Chandra R, Rusinek H
Department of Radiology, New York University Medical Center, New York 10016.
Med Phys. 1993 Jul-Aug;20(4):1071-5. doi: 10.1118/1.597003.
Random noise and MR signal uniformity were analyzed for a period of 9 months using two head coils on a 1.5 T commercial imager. Signal response from a cylindrical phantom filled with a 0.1 mmol/L CuSO4 solution was incorporated in a correction scheme and the effect of correction on uniformity and accuracy of tissue volume determination was measured. There was little change in random noise (CV < 5%) and image uniformity (CV < 15%) over the time of the study. The uniformity in a 130 cm2 region was 4% for a double saddle coil and 5.3% for a mirror coil. After correction, uniformity was improved to 1.1% for the double saddle coil and 1.2% for the mirror coil. In a 40 cm2 central region the uniformity was approximately three times better than in the 130 cm2 region. A second phantom, mimicking the relaxation times of CSF and the brain, consisted of saline encapsulated in vials of volume ranging from 35.6 ml to 249.6 ml and placed in a 0.1 mmol/L solution of MnCl2. Uniformity correction reduced the average error in volume measurement from 8.6% to 6.1%.
在一台1.5T的商用成像仪上，使用两个头部线圈对随机噪声和磁共振信号均匀性进行了为期9个月的分析。将填充有0.1mmol/L硫酸铜溶液的圆柱形模体的信号响应纳入校正方案，并测量校正对组织体积测定的均匀性和准确性的影响。在研究期间，随机噪声（CV<5%）和图像均匀性（CV<15%）几乎没有变化。对于双鞍形线圈，130cm²区域的均匀性为4%，对于镜像线圈为5.3%。校正后，双鞍形线圈的均匀性提高到1.1%，镜像线圈提高到1.2%。在40cm²的中心区域，均匀性比130cm²区域大约好三倍。第二个模体模仿脑脊液和大脑的弛豫时间，由封装在体积从35.6ml到249.6ml的小瓶中的盐水组成，并放置在0.1mmol/L的氯化锰溶液中。均匀性校正将体积测量的平均误差从8.6%降低到6.1%。
