Gamma Knife

The term Gamma Knife combines “gamma rays” and “knife,” reflecting its ability to treat brain lesions with high-energy gamma rays without the need for a surgical incision or general anesthesia. By directing 192 finely focused beams of radiation from cobalt-60 sources, Gamma Knife radiosurgery converges energy precisely on the target, while sparing surrounding healthy brain tissue. This is similar to how a magnifying glass can focus sunlight onto a single point to burn paper.

[Purpose]

Gamma Knife radiosurgery is designed to safely and accurately treat brain tumors, vascular malformations, and functional disorders without damaging normal brain structures. It provides an effective alternative to conventional surgery, especially for lesions located deep within the brain or near critical structures.

Gamma Knife treatment can be performed using three different fixation methods:

1. Frame-Based Fixation

• Frame placement: A stereotactic head frame is applied to accurately map the coordinates of the lesion and keep the head immobile during treatment.
• Imaging: MRI or CT scans are performed to determine the exact location, size, and shape of the lesion.
• Treatment planning: A tailored plan is created to deliver the optimal radiation dose and distribution.
• Treatment: Radiation delivery is painless and silent. The patient’s condition is continuously monitored. After treatment, the frame is removed.
• Follow-up: Because therapeutic effects develop gradually over months to years, regular outpatient visits and imaging follow-up are required.

2. Frame-Based Fixation with Cone-Beam CT (CBCT)

• Imaging: Pre-treatment MRI or CT scans provide detailed mapping of the lesion.
• Preliminary planning: An initial plan is generated to optimize radiation dose and field.
• Frame placement: The stereotactic frame is secured for precise localization and head stabilization.
• CBCT scan: A cone-beam CT is performed immediately before treatment.
• Image fusion: CBCT images are fused with the preliminary plan to finalize treatment coordinates and dose.
• Treatment: Painless, silent radiation delivery is performed, followed by frame removal.

3. Mask-Based Fixation

• Imaging: MRI or CT scans identify the lesion’s characteristics.
• Preliminary planning: An initial treatment plan is generated.
• Mask fabrication: A custom thermoplastic facial mask is molded to immobilize the head. This method allows for painless, fractionated treatments.
• CBCT scan: Provides accurate head position data immediately before treatment.
• Image fusion: CBCT data are fused with the preliminary plan to finalize the treatment setup.
• Treatment: Radiation delivery is painless and silent. The mask is removed after each session. Treatments are usually given over 2–5 days.
• Diet: Resume your usual meals.
• Wound care: Remove the small dressings at the frame pin sites the day after treatment. No home disinfection is required. Washing the face and shampooing are permitted after two days.
• Daily activities: Most patients can return to normal activities the next day.
• Outpatient follow-up: A clinic visit is usually scheduled 2–4 weeks later to review post-treatment progress and plan ongoing care.
• Other considerations: Mild dizziness, headache, nausea, or scalp numbness may occur but are usually temporary and resolve within a few days.

Treatment outcomes vary depending on the type, size, and location of the lesion. For well-selected conditions such as vestibular schwannomas or arteriovenous malformations (AVMs), Gamma Knife achieves tumor or malformation control in approximately 80-90% of patients without significant complications.

Because the therapeutic effect develops slowly over several months to years, long-term follow-up with periodic imaging is essential to monitor changes in the treated lesion.