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Description
Background and objective: CT is a major contributor to the collective medical radiation dose, highlighting the continuous need for optimization particularly for higher-dose examinations such as CT perfusion (CTP). This study aimed to estimate the effective (E, mSv) and eye lens dose (mGy), and to assess imaging protocol (IP) performance.Materials and methods: CT protocols for 1,020 patients were audited for the emergency department using a Siemens SOMATOM Definition Edge with 128 slices. The scan protocol included: topogram, non-contrast, premonitoring, monitoring (timing), CTA (arch-to-vertex), and brain perfusion (CTP). Patient dose metrics were dose-length product (DLP, mGy·cm) and volume CT dose index (CTDIvol, mGy). The effective dose was extracted from the dose management system and is vendor-estimated based on ICRP 103. Results: Repeat CTA and/or CTP occurred in 2.2% of encounters and were associated with higher total procedure DLP: mean ±SD 2957.5±573 mGy·cm, median 3103.27, P75 3273.54, range 1295.0–3720.9 compared with the standard protocol (CTA=1 and CTP=1), which represented 86.3% of encounters with mean ±SD 2611.65±378.78 mGy·cm, median 2608.33, P75 2702.54. CTDIvol for the standard protocol was mean ±SD 80.79±2.12 mGy, median 80.60, P75 80.95, range 58.96–89.32. The median effective dose for standard protocol was 16.33 mSv (range 9.36–63.27). Eye lens dose was approximately estimated as 0.62 × CTDIvol, based on published brain CTP data. Conclusions: Patient dose from standard CTP protocol is comparable to or lower than published data. Significant variation in total CTP dose (4-fold) while CTDIvol showed minimal variation (1.5-fold), suggesting the variation was due to the number of scans and scan length. Reduction of eye lens dose is necessary to minimize lens tissue-reaction (cataract) risk. Practical optimization efforts should therefore prioritize preventing repeat scans and tightening scan coverage while maintaining diagnostic performance.