Stereotactic Radiosurgery — Brain (SRS)

Single-fraction (or up to 5-fraction hypofractionated) high-dose radiation to intracranial targets — brain metastases, arteriovenous malformations, acoustic neuromas, meningiomas, trigeminal neuralgia, functional targets. Millimeter targeting accuracy combined with steep dose falloff spares surrounding brain.

Clinical pathway

1. Immobilization — frame-based (Leksell G-frame, invasive pins) or frameless (thermoplastic mask + optical/CBCT tracking).
2. Imaging + target definition — high-resolution stereotactic MRI fused with planning CT; contours drawn on each lesion plus critical structures (brainstem, optic apparatus, cochlea, hippocampi).
3. Treatment planning — inverse planning for Gamma Knife multi-isocenter shots, MLC-based VMAT arcs on linac, or CyberKnife non-isocentric beams.
4. Delivery — Gamma Knife (60+ Co-60 sources converging), linac SRS (cone or MLC-based), or CyberKnife (robotic 6D tracking).
5. Follow-up MRI — typically 2–3 months post.

Typical systems

• Leksell Gamma Knife Icon
• Leksell Gamma Knife Perfexion
• Varian TrueBeam STx
• CyberKnife M6
• Elekta Versa HD

Dose characteristics

• Single-fraction typical dose: 15–24 Gy depending on target size (smaller = higher dose per RTOG 90-05 constraints)
• 12 Gy volume in normal brain is the radiation necrosis predictor
• Steep gradients: 50% isodose at or near target edge

Room + procedure characteristics

• Treatment time: 20–90 min per session depending on lesion count and platform
• Team: radiation oncologist, neurosurgeon (often co-attends), medical physicist, dosimetrist, RT
• QA: TG-142-level daily + monthly + annual, plus end-to-end hidden-target tests specific to SRS

Related

• SBRT (body)
• Gamma Knife MOC
• CyberKnife MOC