Evaluating the Reproducibility of 3.0 Tesla MRI Continuous Arterial spin labeling in the Assessment of Cerebral Perfusion

Measurement of cerebral blood flow (CBF) provides useful information about
cerebrovascular sufficiency and regional metabolism. Arterial spin labeling
(ASL) is a non-invasive magnetic resonance imaging (MRI) technique for the
quantification of cerebral perfusion. ASL does not involve exposure to ionizing
radiation or radioactive isotopes. Therefore, it is an attractive tool compared
to standard clinical methods, especially in the pediatric population and in
longitudinal studies with repeated measurements.
During the recent years, technical improvements have been made and sequences
have been implemented. These are generally classified as continuous arterial
spin labeling (CASL) or pulsed arterial spin labeling (PASL). ASL is based on
magnetic labeling of arterial blood water protons, which are subsequently used
as an endogenous tracer. Magnetic inversion takes place in a plane proximal to
the brain. Labeled blood water spins move towards the brain microvasculature.
They have a decay rate of T1, which is sufficiently long to visualize perfusion
of brain tissue and brain microvasculature. Perfusion contrast is obtained by
subtraction of successively acquired labeled images and control images in which
no labeling of arterial blood water spins is performed . Multiple acquisitions
are averaged to improve the signal to noise ratio (SNR) and the final perfusion
signal. In order to obtain sufficient perfusion signal effect, ASL sequences
commonly consist of 40 to 60 paired acquisitions of labeled and controlled
scans.
The low perfusion signal is one of the concerns in the reproducibility of CASL.
Previously described CASL reproducibility studies were performed at 1.5 Tesla
MR scanners. Careful search of literature did not yield any information on CASL
reproducibility at 3.0 Tesla MRI. We suppose that a higher magnetic field
strength will ameliorate the signal to noise ratio (SNR) and thus have a
positive influence on reproducibility of CBF measurements. In case of a better
SNR, fewer acquisitions might suffice to accurately measure CBF. This could
reduce the total scan duration and the chance of movement between the
subsequent acquisitions and thus improve the clinical applicability of ASL.
Therefore the aim of this study will be to assess the inter- and intrasession
reproducibility of CASL and the convergence of CASL data at 3.0 Tesla MRI.

Our primary objective is:
To assess the reproducibility of CASL at 3.0T MRI in order to get an insight in
the applicability of CASL in daily clinical routine in the AMC

Our secondary objectives are:
To assess whether the standard CASL sequence could be shortened by using less
signal averages for the calculation of CBF
To compare mean CBF in the left and the right hemisphere
To compare mean CBF in men and women

For studying the inter-scan reproducibility and convergence of CASL, we will
measure CBF on three different occasions in a period of 3 weeks. To assess the
intra-scan reproducibility and convergence of CASL, we will perform 2 CASL
scans during each session.

This study is conducted using a non-invasive imaging modality: MRI. There is no
risk associated with participation. If abnormalities on the MR images are
apparent, a specialist will be consulted.