Pseudo beam’s-eye–view as applied to beam orientation selection in intensity-modulated radiation therapy

Purpose: To introduce the concept of pseudo beam’s-eye–view (pBEV), to establish a framework for computer-assisted beam orientation selection in intensity-modulated radiation therapy (IMRT), and to evaluate the utility of the proposed technique.

Methods and Materials: To facilitate the selection of beam orientations for IMRT treatment planning, a scoring of beam direction was introduced. The score function was based on the maximum target dose deliverable by the beam without exceeding the tolerance doses of the critical structures. For the score function calculation, the beam portal at given gantry and couch angles was divided into a grid of beamlets. Each beamlet crossing the target was assigned the maximum intensity that could be used without exceeding the dose tolerances of the organs at risk (OARs) and normal tissue. Thereafter, a score was assigned to the beam according to the target dose delivered. The beams for the treatment were selected among those with the highest scores. In a sense, this technique is similar to the beam’s-eye–view approach used in conventional radiation therapy, except that the evaluation by a human is replaced by a score function, and beam modulation is taken into account.

Results: The pBEV technique was tested on two clinical cases: a paraspinal treatment and a nasopharyngeal cancer with both coplanar and noncoplanar beam configurations. The plans generated under the guidance of pBEV for the paraspinal treatment offered superior target dose uniformity and reduced OAR doses. For the nasopharyngeal cancer case, it was also found that the pBEV-selected coplanar and noncoplanar beams significantly improved the target coverage without compromising the sparing of the OARs.

Conclusions: The pBEV technique developed in this work provides a comprehensive tool for beam orientation selection in IMRT. It is especially valuable for complicated cases, where the target is surrounded by several sensitive structures and where it is difficult to select a set of good beam orientations. The pBEV technique has considerable potential for simplifying the IMRT treatment planning process and for maximizing the technical capacity of IMRT.     

Cohen's operation in the treatment of vesico-ureteral reflux in children

The present study is a review of the results of Cohen's operation performed on 43 ureters in 32 children. Treatment results were assessed through the comparison of cystographic and 131I-hippuran renographic findings obtained before and after surgery. Urodynamic recovery in the affected ureter was demonstrated in all children. One year after surgery, there was no improvement in the activity of the resected kidney in 37% of patients. In the remaining patients, secretion improved by 10-13% in the affected kidney. Seventeen children returned for follow-up examination 2 years after surgery. The activity of the affected kidney and the contralateral one improved in 13 of 17 patients. There was no upper urinary retention due to ureteral stricture in any of the children. The rate of recurrent vesico-ureteral reflux (VUR) was 5.3%. Augmentation or persistence of purification deficiency in the affected kidney, detected in 12 patients at first postoperative follow-up, was qualified as a result of aggravated chronic pyelonephritis rather than that of surgical complications related to methodologic specifics. This assumption was verified by the results of the next follow-up examination 2 years after surgery. Therefore, Cohen's method can be recommended for large-scale application in the treatment of VUR in children and is expected to essentially reduce the rate of relapses and improve the standards of surgical care of children with this grave disease.     

Immunohistologic study of intestinal antigen beta-2-MA in gastric tumors

Immunologic techniques were used to examine localization of the intestinal antigen beta-2-MA in 87 cases of malignant gastric tumors and 25 cases of non-neoplastic diseases of the stomach. The antigen was identified in 46.4% of gastric carcinomas. The presence of the antigen was not found to be related to a histological type of cancer. The beta-2-MA antigen was detected in the areas of intestinal metaplasia alone in 48% of the cases and in combination with malignant tumors in 50.9%. The antigen was found to be more common in the mucosa adjacent to those of diffuse cancer than in the mucosa located around cancer of intestinal type (p less than 0.01). beta-2-MA is one of the antigens showing intestine-differentiated cells in a number of gastric tumors and may be useful for immunological studies of gastric neoplastic types.     

Cellular localization of human secretory β-globulin in normal and tumor tissues

Department of Biochemistry, N. I. Pirogov Second Moscow Medical Institute P. A. Gertsen Moscow Oncologic Research Institute (Presented by Academician of the Academy of Medical Sciences of the USSR Yu. S. Lopukhin.) Translated from Byulleten Éksperimental'noi Biologii i Meditsiny, Vol. 113, No 1, pp. 79–82, January, 1992.