title: A tool for validating MRI-guided strategies: a digital breathing CT/MRI phantom of the abdominal site.
abstract: Dynamic magnetic resonance imaging (MRI) is emerging as the elected image modality for organ motion quantification and management in image-guided radiotherapy. However, the lack of validation tools is an open issue for image guidance in the abdominal and thoracic organs affected by organ motion due to respiration. We therefore present an abdominal four-dimensional (4D) CT/MRI digital phantom, including the estimation of MR tissue parameters, simulation of dedicated abdominal MR sequences, modeling of radiofrequency coil response and noise, followed by k-space sampling and image reconstruction. The phantom allows the realistic simulation of images generated by MR pulse sequences with control of scan and tissue parameters, combined with co-registered CT images. In order to demonstrate the potential of the phantom in a clinical scenario, we describe the validation of a virtual T1-weighted 4D MRI strategy. Specifically, the motion extracted from a T2-weighted 4D MRI is used to warp a T1-weighted breath-hold acquisition, with the aim of overcoming trade-offs that limit T1-weighted acquisitions. Such an application shows the applicability of the digital CT/MRI phantom as a validation tool, which should be especially useful for cases unsuited to obtain real imaging data.
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy. chiara.paganelli@polimi.it.
authors.forename: Chiara
authors.initials: C
authors.lastname: Paganelli
authors.affiliation: Division of Radiology, Istituto Europeo di Oncologia, Milan, Italy.
authors.forename: Paul
authors.initials: P
authors.lastname: Summers
authors.affiliation: Department of Experimental Physics-Medical Physics, Ludwig-Maximilians-Universität München (LMU Munich), Munich, Germany.|Department of Radiation Oncology, Ludwig-Maximilians-Universität München (LMU Munich), Munich, Germany.
authors.forename: Chiara
authors.initials: C
authors.lastname: Gianoli
authors.affiliation: Division of Radiology, Istituto Europeo di Oncologia, Milan, Italy.|Department of Oncology, Università degli Studi di Milano, Milan, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Bellomi
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy.|Bioengineering Unit, Centro Nazionale di Adroterapia Oncologica, Pavia, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Baroni
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Riboldi
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging*; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009038:Motion; D019047:Phantoms, Imaging; D012119:Respiration
keywords: 4DMRI; Digital phantom; MRI guidance; Radiotherapy