Nongated cardiac magnetic resonance imaging: preliminary experience at 0.12 T

Nongated cardiac magnetic resonance imaging (MRI) has been reported previously to be inadequate for obtaining diagnostic information. This study explored the role of pulse sequence in the degradation of the nongated cardiac image. Images of diagnostic quality were obtained by using single spin-echo sequences with a very short echo time (10-20 msec TE) on a 0.12-T developmental MR unit. Marked degradation of the image was noted with longer TEs, and it is concluded that the previous unfavorable reports using a nongated technique may have been due to the longer TEs used in other units. Short-TE technique was used to examine 34 patients with a variety of cardiac diseases. Eleven patients had ventricular aneurysms. These cases showed thinning of the myocardium, and four of them showed increased signal within the aneurysm, perhaps related to regionally slower blood flow. Twenty patients had enlargement of one or more cardiac chambers. Three of these patients had thrombus within an enlarged chamber, which was readily identified on MRI. Twelve patients had left ventricular hypertrophy that was concentric in 11. One patient demonstrated asymmetric septal hypertrophy. All four pericardial effusions were low in signal intensity, but this was related to the pulse sequence used. Six patients had extrinsic masses displacing the heart and distorting the chamber contour. One patient showed intracardiac invasion of tumor; this finding was not evident on the CT. One patient with ventricular septal defect (VSD) and corrected transposition was scanned. In addition to identifying the VSD and chamber hypertrophy, the malposition of the great vessels at the base of the heart was seen. Four postoperative patients were scanned; wire suture artifact did not preclude imaging. In conclusion, diagnostic information can be obtained from nongated cardiac images provided that the TE is very short (10-20 msec). Although quantitative functional data are not available from nongated images, qualitative and diagnostic information is possible and may suffice in certain circumstances.
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