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Development of Real Time Thermoplastic Mask Compression Force Monitoring System Using Force Sensing Register (FSR) Sensor

T Kim1*, T Suh2, S Kim3, D Shin2, D Shin1, (1) Proton Therapy Center, National Cancer Center, Goyang-si, Gyeonggi-do, KR, (2) Catholic Univ Medical College, Seoul, ,KR, (3) Virginia Commonwealth University, Richmond, VA,


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: this study, we developed and evaluated a system that could monitor compression force inside a thermoplastic mask in real time. The system also provides a warning to the user when there is a possibility of improper immobilization.

Methods: real-time thermoplastic mask compression force (TMCF) monitoring system consists of a force sensing register (FSR) sensor, a signal transport device, control PC and an in-house software program The system provided stable pressure readings in all of 10 trials sensor unit reproducibility test. The largest SD of 10 mean values was about 36 gf/cm²(~2.4 % of full scale range). For 5 repeated mask setups on the phantom, the compression force variation of the mask was less than 39 gf/cm²(2.6 % of full scale range).

Results: A thermoplastic mask setup reproducibility study with six volunteers was performed to evaluate the feasibility of the proposed monitoring system. We were successful in making masks together with the monitoring system connected and demonstrated feasible utilization of the system. Various compression force variations were observed according to the location of the sensor (among forehead, both cheekbones, and chin) and each volunteers. In case of forehead and both cheekbones, the compression force was generally stable in all volunteers. However, in the chin case, the compression force was formed lower than other sites and even dropped down to zero, indicating loss of immobilization power.

Conclusion: developed monitoring system could provide information that if the appropriate compression force was maintained during the treatment. When the compression force is too weak or close to zero, the GUI of monitoring system gives a warning signal to the user. With the capability of providing a warning signal before actual variation accrued, it could improve the setup accuracy of patient with a thermoplastic mask.




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