MR-only simulation for prostate RT planning

With its excellent soft-tissue contrast and functional imaging capabilities, MRI has the potential to become a primary imaging technique for radiation therapy (RT) treatment planning and thereby enhance the accuracy of delineating targets and critical structures.

Find out how Philips is going beyond integrating MRI into CT-based RT workflows to develop the first MR-only simulation solution for RT. All based on your need for higher precision RT planning and more streamlined workflow.

3D density maps based on MR imaging alone

Commercial MR imaging solutions are already available that integrate MR imaging into the CT-based RT treatment planning workflow. Since MR lacks electron density information that is required to calculate dosage, current clinical workflows for RT planning include a step that registers MRI to CT. Philips is working on a plug-in extension to its Ingenia MR-RT Oncology system that enables 3D density maps to be created based on MR imaging alone.

RT dose plan based on MR-only simulation (MRCAT). Image courtesy of NKI-AvL, Amsterdam, The Netherlands.

MRCAT

The MRCAT (MR for Calculating ATtenuation) functionality is designed to automatically generate density maps by using a 3D MR imaging protocol together with smart, embedded image-processing that includes auto-segmentation and bulk density assignment algorithms. The resulting CT-like MRCAT images can subsequently be exported to treatment planning systems to aid in dose calculations which are based on MR alone. This would eliminate the need for a pre-treatment CT image and its associated X-ray dose, and save the time and workflow impacts of having to register MRI to CT images. The current workflow is shown in Figure 1 below and the MR-only simulation workflow is shown in Figure 2.

Figure 1 shows the current CT & MR workflow for RT treatment planning

Figure 2 shows the workflow with MR-only simulation for RT treatment planning

Image 1: MRCAT image based on atlas-based classification of 5 tissue types (air, fat, water, bone marrow and cortical bone)
Image courtesy of Docrates Cancer Center, Helsinki, Finland

Image 2: RT dose plan based on MR-only simulation, overlay on T2W 3D imaging
Image courtesy of Docrates Cancer Center, Helsinki, Finland

MRCAT for prostate applications

Philips is currently working with clinical partners to demonstrate the potential of MR-only simulation. The first application planned for the MR-only simulation is prostate, which is one of the main applications to harness MRI’s soft-tissue contrast for RT planning purposes.

Image 3: Images of MR-only simulation used for prostate RT treatment planning.
Image courtesy of Docrates Cancer Center, Helsinki, Finland

Plug-in for Ingenia MR-RT Oncology Configuration

The MR-only simulation is being developed as a plug-in extension for the Ingenia MR-RT Oncology Configuration. This comprehensive solution is designed to provide high-quality MR images acquired in the treatment position that can help boost accuracy in delineating tumors and critical structures for enhanced RT treatment planning.

The Ingenia offers a combination of patient positioning tools and versatile coil solutions to support reproducible MR imaging in the treatment position.

Dedicated imaging for RT planning is underpinned by Ingenia’s excellent geometric accuracy and large field of view. These are combined with customized MR imaging protocols for the main applications in RT: prostate, female pelvis, brain, and head & neck.

A ready-to-use geometric quantitative analysis package allows clinicians to perform routine volumetric evaluations of the scanner’s geometric fidelity in an efficient and repeatable manner.

For more information

More information on available MR Therapy solutions.

Written by:

David Spagnoli

Senior Field Marketing Manager, BG Imaging Systems

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*This is Works in Progress for prostate applications being carried out by Philips Research.

AAPM 2014:
Schadewaldt, et al., Comparison of Dose calculation on automatically generated MR-based ED maps and corresponding patient CT for clinical prostate EBRT plans. SU-E-J-141, AAPM 2014
(http://www.aapm.org/meetings/2014AM/PRAbs.asp?mid=90&aid=24171)

ISMRM 2014:
Helle, et. al. Evaluation of Dixon based Soft Tissue and Bone Classification in the Pelvis for MR-only-based Radiation Therapy Planning. 1128, ISMRM 2014

Innovations – prostate cancer

MR-only simulation for prostate RT planning*