Radiation Physics

PV QA 3 - Poster Viewing Q&A 3

TU_3_3141 - Feasibility Study for a Measurement of Patient Dose Via N-V Center of Diamond During Radiation Therapy

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

Feasibility Study for a Measurement of Patient Dose Via N-V Center of Diamond During Radiation Therapy
S. Y. Moon1, S. Y. Lee2, and D. Shin3; 1Korea University, Seoul, Korea, Republic of (South), 2Kaiser Permanente Anaheim Medical Center, Anaheim, CA, 3Proton Therapy Center, National Cancer Center, Goyang-si, Gyeonggi-do, Korea, Republic of (South)

Purpose/Objective(s): It is possible to prevent radiation accidents by an overdose or under dose if patient dose was checked during radiotherapy. Also an accuracy of the radiotherapy has been improved with it. A molecular structure of diamond is changed as exposed to radiation and a photoluminescence is emitted as the diamond returns to its original state. Based on this light, we checked whether possible to measure a radiation dose via the diamond.

Materials/Methods: When a diamond was irradiated by radiation, point defects called nitrogen-vacancy center (N-V center) were formed in it and the molecular structure was changed. The N-V centers emitted photoluminescence appearing bright red light and then the diamond returned to the original state. A clear, polished fiber guiding the light was attached to the end of diamond and connected to a photomultiplier tube (PMT). When the 6MV photon beam was turned on using a linear accelerator, the irradiated diamond formed the N-V center and emitted photoluminescence, with the emitted light guided to the PMT through the clear fiber. Light signals guided to the PMT were amplified and transferred to a printed circuit board (PCB), which transformed the amplified light signal into an electrical signal. This signal was subsequently transmitted to the data acquisition system and digitized at a sampling rate of 100 per second and a frequency of 1 kHz.

Results: According to the field size, the respective signal was 230, 370 and 500 under the 3x3, 6x6 and 10x10. The noise signal by the useless light of the clear fiber was 180, 320 and 450, respectively. The noise was removed and the valuable signal by the diamond was 50 in all cases. The consistent light was emitted from the diamond under the radiation exposure regardless of the field size and the amount of signal increased with increasing the radiation dose.

Conclusion: The irradiated diamond by the radiation formed the N-V centers and emitted the photoluminescence with high temporal stability. Through the amount of the accumulated light for the treatment time, the radiation dose was checked. The diamond has attracted attention as a next generation dosimetry material because of its properties as a radiation dosimeter.

Author Disclosure: S. Moon: None. S. Lee: None.

Sun Young Moon, MS

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