TRADITIONAL POSTER - ismrm

Poster Sessions
hematocrits, a general two-site exchange model (including slow, fast and intermediate regimes) can appropriately describe blood relaxation in oxygenated
blood and provides an erythrocyte lifetime of 12.2±3.7ms, in agreement with literature values
1131. Blood Longitudinal (T1) and Transverse (T2) Relaxation Times at 11.7 Tesla
Ai-Ling Lin 1 , Xia Zhao 1 , Peter T. Fox 1 , Timothy Q. Duong 1
1 Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, United States
Knowledge of blood T1 and T2 values are important for many MRI studies that include BOLD modeling, high spatial specificity BOLD fMRI, blood flow
MRI using arterial spin labeling (ASL), and blood volume MRI using vascular space occupancy (VASO) techniques. The purpose of the present study was
to determine blood T1 and T2 values at 11.7T as a function of oxygenation level (Y), temperature, hematocrit fraction (Hct) and field strength (B0).
1132. Maximal Accuracy and Precision of HRF Measurements in Rapid-Presentation ER-FMRI
Experimental Designs
Xiaopeng Zong 1 , Jie Huang 1,2
1 Department of Radiology, Michigan State University, East Lansing, MI, United States; 2 Neuroscience Program, Michigan State
University, East Lansing, MI, United States
A quantitative ER-fMRI study requires to measuring hemodynamic response function (HRF) both accurately and precisely. A periodic ER-fMRI design can
produce a high accuracy of HRF measurement but a low precision. Utilizing the approximate linearity of the HRF, a rapid-presentation (RP) ER-fMRI
design can improve the precision by shorting intersitimulus interval (ISI). Nevertheless, hemodynamic response is non-linear and its corresponding effect on
the estimated HRF increases with decreasing ISI, rendering the estimated HRF inaccurate for small ISI values. Accordingly, as demonstrated in this
preliminary study, an optimal RP ER-fMRI design should maximize both accuracy and precision of HRF measurements.
fMRI: Respiratory Calibrations
Hall B Wednesday 13:30-15:30
1133. Saturation of Visually Evoked BOLD Response During Carbogen Inhalation
Claudine J. Gauthier 1,2 , Cécile Madjar 2 , Richard D. Hoge 1,2
1 Physiology/Biomedical Engineering, Université de Montréal, Montréal, Quebec, Canada; 2 CRIUGM, Montreal, Quebec, Canada
Oxidative metabolism can be estimated from the BOLD signal following a calibration manipulation to determine a factor M. M is the maximum possible
BOLD signal change. Carbogen inhalation was used here with intense visual stimulation to test whether an asymptote in BOLD signal could be reached.
Results show a convergence of percent BOLD changes around 9% in visual cortex for 10% carbogen alone, and 5-10% carbogen breathing plus visual
stimulation. The diminishing incremental response from visual stimulation at high carbogen concentrations suggests that these manipulations approach
BOLD levels close to the saturation plateau.
1134. Calibrated FMRI During a Cognitive Stroop Task in the Aging Brain
Rafat Saeed Mohtasib 1,2 , Vanessa Sluming 1,2 , Laura Parkes 1,3
1 Magnetic Resonance and Image Analysis Research Centre (MARIARC), The University of Liverpool, Liverpool, United Kingdom;
2 Medical Imaging Department, The University of Liverpool, United Kingdom; 3 Imaging Science and Biomedical Engineering, School
of Cancer and Imaging Sciences, The University of Manchester, United Kingdom
Calibrated fMRI is a new technique that allows quantitative estimates of the relative changes in cerebral metabolic rate of oxygen (ÄCMRO2) and cerebral
blood flow (ÄCBF) that accompany neural activation. In this research we extend our previous work to study changes in neurovascular coupling over an age
range during a cognitive Stroop task.
37 volunteers (age range 20-70) were scanned using 3T MRI. We found BOLD response to the Stroop task increases with increasing age, calibration
constant A was found to reduce with age, a trend to reduced ÄCMRO2 with increasing age, and globally ÄCBF did not change with age.
1135. Error Propagation in CMRO2 Derivations Using CBF and BOLD Imaging
Hsiao-Wen Chung 1 , Wen Chau Wu
1 Electrical Engineering, National Taiwan University, Taipei, Taiwan, Taiwan
The purpose of this study is therefore to investigate the issues error propagation in CMRO2 estimations under different CNR. Results from our error
propagation study suggest that CMRO2 estimations using CBF and BOLD are valid only when the CNR for CBF measurements is sufficiently large, or
when the underlying changes in CMRO2 and CBF are sufficiently large as in hypercapnic experiments. Validity of current instantaneous CMRO2
measurements for resting-state brain functional studies is therefore in some doubt.
1136. Effects of the ValSalva Maneuver and Hypercapnia on the BOLD Signal
Daniel A. Handwerker 1 , Paula Wu 1,2 , Ronald M. Harper 3 , Peter A. Bandettini 1,4
1 Section on Functional Imaging Methods, National Institute of Mental Health, Bethesda, MD, United States; 2 Neuroscience,
University of California, Los Angeles, Los Angeles, CA, United States; 3 Neurobiology, David Geffen School of Medicine, UCLA,
Los Angeles, CA, United States; 4 Functional MRI Facility, National Institute of Mental Health, Bethesda, MD, United States
Hypercapnia creates global changes in cerebral blood flow, volume, and oxygenation that can be measured with fMRI and used for calibration. Breathholding
is a simple way to induce hypercapnia, but it may alter thoracic chest pressure and include a ValSalva effect. We alter chest pressure while keeping
the hold duration constant to see how the BOLD signal changes. The initial BOLD undershoot and following peak scale with pressure. Because the precise