Semester of Graduation

Fall 2023

Degree

Master of Science (MS)

Department

Physics & Astronomy

Document Type

Thesis

Abstract

Breast cancer is the most common type of cancer among women in the United States. It is also the second leading cause of death by cancer among women in the United States. Early detection is key to preventing fatalities. There are over 39 million mammography screening procedures performed yearly [3]. We know that exposure to radiation, including in routine mammography, may induce secondary cancers [4]. Thus, it is important to be able to accurately estimate the dose delivered to a patient during breast cancer screening. The dose delivered to a patient is regulated in the US and in many other countries worldwide.

Currently accepted dose estimation methods are approximate. They assume a 50/50 homogeneous mixture of adipose and fibroglandular (FG) tissue.

We aim to provide a more personalized range of possible normalized glandular dose (DgN) to a given patient for one mammogram image and a glandular fraction image thereof. We utilize the previous work of Smith and Dey, et al. in estimating glandular fraction [8]. In the first aim, we used Monte Carlo simulation on a breast model to investigate the dose range delivered to a breast model of varying thickness and glandular fraction with FG tissue concentrated close to the source, centrally, or far away from the source.

The DgN varies by up to a factor of 3 based on location of FG tissue with no visually detectable change in projection images. Secondly using simulated projections and glandular fraction images, the Siddon ray tracing algorithm was used to find backprojected volumes corresponding to minimum and maximum DgNs, keeping the projection and glandular fraction unchanged. We show analytical dose to the backprojected object can be minimized or maximized by adjusting the placement of FG tissue within the object. Lastly, an estimate is performed in with scatter by a Monte Carlo simulation. The Monte Carlo dose is normalized by the air kerma, providing a DgN value for each backprojected volume. Finally, the same technique is applied for four clinical cases.

Date

9-27-2023

Committee Chair

Dey, Joyoni

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