Research On A Wide Fan-beam Dual Energy X-ray Absorptiometry

Dual energy X-ray absorptiometry provides accurate bone mineral density and bone mineral content of all parts of human body. Its reliable results can be used in conjunction with the clinical risk factors as an aid to the physician in diagnosis of osteoporosis and other medical conditions leading to reduced bone density and ultimately the determination of fracture risk. Dual energy X-ray absorptiometry serves as a golden standard in bone mineral detection due to its high accuracy, low dose, fast scanning speed and images with high definition. However, most of dual energy X-ray absorptiometry are primarily performed to obtain bone mineral density of total body, especially spine or hip. These devices are expensive and relatively high-dose so that they are not appropriate for general bone physical examinations and some special conditions where scanning bed is not preferred by subjects.Aims at offering a better solution to the problems above, this paper focuses on fan-beam dual energy X-ray bone mineral densitometry, studies system design and algorithm improvement and proposes a cost-effective system utilizing wide fan-beam dual energy X-ray for the forearm. A series of experiments proves that this system would give good dual energy spectrum and accurate bone mineral density results of human ultra-forearm because of its developed algorithm and special system design. The main achievements of this work are as follows:Firstly, current means and devices of bone mineral densitometry is deeply researched to give a better understanding of the present development of the dual energy X-ray absorptiometry.Secondly, a new system using wide fan-beam dual energy X-ray for the forearm.is proposed, according to the demand for accuracy, efficiency and cost. Simulation experiments affirms that the system has good dual energy spectrum and high intensity of photons.Thirdly, conic and cubic surface equations to directly approximate the dual energy equations and their inverses are carried out in the solution to the attenuation of dual energy X-ray with wide spectrum, based on the interaction between X-ray photons and objects. Simulation experiments verify the validity and accuracy of the algorithm used in the proposed system. An improvement using piecewise fitting method develops the area where errors are larger.Fourthly, a series of experiments are conducted in the real experimental bed. Results are acquired by X-ray scanning the test pieces that are precisely familiar with the component of human bone, and fitted by conic and cubic surface equations algorithm. Error analysis are made accordingly.Finally, a new beam-stop array method for scatter correction is applied in this bone mineral densitometry system. Experiments’results indicate that the new method for scatter correction works well and makes contribution to the system accuracy.