Lukas Havla, Presenter: Nothing to Disclose

Kolja Thierfelder MD, MSc, Abstract Co-Author: Nothing to Disclose

Sebastian Ekkehard Beyer, Abstract Co-Author: Nothing to Disclose

Maximilian F. Reiser MD, Abstract Co-Author: Nothing to Disclose

Wieland H. Sommer MD, Abstract Co-Author: Nothing to Disclose

Olaf Dietrich PhD, Abstract Co-Author: Nothing to Disclose

Wavelet analysis is a powerful means for displaying angiographic data derived from dynamic CT perfusion acquisitions and for separating arterial and venous flow patterns.

Color-coded time-to-peak information of time-attenuation curves allows differentiating arterial feeders and normal veins (C.M. Strother et al. AJNR 2010). We propose the application of a time-domain wavelet transform on time-resolved cerebral CT perfusion data to differentiate arterial and venous vessels based on the scale information of the wavelet power spectrum (i.e., on the bolus dilation).

8 patients with suspected stroke were examined at multi-detector CT systems acquiring 32 dynamic phases (temporal resolution: 1.5s) of 99 slices (total slab thickness 99mm) at 80kV/350mAs. Typically, 35mL of iomeprol-350 were injected at a flow rate of 4.5mL/s. After initial rigid-body motion correction, the (“Paul order 4”) wavelet power spectrum for each pixel was calculated and its maximum value was defined as angiographic intensity; the scale value Smax where this maximum occurred (normalized to the value in the carotid arteries) was defined as marker for differentiating arterial and venous vessels. Smax was quantitatively evaluated in cerebral arteries (N=9, internal carotid/basilar/M1 middle cerebral/P1 posterior cerebral/M2 middle cerebral) and sinuses (N=5, sagittal/transverse/sigmoid) and compared to the time-to-peak TTTP parameter derived from CT perfusion data (after subtracting the time until bolus arrival in the carotid arteries). Mean (±standard deviation) normalized scale values were Smax arterial=1.00(±0.02) and Smax venous=1.22(±0.15) differing significantly (Mann-Whitney test p<0.0001); TTTP arterial yielded 0.16(±0.54)s and TTTP venous 4.84(±2.43)s (p<0.0001).

Our results show that bolus dilation during the passage through the vascular tree is sensitively mapped by the wavelet scale parameter; thus providing a new supplementary parameter for the separation of arteries and veins in addition to the time-to-peak information. This information might be used to improve the suppression of venous superposition in angiographic data or to color-code arterial and venous vessels.

Havla, L, Thierfelder, K, Beyer, S, Reiser, M, Sommer, W, Dietrich, O, Characterization of Arterial and Venous Vasculature Using the Bolus Width Derived from the Scale Information of the Wavelet Transform in Cerebral Perfusion CT.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012723.html