title: Integrated megavoltage portal imaging with a 1.5 T MRI linac.
abstract: In this note, the feasibility of complementing our hybrid 1.5 T MRI linac (MRL) with a megavoltage (MV) portal imager is investigated. A standard aSi MV detector panel is added to the system and both qualitative and quantitative performances are determined. Simultaneous MR imaging and transmission imaging can be performed without mutual interference. The MV image quality is compromised by beam transmission and longer isocentre distance; still, the field edges and bony anatomy can be detected at very low dose levels of 0.4 cGy. MV imaging integrated with the MRL provides an independent and well-established position verification tool, a field edge check and a calibration for alignment of the coordinate systems of the MRI and the accelerator. The portal imager can also be a valuable means for benchmarking MRI-guided position verification protocols on a patient-specific basis in the introductory phase.
authors.affiliation: Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. B.W.Raaymakers@umcutrecht.nl
authors.forename: B W
authors.initials: BW
authors.lastname: Raaymakers
authors.forename: J C J
authors.initials: JC
authors.lastname: de Boer
authors.forename: C
authors.initials: C
authors.lastname: Knox
authors.forename: S P M
authors.initials: SP
authors.lastname: Crijns
authors.forename: K
authors.initials: K
authors.lastname: Smit
authors.forename: M K
authors.initials: MK
authors.lastname: Stam
authors.forename: M R
authors.initials: MR
authors.lastname: van den Bosch
authors.forename: J G M
authors.initials: JG
authors.lastname: Kok
authors.forename: J J W
authors.initials: JJ
authors.lastname: Lagendijk
mesh_terms: D001842:Bone and Bones / Q000000981:diagnostic imaging* / Q000473:pathology; D005240:Feasibility Studies; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation / Q000379:methods*; D057230:Limit of Detection; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D010315:Particle Accelerators / Q000295:instrumentation; D010384:Pelvic Bones / Q000000981:diagnostic imaging / Q000473:pathology; D010388:Pelvis / Q000000981:diagnostic imaging / Q000473:pathology; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011859:Radiography