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A case study comparing the relative benefit of optimizing beam weights, wedge angles, beam orientations and tomotherapy in stereotactic radiotherapy of the brain.

Publication ,  Journal Article
Oldham, M; Khoo, VS; Rowbottom, CG; Bedford, JL; Webb, S
Published in: Phys Med Biol
August 1998

A treatment-planning case study has been performed on a patient with a medium-sized, convex brain tumour. The study involved the application of advanced treatment-plan optimization techniques to improve on the dose distribution of the 'standard plan' used to treat the patient. The standard plan was created according to conventional protocol at the Royal Marsden NHS Trust, and consisted of a three-field (one open and two wedged) non-coplanar arrangement, with field shaping to the beam's-eye view of the planning target volume (PTV). Three optimized treatment plans were created corresponding to (i) the optimization of the beam weights and wedge angles of the standard plan, (ii) the optimization of the beam orientations, beam weights and wedge angles of the standard plan, and (iii) a full fluence tomotherapy optimization of 1 cm wide (at isocentre), 270 degree arcs. (i) and (ii) were created on the VOXELPLAN research 3D treatment-planning system, using in-house developed optimization algorithms, and (iii) was created on the PEACOCK tomotherapy planning system. The downhill-simplex optimization algorithm is used, in conjunction with 'threshold-dose' cost-function terms enabling the algorithm to optimize specific regions of the dose-volume histogram (DVH) curve. The 'beam-cost plot' tool is presented as a visual aid to the selection of beneficial beam directions. The methods and pitfalls in the transfer of plans and patient data between the two planning systems are discussed. Each optimization approach was evaluated, relative to the standard plan, on the basis of DVH and dose statistics in the PTV and organs at risk (OARs). All three optimization approaches were able to improve on the dose distribution of the standard plan. The magnitude of the improvement was greater for the optimized beam-orientation and tomotherapy plans (up to 15% and 30% for the maximum and mean OAR doses). A smaller improvement was observed in the beam-weight and wedge-angle optimized plan (up to 5% and 10% in the maximum and mean OAR doses). In the tomotherapy plan, difficulty was encountered achieving an acceptable homogeneity of dose in the PTV. This was improved by treating the gross tumour volume (GTV) and (PTV - GTV) regions as separate targets in the inverse planning, with the latter region prescribed a slightly higher dose to reduce edge under-dosing. In conclusion, for the medium-sized convex tumour studied, the tomotherapy dose distribution showed a significant improvement on the standard plan, but no significant improvement over a conventional three-field plan where the beam orientations, beam weights and wedge angles had been optimized.

Duke Scholars

Published In

Phys Med Biol

DOI

ISSN

0031-9155

Publication Date

August 1998

Volume

43

Issue

8

Start / End Page

2123 / 2146

Location

England

Related Subject Headings

  • Stereotaxic Techniques
  • Software
  • Reproducibility of Results
  • Radiotherapy, Computer-Assisted
  • Radiotherapy Planning, Computer-Assisted
  • Pituitary Neoplasms
  • Pituitary Irradiation
  • Nuclear Medicine & Medical Imaging
  • Humans
  • Brain Neoplasms
 

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Oldham, M., Khoo, V. S., Rowbottom, C. G., Bedford, J. L., & Webb, S. (1998). A case study comparing the relative benefit of optimizing beam weights, wedge angles, beam orientations and tomotherapy in stereotactic radiotherapy of the brain. Phys Med Biol, 43(8), 2123–2146. https://doi.org/10.1088/0031-9155/43/8/010
Oldham, M., V. S. Khoo, C. G. Rowbottom, J. L. Bedford, and S. Webb. “A case study comparing the relative benefit of optimizing beam weights, wedge angles, beam orientations and tomotherapy in stereotactic radiotherapy of the brain.Phys Med Biol 43, no. 8 (August 1998): 2123–46. https://doi.org/10.1088/0031-9155/43/8/010.
Oldham, M., et al. “A case study comparing the relative benefit of optimizing beam weights, wedge angles, beam orientations and tomotherapy in stereotactic radiotherapy of the brain.Phys Med Biol, vol. 43, no. 8, Aug. 1998, pp. 2123–46. Pubmed, doi:10.1088/0031-9155/43/8/010.
Journal cover image

Published In

Phys Med Biol

DOI

ISSN

0031-9155

Publication Date

August 1998

Volume

43

Issue

8

Start / End Page

2123 / 2146

Location

England

Related Subject Headings

  • Stereotaxic Techniques
  • Software
  • Reproducibility of Results
  • Radiotherapy, Computer-Assisted
  • Radiotherapy Planning, Computer-Assisted
  • Pituitary Neoplasms
  • Pituitary Irradiation
  • Nuclear Medicine & Medical Imaging
  • Humans
  • Brain Neoplasms