摘要
目的 对MRI信噪比影响因素进行实验研究 ,验证信噪比与部分扫描参数的关系。方法 利用Magphan体模在 1 5T高场和 0 15T低场MR设备上进行实验 ,利用体模均匀层图像测量信噪比。改变的扫描参数有激励次数 (NEX)、矩阵和层厚。使用的序列有自旋回波 (SE)、快速自旋回波(FSE)和梯度回波 (GRE)序列。结果 (1)NEX :得到NEX分别为 2、3、4的信噪比与NEX为 1的信噪比的比值。高场设备A结果为 1 13、0 99、0 99(10mm层厚 ) ;高场设备B的结果为 1 44、1 68、2 0 2(6mm层厚 )和 1 42、1 75、1 93 (3mm层厚 ) ;低场设备C结果为 1 5 1、2 0 3 (NEX分别为 2和 4)。 (2 )矩阵 (保持扫描野不变 ) :得到设备A矩阵为 192× 2 5 6、5 12× 5 12的信噪比与 2 5 6× 2 5 6的信噪比的比值。SE结果为 10 5 %和 45 % ;FSE结果为 96%和 5 4% ;GRE(T1)结果为 111%和 71% ;GRE(T2 )结果为 110 %和 63 %。 (3 )层厚 :得到设备A层厚为 2、6mm的信噪比与 10mm信噪比的比值。SE结果为 41%、10 5 % ;FSE结果为 43 %、69% ;GRE(T1)结果为 43 %、80 % ;GRE(T2 )结果为 3 3 %、75 %。结论 (1)对于高场设备 ,如无特殊要求NEX应≤ 2 ,低场设备增加NEX对提高信噪比有效。 (2 )矩阵对信噪比的影响比理论值小 。
Objective To research signal to noise ratio (SNR) of MRI and to verify the relationship between SNR and some scan parameters Methods The Magphan phantom was used to do experiments on 1 5 T and 0 15 T MR sets The uniformity module image was used to measure SNR Altering parameters such as NEX, matrix, and slice thickness and altering pulse sequences such as SE, FSE,and GRE Results (1) NEX: Comparing the SNR results with NEX of 2, 3, and 4, respectively to the result of NEX=1, the results of set A were 1 13, 0 99, and 0 99(10 mm), the results of set B were 1 44, 1 68, and 2 02 (6 mm) and were 1 42, 1 75, and 1 93 (3 mm),and the results of set C were 1 51 and 2 03 (NEX = 2, 4) (2) Matrix (keeping field of view constant): Comparing the SNR results of 192×256 and 512×512 to the result of 256×256 on set A, the results of SE were 105% and 45%, the results of FSE were 96% and 54%, the results of GRE (T 1 ) were 111% and 71%, and the results of GRE (T 2) were 110% and 63% (3) Slice thickness: Comparing the SNR results of 2 and 6 mm slice thickness to the result of 10 mm slice thickness on set A, the results of SE were 41% and 105%, the results of FSE were 43% and 69%, the results of GRE (T 1 ) were 43% and 80%, and the results of GRE (T 2) were 33% and 75% Conclusion (1) For high field set, the NEX should be ≤2 if no special request is required For low field set, increasing NEX is an effective method for enhancing SNR (2) The influence degree of matrix is less than ideal value So when matrix is selected, SNR, scan time, and imaging position should be considered (3) For high field set,thin slice thickness may be selected For low field set, thick slice thickness should be selected Many factors which can affect SNR should be considered In order to get high quality MR image, the selection of scan parameters should base on the SNR law and the characteristic of MR system and pulse sequence
出处
《中华放射学杂志》
CAS
CSCD
北大核心
2003年第3期225-227,共3页
Chinese Journal of Radiology
关键词
MRI
扫描参数
信噪比
实验研究
Signal processing, computer assisted
Magnetic resonance imaging
Factor analysis, statistical
