Date Approved

7-2020

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Diagnostic & Treatment Sciences

First Advisor

Kristen Vu

Academic Year

2019/2020

Abstract

Planning technique and bolus choice are important aspects in planning chest wall irradiation (CWI). Many previous studies have tested various combinations of photon energies, electron energies, bolus types and sizes, air gaps sizes, and treatment methods. This study aims to assess the effect of smaller, clinically relevant air gap sizes on specific chest wall treatments using a variety of common bolus types. Due to the Covid-19 pandemic, no data was able to be collected and was instead fabricated by the researcher. Four different treatment plans were created on a phantom patient using various energies of photons (6MV and 10MV) and electrons (9MeV and 12MeV) using the version 15 eclipse planning system. All treatment plans were tested with five different types of bolus: superflab, elastogel, steel brass, custom aquaplast, and wet towel. Air gaps of sizes 0cm, 0.3cm, 0.5cm, 0.7cm, and 1cm were introduced between the bolus and phantom surface. Statistical analysis was performed as t-tests with a Bonferroni correction for multiple testing. P-value of significance is p=0.0125 and the only air gap of significance was 1cm (p=0.0029). Of the bolus types, steel brass and custom aquaplast displayed the largest doses while wet towel displayed the lowest doses. As the air gap size increased, the more significant the difference in dose to the chest wall. Small air gaps are not clinically detrimental to CWI’s, while larger air gaps starting at 1cm pose a significant difference. Steel brass and custom aquaplast are good choices of bolus when treating a chest wall for optimal coverage of the target.

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