Signal-to-noise ratio and dose to the lens of the eye for computed tomography examination of the brain using an automatic tube current modulation system
The study aimed to evaluate the image quality in terms of signal-to-noise ratio (SNR) and dose to the lens of the eye and the other nearby organs from the CT brain scan using an automatic tube current modulation (ATCM) system with or without CT gantry tilt is needed.
An anthropomorphic phantom was scanned with different settings including use of different ATCM, fixed tube current time product (mAs) settings and degree angles of gantry tilt. Gafchromic film XR-QA2 was used to measure absorbed dose of the organs. Relative doses and SNR for the various scan settings were compared with the reference setting of the fixed 330 mAs.
Average absorbed dose for the lens of the eyes varied from 8.7 to 21.7 mGy. The use of the ATCM system with the gantry tilt resulted in up to 60% decrease in the dose to the lens of the eye. SNR significantly decreased while tilting the gantry using the fixed mAs techniques, compared to that of the reference setting. However, there were no statistical significant differences for SNRs between the reference setting and all ATCM settings.
Compared to the reference setting of the fixed effective mAs, using the ATCM system and appropriate tilting, the gantry resulted in a substantial decrease in the dose to the lens of the eye while preserving signal-to-noise ratio. CT brain examination should be carefully controlled to optimize dose for lens of the eye and image quality of the examination.
KeywordsCT brain Tube current modulation Absorbed dose Eye lens
The authors wish to thank Ms. Arunruk Surarit for her help in operating the CT scanner.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- 1.Smith-Bindman R, Miglioretti DL, Larson EB (2008) Rising use of diagnostic medical imaging in a large integrated health system: the use of imaging has skyrocketed in the past decade, but no one patient population or medical condition is responsible. Health Affairs (Project Hope) 27:1491–1502. doi: 10.1377/hlthaff.27.6.1491 CrossRefGoogle Scholar
- 2.Shrimpton PC, Hiller MC, Lewis MA, Dunn M (2005) Dose from computed tomography (CT) examinations in the UK-2003 review. National Radiological Protection Board, ChiltonGoogle Scholar
- 7.ICRP (2007) The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37 (2–4)Google Scholar
- 11.ICRP (2012) ICRP statement on tissue reactions/early and late effects of radiation in normal tissues and organs—threshold doses for tissue reactions in a radiation protection context. ICRP Publication 118. Ann. ICRP 41(1/2)Google Scholar
- 13.Grobe H, Sommer M, Koch A, Hietschold V, Henniger J, Abolmaali N (2009) Dose reduction in computed tomography: the effect of eye and testicle shielding on radiation dose measured in patients with beryllium oxide-based optically stimulated luminescence dosimetry. Eur Radio l19:1156–1160. doi: 10.1007/s00330-008-1241-1 CrossRefGoogle Scholar
- 17.Rego SL, Yu L, Bruesewitz MR, Vrieze TJ, Kofler JM, McCollough CH (2007) CareDose 4D CT automatic exposure control (AEC): physics principle and practical hints [online document] Available at http://mayoresearch.mayo.edu/mayo/research/ctcic/upload/rsna2007-care-dose-4d.pdf (Accessed: 10 Jan 2012)
- 21.Zhang D, Cagnon CH, Villablanca JP, McCollough CH, Cody DD, Stevens DM, Zankl M, Demarco JJ, Turner AC, Khatonabadi M, McNitt-Gray MF (2012) Peak skin and eye lens radiation dose from brain perfusion CT based on Monte Carlo simulation. AJR Am J Roentgenol 198:412–417. doi: 10.2214/AJR.11.7230 CrossRefPubMedPubMedCentralGoogle Scholar
- 22.Akhilesh P, Kulkarni AR, Jamhale SH, Sharma SD, Kumar R, Datta D (2016) Estimation of eye lens dose during brain scans using Gafchromic Xr-QA2 film in various multidetector CT scanners. Radiat Prot Dosimetry May 31Google Scholar