Conductive Phantom for MR Coil Loading and PET Calibration
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Solution Overview
Problem
Conventional phantoms are inadequate for quality control measurements of fully integrated magnetic resonance/PET scanners, as they do not adequately load the MR coil, potentially leading to excessive current and damage when maximum RF power is applied, and require separate calibration for PET and MR functionalities.
Innovation Solution
A phantom with uniformly distributed radiation activity within an electrically conductive elastomeric binder, featuring ether-based thermoplastic polyurethane as the matrix and electrically conductive fibers like carbon, aluminum, or semiconducting polymers, ensuring appropriate electrical resistivity and conductivity to safely load the MR coil and maintain PET imaging accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional phantom is used for quality control measurement, then the PET scanning functionality can be assessed, but the MR coil cannot be adequately loaded, leading to excessive current and potential damage when maximum RF power is applied
Solution Approach 1:
The phantom uses a composite material consisting of an elastomeric binder mixed with electrically conductive fibers (such as carbon, aluminum, copper, or semiconducting polymer fibers). This composite provides both the necessary electrical conductivity to load the MR coil and the physical properties required for PET imaging, resolving the contradiction between MR coil safety and phantom functionality.
Solution Approach 2:
The electrical resistivity of the phantom matrix is specifically controlled to be between 10 to 200 Ωcm by adjusting the concentration and distribution of conductive fibers in the elastomeric binder. This parameter optimization ensures adequate MR coil loading while maintaining PET imaging capabilities, preventing excessive current damage to the MR coil.
2Measurement precision
If separate phantoms are used for PET and MR calibration, then each functionality can be calibrated accurately, but the device complexity and time required for quality control increases
Solution Approach 1:
The phantom is designed to serve dual purposes: it provides uniform radiation activity distribution for PET scanner calibration and adequate electrical conductivity for MR coil loading. This multi-functional design eliminates the need for separate PET and MR phantoms, reducing device complexity while maintaining calibration accuracy for both modalities.
Solution Approach 2:
The invention merges the functions of PET calibration phantom and MR loading phantom into a single integrated phantom. The elastomeric matrix with conductive fibers simultaneously provides the radiation activity distribution needed for PET and the electrical conductivity needed for MR, combining two separate calibration requirements into one unified solution.
3Reliability
If maximum RF power is applied to an unloaded MR coil, then the coil could be damaged due to excessive current, but using a conductive phantom may interfere with PET imaging signals
Solution Approach 1:
The electrical resistivity is optimized to a specific range (10 to 200 Ωcm) that provides sufficient conductivity to load the MR coil and prevent excessive current, while remaining low enough not to significantly interfere with PET imaging signals. This precise parameter control balances MR coil protection with PET signal integrity.
Solution Approach 2:
The conductive fibers are distributed throughout the elastomeric binder to create localized conductive pathways that adequately load the MR coil. The distribution density and pattern are controlled to provide sufficient MR loading without creating large-scale conductive structures that would interfere with PET signal detection, achieving local optimization of electrical properties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The phantom effectively loads the MR coil, preventing damage from excessive current while allowing simultaneous MR and PET imaging, thereby enabling accurate quality control and eliminating the need for separate phantoms, ensuring safe and accurate scanner calibration.
Implementation Method 1
The phantom features radiation activity distributed throughout an electrically conductive binder. Suitably, the binder is elastomeric and includes electrically conducting fibers distributed throughout it to set the conductivity of the phantom to a desired level.
Implementation Method 2
the MR coil of the scanner has to experience a certain load in order to dampen the resonance peak sufficiently, even when maximum RF power is applied to the coil
Implementation Method 3
The phantom may have distributed radiation activity of about 1.5 mCi or less that is suitably provided by Ge68
Data Source
AI summary
A phantom for use in quality control measurement of a fully integrated magnetic resonance/PET scanner is disclosed. The phantom features radiation activity distributed throughout an electrically conductive binder. Suitably, the binder is elastomeric and includes carbon fibers distributed throughout it to set the conductivity of the phantom to a desired level. The phantom is applicable to various multimodality integrated medical imaging systems such as MR/SPECT and MR/CT in addition to MR/PET.