TU‐C‐108‐12: A New Technology for Fast Two‐Dimensional Detection of Proton Therapy Beams

• Published in: Medical Physics 2013-06, Vol.40 (6), p.433-433
• Main Authors: Hollebeek, R, Newcomer, M, Mayers, G, Delgado, B, Shukla, G, Maughan, R, Dolney, D
• Format: Article
• Language: English
• Subjects: Amplifiers; Dosimetry; Drug delivery; Electronic structure; Error analysis; Ionization chambers; Particle beam detectors; Proton therapy; Quality assurance; Spatial resolution
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.4815376

Purpose: The authors have developed a novel detector technology for proton therapy dosimetrywith fine spatial and time resolution. New dosimetry technology tailored to proton therapy willreduce the uncertainties in beam characteristics, assist in the development of new and moreadvanced therapy‐supporting technologies, facilitate more rapid delivery and commissioning ofnew particle therapy facilities, and allow more comprehensive Quality Assurance measurements. Methods: The Micromesh Gaseous Structure, or Micromegas, is a technology developed for highcount‐rate applications in high‐energy physics experiments. Presented here are tests using aMicromegas chamber and specially designed amplifiers and readout electronics adapted to therequirements of the proton therapy environment and providing both excellent time and high spa‐tial resolution. Several iterations of Micromegas prototypes have been fabricated and assembled.Data has been collected with these prototypes in proton therapy beams to demonstrate the capa‐bilities and limitations of this new technology. Results: The digitized ionization signal from the chamber is found to be reproducible to betterthan 0.8%. Spatial resolution is determined to be 1.1 mm (1σ) at 1 ms time resolution. We resolvethe range modulator wheel rotational frequency and the thicknesses of its segments and showthat this information can be quickly measured owing to the high time resolution of the system. Oursystem resolves the high dose rate within a proton Bragg peak and measurements agree with aparallel‐plate ionization chamber (PTW 34070) to better than 1%. Conclusion: We have demonstrated an adaptation of Micromegas as a beam monitor for protontherapy, and the data indicates that Micromegas holds promise as a high spatial and time resolu‐tion measurement device. Systems of this type will be useful in future treatment methods involvingbeams that change rapidly in time and spatial position.