英语翻译Bone density measurement by quantitative computed tomography (QCT) commonly uses an external reference phantom to decrease scan-to-scan and scanner-to-scanner variability.However,the peripheral location of these phantoms and other phantom

英语翻译Bone density measurement by quantitative computed tomography (QCT) commonly uses an external reference phantom to decrease scan-to-scan and scanner-to-scanner variability.However,the peripheral location of these phantoms and other phantom
英语翻译
Bone density measurement by quantitative computed tomography (QCT) commonly uses an external reference phantom to decrease scan-to-scan and scanner-to-scanner variability.However,the peripheral location of these phantoms and other phantom variables is also responsible for a measurable degradation in accuracy and precision.Due to non-uniform artifacts such as beam hardening,scatter,and volume averaging,the ideal reference phantom should be as close to the target tissue as possible.This investigation developed and tested a computer program that uses paraspinal muscle and fat tissue as internal reference standards in an effort to eliminate the need for an external phantom.Because of their proximity,these internal reference tissues can be assumed to reflect more accurately the local changes in the x-ray spectra and scatter distribution at the target tissue.A user interactive computerized histogram plotting technique enabled the derivation of reproducible CT numbers for muscle,fat,and trabecular bone.Preliminary results indicate that the use of internal reference tissues with the histogram technique may improve reproducibility of scan-to-scan measurements as well as inter-scanner precision.Reproducibility studies on 165 images with intentional region-of-interest (ROI) mispositioning of 1.5,2.5,or 3.5 mm yielded a precision of better than 1% for normals and 1% to 2% for osteoporotic patients--a twofold improvement over the precision from similar tests using the standard technique with an external reference phantom.Such improvements in precision are essential for QCT to be clinically useful as a noninvasive modality for measurement of the very small annual changes in bone mineral density.
Vertebral trabecular bone mineral density (BMD) was measured in 187 healthy Icelandic women,age 35-64 years,by quantitative computed tomography (QCT) with the use of internal references (muscle and subcutaneous fat) instead of the traditional external references (phantoms).We found a mean 2.4 mg/cm3 (1.8%) bone loss per year in the age range 35-64 years.There was an accelerated phase (exponential) after menopause,with 4% loss per year for the first 1-5 years after menopause or 5-fold trabecular bone loss compared with the subsequent 11-15 years after menopause.Reproducibility was found to be 1.9%.This method thus compares with traditional QCT measurements and is highly reproducible.We find QCT using internal references a promising method for assessing fracture risk in perimenopausal women and for follow-up in osteoporotic patients.

英语翻译Bone density measurement by quantitative computed tomography (QCT) commonly uses an external reference phantom to decrease scan-to-scan and scanner-to-scanner variability.However,the peripheral location of these phantoms and other phantom
骨密度测定的定量CT （ QCT ）部门普遍使用的外部参考幻像减少扫描到扫描和扫描仪的扫描仪可变性.然而,这些周边位置幻像幻影和其他变数还负责一个可以衡量的退化的准确度和精密度.由于非均匀文物如束硬化,分散,体积平均,理想参考幻像应接近目标组织的.这项调查开发和测试的一种计算机程序,使用椎旁肌肉和脂肪组织的内部参考标准,以努力消除无需外部幻像.因为他们的接近,这些内部参考组织可以假定,以更准确地反映当地变化的X射线谱和分散分布在靶组织.用户互动电脑直方图绘制技术使推导重复性的CT号码肌肉,脂肪,和骨小梁.初步结果显示,使用内部参考组织与直方图技术,可提高重复性的扫描,以扫描测量以及跨扫描仪的精度.重复性研究165图像故意感兴趣区域（ ROI ）的mispositioning 1.5 ,2.5 ,或3.5毫米取得了精度优于1 ％的正常人和1 ％至2 ％的骨质疏松症患者-一种双重的改进,从类似的精密测试使用的标准技术与外部参考幻像.这种改进是必不可少的精确定量的临床有用的无创方法测量非常小的年度变化骨密度.
椎体松质骨骨密度（ BMD ）测定187冰岛妇女健康,年龄35 〜 64岁,定量计算机断层扫描（ QCT ）部门与使用内部参考（肌肉和皮下脂肪） ,而不是传统的外部引用（幻影） .我们发现,平均2.4 mg/cm3 （ 1.8 ％ ） ,骨质流失,每年的年龄范围35 〜 64岁.有一个加速期（指数）绝经后,以4 ％的损失每年为第一绝经后1-5年或5倍的损失相比,骨小梁随后的11月15日与绝经后几年.重现被认为是1.9 ％ .这种方法比较,因此,与传统的定量测量和高度重复性.我们发现,定量使用内部参考一个有希望的方法来评估骨折风险,并在围绝经期妇女的后续骨质疏松患者.