Quantification of the reproducibility of the positioning in patients that receive radiotherapy with immobilization devices for treatments with VMAT using DRR and CBCT

The technological advances and the introduction of digital and computer systems to the treatment equipment s have contributed significantly in the precision when is necessary to deliver and distributing radiation dose in the planning volume where is located the tumor, besides also considering the healthy organs and tissues or in risk. For this treatment modality is necessary take into account the great importance that has the positioning, and immobilization and its reproducibility, making use of appropriate and personalized accessories that guarantee the bigger possible precision when the images are compared of before and after the treatment. For this study positioning data of 34 patients were quantified, which were treated with Volumetric Modulated Arc Therapy (VMAT) for the period between May to November of 2013. Of the patients 16 were treated in head and neck and 18 of prostate and abdomen. In all cases of head and neck treatment with VMAT immobilizer meshes were used that hold until the patient's neck, and in the cases of prostate and abdomen was used an immobilizer device under the knees and the ankles. All the cases were re-positioning using positioning techniques with Digitally Reconstructed Radiograph images (DRR) with acquisition modality Kv/Kv and Cone Beam the corrections and monitoring were carried out daily. Variations existed during the treatments that oscillate of 1-2 mm in the head and neck cases; and 2-4 mm in prostate and abdomen, these variations are necessary to quantify them in pro of the reproducibility in the patients positioning that receive radiotherapy and use immobilization device. (Author)