Altered saturation pulse with a high flip angle for venous saturation on 7 T time-of-flight magnetic resonance angiography

This study aimed to apply minimum-time variable-rate selective excitation (MinVER) to a presaturation pulse (PSP) with a high flip angle on 7 T time-of-flight magnetic resonance angiography (7T TOF-MRA), to attain a superior vessel-to-tissue contrast (VTCR), short acquisition time, and minor off-resonance effect. An altered PSP modified by using the 90 degrees flip angle (FA)-MinVER was implemented in the 7 T TOF-MRA, and its performance was evaluated with a signal profile and vessel-tissue contrast ratios and compared to the conventional PSP and 45 FA-TOF. The 90 FA-MinVER showed a similar signal profile to that of the conventional PSP and improved the vessel-tissue contrast ratios (0.313 +/- 0.80) compared to all conventional types (45 FA-TOF: 0.088 +/- 0.84, 90 FA-TOF: 0.203 +/- 0.72). Moreover, this noteworthy approach achieved substantially reduced total acquisition time (5 min and 55 s) with a short repeat-to-time (28 ms), indicating that at the 7 T TOF-MRA, the 90 FA-MinVER could be applied by default to suppress the venous signals regardless of individual human status and the specific absorption ratio constraint and with rapid imaging. Ultimately, its application could also help to observe subtle microvascular changes in the early stages and serve as key biomarkers in various vascular diseases.

Automated summary

This study applied MinVER technique to improve vessel-to-tissue contrast and shorten acquisition time on 7T TOF-MRA, achieving faster imaging speed and better contrast enhancement. The approach, unaffected by individual status and specific absorption ratio constraints, can serve as a valuable tool in observing microvascular changes and diagnosing various vascular diseases.