Acquisition strategy to reduce cerebrospinal fluid partial volume effects for improved DTI tractography.
OBJECTIVE
An acquisition method that does not increase scan time or specific absorption rate is investigated for reducing the deleterious effects of cerebrospinal fluid (CSF) partial volume effects on diffusion tensor imaging (DTI) tractography. It is based on using a shorter repetition time (TR) by means of slice acquisition re-ordering to reduce the signal of long T1 CSF and a non-zero minimum diffusion weighting (b-value) to attenuate rapidly diffusing CSF signal with respect to brain tissue.


METHODS
A target reduction of the CSF/brain signal ratio from 3.5 to 0.8 required a TR of 2.5 s and minimum b-value of 425 s/mm(2) . This was evaluated at 4.7 Tesla in eight healthy young adults for tractography of the fornix, which has considerable CSF contamination and is difficult to track from standard DTI.


RESULTS
This method effectively reduced CSF signal relative to brain and yielded more robust tractography, increased tract volume, increased fractional anisotropy, and decreased mean diffusivity in the fornix relative to standard DTI.


CONCLUSIONS
CSF partial volume effects in DTI can be mitigated in acquisition through reduced TR and non-zero minimum diffusion weighting. The lack of RF absorption rate or scan time increases is attractive over other CSF suppression methods such as inversion recovery.
Department of Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
Corey A
CA
Baron
Christian
C
Beaulieu
D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D002555:Cerebrospinal Fluid / Q000166:cytology*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D066127:White Matter / Q000033:anatomy & histology*
CSF; DTI; diffusion; fornix; partial volume