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求帮忙翻译一下（有效期至2009年4月8日）
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Precise measurement of vertebral bone density using computed tomography without the use of an external reference phantom 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 bone density in Icelandic women using quantitative computed tomography without an external reference phantom 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. |
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wy_why007(金币+1,VIP+0):能否翻译的好一点，google翻译的我也弄过，总觉得不是特别好 3-25 07:46
wy_why007(金币+1,VIP+0):能否翻译的好一点，google翻译的我也弄过，总觉得不是特别好 3-25 07:46
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用电脑断层扫描精确测量腰椎骨密度，而不需使用外部参考幻像 骨密度测定的定量CT （ QCT ）部门普遍使用的是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，体积平均的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照标准，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中的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 ，或取得了3.5毫米的精度优于1 ％的正常人和1 ％至2 ％的骨质疏松症患者-双重改进了精度从类似的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。 |
2楼2009-03-24 13:09:33