title: Estimation of organ-absorbed radiation doses during 64-detector CT coronary angiography using different acquisition techniques and heart rates: a phantom study.
abstract: BACKGROUND
  Though appropriate image acquisition parameters allow an effective dose below 1 mSv for CT coronary angiography (CTCA) performed with the latest dual-source CT scanners, a single-source 64-detector CT procedure results in a significant radiation dose due to its technical limitations. Therefore, estimating the radiation doses absorbed by an organ during 64-detector CTCA is important.
  
  
  OBJECTIVE
  To estimate the radiation doses absorbed by organs located in the chest region during 64-detector CTCA using different acquisition techniques and heart rates.
  
  
  METHODS
  Absorbed doses for breast, heart, lung, red bone marrow, thymus, and skin were evaluated using an anthropomorphic phantom and radiophotoluminescence glass dosimeters (RPLDs). Electrocardiogram (ECG)-gated helical and ECG-triggered non-helical acquisitions were performed by applying a simulated heart rate of 60 beats per minute (bpm) and ECG-gated helical acquisitions using ECG modulation (ECGM) of the tube current were performed by applying simulated heart rates of 40, 60, and 90 bpm after placing RPLDs on the anatomic location of each organ. The absorbed dose for each organ was calculated by multiplying the calibrated mean dose values of RPLDs with the mass energy coefficient ratio.
  
  
  RESULTS
  For all acquisitions, the highest absorbed dose was observed for the heart. When the helical and non-helical acquisitions were performed by applying a simulated heart rate of 60 bpm, the absorbed doses for heart were 215.5, 202.2, and 66.8 mGy for helical, helical with ECGM, and non-helical acquisitions, respectively. When the helical acquisitions using ECGM were performed by applying simulated heart rates of 40, 60, and 90 bpm, the absorbed doses for heart were 178.6, 139.1, and 159.3 mGy, respectively.
  
  
  CONCLUSIONS
  ECG-triggered non-helical acquisition is recommended to reduce the radiation dose. Also, controlling the patients' heart rate appropriately during ECG-gated helical acquisition with ECGM is crucial.
authors.affiliation: Department of Quantum Medical Technology, Faculty of Health Sciences, Kanazawa University, Kanazawa, 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: Tetsunori
authors.initials: T
authors.lastname: Shimono
authors.forename: Hiroko
authors.initials: H
authors.lastname: Kawashima
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Matsui
mesh_terms: D001853:Bone Marrow / Q000528:radiation effects; D001940:Breast / Q000528:radiation effects; D002138:Calibration; D017023:Coronary Angiography / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000528:radiation effects; D006339:Heart Rate; D006801:Humans; D008168:Lung / Q000528:radiation effects; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D012867:Skin / Q000528:radiation effects; D013950:Thymus Gland / Q000528:radiation effects; D014057:Tomography, X-Ray Computed / Q000379:methods*