Njeh C F, Fuerst T, Hans D, Blake G M, Genant H K
Department of Radiology, University of California, San Francisco, USA.
Appl Radiat Isot. 1999 Jan;50(1):215-36. doi: 10.1016/s0969-8043(98)00026-8.
Osteoporosis is a systematic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue which leads to diminished biomechanical competence of the skeleton and low-trauma or atraumatic fractures. Due to increased awareness of the impact of osteoporosis on the elderly population, the use of bone densitometric techniques is becoming more widespread. Considerable progress has been made in the development of non-invasive methods for the assessment of the skeleton. While DXA and QCT are commonly used techniques, the popularity of other approaches such as RA, SXA and QUS is gaining grounds. QCT has an advantage over the other techniques in its ability to measure the true volumetric density of trabecular or cortical bone. We therefore present an overview of these current techniques for bone mineral density (BMD) measurements. In the second section we discuss the radiation doses incurred in BMD measurements by patients and methods for reducing patient and staff radiation exposure are given. Studies of radiation dose to patient from DXA confirms that patient dose is small (0.08-4.6 muSv) compared to that given by many other investigations involving ionizing radiation. Fan beam technology with increased resolution has resulted in increase patient dose radiation dose (6.7-31 muSv) but this is still relatively small. Carrying vertebral morphometry using DXA also incurs less radiation dose (< 60 muSv) than standard lateral radiographs QCT has radiation dose (25-360 muSv) comparable to simple radiological examination such as chest X-ray but lower than imaging CT. Radiation dose from other techniques such as RA and SXA are in the same order of magnitude as pencil beam DXA. For pencil beam DXA and SXA systems the time average dose to staff from scatter is very low even with the operator sitting as close as 1 m from the patient during measurement. However the scatter dose from fan beam DXA systems is considerable higher and approaches limits set by regulator bodies for occupational exposure.
骨质疏松症是一种全身性骨骼疾病，其特征为骨量低和骨组织微结构退化，导致骨骼生物力学性能下降以及低创伤或无创伤性骨折。由于对骨质疏松症对老年人群影响的认识不断提高，骨密度测量技术的应用越来越广泛。在无创评估骨骼的方法开发方面已经取得了相当大的进展。虽然双能X线吸收法（DXA）和定量计算机断层扫描（QCT）是常用技术，但其他方法如电阻抗法（RA）、单能X线吸收法（SXA）和定量超声（QUS）的普及程度也在不断提高。QCT在测量小梁骨或皮质骨的真实体积密度方面比其他技术具有优势。因此，我们概述了这些当前用于骨密度（BMD）测量的技术。在第二部分中，我们讨论了患者在BMD测量中所接受的辐射剂量，并给出了减少患者和工作人员辐射暴露的方法。对DXA给患者带来的辐射剂量的研究证实，与许多其他涉及电离辐射的检查相比，患者剂量很小（0.08 - 4.6微希沃特）。具有更高分辨率的扇形束技术导致患者辐射剂量增加（6.7 - 31微希沃特），但这仍然相对较小。使用DXA进行椎体形态测量所产生的辐射剂量（< 60微希沃特）也比标准侧位X线片少。QCT的辐射剂量（25 - 360微希沃特）与胸部X线等简单放射学检查相当，但低于CT成像。其他技术如RA和SXA的辐射剂量与笔形束DXA处于同一数量级。对于笔形束DXA和SXA系统，即使在测量期间操作员距离患者仅1米，散射对工作人员的时间平均剂量也非常低。然而，扇形束DXA系统的散射剂量要高得多，接近监管机构规定的职业暴露限值。
