Utilization of MR angiography in perfusion imaging for identifying arterial input function
This research utilizes magnetic resonance angiography (MRA) to identify arterial locations during the parametric evaluation of concentration time curves (CTCs), and to prevent shape distortions in arterial input function (AIF).
Materials and methods
We carried out cluster analysis with the CTC parameters of voxels located within and around the middle cerebral artery (MCA). Through MRA, we located voxels that meet the AIF criteria and those with distorted CTCs. To minimize partial volume effect, we re-scaled the time integral of CTCs by the time integral of venous output function (VOF). We calculated the steady-state value to area under curve ratio (SS:AUC) of VOF and used it as a reference in selecting AIF. CTCs close to this reference value (selected AIF) and those far from it were used (eliminated AIF) to compute cerebral blood flow (CBF).
Eliminated AIFs were found to be either on or anterior to MCA, whereas selected AIFs were located superior, inferior, posterior, or anterior to MCA. If the SS:AUC of AIF was far from the reference value, CBF was either under- or over-estimated by a maximum of 41.1 ± 14.3 and 36.6 ± 19.2%, respectively.
MRA enables excluding voxels on the MCA during cluster analysis, and avoiding the risk of shape distortions.
KeywordsArterial input function Magnetic resonance imaging Perfusion imaging Magnetic resonance angiography Cerebral blood flow
This paper was supported by Bogazici University Scientific Research Project Unit, (project: BAP-07HX104D, “Fusion of Brain Fiber Tractography and Perfusion in Stereotactic Surgery”).
Buyuksarac contributed to the manuscript in project development, data collection, and data analysis. Ozkan contributed to the manuscript in project development.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the local institutional review board.
Informed consent was obtained from all individual participants included in the study.
Supplementary material (MOV 4818 kb)
The video illustrates the first pass of the contrast agent through the cerebral arteries. To visualize the arteries during the passage of the contrast agent, the MRA images were overlaid on top of the perfusion image series. The movie shows the slice containing the MCA. Red arrows point at the signal intensity drop that occurs as the contrast matter arrives at the MCA. Note that the speed of the video has been slowed down by a factor of 0.5 for better viewing.