In Vivo Dosimetry using Plastic Scintillation Detectors for External Beam Radiation Therapy

ACKNOWLEDGEMENTS 
First and foremost I’d like to acknowledge and thank Dr. Beddar for his mentorship, 
support and guidance without whom this work would not have been possible. I’d like to 
acknowledge all the members of my committees, past and present: Dr. Mirkovic, Dr. 
Zhu, Dr. Sahoo, Dr. Johnson, Dr. Hess, Dr. Wendt, Dr. Briere, and particularly Dr. Lee 
and Dr. Kudchadker who have been instrumental in the course of this research and in my 
education. Thanks to current and former lab members: Francois Therriault-Proulx, David 
Klein, Daniel Robertson, Lelei Wang, Clint Zeringue, Slade Klawikowski, Beckett Hui, 
Thomas Henry, and Gustavo Kertzscher. Thanks especially to Francois and David who 
served as mentors to me when I first joined. Thanks to the many people who have helped 
along the way. There are too many to name, and I owe each a debt of gratitude. Finally, a 
special thanks to the members of the American Legion Auxiliary for their support 
through the American Legion Auxiliary Fellowship in Cancer Research. 
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IN VIVO DOSIMETRY USING PLASTIC SCINTILLATION DETECTORS FOR 
EXTERNAL BEAM RADIATION THERAPY 
Landon Scott Wootton, B.S. 
Supervisory Professor: Sam Beddar, Ph.D. 
In vivo dosimetry, the direct measurement of dose delivered to patients during 
radiation therapy, has significant potential in ensuring safe and effective treatment in 
radiation therapy. It can serve as point-of-delivery, patient specific quality assurance and 
direct verification of treatment. Despite evidence that in vivo dosimetry can detect errors 
in patient treatment that would otherwise go undetected, it is not commonly practiced. 
This is due in part to a lack of available detectors ideally suited to perform in vivo 
dosimetry. Plastic scintillation detectors (PSDs) possess a number of dosimetric 
characteristics advantageous for in vivo dosimetry including water equivalence, real-time 
capability, small size, and energy independence. However, PSDs have not been used for 
in vivo dosimetry of external beam radiation therapy to date. The overall purpose of this 
work is to apply PSDs to in vivo dosimetry of external beam radiation therapy, and 
demonstrate the utility and practicality of performing in vivo dosimetry with PSDs. 
Three avenues of research were pursued in accordance with this purpose. First, 
the temperature dependence of PSDs was characterized. Prior to this work, PSDs were 
understood to be temperature independent detectors. However responses of PSDs 
constructed with BCF-60 and BCF-12, two common scintillating fibers, were 
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demonstrated to decrease by 0.5% and 0.1% per °C increase relative to 22 °C, 
respectively. The spectral distribution of light was observed to change with temperature 
as well. This resulted in a non-negligible error in measured dose at human body 
temperature, requiring a temperature-specific correction factor.
Next, PSDs were used for in vivo dosimetry of the rectal wall in five patients 
undergoing intensity modulated radiation therapy for prostate cancer. This was done as