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III. Moving Field Techniques contrasted with Wedge Filter Techniques in High Energy Radiation Treatment

The London Hospital, London, E.1

This excerpt was created in the absence of an abstract.

The first consideration in planning radiotherapeutic techniques has always been to raise the tumour to a cancericidal dose and spare the normal tissue. The next consideration is to do this accurately, and easily; that is to say with as little discomfort as possible for the patient and in a manner that is not beyond the scope and endurance of the average radiographer, and finally that when a given method of treatment is investigated thoroughly it should be adaptable to a wide range of treatment problems.

It is clear historically that the major consideration which led to the development of moving field therapy was a desire to procure a skin-sparing technique, and now that skin-sparing can be achieved in other ways the impetus has been allowed to affect the choice of technique with new and higher energies. The role of moving field therapy has been carefully considered as recently as 1958 in a symposium in this Institute (Farmer, Fowler, Chance, Snelling and Stern), with reference to 250 kV X rays. One disadvantage then became clear: the large integral dose—12·7 Mg rads as compared with 7 Mg rads for a comparable fixed field technique (Farmer, 1958).

Moving field techniques depend on the production of a satisfactory body outline and this introduces a factor of considerable variation and error. These techniques also rely either on a combination of measured transit doses as adopted by O'Connor (1956), or on calculation alone as suggested by Quimby and Cohen (1957).