AbstractID: 6770 Title: An Analytical Dose Model For Treatment Planning Optimization
and Quality Assurance of Gamma Knife Stereotactic Radiosurgery
An analytical dose model was developed for γ-knife radiosurgery. The model was used
for inverse treatment planning optimization of the γ-knife procedure. It was also
implemented to perform clinical quality assurance hand-calculation checks for the
Leksell Gamma Plan (LGP) system.
The model was developed based on the isodose distributions for a single γ-knife shot that
are in the shape of an expanding ellipsoid. The dose model was commissioned by fitting
the measured dose profiles for each individual helmet along its major axes. The model
was verified by comparing its calculation with the LGP calculation results for 25 patient
cases. These cases included varying target volumes (5-20 cm3), number of the shots (215), and helmet sizes (4mm, 8mm, 14mm and 18mm).
Our results showed an agreement between the model calculations and the LGP results to
be within 2% and 2 mm for all tested cases. In comparison with the LGP dose model, an
advantage of our model is that the spatial dose gradient can be explicitly computed thus
allowing optimization algorithms to be effectively applied. Because of the simplicity and
the accuracy of the model, it was also used for checking point dose and prescribing
isodose distribution of a γ-knife plan.
In summary, we have demonstrated a fast and an accurate γ-knife dose calculation tool
for carrying out inverse treatment-planning optimization and routine clinical quality
assurance tasks.
This work is supported in part by a research grant BC99087 from the Department of U.S.
Army.