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Key visual MRI for Radiation Therapy

MR-only Radiotherapy Planning

Powered by syngo.via RT Image Suite

While MR provides excellent soft-tissue contrast and functional information, CT is still required for electron density information for accurate dose calculation. As a result, many institutions have to adapt their RT treatment planning workflow, in which patients are normally scanned on both imaging modalities. Fusing CT and MRI modalities makes the workflow more complicated and adds uncertainties in the planning process.1, 2

MR-based Synthetic CT offers the possibility of combining the superior soft-tissue contrast of MRI for organs-at-risk and target delineation with dosimetric planning. An MR-only workflow eliminates the need for CT to MRI registration, reducing systematic registration errors and unnecessary ionizing radiation from CT scans.

Discover our MR-only workflow for brain and pelvis.

Features & Benefits

MR-based Synthetic CT3

Enabling a straight forward MR-only workflow for RT planning with our AI-powered algorithm for pelvis and brain.

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Challenges of combined MR and CT workflow

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Key features of MR-based Synthetic CT

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Challenges of MR-based Synthetic CT

Courtesy of Universitätsklinikum Erlangen, Strahlenklinik, Germany 

Challenges of combined MR and CT workflow 

  • Accurate image registration
  • Patient scheduling
  • Resource utilization & reimbursement
Challenges of MR-based Synthetic CT
Key features of MR-based Synthetic CT
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MR-based Synthetic CT results for pelvis and brain

Synthetic CT Re-imagined

Image examples brain

Synthetic CT Re-imagined

Image examples pelvis

The MR-only radiotherapy planning workflow typically encompasses five main areas

Evaluation

Synthetic CT Line Profile Comparison
Courtesy of Centre Hospitalier de l'Université de Montréal, Canada

An internal validation of geometric fidelity and HU unit accuracy

The geometric fidelity test was passed with an average symmetric surface distance (ASSD) <1mm for brain and pelvis, which is below the in-plane pixel resolution of 1 mm (2 mm) for the brain (pelvis) and therefore negligible. 

For HU accuracy, line profiles from CT and MR-based Synthetic CT of the same patient were compared as shown in the image.

Clinical Use

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Dose and Positioning Evaluation of MR-based Synthetic CT

Clinical evaluation and image courtesy of Brigham & Women’s Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, USA

Dosimetric and position results in the pelvis

  • <1% dose difference in the CTV and evaluated OARs
  • 1%/2 mm gamma analysis agreement of 98.9 ± 0.3%
  • Absolute differences in positioning with CBCT <1 mm
Dose and Positioning Evaluation of MR-based Synthetic CT
Dose Distribution on MR-based Synthetic CT
Synthetic CT Checkerboard Tool
Synthetic CT Calibration Curve
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1
K. K. Brock, “Adaptive Radiotherapy: Moving Into the Future”, Semin. Radiat. Oncol., vol. 29, no. 3, pp. 181–184, 2019.
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K. Latifi, J. Caudell, G. Zhang, D. Hunt, E. G. Moros, and V. Feygelman, “Practical quantification of image registration accuracy following the AAPM TG-132 report framework”, J. Appl. Clin. Med. Phys., vol. 19, no. 4, pp. 125–133, 2018.
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MR-based Synthetic CT (AI algorithm) is an optional feature available in syngo.via RT Image Suite starting from software version VB60.
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The name "myExam RT Assist" is used starting from software version syngo MR XA50. In former software versions it is called "RT Dot Engine“.
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Available on syngo MR XA20 and later software versions with RT Pro edition for MAGNETOM Vida and Sola.
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The data acquisition protocols for MR-based Synthetic CT are available with syngo MR XA11A and later software versions with RT Pro edition for MAGNETOM Sola and Vida, with syngo XA30 and later software Versions for MAGNETOM Aera and MAGNETOM Skyra.

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VMAT plan generated internally by Varian a Siemens Healthineers Company for demonstration purposes, not clinically used.
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Compressed Sensing GRASP-VIBE for other regions than liver is not for sale in the U.S. Intended Use: Compressed Sensing GRASP-VIBE (GRASP = Golden-angle Radial Sparse Parallel MRI) is intended to be used in dynamic and/or non-contrast liver examinations to support patients who cannot reliably hold their breath for a conventional breath-hold measurement.

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Checkerboard is a feature available in syngo.via RT Image Suite starting from software version VB60.