AbstractID: 9010 Title: Comparative Evaluation of Image Quality from 3 CT Simulation
Scanners
INTRODUCTION: Today, radiation therapy is moving towards increased radiation dose to the tumour as a result of 3D conformal
RT (3DCRT) and intensity modulated RT (IMRT), which have been made possible by advances in volumetric-based image planning
with digital imaging systems like computed tomography (CT). Treatment planning for such radiation therapy requires superior CT
image quality. PURPOSE: Our goal is to evaluate and compare image quality of 3 CT simulation scanners available at our center.
These scanners include a conventional 70cm bore single slice scanner from Philips Medical Systems, a large 85cm bore single slice
scanner also from Philips and a standard bore multislice scanner from GE Medical Systems. METHODS: Image quality is evaluated
in terms of image noise, low contrast detectability (LCD), limiting spatial resolution and modulation transfer function, and slice
thickness accuracy. A commercially available Catphan phantom is used to characterize image quality for both axial and helical
mode scanning. RESULTS: Generally, image quality is comparable for all scanners, although the LightSpeed Plus multislice scanner
demonstrates better image quality in terms of noise content. DISCUSSION: As a result, this scanner shows better low contrast
detectability, particularly at very low nominal contrast levels of 0.3%, which is of significant clinical importance, particularly for soft
tissue delineation. In addition, while limiting spatial resolution and slice thickness accuracy are comparable for all three scanners for
both scanning modes, the multislice scanner evidently optimizes volume coverage speed and longitudinal resolution without
compromising image quality, a significant advantage in the radiation oncology environment.