title: A head phantom study for intraocular dose evaluation of 64-slice multidetector CT examination in patients with suspected cranial trauma.
abstract: OBJECTIVE
  In cases of suspected cranial trauma, cranial CT examinations should be performed to rule out pathology. There are some methods available for reducing intraocular doses; however, it is difficult for the operators to conduct the necessary measurements because of restrictions in time and patient mobility, especially in high-energy trauma cases. Therefore, we performed a head phantom study for intraocular dose evaluation of 64-slice multidetector CT examination in patients with suspected cranial trauma.
  
  
  METHODS
  Assuming that the orbitomeatal (OM) line and bed were vertical, a head phantom was tilted from 10 degrees caudally to 25 degrees cranially at 5-degree intervals. At each tilted position, the phantom was examined using a 64-section multidetector CT device using three acquisition protocols. Intraocular doses during each examination were measured using small dosimeters.
  
  
  RESULTS
  Assuming that the OM line and bed were vertical, intraocular doses varied between 52 and 140%, 17-138%, and 90-142% during helical, non-helical, and helical CT angiographic examinations, respectively. Intraocular doses increased when the phantom was tilted cranially.
  
  
  CONCLUSIONS
  If possible, the best way to reduce the intraocular dose is by angling the gantry cranially, tilting the head of each patient caudally and adopting a non-helical acquisition method. During procedure, the acquisition angle should be angled cranially more than 0 degrees based on the OM line. The estimation of intraocular dose using the acquisition angle and displayed volumetric CT dose index might be useful to evaluate the deterministic effect risks and to inform patients about the associated risks.
authors.affiliation: Department of Quantum Medical Technology, Faculty of Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942, Japan. matsuk@mhs.mp.kanazawa-u.ac.jp
authors.forename: Kosuke
authors.initials: K
authors.lastname: Matsubara
authors.forename: Kichiro
authors.initials: K
authors.lastname: Koshida
authors.forename: Kimiya
authors.initials: K
authors.lastname: Noto
authors.forename: Tadanori
authors.initials: T
authors.lastname: Takata
authors.forename: Masayuki
authors.initials: M
authors.lastname: Suzuki
authors.forename: Tetsunori
authors.initials: T
authors.lastname: Shimono
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Matsui
mesh_terms: D006259:Craniocerebral Trauma / Q000000981:diagnostic imaging*; D005123:Eye / Q000528:radiation effects*; D005898:Glass; D006801:Humans; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed / Q000379:methods*