Noninvasive blood flow measurement and quantification of shunt volume by cine magnetic resonance in congenital heart disease. Preliminary results

Abstract

Based on the phase difference method as described by Nayler et al. we developed a gradient-echo sequence, which refocuses flow related phase shifts even for infants with their higher peak velocity, higher acceleration and faster heart rates. A repetition time (TR) of 15 ms provides a high temporal resolution for dynamic studies. Modification of the flow-rephasing gradient-echo sequence in slice select direction leads to a defined phase shift and the resultant phase difference images allow blood flow measurements in the great arteries and the calculation of blood volume per heart cycle (flow volume) to assess left and right ventricular stroke volume. This can also be achieved by calculation of the ventricular volume from contiguous slices of the whole heart, but, this in excessive measuring times. Both methods were applied in 6 examinations of children with congenital heart diseases (1 pulmonary sling, 1 coarctation of the aorta, 1 ventricular septal defect, 3 atrial septal defects). The age of the patients ranged from 3 months to 13.4 years (mean age 4.9 years). The regression analyses of both methods show a high correlation for systemic flow (y = -0.98 + 1.08 x, r = 0.99, SEE = 2.59 ml) and for pulmonary flow (y = -1.40 + 0.96 x, r = 0.99, SEE = 4.70 ml). The comparison of flow calculated Qp:Qs ratio and chamber size calculated Qp:Qs ratio with data obtained by heart catheterization show also a regression line close to the line of identity (y = -0.01 + 1.04 x, r = 0.98, SEE = 0.15 and y = 0.28 + 0.96 x, r = 0.81, SEE = 0.47, respectively).