Correction Method on Mismatched Posterior Edge of Medial and Lateral Tangential Fields for Three Fields Techniques in Breast Cancer / 대한방사선종양학회지

PURPOSE: The target volume for the three field technique in breast cancer include the breast tangential and supraclavicular areas. The techniques rotating the gantry and couch angles, to match these two areas, will geometrically produce mismatching of the posterior edge between the medial and lateral tangential beams. This mismatch was confirmed by film dosimetry and three-dimensional computer planning. The correction methods of this mismatching were studied in this article. MATERIALS AND METHODS: After the supraclavicular field was simulated using a half beam block and the medial and lateral tangential fields, by the rotation of the couch and gantry, we compared the following two methods to correct the mismatch. The first method was the rotation of collimator until a line drawn on the posterior edge of tangential beams before the rotation of couch aligned the line drawn on the posterior edge after the rotation. The second method was the rotation of collimator according to the formula developed by the author as follows; Co=2sin(-1){sin angle x sin (C/2)} (Co: collimator angle, angle: angle between tangential beam and table, C: couch angle) RESULTS: The film dosimetry showed the mismatching of posterior edges of the medial and lateral tangential fields prior to the rotation of collimator, while the posterior edges matched well after the rotation of collimator according to the formula. The three-dimensional computer plan also showed that the posterior edges matched well after the rotation of collimator accordingly. The DVH of the ipsilateral lung with the proper rotation of collimator angle was better than that without the rotation of collimator angle. CONCLUSION: The mismatching of the posterior edges of the medial and lateral tangential fields can be recognized on the three field technique in breast irradiation when the gantry and couch are simultaneously rotated and can be corrected with the proper rotation of the collimator angle. The radiation dose to the ipsilateral lung could be lowered with this technique.

Effects of Visual Field Factor on Pseudoneglect / 中国临床心理学杂志

Objective:Two experiments were performed to research the effects of visual field factor on pseudoneglect and to test the theories about neglect and pseudoneglect.Methods:Experiment 1 employed the landmark task and greyscales task in tachistoscopic and forced-choice conditions.Experiment 2 employed the greyscales task and tachistoscopic visual three-field technique.Results:Experiment 1 manifested that greyscales had no crossover effect;the length factor had effect on the greyscales task as the landmark task,but it only affected the bias magnitude,not the error direction.Experiment 2 indicated that the main effect of visual field was significant:when the greyscales were presented in the middle or right,pseudoneglect manifested,but when in the left,pseudoneglect vanished.Conclusion:The results provide evidence supporting the hypothesis that the perceptual distortion derives from the attentional process.