Comprehensive Assessment of Osteoporosis and Bone Fragility with CT Colonography

Abstract

).q RSNA, 2015 Purpose:To evaluate the ability of additional analysis of computed tomographic (CT) colonography images to provide a comprehensive osteoporosis assessment. Materials and Methods:This Health Insurance Portability and Accountability Actcompliant study was approved by our institutional review board with a waiver of informed consent. Diagnosis of osteoporosis and assessment of fracture risk were compared between biomechanical CT analysis and dual-energy x-ray absorptiometry (DXA) in 136 women (age range, 43-92 years), each of whom underwent CT colonography and DXA within a 6-month period (between January 2008 and April 2010). Blinded to the DXA data, biomechanical CT analysis was retrospectively applied to CT images by using phantomless calibration and finite element analysis to measure bone mineral density and bone strength at the hip and spine. Regression, Bland-Altman, and reclassification analyses and paired t tests were used to compare results. Results:For bone mineral density T scores at the femoral neck, biomechanical CT analysis was highly correlated (R 2 = 0.84) with DXA, did not differ from DXA (P = .15, paired t test), and was able to identify osteoporosis (as defined by DXA), with 100% sensitivity in eight of eight patients (95% confidence interval [CI]: 67.6%, 100%) and 98.4% specificity in 126 of 128 patients (95% CI: 94.5%, 99.6%). Considering both the hip and spine, the classification of patients at high risk for fracture by biomechanical CT analysis-those with osteoporosis or "fragile bone strength"-agreed well against classifications for clinical osteoporosis by DXA (T score 22.5 at the hip or spine), with 82.8% sensitivity in 24 of 29 patients (95% CI: 65.4%, 92.4%) and 85.7% specificity in 66 of 77 patients (95% CI: 76.2%, 91.8%). Conclusion:Retrospective biomechanical CT analysis of CT colonography for colorectal cancer screening provides a comprehensive osteoporosis assessment without requiring changes in imaging protocols.q RSNA, 2015

Phantomless calibration of CT scans for measurement of BMD and bone strength—Inter-operator reanalysis precision

“…The resulting type of areal BMD measurements has been validated against DXA measurements [2, 3, 24]. …”

“…For the hip, we measured DXA-equivalent areal BMD values for the femoral neck and total hip regions and overall femoral strength for a simulated sideways fall, preferentially from the left proximal femur (Figure 2). All these “clinical” measurements have been validated in various prospective [1, 25, 28] and prevalent [26, 27, 29, 30] fracture-outcome studies, and are available clinically for patient care [2, 3, 31] and meet recommended practice guidelines [32]. To enable further comparisons with the research literature, we also report on the reanalysis precision for various other volumetric BMD measurements, specifically, integral volumetric BMD for both the whole vertebral body and total hip and their respective cortical and trabecular compartments.…”

“…Quantitative analysis of computed tomography (CT) scans can be performed clinically to identify patients at high risk of fracture [1–3] based on calibrated measurements of bone mineral density (BMD) at the spine and hip, as well as measurements of bone strength when combined with finite element analysis [4–7]. In any quantitative CT analysis, proper calibration of the scan is required to correct for variations in scanner settings and attenuation characteristics [8], any related beam-hardening, and patient-specific characteristics such as body size, all of which can alter the attenuation characteristics [9].…”

“…Already validated clinically against DXA for accurately measuring areal BMD at the hip [2, 3], this technique utilizes as calibrating reference materials the external air that is visible on the patient’s CT scan and one of either the patient’s blood or adipose tissue adjacent to the bone being assessed. Applying this technique to a diverse cohort of patients and CT scanners, we sought to quantify its inter-operator reanalysis precision for measuring both BMD and finite element-derived bone strength, at both the spine and hip; we also sought to confirm the equivalence of the phantomless versus traditional phantom-based measurements.…”

Head-Neck Osteoplasty has Minor Effect on the Strength of an Ovine Cam-FAI Model: In Vitro and Finite Element Analyses

“…Ideally, the resulting femoral strength after osteochondroplasty could be predicted preoperatively using computer simulations based on finite element (FE) methods. These computer models are generated from quantitative CT (QCT) after conversion of the Hounsfield units to bone mineral density (BMD) values [2,4,7,8,10,16] and provide an accurate measure of bone strength [31], a criterion that can discriminate patients at risk for hip fracture [6]. However, unlike numerous FE models predicting human femoral strength [2,4,7,8,10,16], the one study dealing with FAI correction [20] relied on a single femur with simplified linear elastic material properties (ie, no microcracks) and no direct experimental validation.…”