Program Information
Differences Observed in Radiation Doses Across 2 Similar CT Scanners From Adult Brain-Neck CT Angiography
K Fujii1,2*, K McMillan2 , M Bostani2 , C Cagnon2 , M McNitt-Gray2 , (1) Graduate School of Medicine, Nagoya University, Nagoya, Japan, (2) UCLA School of Medicine, Los Angeles, CA
Presentations
SU-E-I-31 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:
The aim of this study is to evaluate the difference in radiation doses from adult Brain-Neck CT angiography (CTA) between two CT scanners.
Methods:
We collected CT dose index data (CTDIvol, DLP) from adult Brain-Neck CTA performed with two CT scanners (Sensation 64 (S64) and Definition AS (AS), Siemens Healthcare) performed at two of our facilities from Jan 1st to Dec 31th, 2014. X-ray dose management software (Radmetrics, Bayer Healthcare) was used to mine these data. All exams were performed with Tube Current Modulation (Care Dose 4D), tube voltage of 120 kVp, quality reference mAs of 300, beam collimation of 64*0.6 mm. The rotation time was set to 0.5 sec for S64 and 1.0 sec for AS. We also scanned an anthropomorphic skull and chest phantom under routine Brain-Neck CTA protocol with the two scanners and extracted the tube current values from the raw projection data.
Results:
The mean CTDIvol and DLP in Brain-Neck CTA was 72 mGy and 2554 mGy*cm for AS, which was substantially larger than the mean values of 46 mGy and 1699 mGy*cm for S64. The maximum tube current was 583 mA for most cases on the S64 while the maximum was 666 mA for AS even though the rotation time set for AS was 1.0 sec. Measurements obtained with the anthropomorphic phantom showed that the tube current reached 583 mA at the shoulder region for S64 while it reached to 666 mA for AS.
Conclusion:
The results of this study showed that substantially different CT doses can result from Brain-Neck CTA protocols even when similar scanners and similar settings are used. Though both scanners have a similar maximum mA rating, differences in mA were observed through the shoulders, resulting in substantially different CTDIvol values.
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