Klumpp Bernhard, Fenchel Michael, Hoevelborn Tobias, Helber Uwe, Scheule Albertus, Claussen Claus, Miller Stephan
Department of Diagnostic Radiology, Eberhard-Karls-University Tuebingen, Hoppe-Seyler-Strasse 3, 72076 Tuebingen, Germany.
Invest Radiol. 2006 Sep;41(9):661-7. doi: 10.1097/01.rli.0000233321.82194.09.
Cardiac magnetic resonance imaging (MRI) at 3.0 T has recently become available and potentially provides a significant improvement of tissue contrast in T1-weighted imaging techniques relying on Gd-based contrast enhancement. Imaging at high-field strength may be especially advantageous for methods relying on strong T1-weighting and imaging after contrast material administration. The aim of this study was to compare cardiac delayed enhancement (DE) MRI at 3.0 T and 1.5 T with respect to image quality, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) between infarcted and normal myocardium.
Forty consecutive patients with history of myocardial infarction were examined at 3.0 T (n = 20) or at 1.5 T (n = 20). Myocardial function was assessed using cine steady-state-free-precession (SSFP) sequences (TR 3.1 milliseconds, TE 1.6 milliseconds, flip angle 70 degrees , and a matrix of 168 x 256 at 1.5 T and TR 3.4 milliseconds, TE 1.7 milliseconds, flip angle 50 degrees and a matrix of 168 x 256 at 3.0 T), acquired in long- and short-axes views. DE images were obtained 15 minutes after the administration of 0.15 mmol of Gd-DTPA/kg body weight using a segmented inversion recovery prepared gradient echo sequence at 1.5 T (TR 9.6 milliseconds, TE 4.4 milliseconds, flip angle 25 degrees , matrix 160 x 256, bandwidth 140 Hertz/pixel) and at 3.0 T (TR 9.8 milliseconds, TE 4.3 milliseconds, flip angle 30 degrees , matrix 150 x 256, bandwidth 140 Hertz/pixel). For image analysis, standardized SNR and CNR measurements were performed in infarcted and remote myocardial regions. Two independent observers rated image quality on a 4-point scale (0 = poor image quality, 1 = sufficient image quality, 2 = good image quality, 3 = excellent image quality).
High diagnostic image quality was obtained in all patients. Rating of mean image quality was 2.2 +/- 0.8 at 1.5 T and 2.5 +/- 0.6 at 3.0 T (P = 0.012) for observer 1 and 2.2 +/- 0.7 at 1.5 T and 2.6 +/- 0.6 at 3.0 T (P = 0.003) for observer 2, respectively. Interobserver agreement was good (kappa = 0.68 at 1.5 T and 0.78 at 3.0 T). SNR measurements yielded a mean SNR of 37.8 +/- 13.9/22.9 +/- 6.0 in infarcted myocardium (P < 0.001) and 5.6 +/- 2.2/5.9 +/- 2.4 in normal myocardium (P = 0.45) at 3.0 T/1.5 T, respectively. CNR measurements revealed mean values of 32.4 +/- 13.0/16.7 +/- 5.4 (P< 0.001) at 3.0 T/1.5 T, respectively.
Delayed enhancement MRI at 3.0 T is feasible and provides superior image quality compared with 1.5 T. Furthermore, using identical contrast doses, increased SNR and CNR values were recorded at 3.0 T.
3.0 T心脏磁共振成像（MRI）近期已可实现，并且在依赖基于钆的对比增强的T1加权成像技术中可能显著改善组织对比度。高场强成像对于依赖强T1加权及对比剂注射后成像的方法可能特别有利。本研究的目的是比较3.0 T和1.5 T心脏延迟增强（DE）MRI在梗死心肌与正常心肌之间的图像质量、信噪比（SNR）及对比噪声比（CNR）。
连续40例有心肌梗死病史的患者分别在3.0 T（n = 20）或1.5 T（n = 20）下接受检查。使用电影稳态自由进动（SSFP）序列评估心肌功能（1.5 T时TR 3.1毫秒，TE 1.6毫秒，翻转角70度，矩阵168×256；3.0 T时TR 3.4毫秒，TE 1.7毫秒，翻转角50度，矩阵168×256），采集长轴和短轴视图。在静脉注射0.15 mmol钆喷酸葡胺/千克体重后15分钟，使用分段反转恢复准备梯度回波序列分别在1.5 T（TR 9.6毫秒，TE 4.4毫秒，翻转角25度，矩阵160×256，带宽140赫兹/像素）和3.0 T（TR 9.8毫秒，TE 4.3毫秒，翻转角30度，矩阵150×256，带宽140赫兹/像素）获得DE图像。对于图像分析，在梗死心肌区域和远隔心肌区域进行标准化SNR和CNR测量。两名独立观察者以4分制对图像质量进行评分（0 = 图像质量差，1 = 图像质量足够，2 = 图像质量好，3 = 图像质量优）。
所有患者均获得了高诊断图像质量。观察者1在1.5 T时平均图像质量评分为2.2±0.8，在3.0 T时为2.5±0.6（P = 0.012）；观察者2在1.5 T时平均图像质量评分为2.2±0.7，在3.0 T时为2.6±0.6（P = 0.003）。观察者间一致性良好（1.5 T时kappa = 0.6,3.0 T时kappa = 0.78）。SNR测量结果显示，在3.0 T/1.5 T时，梗死心肌的平均SNR分别为37.8±13.9/22.9±6.0（P < 0.001），正常心肌的平均SNR分别为5.6±2.2/5.9±2.4（P = 0.45）。CNR测量结果显示，在3.0 T/1.5 T时，平均值分别为32.4±13.0/16.7±5.4（P < 0.001）。
3.0 T延迟增强MRI是可行的，与1.5 T相比可提供更优的图像质量。此外，在使用相同对比剂剂量的情况下，3.0 T时记录到更高的SNR和CNR值。
