Stereotactic Radiosurgery using the Gamma Knife Consists of five main steps
Head frame with CT/MRI box attached to the frame
1. Frame placement. A lightweight frame is fitted over the patient’s head and attached with screws using local anesthesia. The frame serves two purposes: On the side of the frame are markers that allow the treatment team to pinpoint areas that will receive treatment. The frame also keeps the patient’s head immobile during the radiation procedure.
3-D image of an acoustic neuroma (in yellow) (top view)
2. Imaging Study. Imaging studies are obtained using MRI, CT scan, angiography, or a combination of these technologies. The imaging studies produce a three-dimensional map of the tumor and the surrounding brain structures.
Screenshot of computer workstation view of left-sided 1.8-cm acoustic neuroma prior to planning. (Clockwise from top left: axial, coronal, axial, sagittal views)
Left-side 1.8-cm acoustic neuroma prior to treatment plan. (Yellow=outline of radiation target around tumor)
Left-side 1.8-cm acoustic neuroma treatment plan. (Yellow=outline of radiation target around tumor and red circles=radiation “shots”)
3. Treatment planning. Based on the imaging studies, your physician works with a radiation oncologist and a medical physicist to develop the treatment plan that accurately targets the tumor with exact precision, sparing surrounding tissue as much as possible (i.e. a plan than conforms closely to the shape of the lesion).
Perfexion Gamma Knife radiation bed and machine
4. Radiation treatment. Treatment begins by first having the patient lie on the Gamma Knife bed (Left Figure Below). The head frame is fitted into a helmet with 201 holes in the helmet (Right Figure Below). The helmet helps to guide 201 sources of cobalt 60 based (photon) radiation beams to accurately target the tumor. After the helmet is placed, the bed is precisely moved into the domed unit and treatment begins. Depending on the size and location of the tumor, the actual time of radiation delivery could range from a few minutes to over an hour.
5. Removal of the head frame. Removal of the frame is a painless procedure. Most patients are able to go home shortly after the head frame is removed.
For Frequently Asked Questions regarding Gamma Knife Radiosurgery, click here.