In vivo Measurement of Longitudinal Relaxation Time of Human Blood by Inversion-recovery Fast Gradient-echo MR Imaging at 3T

Abstract

Purpose: Accurate longitudinal relaxation time (T 1 ) of arterial blood is important in evaluating blood ‰ow in tissue by arterial spin labeling magnetic resonance (MR) imaging. Few studies have reported the T 1 of human arterial blood in vivo, especially using 3-tesla MR imaging. T 1 values of human venous blood in vivo have been reported, but they diŠer from those measured in vitro. We aimed to evaluate the accurate T 1 of human arterial blood in vivo.Methods: We measured T 1 values of blood in 10 healthy volunteers in vivo using an inversion-recovery fast gradient-echo sequence and 3-tesla MR imaging unit. We also measured hematocrit (Hct) values of venous blood samples. After nonselective application of the inversion pulse using a body coil, we obtained MR imaging signals of arterial blood in the abdominal aorta. Similarly, we measured the signals of venous blood in the internal jugular vein. Inversion times varied between 200 and 5000 ms for imaging of the abdominal aorta and 200 and 2500 ms for imaging of the jugular vein. We also acquired signals without the inversion pulse. We estimated T 1 values from the data by nonlinear least squaresˆtting of a 3-parameter model.Results: The T 1 value (mean±standard deviation) of arterial blood was 1779±80 ms and of venous blood, 1694±77 ms. The average Hct value was 0.47. The R 1 (＝1/T 1 ) of arterial blood was related to the Hct value as: R 1 ＝(0.59±0.16)Hct＋(0.29±0.07) (mean± standard error) s -1 . For the venous blood, R 1 ＝(0.70±0.11)Hct＋(0.27±0.05) s -1 .Conclusion: We observed a T 1 of human arterial blood in vivo of 1779±80 ms at a mean hematocrit value of 0.47 as determined by 3T MR imaging; an even longer T 1 value is expected with a hematocrit value less than 0.47.

Fast measurement of blood T1 in the human carotid artery at 3T: Accuracy, precision, and reproducibility

“…a). As demonstrated in previous studies on both arterial and venous blood, the blood relaxation rate 1/T 1 has a linear dependence on Hct. Earlier work has asserted hemoglobin as the main source of the T 1 relaxation in arterial blood.…”

MR fingerprinting for rapid quantification of myocardial T1 , T2 , and proton spin density

“…Nevertheless, in the LV blood pool, the mean T 1 measured with MRF over all volunteers was 1807ms (min 1701ms, max 1931ms) and the mean T 2 was 91ms (min 76ms, max 107ms). The blood T 1 measurements are in agreement with literature values of 1550-1932ms (40)(41)(42)(43); however, the blood T 2 measurements obtained with both MRF and T 2 -prepared bSSFP are lower than in previously reported studies, which found T 2 values in oxygenated blood of 175ms (44) to 275ms (40).…”

T1 Relaxivities of Gadolinium-Based Magnetic Resonance Contrast Agents in Human Whole Blood at 1.5, 3, and 7 T

“…T1 values of blood may be influenced by Hct, temperature, pH, and oxygenation levels. 9,[15][16][17][18][19] In fact, accurate measurements of human blood T1 values are an important topic in itself because these values are an important MR parameter for quantitative physiological and functional MR measurements, such as arterial spin labeling with cerebral blood volume calculations. Previously, T1 values of bovine blood had been measured at 1.5 T, 3 T, 18 4.7 T, 7 T, and 9.4 T. 17 T1 values of rat blood have also been measured at 11.7 T. 16 Human blood T1 values have also recently been measured at 3 T 19 and 7 T.…”

“…However, conflicting conclusions regarding the influence of blood oxygen content have been reached in previous studies. [15][16][17][18][19] In the study of Lin et al, 16 rat blood T1 values were found to be independent of oxygenation. The study of Rane et al 15 demonstrated that T1 values of human blood at 7 T differed depending on whether arterial or venous blood was examined.…”