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Cardiac MRI function measurements are typically based on multiple breathhold 2D sequences to acquire images of the entire heart. In the present study, the feasibility of a cine 3D TrueFISP technique in which several complete volumetric measurements may be obtained during a single breathhold is demonstrated. In contrast to 3D FLASH, the TrueFISP sequence offers an excellent contrast between the myocardium and the intraventricular cavity without the use of contrast agent. An ECG-gated 3D cine TrueFISP sequence was implemented with a repetition time of 2.4–2.8 ms, which allows imaging of the complete heart within a single breathhold throughout 20–46 heartbeats with a 3D frame rate of 8–13 volumes per cardiac cycle and a spatial resolution of about 1.5 × 3.5 × 3.5 mm3. Breathhold volumetric cine imaging with the 3D TrueFISP technique holds promise for rapid and accurate evaluation of the cardiac regional wall motion and the calculation of cardiac volume and ejection fraction. Magn Reson Med 48:921–925, 2002. © 2002 Wiley-Liss, Inc.
Cine magnetic resonance imaging represents a method for quantification the 3D functional geometry of the ventricles (1–3). The standard methods for the acquisition of 2D datasets during a single breathhold include turbo-gradient echo sequence (4, 5), echo-planar imaging (EPI) (6), and spiral EPI (7). The drawback of these 2D methods is the reduced signal-to-noise ratio (SNR), the sensitivity to motion between scans, and a relatively poor contrast between the myocardium and the intraventricular blood volume. A multislice technique based on 2D TrueFISP acquisitions has proven to offer a superior contrast between myocardium and blood (8). For covering the complete heart, multiple breathholds are necessary to get the functional information in any desired plane of the ventricles. Multiple breathholds, however, require an increased acquisition time and lead to a possible mismatch of adjacent slices due to different breathhold positions.
In addition, using multiple breathholds can lead to problems during stress examinations due to the prolonged scan time. The assessment of the complete left ventricle may not be possible because the duration of the imaging procedure may exceed the longest acceptable duration of the stress test. This may be important because stress MR imaging with dobutamine has been shown to be superior to dobutamine stress echocardiography for the noninvasive detection of myocardial ischemia (9).
The recent development of high-performance gradient systems enables the acquisition of a single 3D cardiac dataset within a single breathhold. Previously proposed methods for volumetric imaging during a single breathhold are 3D FLASH techniques (10), EPI sequences (11), and segmented EPI techniques (12). Besides these single 3D acquisition techniques, a contrast-enhanced cine 3D projection technique with a temporal aperture of 60 ms within one breathhold has been developed (13). In the present study, we propose a cine 3D technique without the use of a contrast agent based on a balanced SSFP (steady-state free precession), or TrueFISP sequence. This imaging technique offers very high signal-to-noise ratio (SNR) and high contrast between myocardium and blood, which is necessary for the assessment of the left ventricular function. A further advantage as demonstrated in this application on cardiac imaging is the relative insensitivity of TrueFISP to flow and motion compared to FLASH-type sequences. With a TR of 2–3 ms, the imaging speed of TrueFISP offers the possibility to acquire time-resolved 3D datasets with a time resolution of 60–100 ms. The sensitivity of TrueFISP to off-resonance effects and eddy currents requires a carefully designed 3D acquisition scheme to minimize image artifacts. This was achieved by implementing a 3D trajectory with alternated reordering in the line-encoding direction that significantly reduced eddy current effects.
