Abstract： Objeetive To analyze the attenuation differences of left yentricular myocardium on 64-slice CT coronary artery angiography in adults.Methods of 1130 consecutive patients,119 patients (65 males,54 females,ranged from 27 to 83 years with mean age of 52 years)with no stenosis or stenosis less than 25% in the left anterior descending arteries were enrolled.The standard axial image with 3mm slice thickness just below the aorta valve was selected for measttrement.The regions of interest(0.1 cm× 0.1 cm)in posterior interventricular septum(septal P),anterior interventricular septum(septal A),apex,anterior free wall and posterior free wall of the left ventricle were selected within the myocardium and the mean CT value wag measured.A paired Student t test was used for the comparison of CT values in different areas,P value under 0.05 was considered statistically significant.Results The megn attenuafion of the apical region(69.9±15.5)HU was lower than that of septal A(91.9±15.1)HU(t=11.060,P＜0.01)and anterior free wall(79.7±16.9)HU(t=4.639,P＜0.01),the mean attenuation in septal(93.8±14.8)HU and posterior free wall(88.0±14.3)HU showed relatively higher values.The myocardial intensity attenuation presented as a U-shape in the left ventricular myoeardium. Conclusions The mean attenuation in the left ventrieular myoeardium demonstrates as U-shape during the coronary artery angiography examination in normal adults.This can be helpful for iudging the extent of myocardial infarctiotr.