Validation of Isodose Curves for AIRO Mobile CT, P-32 Pure-Beta and I-131 Mixed Beta/Gamma Detection Utilizing Nano-Fiber Optic Detector
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Project 1: Validation of Isodose Curves for AIRO Mobile CT
Purpose: Validate isodose curves provided by the manufacturer for the Airo Mobile CT to determine if, indeed, it is safe for those who are operating the machine.
Materials and Methods: To determine the maximum number of scans per year allowed, hospitals rely on the data provided by the manufacturer. It is not common practice to verify the data provided for CT scanners. To validate the information provided by the manufacturer, the same CT settings were utilized for testing. The manufacturer settings were 120 kV, 100 mA and 1.92 sec and a 32 cm body CTDI phantom was used to generate scatter patterns. Replicating these conditions, two ion chambers were used to collect measurements of scattered radiation at different distances around the MobileCT gantry.
Results: Following the manufacturer settings, the average percent difference between the manufacturer data and the data collected in this experiment was 24.16 ± 15%.
Conclusions: The results provided information that confirmed the validity of the data provided by the manufacturer. Through this verification, it was shown that the scattered air kerma determined through experimentation was comparable to the data provided by the manufacturer.
Project 2: P-32 pure-beta detection utilizing nano-fiber optic detector
Purpose: Determine if the nano-fiber optic detector is capable of detecting pure β emissions by placing it in contact with P-32 in liquid solution.
Materials and Methods: The P-32 was placed into a vial with 2 mL of stabilizing solution. The vial was placed in a lead pig that was modified with a 1 mm opening on the lid for the nano-FOD to be inserted through. Measurements of the nano-FOD’s response to pure beta emissions were collected by submerging the nano-FOD into a vial containing 76.2 mCi of liquid P-32 and evaluating the voltage output that was produced. For P-32, this was done over a 45-day period to determine if the nano-FOD was able to accurately measure activity over time. From the data collected, the net signal and signal-to-noise ratio (SNR) were calculated and compared to the P-32 concentration, which showed a linear correlation when plotted.
Results: The nano-FOD was able to demonstrate a noticeable response when inserted into the P-32 solution. The data from the net signal allowed for the determination of the experimental half-life which was 13.46 ± 0.87 days. When compared to the published half-life of P-32, which is 14.29 days, the percent difference between the experimental and published half-life was 5.8%.
Conclusions: The results from this data collection provide confirmation that the nano-FOD device can be utilized as a real-time β detector. Using Monte Carlo simulations, the signals measured with the nano-FOD have been calibrated to radiation exposure, proving the nano-FODs ability to be utilized as a novel β detector.
Project 3: I-131 mixed-beta and gamma detection utilizing nano-fiber optic detector
Purpose: Determine if the nano-fiber optic detector is capable of accurately detecting mixed β and γ radiation by placing it in contact with I-131.
Materials and Methods: The I-131 was placed into a vial with 2 mL of stabilizing solution. The vial was placed in a lead pig that was modified with two openings on the lid for each of the nano-FODs to be inserted through. The first opening was used to insert directly into the I-131 solution to be exposed to both the β and γ emissions. The second opening led the nano-FOD into a Lucite sheath that blocks all β emissions, so that only the γ component was detected by the nano-FOD. Measurements of the nano-FOD’s response to mixed β and γ emissions were collected by submerging the nano-FOD into the vial containing 105 mCi of liquid I-131 and evaluating the voltage output that was produced. For I-131, this was done over a 20-day period to determine if the nano-FOD was able to measure activity over time for both the mixed signal and the gamma signal.
Results: The signal produced by the nano-FOD from being exposed to the mixed beta and gamma emissions of I-131 shows the nano-FODs capability of detecting radiation in mixed fields. The net signal over time provided an experimental half-life comparable to that of the published half-life of I-131.
Conclusions: The nano-FOD is capable of functioning in a mixed field. The post-processing data analysis for this nano-FOD needs modification and will provide insight into the future of utilizing the nano-FOD in mixed fields.
Smiley, Brianna Rochelle (2019). Validation of Isodose Curves for AIRO Mobile CT, P-32 Pure-Beta and I-131 Mixed Beta/Gamma Detection Utilizing Nano-Fiber Optic Detector. Master's thesis, Duke University. Retrieved from https://hdl.handle.net/10161/18864.
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