Monte Carlo modelling of an extended DXA technique
| Autor: | Gregory Michael, C J Henderson |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
musculoskeletal diseases
Radiography Monte Carlo method Osteoporosis Biophysics Bone healing Models Biological Biophysical Phenomena Absorptiometry Photon Bone Density medicine Humans Radiology Nuclear Medicine and imaging Quantitative computed tomography Osteoporosis Postmenopausal Bone mineral Radiological and Ultrasound Technology medicine.diagnostic_test Phantoms Imaging business.industry Soft tissue medicine.disease Standard technique Adipose Tissue Connective Tissue Female business Nuclear medicine Monte Carlo Method |
| Zdroj: | Physics in Medicine and Biology. 43:2583-2596 |
| ISSN: | 1361-6560 0031-9155 |
| Popis: | The precision achieved in measuring bone mineral density (BMD) by commercial dual-energy x-ray absorptiometry (DXA) machines is typically better than 1%, but accuracy is considerably worse. Errors, due to inhomogeneous distributions of fat, of up to 10% have been reported. These errors arise because the DXA technique assumes a two-component model for the human body, i.e. bone mineral and soft tissue. This paper describes an extended DXA technique that uses a three-component model of human tissue and significantly reduces errors due to inhomogeneous fat distribution. In addition to two x-ray transmission measurements, a measurement of the path length of the x-ray beam within the patient is required. This provides a third equation, i.e. T DtsCtbCtf where T , ts , tb and tf are the total, lean soft tissue, bone mineral and fatty tissue thicknesses respectively. Monte Carlo modelling was undertaken to make a comparison of the standard and extended DXA techniques in the presence of inhomogeneous fat distribution. Two geometries of varying complexity were simulated. In each case the extended DXA technique produced BMD measurements that were independent of soft tissue composition whereas the standard technique produced BMD measurements that were strongly dependent on soft tissue composition. For example, in one case, the gradients of the plots of BMD versus fractional fat content were for standard DXA . 0:183 0:037/ gc m 2 and for extended DXA .0:027 0:044/ gc m 2 . In all cases the extended DXA method produced more accurate but less precise results than the standard DXA technique. In vivo analysis of tissue composition is an important diagnostic tool in clinical medicine and a number of physical methods exist for estimating tissue and whole body composition. Radiographic methods are particularly well suited to in vivo determination of bone mineral density (BMD) due to the relatively high x-ray absorption properties of bone mineral compared with other tissues. The modern radiographic techniques of measuring bone mineral content which are considered to form the basis of techniques for quantitative assessment of the skeleton are (Genant 1990) single-energy quantitative computed tomography, dual-energy quantitative computed tomography, single-photon absorptiometry, dual-photon absorptiometry and dual-energy x-ray absorptiometry (DXA). More than any other technique, it is DXA that has established bone mineral measurements in routine clinical practice (Fogelman and Blake 1994). Recent applications of BMD measurement include measurement of bone formation during leg lengthening, BMD changes around orthopaedic implants, assessment of fracture healing (Cattermole and Cunningham 1995) and body composition measurements in obese individuals (Tataranni and Ravussin 1995). However, BMD measurement is most commonly used in the diagnosis of osteoporosis. |
| Databáze: | OpenAIRE |
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