PMID: 2105923Feb 1, 1990Paper

Radiation qualities of x-ray beams in cooperative clinical trials

International Journal of Radiation Oncology, Biology, Physics
M Tatcher, A S Glicksman

Abstract

X-ray beams are usually described by "MV" numbers which represent accelerating potentials (AP) and approximations to the maximum energies in the photon spectra. However, these numbers do not uniquely specify the properties of the beams. Current high energy photon dosimetry protocols specify radiation quality in terms of a measured ionization ratio which is equivalent to the ratio of the tissue-maximum ratios at depths 10 cm and 20 cm, for field size 10 cm X 10 cm [TMR)20(10]. For convenience, the American Association of Physicists in Medicine introduced a new parameter, known as the Nominal Accelerating Potential (NAP), which was derived from (TMR)20(10) and features values in MV units that are similar to those of the conventional accelerating potentials. (TMR)20(10) and Nominal Accelerating Potential may be considered to be expressions of the penetrating powers of x-ray beams. We determined (TMR)20(10) and Nominal Accelerating Potential for 460 treatment machines with stated accelerating potentials from 4 MV to 25 MV in the Quality Assurance Review Center's files of machine data from institutions that participate in cooperative clinical trials. The results demonstrate appreciable variability of the two parameters at each state...Continue Reading

References

Jan 1, 1975·The American Journal of Roentgenology, Radium Therapy, and Nuclear Medicine·E B PodgorsakH E Johns
May 1, 1986·Acta Radiologica. Oncology·A Brahme, P Andreo
Sep 1, 1986·Medical Physics·R J SchulzF M Kahn
Jan 1, 1986·Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology·A BridierA Dutreix

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Citations

Mar 1, 1995·Clinical Rheumatology·B KrolM van Leeuwen
Jun 1, 1996·European Journal of Epidemiology·P VanhemsR Pineault

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