A needed modification to vendor supplied oversized 45 degree wedges.
A recent change in the source-to-blocking tray distance on at least one new linear accelerator restricts simultaneous use of the vendor supplied oversized (i.e., 20 cm) 45 degree wedge and 7.5 cm or higher custom cerrobend blocks. Truncating the "heel" end of the vendor supplied steel wedge as well as substituting a 45 degree lead wedge (designed and supplied by the vendor) allows simultaneous wedge and 7.5 cm high block usage. Central axis depth dose, transverse dose profile, wedge transmission factor, and surface dose measurements were made for each wedge for 6 through 18 MV x-rays. Dosimetric data for the truncated steel wedge is insignificantly different from that of the untruncated steel wedge, whereas the lead substitute wedge dosimetric data is substantially different and requires remeasurement.
Mellenberg
D E
DE
Division of Radiation Oncology, Mayo Clinic, Rochester, MN 55905.
McCullough
E C
EC
D006801:Humans; D010315:Particle Accelerators; D011882:Radiotherapy, High-Energy / Q000295:instrumentation*; D013232:Steel
D013232:Steel