Ned,
I beleive the Peacock system is an IMRT system ( Intensity Modulated Radiation Therapy) whereas the CK isan active targeting SRS system. Both are Linac and both are very effective in treating Skull based tumors. Here is a one discussion of there advantages and disadvantages:
Shaped Beam Systems
The recent development of IMRT or Intensity Modulated Radiation Therapy has added another dimension to multi-fraction radiation therapy. These linac-based technologies use computer-controlled "beam-shaping" to do a better job of conforming the radiation dose to the shape of the tumor or other lesion. This form of advanced radiation therapy can be utilized at virtually any location in the body. IMRT technology enables a mechanical device (called a multi-leaf collimator) that is typically attached to most modern medical linear accelerators, to dynamically reshape the outlines and intensity of the radiation field during cancer treatment. When combined with sophisticated planning software, IMRT fits the dose of radiation to a target much better than conventional radiation therapy, and thereby minimizes the volume of surrounding normal tissue that is injured by treatment. While it appears that IMRT may produce fewer side-effects than conventional radiation therapy, IMRT is not as spatially precise as radiosurgery. Because of this imprecision, a full course of IMRT treatment is typically administered over multiple treatment sessions (typically 20-30+). Common brand names include X-Knife (Radionics) and Novalis (Brain Lab). Advantages of Shaped-Beam systems include:
1. The capacity to treat most regions of the body with IMRT
2. When coupled to an invasive stereotactic frame, precision targeting for brain tumors that approaches, but does not equal, that of the Gamma Knife or CyberKnife.
3. The capacity to more accurately target extracranial (non-brain) tumors than standard radiation therapy
4. An ability to deliver fractionated intracranial or extracranial treatment
Disadvantages of the Shaped Beam systems include:
1. The need for an invasive head frame (similar to the Gamma Knife) to assure treatment accuracy when used for brain radiosurgery (single fraction)
2. Less treatment accuracy when multiple fractions are used to treat areas of the brain where the use of an invasive head frame is impractical
3. A significantly lesser degree of targeting accuracy when treating extracranial tumors compared to brain radiosurgery
4. Treatment accuracy is degraded further when the target moves during radiation delivery from either natural breathing or patient movement
CyberKnife System
The CyberKnife System is an SRS system utilizing contemporary technology that is designed to be the most accurate and flexible tool available for aggressive therapeutic irradiation. The CyberKnife was designed to address the limitations of frame-based SRS systems and expands the application of radiosurgery to sites outside of the head. It is the only system to incorporate a miniature linear accelerator mounted on a flexible, robotic arm. An image-guidance system that can track target location during treatment also enables the CyberKnife to offer superior targeting accuracy without the need for the invasive head frame. While Gamma Knife and linac-based systems can perform radiosurgery in the brain, true radiosurgery for areas outside of the brain is difficult if not impossible to perform with these systems. For more detailed information on the CyberKnife, see CyberKnife Overview.
Advantages of the CyberKnife include:
1. No invasive head frame or other rigid immobilization device is required
2. The ability to perform radiosurgery (1-5 fractions) on targets throughout the body, not just the brain
3. Precise targeting (within 1 mm) of selected lesions in the brain and body
4. A unique ability to provide real time monitoring of the treated target throughout treatment using an advanced image-guidance system
5. A unique ability to correct during treatment for limited target motion (e.g. due to small patient movements)
6. The capacity to easily perform staged radiosurgery
Disadvantages of the CyberKnife include:
1. The need for placement of very small markers (fiducials) via a needle for the treatment of targets outside of the head
2. Compared to other radiosurgical devices, treatment takes longer when multiple tumors are ablated during the same treatment session.
