Magphan RT: MR Imaging QA for radiotherapy

 
 
 
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Comprehensive quantitative image quality analysis for MR in radiotherapy

 

Meeting Specific QA Needs

MRI manufacturers have made great strides in reducing MR system distortion. Maintaining acceptable levels of distortion relies on properly controlling a long chain of conditions. A robust system of quality control measuring key imaging performance characteristics to detect significant deviations is critical for maintaining safe and effective clinical operations.

The Magphan RT series of phantoms from The Phantom Laboratory meet the specific QA needs for MR imagers used for MR guided surgery and radiotherapy planning and guidance where measurement of large fields of view is required for the torso sizes encountered in clinical practice.

Image Owl performs an automated analysis of the Magphan RT phantoms within its Total QA service. Purchase of a Magphan RT phantom includes access to this service for a two-year period. A moderate annual subscription cost applies after the first two years.

The Magphan RT phantom analysis is automated. The user simply uploads a DICOM scan into a drag-and-drop interface. The service recognizes the phantom’s configuration, analyzes the images and produces a comprehensive report. Analysis results are saved in a cloud-based database for longitudinal studies, process control, and inter-machine comparisons.

For further automation, users have access to Total QA’s API that allows users to extend the system with custom analyses or interfaces and automated uploads.

The service is accessible from any web-enabled device and requires no local installation. Updates to the service are automatic and require no user interactions.

 
 

The Main Magphan RT Analysis Includes

 

Geometric Distortion

The locations of several hundred 1-cm sphere fiducials are measured across the volume of the phantom. These measured locations are compared to known locations to generate a 3D distortion map. The phantom modules are designed to fit together precisely and the analysis accounts for any residual positional offsets between components. Beyond producing a distortion map, the system tracks several key indicators such as maximum and mean high 10% distortion along the cardinal axes. Analysis of optimized gradient rescaling factors for different objectives is included.

 
 

Uniformity

Uniformity can be a useful indicator for common failure mechanisms in subsystems like the RF coil element. The uniformity is measured at several hundred uniform spherical sub-volumes throughout the phantom. The mean signal, normalized standard deviation, and spread are calculated.

 
 
 

Laser Alignment

The phantom contains markers for alignment with positioning lasers. The analysis provides data on translation and rotation of the phantom in all three cardinal axes.

 
 
 

MR Imaging QA for Radiotherapy from ImageOwl

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Slice Thickness

We provide slice thickness ramps to provide an objective slice thickness measurement on all three orthogonal axes. The automated routine provides higher quality slice thickness measurements versus manual measurements on clinical sequences.

 
 
 

Resolution

The Magphan RT system measures the point spread and modulation transfer functions from circular features in the phantom all three image planes.

 
 
 

Signal-to-Noise Ratio

The signal-to-noise ratio is measured at several places throughout the phantom. Longitudinal tracking of SNR can give early warning of component degradation or failure.