Effect of daily setup errors on individual dose distribution in conventional radiotherapy: an initial study

Abstract

Recent linear accelerators can perform cone beam computed tomography to correct setup errors immediately before dose delivery. We calculated the dose distribution with setup errors acquired from cone-beam computed tomography to determine a more realistic and individual effect of setup errors. The differences in dose distribution were analyzed.The setup errors of three patients who were irradiated in the neck, esophagus, and pelvic area were obtained retrospectively. We found that the maximum dose variances for the three cases were 19.9 to 35.9%. The maximum dose variance points were relatively far from the isocenter. The volume of the 10% dose difference had widths of 1.3 to 1.85 cm around the beam edges. The V95 and mean doses at the clinical target volume were mostly unchanged. Doses around the beam edges were more varied than those around the isocenter for every case. The dose on the spinal cord located near the beam edges varied by 5 -10 % compared with the dose of the radiotherapy plan in two of the cases. We demonstrated the individual dose distributions of the cases affected by daily setup errors for all fractions.

Impact of pitch angle setup error and setup error correction on dose distribution in volumetric modulated arc therapy for prostate cancer

“…Several studies have simulated the rotational setup errors by arrangement of the beam 7 alignment [9][10][11]. This is possible for a treatment plan with fixed beams such as a fixed beam IMRT plan.…”

“…The effects of setup error, including rotational errors, on the dose distribution during commonly used radiation therapies have been evaluated for several body sites [9]. The 5 dosimetric effect of rotational setup errors concerning IMRT for head and neck cancer has also been evaluated [10].…”