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SRS with the CyberKnife® System

Precise robotic treatment as individual as every patient

With the first-and-only robotic-arm-mounted linear accelerator, the CyberKnife® System enables uniquely precise and versatile treatments of neurological indications.


True robotic precision with practical versatility

The CyberKnife® System leads stereotactic radiosurgery (SRS) innovation, combining state-of-the-art robotic architecture with fully integrated image guidance and continual, delivery adaptation and motion synchronization. This powerful combination enables frameless SRS targeting with sub-millimeter precision, while giving practices the versatility to make SRS efficient and practical for every patient, regardless of the disease complexity and location.

Demonstrated clinical benefits for intracranial indications

CyberKnife SRS has been proven precise and effective for a broad range of neurological indications including brain1-3 and spinal tumors4-6, meningioma7, acoustic neuroma8-10, pituitary adenomas12, vascular malformations13, and functional disorders14. CyberKnife frameless SRS also offers a precise, non-invasive treatment with clinical outcomes comparable to Gamma Knife frame-based SRS as demonstrated on patients treated with brain metastases1,2 and trigeminal neuralgia14.

Excellent clinical outcomes achievable with the CyberKnife® System for the treatment of Trigeminal Neuralgia

Motion Synchronization and Delivery Adaptation

The CyberKnife fully integrated image-guidance system continually acquires stereoscopic kV images during treatment, tracks motion and automatically adapts treatment delivery to synchronize the treatment beams position with detected changes in the targets position.15. The 6-axis robotic arm aims each beam of radiation taking into account any translational and rotational changes. All measured displacements are automatically corrected, regardless of how small, maintaining sub-millimeter accuracy15-18, preserving conformal dose distribution, and minimizing dose to the surrounding critical structures and normal tissues.

Frameless stereotactic targeting

The CyberKnife System enables stereotactic targeting without a stereotactic frame, enhancing patient comfort and simplifying the procedure. Simple immobilization devices such as thermoplastic masks, a foam cradle or vacuum bags keep the patient comfortably in treatment position and prevent large displacements that cannot be automatically adapted by the robotic arm.

Full-body SRS

The frameless CyberKnife technology unlocks unique versatility, enabling SRS treatments anywhere in the central nervous system—including along the spine. CyberKnife SRS has been shown safe and effective for primary and metastatic spine lesions with low rates of toxicity4-6.

Multi-session SRS

The frameless technology also facilitates multisession SRS, allowing for more precise treatment of lesions close to sensitive structures such as the spine5,6 and optic apparatus7-12. For acoustic neuroma 8-10, multisession SRS has shown excellent response and hearing preservation rate.

CyberKnife brain

Sharp dose gradient

The robotic design of the CyberKnife System seamlessly delivers non-coplanar, non-isocentric and isocentric beams. This wide range of available beam angles sculpts conformal dose distributions and enables safe and effective treatments regardless of the disease complexity and location. The CyberKnife System generates the sharp dose gradients required for lesions close to critical structures and minimizes dose delivered to normal tissues. Clinical data indicates that patients previously treated with CyberKnife SRS for brain metastases can be effectively treated with additional courses of SRS, thereby delaying or completely avoiding whole brain radiation therapy3.

Validated accuracy

The CyberKnife System uses proprietary anatomy-specific algorithms to track tumor motion. These specialized image guidance algorithm such as Synchrony® Skull Tracking, Synchrony® Spine Tracking Prone, and Synchrony® Spine Tracking Supine enable sub-millimeter precision and accuracy without the need for invasive and cumbersome stereotactic frame15-18. Academic institutions have independently validated the image guidance sub-millimeter accuracy.

Synchrony Skull Tracking, total system error:

  • 0.95 mm (Accuray Specification)
  • 0.48 ± 0.22 mm2
  • 0.30 ± 0.12 mm14
  • 0.44 ± 0.12 mm16

Synchrony Spine Tracking, total system error:

  • 0.95 mm (Accuray Specification)
  • 0.53 ± 0.16 mm16
  • 0.52 ± 0.22 mm17
  • 0.61 ± 0.27 mm18

Versatility in collimator options

The CyberKnife System offers a collection of available collimators, providing the versatility needed to treat a wide range of clinical indications from trigeminal neuralgia to large brain tumors.

  • Fixed Circular Collimators
  • Iris Variable Aperture Collimator
  • InCise Multileaf Collimator

Clinical Examples


Brain metastases:
1. Wowra B. et al. “Quality of radiosurgery for single brain metastases with respect to treatment technology: A matched-pair analysis.” J Neurooncol. 2009; 94: 69-77
2. Muacevic A. et al. “Feasibility, safety, and outcome of frameless image-guided robotic radiosurgery for brain metastases.” J Neurooncol. 2010; 97: 267-274
3. Shultz et al. “Repeat Courses of Stereotactic Radiosurgery (SRS), Deferring Whole-Brain Irradiation, for New Brain Metastases After Initial SRS.” International Journal of Radiation Oncology Biology Physics. 2015; 92: 993-999

4. Gerszten P.C. et al. “Radiosurgery for spinal metastases: Clinical experience in 500 cases from a single institution.” Spine. 2007; 32: 193-199
5. Gagnon G.J. et al “ Treatment of spinal tumors using CyberKnife fractionated stereotactic radiosurgery: pain and quality-of-life assessment after treatment in 200 patients.” Neurosurgery. 2009; 64: 297-306
6. Heron D.E. et al. “Single-session and multisession cyberknife radiosurgery for spine metastases-university of pittsburgh and georgetown university experience.” J Neurosurg Spine. 2012; 17: 11-18 –

7. Colombo F. et al. “CyberKnife radiosurgery for benign meningiomas: short-term results in 199 patients.” Neurosurgery. 2009; 64: A7-13

Acoustic neuroma:
8. Jumeau et al “Vestibular shwannomas treated with CyberKnife: clinical outcomes.” Tumori. 2016; 102: 569-573
9. Hansasuta A. et al. “Multisession stereotactic radiosurgery for vestibular schwannomas: Single-institution experience with 383 cases.” Neurosurgery. 2011; 69: 1200-1209
10. Casentini L. et al. “Multisession stereotactic radiosurgery for large vestibular schwannomas.” J Neurosurg. 2015; 122: 818-824 –
11. Cakir O. et al. J. Laryngol Otol. 2018; September 5: 1-6.

Pituitary adenomas:
12. Killory B.D. et al “Hypofractionated CyberKnife radiosurgery for perichiasmatic pituitary adenomas: Early results.” Neurosurgery. 2009; 64: A19-25

Arteriovenous malformations:
13. Colombo F. et al. “Early results of CyberKnife radiosurgery for arteriovenous malformations.” J Neurosurg. 2009; 111: 807-819

Trigeminal neuralgia:
14. Romanelli P. et al. “Image-Guided Robotic Radiosurgery for Trigeminal Neuralgia” Neurosurgery. 2017; Nyx571 –

CyberKnife System accuracy:
15. Kilby W. et al. “The CyberKnife® Robotic Radiosurgery System in 2010” TCRT. 2010; 9(5): 433-452 –

16. Antypas C. and Pantelis E. “Performance evaluation of a CyberKnife G4
image-guided robotic stereotactic radiosurgery system.” Phys Med Biol.
53:4697-4718, 2008
17. Muacevic A. et. al. “Technical description, phantom accuracy, and clinical feasibility for fiducial-free frameless real-time image-guided spinal radiosurgery” J Neurosurgery Spine. 2006; 5(4): 303-312 –
18. Ho et. al. “A study of the accuracy of cyberknife spinal radiosurgery using skeletal structure tracking” Neurosurgery. 2007; 60: 147-156

Technology naming information:
In April 2020 Accuray expanded the use of the Synchrony® brand name. As such, please be advised that the names for motion tracking and correction algorithms referenced in clinical publications may be different that current naming. Below you will find information on those name changes so that you may find the appropriate reference in existing clinical literature:

Synchrony Skull Tracking was called 6D Skull Tracking
Synchrony Spine Tracking Prone was called Xsight® Spine Tracking (in the prone position)
Synchrony Spine Tracking Supine was called Xsight® Spine Tracking (in the supine position)

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