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Dose uncertainty and resolution of polymer gel dosimetry using an MRI guided radiation therapy system's onboard 0.35 T scanner.

Publication ,  Journal Article
Maraghechi, B; Gach, HM; Setianegara, J; Yang, D; Li, HH
Published in: Phys Med
May 2020

Magnetic Resonance Imaging (MRI) scanners are widely used for 3D gel dosimeters readout. However, limited access to MRI scanners is a challenge in MRI-based gel dosimetry. Recent clinical implementation of MRI-guided radiation therapy machines provides potential opportunities for onboard gel dosimetry using its MRI subsystem. The objective of this study was to investigate the feasibility of gel dosimetry using ViewRay's onboard 0.35 T MRI scanner. A BANG® polymer gel dosimeter was irradiated by three beams of 3 × 3 cm2 field size. The T2 relaxation rate (R2) of the irradiated gel was measured using a Philips 1.5 T Ingenia MRI and a ViewRay 0.35 T onboard MRI and spin-echo pulse sequences. The number of signal averages (NSA) was set to 16 for the ViewRay acquisitions and one for the Philips 1.5 T MRI to achieve similar signal-to-noise ratios. The in-plane spatial resolution was 1.5 × 1.5 mm2 and the slice thickness was 5 mm. The relative dose uncertainty was obtained using R2 versus dose curves to compare the performance of dosimetry using the two different MRIs and field strengths. The dose uncertainty decreased from 12% at 2 Gy to 3.5% at 7.5 Gy at 1.5 T. The dose uncertainty decreased from 13% at 2 Gy to 4% at 7.5 Gy with NSA = 16 and 3 × 3 mm2 pixel size, and from 10.5% at 2 Gy to 3.2% at 7.5 Gy with NSA = 16 and denoised R2 maps (1.5 × 1.5 mm2 pixel size) at 0.35 T. The mean of dose resolution was 0.4 Gy at 1.5 T while the mean of dose resolution was 0.8 Gy and 0.64 Gy at 0.35 T by downsampling and denoising the R2 map, respectively. Therefore, comparable dose uncertainty was achievable using the ViewRay's onboard 0.35 T and Philips 1.5 T MRI scanners. 3D gel dosimetry using onboard low-field MRI scanner provides ViewRay users a 3D high resolution dosimetry option besides film and ionization chamber.

Duke Scholars

Published In

Phys Med

DOI

EISSN

1724-191X

Publication Date

May 2020

Volume

73

Start / End Page

8 / 12

Location

Italy

Related Subject Headings

  • Radiotherapy, Image-Guided
  • Radiotherapy Dosage
  • Radiometry
  • Radiation Dosage
  • Polymers
  • Nuclear Medicine & Medical Imaging
  • Magnetic Resonance Imaging
  • Humans
  • Gels
  • Feasibility Studies
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Maraghechi, B., Gach, H. M., Setianegara, J., Yang, D., & Li, H. H. (2020). Dose uncertainty and resolution of polymer gel dosimetry using an MRI guided radiation therapy system's onboard 0.35 T scanner. Phys Med, 73, 8–12. https://doi.org/10.1016/j.ejmp.2020.04.004
Maraghechi, Borna, H Michael Gach, Jufri Setianegara, Deshan Yang, and H Harold Li. “Dose uncertainty and resolution of polymer gel dosimetry using an MRI guided radiation therapy system's onboard 0.35 T scanner.Phys Med 73 (May 2020): 8–12. https://doi.org/10.1016/j.ejmp.2020.04.004.
Maraghechi, Borna, et al. “Dose uncertainty and resolution of polymer gel dosimetry using an MRI guided radiation therapy system's onboard 0.35 T scanner.Phys Med, vol. 73, May 2020, pp. 8–12. Pubmed, doi:10.1016/j.ejmp.2020.04.004.

Published In

Phys Med

DOI

EISSN

1724-191X

Publication Date

May 2020

Volume

73

Start / End Page

8 / 12

Location

Italy

Related Subject Headings

  • Radiotherapy, Image-Guided
  • Radiotherapy Dosage
  • Radiometry
  • Radiation Dosage
  • Polymers
  • Nuclear Medicine & Medical Imaging
  • Magnetic Resonance Imaging
  • Humans
  • Gels
  • Feasibility Studies