Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
권호 표지
DOI QR코드

DOI QR Code

Optimization of Energy Modulation Filter for Dual Energy CBCT Using Geant4 Monte-Carlo Simulation

  • Ju, Eun Bin (Department of Medical Science, Ewha Womans University) ;
  • Ahn, So Hyun (Department of Radiation Oncology, School of Medicine, Yonsei University) ;
  • Choi, Sang Gyu (Department of Radiation Oncology, School of Medicine, Dankook University) ;
  • Lee, Rena (Department of Biomedical Engineering, School of Medicine, Ewha Womans University)
  • Received : 2016.09.06
  • Accepted : 2016.09.23
  • Published : 2016.09.30
Download PDF
⟨ Previous Next ⟩

Abstract

Dual energy computed tomography (DECT) is used to classify two materials and quantify the mass density of each material in the human body. An energy modulation filter based DECT could acquire two images, which are generated by the low- and high-energy photon spectra, in one scan, with one tube and detector. In the case of DECT using the energy modulation filter, the filter should perform the optimization process for the type of materials and thicknesses for generating two photon spectra. In this study, Geant4 Monte-Carlo simulation toolkit was used to execute the optimization process for determining the property of the energy modulation filter. In the process, various materials used for the energy modulation filter are copper (Cu, $8.96g/cm^3$), niobium (Nb, $8.57g/cm^3$), stannum (Sn, $7.31g/cm^3$), gold (Au, $19.32g/cm^3$), and lead (Pb, $11.34g/cm^3$). The thickness of the modulation filter varied from 0.1 mm to 1.0 mm. To evaluate the overlap region of the low- and high-energy spectrum, Geant4 Monte-Carlo simulation is used. The variation of the photon flux and the mean energy of photon spectrum that passes through the energy modulation filter are evaluated. In the primary photon spectrum of 80 kVp, the optimal modulation filter is a 0.1 mm lead filter that can acquire the same mean energy of 140 kVp photon spectrum. The lead filter of 0.1 mm based dual energy CBCT is required to increase the tube current 4.37 times than the original tube current owing to the 77.1% attenuation in the filter.

Keywords

References

  1. Primak AN, Giraldo JCR, Liu X, et al: Improved dual energy material discrimination for dual source CT by means of additional spectral filtration. Med Phys 36(4): 1359-1369 (2009) https://doi.org/10.1118/1.3083567
  2. Guillaume L, et al: Extracting atomic numbers and electron densities from a dual source dual energy CT scanner: experiments and a simulation model. Radiotherapy and Oncology 100(3): 375-379 (2011) https://doi.org/10.1016/j.radonc.2011.08.029
  3. Johnson TRC: Dual energy CT: general principles. American Roentgen Ray Society 199:S3-S8 (2012) https://doi.org/10.2214/AJR.12.9116
  4. Petersilka M, Bruder H, Krauss B, Stierstorfer K, Flohr TG: Technical principles of dual source CT. Eur J Radiol 68(3): 362-368 (2008) https://doi.org/10.1016/j.ejrad.2008.08.013
  5. Altman A, Carmi R: A double-layer detector, dual-energy CT -principles, advantages and applications. Med Phys 36(6): 2750-2750 (2009)
  6. Saito M: Spectral optimization for measuring electron density by the dual energy computed tomography coupled with balanced filter method. Med Phys 36(8): 3631-3642 (2009) https://doi.org/10.1118/1.3157098
  7. Nasseri MM: Determination of tungsten target parameters for transmission X-ray tube: A simulation study using Geant4. Nuc Eng Technol 48: 795-798 (2016) https://doi.org/10.1016/j.net.2016.01.006
  8. Agostinelli S, Allison J, Amako KA, et al: GEANT4-a simulation toolkit. Nuclear Instruments and Methods in Physics Research A 506(3):250-303 (2003) https://doi.org/10.1016/S0168-9002(03)01368-8
  9. Guthoff M, et al: Geant4 simulation of a filtered X-ray source for radiation damage studies. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 675: 118-122 (2012)
  10. Poludniowski G, et al: SpekCalc: a program to calculate photon spectra from tungsten anode X-ray tubes. Phys Med Bio 54(19): N433 (2009) https://doi.org/10.1088/0031-9155/54/19/N01
  11. Magdalena B, et al: Tissue segmentation in Monte Carlo treatment planning: a simulation study using dual-energy CT images. Radiotherapy and Oncology 86(1): 93-98 (2008) https://doi.org/10.1016/j.radonc.2007.11.008
  12. Danad I, Fayad ZA, Willemink MJ, Min JK: New applications of cardiac computed tomography: dual-energy, spectral, and molecular CT imaging. Cardiovascular Imaging 8(6):710-723 (2015)
  13. Johnson T: Dual Energy CT in Clinical Practice. Springer Science & Business Media (2011), pp. 3-8