were calculated.ResultsBMD values derived from contrast-enhanced phases using conversion equations adjusted for individual vessel iodine concentrations of VP and/or AA showed a high agreement with those from non-enhanced scans in Bland-Altman plots. Mean absolute errors (MAE) of DLCT-BMD were 3.57 mg/ml for the arterial (R2 = 0.989) and 3.69 mg/ml for the portal-venous phase (R2 = 0.987) (conventional BMD: 4.70 [R2 = 0.983] and 5.15 mg/ml [R2 = 0.981]). In the phase-independent analysis, MAE was 4.49 mg/ml for DLCT (R2 = 0.989) (conventional BMD: 4.82 mg/ml [R2 = 0.981]).ConclusionsConverted BMD derived from contrast-enhanced DLCT examinations and adjusted for individual vessel iodine concentrations showed a high agreement with non-enhanced DLCT-BMD, suggesting that opportunistic BMD measurements are feasible even in non-dedicated contrast-enhanced DLCT examinations.Key Points• Accurate BMD values can be converted from contrast-enhanced DLCT scans, independent from the used scan phase.• DLCT-BMD measurements from contrast-enhanced scans should be adjusted with iodine concentrations of portal vein and/or abdominal aorta, which significantly improves the goodness-of-fit of conversion models.
Highlights
Osteopenia and osteoporosis remain a severe challenge in health care, from a clinical perspective—the treatment gap is estimated at 59% of women and 57% of men in the EU [1]—and from an epidemiologic view considering its contribution to an increasing number of fall-related deaths [2]
A commercially available spectral CT software was used for the generation of iodine density maps based on iodine-water decomposition (IntelliSpace Portal 10.1.0, Philips Healthcare). Both dual-layer spectral CT (DLCT) and conventional bone mineral density (BMD) values from CE scans were separately correlated with their reference values from corresponding NE scans in multivariable linear regression models using forward selection
BMD values from CE scans, vessel iodine concentrations (AA, inferior vena cava (IVC), and vena portae (VP)), age, and sex represented the set of selectable independent variables
Summary
Osteopenia and osteoporosis remain a severe challenge in health care, from a clinical perspective—the treatment gap is estimated at 59% of women and 57% of men in the EU [1]—and from an epidemiologic view considering its contribution to an increasing number of fall-related deaths [2]. Men with prostate cancer receiving androgen deprivation therapy (ADT) bear an increased risk to suffer from accelerated bone loss, which is a major adverse effect [10,11,12]. Even though guidelines recommend evaluation with baseline and periodic follow-up BMD quantification [13], there is a severe under-use of dedicated imaging methods such as dual-energy x-ray absorptiometry (DXA) or quantitative CT (QCT)—e.g., for patients with non-metastatic prostate cancer, only about one in ten patients over 65 years receiving ADT undergoes a baseline bone densitometry [14,15,16]
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