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Dosimetric validation of a magnetic resonance image gated radiotherapy system using a motion phantom and radiochromic film.

Publication ,  Journal Article
Lamb, JM; Ginn, JS; O'Connell, DP; Agazaryan, N; Cao, M; Thomas, DH; Yang, Y; Lazea, M; Lee, P; Low, DA
Published in: J Appl Clin Med Phys
May 2017

PURPOSE: Magnetic resonance image (MRI) guided radiotherapy enables gating directly on the target position. We present an evaluation of an MRI-guided radiotherapy system's gating performance using an MRI-compatible respiratory motion phantom and radiochromic film. Our evaluation is geared toward validation of our institution's clinical gating protocol which involves planning to a target volume formed by expanding 5 mm about the gross tumor volume (GTV) and gating based on a 3 mm window about the GTV. METHODS: The motion phantom consisted of a target rod containing high-contrast target inserts which moved in the superior-inferior direction inside a body structure containing background contrast material. The target rod was equipped with a radiochromic film insert. Treatment plans were generated for a 3 cm diameter spherical planning target volume, and delivered to the phantom at rest and in motion with and without gating. Both sinusoidal trajectories and tumor trajectories measured during MRI-guided treatments were used. Similarity of the gated dose distribution to the planned, motion-frozen, distribution was quantified using the gamma technique. RESULTS: Without gating, gamma pass rates using 4%/3 mm criteria were 22-59% depending on motion trajectory. Using our clinical standard of repeated breath holds and a gating window of 3 mm with 10% target allowed outside the gating boundary, the gamma pass rate was 97.8% with 3%/3 mm gamma criteria. Using a 3 mm window and 10% allowed excursion, all of the patient tumor motion trajectories at actual speed resulting in at least 95% gamma pass rate at 4%/3 mm. CONCLUSIONS: Our results suggest that the device can be used to compensate respiratory motion using a 3 mm gating margin and 10% allowed excursion results in conjunction with repeated breath holds. Full clinical validation requires a comprehensive evaluation of tracking performance in actual patient images, outside the scope of this study.

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Published In

J Appl Clin Med Phys

DOI

EISSN

1526-9914

Publication Date

May 2017

Volume

18

Issue

3

Start / End Page

163 / 169

Location

United States

Related Subject Headings

  • Respiration
  • Radiotherapy, Image-Guided
  • Radiotherapy Planning, Computer-Assisted
  • Radiometry
  • Phantoms, Imaging
  • Nuclear Medicine & Medical Imaging
  • Movement
  • Magnetic Resonance Imaging
  • Humans
  • Film Dosimetry
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Lamb, J. M., Ginn, J. S., O’Connell, D. P., Agazaryan, N., Cao, M., Thomas, D. H., … Low, D. A. (2017). Dosimetric validation of a magnetic resonance image gated radiotherapy system using a motion phantom and radiochromic film. J Appl Clin Med Phys, 18(3), 163–169. https://doi.org/10.1002/acm2.12088
Lamb, James M., John S. Ginn, Dylan P. O’Connell, Nzhde Agazaryan, Minsong Cao, David H. Thomas, Yingli Yang, Mircea Lazea, Percy Lee, and Daniel A. Low. “Dosimetric validation of a magnetic resonance image gated radiotherapy system using a motion phantom and radiochromic film.J Appl Clin Med Phys 18, no. 3 (May 2017): 163–69. https://doi.org/10.1002/acm2.12088.
Lamb JM, Ginn JS, O’Connell DP, Agazaryan N, Cao M, Thomas DH, et al. Dosimetric validation of a magnetic resonance image gated radiotherapy system using a motion phantom and radiochromic film. J Appl Clin Med Phys. 2017 May;18(3):163–9.
Lamb, James M., et al. “Dosimetric validation of a magnetic resonance image gated radiotherapy system using a motion phantom and radiochromic film.J Appl Clin Med Phys, vol. 18, no. 3, May 2017, pp. 163–69. Pubmed, doi:10.1002/acm2.12088.
Lamb JM, Ginn JS, O’Connell DP, Agazaryan N, Cao M, Thomas DH, Yang Y, Lazea M, Lee P, Low DA. Dosimetric validation of a magnetic resonance image gated radiotherapy system using a motion phantom and radiochromic film. J Appl Clin Med Phys. 2017 May;18(3):163–169.

Published In

J Appl Clin Med Phys

DOI

EISSN

1526-9914

Publication Date

May 2017

Volume

18

Issue

3

Start / End Page

163 / 169

Location

United States

Related Subject Headings

  • Respiration
  • Radiotherapy, Image-Guided
  • Radiotherapy Planning, Computer-Assisted
  • Radiometry
  • Phantoms, Imaging
  • Nuclear Medicine & Medical Imaging
  • Movement
  • Magnetic Resonance Imaging
  • Humans
  • Film Dosimetry