Investigations in the Design of a Novel Linac-MRI System

Fallone, G.; Carlone, Marco; Murray, B. Stuart; Rathee, S; Steciw, S

doi:10.1016/j.ijrobp.2007.07.034

Cited by 6 publications

(4 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, since the high-permeability alloys are magnetic, mechanical support sufficient to prevent displacement is also required. 1,2,14,15 For the in-line case, because the magnetic field is aligned with the gun axis, there is no global deflection away from the beam axis. However, the value of the primary beam current depends on the field strength for values of the field larger than 0.016 T for Litton L-2087 and 0.012 T for Varian VTC6364 due to collision of electrons in the beam with the anode walls.…”

Section: And the Values Reported Inmentioning

confidence: 99%

See 1 more Smart Citation

A study of the effect of in‐line and perpendicular magnetic fields on beam characteristics of electron guns in medical linear accelerators

2011

View full text Add to dashboard Cite

3D space charge simulation of two electron guns, Litton L-2087 and Varian VTC6364, were performed for in-line and perpendicular external magnetic fields. A consistent behavior of Pierce guns in external magnetic fields was proven. For the in-line configuration, the primary beam current does not vanish but a large reduction of beam current (up to 77.1%) is observed at higher field strengths; the beam directionality remains unchanged. It was shown that for a perpendicular configuration the current vanishes due to beam bending under the action of the Lorentz force. For in-line configuration it was determined that the rms beam emittance reaches two minima for relatively high values of the external magnetic field.

show abstract

Section: And the Values Reported Inmentioning

confidence: 99%

“…Another solution is to have the main magnetic field perpendicular to the treatment beam and thus to the electron beam. 14,15 This configuration, referred to from now on as the perpendicular configuration, has no symmetry. A possible geometry which is considered in the present study is shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

A study of the effect of in‐line and perpendicular magnetic fields on beam characteristics of electron guns in medical linear accelerators

2011

View full text Add to dashboard Cite

show abstract

“…Currently, two research groups appear to be developing radiation therapy devices that integrate an MRI unit with a linac: University Medical Center at the University of Utrecht in The Netherlands (see, e.g., Lagendijk et al 2008) and Cross Cancer Institute at the University of Alberta in Canada (see, e.g., Fallone et al 2007). This integration is, of course, extremely enticing, since it could potentially allow for simultaneous patient treatment and imaging, so that we could, for the first time, measure and evaluate the actual delivered dose to patients.…”

Section: Technological Advancementsmentioning

confidence: 99%

Intensity modulated radiation therapy treatment plan optimization

Romeijn

Dempsey

2008

TOP

View full text Add to dashboard Cite

show abstract

“…One compelling approach is to use magnetic resonance imaging (MRI) which is a noninvasive technique that not only allows real time volumetric imaging, but provides exquisite soft tissue contrast to differentiate cancerous from healthy tissue. To date two base MRI-linac configurations have been proposed, i.e., the inline [1][2][3] and the perpendicular 4,5 configurations, which are defined by the relative orientation of the linac with respect to the main magnetic field of the MRI scanner. All these configurations assume a fixed position of the linac with respect to the MRI scanner.…”

Section: Introductionmentioning

confidence: 99%

A novel electron gun for inline MRI‐linac configurations

et al. 2014

View full text Add to dashboard Cite

Purpose: This work introduces a new electron gun geometry capable of robust functioning in the presence of a high strength external magnetic field for axisymmetric magnetic resonance imaging (MRI)-linac configurations. This allows an inline MRI-linac to operate without the need to isolate the linear accelerator (linac) using a magnetic shield. This MRI-linac integration approach not only leaves the magnet homogeneity unchanged but also provides the linac flexibility to move along the magnet axis of symmetry if the source to target distance needs to be adjusted. Methods: Simple electron gun geometry modifications of a Varian 600C electron gun are considered and solved in the presence of an external magnetic field in order to determine a set of design principles for the new geometry. Based on these results, a new gun geometry is proposed and optimized in the fringe field of a 0.5 T open bore MRI magnet (GE Signa SP). A computer model for the 6 MeV Varian 600C linac is used to determine the capture efficiency of the new electron gun-linac system in the presence of the fringe field of the same MRI scanner. The behavior of the new electron gun plus the linac system is also studied in the fringe fields of two other magnets, a 1.0 T prototype open bore magnet and a 1.5 T GE Conquest scanner. Results: Simple geometrical modifications of the original electron gun geometry do not provide feasible solutions. However, these tests show that a smaller transverse cathode diameter with a flat surface and a slightly larger anode diameter could alleviate the current loss due to beam interactions with the anode in the presence of magnetic fields. Based on these findings, an initial geometry resembling a parallel plate capacitor with a hole in the anode is proposed. The optimization procedure finds a cathode-anode distance of 5 mm, a focusing electrode angle of 5• , and an anode drift tube length of 17.1 mm. Also, the linac can be displaced with ±15 cm along the axis of the 0.5 T magnet without capture efficiency reduction below the experimental value in zero field. In this range of linac displacements, the electron beam generated by the new gun geometry is more effectively injected into the linac in the presence of an external magnetic field, resulting in approximately 20% increase of the target current compared to the original gun geometry behavior at zero field. The new gun geometry can generate and accelerate electron beams in external magnetic fields without current loss for fields higher than 0.11 T. The new electron-gun geometry is robust enough to function in the fringe fields of the other two magnets with a target current loss of no more than 16% with respect to the current obtained with no external magnetic fields. Conclusions: In this work, a specially designed electron gun was presented which can operate in the presence of axisymmetric strong magnetic fringe fields of MRI magnets. Computer simulations show that the electron gun can produce high quality beams which can be injected into a straight through linac such as Va...

show abstract

Investigations in the Design of a Novel Linac-MRI System

Cited by 6 publications

References 0 publications

A study of the effect of in‐line and perpendicular magnetic fields on beam characteristics of electron guns in medical linear accelerators

A study of the effect of in‐line and perpendicular magnetic fields on beam characteristics of electron guns in medical linear accelerators

Intensity modulated radiation therapy treatment plan optimization

A novel electron gun for inline MRI‐linac configurations

Contact Info

Product

Resources

About