Combining transrectal ultrasound and CT for image-guided adaptive brachytherapy of cervical cancer: Proof of concept.
To investigate the feasibility of a treatment planning workflow for three-dimensional image-guided cervix cancer brachytherapy, combining volumetric transrectal ultrasound (TRUS) for target definition with CT for dose optimization to organs at risk (OARs), for settings with no access to MRI.



A workflow for TRUS/CT-based volumetric treatment planning was developed, based on a customized system including ultrasound probe, stepper unit, and software for image volume acquisition. A full TRUS/CT-based workflow was simulated in a clinical case and compared with MR- or CT-only delineation. High-risk clinical target volume was delineated on TRUS, and OARs were delineated on CT. Manually defined tandem/ring applicator positions on TRUS and CT were used as a reference for rigid registration of the image volumes. Treatment plan optimization for TRUS target and CT organ volumes was performed and compared to MRI and CT target contours.



TRUS/CT-based contouring, applicator reconstruction, image fusion, and treatment planning were feasible, and the full workflow could be successfully demonstrated. The TRUS/CT plan fulfilled all clinical planning aims. Dose-volume histogram evaluation of the TRUS/CT-optimized plan (high-risk clinical target volume D90, OARs D2cm³for) on different image modalities showed good agreement between dose values reported for TRUS/CT and MRI-only reference contours and large deviations for CT-only target parameters.



A TRUS/CT-based workflow for full three-dimensional image-guided cervix brachytherapy treatment planning seems feasible and may be clinically comparable to MRI-based treatment planning. Further development to solve challenges with applicator definition in the TRUS volume is required before systematic applicability of this workflow.
Department of Radiation Oncology, Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Austria. Electronic address: nicole.nesvacil@meduniwien.ac.at.
Nicole
N
Nesvacil
Department of Radiation Oncology, Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria.
Maximilian P
MP
Schmid
Department of Radiation Oncology, Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Austria.
Richard
R
Pötter
Austrian Center for Medical Innovation and Technology, Wr. Neustadt, Austria.
Gernot
G
Kronreif
Department of Radiation Oncology, Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Austria.
Christian
C
Kirisits
D001918:Brachytherapy / Q000379:methods*; D054893:Cone-Beam Computed Tomography; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008875:Middle Aged; D009929:Organ Size; D058958:Organs at Risk; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014463:Ultrasonography / Q000379:methods; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D057188:Workflow
Brachytherapy; Cervix cancer; Image fusion; Transrectal ultrasound