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A novel probabilistic approach to generating PTV with partial voxel contributions
H S Tsang1, C P Kamerling, P Ziegenhein
1Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG, United Kingdom.
Physics in Medicine and Biology
|April 6, 2017
Summary
This study introduces beam-dependent planning target volumes (bdPTVs) for radiotherapy, improving organ at risk (OAR) sparing in prostate cancer treatment. While slightly reducing target coverage, the method ensures adequate dose delivery to the planning target volume (PTV).
Area of Science:
- Radiation Oncology
- Medical Physics
- Radiotherapy Treatment Planning
Background:
- Current radiotherapy planning uses a binary approach for planning target volume (PTV) definition.
- This binary method does not account for individual beam directions in high-energy photon beam treatments.
Purpose of the Study:
- To introduce a novel margin concept generating beam-dependent PTVs (bdPTVs) for improved radiotherapy planning.
- To investigate the impact of bdPTVs on prostate radiotherapy treatments compared to conventional margins.
Main Methods:
- Developed a margin concept considering beam directions to create bdPTVs on a beam-by-beam basis.
- Integrated bdPTV overlaps into the optimization process, allowing voxels to be treated as both target and organ at risk (OAR) with fractional contributions.
- Compared treatment plans generated with bdPTVs against conventional margins in five prostate cancer patients.
Main Results:
- Plans using bdPTVs demonstrated improved sparing of high doses to organs at risk (OARs) surrounding the target.
- A trade-off was observed, with a slight increase in low-dose delivery to OARs.
- A minor reduction in target coverage was noted, though all plans met clinical dose-volume histogram requirements.
Conclusions:
- Beam-dependent PTV margins offer potential for enhanced OAR sparing in radiotherapy.
- The approach requires careful optimization to balance OAR sparing with target coverage.
- Further research is warranted to fully evaluate the clinical utility of bdPTVs.