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A method to correct for spectral artifacts in optical-CT dosimetry.

Publication ,  Journal Article
Thomas, A; Pierquet, M; Jordan, K; Oldham, M
Published in: Phys Med Biol
June 7, 2011

The recent emergence of radiochromic dosimeters with low inherent light-scattering presents the possibility of fast 3D dosimetry using broad-beam optical computed tomography (optical-CT). Current broad beam scanners typically employ either a single or a planar array of light-emitting diodes (LED) for the light source. The spectrum of light from LED sources is polychromatic and this, in combination with the non-uniform spectral absorption of the dosimeter, can introduce spectral artifacts arising from preferential absorption of photons at the peak absorption wavelengths in the dosimeter. Spectral artifacts can lead to large errors in the reconstructed attenuation coefficients, and hence dose measurement. This work presents an analytic method for correcting for spectral artifacts which can be applied if the spectral characteristics of the light source, absorbing dosimeter, and imaging detector are known or can be measured. The method is implemented here for a PRESAGE® dosimeter scanned with the DLOS telecentric scanner (Duke Large field-of-view Optical-CT Scanner). Emission and absorption profiles were measured with a commercial spectrometer and spectrophotometer, respectively. Simulations are presented that show spectral changes can introduce errors of 8% for moderately attenuating samples where spectral artifacts are less pronounced. The correction is evaluated by application to a 16 cm diameter PRESAGE® cylindrical dosimeter irradiated along the axis with two partially overlapping 6 × 6 cm fields of different doses. The resulting stepped dose distribution facilitates evaluation of the correction as each step had different spectral contributions. The spectral artifact correction was found to accurately correct the reconstructed coefficients to within ∼1.5%, improved from ∼7.5%, for normalized dose distributions. In conclusion, for situations where spectral artifacts cannot be removed by physical filters, the method shown here is an effective correction. Physical filters may be less viable if they introduce strong sensitivity to Schlieren bands in the dosimeters.

Duke Scholars

Published In

Phys Med Biol

DOI

EISSN

1361-6560

Publication Date

June 7, 2011

Volume

56

Issue

11

Start / End Page

3403 / 3416

Location

England

Related Subject Headings

  • Uncertainty
  • Tomography, X-Ray Computed
  • Spectrum Analysis
  • Radiometry
  • Optical Phenomena
  • Nuclear Medicine & Medical Imaging
  • Models, Theoretical
  • Artifacts
  • Algorithms
  • 5105 Medical and biological physics
 

Citation

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Thomas, A., Pierquet, M., Jordan, K., & Oldham, M. (2011). A method to correct for spectral artifacts in optical-CT dosimetry. Phys Med Biol, 56(11), 3403–3416. https://doi.org/10.1088/0031-9155/56/11/014
Thomas, Andrew, Michael Pierquet, Kevin Jordan, and Mark Oldham. “A method to correct for spectral artifacts in optical-CT dosimetry.Phys Med Biol 56, no. 11 (June 7, 2011): 3403–16. https://doi.org/10.1088/0031-9155/56/11/014.
Thomas A, Pierquet M, Jordan K, Oldham M. A method to correct for spectral artifacts in optical-CT dosimetry. Phys Med Biol. 2011 Jun 7;56(11):3403–16.
Thomas, Andrew, et al. “A method to correct for spectral artifacts in optical-CT dosimetry.Phys Med Biol, vol. 56, no. 11, June 2011, pp. 3403–16. Pubmed, doi:10.1088/0031-9155/56/11/014.
Thomas A, Pierquet M, Jordan K, Oldham M. A method to correct for spectral artifacts in optical-CT dosimetry. Phys Med Biol. 2011 Jun 7;56(11):3403–3416.
Journal cover image

Published In

Phys Med Biol

DOI

EISSN

1361-6560

Publication Date

June 7, 2011

Volume

56

Issue

11

Start / End Page

3403 / 3416

Location

England

Related Subject Headings

  • Uncertainty
  • Tomography, X-Ray Computed
  • Spectrum Analysis
  • Radiometry
  • Optical Phenomena
  • Nuclear Medicine & Medical Imaging
  • Models, Theoretical
  • Artifacts
  • Algorithms
  • 5105 Medical and biological physics