Quantitative computed tomography. Eur J Radiol
ABSTRACT Quantitative computed tomography (QCT) was introduced in the mid 1970s. The technique is most commonly applied to 2D slices in the lumbar spine to measure trabecular bone mineral density (BMD; mg/cm(3)). Although not as widely utilized as dual-energy X-ray absortiometry (DXA) QCT has some advantages when studying the skeleton (separate measures of cortical and trabecular BMD; measurement of volumetric, as opposed to 'areal' DXA-BMDa, so not size dependent; geometric and structural parameters obtained which contribute to bone strength). A limitation is that the World Health Organisation (WHO) definition of osteoporosis in terms of bone densitometry (T score -2.5 or below using DXA) is not applicable. QCT can be performed on conventional body CT scanners, or at peripheral sites (radius, tibia) using smaller, less expensive dedicated peripheral CT scanners (pQCT). Although the ionising radiation dose of spinal QCT is higher than for DXA, the dose compares favorably with those of other radiographic procedures (spinal radiographs) performed in patients suspected of having osteoporosis. The radiation dose from peripheral QCT scanners is negligible. Technical developments in CT (spiral multi-detector CT; improved spatial resolution) allow rapid acquisition of 3D volume images which enable QCT to be applied to the clinically important site of the proximal femur, more sophisticated analysis of cortical and trabecular bone, the imaging of trabecular structure and the application of finite element analysis (FEA). Such research studies contribute importantly to the understanding of bone growth and development, the effect of disease and treatment on the skeleton and the biomechanics of bone strength and fracture.
- SourceAvailable from: Yunhua Luo
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- "A sequence of cross-sectional images of tissues are produced in quantitative computed tomography (QCT) based on the amount of X-ray absorbed or attenuated by different tissues through which the X-ray travels . The amount of X-ray absorbed by the tissue at a specific location is expressed as CT number and measured by Hounsfield Unit (HU) in the image. "
ABSTRACT: In the existing finite element head models (FEHMs) that are constructed from medical images, head tissues are usually segmented into a number of components according to the interior anatomical structure of the head. Each component is represented by a homogenous material model. There are a number of disadvantages in the segmentation-based finite element head models. Therefore, we developed a nonsegmentation finite element head model with pointwise-heterogeneous material properties and corroborated it by available experiment data. From the obtained results, it was found that although intracranial pressures predicted by the existing (piecewise-homogeneous) and the proposed (pointwise-heterogeneous) FEHM are very similar to each other, strain/stress levels in the head tissues are very different. The maximum peak strains/stresses predicted by the proposed FEHM are much higher than those by the existing FEHM, indicating that piecewise-homogeneous FEHM may have underestimated the stress/strain level induced by impact and thus may be inaccurate in predicting traumatic brain injuries.Applied Bionics and Biomechanics 01/2015; 2015:1-8. DOI:10.1155/2015/837585 · 0.47 Impact Factor
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- "Thus, in 2000, the National Institute of Health defined in addition to a decreased bone mass new « quality » criteria for the diagnosis of osteoporosis. As these quality criteria are not evaluated by DXA, alternative imaging techniques have been developed to assess bone microarchitecture and improve the fracture risk prediction      . "
ABSTRACT: PURPOSE: Femoral neck fracture is a major public health problem in elderly persons, representing the main source of osteoporosis-related mortality and morbidity. In this study, we aimed at comparing radiographic texture analysis with three-dimensional (3D) microarchitecture in human femurs, and at evaluating whether bone texture analysis improved the assessment of the femoral neck fracture risk other than that obtainable by bone mineral density (BMD). MATERIALS AND METHODS: Thirteen osteoporotic femoral heads from patients who fractured their femoral neck and twelve non-fractured femoral heads from osteoarthritic patients were studied using respectively (1) a new high-resolution digital X-ray device (BMA™, D3A Medical Systems) allowing for bone texture analysis with fractal parameter Hmean, and (2) a micro-computed tomograph (CT) for 3D microarchitecture. BMD was measured postoperatively by DXA in all patients in the contralateral femur. RESULTS: In these femoral heads, we found that fractal parameter Hmean was correlated with 3D microarchitecture parameters: bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular separation (Tb.Sp) and fractal dimension (FD) respectively (p<0.05). Then, fractal parameter Hmean was significantly lower in the femoral heads from the fractured group than from the non-fractured group (p<0.01). Finally, multiple regression analysis showed that combining bone texture analysis and total hip BMD significantly improved the estimation of the femoral neck fracture risk from adjusted r(2)=0.46 to adjusted r(2)=0.67 (p<0.05). CONCLUSION: Radiographic bone texture analysis was correlated with 3D microarchitecture parameters in the femoral head, provided accurate discrimination between the femoral heads from the fractured and non-fractured groups, and significantly improved the estimation of the femoral neck fracture risk when combined with BMD.European journal of radiology 06/2013; 82(9). DOI:10.1016/j.ejrad.2013.04.042 · 2.16 Impact Factor
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ABSTRACT: Although dual-energy absorptiometry (DXA) has proven its clinical utility, there are many limitations to using areal bone mineral density (aBMD) measured by DXA to predict bone strength and fracture risk. Recent advances in imaging techniques including quantitative computed tomography (QCT) and magnetic resonance imaging (MRI) have led to non-invasive assessment of bone macro-architecture and micro-architecture. Analysis techniques such as finite element (FE) modelling use image data to estimate the ability of a bone to carry load, and provide new insight into treatment effects and fracture risk. QCT and MRI can image clinically relevant sites such as the lumbar spine and proximal femur. High-resolution peripheral QCT (HR-pQCT) offers superior resolution at peripheral sites including the radius and tibia. Measures obtained from QCT and HR-pQCT have been significantly associated with fracture risk independently of DXA-derived parameters. FE models derived from QCT, HR-pQCT, and MRI are capable of detecting treatment-induced changes in bone strength, and preliminary results suggest that QCT and HR-pQCT-derived FE models can discriminate fracture cases from controls. Continued advances in image acquisition and analysis will improve our ability to predict fracture and to understand factors associated with bone strength. KeywordsBone strength-Quantitative computed tomography-High-resolution peripheral quantitative computed tomography-Magnetic resonance imaging-Finite element modellingClinical Reviews in Bone and Mineral Metabolism 09/2010; 8(3):122-134. DOI:10.1007/s12018-009-9066-2