title: CT breast dose reduction with the use of breast positioning and organ-based tube current modulation.
abstract: OBJECTIVE
  This study aimed to investigate the breast dose reduction potential of a breast-positioning (BP) technique for thoracic CT examinations with organ-based tube current modulation (OTCM).
  
  
  METHODS
  This study included 13 female anthropomorphic computational phantoms (XCAT, age range: 27-65 y.o., weight range: 52-105.8 kg). Each phantom was modified to simulate three breast sizes in standard supine geometry. The modeled breasts were then morphed to emulate BP that constrained the majority of the breast tissue inside the 120° anterior tube current (mA) reduction zone. The OTCM mA value was modeled using a ray-tracing program, which reduced the mA to 20% in the anterior region with a corresponding increase to the posterior region. The organ doses were estimated by a validated Monte Carlo program for a typical clinical CT system (SOMATOM Definition Flash, Siemens Healthcare). The simulated organ doses and organ doses normalized by CTDIvolwere used to compare three CT protocols: attenuation-based tube current modulation (ATCM), OTCM, and OTCM with BP (OTCMBP).
  
  
  RESULTS
  On average, compared to ATCM, OTCM reduced breast dose by 19.3 ± 4.5%, whereas OTCMBPreduced breast dose by 38.6 ± 8.1% (an additional 23.8 ± 9.4%). The dose saving of OTCMBPwas more significant for larger breasts (on average 33, 38, and 44% reduction for 0.5, 1, and 2 kg breasts, respectively). Compared to ATCM, OTCMBPalso reduced thymus and heart dose by 15.1 ± 7.4% and 15.9 ± 6.2% respectively.
  
  
  CONCLUSIONS
  In thoracic CT examinations, OTCM with a breast-positioning technique can markedly reduce unnecessary exposure to radiosensitive organs in anterior chest wall, specifically breast tissue. The breast dose reduction is more notable for women with larger breasts.
authors.affiliation: Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina, 27705, USA.
authors.forename: Wanyi
authors.initials: W
authors.lastname: Fu
authors.affiliation: Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Department of Biomedical Engineering, Duke University, Durham, North Carolina, 27705, USA.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Tian
authors.affiliation: Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University, Durham, North Carolina, 27705, USA.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Sturgeon
authors.affiliation: Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University, Durham, North Carolina, 27705, USA.
authors.forename: Greeshma
authors.initials: G
authors.lastname: Agasthya
authors.affiliation: Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Department of Biomedical Engineering, Duke University, Durham, North Carolina, 27705, USA.
authors.forename: William Paul
authors.initials: WP
authors.lastname: Segars
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan, 48109, USA.
authors.forename: Mitchell M
authors.initials: MM
authors.lastname: Goodsitt
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan, 48109, USA.
authors.forename: Ella A
authors.initials: EA
authors.lastname: Kazerooni
authors.affiliation: Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Medical Physics Graduate Program, Departments of Physics, Biomedical Engineering, and Electrical and Computer Engineering, Duke University, Durham, North Carolina, 27705, USA.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Samei
mesh_terms: D000328:Adult; D001940:Breast / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000528:radiation effects; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008875:Middle Aged; D009010:Monte Carlo Method; D009929:Organ Size; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed / Q000009:adverse effects / Q000379:methods*
keywords: Monte Carlo; Organ-based tube current modulation; breast dose; organ dose; thoracic CT