Hugo Gratama van Andel MS, Presenter: Nothing to Disclose

Henk Willem Venema PhD, Abstract Co-Author: Nothing to Disclose

Geert J. Streekstra PhD, Abstract Co-Author: Nothing to Disclose

Charles Bernard Majoie MD, PhD, Abstract Co-Author: Nothing to Disclose

Gerard J. Den Heeten MD, PhD, Abstract Co-Author: Nothing to Disclose

Cornelis A. Grimbergen PhD, Abstract Co-Author: Nothing to Disclose

CT perfusion (CTP) examinations of the brain are performed increasingly for the evaluation of cerebral blood flow in patients with stroke and vasospasm after subarachnoid hemorrhage. Of the same patient often also a CT angiography (CTA) examination is performed. This study investigates the possibility to obtain CTA images, both static and dynamic, from the CTP examination, thereby possibly obviating the CTA examination. This would save the patient exposure to radiation, contrast, and time.

With a Philips Brilliance-64 CT scanner (64x0.625mm) CTP examinations can be performed of 80mm of brain, using a ‘jog’ mode between two areas of 40mm wide. A CTP scan consists of a time-series of 15 3D-images (64x1.25mm; 80kV; 150mAs each) with an interval of 4s. Each CTP frame is a CTA image with a varying amount of contrast enhancement, and with high noise. To improve the signal-to-noise ratio all 3D images are combined into one 3D image, after matching to correct for patient motion. Optimal image combination consists of weighted averaging in which the weighting factor of each frame is proportional to the arterial contrast. This maximizes the arterial contrast-to-noise ratio. Another possibility is to observe the vascular anatomy dynamically by viewing the 15 frames in a cine loop. Optimally averaged and dynamic images were compared with regular CTA scans of the same region (120kV; 250mAs) in four patients.

In comparison with the CTA examination, optimally averaged CTP images appear to have an acceptable in-plane image quality and signal-to-noise ratio. The resolution in the z-direction can be improved upon, for instance if 128 images of 0.625 mm thickness could be used. Dynamic presentation of the CTA data is a definite bonus.

Optimally averaged CTP images have a quality that approximates the quality of regular CTA images. This could pave the way to significant dose reduction and patient discomfort in case both functional and anatomical information are required.

Next to providing the perfusion parameters, a CTP examination can be used to obtain both static and dynamic CTA images. This might obviate an extra CTA examination of the same scan region.

Gratama van Andel, H, Venema, H, Streekstra, G, Majoie, C, Den Heeten, G, Grimbergen, C, Intracranial CT Angiography Obtained from Cerebral CT Perfusion: A Feasibility Study.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5006558.html