Date

2021-9-09

Author

Ege, Ahmet

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The mean absorbed radiation dosage by the breast glandular tissue in mammography is called the "Average Glandular Dose" (AGD). The latest ICRP (International Comission on Radiological Protection) publication on the use of DRLs (Diagnostic Reference Level) in medical imaging recommends the AGD as DRL values. Diagnostic mammogram data about doses were collected for 253 healthy women between 40 to 64 years of ages with 1012 screenings completed in one calendar year in a medical institution in Turkey. Local DRL values for a standard two-projection mammogram with CC (Cranioncaudal) and MLO (Mediolateral oblique) projections are determined for different breast thickness as it is established and recommended by ICRP 135.AGD values were obtained by multiplying the in-air exposure on theentrance surface by the absorbed dose conversion factor using the coefficientsfound by Monte Carlo simulations with three different methods. Robson AGD,2ABD and the Wu-Boone radiation dose calculation parametric methods wereapplied for each patient data. Excel was used to calculate the AGDs by usingtube voltage (kV), half- value thickness (HVL), compressed breast thickness(CBT) and breast composition. For some breast thicknesses, the quartile valuesof AGDs were computed. Utilization of these results in the calculation of thefirst local DRLs of Turkey and therefore, we compared them with national DRLs for each 10-mm CBT in mammography. Nonparametric statistical methods are used to determine the significance with respect to two other methods, age and CBT differences. As a result, 2ABD values were significantly higher than Robson AGD and Wu-Boone, whereas Robson AGD yielded significantly higher values than Wu-Boone. Moreover, radiation dose comparison of Robson AGD (mGy) (75th) between local and national values for the age ranges 40-49 and 50-64 shows that the local values are higher than the national values.

Subject Keywords

Mammography, Radiation Dose Calculation Methods, Average Glandular Dose, Local Diagnostic Reference Level

URI

https://hdl.handle.net/11511/93201

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Graduate School of Natural and Applied Sciences, Thesis