Purpose Evaluation for potential ischemic risk following internal carotid artery (ICA) sacrifice assess cerebral perfusion during temporary ICA occlusion. Tc99m-Exametazime Single Photon Emission Computed Tomography (HMPAO-SPECT) represents a commonly accepted method for this purpose but is time inefficient, whereas angiographic based methods are less accepted but time efficient. This study compares automated angiographically derived parameters during ICA balloon test occlusion (BTO) to HMPAO-SPECT and manually derived angiographic parameters.
Materials/methods Aortic arch, selective ICA and vertebral artery arteriographic anteroposterior projections of the head (6 frames per seconds) from patients undergoing BTO with HMPAO-SPECT. Regions of interest (ROIs) were placed in the watershed zones (figure 1) both manually and using a custom made post-processing program MATLAB R2017a (The MathWorks Inc. 2017) and image J software (NIH). Time-density curves derived from the ROIs were analyzed both manually and automatically to calculate arterial arrival time (AAT), interhemispheric percent differences in peak contrast density (PCD) and Half Maximum Density Width (HMDW) (figure). Estimated cerebral blood volume (eCBV) was automatically derived using the central volume principle, from which cerebral blood flow (eCBF) was calculated as eCBV/HDMDW. Linear regression analysis compared automated derived parameters to manually derived parameters and to SPECT derived occluded versus non-occluded cerebral blood flow ratios (SPECT L/N ratios).
Results Nineteen patients with a mean age of 62 (sd=10.0) (12 male) were included. Manually and automatically derived PCD, HMDW delay and ATT had varying degrees of correlation (R2=0.9451, 0.9449 and 0.4176 respectively and high levels of agreement by Bland Altman analysis. Correlations between SPECT values and angiographically automatically derived values showed a strong linear relationship for PCD, HMDW, AAT and eCBF (R2=0.636, 0.680, 0.882, and 0.877 respectively). Measures of delay in AAT between selective and aortic arch studies had a mean 0.12 (SD=0.52) second difference which is attributable to cases with dominant posterior circulation supply due to differences in arrival time through the vertebral artery versus the carotid artery. This suggests that calculation of AAT on aortic arch arteriography may overestimate AAT in cases where collateral supply is posterior circulation dominant. In patients with no interhemispheric CBF difference by SPECT, AAT was under 0.5s.
Conclusions Preliminary data indicate that during BTO, PCD, HMDW, AAT and eCBF automatically derived from digital subtraction angiography images can provide an ischemic risk assessment comparable to HMPAO-SPECT. Close attention to the circle of Willis supply is needed for appropriate interpretation of the results.
Disclosures A. Salome: None. G. Christoforidis: 1; C; NIH. J. Fan: None. D. Kromrey: None. T. Carroll: 1; C; NIH.
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