Radiological Physics and Technology

, Volume 5, Issue 2, pp 248–269 | Cite as

Reconsideration of the Iwasaki–Waggener iterative perturbation method for reconstructing high-energy X-ray spectra

  • Akira Iwasaki
  • Shigenobu Kimura
  • Kohji Sutoh
  • Kazuo Kamimura
  • Makoto Sasamori
  • Morio Seino
  • Fumio Komai
  • Singo Terashima
  • Mamoru Kubota
  • Yuichiro Narita
  • Yoichiro Hosokawa
  • Masanori Miyazawa
Article
  • 189 Downloads

Abstract

We have reviewed applicable ranges for attenuating media and off-axis distances regarding the high-energy X-ray spectra reconstructed via the Iwasaki–Waggener iterative perturbation method for 4–20 MV X-ray beams. Sets of in-air relative transmission data used for reconstruction of spectra were calculated for low- and high-Z attenuators (acrylic and lead, respectively) by use of a functional spectral formula. More accurate sets of spectra could be reconstructed by dividing the off-axis distances of R = 0–20 cm into two series of R = 0–10 cm and R = 10–20 cm, and by taking into account the radiation attenuation and scatter in the buildup cap of the dosimeter. We also incorporated in the reconstructed spectra an adjustment factor (fadjust ≈ 1) that is determined by the attenuating medium, the acceleration voltage, and the set of off-axis distances. This resulted in calculated in-air relative transmission data to within ±2 % deviation for the low-Z attenuators water, acrylic, and aluminum (Al) with 0–50 cm thicknesses and R = 0–20 cm; data to within ±3 % deviation were obtained for high-Z attenuators such as iron (Fe), copper (Cu), silver (Ag), tungsten (W), platinum (Pt), gold (Au), lead (Pb), thorium (Th), and uranium (U) having thicknesses of 0–10 cm and R = 0–20 cm. By taking into account the radiation attenuation and scatter in the buildup cap, we could analyze the in-air chamber response along a line perpendicular to the isocenter axis.

Keywords

High-energy X-ray spectra Discrete X-ray spectra Iterative perturbation technique Transmission analysis Buildup cap In-air chamber response 

References

  1. 1.
    Mackie TR, Reckwerdt P, Papanikolaou N. 3-D photon beam dose algorithms. In: Purdy JA, Emami B, editors. 3-D radiation treatment planning and conformal therapy. Madison: Medical Physics Publishing Corporation; 1995.Google Scholar
  2. 2.
    Mackie TR, Reckwerdt P, McNutt T, Gehring M, Sanders C. Photon beam dose computations. In: Mackie TR, Palta JR, editors. Teletherapy: present and future. Madison: Advanced Medical Publishing; 1996.Google Scholar
  3. 3.
    Iwasaki A, Kimura S, Sutoh K, Kamimura K, Sasamori M, Komai F, Seino M, Terashima S, Kubota M, Hirota J, Hosokawa Y. A convolution/superposition method using primary and scatter dose kernels formed for energy bins of X-ray spectra reconstructed as a function of off-axis distance: a theoretical study on 10-MV X-ray dose calculations in thorax-like phantoms. Radiol Phys Technol. 2011;4:203–15.PubMedCrossRefGoogle Scholar
  4. 4.
    Kimura S, Sutoh K, Kamimura K, Iwasaki A, Sasamori M, Komai F, Seino M, Terashima S, Kubota M, Hirota J, Hosokawa Y. A convolution/superposition method using primary and scatter dose kernels formed for energy bins of X-ray spectra reconstructed as a function of off-axis distance: comparison of calculated and measured 10-MV X-ray doses in thorax-like phantoms. Radiol Phys Technol. 2011;4:216–24.PubMedCrossRefGoogle Scholar
  5. 5.
    Iwasaki A, Matsutani H, Kubota M, Fujimori A, Suzaki K, Abe Y. A practical method for estimating high-energy x-ray spectra using the iterative perturbation principle proposed by Waggener. Radiat Phys Chem. 2003;67:81–91.CrossRefGoogle Scholar
  6. 6.
    Iwasaki A, Kubota M, Hirota J, Fujimori A, Suzaki K, Aoki M, Abe Y. Characteristic features of a high-energy x-ray spectra estimation method based on the Waggener iterative perturbation principle. Med Phys. 2006;33:4056–63.PubMedCrossRefGoogle Scholar
  7. 7.
    Waggener RG, Blough MM, Terry JA, Chen D, Lee NE, Zhang S, McDavid WD. X-ray spectra estimation using attenuation measurements from 25 kVp to 18 MV. Med Phys. 1999;26:1269–78.PubMedCrossRefGoogle Scholar
  8. 8.
    Ulmer W, Pyyry J, Kaissl W. A 3D photon superposition/convolution algorithm and its foundation on results of Monte Carlo calculations. Phys Med Biol. 2005;50:1767–90.PubMedCrossRefGoogle Scholar
  9. 9.
    Loevinger R. A formalism for calculation of absorbed dose to a medium from photon and electron beams. Med Phys. 1981;8:1–12.PubMedCrossRefGoogle Scholar
  10. 10.
    Japan Society of Medical Physics. Standard Dosimetry of absorbed dose in external beam radiotherapy (Standard Dosimetry 01). Tokyo: Tsusho-Sangyo-Kenkyu-Sha; 2006.Google Scholar
  11. 11.
    Hubbell JH. Photon mass attenuation and energy-absorption coefficients from 1 keV to 20 MeV. Int J Appl Radiat Isot. 1982;33:1269–90.CrossRefGoogle Scholar

Copyright information

© Japanese Society of Radiological Technology and Japan Society of Medical Physics 2012

Authors and Affiliations

  • Akira Iwasaki
    • 1
  • Shigenobu Kimura
    • 2
  • Kohji Sutoh
    • 2
  • Kazuo Kamimura
    • 2
  • Makoto Sasamori
    • 3
  • Morio Seino
    • 4
  • Fumio Komai
    • 4
  • Singo Terashima
    • 6
  • Mamoru Kubota
    • 6
  • Yuichiro Narita
    • 5
  • Yoichiro Hosokawa
    • 6
  • Masanori Miyazawa
    • 7
  1. 1.HirosakiJapan
  2. 2.Department of RadiologyAomori City HospitalAomoriJapan
  3. 3.Department of RadiologyMisawa City HospitalMisawaJapan
  4. 4.Department of RadiologyHirosaki University HospitalHirosakiJapan
  5. 5.Graduate School of Medicine and School of MedicineHirosaki UniversityHirosakiJapan
  6. 6.Graduate School of Health SciencesHirosaki UniversityHirosakiJapan
  7. 7.Technology of Radiotherapy CorporationTokyoJapan

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