Comparison of radiosurgery planning modalities for acoustic neuroma with regard to conformity and mean target dose.
OBJECTIVE
To evaluate dose conformity and mean target dose in light of previous comparative studies and state-of-the-art radiosurgery delivery modalities.


METHODS
Seven patients with acoustic neuromas deemed clinically suitable for linear accelerator or Gamma Knife radiosurgery were planned such that the minimum doses for any plan were equal. Gamma Knife plans were prepared in three ways: by altering the prescription of previously published data, by hand and with the assistance of an automatic planning algorithm (wizard). The linear accelerator plans were prepared utilizing a micro-multileaf collimator in both static and dynamic modes. The dose volume histogram analyses lead to a measure of conformity and the mean and minimum target dose for each plan. Statistical significance was calculated as each planning modality was compared with every other.


RESULTS
All Gamma Knife plans demonstrated a statistically significantly better conformity when compared with fixed field linear accelerator techniques. When compared to linear accelerator techniques the wizard-assisted Gamma Knife plans demonstrated significantly better conformity. The mean target dose for all the Gamma Knife plans was significantly higher than that of the linear accelerator plans (19.2 Gy vs. 13.4 Gy).


CONCLUSIONS
Conformity of the prescription isodose to the target shape is of major importance in radiosurgery. The modalities compared represent commercially available and widely accepted systems. Gamma Knife plans derived using the 'wizard' option and finalized by hand yield the best conformity.
Perks
J R
JR
Radiation Oncology, UC Davis Medical Center, Sacramento, CA 95817, USA. julian.perks@ucdmc.ucdavis.edu
El-Hamri
K
K
Blackburn
T P D
TP
Plowman
P N
PN
D000465:Algorithms; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D009464:Neuroma, Acoustic / Q000503:physiopathology / Q000601:surgery*; D010315:Particle Accelerators / Q000295:instrumentation; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012984:Software