Open source deformable image registration system for treatment planning and recurrence CT scans : Validation in the head and neck region.
BACKGROUND
Clinical application of deformable registration (DIR) of medical images remains limited due to sparse validation of DIR methods in specific situations, e. g. in case of cancer recurrences. In this study the accuracy of DIR for registration of planning CT (pCT) and recurrence CT (rCT) images of head and neck squamous cell carcinoma (HNSCC) patients was evaluated.


METHODS
Twenty patients treated with definitive IMRT for HNSCC in 2010-2012 were included. For each patient, a pCT and an rCT scan were used. Median interval between the scans was 8.5 months. One observer manually contoured eight anatomical regions-of-interest (ROI) twice on pCT and once on rCT.


METHODS
pCT and rCT images were deformably registered using the open source software elastix. Mean surface distance (MSD) and Dice similarity coefficient (DSC) between contours were used for validation of DIR. A measure for delineation uncertainty was estimated by assessing MSD from the re-delineations of the same ROI on pCT. DIR and manual contouring uncertainties were correlated with tissue volume and rigidity.


RESULTS
MSD varied 1-3 mm for different ROIs for DIR and 1-1.5 mm for re-delineated ROIs performed on pCT. DSC for DIR varied between 0.58 and 0.79 for soft tissues and was 0.79 or higher for bony structures, and correlated with the volumes of ROIs (r = 0.5, p < 0.001) and tissue rigidity (r = 0.54, p < 0.001).


CONCLUSIONS
DIR using elastix in HNSCC on planning and recurrence CT scans is feasible; an uncertainty of the method is close to the voxel size length of the planning CT images.
Institute of Clinical Research, University of Southern Denmark, Odense, Denmark. ruta.zukauskaite@rsyd.dk.|Department of Oncology, Odense University Hospital, Sdr. Boulevard 29, C 5000, Odense, Denmark. ruta.zukauskaite@rsyd.dk.
Ruta
R
Zukauskaite
Institute of Clinical Research, University of Southern Denmark, Odense, Denmark.|Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark.
Carsten
C
Brink
Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark.|Institute of Medical Physics, School of Physics, The University of Sydney, Sydney, Australia.
Christian Rønn
CR
Hansen
Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark.|Institute of Medical Physics, School of Physics, The University of Sydney, Sydney, Australia.
Anders
A
Bertelsen
Department of Oncology, Odense University Hospital, Sdr. Boulevard 29, C 5000, Odense, Denmark.
Jørgen
J
Johansen
Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.
Cai
C
Grau
Department of Oncology, Odense University Hospital, Sdr. Boulevard 29, C 5000, Odense, Denmark.
Jesper Grau
JG
Eriksen
D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D006801:Humans; D020407:Internet; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012984:Software; D000077195:Squamous Cell Carcinoma of Head and Neck; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
Computed tomography; Validation; elastix; head and neck