Korean J Med Phys.  2010 Jun;21(2):192-200.

Monte Carlo Study Using GEANT4 of Cyberknife Stereotactic Radiosurgery System

Affiliations
  • 1Department of Biomedical Engineering, School of Medicine, The Catholic University of Korea, Seoul, Korea. suhsanta@catholic.ac.kr
  • 2Research Institute of Biomedical Engineering, The Catholic University of Korea, Seoul, Korea.
  • 3Department of Radiation Oncology, St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea.
  • 4Department of Physics, Sungkyunkwan University, Seoul, Korea.
  • 5Seoul Wooridul Spine Hospital, Cyberknife Clinic, Seoul, Korea.
  • 6Department of Radiologic Technology, Choonhae College of Health Sciences, Ulsan, Korea.
  • 7Department of Radiologic Technology, Shingu University, Seongnam, Korea.

Abstract

Cyberknife with small field size is more difficult and complex for dosimetry compared with conventional radiotherapy due to electronic disequilibrium, steep dose gradients and spectrum change of photons and electrons. The purpose of this study demonstrate the usefulness of Geant4 as verification tool of measurement dose for delivering accurate dose by comparing measurement data using the diode detector with results by Geant4 simulation. The development of Monte Carlo Model for Cyberknife was done through the two-step process. In the first step, the treatment head was simulated and Bremsstrahlung spectrum was calculated. Secondly, percent depth dose (PDD) was calculated for six cones with different size, i.e., 5 mm, 10 mm, 20 mm, 30 mm, 50 mm and 60 mm in the model of water phantom. The relative output factor was calculated about 12 fields from 5 mm to 60 mm and then it compared with measurement data by the diode detector. The beam profiles and depth profiles were calculated about different six cones and about each depth of 1.5 cm, 10 cm and 20 cm, respectively. The results about PDD were shown the error the less than 2% which means acceptable in clinical setting. For comparison of relative output factors, the difference was less than 3% in the cones lager than 7.5 mm. However, there was the difference of 6.91% in the 5 mm cone. Although beam profiles were shown the difference less than 2% in the cones larger than 20 mm, there was the error less than 3.5% in the cones smaller than 20 mm. From results, we could demonstrate the usefulness of Geant4 as dose verification tool.

Keyword

Cyberknife; Small field; GEANT4; Electron disequilibrium

MeSH Terms

Electronics
Electrons
Head
Photons
Radiosurgery
Resin Cements
Water
Resin Cements
Water
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