| Objectives:1. To verify the effection of velocity encoding value and encoding direction in phase-contrast imaging sequence on 3.0 Tesla MR system (3.0 T PC-MRI), and to assess the accuracy and the stability for the quantitative measurement of the constant flow and variable velocity flow by using a self-made flow phantom.2. To explore the feasibility of multi-phase acquisition sequence during cardiac cycle (cine MRI) without breath-hold to evaluate the cardiac function for patients with incompatible breath-hold, and to investigate the values of left ventricular function by using this sequence.3. To measure the hemodynamic information of great vessels of pulmonary circulation and systemic circulation by using phase-contrast imaging sequence on 3.0 Tesla MR system (3.0 T PC-MRI), and to validate the accuracy of the results from PC-MRI sequence in vivo simultaneously.4. To investigate the significance of the information of the intracardiac malformations, major ventricular and atrioventricular valve function for patients with complex congenital heart disease (CCHD) underwent bidirectional Glenn shunt (BGS) from spin-echo sequence combining with cine MR imaging sequence.5. To calculate the aortopulmonary collateral flow (APCF) and intracardiac shunt flow (ICSF) for patients with bidirectional Glenn shunt (BGS) according the data from PC sequence, and to investigate the relationship of the parameters of pulmonary vessel growth and the pulmonary flows obtained from contrast-enhanced MR imaging (CE-MRI) sequence and phase-contrast imaging sequence.Materials and Methods:1. First, holding flow velocity and velocity encoding value, the dynamic information of the fluid flow was tested under different encoding directions. Second, holding flow velocity and encoding directions, the velocities of constant flow were tested under different velocity encoding values. Third, holding velocity encoding value and encoding direction, flow velocity value measured by PC-MRI sequence under different constant flow was compared with its actual value. Fourth, the curve of the variable velocity flow measured with PC-MRI sequence was compared with the curve of its actual variable velocity. T test was employed to assess the statistical significance of the difference between the results measured with PC-MRI sequence and their actual value.2. The fast imaging employing steady state acquisition (FIESTA) sequence with and without breath-hold was performed to obtain the multiphase data in 15 healthy volunteers. The left ventricular function was analyzed from the images of these volunteers on the workstation with Report Card software. The results of the function parameters of left ventricle, including end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), mean myocardial mass (MM), cardiac output (CO) and the corresponding parameters of end-diastolic volume index (EDVI), myocardial mass index (MMI) and cardiac index (CI), without breath-hold were compared with those obtained with multi-breathhold sequence. Paired-samples t-test was employed to assess their difference, and pearson's correlation analysis was performed between the results without breath-hold sequence and with multi-breathhold sequence.3. PC-MRI sequences were performed on GE 3 tesla MR scanner in 15 healthy volunteers in order to evaluate the blood flow status in main pulmonary artery (MPA), right pulmonary artery (RPA), left pulmonary artery (LPA), ascending aorta (AA), superior vena cava (SVC) and inferior vena cava (IVC). The net flow volume and regurgitation fraction of each vessel were calculated for each volunteer during one cardiac cycle. Paired-samples t-test was employed to assess the statistical significant difference.4. Triple-IR sequence and cine MR sequence were performed in 22 patients with BGS. According to these MR images, intracardiac malformations, major ventricular and atrioventricular valve function were evaluated with Report Card software on workstation. End-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), fractional shortening (FS), mean myocardial mass (MM), cardiac output (CO) and the corresponding parameters of end-diastolic volume index (EDVI), myocardial mass index (MMI) and cardiac index (CI) of major ventricular were measured with cine MR imaging sequence. The correlation analysis of the results of EDV, ESV, EF and FS obtained from ultrasound cardiography (UCG) and MRI was performed. The results of EDVI, MMI, CI and EF of BGS in the patients and healthy volunteers were compared and independent-samples t-test was employed to evaluate the statistical significance of the results' difference. Spearman rank correlation coefficients were employed to analyze the difference of the regurgitation degree of atrioventricular valve obtained with cine MRI and UCG.5. PC-MRI sequence was performed to measure the flow of great vessels of right pulmonary artery (RPA), left pulmonary artery (LPA), ascending aorta (AA), superior vena cava (SVC) and inferior vena cava (IVC), and the quantity of AA (Qs) per minute (Qs), the quantity of pulmonary per minute (Qp), and the quantity of venous return per minute (Qv) were calculated by using Report Card software. APCF was calculated as the difference of Qs and Qp, and ICSF were calculated as the difference of Qv and Qp. CE-MR imaging sequence was performed to assess the pulmonary vessels growth. The relationship of parameters of pulmonary vessels growth and corresponding blood flow was evaluated with the correlation analysis. The statistical significant difference of pulmonary blood flow and APCF at the different antegrade flow groups was evaluated with independent samples t-test. The results of the width of superior cavo-pulmonary anastomosis measured with MRI and UCG were evaluated with paired-samples t-test and pearson's correlation analysis. The relationship of ICSF and EDVI obtained with MRI was evaluated with correlation and regression analysis, and so did the relationship of ICSF and the regurgitation area of atrioventricular valve obtained with UCG.Results:1. Only on the velocity encoding direction of SLICE or SI (superior and inferior) could the direction of proton flowing be correctly detected. There was no significant difference between the measured velocities with PC-MRI sequence under different flow rates and the corresponding actual flow velocities (t=-0.861, P=0.405) while the velocity encoding value was appropriately greater than the actual flow velocity. A significantly positive correlation (r=0.999, P＜0.001) was demonstrated between the measured velocities and the actual velocities. There was good consistency among the measured maximum, minimum, average velocities and the corresponding actual variable flow velocities.2. The EDV, ESV, EF, MM, EDVI, MMI, CO and CI measured with and without breath-hold multi-phase acquisition sequence were (121.97±17.53) ml and (123.85±19.48) ml, (45.57±9.18) ml and (46.64±8.34) ml, (62.39±4.67)% and (62.65±5.12)%, (106.25±18.07) g and (105.63±19.20) g, (69.58±6.53) ml/m2 and (70.44±7.11) ml/m2, (60.17±6.34) g/m2 and (60.83±5.45) g/m2, (5.69±0.88) L/min and (5.70±0.78) L/min, (3.27±0.30) L/min/m2 and (3.26±0.24) L/min/m2, respectively. No statistical difference was found between the results of the two methods (all P>0.05), but good correlationship between the results of the two methods was demonstrated (r=0.633-0.957, all P< 0.01).3. The flow volume of MPA, RPA and LPA during a cardiac cycle was (69.42±12.35) ml, (38.78±6.81) ml and (32.27±6.49) ml, respectively. The flow volume of RPA was significantly higher than that of LPA (t=3.092, P= 0.004). The percentage of flow volume of RPA and LPA was 55.4% and 44.6%, respectively. The regurgitation fraction of LPA was significantly higher than that of RPA (t=5.502, P=0.001). The average flow volume of AA in one cardiac cycle was (70.1±12.42) ml. The average flow volume of SVC (25.5±4.14 ml) was significantly lower than that of IVC (42.14±9.26 ml) (t=-6.866, P＜0.001). The regurgitation fraction of IVC (9.77±1.83%) was significantly higher than that of SVC (6.86±1.92%) (t=4.250, P<0.001). The ratio of flow volumes of AA, MPA and vena cava were 1:1.009:0.974.4. All intracardiac malformations and cardiovascular conjunction were demonstrated clearly on the images of triple-IR sequence with cine MR sequence. No statistical difference was found between the results of EDV, ESV, EF, FS obtained with cine MR imaging sequence and those with UCG (all P>0.05). A good correlation (r=0.727-0.99, all P< 0.01) was found between the two methods. The value of EDVI, MMI and CI of the patients with BGS was significantly higher than that of healthy volunteers, but the value of EF was lower. The positive correlation of the regurgitation degree of atrioventricular valve between two results obtained with MRI and UCG was found significantly (rs=0.712, P＜0.001).5. The difference of the flow volume of systemic circulation and pulmonary circulation was found significantly. We found that Qs was higher than Qv, and Qv was higher than Qp. The flow volume of RPA (56.1±10.9%) was significantly higher than that of LPA (43.9±10.9%). The flow volume of APCF ranged from 0.21-1.53 L/min (mean 0.89 L/min), and the flow volume of antegrade venous blood flow group was significantly higher than that of antegrade arterial blood flow group. The positive relationship of the flow volume and the growth parameters of pulmonary arteries was found (r=0.456-0.698). The results of width, peak flow velocity and gradient pressure of superior cavopulmonary anastomosis obtained by MRI were closely correlated with those of UCG (r=0.427-0.858, all P< 0.05). The positive relationship between ICSF and EDVI obtained by cine MR imaging sequence, and the positive relationship between ICSF and the regurgitation area of atrioventricular valve obtained by UCG were found (r=0.685, and r=0.806).Conclusions:1. PC-MRI sequence on 3.0 T MR system can evaluate the parameters of the flow of the flow phantom accurately when the velocity encoding value and the encoding direction are selected correctly.2. Left ventricular function in healthy people and the patients with incompatibile breath-hold can be evaluated with multi-phase acquisition without breath-hold sequence correctly.3. The flow volume of great vessels of pulmonary circulation and systemic circulation can be accurately measured with PC-MRI sequence. The flow volume and regurgitation fraction of great vessels in healthy volunteers may be used as a reference.4. The cardiac malformation and function of the BGS patients could be accurately evaluated with cine MR imaging sequence and spin-echo sequence. A good correlationship was demonstrated in evaluating the degree of regurgitation of atrioventricular valve between cine MR imaging sequence and UCG.5. The SPCF and ICSF in patients with BDG can be reliably measured with PC-MRI sequence on 3.0 tesla MR system. The good correlation of the flow volume obtained by PC-MRI sequence and the growth parameters obtained by CE-MRI for pulmonary vessels are demonstrated, and so does the ICSF with EDVI and with the regurgitation area of atrioventricular valve obtained by UCG.
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