Validation of SSDE calculation in a modern CT scanner and correlation with effective dose

Abstract

This study aims to validate the Size Specific Dose Estimate (SSDE) provided by a modern Computed Tomography (CT) scanner and investigate its correlation with effective dose (E). SSDE is a size-specific dosimetric index addressing the limitations of the Computed Tomography Dose Index (CTDI_vol). A set of 60 CT scans of anthropomorphic phantoms, including pediatric and obese models, were acquired and analyzed. SSDE values from the CT scanner were compared with those obtained through an independent Python-based calculation and Radimetrics, a dose monitor software. While the independent calculation and the one with Radimetrics were consistently in agreement, a systematic underestimation by the scanner up to 10% was seen, particularly in chest and abdominal exams. The underestimation, however, remained within the acceptable limits set by AAPM guidelines. Furthermore, a correlation between SSDE and effective dose was identified, suggesting SSDE's potential for more accurate, size-specific radiation dose and risk assessments. These findings highlight the importance of SSDE in enhancing patient-specific dose management, though further validation using patient data is needed to confirm its clinical applicability.

Keywords: CT; Effective dose; Radiation dose management; SSDE.

Fig. 1

Flowchart of the SSDE calculation process with the Python script for chest and abdomen examinations. In case of head scans, only the central slice is used in the calculation process.

Fig. 2

Bland-Altman analysis of SSDE obtained from Python, Radimetrics and Philips Incisive CT scanner. Data are divided according to anatomical districts as indicated in subplots’ titles.

Fig. 3

Effective dose calculated by Radimetrics plotted against the SSDE provided by the Philips Incisive CT scanner. Red lines represent linear fit in the form y = k*x. Data are divided according to anatomical districts.