[Distribution of linear accelerators in Great Britain. Use of fast electrons and their main applications]

The features of the electron beam that make it a unique therapeutic tool, are related to physical characteristic rather than to any special biological effectiveness. The advantages of the dose distribution pattern are greatest at low energies (under 20 MeV), suggesting the use of electrons for irradiation of superficial tumors with the sparing of underlying tissues. Modern clinical electron practice demands electron treatment beams offering a high degree of purity, uniformity and the steepest possible fall-off of dose beyond the treatment volume. There are approximately 135 Linacs installed in UK, and approximately half of them have electron capacity with range of energy between 4 and 15/20 MeV. Compared to photon beams, 10% of treatment load is for electrons with a maximum of 15% in very specialised centres.