Gamma Knife Radiation and Imaging Techniques at Hoag

Advanced Imaging Technique

The evolution and success of Gamma Knife Radiosurgery is directly dependent on the imaging modalities available to determine the location of the tumor or AVM. A Gamma Knife (GK) treatment center must have the accompanying state-of-the-art imaging modalities and neuro-oncologic radiology specialists in order to maximize the efficacy of the GK treatment unit and team. Hoag is fortunate to have both the technology and the staffing to collaborate on neurological and Gamma Knife patients.

Learn more about the advanced Neuro Imaging available at Hoag.

Gamma Knife Radiation

The leading edge technique is an innovative process developed to treat one of the most common types of glioma, glioblastoma multiforme. This treatment combines the functionality of the Gamma Knife with the advances in diagnostic radiology technology, which include Multivoxel MR-Spectroscopy scans. This unique combination targets the radiation beyond the local tumor volume to include the potential malignant tumor path. Prior to this technological spectroscopy breakthrough, it was impossible to detect where the tumor would or might spread.

Clinical Explanation

Glioblastoma multiforme (GBM) is among the most common and devastating brain tumors affecting adults. The most successful treatment regimens for GBMs include surgical resection, radiation therapy and chemotherapy, followed by stereotactic radiosurgical boost (Gamma Knife radiosurgery) and immunotherapy. Despite aggressive therapies, the malignant nature of GBMs often results in tumor recurrence. Ninety percent of GBMs recur at the site of the original tumor. In addition to local recurrence, malignant gliomas frequently spread in predictable patterns along the white matter pathways in the brain. It is via this mechanism that long-fought battles against GBMs are often lost.

Predictable Patterns of Spread in Malignant Gliomas

Traditional radiosurgical techniques have focused solely on local tumor margins, as determined by gadolinium enhancement on MRI. However, recent data suggests that by targeting the "leading edge" of these tumors, their spread along white matter pathways can be more effectively halted. FLAIR sequences and Multivoxel MR-Spect scans can be utilized to define positive areas outside of the gadolinium T1-weighted enhancing zones. Targeting these zones with gamma knife is proving to be a successful method of blocking the path of malignant gliomas.​

Gamma Knife Treatment Process

1. The patient is admitted to the hospital on the morning of the procedure and started on intravenous fluids. A stereotactic frame is painlessly secured to the patient's head. This head frame is a guiding device, which ensures the Gamma Knife beams are focused exactly where the treatment is needed. Mild sedation and a local anesthetic are administered prior to head frame placement. Head frame placement usually takes fewer than 10 minutes.
2. Imaging studies, such as MRI, CT scan and/or angiography are performed. The stereotactic frame is displayed on the imaging studies allowing the physicians to precisely localize the target.
3. The team of Gamma Knife physicians utilizes three-dimensional computer imaging to develop the patient's radiosurgical treatment plan.
4. When the treatment plan is complete, the patient is placed on the Gamma Knife bed. The stereotactic head frame is attached to the helmet containing 192 portals through which radiation beams are focused. The frame and the helmet prevent movement, ensuring accurate alignment during treatment.
5. The Gamma Knife team monitors the patient throughout the procedure. Actual treatment may last as little as 10 minutes or as long as two hours. During the procedure, the patient does not hear or feel the Gamma Knife delivering the radiation treatment.
6. The head frame is removed upon completion of the treatment and bandages are applied to the pin site areas. The patient is observed for approximately one hour, then discharged from the hospital.
7. The patient is contacted by the Gamma Knife nurse the next day for follow-up and then periodically to monitor the patient's status.​

Download the Gamma Knife Patient Instructions.​​