Perfexion Registration Using CBCT

Official Title

Use of Cone-beam Computed Tomography on Gamma Knife Perfexion for Stereotactic Radiosurgery


Measuring precision radiation delivery through cone-beam computed tomography (CBCT) and intra-fraction motion management (IFMM) incorporated on a GammaKnife unit via the Leksell Coordinate Frame (LCF) and relocatable mask system (RMS) immobilization devices.

Trial Description

Primary Outcome:

  • Setup variation of LCF and relocatable mask using CBCT Imaging
  • Setup variation in positioning between CT planning and treatment
Secondary Outcome:
  • Target volume margins for brain metastases
: Brain metastases are reported to occur in 20% to 40% of all patients with cancer. Treatment options for brain metastases include surgical resection, particularly in lesions causing significant mass effect, whole brain radiation (WBRT) and radiosurgery (SRS). Due to concerns of neurocognitive toxicity following WBRT, there is growing use of SRS, particularly in patients with limited brain metastases and controlled extracranial disease. Radiosurgery delivers a high dose of radiation to a defined intracranial target through precise targeting with a sharp dose fall off at the target boundaries and minimal damage to surrounding tissue. To date, precision radiation delivery has been facilitated through the Leksell Coordinate Frame (LCF), fixated to the patient's skull through 4 pins. A relocatable mask system (RMS), consisting of a patient specific head rest and mask was developed to enable minimally-invasive fractioned radiosurgery. A cone-beam computed tomography (CBCT) image guidance and intra-fraction motion management (IFMM) system was previously developed in-house in order to measure and address setup uncertainties on Gamma Knife. The in-house prototype has been integrated into a commercially available GammaKnife device with CBCT guidance. The installation of this device will enable volumetric guidance for all patients treated in either a single or multiple session on GammaKnife Perfexion. This study is designed to have 2 arms, A and B. Both Arm A (using the Leksell Coordinate Frame) and Arm B (using the relocatable mask) are undergoing standard of care treatment on GammaKnife Perfexion for SRS. CBCT is part of standard of care for Arm B. However, CBCT imaging is considered as part of study treatment for Arm A. Pre and post treatment images will be acquired of the patient treated on Perfexion Gamma Knife using the Leksell Coordinate Frame in order to aid in analyzing the imaging metrics of the Image Guided Perfexion unit.

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