GAMMA KNIFE VS CYBERKNIFE VS TRUEBEAM
HOW TO CHOOSE
Three major platforms deliver SRS — each with genuine technical distinctions. But the most important conclusion is the one most marketing obscures: for most SRS indications, outcomes are equivalent between well-operated systems. Centre expertise matters more than the brand on the machine.
analyticsAt a Glance
- check_circleGamma Knife: dedicated intracranial — the original gold standard with the longest evidence base
- check_circleCyberKnife: robotic arm, continuous tracking — best for moving body targets and complex geometry
- check_circleTrueBeam/EDGE: versatile LINAC — SRS is one function of a comprehensive radiation platform
- check_circleFor most indications: outcomes are equivalent — centre volume and expertise drive results, not platform
Gamma Knife: The Original Intracranial Radiosurgery Platform
The Leksell Gamma Knife, developed by Lars Leksell and Börje Larsson in the 1960s, is the historical foundation of clinical radiosurgery. It remains the dominant dedicated intracranial SRS platform globally.
“Gamma Knife has treated more than one million patients over 60 years. Its clinical evidence base — across brain metastases, acoustic neuromas, meningiomas, AVMs, and functional indications — is larger and older than any competing platform. That evidence depth is its primary competitive advantage.”
How Gamma Knife Works
192 cobalt-60 radioactive sources arranged in a hemispheric helmet converge radiation beams on a focal point. The patient's head is positioned so the tumour lies exactly at the convergence point — the isocenter. Each of the 192 beams individually carries low dose; only at convergence does the dose reach ablative levels. The system does not move; the helmet containing the sources remains static.
Frame-Based vs Frameless (Icon)
Classic Gamma Knife used a stereotactic frame bolted to the skull — providing sub-millimetre positional accuracy. The Leksell Gamma Knife Icon uses a high-definition motion management system and thermoplastic mask for frameless treatment and intrafraction motion monitoring, allowing hypofractionated courses (2–5 fractions). This enables Gamma Knife to treat patients who cannot tolerate frame placement.
What Gamma Knife Is Best For
Brain metastases (the dominant indication globally). Acoustic neuroma. Meningioma. AVM. Pituitary adenoma. Trigeminal neuralgia. Functional indications. Gamma Knife is NOT designed for body (extracranial) SRS/SBRT. Its optimal anatomy is the brain and skull base.
CyberKnife: The Robotic Tracking System
CyberKnife (Accuray) is a 6-MV LINAC mounted on an industrial robotic arm — delivering radiation from hundreds of non-coplanar positions with continuous image tracking of the target.
How CyberKnife Works
The robotic arm positions the LINAC at thousands of non-coplanar nodes around the patient, delivering small beams from each direction. The system continuously acquires X-ray images of the patient during treatment, comparing to the planning CT, and adjusts delivery for any positional deviation. For body targets, the Synchrony system tracks tumour movement with breathing using implanted fiducial markers or soft tissue tracking.
What CyberKnife Is Best For
Moving body targets — lung, liver, pancreas SBRT where respiratory motion requires real-time tracking. Spine SRS (excellent for nerve-sparing accuracy). Complex-geometry intracranial cases. Fractionated (multi-session) SRS where a frame is impractical. Prostate SBRT. CyberKnife is the preferred platform when tumour motion is significant and real-time tracking adds clinical value.
TrueBeam / EDGE: The Versatile LINAC Platform
TrueBeam (Varian, now Siemens Healthineers) and its radiosurgery-optimised variant EDGE are high-performance LINAC systems that can deliver SRS/SBRT as one of many treatment modalities — not as a dedicated radiosurgery machine.
How TrueBeam Delivers SRS
TrueBeam delivers SRS via volumetric arc therapy (VMAT) or dynamic conformal arcs — rotating the LINAC gantry in arcs around the patient while shaping the beam through multi-leaf collimators. The EDGE variant adds a HD MLC (2.5 mm leaves vs standard 5 mm), enhanced imaging, and surface monitoring specifically for radiosurgery applications. Cone-beam CT verifies positioning before each fraction.
TrueBeam's Real Advantage
TrueBeam's advantage is versatility — the same machine can deliver conventional radiotherapy, SBRT, VMAT, and SRS. For hospitals that cannot justify three separate machines, TrueBeam provides SRS capability within a comprehensive radiation oncology programme. It can treat any body site and can deliver both single-fraction and hypofractionated SRS. Most modern radiation oncology departments have TrueBeam or equivalent VMAT-capable LINAC systems.
Platform Comparison: Gamma Knife vs CyberKnife vs TrueBeam
Technical and clinical comparison of the three platforms.
| Feature | Gamma Knife | CyberKnife | TrueBeam / EDGE |
|---|---|---|---|
| Radiation Source | Cobalt-60 (192 sources) | 6 MV LINAC on robotic arm | 6–10 MV LINAC on rotating gantry |
| Anatomical Scope | Intracranial only (brain, skull base) | Full body: intracranial + extracranial | Full body |
| Patient Immobilisation | Stereotactic frame (classic) or mask (Icon) | Mask or body mould (frameless) | Mask, body mould, surface monitoring |
| Tumour Motion Tracking | Head immobilisation only (no real-time tracking) | Continuous Synchrony tracking for moving targets | Respiratory gating; some surface tracking |
| Fraction Delivery Time | 15–90 min (depends on complexity) | 30–90 min (multiple nodes) | 15–60 min (arc delivery faster) |
| Best Intracranial Indication | Brain mets, acoustic neuroma, AVM, meningioma | Complex geometry; spine SRS; hypofractionated intracranial | Brain mets, general intracranial SRS |
| Best Extracranial Indication | Not designed for body SRS | Lung, liver, spine, prostate SBRT with motion | Lung, liver, prostate, spine SBRT |
| Global Installed Base | ~350 units worldwide | ~800+ units worldwide | ~3,000+ (TrueBeam/similar LINAC globally) |
| Evidence Base | Largest — 60+ years of clinical data | Strong for body SBRT; growing for intracranial | Strong for VMAT-SRS; body SBRT well evidenced |
The Honest Verdict: Does Platform Choice Matter?
After reviewing the technical differences, the most clinically important conclusion requires emphasis.
For Brain Metastases, Acoustic Neuroma, Meningioma: Outcomes Are Equivalent
No randomised trial has demonstrated superior local control, survival, or toxicity for any one platform vs another for the common intracranial SRS indications. Multiple comparative studies show equivalent outcomes between Gamma Knife, CyberKnife, and modern LINAC-based SRS. The technical differences — beam source, number of arcs, immobilisation method — do not translate into clinically meaningful outcome differences for well-executed treatment at experienced centres.
What Matters More Than Platform
Annual case volume of the treating centre. Neurosurgery, neuro-oncology, and radiation oncology MDT collaboration. Quality of treatment planning (delineation of target and critical structures). Experience treating your specific indication (acoustic neuroma SRS is technically different from brain metastases SRS). Whether you need fractionated or single-fraction treatment. Platform choice based on marketing rather than clinical indication is rarely the right approach.
When Platform Does Matter: The Real Distinctions
Body targets with significant respiratory motion (lung SBRT): CyberKnife's Synchrony tracking is genuinely clinically superior to respiratory gating on LINAC systems for many patients. Dedicated intracranial-only programme: Gamma Knife has the deepest evidence base and most established protocols for intracranial indications. Trigeminal neuralgia: Gamma Knife has decades of established protocols for the Gasserian ganglion approach.
Explore the SRS Knowledge Base
Related SRS topics.
- What Is SRS and How Is It Different from Regular Radiation?
- SRS for Brain Metastases: The Evidence That Changed Standard of Care
- SRS for Acoustic Neuroma: Radiation Over Surgery
- Stereotactic Radiosurgery — Full Treatment Page
- RFA vs Microwave Ablation (MWA): When Each Is Preferred
- Lung RFA for Early-Stage NSCLC and Pulmonary Metastases
Frequently Asked Questions
Common questions about choosing between SRS platforms.
About the Choice
My hospital has CyberKnife. Should I travel to a Gamma Knife centre for my brain metastases?
For most brain metastases indications, no. Multiple comparative studies show no meaningful difference in local control or toxicity between CyberKnife and Gamma Knife for brain metastases. The more important question is: how many brain metastases SRS cases does your hospital's radiation oncology team treat annually? If your hospital has a high-volume CyberKnife programme with experienced neuro-oncology MDT input, the outcomes will be equivalent to or indistinguishable from a Gamma Knife centre. Travel for a specific platform brand is rarely justified.
How CancerFax Helps
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For international patients, we help with practical coordination — travel planning, hospital admission guidance, and local support.
If this option is not suitable, we help explore other relevant treatments, clinical trials, or advanced care pathways.
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For informational purposes only. SRS platform and centre selection requires evaluation by qualified radiation oncology specialists.