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Whole Abdominal Irradiation by Cobalt-60 Moving-Strip Technic

1963; Radiological Society of North America; Volume: 81; Issue: 4 Linguagem: Inglês

10.1148/81.4.632

1527-1315

Luis Delclos, Ernest J. Braun, J. Raul Herrera, Vincent Sampiere, Earl Van Roosenbeek,

Advances in Oncology and Radiotherapy

The moving-strip technic was developed in Manchester, England, during the 1940's for utilization with orthovoltage irradiation. Since 1957 it has been applied in the M. D. Anderson Hospital and Tumor Institute to Co60 therapy. The purpose of developing such a technic was to find a method of irradiating the whole abdomen, which would improve systemic tolerance. There are two main types of disease which require total abdominal irradiation: The ovarian carcinomas, and the abdominal manifestations of the lymphomas. A variety of clinical situations such as seminomas, with extensive involvement of the periaortic nodes, also call for such a technic. Static Field Technic of Whole Abdominal Irradiation Irradiation to the whole abdomen should be given preferably in one undivided volume with homogeneous dosage. With either conventional 250-kv or supervoltage roentgen therapy, the whole abdomen can be irradiated through large parallel opposed portals, if the distance from the skin to the target is sufficiently great, about 100 cm., as 35 cm., on the average, are required to cover the abdomen from the pelvic floor to the diaphragm. Although the dose (Fig. 1 A and B) is less at the center than anteriorly and posteriorly, it is sufficiently homogeneous. The patient's tolerance is poor. There is a considerable drop in the blood count, and nausea, diarrhea, a feeling of fatigue, and loss of appetite are always present. Rarely the treatments does not have to be interrupted. However, a central dose of around 3,000 rads can be delivered over six to seven weeks. Another static field procedure is the so-called “trunk bridge” technic (3, 7, 8). Two anterior beams, inclined at an angle of 60° to each other, are opposed by two similarly arranged posterior beams (Fig. 2, A and B). The dimensions of the fields will depend on the patient's measurements, 30 × 15 cm. being an average size; four contiguous fields may have to be used for larger patients. The inter-apical distance is variable and is determined by patient thickness, but the distances between the upper edges of the beams and the apex, and the angle of inclination are fixed. These two fixed measurements have been found, by trial and error, to be the most satisfactory. The tolerance is no better than with two parallel opposed fields, but there is a great improvement in the resulting iso-dose distribution, which gives not only a reasonably homogeneous dosage but a higher dose at the center. Moving Strip Principle: With the moving strip technic, a volume of tissue from the pelvic floor to the diaphragm is seen by the beam only a certain number of days. The dose to the tumor, therefore, in that volume, although it may be the same total dose as with the static-field technics, should have a much greater biological efficiency because it is given in a much shorter time.