Protocols for Correction

 
There are two basic correction strategies used while determining the most beneficial patient position and beam structure: on-line and off-line correction.The On-line strategy makes adjustment to patient and beam position during the treatment process, based on continuously updated information throughout the procedure.The advantage of this strategy is a reduction in both systematic and random errors and it is time-saving process.The Off-line strategy determines the best patient position through accumulated data gathered during treatment sessions. The strategy requires greater coordination of clinic-wide systems than on-line strategies.The use of off-line strategies reduces the risk of systematic errors, but only the on-line strategies can reduced the risk of random errors.

 

(Comment: frakciószám = number of fraction)
With different IGRT techniques the accuracy of patient set-up can be improved and the CTV-PTV margin can be reduced. With volumetric imaging such as kV CT, kV and MV CBCT the tumour shape and size or the effectiveness of treatment can be controlled. This technique is called adaptive radiation therapy (ART). ART can utilize daily CT or CBCT imaging to track anatomical changes, such as displacement and deformation in the target and surrounding tissues, and to adopt the treatment plan for optimal delivery accordingly. It can compensate for uncertainties related to organ deformation, inter-fraction setup errors, and previous deviations in dosimetric deliveries. In order to implement ART clinically, there are many technical issues to be addressed, including improved image quality of CBCT, accurate dose calculation on CBCT, deformable image registration, and dose reconstruction.

 

Literature

 

1. Laura A. Dawson, Michael B. Sharpe. Image-guided radiotherapy: rationale, benefits, and limitations. Lancet. Oncol. 7:848-858. 2006.
2. Dirk Verellen, Mark De Ridder, Nadine Linthout, Koen Tournel, Guy Soete, Guy Storme: Innovations in image-guided radiotherapy. NATURE REVIEWS CANCER 7:949-960. 2007.
3. Laura A. Dawson, David A. Jaffray: Advances in Image-Guided Radiation Therapy. J. Clin. Onc. 25:938-946. 2007.

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