Stereotactic Image Guidance in Brain Surgery

Introduction StealthStation
 Gamma Knife CyberKnife Links & References
 
Gamma Knife®
 
In many cases, invasive neurosurgery is not an option, because a tumor or other abnormality is located deep within the brain, surrounded by other delicate critical areas. Radiosurgery is an enabling technology that can treat tumors which may have been otherwise termed inoperable. Radiosurgery allows a neurosurgeon to operate on the brain without a scalpel and without opening the skull, thus direct visualization is not possible, and localization of surgical area completely relies on image guidance.  In radiative treatment, an array of radiation beams, converging from many different directions, can be focused on the target with a fraction of a millimeter precision.



Gamma Knife was originally developed by Swedish neurosurgeon Lars Leksell in 1967, and is currently commercialized by Swedish company Elekta. Gamma Knife technology combines images from stereotactic CT, MRI, positron emission tomography (PET), magnetoencephalography (MEG), and/or cerebral angiography, and uses them for target determination and radiation beam focusing. Gamma Knife is primarily targeted for brain tumors (both benign and malignant), but is also used in treatment of arteriovenous malformations, trigeminal neuralgia, acoustic neuromas, and pituitary tumors.

        


Gamma Knife system consists of the following major components:
- Radiation unit that contains more than 200 cobalt-60 sources of gamma radiation, placed in a circular array of a heavily shielded assembly;
- Beam-focusing unit with tungsten collimators, which focuses radiation beams at multiple target points in a highly conformal way, minimizing the risk of damage to brain tissue outside of targets;
- Patient couch with electric bed system and precise robotic motion control, which positions the patient’s head at the focus point with accuracy of less than 0.3 millimeter;
- Control console and planning computer system, which analyzes preoperative imaging data and performs the stereotactic guidance and planning of beam trajectories.

What future directions and challenges may be pursued by biomedical engineering with respect to this technology?
- The system could be integrated with intraoperative imaging systems.
- With current systems, the patient is required to wear a specialized helmet that is surgically fixed to the skull in order to eliminate any motion of the focal area. Future systems could track motion in real-time and compensate for it with adaptive beam forming.