Naslov
Factors affecting radiation dose at coronary CT angiography

Autori
Huljev, Vitomir ; Hrabak Paar, Maja

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, pp prezentacija, znanstveni

Skup
European Congress of Radiology ECR 2019

Mjesto i datum
Beč, Austrija, 27.02.2019

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Radioprotection ; Radiation dose ; Cardiac ; CT-Angiography ; Radiation safety

Sažetak
Aim and objective: The radiation dose at coronary CT angiography (CCTA) is usually expressed as volume CT dose index (CTDIvol) and dose length product (DLP). However, these indices represent scanner output and are independent of the patient size. In this study, we wanted to evaluate the size-specific dose estimate (SSDE) for CCTA and to identify factors associated with the increased patient dose. Methods and Materials: We retrospectively evaluated the CCTA of all patients that underwent scan between July and September 2017 at the University Hospital Centre Zagreb. Scanning was performed on a 128-slice CT scanner (Somatom Definition AS, Siemens) which uses automatic exposure and tube voltage control with prospective/retrospective ECG-gating, depending on the heart rate (HR) and HR variability. From scans archived in picture archiving and communication system (PACS) we read: area of the scan (whole chest vs. heart only), type of ECG-gating (prospective vs. retrospective), peak tube voltage (80, 100 or 120 kV), HR, HR variability, and radiation dose estimates (CTDIvol expressed for the 32 cm reference phantom, and DLP). Lateral (LAT) and anterior-posterior (AP) chest diameters were measured for each patient on CT radiographs at the widest point of the chest. Effective diameter (ED) was calculated using equation written in AAPM Report No. 204, ED=√(LAT×AP). Conversion factor (fsize) was read for every value of ED. SSDE was calculated by multiplying CTDIvol with fsize. Spearman's rank correlation coefficient (rs) was calculated between radiation dose estimates (CTDIvol, DLP, and SSDE) and variables describing patient habitus, HR, HR variability, and scanning technique. Results: There was a total of 53 patients, age range 27 – 80 (median 63 years), 25 males (47%) and 28 females (53%). Prospective ECG-gating was performed in 16 scans (30%), these patients were younger (median 59.5 vs. 64 years ; p < 0.049), and had lower HR (median 57 vs. 63 bpm ; p < 0, 014) than those in which retrospective ECG-gating was performed. Peak tube voltage of 80 kV was used in 15 scans (28%), 100 kV in 28 scans (53%), and 120 kV in 10 scans (19%). LAT ranged 31.0 – 48.3 cm (median 37.6 cm), AP 21.9 – 38.2 cm (median 28.9), ED 26 – 40 cm (median 33 cm), and fsize 0.85 – 1.43 (median 1.1). CTDIvol ranged 3.3 – 59.3 mGy (median 13.1 mGy), DLP 45.5 – 1310.4 mGycm (median 191.9 mGycm), and SSDE 4.1 – 56.6 mGy (median 15.2 mGy). Values of CTDIvol (6.8 vs. 14.6 mGy ; p < 0.03), DLP (148 vs. 268 mGycm ; p < 0.03), and SSDE (7.6 vs. 16.1 mGy ; p < 0.01) were lower with the prospective ECG-gating. CTDIvol, DLP, and SSDE correlated with LAT (rs = 0.427 ; rs = 0.343 ; rs = 0.323), AP (rs = 0.520 ; rs = 0.382 ; rs = 0.418), and ED (rs = 0.523 ; rs = 0.395 ; rs = 0.406). We found that in men correlations between SSDE and LAT (rs = 0.436, p = 0.029), AP (rs = 0.454, p = 0.023), and ED (rs = 0.483, p = 0.014) were higher than in whole population, while whereas in women correlations were lower and were not statistically significant. Conclusion: Because SSDE is an index corrected for patients size, it is expected to be independent of patient size. The positive correlation between SSDE and chest diameters in male patients suggests that radiation dose in larger patients increased more than expected, which was not the case in female patients.

Izvorni jezik
Engleski

Znanstvena područja
Kliničke medicinske znanosti

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