Bragg-Gray Dosimetry : Theory of Burch

• The theoretical approach to Bragg-Gray dosimetry is: a Bragg-Gray cavity is a cavity (detector) so small that, when inserted into a medium, it does not disturb the fluence of charged particles existing in the medium. This means that the ideal Bragg-Gray cavity (detector) is one of infinitesimal dimensions, a "point" detector. In practice, such detectors do not exist but many real detectors may, in a first approximation, be treated as Bragg-Gray detectors to a high degree of accuracy. Corrections needed (so called perturbation corrections) to account for the deviation of the signal from a practical detector from that of an ideal one has been treated by, e.g., ICRU 1984, Alm Carlsson, 1985, Svensson and Brahme 1986, Alm Carlsson 1987. Derivation of "perturbation corrections" needs careful consideration and under-standing of the ideal case, i.e., that from which deviations are to be corrected for. The ideal case of a Bragg-Gray detector has been treated by Bragg 1912, Gray 1936, Laurence 1937, Spencer and Attix 1955 and Burch 1955. The formulation of Bragg-Gray theory by Spencer and Attix has found wide practical application and has been treated in detail elsewhere. The theory of Burch treats the same problem as did Spencer and Attix, viz., the significance of generation and slowing down of delta-particles in both medium and detector. Burch treated the problem in considerable detail but didn't find a solution for practical calculations. From a physical point of view, however, there is much to learn from Burch's approach. Also, his treatment of so called track ends, evaluated in some detail by Burch 1957, has been adapted in later versions of the Spencer-Attix formulation of Bragg-Gray theory.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Radiologi och bildbehandling (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Radiology, Nuclear Medicine and Medical Imaging (hsv//eng)

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Radiological physics

Radiofysik

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