Abstract
The goal of this work was to prepare and to evaluate an off-line adaptive protocol for prostate teleradiotherapy with kilovoltage cone beam computer tomography (CBCT). Ten patients with localized prostate carcinoma treated with external beams underwent image-guided radiotherapy. In total, 162CBCT images were collected. Position of prostate and pubis symphysis (PS) with respect to the isocenter were measured off-line. Using the CBCT scans obtained in the first three fractions the average position of prostate in relation (AvPosPr) to PB was calculated. On each CBCT scan, the position of prostate with respect to AvPosPr was calculated and cumulative histogram of prostate displacement with respect to AvPosPr was prepared. Using this data, the adaptive protocol was prepared in which (1) based on the CBCT made in the first three fractions the AvPosPr to PS is obtained, (2) in all other fractions two orthogonal images are acquired and if for any direction set-up error exceeds 0.2cm the patient's position is corrected, and (3) additionally, the patient's position is corrected if the AvPosPr exceeds 0.2cm in any direction. To evaluate the adaptive protocol for 30consecutive patients, the CBCT was also made in 10th and 21st fraction. For the first 10patients, the results revealed that the prostate was displaced in relation to AvPosPr >0.7cm in the vertical and longitudinal directions only on 4 and 5images of 162CBCT images, respectively. For the lateral direction, this displacement was >0.3cm in one case. For the group of 30patients, displacement was never >0.7, and 0.3cm for the vertical and lateral directions. In two cases, displacements were >0.7cm for the longitudinal direction. Implementation of the proposed adaptive procedure based on the on-line set-up error elimination followed by a reduction of systematic internal error enables reducing the CTV-PTV margin to 0.7, 0.7, and 0.4cm for the vertical, longitudinal, and lateral directions, respectively.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
