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Treatment plan complexity metrics for predicting IMRT pre-treatment quality assurance results


The planning of IMRT treatments requires a compromise between dose conformity (complexity) and deliverability. This study investigates established and novel treatment complexity metrics for 122 IMRT beams from prostate treatment plans. The Treatment and Dose Assessor software was used to extract the necessary data from exported treatment plan files and calculate the metrics. For most of the metrics, there was strong overlap between the calculated values for plans that passed and failed their quality assurance (QA) tests. However, statistically significant variation between plans that passed and failed QA measurements was found for the established modulation index and for a novel metric describing the proportion of small apertures in each beam. The ‘small aperture score’ provided threshold values which successfully distinguished deliverable treatment plans from plans that did not pass QA, with a low false negative rate.

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Correspondence to S. B. Crowe.

Additional information

This study was supported by the Australian Research Council, the Wesley Research Institute, Premion and the Queensland University of Technology (QUT), through linkage grant number LP110100401.

Appendix: Summary of initialisms

Appendix: Summary of initialisms

  • AAV: Aperture area variability

  • CAS: Cross axis score

  • CLS: Closed leaf score

  • FMC: Fluence map complexity

  • LSV: Leaf sequence variability

  • MAD: Mean aperture displacement

  • MCDTK: Monte Carlo DICOM tool-kit

  • MCS: Modulation complexity score

  • MFA: Mean field area

  • MI: Modulation index

  • SAS: Small aperture score

  • TADA: Treatment and dose assessor

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Crowe, S.B., Kairn, T., Kenny, J. et al. Treatment plan complexity metrics for predicting IMRT pre-treatment quality assurance results. Australas Phys Eng Sci Med 37, 475–482 (2014).

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  • Quality assurance
  • Beam complexity
  • Radiation therapy