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The optimisation of wedge filters in radiotherapy of the prostate.

Publication ,  Journal Article
Oldham, M; Neal, AJ; Webb, S
Published in: Radiother Oncol
December 1995

A treatment plan optimisation algorithm has been applied to 12 patients with early prostate cancer in order to determine the optimum beam-weights and wedge angles for a standard conformal three-field treatment technique. The optimisation algorithm was based on fast-stimulated-annealing using a cost function designed to achieve a uniform dose in the planning-target-volume (PTV) and to minimise the integral doses to the organs-at-risk. The algorithm has been applied to standard conformal three-field plans created by an experienced human planner, and run in three PLAN MODES: (1) where the wedge angles were fixed by the human planner and only the beam-weights were optimised; (2) where both the wedge angles and beam-weights were optimised; and (3) where both the wedge angles and beam-weights were optimised and a non-uniform dose was prescribed to the PTV. In the latter PLAN MODE, a uniform 100% dose was prescribed to all of the PTV except for that region that overlaps with the rectum where a lower (e.g., 90%) dose was prescribed. The resulting optimised plans have been compared with those of the human planner who found beam-weights by conventional forward planning techniques. Plans were compared on the basis of dose statistics, normal-tissue-complication-probability (NTCP) and tumour-control-probability (TCP). The results of the comparison showed that all three PLAN MODES produced plans with slightly higher TCP for the same rectal NTCP, than the human planner. The best results were observed for PLAN MODE 3, where an average increase in TCP of 0.73% (+/- 0.20, 95% confidence interval) was predicted by the biological models. This increase arises from a beneficial dose gradient which is produced across the tumour. Although the TCP gain is small it comes with no increase in treatment complexity, and could translate into increased cures given the large numbers of patients being referred. A study of the beam-weights and wedge angles chosen by the optimisation algorithm revealed significant inter-patient variability the implications of which are examined. Probably the most significant benefit of the algorithm is the time saved (about a factor of 10) in computing optimised beam-weights and wedge angles for this simple plan.

Duke Scholars

Published In

Radiother Oncol

DOI

ISSN

0167-8140

Publication Date

December 1995

Volume

37

Issue

3

Start / End Page

209 / 220

Location

Ireland

Related Subject Headings

  • Urinary Bladder
  • Software
  • Rectum
  • Radiotherapy Planning, Computer-Assisted
  • Radiation Protection
  • Radiation Injuries
  • Prostatic Neoplasms
  • Prostate
  • Oncology & Carcinogenesis
  • Male
 

Citation

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Oldham, M., Neal, A. J., & Webb, S. (1995). The optimisation of wedge filters in radiotherapy of the prostate. Radiother Oncol, 37(3), 209–220. https://doi.org/10.1016/0167-8140(95)01650-3
Oldham, M., A. J. Neal, and S. Webb. “The optimisation of wedge filters in radiotherapy of the prostate.Radiother Oncol 37, no. 3 (December 1995): 209–20. https://doi.org/10.1016/0167-8140(95)01650-3.
Oldham M, Neal AJ, Webb S. The optimisation of wedge filters in radiotherapy of the prostate. Radiother Oncol. 1995 Dec;37(3):209–20.
Oldham, M., et al. “The optimisation of wedge filters in radiotherapy of the prostate.Radiother Oncol, vol. 37, no. 3, Dec. 1995, pp. 209–20. Pubmed, doi:10.1016/0167-8140(95)01650-3.
Oldham M, Neal AJ, Webb S. The optimisation of wedge filters in radiotherapy of the prostate. Radiother Oncol. 1995 Dec;37(3):209–220.
Journal cover image

Published In

Radiother Oncol

DOI

ISSN

0167-8140

Publication Date

December 1995

Volume

37

Issue

3

Start / End Page

209 / 220

Location

Ireland

Related Subject Headings

  • Urinary Bladder
  • Software
  • Rectum
  • Radiotherapy Planning, Computer-Assisted
  • Radiation Protection
  • Radiation Injuries
  • Prostatic Neoplasms
  • Prostate
  • Oncology & Carcinogenesis
  • Male