ABSTRACT
According to the latest UNSCEAR Report (UNSCEAR 2008) for the period 1997-2007, the global use of radiation therapy increased to 5.1 million treatments from 4.7 million treatments in the period 1991-1996. About 4.7 million patients were treated with external beam radiation therapy, whereas 0.4 million were treated with brachytherapy. e availability of linear accelerators worldwide was about 1.6 machines per million people in the population, whereas the availability of x-ray machines and of cobalt units was about equal, at 0.4 per million people. In absolute numbers, UNSCEAR claims that in the period 1997-2007, the number of linear accelerators worldwide increased to about 9000 from about 5000 in the previous period. e 2009 IAEA Directory of Radiotherapy Centers shows the global distribution of high-energy machines, totaling 7177 clinical accelerators and 2505 Co-60 units (IAEA 2009). ere are no numerical data on the global distribution of GammaKnife and GyroKnife systems, but it is known that most of the GammaKnife units have been installed in level I countries, where most of the linear accelerators function and where 24% of the population received 76% of the total radiation therapy treatments (UNSCEAR 2008). (Level I countries are countries where there is at least one physician for every 1000 people in the general population.) Gyro Knife units are mostly working in China, where they were rst developed (Gammastar 2008).
