title: Assessment of Mean Glandular Dose in Mammography System with Different Anode-Filter Combinations Using MCNP Code.
abstract: BACKGROUND
  X-ray mammography is one of the general methods for early detection of breast cancer. Since glandular tissue in the breast is sensitive to radiation and it increases the risk of cancer, the given dose to the patient is very important in mammography.
  
  
  OBJECTIVE
  The aim of this study was to determine the average absorbed dose of X-ray radiation in the glandular tissue of the breast during mammography examinations as well as investigating factors that influence the mean glandular dose (MGD). One of the precise methods for determination of MGD absorbed by the breast is Monte Carlo simulation method which is widely used to assess the dose.
  
  
  METHODS
  We studied some different X-ray sources and exposure factors that affect the MGD. "Midi-future" digital mammography system with amorphous-selenium detector was simulated using the Monte Carlo N-particle extended (MCNPX) code. Different anode/filter combinations such as tungsten/silver (W/Ag), tungsten/rhodium (W/Rh), and rhodium/aluminium (Rh/Al) were simulated in this study. The voltage of X-ray tube ranged from 24 kV to 32 kV with 2 kV intervals and the breast phantom thickness ranged from 3 to 8 cm, and glandular fraction g varied from 10% to 100%.
  
  
  RESULTS
  MGD was measured for different anode/filter combinations and the effects of changing tube voltage, phantom thickness, combination and glandular breast tissue on MGD were studied. As glandular g and X-ray tube voltage increased, the breast dose increased too, and the increase of breast phantom thickness led to the decrease of MGD. The obtained results for MGD were consistent with the result of Boone et al. that was previously reported.
  
  
  CONCLUSIONS
  By comparing the results, we saw that W/Rh anode/filter combination is the best choice in breast mammography imaging because of the lowest delivered dose in comparison with W/Ag and Rh/Al. Moreover, breast thickness and g value have significant effects on MGD.
authors.affiliation: Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Lida
authors.initials: L
authors.lastname: Gholamkar
authors.affiliation: Physics Department, Hakim Sabzevari University, Sabzevar, Iran; International Center for Theoretical Physics (ICTP), Associate Federation Scheme, Medical Physics Field, Trieste, Italy.
authors.forename: Ali Asghar
authors.initials: AA
authors.lastname: Mowlavi
authors.affiliation: Radiation Application Research School, Nuclear Science and Technology Research Institute, Tehran, Iran.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Sadeghi
authors.affiliation: Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Mitra
authors.initials: M
authors.lastname: Athari
keywords: Breast phantom; Digital Mammography System; MCNP Code; Mean Glandular Dose