Stroke Versus Seizure - Perfusion Computerized Tomography in a Patient with Aphasia.

Both stroke and seizures have varied clinical presentations and their differentiation in the acute setting is not always straightforward. We present the case of a patient who presented at the emergency room with acute onset aphasia. Clinically acute ischemic stroke was suspected. Perfusion CT was performed and demonstrated cortical hypervascularity in the left partietotemporal region. Additional MRI and EEG were performed and a final diagnosis of postictal aphasia was made. This case illustrates that perfusion CT is not only a useful tool for acute stroke management, but can also aid in the detection of seizures in patients presenting with stroke-like symptoms.

Fast generation of 4D PET-MR data from real dynamic MR acquisitions.

We have implemented and evaluated a framework for simulating simultaneous dynamic PET-MR data using the anatomic and dynamic information from real MR acquisitions. PET radiotracer distribution is simulated by assigning typical FDG uptake values to segmented MR images with manually inserted additional virtual lesions. PET projection data and images are simulated using analytic forward projections (including attenuation and Poisson statistics) implemented within the image reconstruction package STIR. PET image reconstructions are also performed with STIR. The simulation is validated with numerical simulation based on Monte Carlo (GATE) which uses more accurate physical modelling, but has 150× slower computation time compared to the analytic method for ten respiratory positions and is 7000× slower when performing multiple realizations. Results are validated in terms of region of interest mean values and coefficients of variation for 65 million coincidences including scattered events. Although some discrepancy is observed, agreement between the two different simulation methods is good given the statistical noise in the data. In particular, the percentage difference of the mean values is 3.1% for tissue, 17% for the lungs and 18% for a small lesion. The utility of the procedure is demonstrated by simulating realistic PET-MR datasets from multiple volunteers with different breathing patterns. The usefulness of the toolkit will be shown for performance investigations of the reconstruction, motion correction and attenuation correction algorithms for dynamic PET-MR data.