orals 5th Asia-Pacific NMR Symposium 2013

CBV, CBF and BOLD weighted functional MRI at 7 Tesla using combined multi RF excitation and multi EPI readout (#63)

Steffen N Krieger 1 2 , Laurantius Huber 1 , Gary F Egan 2 , Benedikt Poser 3 , Robert Turner 1
  1. Neurophysics, Max-Plank Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
  2. Monash Biomedical Imaging, Clayton, VIC, Australia
  3. Cognitive Neuroscience, Maastricht University, Maastricht, The Netherlands

Functional magnetic resonance imaging (fMRI) is widely used for mapping spatial and temporal patterns of brain activity. Local cerebral functional activation leads to variances in the rate of oxyhaemoglobin and deoxyhaemoglobin and can be measured via the blood oxygenation level dependent (BOLD) contrast, the most common fMRI technique1 . However, the major drawback of BOLD is its limited spatial specificity. Therefore more physiologically and spatially specific biophysical quantities, such as cerebral blood flow (CBF) and cerebral blood volume (CBV) have started to be used for detecting cerebral functional activation. Arterial spin labelling (ASL)2,3,4   and vascular space occupancy (VASO)5,6   have been recently introduced to non-invasively measure CBF and CBV.

In this study a highly flexible single slice fMRI sequence is introduced being able to simultaneously measure BOLD, CBF and CBV weighted MRI signals. A fully adjustable adiabatic inversion (time resampled frequency offset corrected inversion pulse)7  is used for a 180° spin inversion. An arbitrary number of 90° RF excitation pulses can be followed by up to 25 echo planar imaging (EPI) readouts after each excitation enabling maximum flexibility regarding sequence design and study purpose. In this study, this MRI pulse sequence has been used for combining VASO and ASL spin preparation with the standard BOLD contrast technique in order to estimate three quantities within one TR of 3s8,9. Further imaging parameters are: 24-channel head coil, visual stimulation with standard 30s block design, isotropic resolution of 1.5mm, TEVASO,1=14ms, TEVASO,2=37ms, TEASL,1=14ms,  TEASL,2=37ms, TEBOLD=22ms, partial k-space readout of 6/8, TI1=1100ms, TI2=1650ms, TI3=2250ms.The pulse sequence design (Fig. 1) shows the applied RF pulses and the x,y and z-gradients. Good VASO, ASL and BOLD activation maps have been obtained (Fig. 2). This technique can be used to simultaneously study temporal and spatial characteristics of multiple MRI contrasts and improve our understanding of brain physiology. 



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  9. Krieger et al. ISMRM (2013)