Abstract:
:This study evaluated unexpected dosimetric errors caused by machine control accuracy, patient setup errors, and patient weight changes/internal organ deformations. Trajectory log files for 13 gynecologic plans with seven- or nine-beam dynamic multileaf collimator (MLC) intensity-modulated radiation therapy (IMRT), and differences between expected and actual MLC positions and MUs were evaluated. Effects of patient setup errors on dosimetry were estimated by in-house software. To simulate residual patient setup errors after image-guided patient repositioning, planned dose distributions were recalculated (blurred dose) after the positions were randomly moved in three dimensions 0-2 mm (translation) and 0°-2° (rotation) 28 times per patient. Differences between planned and blurred doses in the clinical target volume (CTV) D98% and D2% were evaluated. Daily delivered doses were calculated from cone-beam computed tomography by the Hounsfield unit-to-density conversion method. Fractional and accumulated dose differences between original plans and actual delivery were evaluated by CTV D98% and D2% . The significance of accumulated doses was tested by the paired t test. Trajectory log file analysis showed that MLC positional errors were -0.01 ± 0.02 mm and MU delivery errors were 0.10 ± 0.10 MU. Differences in CTV D98% and D2% were <0.5% for simulated patient setup errors. Differences in CTV D98% and D2% were 2.4% or less between the fractional planned and delivered doses, but were 1.7% or less for the accumulated dose. Dosimetric errors were primarily caused by patient weight changes and internal organ deformation in gynecologic radiation therapy.
journal_name
J Appl Clin Med Physjournal_title
Journal of applied clinical medical physicsauthors
Utena Y,Takatsu J,Sugimoto S,Sasai Kdoi
10.1002/acm2.13163subject
Has Abstractpub_date
2021-01-10 00:00:00issn
1526-9914pub_type
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journal_title:Journal of applied clinical medical physics
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