Measurements of surface dose and build-up have been measured for photon radiation sources with maximum energy from 1.2 to 25 MeV. A variable volume ionization chamber was used and the results extrapolated to what would be obtained with a zero volume chamber. The results are found to depend systematically on the plate separation of a parallel plate ionization chamber and an empirical method was derived for correcting measurements made with a fixed volume chamber. The relationship of dose build-up curves with skin reactions in radiation therapy patients is discussed.

Cobalt Radioisotopes↗

PubMedDate not supplied

Photon and electron response of silicon-diode neutron detectors.

The photon response of silicon-diode neutron detectors is analyzed theoretically and measured in the 15-25-MeV region. The main mechanism for producing a response in the diode is shown to be the displacement of silicon atoms by scattering of electrons. If the photon source is an electron accelerator target, the response is mostly due to electrons originating in the target with a smaller contribution from electrons produced in the diode by photons generated at small angles to the beam.

Electrons↗

PubMedDate not supplied

Stereo-photogrammetry for the determination of patient surface geometry.

A stereo-photographic system has been developed with which surface contours of a human subject may be obtained rapidly and objectively. Nonmetric cameras are used and the results are obtained from direct measurements of the photographs. Software has been developed for interpretation of the photographic data with the assistance of a small computer and desk-top digitizer such as those routinely used in radiotherapy treatment planning. With the system the coordinates of a point on the subject may be determined with an accuracy of +/- 1-2 mm.

Computers↗