G P Liney1, B Dong2, J Begg3, P Vial4, K Zhang2, F Lee5, A Walker6, R Rai6, T Causer7, S J Alnaghy7, B M Oborn8, L Holloway9, P Metcalfe7, M Barton10, S Crozier11, P Keall12. 1. Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool NSW 2170, Australia; Radiation Physics, Liverpool Cancer Therapy Centre, Liverpool NSW 2170, Australia; School of Medicine, University of New South Wales, Sydney NSW 2170, Australia; and Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia. 2. Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool NSW 2170, Australia. 3. Radiation Physics, Liverpool Cancer Therapy Centre, Liverpool NSW 2170, Australia. 4. Radiation Physics & Liverpool Cancer Therapy Centre, Liverpool, NSW 2170, Australia and Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia. 5. Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia. 6. Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia and Radiation Physics, Liverpool Cancer Therapy Centre, Liverpool NSW 2170, Australia. 7. Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia. 8. Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia and Illawarra Cancer Care Centre, Wollongong Hospital, NSW 2500, Australia. 9. Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool NSW 2170, Australia; Radiation Physics, Liverpool Cancer Therapy Centre, Liverpool NSW 2170, Australia; School of Medicine, University of New South Wales, Sydney NSW 2170, Australia; Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia; and Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia. 10. Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool NSW 2170, Australia and School of Medicine, University of New South Wales, Sydney NSW 2170, Australia. 11. School of Information Technology & Electrical Engineering, University of Queensland, Brisbane, QLD 4072, Australia. 12. Radiation Physics Laboratory, Sydney Medical School, University of Sydney, Sydney NSW 2170, Australia.
Abstract
PURPOSE: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid magnetic resonance imaging (MRI)-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-linac system. This work describes results from a prototype experimental system to demonstrate the feasibility of a high field inline MR-linac. METHODS: The magnet is a 1.5 T MRI system (Sonata, Siemens Healthcare) was located in a purpose built radiofrequency (RF) cage enabling shielding from and close proximity to a linear accelerator with inline (and future perpendicular) orientation. A portable linear accelerator (Linatron, Varian) was installed together with a multileaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-linac experiments was performed to investigate (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array; and (3) electron contamination effects measured using Gafchromic film and an electronic portal imaging device (EPID). RESULTS: (1) Image quality was unaffected by the radiation beam with the macropodine phantom image with the beam on being almost identical to the image with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background intensity when the radiation beam was on. (3) Film and EPID measurements demonstrated electron focusing occurring along the centerline of the magnet axis. CONCLUSIONS: A proof-of-concept high-field MRI-linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field inline MRI-linac and study a number of the technical challenges and solutions.
PURPOSE: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid magnetic resonance imaging (MRI)-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-linac system. This work describes results from a prototype experimental system to demonstrate the feasibility of a high field inline MR-linac. METHODS: The magnet is a 1.5 T MRI system (Sonata, Siemens Healthcare) was located in a purpose built radiofrequency (RF) cage enabling shielding from and close proximity to a linear accelerator with inline (and future perpendicular) orientation. A portable linear accelerator (Linatron, Varian) was installed together with a multileaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-linac experiments was performed to investigate (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array; and (3) electron contamination effects measured using Gafchromic film and an electronic portal imaging device (EPID). RESULTS: (1) Image quality was unaffected by the radiation beam with the macropodine phantom image with the beam on being almost identical to the image with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background intensity when the radiation beam was on. (3) Film and EPID measurements demonstrated electron focusing occurring along the centerline of the magnet axis. CONCLUSIONS: A proof-of-concept high-field MRI-linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field inline MRI-linac and study a number of the technical challenges and solutions.
Authors: J P Kieselmann; C P Kamerling; N Burgos; M J Menten; C D Fuller; S Nill; M J Cardoso; U Oelfke Journal: Phys Med Biol Date: 2018-07-11 Impact factor: 3.609
Authors: Elizabeth Patterson; Bradley M Oborn; Dean Cutajar; Urszula Jelen; Gary Liney; Anatoly B Rosenfeld; Peter E Metcalfe Journal: J Appl Clin Med Phys Date: 2022-03-25 Impact factor: 2.243