Patients suffering from cerebral ischemia or subarachnoid hemorrhage, undergo a 4D (3D+time) CT Perfusion
(CTP) scan to assess the cerebral perfusion and a CT Angiography (CTA) scan to assess the vasculature. The
aim of our research is to extract the vascular information from the CTP scan. This requires thin-slice CTP
scans that suffer from a substantial amount of noise. Therefore noise reduction is an important prerequisite
for further analysis. So far, the few noise filtering methods for 4D datasets proposed in literature deal with
the temporal dimension as a 4th dimension similar to the 3 spatial dimensions, mixing temporal and spatial
intensity information. We propose a bilateral noise reduction method based on time-intensity profile similarity
(TIPS), which reduces noise while preserving temporal intensity information. TIPS was compared to 4D bilateral
filtering on 10 patient CTP scans and, even though TIPS bilateral filtering is much faster, it results in better
vessel visibility and higher image quality ranking (observer study) than 4D bilateral filtering.
3D CT Angiography (CTA) scans are currently used to assess the cerebral arteries. An additional 4D CT
Perfusion (CTP) scan is often acquired to determine perfusion parameters in the cerebral parenchyma. We
propose a method to extract a three dimensional volume showing either the arteries (arteriogram) or the veins
(venogram) from the 4D CTP scan. This would allow cerebrovascular assessment using the CTP scan and obviate
the need for acquiring an additional CTA scan. Preprocessing steps consist of registration of the time volumes
of the CTP scan using rigid registration and masking out extracranial structures, bone and air. Next a 3D
volume is extracted containing the vessels (vascular volume) by using the absolute area under the first derivative
curve in time. To segment the arteries and veins we use the time to peak of the contrast enhancement curve
combined with region growing within a rough vessel segmentation. Finally the artery/vein segmentation is used
to suppress either the veins or the arteries in the vascular volume to construct the arteriogram and venogram.
To evaluate the method, 11 arteriograms and venograms were visually inspected by an expert observer, with
special attention to the important cerebral arteries (Circle of Willis) and veins (straight and transverse sinus).
Results show that the proposed method is effective in extracting the major cerebral arteries and veins from CTP