Deformable image registration for cervical cancer brachytherapy dose accumulation: Organ at risk dose-volume histogram parameter reproducibility and anatomic position stability.
The purpose of this study was to determine the effect of deformable image registration (DIR) on cumulative organ at risk dose-volume histogram (DVH) parameter summation for more than three brachytherapy fractions. The reproducibility of different methods of DIR was tested. DIR was then used to assess the stability of the anatomic position of the DVH parameters within the bladder and rectum.



DIR was completed for 39 consecutive cervical cancer brachytherapy patients' planning CTs. Accumulated DVH parameters (D2ccand D0.1cc) for bladder and rectum were compared with dose summation without DIR. Reproducibility of DIR results was assessed for different methods of implementation based on adding contour biases added to the DIR algorithm. VolD2ccand VolD0.1ccstructures were created from the overlap of the D2ccand D0.1ccisodose and the bladder or rectum, respectively. The overlap of VolD2ccand VolD0.1ccstructures was calculated using the Dice similarity coefficient.



DIR accumulated D2ccand D0.1ccdecreased by an average of 2.9% and 4.2% for bladder and 5.08% and 2.8% for rectum compared with no DIR. DIR was most reproducible when the bladder or rectum contour was masked. The average Dice similarity coefficient was 0.78 and 0.61 for the bladder D2ccand D0.1ccas well as 0.83 and 0.62 for rectal D2ccand D0.1cc, respectively.



Dose decreases were observed for accumulated DVH parameters using DIR. Adding contour-based biases to the algorithm increases the reproducibility of D2ccand D0.1ccaccumulation. The anatomic position of VolD2ccwas more stable than VolD0.1cc.
Crown Princess Mary Cancer Centre, Westmead, NSW, Australia; Institute of Medical Physics, School of Physics, University of Sydney, Camperdown, NSW, Australia. Electronic address: emily.flower@health.nsw.gov.au.
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Flower
Crown Princess Mary Cancer Centre, Westmead, NSW, Australia; Sydney Medical School Nepean, University of Sydney, Kingswood, NSW, Australia.
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Do
Blacktown Cancer & Haematology Centre, Blacktown, NSW, Australia.
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Sykes
Department of Radiation Oncology, University of Washington, WA; Department of Radiation Oncology, Calvary Mater Newcastle Hospital, Newcastle, NSW, Australia; School of Health Sciences, University of Newcastle, Newcastle, NSW, Australia.
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Dempsey
Institute of Medical Physics, School of Physics, University of Sydney, Camperdown, NSW, Australia; Ingham Institute and Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW, Australia; Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia; South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, Australia.
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Holloway
Crown Princess Mary Cancer Centre, Westmead, NSW, Australia.
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Summerhayes
Institute of Medical Physics, School of Physics, University of Sydney, Camperdown, NSW, Australia.
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Thwaites
D000465:Algorithms; D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D058958:Organs at Risk / Q000033:anatomy & histology; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided; D012007:Rectum / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*
Cervix; Deformable image registration