European Journal of Radiology 64 (2007) 111–118 Dynamic perfusion CT: Optimizing the temporal resolution for the calculation of perfusion CT parameters in stroke patients Andreas K¨ amena a,∗,1 , Florian Streitparth a,∗,1 , Christian Grieser a , Lukas Lehmkuhl a , Basil Jamil b , Katarzyna Wojtal a , Jens Ricke a , Maciej Pech a a Department of Radiology, Charit´ e-Medical University Berlin, Augustenburger Platz 1, D-13353 Berlin, Germany b Department of Radiotherapy, Charit´ e-Medical University Berlin, Schumannstr. 20/21, D-10117 Berlin, Germany Received 15 October 2006; received in revised form 13 February 2007; accepted 23 February 2007 Abstract Purpose: To assess the influence of different temporal sampling rates on the accuracy of the results from cerebral perfusion CTs in patients with an acute ischemic stroke. Material and methods: Thirty consecutive patients with acute stroke symptoms received a dynamic perfusion CT (LightSpeed 16, GE). Forty millilitres of iomeprol (Imeron 400) were administered at an injection rate of 4 ml/s. After a scan delay of 7 s, two adjacent 10 mm slices at 80 kV and 190 mA were acquired in a cine mode technique with a cine duration of 49 s. Parametric maps for the blood flow (BF), blood volume (BV) and mean transit time (MTT) were calculated for temporal sampling intervals of 0.5, 1, 2, 3 and 4s using GE’s Perfusion 3 software package. In addition to the quantitative ROI data analysis, a visual perfusion map analysis was performed. Results: The perfusion analysis proved to be technically feasible with all patients. The calculated perfusion values revealed significant differences with regard to the BF, BV and MTT, depending on the employed temporal resolution. The perfusion contrast between ischemic lesions and healthy brain tissue decreased continuously at the lower temporal resolutions. The visual analysis revealed that ischemic lesions were best depicted with sampling intervals of 0.5 and 1 s. Conclusion: We recommend a temporal scan resolution of two images per second for the best detection and depiction of ischemic areas. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Perfusion CT (PCT); Stroke; Apoplexy; Cerebral infarction; Computed tomography (CT) 1. Introduction Strokes represent a leading cause of mortality in the world and are the most common cause of disability in countries of the Western hemisphere [1]. Clinical trials have proved the benefit of thrombolysis when performed within 3–6 h after the onset of an acute ischemic stroke [2,3]. The target of thrombolytic ther- apy is the area of penumbra (severely hypoperfused tissue that is at risk of infarction) [4–6]. Careful patient selection is essential, as thrombolysis following an acute stroke significantly increases the risk of a secondary hemorrhagic transformation [4,5]. The definitive clinical diagnosis of an acute stroke is often difficult, ∗ Corresponding authors. Tel.: +49 30 450 657143; fax: +49 30 450 557907. E-mail address: andreas.kaemena@charite.de (A. K¨ amena). 1 Both authors contributed equally to this work and are the corresponding authors. so that neuroimaging is becoming increasingly important as part of stroke management. Magnetic resonance perfusion-weighted imaging, positron emission tomography, xenon-enhanced com- puted tomography and single photon emission tomography have all been used to assess cerebral perfusion, but the complexity of these methods, their expense and limited availability restrict their usefulness in patients suspected of having an ischemic brain lesion [5]. Computed tomography (CT) remains the inves- tigation of choice to exclude acute intracranial hemorrhage. Lately, developments in perfusion CT (PCT) techniques have been proved highly valuable in the early assessment of ischemic areas of the brain. The CT determination of tissue perfusion is based on the relationships between the arterial, tissue and poten- tially the venous enhancement after the introduction of a bolus of contrast media [7]. The main advantage of PCT with spi- ral or multi-detector CT scanners over other cerebral perfusion imaging methods is that it can be performed immediately after a non-enhanced cranial CT, with a rapid generation of perfusion 0720-048X/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2007.02.025