Factors impacting on patient setup analysis and error management during breast cancer radiotherapy

Radiotherapy is required to deliver an accurate dose to the tumor while protecting surrounding normal tissues. Breast cancer radiotherapy involves a number of factors that can influence patient setup and error management, including the immobilization device used, the verification system and the patient's treatment position. The aim of this review is to compile and discuss the setup errors that occur due to the above-mentioned factors. In view of this, a systematic search of the scientific literature in the Medline/PubMed databases was performed over the 1990-2021 time period, with 93 articles found to be relevant for the study. To be accessible to all, this study not only aims to identify factors impacting on patient setup analysis, but also seeks to evaluate the role of each verification device, board immobilization and position in influencing these errors.

Frameless immobilization system with roll correction for stereotactic radiosurgery of intracranial brain metastases

The objectives of this study were to develop a frameless immobilization system that allows roll rotation corrections and to investigate the performance of this system for stereotactic radiosurgery (SRS) treatment. We designed the support frame of a frameless immobilization system based on the commercial Brainlab immobilization system. The support frame consisted of a fixed component and a rotating component. With rack and pinion gears and guide holes installed in the system, the rotating component was configured to be rotated along the longitudinal axis of the patient with respect to the fixed component. To evaluate the performance of the system, the six degree-of-freedom (6D) positioning corrections (translational and rotational corrections) were assessed by image verification between planning computed tomography (CT) and cone-beam computed tomography (CBCT) images. The commercial immobilization system was evaluated in the same manner for comparison. The mean translational shifts for the commercial system were 0.68 ± 0.19 mm, 0.73 ± 0.24 mm and 0.78 ± 0.19 mm, while those for the developed system were 0.44 ± 0.31 mm, 0.43 ± 0.25 mm and 0.60 ± 0.14 mm in the lateral, longitudinal and vertical directions, respectively. The mean rotational shifts for the commercial system were 0.37° ± 0.12°, 0.32° ± 0.16° and 0.38° ± 0.14°, while those for the developed system were 0.04° ± 0.04°, 0.11° ± 0.06° and 0.15° ± 0.12° along the lateral, vertical and longitudinal axes of the patient, respectively. For institutions that do not have 6D robotic couches installed, the use of the developed immobilization system can provide 6D corrections, resulting in shorter treatment times and higher patient positioning accuracy.