Characterization of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy system

Yanle Hu, Leith Rankine, Olga L. Green, Rojano Kashani, H. Harold Li, Hua Li, Roger Nana, Vivian Rodriguez, Lakshmi Santanam, Shmaryu Shvartsman, James Victoria, H. Omar Wooten, James F. Dempsey, Sasa Mutic

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Purpose: To characterize the performance of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy (MR-IGRT) system. Methods: The imaging performance characterization included four components: ACR (the American College of Radiology) phantom test, spatial integrity, coil signal to noise ratio (SNR) and uniformity, and magnetic field homogeneity. The ACR phantom test was performed in accordance with the ACR phantom test guidance. The spatial integrity test was evaluated using a 40.8×40.8×40.8 cm3 spatial integrity phantom. MR and computed tomography (CT) images of the phantom were acquired and coregistered. Objects were identified around the surfaces of 20 and 35 cm diameters of spherical volume (DSVs) on both the MR and CT images. Geometric distortion was quantified using deviation in object location between the MR and CT images. The coil SNR test was performed according to the national electrical manufacturers association (NEMA) standards MS-1 and MS-9. The magnetic field homogeneity test was measured using field camera and spectral peak methods. Results: For the ACR tests, the slice position error was less than 0.10 cm, the slice thickness error was less than 0.05 cm, the resolved high-contrast spatial resolution was 0.09 cm, the resolved low-contrast spokes were more than 25, the image intensity uniformity was above 93%, and the percentage ghosting was less than 0.22%. All were within the ACR recommended specifications. The maximum geometric distortions within the 20 and 35 cm DSVs were 0.10 and 0.18 cm for high spatial resolution three-dimensional images and 0.08 and 0.20 cm for high temporal resolution two dimensional cine images based on the distance-to-phantom-center method. The average SNR was 12.0 for the body coil, 42.9 for the combined torso coil, and 44.0 for the combined head and neck coil. Magnetic field homogeneities at gantry angles of 0°, 30°, 60°, 90°, and 120° were 23.55, 20.43, 18.76, 19.11, and 22.22 ppm, respectively, using the field camera method over the 45 cm DSV. Conclusions: The onboard imaging unit of the first commercial MR-IGRT system meets ACR, NEMA, and vendor specifications.

Original languageEnglish (US)
Pages (from-to)5828-5837
Number of pages10
JournalMedical Physics
Volume42
Issue number10
DOIs
StatePublished - Oct 1 2015

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Image-Guided Radiotherapy
Radiology
Magnetic Resonance Spectroscopy
Signal-To-Noise Ratio
Magnetic Fields
Magnetic Resonance Imaging
Torso
Three-Dimensional Imaging
Neck
Head

Keywords

  • MR-IGRT
  • onboard imaging unit
  • performance characterization

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging
  • Medicine(all)

Cite this

Characterization of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy system. / Hu, Yanle; Rankine, Leith; Green, Olga L.; Kashani, Rojano; Li, H. Harold; Li, Hua; Nana, Roger; Rodriguez, Vivian; Santanam, Lakshmi; Shvartsman, Shmaryu; Victoria, James; Wooten, H. Omar; Dempsey, James F.; Mutic, Sasa.

In: Medical Physics, Vol. 42, No. 10, 01.10.2015, p. 5828-5837.

Research output: Contribution to journalArticle

Hu, Y, Rankine, L, Green, OL, Kashani, R, Li, HH, Li, H, Nana, R, Rodriguez, V, Santanam, L, Shvartsman, S, Victoria, J, Wooten, HO, Dempsey, JF & Mutic, S 2015, 'Characterization of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy system', Medical Physics, vol. 42, no. 10, pp. 5828-5837. https://doi.org/10.1118/1.4930249
Hu, Yanle ; Rankine, Leith ; Green, Olga L. ; Kashani, Rojano ; Li, H. Harold ; Li, Hua ; Nana, Roger ; Rodriguez, Vivian ; Santanam, Lakshmi ; Shvartsman, Shmaryu ; Victoria, James ; Wooten, H. Omar ; Dempsey, James F. ; Mutic, Sasa. / Characterization of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy system. In: Medical Physics. 2015 ; Vol. 42, No. 10. pp. 5828-5837.
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AU - Nana, Roger

AU - Rodriguez, Vivian

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AU - Victoria, James

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N2 - Purpose: To characterize the performance of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy (MR-IGRT) system. Methods: The imaging performance characterization included four components: ACR (the American College of Radiology) phantom test, spatial integrity, coil signal to noise ratio (SNR) and uniformity, and magnetic field homogeneity. The ACR phantom test was performed in accordance with the ACR phantom test guidance. The spatial integrity test was evaluated using a 40.8×40.8×40.8 cm3 spatial integrity phantom. MR and computed tomography (CT) images of the phantom were acquired and coregistered. Objects were identified around the surfaces of 20 and 35 cm diameters of spherical volume (DSVs) on both the MR and CT images. Geometric distortion was quantified using deviation in object location between the MR and CT images. The coil SNR test was performed according to the national electrical manufacturers association (NEMA) standards MS-1 and MS-9. The magnetic field homogeneity test was measured using field camera and spectral peak methods. Results: For the ACR tests, the slice position error was less than 0.10 cm, the slice thickness error was less than 0.05 cm, the resolved high-contrast spatial resolution was 0.09 cm, the resolved low-contrast spokes were more than 25, the image intensity uniformity was above 93%, and the percentage ghosting was less than 0.22%. All were within the ACR recommended specifications. The maximum geometric distortions within the 20 and 35 cm DSVs were 0.10 and 0.18 cm for high spatial resolution three-dimensional images and 0.08 and 0.20 cm for high temporal resolution two dimensional cine images based on the distance-to-phantom-center method. The average SNR was 12.0 for the body coil, 42.9 for the combined torso coil, and 44.0 for the combined head and neck coil. Magnetic field homogeneities at gantry angles of 0°, 30°, 60°, 90°, and 120° were 23.55, 20.43, 18.76, 19.11, and 22.22 ppm, respectively, using the field camera method over the 45 cm DSV. Conclusions: The onboard imaging unit of the first commercial MR-IGRT system meets ACR, NEMA, and vendor specifications.

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