Stereotactic Radiosurgery 

The Non-Invasive Neurosurgery


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Heisei Memorial Hospital     OENC

 
 

Introduction    Evolution    How Does it Work    Indications    Treatment Process    Advantage



How Does It Works :


Design : Leksell Gamma Knife Perfexion is dedicatedly designed to do stereotactic radiosurgery. During radiosurgery we diver highly precise beams of radiation on tumor. High energy Gamma rays are produced naturally from Cobalt 60 Isotope sources. Gamma Knife is equipped  bring 192 sources of Cobalt 60 arranged in a special collimator so that beam of gamma rays cross at a sharp focus. This generated a ball of radiation which delivers radiation similar to using hand lens in sunlight  to burn a paper. This special design helps in bringing down radiation in vicinity of target to very low level due to sharp dose fall.

These beams make a focus of  4mm, 8mm and 16mm size depending upon selected collimator. as compared to previous versions in Gamma Knife Perfexion the collimators are inbuilt and automatically adjusted using robotic drives.




Radiobiology:  Gamma Rays are ionizing radiation, Gamma rays when exposed to tissue produce damage to the DNA in the cells which is important for cell reproduction. Thera re of 2 types. First is direct damage to the DNA molecules and second is indirect through Compton Scattering and development of free radicals in cell. As we know tumor is an uncontrolled growth. Due to DNA damage form Gamma rays there capability to produce new cells is lost immidiatly or over time. This stops growth of tumors and slowly tumor reduce in size and may disappear. Similar proliferative process damage happen in case of arteriovenous malformations. in functional disorders like Trigeminal Neuralgia the effect of radiation is manifested as loss of function.


In Radiosurgery a large fraction / dose of  radation is delivered in one session as compared to radiotherapy where treatment is divided in multiple session of low dose fractions . Due to this radiosurgery can produce more damage to tumor DNA then radiotherapy and need much lesser dose to give same resulted. Radiobiologiclaly such single large fraction is 2.5 time more effective then fractionated radiotherapy. Tumors which are resisted to radiotherapy can be treated by radiosurgery effectively.

 

Leksell Gamma Knife Perfexion

The Fifth Generation Robotic Gamma Knife