| Abstract: | Magnetic resonance imaging (MRI) is a completely noninvasive method for visualizing cardiovascular anatomy but has had limited use for assessment of cardiac function. The authors evaluated the use of gated MRI for the quantification of regional myocardial contraction. Nine normal subjects underwent gated MRI of five transverse sections (7 mm thickness) through the left ventricle at five intervals in the cardiac cycle using a new technique called rotating gated sequence. All five sections were examined, and the section that best demonstrated the midportion of the left ventricle in its maximum dimension was used to obtain measurement. This technique permitted assessment of regional wall thickening of various regions of the left ventricle in different phases of the cardiac cycle. The extent and percentage of wall thickening were calculated from measurements of the septum and anterior and lateral left ventricular wall in end-diastole and end-systole. The calculated mean values for extent and percentage of wall thickening for the septum were 0.40 cm and 40%; for the anterior wall, 0.61 cm and 73%; and for the lateral wall, 0.53 cm and 57%, respectively. A limitation of the current technique in wall thickness measurements is that the transverse MR plane of section is not perpendicular to the long axis of the left ventricle. Consequently, such oblique sections through the left ventricle may give inaccurate absolute wall thickness measurements but can provide reliable estimate of regional wall thickening dynamics. The ability to define left ventricular wall thickness and function without contrast media provides a noninvasive technique for the detection of segmental left ventricular myocardial dysfunction in ischemic heart disease. |
