Author/Authors :
Sadeghi Mahdi نويسنده Students Research Committee, School of dentistry, Tabriz University of Medical Sciences, Tabriz, Iran , Gholamkar Lida نويسنده Department of Medical Radiation Engineering, Science and
Research Branch, Islamic Azad University, Tehran,
Iran , Mowlavi Ali Asghar نويسنده Physics Department, Hakim Sabzevari University, Sabzevar,
Iran , Athari Mitra نويسنده Department of Medical Radiation Engineering, Science and
Research Branch, Islamic Azad University, Tehran,
Iran
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. Objectives 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. Materials and 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. Conclusion 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.
