Chen Xinyuan, Dai Jianrong
Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
J Appl Clin Med Phys. 2018 May;19(3):326-335. doi: 10.1002/acm2.12311. Epub 2018 Mar 24.
Magnetic Resonance Imaging (MRI) simulation differs from diagnostic MRI in purpose, technical requirements, and implementation. We propose a semiautomatic method for image acceptance and commissioning for the scanner, the radiofrequency (RF) coils, and pulse sequences for an MRI simulator. The ACR MRI accreditation large phantom was used for image quality analysis with seven parameters. Standard ACR sequences with a split head coil were adopted to examine the scanner's basic performance. The performance of simulation RF coils were measured and compared using the standard sequence with different clinical diagnostic coils. We used simulation sequences with simulation coils to test the quality of image and advanced performance of the scanner. Codes and procedures were developed for semiautomatic image quality analysis. When using standard ACR sequences with a split head coil, image quality passed all ACR recommended criteria. The image intensity uniformity with a simulation RF coil decreased about 34% compared with the eight-channel diagnostic head coil, while the other six image quality parameters were acceptable. Those two image quality parameters could be improved to more than 85% by built-in intensity calibration methods. In the simulation sequences test, the contrast resolution was sensitive to the FOV and matrix settings. The geometric distortion of simulation sequences such as T1-weighted and T2-weighted images was well-controlled in the isocenter and 10 cm off-center within a range of ±1% (2 mm). We developed a semiautomatic image quality analysis method for quantitative evaluation of images and commissioning of an MRI simulator. The baseline performances of simulation RF coils and pulse sequences have been established for routine QA.
磁共振成像（MRI）模拟在目的、技术要求和实施方面与诊断性MRI有所不同。我们提出了一种半自动方法，用于对MRI模拟器的扫描仪、射频（RF）线圈和脉冲序列进行图像验收和调试。使用美国放射学会（ACR）MRI认证大尺寸体模对七个参数进行图像质量分析。采用带有分体头部线圈的标准ACR序列来检查扫描仪的基本性能。使用标准序列和不同的临床诊断线圈来测量和比较模拟RF线圈的性能。我们使用带有模拟线圈的模拟序列来测试图像质量和扫描仪的高级性能。开发了用于半自动图像质量分析的代码和程序。当使用带有分体头部线圈的标准ACR序列时，图像质量通过了所有ACR推荐标准。与八通道诊断头部线圈相比，模拟RF线圈的图像强度均匀性降低了约34%，而其他六个图像质量参数是可接受的。通过内置的强度校准方法，这两个图像质量参数可以提高到85%以上。在模拟序列测试中，对比分辨率对视野（FOV）和矩阵设置敏感。T1加权和T2加权等模拟序列的几何畸变在等中心和偏离中心10 cm处得到了很好的控制，偏差范围在±1%（2 mm）以内。我们开发了一种半自动图像质量分析方法，用于对图像进行定量评估和MRI模拟器的调试。已建立模拟RF线圈和脉冲序列的基线性能，用于常规质量保证（QA）。
