EVIDENCE FOR A SIGNIFICANTLY HIGHER THAN EXPECTED DEPTH DEPENDENCE OFWEDGE TRANSMISSION FACTORS ON THE 4 MV BEAM OF A NEW DUAL-ENERGY ACCELERATOR

Wedge transmission factors have been measured for two sets of physical wedges for the 4 MV beam of a new dual energy linear accelerator as a function of field size and depth. The field size dependence of these factors has been compared with the 4 MV beam from another, single-ener gy linear accelerator and a difference of a factor of approximately 2 has been observed in the relative wedge transmission factors between t he two machines. (C) 1998 American Association of Physicists in Medici ne. [S0094-2405(98)00411-8].