JRSBRT 6.3, p. 227-233

A standardised method for use of the Leksell GammaPlan Inverse Planning module for metastases
Peter Fallows, Gavin Wright and Peter Bownes

Aim: The aim of this investigation was to develop a standardised method for using the inverse planning module in Leksell GammaPlan.

Methods: Leksell GammaPlan version 10 and higher contains an inverse planning module, consisting of functions to automatically fill a target volume with shots and subsequently optimise their resulting dosimetry. A standardised method for using the inverse planning module was developed for metastases, using the following optimisation parameter weightings: {coverage 0.9, selectivity 0.1, gradient index (GI) 0.2, }. 25 plans produced using these parameters were comparedto manually produced clinical plans. Additionally, the 25 plans were manually adjusted to match the coverage of the clinical plans, and comparison of the PCI, GI and BOT was made.

Results: The average parameters for plans produced using the optimisation module were; coverage 98.7%; Paddick conformity index (PCI) 0.85; GI 2.75, compared to coverage 99.5%; PCI 0.83; GI 2.70 for manual clinical plans with BOT 21% shorter than clinical plans on average. The average parameters for the plans produced by the optimisation module after manual adjustment to match the coverage of the clinical plans were: coverage 99.5, PCI 0.83, GI 2.73 with BOT 16% shorter than clinical plans on average.

Conclusions: The standardised method for using the optimisation module has potential for shortening treatment times and planning times.

Keywords: Gamma Knife, inverse planning, optimiser, stereotactic radiosurgery

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