title: 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.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Radiological Technology, Faculty of Allied Health Sciences, Naresuan University, Phitsanulok, 65000, Thailand. supawitoos@nu.ac.th.
authors.forename: Supawitoo
authors.initials: S
authors.lastname: Sookpeng
authors.affiliation: Department of Radiological Technology, Faculty of Allied Health Sciences, Naresuan University, Phitsanulok, 65000, Thailand.
authors.forename: Chitsanupong
authors.initials: C
authors.lastname: Butdee
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging*; D006801:Humans; D007908:Lens, Crystalline / Q000528:radiation effects*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
keywords: Absorbed dose; CT brain; Eye lens; Tube current modulation