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.

Patient in need of intracranial stereotactic radio surgery (SRS) with the CyberKnife System from Accuray.

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, automatic 6D correction. 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 safe and effective for a broad range of neurological indications including brain1-3 and spinal tumors4-6, meningioma7, acoustic neuroma8-10, pituitary adenomas11, vascular malformations12, and functional disorders13. 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 neuralgia13.

Proven Safety And Efficacy Of The CyberKnife® System For The Treatment Of Trigeminal Neuralgia

Automatic 6D Correction

The CyberKnife fully integrated image-guidance system continually acquires stereoscopic kV images during treatment, tracks motion and automatically corrects the treatment beam alignment in real-time14. 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 accuracy14-18, preserving conformal dose distribution, and sparing 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 compensated by the robotic arm.

Illustration of frameless stereotactic targeting for brain cancer with the CyberKnife System from Accuray

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.

Multisession SRS

The frameless technology also facilitates multisession SRS, allowing for safer treatment of lesions close to sensitive structures such as the spine5,6 and optic apparatus7-11. 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. It generates the sharp dose gradient 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 safely and 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 algorithms enable sub-millimeter precision and accuracy without the need for invasive and cumbersome stereotactic frame14-18. Academic institutions have independently validated the image guidance sub-millimeter accuracy.

6D Skull Tracking, total system error:

  • 0.95 mm (Accuray Specification)
  • 0.48 ± 0.22 mm2
  • 0.30 ± 0.12 mm13
  • 0.44 ± 0.12 mm15

Fiducial Tracking, total system error:

  • 0.95 mm (Accuray Specification)
  • 0.29 ± 0.10 mm15

Xsight® Spine Tracking, total system error:

  • 0.95 mm (Accuray Specification)
  • 0.53 ± 0.16 mm15
  • 0.52 ± 0.22 mm16
  • 0.61 ± 0.27 mm17

Synchrony® Respiratory Tracking System, total system error:

  • 0.95 mm (Accuray specification)
  • < 0.6 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 tumors.

  • Fixed Circular Collimators
  • Iris Variable Aperture Collimator
  • InCise 2 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 –


Pituitary adenomas:

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


Arteriovenous malformations:

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


Trigeminal neuralgia:

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


CyberKnife System accuracy:

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

15. Antypas C. and Pantelis E. “Performance evaluation of a CyberKnife G4
image-guided robotic stereotactic radiosurgery system.” Phys Med Biol.
53:4697-4718, 2008

16. 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 –

17. Ho et. al. “A study of the accuracy of cyberknife spinal radiosurgery using skeletal structure tracking” Neurosurgery. 2007; 60: 147-156

18. Muacevic A. et. al. “Technical Description, Phantom Accuracy, and Clinical Feasibility for Single-session Lung Radiosurgery Using Robotic Image-guided Real-time Respiratory Tumor Tracking” TCRT. 2007; 6(4): 321-328 –

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