Magnetic resonance angiography of renal arteries using contrast behavior between water and fat during the transient phase of steady state of signal on balanced turbo field echo sequence

The conventional renal magnetic resonance (MR) angiography using balanced turbo field echo (b-TFE) sequence with water-selective-excitation (WATS) had insufficient spatial resolution of z direction in maximum intensity projection (MIP) image. In this study, we developed an isotropic protocol that used their contrast behavior between water and fat during the transient phase of b-TFE sequence instead of WATS. Then the performance of isotropic protocol was compared with conventional protocol. We investigated contrast to noise ratio (CNR) between distilled water and baby oil to obtain optimal flip angle. The number of startup echoes was investigated to reduce ghost artifact. Furthermore, the median of Full Width at Half Maximums (FWHMs) of profile curves for inside diameter was determined in each size of 2, 3 and 5 mm of plastic tube phantoms. As a result, we constructed an isotropic protocol (voxel size; 0.78x0.78x0.78mm³) with 70 degree flip angle and with startup echoes of 4. Differences between medians of FWHMs and inside diameters of three tube phantoms in x and z directions for isotropic voxel showed almost equal. In conclusion, we have confirmed that the isotropic MR angiography of renal arteries using contrast behavior during the transient phase of b-TFE sequence is worth addressing, and it is clearly more useful than conventional protocol.