title: Absorbed radiation dose in radiosensitive organs during coronary CT angiography using 320-MDCT: effect of maximum tube voltage and heart rate variations.
abstract: OBJECTIVE
  The purpose of this article is to estimate the absorbed radiation dose in radiosensitive organs during coronary MDCT angiography using 320-MDCT and to determine the effects of tube voltage variation and heart rate (HR) control on absorbed radiation dose.
  
  
  METHODS
  Semiconductor field effect transistor detectors were used to measure absorbed radiation doses for the thyroid, midbreast, breast, and midlung in an anthropomorphic phantom at 100, 120, and 135 kVp at two different HRs of 60 and 75 beats per minute (bpm) with a scan field of view of 320 mm, 400 mA, 320 × 0.5 mm detectors, and 160 mm collimator width (160 mm range). The paired Student's t test was used for data evaluation.
  
  
  RESULTS
  At 60 bpm, absorbed radiation doses for 100, 120, and 135 kVp were 13.41 ± 3.59, 21.7 ± 4.12, and 29.28 ± 5.17 mGy, respectively, for midbreast; 11.76 ± 0.58, 18.86 ± 1.06, and 24.82 ± 1.45 mGy, respectively, for breast; 12.19 ± 2.59, 19.09 ± 3.12, and 26.48 ± 5.0 mGy, respectively, for lung; and 0.37 ± 0.14, 0.69 ± 0.14, and 0.92 ± 0.2 mGy, respectively, for thyroid. Corresponding absorbed radiation doses for 75 bpm were 38.34 ± 2.02, 59.72 ± 3.13, and 77.8 ± 3.67 mGy for midbreast; 26.2 ± 1.74, 44 ± 1.11, and 52.84 ± 4.07 mGy for breast; 38.02 ± 1.58, 58.89 ± 1.68, and 78 ± 2.93 mGy for lung; and 0.79 ± 0.233, 1.04 ± 0.18, and 2.24 ± 0.52 mGy for thyroid. Absorbed radiation dose changes were significant for all organs for both tube voltage reductions as well as for HR control from 75 to 60 bpm at all tube voltage settings (p < 0.05). The absorbed radiation doses for the calcium score protocol were 11.2 ± 1.4 mGy for midbreast, 9.12 ± 0.48 mGy for breast, 10.36 ± 1.3 mGy for lung, and 0.4 ± 0.05 mGy for thyroid.
  
  
  CONCLUSIONS
  CT angiography with 320-MDCT scanners results in absorbed radiation doses in radiosensitive organs that compare favorably to those previously reported. Significant dose reductions can be achieved by tube voltage reductions and HR control.
authors.affiliation: Department of Radiology, Beth Israel Deaconess Medical Center, 1 Deaconess Rd., W/CC 308A, Boston, MA 02215, USA.
authors.forename: Boris
authors.initials: B
authors.lastname: Nikolic
authors.forename: Faisal
authors.initials: F
authors.lastname: Khosa
authors.forename: Pei-Jan Paul
authors.initials: PJ
authors.lastname: Lin
authors.forename: Atif N
authors.initials: AN
authors.lastname: Khan
authors.forename: Sheryar
authors.initials: S
authors.lastname: Sarwar
authors.forename: Chun-Shan
authors.initials: CS
authors.lastname: Yam
authors.forename: Laurence E
authors.initials: LE
authors.lastname: Court
authors.forename: Vassilios
authors.initials: V
authors.lastname: Raptopoulos
authors.forename: Melvin E
authors.initials: ME
authors.lastname: Clouse
mesh_terms: D001940:Breast / Q000528:radiation effects; D017023:Coronary Angiography / Q000295:instrumentation*; D005123:Eye / Q000528:radiation effects; D005260:Female; D006321:Heart / Q000528:radiation effects; D006339:Heart Rate / Q000528:radiation effects; D006801:Humans; D016018:Least-Squares Analysis; D008168:Lung / Q000528:radiation effects; D008297:Male; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D018570:Risk Assessment; D013961:Thyroid Gland / Q000528:radiation effects; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*