Optimized 4D Time-of-Flight MR Angiography Using Saturation Pulse

Purpose: To assess arterial visibility on 4D time-of-flight (4D-TOF) by temporal magnetization transfer contrast pulse (t-MTC) and temporal tilted optimized nonsaturating excitation (t-TONE). 3D-TOF magnetic resonance angiography (MRA) is used for the noninvasive assessment of the intracranial arteries. However, it does not provide temporal information for diagnosing hemodynamics. To noninvasively obtain more detailed hemodynamics-related information, we developed a novel time-resolved MRA without the arterial spin labeling technique, termed 4D-TOF MRA using saturation pulse. Materials and Methods: On a 3.0T MRI, three techniques were compared to optimize the visibility of the arteries above the circle of Willis; 1) simple 4D-TOF, 2) 4D-TOF with t-MTC, and 3) 4D-TOF with t-MTC and t-TONE. Eight healthy volunteers were scanned with these three sequences. The contrast changes between the background tissue and the arteries in temporal phases were assessed and compared quantitatively and qualitatively. Results: The contrast between the background and the arteries for 4D-TOF with t-MTC and t-TONE was significantly higher than those for the other methods in delayed phases (P < 0.001). The qualitative assessment showed that 4D-TOF with t-MTC and with t-MTC and t-TONE provided better visualization of the intracranial artery than simple 4D-TOF (P < 0.001). Conclusion: 4D-TOF with t-TONE and t-MTC enabled observation of the intracranial hemodynamics. Optimized 4D-TOF provides high-quality images without image subtraction, and good visibility of the intracranial arteries even in the prolonged observation time.