In patients with locally advanced rectal cancer previously treated with neoadjuvant radiochemotherapy, the combined evaluation of pathologic stage and after-radiochemotherapy (18)F-FDG PET at restaging identified a subgroup of patients characterized by good response to radiochemotherapy and a more favorable prognosis. In these patients, a conservative surgical approach might be considered.
The new beam arrangement, with the use of the UDT, allows to administer different radiation doses to three volumes with different tumor cell density in order to obtain the same probability of local response in all target volumes without increasing the toxicity.
Modern computer networks provide satisfying levels of data recording and verification between the treatment planning system (TPS) and the accelerators, while the main weakness of the preparation chain remains the simulation. When a conventional simulator is employed, it may adversely affect the three-dimensional treatment planning system (3DPS) process because of the difficulty to document the leaf positions on the simulator location films and on the patient's skin. With a conventional simulator, hard copies of the DRRs of each field and CT scans at isocenter level are needed. In an attempt to transfer more information displayed from a BEV perspective from the 3DPS to simulator radiographs, this study aimed to reduce the quality loss by using a 2D conventional simulator in a 3DPS process. We realized an acetate photocopy of TPS data for each field, from a BEV perspective, containing: DRR, wire frames of the PTV, organs at risk and MLC aperture. The photocopies, with an appropriate magnification factor to obtain a correct projective value (ratio 1:1) at isocenter level, are carefully placed on the radiographic images on the same hard copy which allows us to better understand possible setup errors and obliges us to correct these. The method provides reliable documentation, facilitates treatment verification, and fulfils the criteria for MLC simulation. It is accurate, simple, and very inexpensive.
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