Experimental determination of depth-scaling factors and central axis depth dose for clinical electron beams.

Depth-scaling factors rho(eff) for clear polystyrene and polymethylmethacrylate (PMMA) phantoms have been determined experimentally as a function of nominal electron-beam energy in the range 6 to 22 MeV. Values of rho(eff) have been calculated from the ratio rho(eff) = R(wat)(50) / R(med)(50), where R(wat)(50) and R(med)(50) are the measured depths of 50% ionization in electron solid water and plastic (clear polystyrene and PMMA) phantoms, respectively. Measurements were made using an Attix chamber in an electron solid water phantom, a Holt chamber in a clear polystyrene phantom, and a Markus chamber in a PMMA phantom.

A generalized film technique for the verification of vertex fields used in the treatment of brain tumors.

With the availability of commercial three-dimensional (3D)-treatment planning systems, more and more treatment plans call for the use of noncoplanar conformal beams for the treatment of brain tumors. However, techniques for the verification of many noncoplaner beams, such as vertex fields which involve any combination of gantry, collimator, and table angles, do not exist. The purpose of this work is to report on the results of an algorithm and a technique that have been developed for the verification of noncoplanar vertex fields used in the treatment of brain tumors.

Experimental determination of fluence correction factors at depths beyond dmax for a Farmer type cylindrical ionization chamber in clinical electron beams.

Recently, it has been recommended that electron beam calibrations be performed at a new reference depth [Burns et al., Med. Phys.

Anisotropy of an 192iridium high dose rate source measured with a miniature ionization chamber.

The anisotropy of a high dose rate (HDR) 192Ir source was measured in air and in water using a miniature (0.147 cm3) ionization chamber. Measurements were made at a distance of 5 cm from the source center at polar angles from 10 degrees-170 degrees.