Objective Compared the scan doses of the 64 multidetector CT (64-MDCT) in three different lumbar ac-quisition patterns, to determine the optimized one. Methods The water phantom was scanned by the 64-MDCT, and three groups were divided according to acquisition patterns: group A (128 ×0.625 mm), group B (48 ×0.625 mm), and group C (40×0.625 mm). For every group, the water phantom was scanned for 40 times. The volume of CT dose index (CTDIvol), the DLP and the effective dose were calculated and recorded. One-way ANOVA test was used to compare mean values. Results According to the values of CTDIvol, DLP, and effective dose, the three groups were ordered as follows, group A (128×0.625mm)>group B (48×0.625mm)>group C (40×0.625mm). In group C, the values of effective dose were reduced 17.45%and 10.32%, respectively, in comparison with that in group A and group B. Conclusion The 40×0.625 mm is the optimized pattern which had minimum radiation dose.

Objective:To investigate the diagnostic value of cardiac magnetic resonance (CMR) contrast medium perfusion and delayed contrast enhancement for early myocardial ischemia.Methods:Ninety-one patients with coronary artery stenosis diagnosed by coronary angiography (CAG) between March 2020 and March 2022 in Yiwu Central Hospital were included in this study. These patients underwent first-pass perfusion cardiac magnetic resonance imaging and delayed enhancement examination. Arrival time ( t0), accumulative signal intensity (ASI), relative peak enhancement rate (SI%), maximum intensity of signal enhancement (SIp), and maximum curve slope (α) were statistically analyzed in the CMR contrast agent normal-dose perfusion and low-dose perfusion segments. The diagnostic value of CMR contrast agent perfusion versus CAG for early myocardial ischemia was determined. The signal intensity was compared between enhanced and non-enhanced areas of CMR contrast agent perfusion. Results:There were significant differences in ASI, SI%, SIp, and Slope (α) between normal perfusion and low perfusion segments ( t = 9.62, 10.65, 8.67, 6.93, all P < 0.05). There was no significant difference in the detection rate of lesioned vessels in early myocardial ischemia between CMR contrast agent perfusion and CAG [50.42% (120/238) vs. 51.68% (123/238), χ2 = 1.32, P = 0.163). There was a significant difference in the detection rate of lesioned vessels in myocardial ischemia between CMR contrast agent perfusion and CAG ( χ2 = 15.31, P < 0.001, r = 0.71). The signal intensity value in the delayed enhancement segment was significantly higher than that in the non-delayed enhancement segment [(598.43 ± 40.19) vs. (298.64 ± 70.58), t =19.85, P = 0.001). Conclusion:CMR contrast agent perfusion can effectively evaluate the severity of early myocardial ischemia and locate the diseased blood vessels. Delayed enhancement can determine the location and area of early myocardial ischemia, and can objectively reflect the severity of myocardial ischemia.