Adriënne Mirjam Mendrik MSc, Presenter: Research funded, Koninklijke Philips Electronics NV

Evert-Jan Vonken MD, PhD, Abstract Co-Author: Nothing to Disclose

Ewoud Joris Smit MSC, Abstract Co-Author: Nothing to Disclose

Bram van Ginneken PhD, Abstract Co-Author: Nothing to Disclose

Mathias Prokop MD, Abstract Co-Author: Nothing to Disclose

CT angiographic techniques for the evaluation of cranial arteries are hampered by venous overprojection. We present a fully automatic technique for reducing venous overprojection by extracting an arteriogram from cerebral CT perfusion (CTP) data. The reliability of this technique is tested on CTP scans of patients with subarachnoid hemorrhage.

From 25 patients with subarachnoid hemorrhage, cerebral CT perfusion scans (64x0.625mm collimation, 30 scans every 2s) were acquired during injection of 40 ml of contrast at 5ml/s, and reconstructed with 0.625mm thick sections. The proposed technique consists of two steps: extraction of a vessel image and arterial-venous separation. Vessel extraction was accomplished by calculating, for each voxel, the absolute area under the first Gaussian derivative over time at a sigma of 6s, which enhances vessels while suppressing background tissue. Arteries and veins are separated by automatically detecting a patient-specific threshold between the arterial and venous time-to-peak of the contrast enhancement curves. An experienced radiologist scored arterial completeness (0-100%) and suppression of overprojecting veins (0-100%) on the arteriogram using the vessel image as a reference. Scoring was performed separately for the various branches of the circle of Willis and the peripheral anterior, middle and posterior cerebral artery territories.

The average arterial completeness score for the circle of Willis arteries was 99.1% (median 100%, range 70% to 100%) and 89.4% (median 100%, range 50% to 100%) for the peripheral arteries. Venous overprojection was on average 88.2% suppressed (median 90-99%, range 20% to 100%) in the region of the circle of Willis and 76.4% (median 80-89%, range 40% to 99%) in the periphery.

Our post-processing technique for CTP data provides almost complete reduction of venous overprojection in cerebral arteriograms of the circle of Willis.

By successfully reducing venous overprojection, the proposed technique could simplify detection and characterization of aneurysms in subarachnoid hemmorhage patients.

Mendrik, A, Vonken, E, Smit, E, van Ginneken, B, Prokop, M, Reduction of Venous Overprojection Using Cerebral Arteriograms from CT Perfusion Scans of Subarachnoid Hemorrhage Patients.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8010831.html