Improved prediction of incident vertebral fractures using opportunistic QCT compared to DXA

Abstract

Objectives To compare opportunistic quantitative CT (QCT) with dual energy X-ray absorptiometry (DXA) in their ability to predict incident vertebral fractures. Methods We included 84 patients aged 50 years and older, who had routine CT including the lumbar spine and DXA within a 12-month period (baseline) as well as follow-up imaging after at least 12 months or who sustained an incident vertebral fracture documented earlier. Patients with bone disorders aside from osteoporosis were excluded. Fracture status and trabecular bone mineral density (BMD) were retrospectively evaluated in baseline CT and fracture status was reassessed at follow-up. BMD QCT was assessed by opportunistic QCT with asynchronous calibration of multiple MDCT scanners. Results Sixteen patients had incident vertebral fractures showing lower mean BMD QCT than patients without fracture ( p = 0.001). For the risk of incident vertebral fractures, the hazard ratio increased per SD in BMD QCT (4.07; 95% CI, 1.98–8.38), as well as after adjusting for age, sex, and prevalent fractures (2.54; 95% CI, 1.09–5.90). For DXA, a statistically significant increase in relative hazard per SD decrease in T -score was only observed after age and sex adjustment (1.57; 95% CI, 1.04–2.38). The predictability of incident vertebral fractures was good by BMD QCT (AUC = 0.76; 95% CI, 0.64–0.89) and non-significant by T -scores. Asynchronously calibrated CT scanners showed good long-term stability (linear drift ranging from − 0.55 to − 2.29 HU per year). Conclusions Opportunistic screening of mainly neurosurgical and oncologic patients in CT performed for indications other than densitometry allows for better risk assessment of imminent vertebral fractures than dedicated DXA. Key Points • Opportunistic QCT predicts osteoporotic vertebral fractures better than DXA reference standard in mainly neurosurgical and oncologic patients. • More than every second patient (56%) with an incident vertebral fracture was misdiagnosed not having osteoporosis according to DXA. • Standard ACR QCT-cutoff values for osteoporosis (< 80 mg/cm 3 ) and osteopenia (≤ 120 mg/cm 3 ) can also be applied scanner independently in calibrated opportunistic QCT.

Association of bone mineral density with reoperation rate following instrumented lumbar spinal fusion: a retrospective cohort and case-control study

“…Of note, BMD measurements are not performed on a regular basis prior to surgery in our hospital. We performed opportunistic screening of lumbar BMD in clinical CT scans (31), which has been validated and applied in various studies (22,(28)(29)(30)(32)(33)(34)47), showing low short-and long-term reproducibility errors (30). Previous studies demonstrated that lumbar BMD can be assessed in sagittal reformations of contrast-enhanced MDCT and used to differentiate patients with and without osteoporotic fractures (30), and it could also be used to predict these fractures (29).…”

“…Linear correction equations can be adjusted for systematic bias of apparent bone density related to different calibration techniques and contrast application (48). We analyzed CT scans obtained on different MDCT devices for indications other than densitometry and applied asynchronous calibration to calculate BMD (22,34). In contrast to direct HU measurements, which are dependent on the specific MDCT device used, calibration enables inter-scanner and/or inter-study comparability of BMD values.…”

“…Supplementary DXA examinations may become obsolete if volumetric BMD can be opportunistically assessed in preoperative CT imaging. The feasibility and validity of opportunistic BMD screening in existing CT data has been extensively shown (22,(28)(29)(30)(31)(32)(33)(34).…”

Opportunistic QCT Bone Mineral Density Measurements Predicting Osteoporotic Fractures: A Use Case in a Prospective Clinical Cohort

“…Fractured or otherwise altered vertebrae (e.g., vertebrae with severe degenerative changes, vertebrae after vertebro-/kyphoplasty) were not used for HU measurements. The HU values were then converted into BMD using HU-to-BMD conversion as previously described: (i) 0.928 × HU + 4.5 mg/cm 3 for the IQon Spectral CT, (ii) 0.855 × HU + 1.172 mg/cm 3 for the Philips iCT 256, (iii) 0.778 × HU − 4.693 mg/cm 3 for the Philips Brilliance 64, (iv) 1.011 × HU − 3.385 mg/cm 3 for the Siemens Somatom Definition AS+, and (v) 0.985 × HU + 15.516 mg/cm 3 for the Siemens Somatom Definition (12,15). A BMD correction offset for contrast-enhanced CT scans with arterial (-8.6 mg/cm 3 ) and portal venous contrast phase (-15.8 mg/cm 3 ) was added (16).…”

“…The CT scans are either asynchronously calibrated (separate scans of calibration phantoms and patients) or tissue-calibrated (using tissue within the scan such as muscle and fat tissue that are known for little variance regarding density). Recently, osteoporotic trabecular BMD of lumbar vertebrae was assessed by opportunistic QCT and allowed for better risk assessment of imminent vertebral fractures than DXA in neurosurgical and oncologic patients (12).…”