Background

One of the UK’s leading cancer centres, The Clatterbridge Cancer Centre NHS Foundation Trust, required help to map distortion in MRI scanners.

Geometric distortion in MRI scanners hinders their ability to accurately reproduce the dimensions of the object in the images. This distortion creates issues in applications which require high spatial accuracy, such as image-guided surgery and radiotherapy treatment planning, for which MRI is becoming an increasingly popular modality due to the excellent soft tissue contrast it provides.

Measurement of geometric distortion in two dimensions (the image plane) is a standard component of quality assurance in MRI. But measurement of geometric distortion in all three spatial dimensions, including the slice-direction as well, is not commonly performed due to difficulty in designing, building and maintaining the necessary test objects (phantoms). Such a phantom must have control points that are identifiable in the images and distinguishable from each other in all three spatial directions.

This innovative work has formed part of my MSc project, which is focused around mapping geometric distortion in MRI scanners.
The work undertaken by Sensor City will have a real impact on the development of this research area and I’m looking forward to working with them again in the future.”

Chris Murphy, Medical Physics Trainee, The Clatterbridge Cancer Centre NHS Foundation Trust

Approaching Sensor City

The recent emergence of additive manufacturing (3D printing) has opened up new possibilities in phantom design and construction. Designs that would have taken considerable amounts of time to build manually can now be constructed automatically by machine, potentially saving hospital staff valuable time and money. Additionally, any centre with access to a 3D printer could build an identical phantom, allowing multiple centres to use the same model and reliably compare their results.

The Engineers at Sensor City were approached to provide support in developing a phantom, as the purpose-built rapid prototyping facility is equipped with a range of 3D printers and design software capabilities.

Partner Support

Using computer-aided-design (CAD) and 3D printing technology, a phantom calibration tower was manufactured using Sensor City’s Ultimaker 3D printer and Pro PLA materials. It is capable of measuring geometric distortion in all three dimensions of the MRI scanner, which will result in considerable benefits for the end user.

Created alongside this, was a suitable MRI imaging protocol, that can obtain the necessary images for analysis of distortion.

Working into the future

Going forwards, Clatterbridge Cancer Centre will be using the results to (hopefully) improve the accuracy of their MRI images, which could be useful for any high-precision applications based on MR-imaging, like radiotherapy treatments.

Additionally, a specific software application will be developed to analyse the MRI images, and derive the geometric distortion map.

Results

The creation of the 3D printed prototype should lead to enhanced analysis of MRI imaging, subsequently resulting in accuracy improvements, particularly in radiotherapy treatment.

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