Radiation dose reduction using spectral shaping in pediatric non-contrast sinus CT.

Abstract

CT is the standard imaging technique to evaluate pediatric sinuses. Given the potential risks of radiation exposure in children, it is important to reduce pediatric CT dose and maintain image quality. To study the utility of spectral shaping with tin filtration to improve dose efficiency for pediatric sinus CT exams. A head phantom was scanned on a commercial dual-source CT using a conventional protocol (120kV) and a proposed 100kV with a 0.4-mm tin filter (Sn100 kV) protocol for comparison. Entrance point dose (EPD) of eye and parotid gland region was measured by an ion chamber. Sixty pediatric sinus CT exams (33 acquired with 120kV, 27 acquired with Sn100 kV) were retrospectively collected. All patient images were objectively measured for image quality and blindly reviewed by 4 pediatric neuroradiologists for overall noise, overall diagnostic quality, and delineation of 4 critical paranasal sinus structures, using a 5-point Likert scale. Phantom CTDIvol from Sn100 kV is 4.35mGy, compared to CTDIvol of 5.73mGy from 120kV at an identical noise level. EPD of sensitive organs decreases in Sn100 kV (e.g., right eye EPD 3.83±0.42mGy), compared to 120kV (5.26±0.24mGy). Patients in the 2 protocol groups were age and weight (unpaired T test P>0.05) matched. The patient CTDIvol of Sn100 kV (4.45±0.47mGy) is significantly lower than 120kV (5.56±0.48mGy, unpaired T test P<0.001). No statistically significant difference for any subjective readers' score (Wilcoxon test P>0.05) was found between the two groups, indicating proposed spectral shaping provides equivalent diagnostic image quality. Phantom and patient results demonstrate that spectral shaping can significantly reduce radiation dose for non-contrast pediatric sinus CT without compromising diagnostic quality.