A comparison of a T1 weighted 3D gradient-echo sequence with three different parallel imaging reduction factors, breath hold and free breathing, using a 32 channel coil at 1.5 T. A preliminary study.

Objective: To investigate whether increasing temporal resolution with higher parallel imaging (PI) reduction factors (RF) in both breath-hold and free breathing approaches, using a non-contrast T1-weighted 3D gradient echo (GRE) sequence and a 32-channel phased array coil, permits diagnostic image quality, with potential application in patients unable to cooperate with breath-hold requirements.

Methods: The 9 healthy subjects (5 females and 4 males; age range was 20-49, mean 36 yrs) were recruited. A 3D GRE MR imaging of the abdomen was performed on 1.5 T MR system using a 32-element phased-array torso coil with PI RFs of 2, 4 and 6, breath hold and free breathing. Two reviewers retrospectively qualitatively evaluated all sequences for image quality, extent of artifacts, including motion, truncation, aliasing, pixel graininess and signal heterogeneity. The results were compared using Wilcoxon signed rank and a Bonferroni adjustment was applied for multiple comparisons.

Results: Image quality and extent of artifacts were better with breath hold than with free breathing acquisitions. The rate of artifacts increased with higher RF. The best quality was acquired with breath hold sequence using RF=2. RF=4 had lower but diagnostic rates (P=.004). The severity of artifacts, mainly pixel graininess (P=.004), rendered sequences with RF=6 non-diagnostic. All sequences were non-diagnostic in free breathing acquisitions.

Conclusions: Breath hold sequences with RF=2 had excellent quality and RF=4 had good quality and may be potentially used in partially cooperative patients. None of the sequences was considered diagnostic in free breathing acquisitions.