A methodological approach for the comparison of CT systems in terms of radiation dose and image quality

Abstract

Purpose

This study aims to apply a comparative methodology for two different computed tomography (CT) scanners, by evaluating patient radiation dose and image quality.

Materials & methods

A total of 189 consecutive non-enhanced and enhanced abdominal examinations, were performed using General Electric Revolution GSI (scanner A) and Siemens Somatom Drive (scanner B) scanners. Both protocols had been previously optimized by the same team for the two scanners, ensuring consistent image quality during comparison. CT dose index volume (CTDI_vol) and dose-length product (DLP) were recorded, and percent dose difference between scanners was estimated. Image quality was objectively assessed using image noise and contrast-to-noise ratio (CNR), and subjectively with a five-point scale. Utilizing the same protocols, an anthropomorphic phantom was irradiated to estimate organ doses. Statistical analysis was conducted to compare the examined parameters.

Results

The CTDI_vol and DLP for two scanners were 16.4–21.8 mGy and 494.7–1030.3 mGy*cm, respectively. Doses for scanner B were up to 41 % lower than scanner A. No significant CTDI_vol and DLP differences were found for unenhanced scans. Organ doses ranged from 5.0 to 16.9 mGy for both scanners, with scanner B delivering lower doses. Image quality was comparable between two CT systems. No statistical differences were found for image quality parameters, except for CNR in non-enhanced examinations. Radiologists’ ratings were consistent with the objective assessment.

Conclusion

A methodology was applied to compare two different CT scanners, regardless of patient selection criteria. Scanner B achieved lower doses for contrast-enhanced exams than scanner A.