Prog Med Phys.  2016 Mar;27(1):25-30. 10.14316/pmp.2016.27.1.25.

Measurement of Energy Parameters for Electron Gun Heater Currents and Output Dose Rate for Electron Beams from a Prototype Linac

• Lim H
• Lee M
• Kim MY
• Yi J
• Lee M
• Kang SK
• Rhee DJ
• Jeong DH

• KMID: 2161935
• DOI: http://doi.org/10.14316/pmp.2016.27.1.25

Abstract

The dosimetric characteristics were experimentally evaluated for electron beams from the prototype linac developed for radiotherapy units. This paper focuses on the electron beam output and energy variations as a function of electron gun heater current. The electron energy was derived from its mean and most probable energies measured by film dosimetry. The electron beam output at the maximum electron energy was measured with the plane parallel ionization chamber in water using TRS-398 dosimetry protocol. The mean energy and the most probable energy of the electron beam were 6.54~3.31 MeV and 5.94~2.80 MeV at electron gun current of 2.02~2.50 A respectively. The output dose rate for an electron beam of mean energy 6.54 MeV was 5.41 Gy/min ±1.5% at the reference depth in water.

Keyword

Electron linac; Gun heater current; Output measurement

MeSH Terms

Film Dosimetry
Radiotherapy
Water
Water

Figure

• 

  Fig. 1. Schematic description of experimental setup for film measurement.

• 

  Fig. 2. Experimental setup for depth dose and output measurement for electron beams from a prototype electron linac.

• 

  Fig. 3. Measured percentage depth dose curves for electron gun heater currents.

• 

  Fig. 4. Polynomial fitting for energy parameters with electron gun heater currents.

• 

  Fig. 5. Depth ionization curves for e-gun heater current of 2.02 A.

• 

  Fig. 6. Determined depth dose curves for e-gun heater current of 2.02 A.

• 

  Fig. 7. Relationship between nominal energy and R50 values in commercial linacs. The measured R50 values for gun heater currents were shown.

Reference

References

1. David IT, John BT. Backtothefuture: thehistoryanddevel-opmentoftheclinicallinearaccelerator.PhysMedBiol. 51:R343–R362. 2006.

2. www.kirams.re.kr/khima

3. Kim S, Kang SK, Rhee DJ, et al. :. MeasurementofElectron BeamOutputforthe PrototypeCompactLinac,Progressin MedicalPhysics. 26(1):1–5. 2015.

4. Yi J, Lee M, Lee M, et al. :. FabricationandHighpowerRF testofaC-bandStanding-waveAcceleratingStructurefor MedicalApplication,ICABU(InternationalConferenceonAccele-ratorsandBeamUtilizations)Proceeding. 134–134. 2015.

5. Scott EVB. AnIntroductiontoMassSpectrometry, Widner University, PA, USA. 1998.

6. TRS-277. AbsorbedDoseDeterminationinPhotonand ElectronBeams: AnInternationalCodeofPractice. International Atomic Energy Agency;Vienna: 1997.

7. Li A, Wen D, Chen , et al. :. Astudyofdosimetrycharacteristics ofGAFDM-1260radiochromicFilms,RadPhysChem. 57:103–113. 2000.

8. TRS-398. Absorbeddosedeterminationinexternalbeamra-diotherapy: aninternationalcodeofpracticefordosimetrybased onstandardsofabsorbeddosetowater. International Atomic Energy Agency;Vienna: 2000.

9. Zink K, Wulff J. MonteCarlocalculationsofbeamqualitycor-rectionfactors_ for electron dosimetry with a parallel-plate Roos chamber,PhysMedBiol. 53:1595–1607. 2008.