Radio frequency shielding for a linac-MRI system

Lamey, M; Burke, B; Blosser, E.; Rathee, S; Zanche, Nicola De; Fallone, B. G.

doi:10.1088/0031-9155/55/4/006

Cited by 17 publications

(10 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The method and effect of RF shielding for this system has been previously described. 12 This means that a total of 11 (beam off, beam on at five different dose rates, beam on but blocked at the same five dose rates) different imaging conditions were examined for each phantom and coil combination.…”

Section: Iia Effect Of Ric and Linear Accelerator Dose Rate On Mr Imentioning

confidence: 99%

Effect of radiation induced current on the quality of MR images in an integrated linac‐MR system

et al. 2012

View full text Add to dashboard Cite

show abstract

Section: Iia Effect Of Ric and Linear Accelerator Dose Rate On Mr Imentioning

confidence: 99%

Effect of radiation induced current on the quality of MR images in an integrated linac‐MR system

et al. 2012

View full text Add to dashboard Cite

show abstract

“…This block was located far away from the coil, did not form any electrical connection with the linac, MRI, or RF cage and would not provide any RF shielding. Lamey et al 13 showed (see Fig. 9 in Ref.…”

Section: Iib Radiation Effect or Radiofrequency Interferencementioning

confidence: 92%

“…9 in Ref. 13) that if not properly shielded, the RF noise is visible in the k-space data even when the radiation beam is blocked from reaching the RF coil with the same lead block; however, when the RF is properly shielded there was no interference signal present (see Figs. 5 and 7 in Ref.…”

Section: Iib Radiation Effect or Radiofrequency Interferencementioning

confidence: 95%

See 1 more Smart Citation

Radiation induced current in the RF coils of integrated linac‐MR systems: The effect of buildup and magnetic field

et al. 2012

View full text Add to dashboard Cite

The RIC in RF coils results from the lack of electronic equilibrium in the coil conductor as the RIC in planar conductor was completely removed by identical buildup of adequate thickness to create electronic equilibrium. The buildup method of RIC removal is effective in cylindrical coil geometry when the coil conductor is in direct contact with the patient. The presence of air makes this method of RIC removal less effective although placing buildup still reduces the RIC by up to 60%. The RIC Monte Carlo simulation is a useful tool for practical coil design where radiation effects must be considered. The SNR is improved in the images obtained concurrently withradiation if buildup is applied to the coil.

show abstract

“…The linear accelerator (linac) is a reliable unit for producing and delivering x rays. Solutions to various challenges to the linac‐MR integration, such as electron gun shield and design, decoupling between the linac and MR imager, RF shielding, and the magnet designed, have been published.…”

Section: Introductionmentioning

confidence: 99%

Proton beam behavior in a parallel configured MRI‐proton therapy hybrid: Effects of time‐varying gradient magnetic fields

Santos¹,

Wachowicz

Burke

et al. 2018

Medical Physics

View full text Add to dashboard Cite

Purpose Real‐time magnetic resonance (MR) guidance is of interest to various groups globally because the superior soft tissue contrast MR images offer over other x‐ray‐based imaging modalities. Because of the precision required in proton therapy, proton therapy treatments rely heavily on image guidance. Integrating a magnetic resonance imaging (MRI) into a proton therapy treatment is a challenge. The charged particles (protons) used in proton therapy experience magnetic forces when travelling through the MRI magnetic fields. Given that it is desired that proton beams can be delivered with submillimeter accuracy, it is important that all potential sources of beam displacement are well modeled and understood. This study investigated the behavior of monoenergetic proton beams in the presence of a simulated set of realistic three‐dimensional (3D) vector magnetic gradient fields required for spatial localization during imaging. This deflecting source has not been previously investigated. Methods Three‐dimensional magnetic vector fields from a superconducting 0.5 T open bore MRI magnet model (previously developed in‐house) and 3D magnetic fields from an in‐house gradient coil model were applied to two types of computer simulations. In all simulations, monoenergetic proton pencil beams (from 80 to 250 MeV) were used. The initial directions of proton beams were varied. In all simulations, the orientation of the B0 field coincided with the positive z‐axis in the simulation geometry. The first type of simulation is based on an analytic magnetic force equation (analytic simulations) while the second type is a full Monte Carlo (MC) simulation. The analytic simulations were limited to propagating the proton beams in vacuum but could be rapidly calculated in a desktop computer while the MC simulations were calculated in a cluster computer. The proton beam locations and dose profiles at the central plane (z = 0 cm) with or without magnetic fields were extracted and used to quantify the effect of the presence of the different magnetic fields on the proton beam. Results The analytic simulations agree with MC results within 0.025 mm, thus acting as the verification of MC calculations. The presence of the B0 field caused the beam to follow a helical trajectory which resulted in angular offsets of 4.9o, 3.6o, and 2.8o for the 80, 150, and 250 MeV, respectively. Magnetic field deflections caused by a rapid MRI sequence (bSSFP, with maximum gradient strength of 40 mT/m) show a pattern of distortion which remained spatially invariant in the MR's field of view. For the 80 MeV beam, this pattern shows a maximum ranged in the y direction of 1.5 mm. The presence of the B0 field during the bSSFP simulations adds the same beam rotation to the observed during the B0 only simulations. Conclusion This investigation reveals that time‐varying gradient magnetic fields required for image generation can cause a small spread in the proton beams used in the study which are independent of the effects arising from the B0 field. Further, studies where cl...

show abstract

Radio frequency shielding for a linac-MRI system

Cited by 17 publications

References 19 publications

Effect of radiation induced current on the quality of MR images in an integrated linac‐MR system

Effect of radiation induced current on the quality of MR images in an integrated linac‐MR system

Radiation induced current in the RF coils of integrated linac‐MR systems: The effect of buildup and magnetic field

Proton beam behavior in a parallel configured MRI‐proton therapy hybrid: Effects of time‐varying gradient magnetic fields

Contact Info

Product

Resources

About