Abstract WP51: Quantification of the Time of Flight (TOF) Angiography Signal to Predict Grade of Stenosis and Hypoperfusion

Introduction and hypothesis: MR-TOF angiography (magnetic resonance time of flight) offers a rapid, non-invasive assessment of the intracranial vessel status in patients with cerebrovascular diseases. As the signal of the MR-TOF is flow-dependent, we hypothesized that a quantification can predict perfusion of the respective flow territory as well as degree of proximal stenosis. Methods: Within the PEGASUS study (WHO REG-NR DRKS00003198) we performed intracranial TOF angiography and perfusion imaging with a contrast agent (DSC, dynamic susceptibility-weighted contrast-enhanced) in patients with chronic unilateral stenosis (>70%) or occlusion of the internal carotid artery. Images were acquired on a 3 Tesla MRI (TimTrio, Siemens). The TOF signal was quantified on 2D maximal intensity projections (MIPs): Regions of interest (ROIs) were placed into the M1 segment of the middle cerebral artery (MCA). A TOF ratio was calculated: relTOF[%]=ROIipsi/ROIcontra. The relative cerebral blood flow (relCBF) in the MCA territory was calculated in %. RelCBF and relTOF were correlated (Spearman). Receiver operating characteristic (ROC) analysis defined the performance of the TOF ratio to assess cortical hypoperfusion (defined as relCBF Results: In 40 patients (median 57yrs), we found a moderate correlation for relCBF and relTOF (rho: 0.52, p The ROC analysis identified a TOF ratio Conclusion: The intracranial TOF ratio is an easily accessible clinical measure to estimate distal brain perfusion and proximal vessel pathology in patients with chronic stenosis of the internal carotid artery.