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

1.3 Specific Aims 
The research performed for this work consisted of three specific aims, each dealing with 
a separate aspect of using plastic scintillation detectors for in vivo dosimetry.
The first aim was to fully characterize the unexpected temperature dependence of 
plastic scintillation detectors and provide accurate methods to correct for it during in vivo 
dosimetry. The effect of temperature on measured dose, total light output, and spectral 
shape for two common plastic scintillating fibers and their optical train components was 
quantified. This characterization was used to suggest a correction method and evaluate its 
efficacy.
The second aim was to carry out in vivo measurements of the rectal wall dose for 
a small group of prostate cancer patients undergoing intensity modulated radiation 
therapy, a form of external beam radiation using photons to deliver dose. The data 
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generated during this study was used to evaluate the performance of plastic scintillation 
detectors as in vivo detectors in terms of accuracy, precision, and practicality. 
The final aim was to characterize the response of plastic scintillation detectors 
used for absolute entrance dosimetry in proton beams. Specifically, the effects of 
ionization quenching and Cerenkov light contamination were quantified and the necessity 
of correcting for each effect was evaluated, as well as methods to implement corrections. 
 
1.4 Organization 
The remaining five chapters of this work consist of one chapter of background 
information helpful in understanding the presented research, three addressing the specific 
aims listed in the previous section, and a final chapter summarizing the findings and 
discussing future directions of the presented research. 
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