Radiotherapeutic physics. VII. An instrument for dosage estimation with fields of any size and shape.
In the preceding paper in this symposium the need was stressed for a system of dosage estimation with beamed radiations of more general application than those at present use, and in particular one that could be used for the routine estimation of dose with fields of irregular shape. Brief mention was made of a machine which could fulfil this function, and the purpose of the present paper is to describe more fully the construction and mode of operation of this device. The basic principle of the device is one which has been discussed by various workers—that the analysis of the way in which the dose of scattered radiation at given points on the central axis of a circular field varies with field diameter can be made the basis of the estimation of dose at any point of the volume irradiated by an irregularly shaped field. The essential procedure in this estimation has in the past been one of integration, graphical or otherwise, of a rather cumbersome nature and not well fitted for routine work. However, in the p...
Physical Aspects of Roentgen Therapy Using Wedge Filters
The essentisl features of the dose distribution in a two- or three-field wedge arrangement may be extracted in the form of: mean percentage tumor dose, location of a defined plateau'' relative to a base-line, and hotspot factor,'' i.e., maximum skin dose/mean tumor dose. The following variables are studied: angle between wedges, separation of wedges, width of the normal field, width of the wedge field, and the slope and shape of the wedge isodose lines. The results of the analyses can be presented as dosage tables'' which facilitate a rapid choice of configuration in individual cases. (auth)
Coherent pulsed injection seeding of two gain-switched semiconductor lasers
High-power, narrow-spectrum, short pulses at a wavelength near 830 nm are needed for optical logic applications. The authors report the generation of two coherent trains of pulses by pulsed injection seeding of two gain-switched semiconductor lasers with one mode-locked master oscillator. The available power was doubled and both lasers emit in nearly identical spectral lines. Short pulses (30-50 ps) are generated at a repetition rate of 1.9 GHz. The spectrum is reduced to a single mode cluster and shows a 1.7 AA wide chirp suitable for pulse compression. The peak power is 0.1 W for each pulse train. The capability of this technique for coherent power combining is demonstrated.<<ETX>>