MR imaging of the heart in patients after myocardial infarction: Effect of increasing intersection gap on measurements of left ventricular volume, ejection fraction, and wall thickness
Résumé
Abstract: PURPOSE: To determine the extent to which the number of planes imaged at magnetic resonance (MR) imaging could be reduced without modifying the volume and thickness of the left ventricle. MATERIALS AND METHODS: Sixty-one patients were examined after a myocardial infarction. The whole left ventricle was imaged by using 5-mm contiguous breath-hold cine MR short-axis sections with no gap (SA(ng)) (two-dimensional fast low-angle shot sequence, 9/4.8 [repetition time msec/echo time msec]). The effect of omitting in two (short-axis sections with 5-mm gap [SA(5mm)]) or two sections in three(short-axis sections with 10-mm gap [SA(10mm)]) was studied. RESULTS: In the comparison of SA(5mm) or SA(10mm) with respect to the reference SA(ng), standard Error of the estimate (SEE) for the diastolic volume did not exceed the 6.1% interobserver SEE, and the SEE for the ejection fraction remained lower than the 3% interobserver SEE. The measured wall thickness was not affected. In addition, six simple geometric models were compared with SA(ng) and yielded an SEE of 9.5%-28.1% for the diastolic volume and 3.8%-13.3% for the ejection fraction. CONCLUSION: In the study of left ventricles with heterogeneous contractility, short-axis imaging is more accurate than geometric modeling and permits wall thickness measurements when an intersection gap of 5 or 10 mm is used.