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Intravascular BOLD signal characterization of balanced SSFP experiments in human blood at high to ultrahigh fields
{Purpose: To investigate the intravascular contribution to the overall balanced SSFP (bSSFP) BOLD effect in human blood at high to ultrahigh field strengths (3 T, 9.4 T, and 14.1 T). Methods: Venous blood prepared at two different oxygenation levels (deoxygenated: Y $\approx$ 71\textpercent, oxygenated: Y $\approx$ 94\textpercent) was measured with phase-cycled bSSFP for varying TRs/flip angles at 3 T, 9.4 T, and 14.1 T. The oxygen sensitivity was analyzed by intrinsic MIRACLE (motion-insensitive rapid configuration relaxometry)-R2 estimation and passband signal differences. The intravascular BOLD-related signal change was extracted from the measured data for microvasculature and macrovasculature, and compared with the extravascular contribution obtained by Monte Carlo simulations. Results: The MIRACLE-R2 values showed a characteristic increase with longer TRs in deoxygenated blood, corroborating that SE-R2 data cannot be used to assess the intravascular bSSFP BOLD effect. Passband bSSFP signal differences measured at optimal flip angles of 30\mbox{$^\circ$} at 3 T and 20\mbox{$^\circ$} at 9.4 T/14.1 T revealed considerable relative intravascular contributions of 95\textpercent/70\textpercent at 3 T, 74\textpercent/43\textpercent at 9.4 T, 66\textpercent/46\textpercent at 14.1 T for TR \textequals 5 ms, and 90\textpercent/65\textpercent at 3 T, 36\textpercent/27\textpercent at 9.4 T, 13\textpercent/15\textpercent at 14.1 T for TR \textequals 10 ms in macrovascular/microvascular regimes. Conclusion: The results indicate that intravascular effects have to be considered to better understand the origin of bSSFP BOLD contrast in functional MRI experiments, especially at short TRs. The MIRACLE-R2 method demonstrated the ability to quantify the apparent decrease in R2 due to rapid RF refocusing.}
@article{item_3261917, title = {{Intravascular BOLD signal characterization of balanced SSFP experiments in human blood at high to ultrahigh fields}}, journal = {{Magnetic Resonance in Medicine}}, abstract = {{Purpose: To investigate the intravascular contribution to the overall balanced SSFP (bSSFP) BOLD effect in human blood at high to ultrahigh field strengths (3 T, 9.4 T, and 14.1 T). Methods: Venous blood prepared at two different oxygenation levels (deoxygenated: Y $\approx$ 71\textpercent, oxygenated: Y $\approx$ 94\textpercent) was measured with phase-cycled bSSFP for varying TRs/flip angles at 3 T, 9.4 T, and 14.1 T. The oxygen sensitivity was analyzed by intrinsic MIRACLE (motion-insensitive rapid configuration relaxometry)-R2 estimation and passband signal differences. The intravascular BOLD-related signal change was extracted from the measured data for microvasculature and macrovasculature, and compared with the extravascular contribution obtained by Monte Carlo simulations. Results: The MIRACLE-R2 values showed a characteristic increase with longer TRs in deoxygenated blood, corroborating that SE-R2 data cannot be used to assess the intravascular bSSFP BOLD effect. Passband bSSFP signal differences measured at optimal flip angles of 30\mbox{$^\circ$} at 3 T and 20\mbox{$^\circ$} at 9.4 T/14.1 T revealed considerable relative intravascular contributions of 95\textpercent/70\textpercent at 3 T, 74\textpercent/43\textpercent at 9.4 T, 66\textpercent/46\textpercent at 14.1 T for TR \textequals 5 ms, and 90\textpercent/65\textpercent at 3 T, 36\textpercent/27\textpercent at 9.4 T, 13\textpercent/15\textpercent at 14.1 T for TR \textequals 10 ms in macrovascular/microvascular regimes. Conclusion: The results indicate that intravascular effects have to be considered to better understand the origin of bSSFP BOLD contrast in functional MRI experiments, especially at short TRs. The MIRACLE-R2 method demonstrated the ability to quantify the apparent decrease in R2 due to rapid RF refocusing.}}, volume = {85}, number = {4}, pages = {2055--2068}, publisher = {Wiley-Liss}, address = {New York}, year = {2021}, slug = {item_3261917}, author = {P\'erez-Rodas, M and Pohmann, R and Scheffler, K and Heule, R} }