MRI-Compatible Cooling Unit for PET Detector Temperature Stability
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Solution Overview
Problem
The integration of PET detectors with MRI systems poses challenges due to magnetic fields, which cause heating issues such as eddy current, ohmic, and Lorentz forces, making conventional metal cooling structures ineffective, and solid-state sensors like APDs and SiPMs prone to temperature fluctuations.
Innovation Solution
A cooling unit with a non-electrically conductive encasement body and a metal conduit with series of fins, configured to minimize heating from eddy currents and Lorentz forces, using high thermal conductivity materials like copper alloys, and incorporating non-conductive inserts for enhanced cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If solid-state sensors (APDs/SiPMs) are used in MRI environment, then magnetic field sensitivity is reduced, but temperature stability deteriorates due to gain fluctuations
Solution Approach 1:
The patent applies parameter changes by actively controlling the temperature of the solid-state sensor to maintain stable operation. A cooling system with temperature sensing and control circuitry adjusts cooling parameters in real-time to compensate for temperature fluctuations, thereby stabilizing the sensor gain and ensuring reliable detection performance in the MRI environment.
Solution Approach 2:
The patent introduces an intermediary cooling system between the solid-state sensor and the MRI environment. This cooling intermediary includes a cooling element in thermal contact with the sensor, through which a cooling fluid circulates to actively regulate sensor temperature, isolating the sensor from harmful thermal fluctuations while maintaining magnetic field insensitivity.
2Temperature
If metal cooling components are used, then thermal conductivity is improved, but heating from eddy currents and Lorentz forces increases
Solution Approach 1:
The patent employs composite materials by combining electrically conductive metal components with electrically insulating materials in the cooling system. The cooling element uses metal portions for efficient heat conduction while incorporating insulating portions to block eddy current paths, creating a composite structure that achieves both effective cooling and minimal electromagnetic heating in the MRI environment.
Solution Approach 2:
The patent applies local quality by creating regions with different electrical conductivity properties within the cooling system. Metal portions provide high thermal conductivity for cooling, while insulating portions are strategically placed to interrupt eddy current paths and reduce Lorentz forces, allowing each local region to optimize its function for either thermal management or electromagnetic compatibility.
3Reliability
If conventional PMTs are used, then temperature stability is improved, but device size increases and magnetic field compatibility decreases
Solution Approach 1:
The patent applies parameter changes by actively controlling the operating temperature of compact solid-state sensors through a cooling system. This enables the small sensors to maintain the temperature stability previously only achievable with large PMTs, while achieving both miniaturization and stable performance through active thermal management rather than passive environmental isolation.
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 solution provides effective cooling for PET detectors in MRI environments by reducing heating from magnetic field-induced forces and maintaining sensor stability, ensuring long-term operation of PET detectors.
Implementation Method 1
a metal conduit disposed in the encasement body substantially parallel to the first surface. Additionally, the apparatus also includes a series of metal fins disposed in the encasement body and extending from the conduit
Implementation Method 2
a cooling fluid device coupled to the metal conduit and configured for directing a cooling fluid through the metal conduit
Implementation Method 3
which are susceptible to eddy current, ohmic, and Lorentz forces
Implementation Method 4
a series of metal fins disposed in the encasement body and extending from the conduit
Data Source
AI summary
A cooling unit operating in a magnetic field is provided. The cooling unit includes an encasement body having a non-electrically conductive composition and defining a first and second opposing planar surface. The cooling unit also includes a metal conduit disposed in the encasement body substantially parallel to the first surface. Additionally, the cooling unit also includes a series of metal fins disposed in the encasement body and extending from the conduit. In some configurations the fins can be substantially parallel to the first surface. Further, in some configurations, non-electrically conductive inserts having a thermal conductivity greater than a thermal conductivity of the encasement body can be disposed in a portion of the encasement body between one of the first and second surfaces and one or more of the metals fins.