Some Factors Influencing the Experimental Determination of Percentage Depth Doses for Medium Energy X rays

An assessment of GafChromic film for measuring 50 kV and 100 kV percentage depth dose curves

“…However, diodes have been found to need a perturbation correction factor (Li et al 1998b) and have a significant beam quality dependence. Diamond detectors and NACP chambers have been found to require relatively small depth-dependent corrections (Ma et al 2001) but Wood et al (1963) have reported that chamber size and heavy metal stems can affect the PDD at shallow depths. Li et al (1998a) suggest that diodes, PTW N23342, NACP and Markus chambers can be used to directly measure the PDD for 100 kV x-rays to within 3% uncertainty except at the surface.…”

Measurement of percentage depth dose and lateral beam profile for kilovoltage x-ray therapy beams

“…diode, TLD, film) and cylindrical and parallel-plate ionization chambers have been used (Harrison 1981, BJR 1983, Scrimger and Connors 1986, Niroomand-Rad et al 1987, Aldrich et al 1992, Kurup and Glasgow 1993, Gerig et al 1994, Aukett et al 1996. In the case of ionization chambers, it has been reported that the chamber size and a heavy metal stem can affect PDD at small depths (Wood et al 1963). For a 250 kVp x-ray beam, Cunningham et al (1986) and Knight and Nahum (1994) reported that the ratios of mass energy-absorption coefficient depend on beam size and depth in phantom.…”