TY - JOUR
T1 - In vivo validation of the bold mechanism
T2 - A review of signal changes in gradient echo functional MRI in the presence of flow
AU - Haacke, E. Mark
AU - Lai, Song
AU - Yablonskiy, Dmitriy A.
AU - Lin, Weili
PY - 1995
Y1 - 1995
N2 - Brain functional magnetic resonance imaging (FMRI) is possible because of local changes in blood flow and oxygenation levels. Understanding the role of each mechanism is important for interpreting FMRI results as well as for the design of the experiment itself. In this review, we address the role of flow and blood oxygen level dependence (BOLD) and how they can be used in conjunction with each other to enhance the BOLD effect. We also discuss the role of intra/extravascular signal changes in the presence of a vessel for the imaging situation and show how the ratio of these two contributions is likely to change as the blood volume fraction changes. Using the BOLD model itself, along with 3‐D phase imaging, we show that blood oxygenation level in veins in vivo is Y = 0.544 ± 0.029 as measured in 14 vessels in five subjects. Finally, we comment on the use of phase images themselves as a means to discriminate tissues with different levels of blood such as gray matter, white matter, and cerebrospinal fluid.
AB - Brain functional magnetic resonance imaging (FMRI) is possible because of local changes in blood flow and oxygenation levels. Understanding the role of each mechanism is important for interpreting FMRI results as well as for the design of the experiment itself. In this review, we address the role of flow and blood oxygen level dependence (BOLD) and how they can be used in conjunction with each other to enhance the BOLD effect. We also discuss the role of intra/extravascular signal changes in the presence of a vessel for the imaging situation and show how the ratio of these two contributions is likely to change as the blood volume fraction changes. Using the BOLD model itself, along with 3‐D phase imaging, we show that blood oxygenation level in veins in vivo is Y = 0.544 ± 0.029 as measured in 14 vessels in five subjects. Finally, we comment on the use of phase images themselves as a means to discriminate tissues with different levels of blood such as gray matter, white matter, and cerebrospinal fluid.
UR - http://www.scopus.com/inward/record.url?scp=0029313692&partnerID=8YFLogxK
U2 - 10.1002/ima.1850060204
DO - 10.1002/ima.1850060204
M3 - Article
AN - SCOPUS:0029313692
SN - 0899-9457
VL - 6
SP - 153
EP - 163
JO - International Journal of Imaging Systems and Technology
JF - International Journal of Imaging Systems and Technology
IS - 2-3
ER -