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To better understand how CyberKnife works, it is helpful to understand the technology of radiosurgery. Stereotactic radiosurgery (SRS) combines the principles of stereotaxy, or 3-D target localization, with multiple cross-fired beams from a high-energy radiation source to precisely irradiate an abnormal (oftentimes cancerous) lesion within a patient's body. The ideal objective is the destruction of the targeted area without damaging any normal tissue outside of the defined target area.

Radiosurgery and conventional radiotherapy are often confused.

Radiosurgery Radiotherapy
Description Focused radiation delivered precisely to the target sparing surrounding normal tissue Large field radiation delivered to the target and surrounding normal tissue
Typical Dose Per Treatment High dose (~ 6 to 25 Gy per treatment) Low dose (~ 2 Gy per treatment)
Typical Treatment Duration 1 - 5 treatments 30 - 40 treatments

Would you rather 4 vs. 40 Treatments? Stereotactic radiosurgery differs from conventional radiotherapy in several ways. Because radiotherapy does not achieve the same level of accuracy, normal tissues are protected by administering the radiation dose over multiple sessions (fractions) daily for a period of a few to several weeks. In contrast, radiosurgery utilizes highly destructive doses of radiation administered in one to five (1-5) daily fractions. The key to the success of SRS is its ability to precisely target the tumor, firing these high dose beams from multiple angles to avoid sensitive structures (nerves, sensitive areas of the brain, etc.) even as the tumor moves (due to patient movement, breathing, etc.).  Prior to CyberKnife, the accuracy of SRS relied on the use of a rigid metal frame fixed to a patient's skull, immobilizing the head to prohibit movement and minimize damage to the surrounding healthy tissue. This procedure is very effective, but has considerable drawbacks, including the fact that treatment is restricted to only the head.

The CyberKnife radiosurgery system takes this procedure to the next level, eliminating the need for a head frame and allowing CyberKnife to treat tumors anywhere in the body. Perhaps more importantly, CyberKnife is uniquely capable of providing real time monitoring of the target throughout treatment using an advanced image-guidance system, and is able to detect and correct during treatment for some target motion (e.g. due to small patient movements, breathing, coughing).

Stereotactic radiosurgery has been used for more than 30 years to treat benign and malignant tumors, vascular malformations, and other disorders of the brain with minimal invasiveness.

Safe delivery of these radiosurgical high doses require a different treatment delivery technique than the conventional radiotherapy devices. Would you rather treatment with 4 high dose treatments for a chance to cure, control growth, or get pain relief vs. 40 lower dose treatments over several weeks?

CyberKnife provides the means to get the highest dose of radiation to the target with continual detection and correction throughout treatments with no pain, no incision, and little to no recovery time or side effects - allowing you to get back to your life.

Radiosurgery vs. Radiotherapy

Targeting tumors that move with respiration.

CyberKnife Robotic Radiosurgery System

  • Beams move in real-time with 3D target motion
  • Dose delivered continuously throughout the breathing cycle

Conventional Radiotherapy Systems

  • Limited system mobility requires the beam to repeatedly turn on and off as the target moves through fixed cross-hairs

Ring Gantry Radiotherapy Systems

  • Delivers high doses of radiation to the entire envelope of target motion - encompassing both healthy and cancerous tissues

Treatment Comparison

There are several devices, modified linear accelerators (linac) systems, in our area that are capable of delivering radiation, but that do not automatically and continuously adapt to tumor motion caused by organ movement or breathing and require more multi week treatment sessions vs. 1-5 sessions or "fractions" with CyberKnife. The number of fractions depends on several factors, including the size of the lesion, location in the body, and your unique treatment plan developed by the multidisciplinary practitioners

CyberKnife Gamma Knife Other Linac Systems(ie., Novalis, Varian Trilogy, TomoTherapy)
Continuously adapts to lesion motion caused by organ movement Yes N/A No
Continuously adapts to lesion motioncaused by breathing (respiratory tracking) Yes N/A Varian Trilogy uses respiratory gating but does not track with radiosurgical precision; other systems do not adapt to breathing
Radiosurgery dedicated Yes Yes No
Also does "conventional" radiotherapy No No Yes
Anatomic area treatable with radiosurgical precision Brain,spine, entire body Brain Brain, possibly other areas, depending upon system
Rigid brain or body frame required for accuracy No Yes Yes
Lesion size limitation No Yes No
Capable of divided treatments to better preserve adjacent tissues Yes No Yes

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