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Fast, high-resolution 3D dosimetry utilizing a novel optical-CT scanner incorporating tertiary telecentric collimation.

Publication ,  Journal Article
Sakhalkar, HS; Oldham, M
Published in: Med Phys
January 2008

This study introduces a charge coupled device (CCD) area detector based optical-computed tomography (optical-CT) scanner for comprehensive verification of radiation dose distributions recorded in nonscattering radiochromic dosimeters. Defining characteristics include: (i) a very fast scanning time of approximately 5 min to acquire a complete three-dimensional (3D) dataset, (ii) improved image formation through the use of custom telecentric optics, which ensures accurate projection images and minimizes artifacts from scattered and stray-light sources, and (iii) high resolution (potentially 50 microm) isotropic 3D dose readout. The performance of the CCD scanner for 3D dose readout was evaluated by comparison with independent 3D readout from the single laser beam OCTOPUS-scanner for the same PRESAGE dosimeters. The OCTOPUS scanner was considered the "gold standard" technique in light of prior studies demonstrating its accuracy. Additional comparisons were made against calculated dose distributions from the ECLIPSE treatment-planning system. Dose readout for the following treatments were investigated: (i) a single rectangular beam irradiation to investigate small field and very steep dose gradient dosimetry away from edge effects, (ii) a 2-field open beam parallel-opposed irradiation to investigate dosimetry along steep dose gradients, and (iii) a 7-field intensity modulated radiation therapy (IMRT) irradiation to investigate dosimetry for complex treatment delivery involving modulation of fluence and for dosimetry along moderate dose gradients. Dose profiles, dose-difference plots, and gamma maps were employed to evaluate quantitative estimates of agreement between independently measured and calculated dose distributions. Results indicated that dose readout from the CCD scanner was in agreement with independent gold-standard readout from the OCTOPUS-scanner as well as the calculated ECLIPSE dose distribution for all treatments, except in regions within a few millimeters of the edge of the dosimeter, where edge artifact is predominant. Agreement of line profiles was observed, even along steep dose gradients. Dose difference plots indicated that the CCD scanner dose readout differed from the OCTOPUS scanner readout and ECLIPSE calculations by approximately 10% along steep dose gradients and by approximately 5% along moderate dose gradients. Gamma maps (3% dose-difference and 3 mm distance-to-agreement acceptance criteria) revealed agreement, except for regions within 5 mm of the edge of the dosimeter where the edge artifact occurs. In summary, the data demonstrate feasibility of using the fast, high-resolution CCD scanner for comprehensive 3D dosimetry in all applications, except where dose readout is required close to the edges of the dosimeter. Further work is ongoing to reduce this artifact.

Duke Scholars

Published In

Med Phys

DOI

ISSN

0094-2405

Publication Date

January 2008

Volume

35

Issue

1

Start / End Page

101 / 111

Location

United States

Related Subject Headings

  • Tomography Scanners, X-Ray Computed
  • Time Factors
  • Radiotherapy, Intensity-Modulated
  • Radiation Dosage
  • Optics and Photonics
  • Nuclear Medicine & Medical Imaging
  • Imaging, Three-Dimensional
  • Artifacts
  • 5105 Medical and biological physics
  • 4003 Biomedical engineering
 

Citation

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ICMJE
MLA
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Sakhalkar, H. S., & Oldham, M. (2008). Fast, high-resolution 3D dosimetry utilizing a novel optical-CT scanner incorporating tertiary telecentric collimation. Med Phys, 35(1), 101–111. https://doi.org/10.1118/1.2804616
Sakhalkar, H. S., and M. Oldham. “Fast, high-resolution 3D dosimetry utilizing a novel optical-CT scanner incorporating tertiary telecentric collimation.Med Phys 35, no. 1 (January 2008): 101–11. https://doi.org/10.1118/1.2804616.
Sakhalkar, H. S., and M. Oldham. “Fast, high-resolution 3D dosimetry utilizing a novel optical-CT scanner incorporating tertiary telecentric collimation.Med Phys, vol. 35, no. 1, Jan. 2008, pp. 101–11. Pubmed, doi:10.1118/1.2804616.

Published In

Med Phys

DOI

ISSN

0094-2405

Publication Date

January 2008

Volume

35

Issue

1

Start / End Page

101 / 111

Location

United States

Related Subject Headings

  • Tomography Scanners, X-Ray Computed
  • Time Factors
  • Radiotherapy, Intensity-Modulated
  • Radiation Dosage
  • Optics and Photonics
  • Nuclear Medicine & Medical Imaging
  • Imaging, Three-Dimensional
  • Artifacts
  • 5105 Medical and biological physics
  • 4003 Biomedical engineering