title: Consequences of Intermodality Registration Errors for Intramodality 3D Ultrasound IGRT.
abstract: Intramodality ultrasound image-guided radiotherapy systems compare daily ultrasound to reference ultrasound images. Nevertheless, because the actual treatment planning is based on a reference computed tomography image, and not on a reference ultrasound image, their accuracy depends partially on the correct intermodality registration of the reference ultrasound and computed tomography images for treatment planning. The error propagation in daily patient positioning due to potential registration errors at the planning stage was assessed in this work. Five different scenarios were simulated involving shifts or rotations of ultrasound or computed tomography images. The consequences of several workflow procedures were tested with a phantom setup. As long as the reference ultrasound and computed tomography images are made to match, the patient will be in the correct treatment position. In an example with a phantom measurement, the accuracy of the performed manual fusion was found to be ≤2 mm. In clinical practice, manual registration of patient images is expected to be more difficult. Uncorrected mismatches will lead to a systematically incorrect final patient position because there will be no indication that there was a misregistration between the computed tomography and reference ultrasound images. In the treatment room, the fusion with the computed tomography image will not be visible and based on the ultrasound images the patient position seems correct.
authors.affiliation: Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Skadi
authors.initials: S
authors.lastname: van der Meer
authors.affiliation: Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Enrica
authors.initials: E
authors.lastname: Seravalli
authors.affiliation: Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Davide
authors.initials: D
authors.lastname: Fontanarosa
authors.affiliation: Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Esther J
authors.initials: EJ
authors.lastname: Bloemen-van Gurp
authors.affiliation: Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands Department of Oncology, Medical Physics Unit, McGill University, Montréal, Québec, Canada frank.verhaegen@maastro.nl.
authors.forename: Frank
authors.initials: F
authors.lastname: Verhaegen
mesh_terms: D006801:Humans; D021621:Imaging, Three-Dimensional; D056888:Patient Positioning; D019047:Phantoms, Imaging; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation / Q000379:methods / Q000592:standards; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography / Q000379:methods; D057188:Workflow
keywords: error propagation; image guided radiotherapy; intermodality image fusion; patient safety; registration errors; ultrasound imaging