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 <90%) and vessel pathology (occlusion vs stenosis).
Results: In 40 patients (median 57yrs), we found a moderate correlation for relCBF and relTOF (rho: 0.52, p<0.05). Patients with an occlusion (19/40) showed a significantly lower TOF ratio compared to patients with a stenosis (70% vs. 93%, p<.001). Also, perfusion was significantly reduced in patients with occlusions (median relCBF 89% vs. 95%, p<.05).
The ROC analysis identified a TOF ratio <78% as the best predictor for (i) cortical hypoperfusion (sensitivity/specificity 73%/72%, area under the curve 0.75) and (ii) for an occlusion of the ACI (sens./spec. 79%/86%, area under the curve 0.85).
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.
Author Disclosures: M.A. Mutke: None. V.I. Madai: None. S. Martin: None. F. von Samson-Himmelsternja: None. C. Herzig: None. S. Zweynert: None. T. Thamm: None. S. Hetzer: None. J. Sobesky: None.
- © 2016 by American Heart Association, Inc.