Whole-body MR angiography using two-dimensional parallel imaging (iPAT2) at 3T

Aims: MR protocols for whole-body MR angiography are limited with respect to spatial resolution and anatomic coverage secondary to maximum achievable SNR and length of data acquisition. Aim of the study was the optimization of whole-body 3D contrast enhanced MR angiography with parallel imaging in phase- and slice-encoding directions for all imaging stations in order to acquire high spatially resolved datasets in combination with single contrast injection.

Materials and Methods: After injection of 0.18 mmol gadobutrol/kg body weight (Gadovist, Bayer Healthcare) high spatial resolution 3D MRA datasets were acquired throughout the whole-body employing iPAT² in all stations (GRAPPAx6) using a 3.0T MR scanner (Magnetom Trio, Siemens) in 23 patients. SNR and CNR values were calculated for each imaging region taking into account the variable noise distribution of parallel imaging techniques. The data sets were evaluated by two independent observers for image quality and venous overlay on a four-point scale [range 1–4].

Results: Scoring of image quality in 1079 vessel segments by observer 1 (observer 2) yielded 3.13±1.15 (3.17±1.14), respectively. High interobserver agreement (k=0.81) was found. Venous enhancement was evident in 4/23 patients in the abdominal region and in 3/23 patients in the lower leg region, respectively. Signal measurements revealed mean SNR values of 52.7±10.7/36.2±8.0/56.2±17.7/47.0±8.9 and CNR values of 42.7±11.0/29.0±7.4/48.2±15.7/38.8±8.6 for the angiographic stations I-IV, respectively.

Conclusion: The presented data suggests that contrast-enhanced MRA with parallel imaging in phase- and slice-encode direction (iPAT²) is feasible for whole-body applications and allows the acquisition of large 3D datasets with adequate spatial resolution within short measurement times facilitating a single contrast injection.