Leksell gamma knife perfexion – an excellent tool for Intracranial radiosurgery.

   Background

   Leksell Gamma Knife (LGK) PERFEXION (PFX) model (Figure 1) is an entirely new design of LGK as compared to other models U, B, C and 4C. The PFX system has 192 Co-60 sources that are fixed on eight sectors. Each sector can be automatically moved independently to five different positions: three positions define collimator sizes (4, 8, 16 mm), off position (sources are blocked) and home position. The machine aperture for the patient’s head during treatment was increased in volume by more than three times resulting in a greater mechanical treatment range in X/Y/Z stereotactic coordinates. The Automatic Positioning System responsible for stereotactic coordinates setting was replaced by a Patient Positioning System that moves the whole robotic couch with patient body to pre selected stereotactic coordinates improving patient comfort and efficiency of the treatment. This study describes four years experience from the University of Pittsburgh Medical Center and two years experience from Na Homolce Hospital with this new radiosurgery system. Study compares and evaluates dosimetry, treatment planning, treatment efficiency, accuracy and overall performance of this new gamma knife system.

   Methods

   Almost 2000 patients were treated at the University of Pittsburgh between Sep, 2007 and Sep, 2011 with PFX system. Over 2000 patients were treated at Na Homolce Hospital between Dec 2009 and Dec 2011. These patients included various intracranial benign and malignant tumors: acoustic neuromas, meningiomas, pituitary adenomas, low grade and high grade gliomas and single or multiple intracranial metastases. Patients’ diagnosis included also arteriovenous malformations and functional treatments mostly trigeminal neuralgias. Overall dosimetry and mechanical performance of the PFX system was monitored by regular qua- lity assurance program.

   Results

   New PFX system appeared to be very rigid system with zero down time. There were observed no technical issues with the system during observed period of time. Dosimetry and mechanical performed tests showed excellent stability, accuracy and precision of the PFX system. Typical deviation in measured calibration dose was within 1.0 %; mean total robotic couch positioning accuracy in all three axes was within 0.1 mm during the observed period of time. All patients were treated without any problem or difficulties.

   Conclusion

   The new PFX system demonstrated excellent performance with very high efficiency and patient comfort due to the fully automated treatment process. No difficulties were observed to reach all targets within one single stereotactic frame placement. A significant time saving was observed when comparing treatment with the previous 4C model, especially for multiple targets.