It consists of two opposing banks of leaves, either side of the central axis of the beam. These consist of a pair of MLC banks 7, designed to collimate the beam to any desired irregular shape (such as the outline of a tumour). The beam thus created has a standard shape, which is then tailored to the specific needs of the treatment being delivered at that instant by collimators 7, 8, 9. An ion chamber 5 allows the beam properties to be monitored, and a wedge filter 6 provides further control of the beam properties. Filters 3 and 4 then remove unwanted wavelengths from the beam and flatten its intensity profile. These are delimited by a primary collimator 1 comprising a substantial block of x-ray attenuating material such as tungsten with a conical through-aperture centred on the x-ray source 1. High-energy electrons are directed toward an x-ray target 1 in order to generate therapeutic x-rays of (typically) 1-4 MeV. 1 shows the general layout of the essential functional parts of a radiotherapy source. Whilst it is impossible to completely prevent the irradiation of healthy tissue, given that some tissue will be in front of or behind the lesion, the amount of healthy tissue that is irradiated is generally minimised by careful collimation of the beam and planning of the treatment.įIG. The radiation is also capable of causing harm to surrounding healthy tissue, albeit at a slightly lesser rate in the case of cancerous lesions. That radiation is partially absorbed by the lesion, causing cell damage which inhibits growth of the lesion and/or causes it to reduce in size. Radiotherapy consists of the treatment of tumours and other lesions by directing harmful radiation towards the site of the lesion. The present invention relates to improvements in the apparatus and related processes for the delivery of radiotherapy. 28, 2011, which is incorporated herein by reference. This application is a continuation of Patent Cooperation Treaty Patent Application PCT/EP2011/002130, filed Apr.
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