Evaluation and analysis of entrance surface air kerma of the thyroid gland during breast cancer screening mammography

Abstract

Objective

To evaluate and analyze entrance surface air kerma (ESAK) of the thyroid during mammographies performed in a breast cancer screening program.

Methods

The ESAK was measured for the left and right lobes of the thyroid gland for 120 female subjects undergoing routine mammographic screenings. All measurements were single-handedly performed on the Hitachi Hologic LORAD M-IV^TM screen-film mammography system. Radiation dose measurements were made using optically stimulated luminescent dosimeters (OSLD) nanoDot™ taped appropriately to the skin overlying the right and left lobes of the thyroid gland. The standard technique of two craniocaudal (CC) views and two mediolateral oblique (MLO) views with appropriate compression was used during the screening.

Results

The average ESAK was (287 ​± ​102) μGy. The value of radiation dose to the thyroid was estimated as 71.17 ​μGy. Compresssed breast thichness (CBT) was found as key parameter influencing radiation dose to the thyroid gland during mammography. ESAK changed approximately two folds for the CBT range of 2–5 ​cm. Radiation dose to the thyroid gland was increased with higher body mass index (BMI).

Conculsions

A proper compression of the breast is crucial for the mammographic examination. In addition to applied exposure factors for examination, breast compression is the principal and influencing factor that affects various other parameters used during mammographic examinations, which in turn impact radiation dose to the thyroid gland.