期刊
MAGNETIC RESONANCE IN MEDICINE
卷 49, 期 1, 页码 47-60出版社
JOHN WILEY & SONS INC
DOI: 10.1002/mrm.10355
关键词
BOLD contrast; transverse relaxation; fMRI; blood; intravascular
资金
- NCRR NIH HHS [RR15241] Funding Source: Medline
- NIBIB NIH HHS [P41 EB015909] Funding Source: Medline
- NINDS NIH HHS [NS37664] Funding Source: Medline
- PHS HHS [31490] Funding Source: Medline
- NATIONAL CENTER FOR RESEARCH RESOURCES [P41RR015241] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF BIOMEDICAL IMAGING AND BIOENGINEERING [P41EB015909] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE [R01NS037664] Funding Source: NIH RePORTER
Gradient-echo (GRE) blood oxygen level-dependent (BOLD) effects have both intra- and extravascular contributions. To better understand the intravascular contribution in quantitative terms, the spin-echo (SE) and GIRE transverse relaxation rates, R-2 and R-2(*), of isolated blood were measured as a function of oxygenation in a perfusion system. Over the normal oxygenation saturation range of blood between veins, capillaries, and arteries, the difference between these rates, R-2(') = R-2(*) - R-2, ranged from 1.5 to 2.1 Hz at 1.5 T and from 26 to 36 Hz at 4.7 T. The blood data were used to calculate the expected intravascular BOLD effects for physiological oxygenation changes that are typical during visual activation. This modeling showed that intravascular DeltaR(2)(*) is caused mainly by R-2 relaxation changes, namely 85% and 78% at 1.5T and 4.7T, respectively. The simulations also show that at longer TEs (>70 ms), the intravascular contribution to the percentual BOLD change is smaller at high field than at low field, especially for GRE experiments. At shorter TE values, the opposite is the case. For pure parenchyma, the intravascular BOLD signal changes originate predominantly from venules for all TEs at low field and for short TEs at high field. At longer TEs at high field, the capillary contribution dominates. The possible influence of partial volume contributions with large vessels was also simulated, showing large (two- to threefold) increases in the total intravascular BOLD effect for both GRE and SE.
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