Sarah Cuddy and Elsayed Ali

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Thursday, December 18, 2014
3:30-5 pm
Multimedia room H2373 - 2nd floor - The University of Ottawa Heart Institute, 40 Ruskin Street

1. "Characterizing the effect of position dependent Poission-like noise in multi-pinhole cardiac SPECT"
Sarah Cuddy-Walsh - Carleton University
Abstract: A dedicated-cardiac single photon emission computed tomography (SPECT) camera using multiple pinholes with solid-state cadmium zinc telluride (CZT) detectors provides 2 × better energy resolution, > 4 × increase in camera sensitivity (allowing lower dose or shorter imaging time), and ~2.4 × better spatial resolution than traditional parallel-hole camera designs. The limited angle sampling of the fixed position design in the new camera however leads to a number of unique artifacts with unknown impact on image quality. Our work investigates the extent of these artifacts and how they might impact patient outcomes clinically. Two artifact effects will be discussed. First, the effect of variable pinhole sensitivity across the field of view (FOV) is shown to lead to a position dependent uncertainty in the reconstructed relative radiotracer uptake. Second, we will discuss the effect of having projection views from a limited number of angles on the reconstructed image resolution. Specifically we will look at the change in the resolution at different positions inside the FOV and with different object orientations. Conclusions from evaluating both effects may be used to aid in the interpretation of reconstructed images clinically and to make recommendations for future camera designs.

2. "Rotational artifacts in on-board cone-beam computed tomography"
Elsayed Ali - The Ottawa Hospital Cancer Centre
Abstract: Modern clinical linear accelerators are equipped with on-board x-ray imaging systems. These imaging systems are mainly used to acquire cone-beam computed tomography (CBCT) scans of the patient on the treatment table. The CBCT images help in reproducing the same patient position that was used to create the treatment plan. CBCT images can also, in principle, be used for dose calculations in adaptive planning. While an on-board imaging system is a valuable tool on the linac, it can introduce its own systematic errors in the radiation therapy process. This talk is about a systematic error in the Elekta on-board CBCT imaging systems in the form of a rotational artifact.