Multiple brain metastases with far-lateral,far-anterior or far-posterior locations, enmeshed intracranial tumors, and skull base tumors with extracranial components are difficult to treat using earlier generation gamma knife system. Taking advantage of the large collimator treatment volumes and fully automated design, Perfexion has the capability to treat these difficult lesions successfully. However, not all these kinds of lesions can be treated smoothly, some parts of lesions are unable to be irradiated or irradiated safely.  

     In addition to the excellent new hardware,new version Gamma plan have improved the treatment-planning capabilities. Pretreatment planning, one of which, can assure the questionable candidates treatable or not.

      

     We have been using pretreatment planning for some questionable candidates for gamma knife radiosurgery because of concerns of radiation beams unreachable or dosage exceeding 8Gy over optic apparatus. The questionable candidates includes (1) multiple brain metastases with far-lateral,far-anteior or far-posterior locations (2) Parasellar tumor with optic apparatus encasement (3) skull base tumors with extracranial components, such as NPC, maxillary sinus tumor, big skull base meningioma with extracranial invasion. High-resolution magnetic resonance imaging scans ( 3-D SPGRE T1-weighted postgadolinium ) were obtained without frame on and imported into Gamma plan. Preplanning allowed for region and volume setting, dose setting, and assessment of treatment plan by dose-volume histograms. Consequently, preplanning can determine if the difficult lesions can be treated safely and effectively before the treatment day. We also compared the parameters we have measured by histograms, and the optimal treatment plan was determined before the day of treatment.

     Using preplanning, we have treated some difficult lesions smoothly. For patients with craniopharyngioma /skull base meningioma with optic apparatus encasement, preplanning showed that we were able to give therapeutic prescription dose without exceeding 8Gy to the optic apparatus. For patients with multiple brain metastases with far-lateral,far-anterior or far-posterior locations, NPC and maxillary sinus tumor, preplanning afford us the information about lesions reachability by radiation beams. No complications have occurred. Meanwhile, we also cancelled Gamma knife treatment for some patients if the preplanning revealed the treatment was unsafe, time-consuming or the lesions were not reachable by radiation beams.

     This is a retrospective study.

     Preplanning technique is feasible and easy to use by Perfexion gamma knife and new version Gamma plan.

     In our experience, preplanning technique can increase the treatment rate of questionable candidates for Gamma knife radiosurgery. Preplanning allows for better patient comfort, personnel comfort and better cost performance.