Physical Properties of Ethyl Methacrylate as a Bolus in Radiotherapy

Document Type: Original Paper

Authors

1 Radiotherapy Department of Pars Hospital, Tehran, Iran.

2 Medical Physics Department, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

Abstract

Introduction
Bolus is a soft and resilient material which is used for increasing skin dose or to even out the irregular patient contour. The main property of various materials used presently as bolus is the water-equivalent electron density. Ethyl methacrylate is used as a soft-liner in dentistry and its physical and chemical properties are proved to be nontoxic for human body. The goal of this study was to assess the feasibility of using this material as bolus in radiotherapy and also evaluating some parameters such as mass, electron densities, and transmission factors.
Materials and Methods
Computed tomography data from the sample material were acquired to assess mass and electron densities with various techniques (mA and kVp). Circular ROIs were delineated on CT DICOM images and densities were calculated using CT numbers. Transmission factors were calculated for 6 and 18 MV.
Results
Evaluation of our results are evident that showed that mass and electron densities of ethyl methacrylate are similar to those of water and soft tissue. Furthermore, transmission factors are close to those of water.
Conclusion
According to the results of this study and other properties such as flexibility and harmlessness, it seems that ethyl methacrylate is a suitable material to be used as bolus in radiotherapy.

Keywords

Main Subjects


  1. Podgorask EB. Radiation oncology physics: A handbook for teachers and students. 2nd ed. Vienna: International Atomic Energy Agency; 2005.
  2. Hsu SH, Roberson PL, Chen Y, Marsh RB, Pierce LJ, Moran JM. Assessment of skin dose for breast chest wall radiotherapy as a function of bolus material. Phys Med Biol. 2008;53(10):2593-606.
  3. Perkins GH, McNeese MD, Antolak JA, Buchholz TA, Strom EA, Hogstrom KR. A custom three-dimensional electron bolus technique for optimization of post mastectomy irradiation.  Int J Radiation oncology Biol Phys. 2001;51(4):1142-51.
  4. Cooney T, Irani F, Stalnecker A. Johnston S. Development of a Novel Bolus Material for Radiation Therapy, [homepage on the Internet]. 2006 [cited 2012 Jul 21]. Available from: http://bme227.pratt.duke.edu/downloads/S06/Bolus_Proposal.pdf
  5. Lacoste-Ferré MH, Demont P, Dandurand J, Dantras E, Blandin M, Lacabanne  C. Thermo-mechanical Analysis of Dental Silicone Polymers. J Mater Sci. 2006; 41(22):7611-6.
  6. Hekimog C, Anil Lu. The Effect of Accelerated Ageing on the Mechanical Properties of Soft Denture Lining Materials. J Oral Rehabil. 1999;26(9):745–8.
  7. Battista JJ, Bronskill MJ. Compton scatter imaging of transverse sections: an overall appraisal and evaluation for radiotherapy planning. Phys Med Biol. 1981; 26(1):81-99.
  8. Heismann BJ, Leppert J, Stierstorfer K. Density and Atomic Number Measurements with Spectral X-ray Attenuation Method, J Appl Phys. 2003;94(3):2073-9.
  9. Al-Ghazi M. CT simulation: principles, equipments and image based treatment planning. In: Oral presentation. International Scientific Exchange Program, Bahrain 2007.
  10. Thomas SJ. Relative electron density calibration of CT scanners for radiotherapy treatment planning. Br J Radiol. 1999;72(860):781-6.
  11. Schneider U, Pedroni E, Lomax A.. The calibration of CT Hounsfield units for radiotherapy treatment planning. Phys Med Biol. 1996;41(1):111-24.
  12. Khan Faiz M. The physics of radiation therapy, 3rd ed, USA, Lippincott Williams & Wilkins, 2003 ,p. 159, 233. Dose Distribution and Scatter Analysis,Treatment PlanningII:Patient Data,Corrections and Set-up.
  13. JRT Associates Bolus Material. Available from: http://www.jrtassoc.com/rad_oncology/Bolus/2011