VICTR: Venous transit time imaging by changes in T₁ relaxation

Purpose: Abnormalities in cerebral veins are a common finding in many neurological diseases, yet there is a scarcity of MRI techniques to assess venous hemodynamic function. The present study aims to develop a noncontrast technique to measure a novel blood flow circulatory measure, venous transit time (VTT), which denotes the time it takes for water to travel from capillary to major veins. Methods: The proposed sequence, venous transit time imaging by changes in T-1 relaxation (VICTR), is based on the notion that as water molecules transition from the tissue into the veins, they undergo a change in T-1 relaxation time. The validity of the measured VTT was tested by studying the VTT along the anatomically known flow trajectory of venous vessels as well as using a physiological vasoconstrictive challenge of caffeine ingestion. Finally, we compared the VTT measured with VICTR MRI to a bolus-tracking method using gadolinium-based contrast agent. Results: VTT was measured to be 3116.3 +/- 326.0 ms in the posterior superior sagittal sinus (SSS), which was significantly longer than 2865.0 +/- 390.8 ms at the anterior superior sagittal sinus (p = 0.004). The test-retest assessment showed an interclass correlation coefficient of 0.964. VTT was significantly increased by 513.8 +/- 239.3 ms after caffeine ingestion (p < 0.001). VTT measured with VICTR MRI revealed a strong correlation (R = 0.84, p = 0.002) with that measured with the contrast-based approach. VTT was found inversely correlated to cerebral blood flow and venous oxygenation across individuals. Conclusion: A noncontrast MRI technique, VICTR MRI, was developed to measure the VTT of the brain.