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Technical note: Experimental results from a prototype high-field inline MRI-linac

Journal Article


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.

Authors


  •   Liney, Gary P. (external author)
  •   Dong, B (external author)
  •   Begg, Jarrad (external author)
  •   Vial, Philip J. (external author)
  •   Zhang, K (external author)
  •   Lee, F (external author)
  •   Walker, Amy
  •   Rai, Roshika (external author)
  •   Causer, Trent (external author)
  •   Alnaghy, Sarah (external author)
  •   Oborn, Brad M.
  •   Holloway, Lois C.
  •   Metcalfe, Peter E.
  •   Barton, Michael (external author)
  •   Crozier, Stuart (external author)
  •   Keall, Paul J. (external author)

Publication Date


  • 2016

Citation


  • Liney, G. P., Dong, B., Begg, J., Vial, P., Zhang, K., Lee, F., Walker, A., Rai, R., Causer, T., Alnaghy, S. J., Oborn, B. M., Holloway, L., Metcalfe, P., Barton, M., Crozier, S. & Keall, P. (2016). Technical note: Experimental results from a prototype high-field inline MRI-linac. Medical Physics, 43 (9), 5188-5194.

Scopus Eid


  • 2-s2.0-84984669502

Ro Metadata Url


  • http://ro.uow.edu.au/eispapers/5856

Has Global Citation Frequency


Number Of Pages


  • 6

Start Page


  • 5188

End Page


  • 5194

Volume


  • 43

Issue


  • 9

Place Of Publication


  • United States

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.

Authors


  •   Liney, Gary P. (external author)
  •   Dong, B (external author)
  •   Begg, Jarrad (external author)
  •   Vial, Philip J. (external author)
  •   Zhang, K (external author)
  •   Lee, F (external author)
  •   Walker, Amy
  •   Rai, Roshika (external author)
  •   Causer, Trent (external author)
  •   Alnaghy, Sarah (external author)
  •   Oborn, Brad M.
  •   Holloway, Lois C.
  •   Metcalfe, Peter E.
  •   Barton, Michael (external author)
  •   Crozier, Stuart (external author)
  •   Keall, Paul J. (external author)

Publication Date


  • 2016

Citation


  • Liney, G. P., Dong, B., Begg, J., Vial, P., Zhang, K., Lee, F., Walker, A., Rai, R., Causer, T., Alnaghy, S. J., Oborn, B. M., Holloway, L., Metcalfe, P., Barton, M., Crozier, S. & Keall, P. (2016). Technical note: Experimental results from a prototype high-field inline MRI-linac. Medical Physics, 43 (9), 5188-5194.

Scopus Eid


  • 2-s2.0-84984669502

Ro Metadata Url


  • http://ro.uow.edu.au/eispapers/5856

Has Global Citation Frequency


Number Of Pages


  • 6

Start Page


  • 5188

End Page


  • 5194

Volume


  • 43

Issue


  • 9

Place Of Publication


  • United States