Cyber Knife


Mr. Jyothis John

Principal, Manoj Jain Memorial College of Nursing, Satna, Madhya Pradesh.

*Corresponding Author E-mail:



Cyber Knife System is a radiation therapy device manufactured by Accuray Incorporated. The system is used to deliver radiosurgery for the treatment of benign tumors, malignant tumors and other medical conditions. Despite its name, Cyber Knife treatment is not a surgical procedure. 1In fact, there is no cutting involved. The Cyber Knife System is a non-invasive alternative for delivering radiation with the high level of precision required for stereotactic radiosurgery (SRS). Neurosurgeons and radiation oncologists turn to the Cyber Knife System when more invasive techniques are deemed ineffective or too risky.2


KEYWORDS: Cyber Knife, radiosurgery, tumor, radiation, Gamma Knife.




Radiation therapy uses focused beams of intense energy to destroy cancer cells and shrink or control the growth of tumors. Radiation therapy works by preventing targeted cells from multiplying. The objective of radiation therapy is to destroy the harmful cells while minimizing damage to healthy cells.3 The Cyber Knife System was invented by John R. Adler, a Stanford University professor of neurosurgery and radiation oncology, and Peter and Russell Schonberg of Schonberg Research Corporation. The first system was installed at Stanford University in 1991 and was cleared by the FDA for clinical investigation in 1994. After years of clinical investigation the FDA cleared the system for the treatment of intracranial tumors in 1999 and for the treatment of tumors anywhere in the body in 2001. The Cyber Knife System was designed for both high-precision radiosurgical and Stereotactic body radiation therapy SBRT procedures.4


What is the Cyber Knife System:

The Cyber Knife System is a non-invasive treatment for cancerous and non-cancerous tumors and other conditions where radiation therapy is indicated. It is used to treat conditions throughout the body, including tumors of the prostate, lung, brain, spine, head and neck, liver, pancreas, kidney, and certain gynecologic indications, and can be an alternative to surgery or for some patients who have inoperable or surgically complex tumors. With the Cyber Knife, fully robotic radiation delivery system, the robotic design, coupled with real-time imaging, enables the Cyber Knife System to deliver a maximum dose of radiation directly to the tumor from many different angles with sub-millimeter precision. The Cyber Knife System does this by tracking and adjusting for tumor or patient movement during treatment to minimize radiation exposure to healthy organs and tissues.1



The device combines a compact linear accelerator mounted on a robotic manipulator, and an integrated image guidance system. The image guidance system acquires stereoscopic kV images during treatment, tracks tumor motion, and guide the robotic manipulator to precisely and accurately align the treatment beam to the moving tumor. The system is designed for stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT). The system is also used for select 3D conformal radiotherapy (3D-CRT) and intensity modulated radiation therapy (IMRT).4


How is the Cyber Knife System Different?:


Precision through Robotic Architecture:

The Cyber Knife System uses a robot that bends and moves around the patient. It can approach the target from hundreds of unique angles, significantly expanding the possible positions from which radiation beams can be delivered. The more degrees of freedom – the angles and points in space from which to approach the tumor – the better the radiation beams can be sculpted to avoid critical anatomical structures.1


Precision through Motion Management:

Many things happen from the time a patient has been set up on the treatment couch and radiation is delivered. The patient could change their position. The patient could cough. Muscles tense and relax. Fluids and gasses displace internal organs. The patient breathes. The Cyber Knife System is designed to accommodate all forms of patient and tumor motion, even while the treatment is being delivered. With its motion management technology, the Cyber Knife System enables smaller treatment margins around the tumor, minimizing the amount of healthy tissue exposed to high-dose radiation.1


Cyber Knife Motion Management:

The Cyber Knife System uses advanced technologies to track tumors anywhere in the body, while its unique robotic design keeps the radiation on target even while the tumor moves. Before delivering the radiation beam, the Cyber Knife System verifies the exact tumor position and adjusts the robot to precisely target the tumor. This ensures radiation is delivered to where the tumor is, not to where it was moment’s before.1


Synchrony Respiratory Tracking System:

The Synchrony Respiratory Tracking System is the only clinically proven system that uses continual image guidance to synchronize the movement of the radiation beam with the movement of the target while the patient breathes normally. The Synchrony Respiratory Tracking System enables patients to breathe naturally throughout the treatment. This highly sophisticated technology locks the robot motion on to the target so that the robot follows the patient's every breath. Besides delivering the radiation with greater precision, the Cyber Knife System removes the necessity for breath-holding or chest immobilization, making the treatment more comfortable for patients who may have compromised lung function.1



Non-cancerous tumours:

Cyber Knife is a good option for ablative dosages that can be used as a valid alternative to surgery. Like Gamma Knife, Cyber Knife works on a delivery of very high ablative dosages in a single or small number of sessions with precisions equal to or even more than Conventional Gamma Knife procedure. It has benefits of being non-invasive and does not need anaesthesia or blood loss. Apart from being used as an alternative to surgery, Cyber Knife is also indicated for post-op residual or recurrent cases. Also, it can be used as a boost to Conventional Radiation.2


Brain cancer:-

Cyber Knife is used as a boost, for post-op residual or recurrent cases in malignant gliomas/glioblastomas. Brain tumours that may form good indications for Cyber Knife radiosurgery include neuromas arising from other nerves, pituitary adenomas, hemangioblastomas and meningiomas, hemangiopericytomas.2


Prostate cancer:-

The challenge in treating prostate tumours with radiation is that the prostate moves unpredictably as air passes through the rectum and as the bladder empties and fills. The Cyber Knife Robotic Radiosurgery System is able to overcome this challenge by continuously identifying the exact location of the prostate in real time during the treatment and making active corrections for any movement of the prostate throughout the course of the radiation delivery. During treatment, a patient lays still and breathes normally while the Cyber Knife zeroes in on a moving target, the prostate, and irradiates it without harming the surrounding areas. As a result, the procedure is more comfortable for patients, radiation is delivered more accurately and treatments can be completed in three to five sittings.2


Liver cancer:

Treating liver cancer with radiation therapy is a challenge because liver tumours move with respiration. In addition the tissue surrounding the liver tumours is very sensitive and can be damaged easily. The Cyber Knife Radiosurgery System is able to deliver very high doses of radiation to both primary (before or after a liver transplant or in conjunction with chemotherapy or other treatments) and metastatic liver tumours with extreme accuracy. Working in conjunction with the Cyber Knife System is the Synchrony Respiratory Tracking System, which enables the radiation beam to track tumour movement in real time and allows patients to breathe normally during their treatment sessions.2


Cancerous tumours in spine:

Cyber Knife is a good option sparing normal spinal cord with more precision than most of the other radiation delivery techniques. For local therapy in spinal tumours, Cyber Knife can deliver highly focused radiation-sparing the surrounding normal tissues to a much greater extent.2


Lung cancer:

Cyber Knife is useful in treatment in early stage Lung Cancers when it is limited to a small area and can be used as an alternative to Radical Surgery. Cyber Knife is also useful in cases of Lung Metastasis or post primary therapy limited residual or recurrent disease, when it can be targeted by the Cyber Knife machine, as assessed by the Oncologist. The benefit of Cyber Knife lies in delivery of radical ablative dose that can control the disease in a totally non-invasive mode. It has special capabilities of tracking the tumour while respiration and thus can treat with minimal extra margins and thus decreasing the side effects very efficiently.2


Head and Neck Cancer:-

Cyber Knife can be used as boost to small critical area close to the eyes or other vital areas to decrease the dose going to the vital areas and subsequent side effects. Cyber Knife is also indicated for post-primary therapy residual and recurrent disease or Neck node residual or recurrent disease.2


Breast Cancer:

Sometimes in localised early stage Breast Cancers, Cyber Knife can be used as a very short course Radiotherapy that can just target the post operative surgical site. It is although possible only in selected cases and only treating oncologist can take this decision based on all available records and stage of the patient. Cyber Knife can also be used in metastatic cases where disease has spread from the Breast to other organs like Lung, Brain, Bone or Liver and is still limited that is lesser in number (< 6) or small size (< 6 cm). It cannot be used if there is gross widespread disease.2



Patient Comfort:

The Cyber Knife System is a leading technology in a targeted type of radiation delivery called stereotactic radiosurgery (SRS) or stereotactic body radiation therapy (SBRT). SRS/SBRT is widely used for treatment of brain metastases, and other benign and malignant brain tumors. The Cyber Knife System is a frameless radiation delivery system. With other technologies, immobilization devices, such as a frame bolted to the patient’s skull are used to prevent movement. The Cyber Knife System is designed to automatically adjust for movement and therefore does not require a frame. The Cyber Knife System has been proven to deliver radiation to the skull with sub-millimeter precision; to within 4 which means minimal radiation is delivered to the surrounding healthy brain tissue.1


Alternate to Surgery:

Treatments with the Cyber Knife System are non-invasive and pain free. In some cases, Cyber Knife radiosurgery may be an alternative to traditional surgery. It does not typically require anesthesia or an overnight hospital stay, and eliminates the recovery time and risks associated with surgery.1


Convenient Treatment Schedule:

Because treatments with the Cyber Knife System can be spread out over more than one session, it can treat patients who could not be treated with frame-based systems, such as the GammaKnife.  As compared with single session radiosurgery with the GammaKnife, treatment with the Cyber Knife System can be spread out over two to five sessions, which may result in fewer side effects.1



1. Cyber Knife Team:

Treatment with the Cyber Knife System involves a team approach, in which several specialists participate. Treatment team may include: A surgeon, A radiation oncologist, A medical physicist, A radiation therapist, A dosimetrist, Medical support staff. Once the team is in place, the patient will begin preparation for Cyber Knife treatment.1


2. Preparation:

Depending on your diagnosis, you will undergo some type of imaging which could include CT, MRI or PET scans to help the medical team determine the exact size, shape and location of the tumor. A team of doctors, including radiation oncologists, medical oncologists and surgeons along with medical physicists, radiation technicians and nurses work together to define the care plan for the patient.1


3. Treatment Plan:

Images from MRI, CT or CT/PET scan are digitally transferred to the CyberKnife’s treatment planning workstation, where specialists identify the tumour to be targeted and its surrounding vital structures to be protected. The plan is designed to match the desired radiation dose for the tumour and limit exposure to the surrounding healthy tissue. The Cyber Knife System then calculates the optimal radiation delivery plan, leveraging its extreme maneuverability to deliver a safe and accurate treatment1


4. Fiducial Placement:

Depending on the type and location of the tumour, fiducials (small golden markers) are inserted to determine the exact location of the tumour.2


5. During the Procedure:

During treatment, the Cyber Knife System’s computer-controlled robot will move around your body to various locations from which it will deliver radiation. At each position, it will stop to determine precisely where the radiation should be delivered. Nothing will be required of you during treatment, except to relax and lie as still as possible. The patient undergoes 1 to 5 sessions, depending upon the severity and location of the tumour. Each session may last approximately for 1 hour.1


6. Post-treatment:

Most patients experience minimal side effects and can quickly return to their daily routines with little interruption to their normal activities. Doctors will discuss all possible side effects prior to treatment and may prescribe medication to control any side effects, should they occur.1


7. Retreatment:

Because it can precisely target tumors, the Cyber Knife System may provide a safe radiation treatment option even for some previously irradiated patients.1



A painless treatment procedure that requires no anaesthesia, The technology is non-invasive and involves no blood loss, Minimum exposure of healthy tissues to the harmful radiations, Suitable for treatment of many tumors or lesions throughout the body, including soft tissue, spinal, head and neck and intracranial cases, Little to no recovery time, Surgically precise targeting (sub-millimeter clinical accuracy), Appropriate treatment for some patients diagnosed with inoperable or untreatable tumors or other lesions. Does not require hospitalisation; patients can immediately return to daily activities, No or minimal complications for patients post procedure1,2



Most side effects are minimal and last only a short time. Possible side effects could include: Nausea, Fatigue, Headache, Injury to nearby tissues1,2


Clinically Proven:

A research findings by Zhiyong Yuan (2013) done in 26 patients treated with tumor-free cutting edge (R0) surgical excision and 22 patients treated with Cyber Knife treatment. The results showed that the adverse effects of Cyber Knife were milder, with 1-, 2-, and 3-year local control rates of 92.9%, 90.0%, and 67.7%, respectively. The overall survival rates of the surgical treatment were 88.5%, 73.1%, and 69.2% for the same periods, while those of Cyber Knife treatment were 72.7%, 66.7%, and 57.1%, respectively.5


Research study done by Jeffrey W. Degen (2005) in patients with spinal tumors who underwent Cyber Knife radiosurgery were analyzed. Patients underwent examination, visual analog scale pain assessment, and completed the 12-item Short Form Health Survey  before treatment and at 1, 3, 6, 8, 12, 18, and 24 months following treatment. Fifty-one patients with 72 lesions (58 metastatic and 14 primary) were treated. The mean follow-up period was 1 year. Pain was improved, with the mean VAS score decreasing significantly from 51.5 to 21.3 at 4 weeks (p < 0.001). This effect on pain was durable, with a mean score of 17.5 at 1 year, which was still significantly decreased (p = 0.002). Quality of life was maintained throughout the study period. After 18 months, physical well-being was 33 (initial score 32; p = 0.96) and mental well-being was 43.8 (initial score 44.2; p = 0.97). (The mean SF-12 score is 50 ± 10 [standard deviation].) Adverse effects included self-limited dysphagia (three cases), diarrhea (two cases), lethargy (three cases), paresthesias (one case), and wound dehiscence (one case).6


A research finding by Brian K. Roberts (2007) aim of this study was to determine the efficacy and tolerability of Cyber Knife stereotactic radiosurgery in acromegaly. Nine patients with active acromegaly were treated with radiosurgery using the CyberKnife. After a mean follow up of 25.4 months (range, 6–53 months), Cyber Knife radiosurgery resulted in complete biochemical remission in 4 (44.4%) subjects, and in biochemical control with the concomitant use of a somatostatin analog in an additional subject. Smaller tumor size was predictive of treatment success: baseline tumor volume was 1.28 cc 0.81, SD) vs. 3.93 cc 1.54) in subjects with a normal IGF-1 vs. those with persistent, active disease, respectively (P = 0.02). The mean biologically effective dose (BED) was higher in subjects who achieved a normal IGF-1 vs. those with persistent, active disease, 172 Gy3 (±28) vs. 94 Gy3 (±17), respectively (P,0.01).7


A research finding by Sandra Vermeulen (2011) a study done to assess  the Accelerated partial breast irradiation: using the Cyber Knife in the treatment of early breast cancer. 9 patients were treated with CyberKnife. Patients received a total dose of 30 Gy in five fractions (group 1, n = 2) or 34 Gy in 10 fractions (group 2, n = 7) delivered to the planning treatment volume defined as the clinical target volume (CTV) +2 mm. The CTV was defined as either the lumpectomy cavity plus 10 mm (n = 2) or 15 mm (n = 7). The cavity was defined by a T2-weighted non-contrast breast MRI fused to a planning non-contrast thoracic CT. The Cyber Knife Synchrony system tracked gold fiducials sutured into the cavity wall during lumpectomy. Treatments started 4–5 weeks after lumpectomy. The mean PTV was 100 cm3 (range, 92–108 cm3) and 105 cm3 (range, 49–241 cm3) and the mean PTV isodose prescription line was 70% for groups 1 and 2, respectively. The mean percent of whole breast reference volume receiving 100 and 50% of the dose (V100 and V50) for group 1 was 11% (range, 8–13%) and 23% (range, 16–30%) and for group 2 was 11% (range, 7–14%) and 26% (range, 21–35.0%), respectively. At a median 7 months follow-up (range, 4–26 months), no acute toxicities were seen. Study suggests the Cyber Knife is a suitable non-invasive radiation platform for delivering APBI with achievable normal tissue constraints.8


Study finding by Cheng Yu, (2004) to detect the Accuracy of Cyber Knife Spinal Radiosurgery. The purpose of this study was to evaluate the total system for clinically relevant accuracy of this approach. The clinically relevant accuracy was measured at three different Cyber Knife facilities using head and torso phantoms loaded with packs of radiochromic film and expressed as a displacement of the dose contours from the treatment planning. The mean clinically relevant error, as measured at three different Cyber Knife facilities, was determined to be 0.7 ± 0.3 mm, which did not vary with computed tomographic slice thickness in a range of 0.625 to 1.5 mm. The average treatment delivery precision was 0.3 ± 0.1 mm. Fiducial tracking error was less than 0.3 mm for radial translations up to 14 mm and less than 0.7 mm for rotations up to 4.5 degrees.9


What makes Cyber Knife so unique?:

·       Unrivalled accuracy: The Cyber Knife system can treat moving tumours with pinpoint accuracy, which is unmatched by other radio surgery systems. This is especially important when treating tumours that move with anybody function (e.g; breathing).2

·       Unlimited flexibility and freedom: The Cyber Knife system’s robotic manoeuvrability allows doctors to deliver highly individualised treatments. With a linear accelerator mounted on a flexible robotic arm, Cyber Knife clinicians can select various angles targeting the tumour with a high dose of radiation from every conceivable angle.2

·       Real-time image guidance: The Cyber Knife uses a very sophisticated 6D image guidance system to track and continually adjust treatment for any movement of the patient or tumour.2

·       Convenient: Depending on the type of tumour, patients need only one to five Cyber Knife treatments, typically lasting less than an hour each, while other radiation systems require dozens of treatments spread over several weeks.2

·       Patient safety: Unlike other gantry based linear accelerators, the Cyber Knife operates on a fully integrated closed loop system. Each function works in unison to ensure the safest possible patient experience.2







5.      National Center for Biotechnology Information, published online 2013 Oct 29,

6.      Journa;l of neurosurgery, published on 2005,

7.      Pituitary online journal, publishe on March 2007,

8.      Frontiers in oncology, online research article;published on 2011 November 21,

9.      Neurosurgery online journal; Volume 55, Issue 5, 1 November 2004, Pages 1138–1149,





Received on 26.06.2019          Modified on 20.07.2019

Accepted on 08.08.2019     © A&V Publications all right reserved

Int. J. Nur. Edu. and Research. 2019; 7(4): 633-637.

DOI: 10.5958/2454-2660.2019.00143.1