No abstract available

[en] Short communication. 5 refs

[en] Letter to the editor

[en] Letter to the editor. 3 refs

[en] Letter to the editor. 3 refs

[en] Several of the most commonly used dosimetry protocols for high-energy photon and electron beams have been or are being revised. There are however, still differences in the recommended measuring procedures and numerical value of interaction coefficients and correction factors between the different protocols. The intention of this paper is to discuss some of these differences and to present a comparison of values of absorbed dose to water determined using different dosimetry protocols. (Auth.)

[en] Since July 1973, endocavitary irradiation has been used to treat 129 patients with rectal carcinoma. The lesion must be a modified Dukes' A, well-differentiated adenocarcinoma and no more than 5 cm in diameter and within 12 cm of the anal verge. Specialized diagnostic techniques assist with the clinical selection. Specially designed proctoscopes are used to visualize the carcinoma which is treated by a Philips RT-50 contact machine. 11000-12000 cGy are delivered in four treatments administered at 2-3 weekly intervals. No systemic side effects have been observed and local morbidity is minimal. This treatment perserves the anal sphincter, and sexual function in male patients. Hospitalization is not required and there is no risk of mortality. Recurrence has been observed in six of 129 patients within 18 months of treatment for known reasons. Two of these six patients have died from disease and a further 25 from other causes. The local control rate is 95.3%. This treatment modality has been offered also to 87 patients for palliation and this has been effectively obtained in 82.7%. This technique is an alternative to surgery in selected cases. (orig.)

[en] Lewis lung tumours were treated in vivo with acute radiation (20 Gy) and 1-(2-chloroethyl)-3-(4-methyl cyclohexyl)-1-nitrosourea (MeCCNU, 10 mg . kg^-1), cyclophosphamide (CY, 120 mg . kg^-1) or cis-dichlorodiammine platinum (cis-Pt, 10 mg . kg^-1) with time intervals ranging from simultaneous to 9 days in either sequence. Tumour response was measured by regrowth delay and combination responses were evaluated relative to calculated 'additivity envelopes'. With CY and cis-Pt, tumour volume response was approximately additive, whether the drugs were administered simultaneously, or up to 7 days before or after radiation. However, with simultaneous administration, MeCCNU and radiation were supra-additive in terms of volume response. In the fractionation studies, drugs were given either at the beginning or at the end of a regime of 5 daily 6 Gy doses. With CY and MeCCNU the drugs were more effective when given with the first radiation dose, but with cis-Pt either regime was equally effective. There was no evidence that repopulation could be exploited to improve therapeutic effect with any of the combination treatments used in this study. (Auth.)

[en] In studies of radiation damage, the parameter α/β of the linear-quadratic (LQ) model is usually estimated from iso-effect data by plotting the iso-effect doses in a so-called F_e-plot, which is a plot of the inverse total dose versus dose per fraction. This method, however, is statistically not well founded. A better, but relatively complex technique to estimate α/β ratio was described by Tucker. The author shows that results, virtually identical to those of Tucker can be obtained in a very simple way if the iso-effect doses are plotted as total dose D_n versus the product of dose per fraction and total dose, D_nd_n. A reliable estimator of the α/β ratio consists then of the negative inverse slope of the linear-regression line in this plot. The presentation of iso-effect data in such a D - dD plot highlights deviations from the LQ model more clearly than does the F_e-plot. It is therefore suggested to use the D - dD plot as a quick and easy graphical scheme to obtain an estimate of α/β. 11 refs.; 3 figs.; 1 table

[en] The results of transmission measurements for neutrons, cobalt-60 gamma-rays, and 10 and 15 MV photons made with close-packed arrays of tungsten rods are presented. These results indicate that tungsten rod arrays of reasonable thickness can provide for primary or secondary collimation of all these radiation beams. Development work on a collimation system utilizing the multi-rod concept which is capable of producing irregularly shaped fields and suitable for use in photon or neutron radiation therapy is described. (author). 11 refs.; 5 figs.; 1 tab