Yamada Kazutaka, Wisner Erik R, de Ropp Jeff S, LeCouteur Richard A, Tripp Linda D
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Vet Radiol Ultrasound. 2002 Nov-Dec;43(6):518-27. doi: 10.1111/j.1740-8261.2002.tb01042.x.
The aim of the study was to assess the effects of changing acquisition parameters used for high-resolution in vivo magnetic resonance (MR) microscopy on image quality and scan time. The head or abdomen of 11 normal and 1 glioblastoma-bearing anesthetized BALB/c mice were imaged using a high-resolution 7.0-Tesla magnet. Scan parameters such as matrix size (MTX), slice thickness (ST), number of excitations (NEX), pulse sequence type including repetition time (TR) and echo time (TE), respiratory gating, and intraperitoneal contrast medium administration were altered to assess their actual effect on signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) as compared to calculated effects. As expected, SNR increased with increasing ST or NEX and with decreasing MTX. However, although the empirical increase in SNR was similar to that expected for increased ST, it was less than that anticipated for increasing NEX or decreasing MTX. Increasing NEX and applying respiratory gating both increased SNR and reduced the image degradation associated with respiratory motion in images of the abdomen. Intraperitoneal contrast medium administration produced a marked increase in CNR in the subject with the implanted glioblastoma, suggesting that this route is satisfactory for the enhancement of lesions disrupting the blood-brain barrier. The consequence of improving image quality in terms of spatial and contrast resolution is increased scan time. However, the actual increase in SNR when altering acquisition parameters may not be as much as predicted by theory.
本研究的目的是评估改变用于高分辨率体内磁共振（MR）显微镜检查的采集参数对图像质量和扫描时间的影响。使用高分辨率7.0特斯拉磁体对11只正常麻醉的BALB/c小鼠和1只患有胶质母细胞瘤的麻醉BALB/c小鼠的头部或腹部进行成像。改变扫描参数，如矩阵大小（MTX）、层厚（ST）、激励次数（NEX）、脉冲序列类型（包括重复时间（TR）和回波时间（TE））、呼吸门控以及腹腔内造影剂给药，以评估它们对信噪比（SNR）、对比噪声比（CNR）的实际影响，并与计算结果进行比较。正如预期的那样，SNR随着ST或NEX的增加以及MTX的减小而增加。然而，尽管SNR的实际增加与ST增加时预期的增加相似，但小于NEX增加或MTX减小时预期的增加。增加NEX和应用呼吸门控均增加了SNR，并减少了腹部图像中与呼吸运动相关的图像退化。腹腔内造影剂给药使植入胶质母细胞瘤的受试者的CNR显著增加，这表明该途径对于增强破坏血脑屏障的病变是令人满意的。在空间和对比分辨率方面提高图像质量的结果是扫描时间增加。然而，改变采集参数时SNR的实际增加可能不如理论预测的那么多。
