Gamma Knife Radiosurgery: An Overview of Physics, Chemistry, Biology and Neuro-medicine

Abstract

The gamma knife is a highly specialized treatment unit that
provides an advanced sophisticated stereotactic approach
to treatment of tumour and vascular malformations within
the internal structure of the head. The gamma knife delivers
a single high dose of radiation emanating from 201 cobalt-
60 unit sources. All 201 beam simultaneously intersect at
the same time in a pre-defined location. The treatment
planning system for gamma knife radiosurgery has been
developed using nonlinear programming techniques. The
system optimizes the shot sizes, location and weights for
gamma knife treatments. Open stereotactic technique in the
1990’s was essential for the treatment of a number of
functional conditions and cystic space occupying lesions.
It has an important part to play in the investigation of
tumours and can help to increase the number which are
accessible to treatment. It can be employed to guide not
only solid instruments but also ionizing irradiation to “masslesion
– targets”. It is just this combination of stereotactic
guidance and narrow beam, high energy radiation to
precisely defined target, is the basis of gamma knife
radiosurgery . The topic on radiological physics presents a
broad field, which includes physics of radiation therapy,
diagnosis and nuclear medicine. The emphasis is on the
basic physical principles which form a common foundation
for these areas. Consequently, the topic provides both basic
radiation physics, physical aspects of treatment planning
and use of radiation beams. Some knowledge of the effect
of ionizing radiation on living tissues is necessary, for those
who wish to understand the nature of any treatment using
radiation and who also wish to inform patients about such
treatment. The topic relates to the effects of radiation on
visible structures, in other words, cells and tissues. The
radiobiological knowledge described here has been
developed in relation to standard radiotherapy. Moreover,
the linear quadratic model of cell killing is also applicable
for single dose irradiation.

DOI: 10.3329/jbcps.v28i2.5370

J Bangladesh Coll Phys Surg 2010; 28: 100-112