Objective:To evaluate the feasibility of making individualized scanning and contrast injection protocol based on body mass index (BMI) and body weight during dynamic myocardial computed perfusion (CTP) imaging in order to get high-quality images while drastically reducing radiation dose.Methods:A total of 128 patients with coronary heart disease diagnosed by coronary CTA (CCTA) performed CTP from June, 2019 to March, 2020 were prospectively enrolled. Patients were divided into six groups: group 1, BMI<24 kg/m 2, ≤60 kg, 70 kV; group 2,BMI<24 kg/m 2, 61≤kg≤70, 70 kV; group 3, BMI 24-28 kg/m 2, 61≤kg≤70, 80 kV; group 4, BMI 24-28 kg/m 2, 71≤kg≤80, 80 kV; group 5, BMI 24-28 kg/m 2,>80 kg, 80 kV;group 6, BMI>28 kg/m 2,>80 kg, 100 kV. 200 mA was fixed for all patients. Contrast agent with iodine containing 370 mg/ml was used in all patients. The iodine delivery rates (IDR) for each group was 0.8, 1.0, 1.2, 1.4, 1.6, 2.0 g/s, respectively. The attenuation and noise of left ventricle (LV) and septal myocardial were measured to calculate signal to noise ratio (SNR) and contrast to noise ratio (CNR) of the images in each group. The Shapiro-Wilk test was conducted to assess the normality of quantitative data. Quantitative variables were compared using one-way ANOVA if normally distributed. Results:The LV attenuation of the six groups were (506±85), (513±77), (510±81), (456±74), (477±111), (462±43) HU, respectively. There was no significant difference among them ( F=2.249, P=0.054). SNR values of LV were 23±8, 20±5, 21±5, 19±4, 19±7, 19±4, and CNR values were 19±7, 17±4, 17±4, 16±4, 15±6, 15±4, respectively. There were no significant differences among them ( F=1.674, 1.736, all P>0.05). Under a single CTP scan, the radiation dose of 70, 80 and 100 kV groups were 1.6, 2.3 and 4.3 mSv, respectively. The does of the 70 kV group and 80 kV group were significantly lower than that of the 100 kV group, and the dose of the 70 kV group was also significantly lower than that of the 80 kV group (all P<0.001). Conclusions:The application of individualized scanning and contrast agent injection protocol based on IDR is feasible in myocardial CTP with successful image quality, and the radiation dose decreases significantly.

Objective:To investigate the impact on image quality of a new deep learning image reconstruction (DLIR) algorithm in dynamic CT myocardial perfusion imaging (CTP) and to explore whether the algorithm affects the quantification of myocardial blood flow (MBF) in swine.Methods:Dynamic CTP imaging was performed in five anesthetized domestic swine [body weight (58.6±1.9) kg], at both rest and stress state. The tube voltages were fixed at 100 kV, and the low-dose and high-dose scanning tube currents were set as 150 mA and 300 mA, respectively. The low-dose (LD) scan data were reconstructed with filtered back projection (FBP) and three different DLIR strengths (low, medium, and high). High-dose (HD) scan data were reconstructed with filtered back projection (FBP) only. Subjective (5-point scale) image quality was evaluated, and objective evaluations included image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) was performed. Linear regression was used to test the linear trend between DLIR algorithm strength and image quality. Data sets normality was determined by the Shapiro-Wilk test. Comparisons between groups were performed using Student′s t test for normally distributed data or the Wilcoxon rank-sum test for non-normally distributed data. Results:The mean effective radiation dose was 7.2 and 3.8 mSv for the HD protocol and the LD protocol, respectively, with statistically significant difference found between two protocols ( t=282.50, P<0.001). The image noise of the images obtained at LD protocol gradually decreased and the image SNR and CNR gradually increased with DLIR algorithm strength increased ( F=60.10,35.87,41.41; P for trend were all<0.001). As for DLIR-high strength (LD) and FBP (HD) images, the image noise values were (31.7±3.1) and (38.2±1.2) HU; SNR were 16.6±2.0 and 13.8±0.8; CNR were 14.5±1.7, 11.6±0.9, respectively, with significant differences found between two groups ( t=5.70, 4.15, 5.68; all P<0.05). The subjective scores of DLIR-high strength (LD) and FBP (HD) images were significantly different (4.8±0.4 and 4.2±0.6, Z=2.12, P<0.05). No significant differences were found between the MBF calculated from FBP (LD) and from DLIR-high strength (LD), with the values as (81.3±17.3) ml·100 ml -1·min -1 vs. (79.9±18.3)ml·100 ml -1·min -1 at rest state; and (99.4±24.9)ml·100 ml -1·min -1 vs. (100.7±27.3) ml·100 ml -1·min -1 at stress state ( t=1.10, 0.89; P>0.05). Conclusion:DLIR-high strength can improve image quality of myocardial CTP in swine, and can reduce radiation dose without influencing the MBF calculation.