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SU‐GG‐J‐28: An Investigation of Intra and Inter‐Fraction Motion in Cervical Cancer Patients
Author(s) -
Taylor B,
Boyd J,
Kasibhatla M,
Oldham M
Publication year - 2008
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2961585
Subject(s) - cervix , medicine , radiation therapy , nuclear medicine , cervical cancer , sagittal plane , fraction (chemistry) , margin (machine learning) , radiology , cancer , computer science , chemistry , organic chemistry , machine learning
Purpose: To quantify the intra‐fraction motion of the cervix at various time points during a course of external beam radiation therapy. Also to develop patient‐specific PTV margins that can account for the observed intra‐fraction motion for cervix patients. Method and Materials: Multiple single shot fast spin echo MRI images were acquired through the central sagittal slice of the cervix of 6 patients undergoing external beam radiation therapy for cervical cancer. Images were acquired at 6‐second intervals for approximately 20 minutes. MRI scans were performed at 3 time points; pre‐treatment, mid‐treatment and post‐treatment. Cervical contours were delineated on all images using in‐house software which also enabled quantification of motion and deformation. Using these contours, the extent of margin expansion to achieve 100% coverage was measured and used to construct customized PTV expansions. Results: During each intra‐fraction period a general trend was observed in that the cervix moved superiorly and posteriorly with time (up to 6 mm). This motion was observed to correlate with bladder filling. For scans acquired at different time points, anterior motion increased as a function of treatment progression. Anterior PTV expansion increased from 2.2mm to 6.6 mm while the inferior margin decreased from 7.0mm to 3.1mm. No systematic trends were observed in the posterior or superior directions when comparing scans acquired at different time points through the treatment. Conclusion: This work suggests that as treatment of the cervix progresses, significant changes in intra‐fraction motion can occur. Further, each patient's motion is unique and requires individual assessment for custom PTV margin construction. Motion analysis may provide guidance as to when an IMRT boost would be most successful in replacing an interstitial brachytherapy boost.