MR-only radiotherapy planning with Synthetic CT

MR-only radiotherapy planning with Synthetic CTPowered by syngo.via RT Image Suite

While MR provides excellent soft-tissue imaging, CT is still essential for providing electron density information for dose planning which MR images cannot deliver. As a result, many institutions have to adapt their RT treatment planning workflow, in which patients are normally scanned on both imaging modalities. This makes the workflow more complicated and also challenging in regards to image co-registration. Synthetic CT1 from Siemens Healthineers allows you to perform an MR-only radiotherapy planning workflow. Synthetic CT1, as part of syngo.via RT Image Suite, derives a CT-like image from a series of MR sequences and can be used for dose calculation, all without the need for a CT scan.

Siemens Healthineers is proud to release a new, AI-based Synthetic CT solution with syngo.via RT Image Suite VB60. This new Synthetic CT version provides a few advantages over the previous solution, with the main goal of having an MR-only workflow remaining the same.  

Pelvis Brain

The new Synthetic CT is an AI-powered algorithm for MR only workflows in brain and pelvis. The new Synthetic CT solution provides a number of key advantages and improvements over the previous solution:

  • Reduced scan time - only one T1 VIBE Dixon (in phase and opposed phase) scan is needed for both brain and pelvis acquisitions
  • Continuous HU values for both brain and pelvis for more CT comparable HU values for different tissue types. This also provides a CT-like image as known from conventional CT Sim planning
  • Quick patient check in syngo.via
  • relative electron density or mass density output - for your clinical workflow
Synthetic CT - Imaging for planning and simulation
These MR sequences are needed to generate the Synthetic CT1 brain image.

Imaging starts with the RT Dot Engine, which provides workflow guidance with dedicated RT protocols for brain, head/neck, and pelvis to help achieve consistent data acquisition and geometric accuracy. Pictograms and hints show how to plan an exam, and guide users through the scan.

Synthetic CT - Post-processing and assessment

Post-processing is made simple with syngo.via RT image Suite. After performing the necessary MR scans, the Synthetic CT1 image is created automatically and displayed on the scanner console.

Synthetic CT - Contouring

Afterwards, the Synthetic CT1 image can be displayed alongside other MR images for patient marking, assessment, and parallel contouring. Once preparation is completed in RT Image Suite, users can then export the images to their treatment planning system for dose calculation.

Synthetic CT - Dosimetric planning
Comparison of dose calculation on conventional CT and on Synthetic CT1, both with MR-defined contours.

Studies have shown that dose calculation on Synthetic CT1 images correlates very closely to that on a conventional CT image.

Synthetic CT - Treatment monitoring and adaptation

It is also important that patient response is monitored and that treatment plans are adapted according to the response assessment. To support physicians with response assessment, Siemens Healthineers offers a wide range of applications and techniques which can be utilized for this evaluation. MR OncoCare, for instance, can assist you in response assessment and treatment monitoring by providing a quantitative assessment of a lesion’s functional characteristics.

Synthetic CT - RT planning
MR-supported RT planning and follow-up in the brain.

Diffusion-weighted imaging, or DWI, is another technique often used in radiation therapy to assess tumor response to treatment. DWI can provide valuable information about tissue cellularity, but is by nature more susceptible to increased distortions. Siemens Healthineers’ RESOLVE technique can help correct distortion artifacts caused by for example dental implants with DWI in brain imaging.

Pre-treatment
Image courtesy of University Hospital Tuebingen, Germany.

Finally, dynamic contrast-enhanced MRI can also help assess tumor function and response by showing blood flow and blood volume. This can be utilized as tumors have a tendency to enhance contrast earlier than surrounding tissue. For contrast-enhanced imaging, we offer our unique technique called Compressed Sensing GRASP-VIBE3, which combines high robustness for involuntary motion with high temporal resolution to capture the contrast dynamics.

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