Cardiac Cine MRI at 3.0 Tesla: Comparison of Image Quality between SSFP and FLASH Sequence

Abstract

IntroductionThe clinical use of cardiac magnetic resonance imaging MRI has increased in recent years, especially for whole-heart coronary MR angiography and the identi cation of myocardial ischemia by perfusion study. The functional cardiac exam is a fundamental method for many cardiac MRI investigations. This exam can be performed using either the steady-state free precession SSFP or fast low angle shot FLASH method.The FLASH technique-based gradient echo sequence was introduced in 19861 . The features of this sequence are RF pulse with low ip angle, short repetition time 2-20 msec 2 , and a spoiler pulse that can reduce the effect of residual transverse magnetization 3 . The SSFP sequence is also a gradient echo sequence with low ip angle and short Abstract : This study compared steady-state free precession SSFP with Fast Low Angle Shot FLASH at 3.0 T cardiac Cine MRI with respect to contrast to noise ratio CNR and visual image quality assessment. All images were acquired on a 3.0-T Siemens MAGNETOM trio. Seven healthy volunteers all males, mean age 32.5 7.1 years underwent magnetic resonance imaging using SSFP and FLASH sequence on the same day. For both SSFP and FLASH imaging, 8-mm thick short axis and long axis views were acquired with equal matrix size 192 192 . CNR calculations were performed on the short axis images acquired at end systole time points. Three radiologists independently assessed image quality. SSFP images were superior to FLASH images with respect to CNR SSFP : 7.14 2.16, FLASH : 3.57 1.83, P 0.001 . In image quality, SSFP images were superior to FLASH in both short and long axis views P 0.01 . Although SSFP images contained dark blood artifacts in 3 cases, these images were improved by frequency offset. SSFP sequences provided higher quality images than FLASH sequences, and would be available for cardiac cine MRI at 3.0 T. [5][6][7] . At 3.0 T, the higher field strength enables a higher signal to noise ratio SNR and contrast to noise ratio CNR . However, the SSFP sequence is more limited by the specific absorption rate SAR or specific artifact, and SAR increases with field strength. The rst solution to this problem is to decrease the ip angle, but this worsens contrast [8][9][10] . At 3.0 T cine MRI, SSFP is reportedly slightly superior to FLASH sequence in terms of CNR and visual image quality assessment 11 , but 3.0 T MRI has been improved in terms of susceptibility or sequence optimization since that study.This study compared SSFP and FLASH sequence images with respect to CNR, the presence of artifacts and visual image quality at 3.0 T MRI. Materials and MethodsSeven volunteers mean age 32.5 7.1 years, age range 25-42 years, all males without any known history of diabetes, hypertension, renal failure, or cardiac disease were enrolled in this study. All examinations were performed using a 3.0-T MRI system MAGNETOME Trio A Tim System ; Siemens Medical Solutions, Erlangen, Germany with a 6-ch balance coil and 6-ch spinal balance coil. The parameters for the SSFP sequence were as follows :