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The measured data, whose high precision makes them useful for evaluation of the accuracy of electron dose algorithms, will be made publicly available. Based on the spread in dose differences, the PBRA has at least twice the accuracy of the PBA. From a clinical perspective the PBRA accuracy is acceptable in the retromolar trigone and nose for electron therapy with and without bolus.

The intent of this study was to determine whether open neck biopsy for patients with squamous cell carcinoma metastatic to the neck influenced the biologic course of the disease or the response to treatment. One hundred ninety-two patients, treated over a 10-year period at M.D. Anderson Hospital and Tumor Institute, were reviewed; 102 of the 139 patients, whose primary site of disease was identified prior to definitive treatment, were matched with a control group of 204 patients. The results showed no significant difference in wound complications, neck recurrence, distant metastases, and 5-year survival. Also, time interval from the biopsy to subsequent treatment and the type of node biopsy did not appear to have any significant detrimental effect. On the basis of these findings, we conclude that, although it is important to refrain from proceeding with an open biopsy until a complete head and neck evaluation has been done, violation of the neck does not signify a poorer prognosis--provided adequate treatment is subsequently given.

The demands of a busy clinic require that basic machine calculations be performed as accurately, rapidly, and simply as possible. For the electron beam of the Therac 20 Saturne linear accelerator, a method suitable for a programmable calculator is described to predict the dose output from the measurement of selected fields. One-dimensional output factors were measured; these are defined as output factors of rectangular fields where one side is always equal to the side of the square reference field. The output of an arbitrary rectangular field X, Y is given by the product of the output factors OF(X,Y) = OF(X,10) X OF(10,Y), where 10 is the side of the square reference field. The measured data indicate that the output of very large rectangular and square fields is underestimated using this method for the lower energies. A correction factor of the form CF = C X [(X - 10)(Y - 10)/(X - 10)(Y - 10) 1/2] results in agreement with measured data to within 1.5% for all energies.