Evaluation Of Myocardial Infarction By 64-MDCT Comparison With Contrast-Enhanced MRI

Part I and IIObjective To assess the left ventricular myocardium attenuation difference in healthy individuals during the early wash-in in 64-MDCT coronary artery angiography, and measure the CT value in chronic myocardial infarction, evaluate the myocardial hypo-attenuation in detection of myocardial infarction. Materials and Methods ①Among 450 consecutive patients, 51 patients who underwent 64-MDCT coronary artery angiography and their left anterior descending artery presented as normal or less than 25% stenosis were enrolled in this study retrospectively. They aged from 28 to 70yrs, averaged 49.9yrs (38 men 13 women). The 3mm thickness axial image of whole heart below the aorta valve was selected for measuring. Five regions of interest (dimension about 0.1cm~2) were drawn within the myocardium, i.e. post interventricular septum ( septal P) and anterior interventricular septum ( septal A), cardiac apex, anterior free wall and posterior free wall. The mean attenuation was measured and compared. ② Another 31 cases (23 men, 8 women) who suffered from documented myocardial infarction were included, and the infarction areas were measured on the MDCT images. ③ Additionally, 23 cases who performed 64-MDCT and contrast-enhanced MRI, the hypo-ttenuation on MDCT was compared with DE-MRI, to measure and compare the volume of MI.Results ① The mean attenuation in apical region (69.7HU) is lower than that of septal A (85.8HU) and anterior free wall (73.6HU), the mean attenuation in septal P (89.8HU) and posterior free wall (86.2HU) show relatively higher. The myocardial attenuation tends to present as a U-shape in the left ventricular myocardium. ② The density of chronic MI is about 15.33Hu, 95% confidence interval is 8.3～30.8Hu. ③ The MI volume measured by CE-MRI and 64-MDCTwere 15.26±9.00mL and 7.68±5.53mL,respectiveIy. Although the volume of hypoenhanced area were correlated with that of hyperenhanced on CE-MRI,but the size can be underestimated by MDCT. ④ Diagnosis of the MI by the hypoenhancement on MDCT shows sensitivity of 100%, specificity of 66.7%. Positive prognostic value is 82.3%, whereas negative prognostic value is 100%. Conclusions ①The mean attenuation in left ventricular myocardium demonstrates as U-shape during the coronary artery angiography. ②) The area of chronic MI shows hypoenhancement compared with normal area. ③The size of MI area tends to be underestimated on MDCT compare with DE-MRI. ④ The diagnosis of MI depended on hypoenhancement shows excellent sensitivity but moderate specificity.Part threeObjective To determine if phase-sensitive inversion-recovery(IR) magnetic resonance( MR) imaging can obviate the need to the precise inversion time (TI) to null the signal of normal myocardium to achieve high contrast between infarcted and normal myocardium.Materials and Methods: Twenty three patients with suspected and documented myocardial infarction were enrolled in this study, 16 patients accomplished the examination successfully, 12 men, and 4 women, aged from 37～77 yrs (averaged 56.3 yrs). Informed consent was obtained from each patient. They underwent scanning in a 1.5-T MR system 5～30min after administration of gadobenate dimeglumine of 0.1mmol per kilogram of body weight. Each patient performed routine IR FGRE sequence which produced magnitude reconstructed images and then PSIR sequence produced phase-sensitive IR images.Results: Among 16 cases, 5 hyperenhancement due to MI were detected, 2 cases transmural infarction, 3 cases of subendocardial infarction. No hyperenhancement was detected by both sequences in another 10 cases. In routine DE-MRI, 2～9 breath-holdings were needed to optimize TI time to null the normal myocardium, whereas a nominal TI 280ms was selected to perform the whole heart scanning to PSIR sequence. Mean CNR of normal myocardial 8.24 and 7.02 in routine and PSIR sequence. Mean CNR of hyperenhanced area with blood pool in left ventricle were 4.36 and 6.29. PSIR demonstrated stable image signal intensity, while eliminated the need to find optimal TI.Conclusions: PSIR can be performed with a nominal time 280ms to finish the delayed enhancement study, obviated the need to find an optimal TI, thus it is a promising MRI technology.