Acceptance tests form an important part of machine installation procedures. Acceptance tests were carried out on CLINAC-1800 accelerator installed at KMIO, as recommended by Varian Associates, U.S.A. in accordance with the German Standard DIN 6847. The tests included radiation survey, mechanical tests, radiation isocenter test, photon beam performance, electron beam performance and dosimetry tests. The results of these acceptance tests were very satisfactory- Tests such as depth dose, field flatness, field symmetry constitute routine quality assurance programme for an accelerator.

Postal Quality Assurance tests carried out by the Saskatchewan Government's Radiation Safety Unit during the last two years have proven very reliable and economical. This has the potential to identify the performance of rapidly deteriorating X ray tubes and other imaging problems and take prompt corrective action.

In electron beam treatment introduction of a metal sheet under the tissue to shield vital organs increases the dose to the tissue at the junction due to the back scattering of electrons from the metal. Investigations were made to observe this effect for electron energies from 9 to 20 MeV. It was found that the increase in the relative ionisation is from 26 to 50 percent at the tissue-lead junction. The range of the back scattered electrons for each electron energy was determined by introducing polystyrene (density = 1.02 gm/cc) and wax sheets between the ionisation chamber and metal. A 1.0 gm per sq. cm thick wax sheet (density = 0.85 gm/cc) reduces the relative ionisation to 101, 102.6, 106.6 and 106% for 9,12,16, and 20 MeV electron beams respectively.