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Commissioning and benchmarking a 3D dosimetry system for clinical use.

Publication ,  Journal Article
Thomas, A; Newton, J; Adamovics, J; Oldham, M
Published in: Med Phys
August 2011

PURPOSE: A 3D dosimetry system is described which consists of two parts: a radiochromic plastic dosimeter PRESAGE (which responds to absorbed dose with a linear change in optical-density) and the Duke large-field-of-view optical-CT scanner (DLOS). The DLOS/PRESAGE system has recently been commissioned and benchmarked for clinical use and, in particular, for verification and commissioning of complex radiation treatments. METHODS: DLOS commissioning involved determining the dynamic range, spatial resolution, noise, temporal, and other characteristics of the light source and imaging components. Benchmarking tests were performed on the combined DLOS/PRESAGE system to establish baseline dosimetric performance. The tests consisted of delivering simple radiation treatments to PRESAGE dosimeters, and comparing the measured 3D relative dose distributions with the known gold standard. The gold standard distribution was obtained from machine beam-data or the treatment planning system (TPS). All studies used standardized procedures to ensure consistency. RESULTS: For commissioning, isotropic spatial resolution was submillimeter (MTF > 0.5 for frequencies of 1.5 lp/mm) and the dynamic range was -60 dB. Flood field uniformity was within 10% and stable after 45 min of warm-up. Stray-light is small, due to telecentricity, but even the residual can be removed through deconvolution by a point-spread-function. For benchmarking, the mean 3D passing NDD (normalized dose distribution) rate (3%, 3mm, 5% dose threshold) over the benchmark data sets was 97.3% +/- 0.6% (range 96%-98%), which is on par with other planar dosimeters used in external beam radiation therapy indicating excellent agreement. Noise was low at < 2% of maximum dose (4-12 Gy) for 2 mm reconstructions. The telecentric design was critical to enabling fast imaging with minimal stray-light artifacts. CONCLUSIONS: This work presents the first comprehensive benchmarking of a 3D dosimetry system for clinical use. The DLOS/PRESAGE benchmark tests show consistently good agreement to simple known distributions. The system produces accurate isotropic 2 mm dose data over clinical volumes (e.g., 16 cm diameter phantoms, 12 cm height), in under 15 min. It represents a uniquely useful and versatile new tool for commissioning and verification of complex therapy treatments.

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Published In

Med Phys

DOI

ISSN

0094-2405

Publication Date

August 2011

Volume

38

Issue

8

Start / End Page

4846 / 4857

Location

United States

Related Subject Headings

  • Tomography, X-Ray Computed
  • Radiotherapy Planning, Computer-Assisted
  • Radiometry
  • Nuclear Medicine & Medical Imaging
  • Imaging, Three-Dimensional
  • Humans
  • Benchmarking
  • 5105 Medical and biological physics
  • 4003 Biomedical engineering
  • 1112 Oncology and Carcinogenesis
 

Citation

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Thomas, A., Newton, J., Adamovics, J., & Oldham, M. (2011). Commissioning and benchmarking a 3D dosimetry system for clinical use. Med Phys, 38(8), 4846–4857. https://doi.org/10.1118/1.3611042
Thomas, Andrew, Joseph Newton, John Adamovics, and Mark Oldham. “Commissioning and benchmarking a 3D dosimetry system for clinical use.Med Phys 38, no. 8 (August 2011): 4846–57. https://doi.org/10.1118/1.3611042.
Thomas A, Newton J, Adamovics J, Oldham M. Commissioning and benchmarking a 3D dosimetry system for clinical use. Med Phys. 2011 Aug;38(8):4846–57.
Thomas, Andrew, et al. “Commissioning and benchmarking a 3D dosimetry system for clinical use.Med Phys, vol. 38, no. 8, Aug. 2011, pp. 4846–57. Pubmed, doi:10.1118/1.3611042.
Thomas A, Newton J, Adamovics J, Oldham M. Commissioning and benchmarking a 3D dosimetry system for clinical use. Med Phys. 2011 Aug;38(8):4846–4857.

Published In

Med Phys

DOI

ISSN

0094-2405

Publication Date

August 2011

Volume

38

Issue

8

Start / End Page

4846 / 4857

Location

United States

Related Subject Headings

  • Tomography, X-Ray Computed
  • Radiotherapy Planning, Computer-Assisted
  • Radiometry
  • Nuclear Medicine & Medical Imaging
  • Imaging, Three-Dimensional
  • Humans
  • Benchmarking
  • 5105 Medical and biological physics
  • 4003 Biomedical engineering
  • 1112 Oncology and Carcinogenesis