Optimizing data acquisition strategies for cerebral CT perfusion (CTP) studies is difficult in clinical practice. Therefore, we have developed a hybrid digital phantom to study the influence of various acquisition parameters on CTP maps. The purpose of this work is to introduce the hybrid digital phantom and to compare the perfusion maps from phantom data with the perfusion maps from patient data.

Construction of the phantom The phantom uses scans of an epoxy-filled human skull to provide a homogeneous background with realistic noise patterns derived from a 320-row CT scanner. The epoxy-filled human skull was scanned multiple times at various exposure settings ( Fig. 1a). A volume of interest (VOI) of 64 x 64 x 30 voxels is selected from the epoxy-filled human skull ( Fig. 1b) in which ring and cupping artefacts are least present. This VOI contains a realistic noise pattern that simulates the situation...

Measured noise in CBF maps from patient and phantom data was within 13% (1.9-23.9%) of each other. CNR for CBF maps derived from the phantom (20mm object) and patient data correlated well (R = 0.93).

The phantom provides a good estimate of real noise in CTP maps and allows for measuring CNR. With the hybrid digital phantom we are able to examine timing and distribution of radiation dose over time and we can predict how the noise propagates to patient measurements. It can play a major role for future optimization of CTP protocols without having to expose patients to unnecessary radiation. ACKNOWLEDGMENTS We would like to thank Dr. Marianne van Walderveen from Leiden University Medical Center and Drs. Tom van...

1. Kudo K. Perfusion Mismatch Analyzer, version3.4.0.6 ASIST-Japan Web site. http://asist.umin.jp/index-e.htm.

Marcel Oei, MD Department of Radiology Radboud University Nijmegen Medical Centre Geert Grooteplein 10 6500 HB Nijmegen The Netherlands [email protected] +31 24 3618766