Ito M, Hayashi K, Yamada N
Nihon Igaku Hoshasen Gakkai Zasshi. 1989 Aug 25;49(8):999-1008.
Quantitative computed tomography (QCT) has been found useful in the evaluation of vertebral bone mineral density (BMD). It separates cortical from trabecular bone in the vertebral bodies. The accuracy of QCT, however, is limited because of the existence of unknown amounts of marrow fat in the trabecular bone. The purpose of this study is to investigate the precision and accuracy of QCT, with a particular emphasis on the advantage of dual energy technique over single energy technique, as well as to investigate age-related change of BMD in patients with no metabolic disorders. For evaluation of BMD, SOMATOM DR-H CT scanner was used, which provided dual energy scan with rapid kilovolt peak switching system. The lumbar vertebrae (L1-L3) were exposed at the middle portion together with the calibration phantom (Ca10(PO4)6(OH)2 200 mg/ml, 0 mg/ml). KV-separated images (KV-HI, KV-LO) and material-separated images (MAT-HI, MAT-LO) were calculated from dual-energy scan data. KV-separated data were considered as SEQCT data. In experiment, dipotassium hydrogen phosphate (K2HPO4) solution was used to simulate bone mineral, water to simulate lean soft tissue and ethanol (C2H5OH) to simulate fat. To investigate the variations originating from marrow fat, a series of phantoms (K2HPO4-C2H5OH-H2O mixtures) with a constant 10 gm% K2HPO4 concentration but with the various mixtures of C2H5OH ranging from 0-40% by volume was scanned with dual energy technique. The value of BMD obtained from KV-separated data was reduced about 12% per 10% fat by volume increase, while the value obtained by DEQCT technique was reduced 5.5% per 10% fat by volume increase. With the dual energy technique the error was greatly reduced. On the other hand, the higher precision of KV-separated images compared to MAT-HI images was obtained, as well as the relatively higher precision for determining high rather than low fraction of mineral. In conclusion, with the single energy technique, precision is high, and with the dual energy technique, accuracy is high. It was also noted that selection of the CT section was the most critical factor in clinical BMD analysis. Age-related change of BMD in vertebral trabecular and cortical bone was studied in 161 patients without bone metabolic disorders. There were two peaks of BMD in females in their 20s and 30s, and a single peak in males in their 20s.(ABSTRACT TRUNCATED AT 400 WORDS)
定量计算机断层扫描（QCT）已被证明在评估椎体骨密度（BMD）方面很有用。它能区分椎体中的皮质骨和小梁骨。然而，由于小梁骨中存在未知量的骨髓脂肪，QCT的准确性受到限制。本研究的目的是调查QCT的精密度和准确性，特别强调双能技术相对于单能技术的优势，以及调查无代谢紊乱患者中与年龄相关的骨密度变化。为了评估骨密度，使用了SOMATOM DR - H CT扫描仪，它通过快速千伏峰值切换系统提供双能扫描。腰椎（L1 - L3）中部连同校准体模（Ca10(PO4)6(OH)2 200 mg/ml，0 mg/ml）一起进行扫描。从双能扫描数据计算出千伏分离图像（KV - HI，KV - LO）和物质分离图像（MAT - HI，MAT - LO）。千伏分离数据被视为SEQCT数据。在实验中，磷酸氢二钾（K2HPO4）溶液用于模拟骨矿物质，水用于模拟瘦软组织，乙醇（C2H5OH）用于模拟脂肪。为了研究源自骨髓脂肪的变化，用双能技术扫描了一系列体模（K2HPO4 - C2H5OH - H2O混合物），其K2HPO4浓度恒定为10 gm%，但C2H5OH的体积混合比例从0 - 40%不等。从千伏分离数据获得的骨密度值每10%体积的脂肪增加会降低约12%，而通过双能QCT技术获得的值每10%体积的脂肪增加会降低5.5%。使用双能技术时误差大大降低。另一方面，与MAT - HI图像相比，KV - 分离图像具有更高的精密度，并且在确定高矿物质比例而非低矿物质比例时具有相对更高的精密度。总之，单能技术精密度高，双能技术准确性高。还注意到CT层面的选择是临床骨密度分析中最关键的因素。在161例无骨代谢紊乱的患者中研究了椎体小梁骨和皮质骨中与年龄相关的骨密度变化。女性在20多岁和30多岁时有两个骨密度峰值，男性在20多岁时有一个峰值。（摘要截取自400字）
