IMAGE QUALITY AND DOSE DISTRIBUTION IN MULTISCAN AND FAST RING CT SYSTEMS

Modem CT systems allow examinations with both multiscan and volumetric techniques. This study on image quality and dose distribution was car ried out varying the operating conditions (step and slice thickness) f or each technique. To describe the physical image quality two basic pa rameters were taken into account: spatial resolution and noise. The me asurements were performed using an acrylic phantom, which includes a s eries of inserts for the response to spatial frequencies and a uniform insert for noise evaluation. The phantom images recorded on the film by a multiformat laser printer were acquired with a TV digitiser syste m and processed with a customised software package. Dosimetric evaluat ions were performed along the longitudinal axis using an air density e quivalent phantom holding the TL dosemeters at the desired location.