Establishing Local Diagnostic Reference Levels in Adult Uroscan CT Examinations using Size-Specific dose Estimates (SSDE) and Ctdivol in Morocco

Abstract

CTDI_vol is a commonly used dose metric in CT scans, calculated based on a 16 cm or 32 cm diameter phantom. However, CTDI_vol does not provide an accurate representation of the patient’s actual dose. The Size-Specific Dose Estimate (SSDE) is a dose parameter that takes into account the patient’s body size, specifically the Effective Diameter (ED). This study aims to report the SSDE and CTDI_vol values for adult uroscan examinations in Morocco in order to establish local diagnostic reference levels (DRLs) for CT exams and to determine the correlation between these two metrics.

The study was conducted at the University Hospital of Casablanca with a sample of 52 adult patients undergoing uroscan examinations. SSDE values were calculated using the method described in AAPM Report No. 204. The results showed that, in general, SSDE values were higher than CTDIvol values for the same patients. Furthermore, the highest SSDE and CTDIvol values were observed: 26.18 mGy and 20.95 mGy, respectively, for the GE Revolution EVO 64-slice scanner, and 15.10 mGy and 10.79 mGy for the GE Optima CT 540 16-slice scanner. These results highlight the influence of patient size on dose calculations, with SSDE showing potential as a key parameter in establishing DRLs, as indicated by the high correlation coefficient (R² = 0.8992).