Patient dose reduction in CT screening of nasal sinuses: results of clinical verification

Screening examinations of the nasal sinuses using computed tomography (CT) has become a more common diagnostic procedure. The aim of the study was clinical verification of the possibility of patient dose reduction in CT screening of nasal sinuses. A Siemens Somatom AR Star was used for the investigations. First, image quality indicators (contrast and spatial resolution) were analyzed in relation to the intensity of the scanning x-ray beam using a Catphan phantom. Dosimetric evaluation was also performed. The results showed no worsening in the visualization of low-contrast objects when the anode current was lowered from 105 mA to 63 mA; only the size of the smallest detectable object was slightly greater. Spatial resolution was also not changed. The clinical study involved examination of the sinuses of 100 patients. Five details of the image of diagnostic value were analyzed. The routine value of anode current was applied in 50 patients, while the other 50 had the reduced current. The diagnostic images were scored by two independent radiologists who did not know the parameters used during the examinations. To make the results objective, semiquantitative analysis was used. Diagnostic images obtained with the routinely used and at the reduced anode current did not show ny differences in the visualization of the selected image details. Screening CT examinations of nasal sinuses can be performed at a reduced anode current with no loss of diagnostic significance of the examination. The dose to the patient is reduced by 40% when the modified protocol is implemented. (author)