Process chillers for precision cooling of low viscosity industrial fluids are routinely used in hospitals and laboratories to control the temperature in a variety of applications including rotary evaporation, reaction vessel jacketing, diffusion pumps, laser systems, electron microscopes and linear accelerators. Two of the most prevalent applications of this technology include heat load management in magnetic resonance imaging (MRI) and computed tomography (CT) scanners.
This blog explores how process water-chilling technology is applied to these critical applications.
What is an MRI scanner?
MRI (magnetic resonance imaging) is a non-invasive scanning technology that produces cross-sectional images of the body. It is used in a range of medical fields including:
MRI scanning can differentiate soft tissue structures in any plane, making it an invaluable diagnostic tool. MRI scanners generate a strong magnetic field that is used in conjunction with radiofrequency currents to stimulate specific molecules in the body. The behavior of the molecules can be used to generate a three-dimensional image of body tissues. Example MRI images are shown below:
MRI operation and cooling requirements
Cold head recondensing of helium
All MRI scanners contain superconductive magnetic coils. These coils must be cooled to approximately -296° celsius to promote superconducting properties in the metal alloys. The low cooling temperature is achieved by circulating liquid helium around the magnetic coils.
An average-sized MRI scanner contains approximately 1,700L of helium. A mechanical device called a “cold-head” is used to minimize the loss of helium. The device re-condenses gaseous helium back to a liquid state after contact with the magnets.
Below is a diagram of the cold-head circuit:
Heat load reduction
In addition to controlling the ambient temperature around the MRI scanner, heat must be removed from several processes during machine operation. These include:
- A helium compressor is used in conjunction with the cold-head to compresses the gaseous helium prior to recirculation to the MRI magnet. The heat load from the compressor motor must be removed to maintain the efficiency of the helium circuit.
- RF cabinets and amplifiers generate electrical heat that must be removed in order to protect the equipment from heat-related failures.
- Direct cooling around the magnetic coils is employed to remove ambient heat and improve the magnet cooling efficiency (compliments the HVAC control of the room temperature).
Benefits of using a water chiller for an MRI scanner
Chillers can be integrated into the MRI system to provide cooling capacity in several ways. In most instances, the chiller is used in conjunction with a heat exchange cabinet (HEC) located in the equipment room (kept separate to the magnet room). The HEC utilizes heat exchangers that can be connected to the water supply from the chiller.
Below is an example layout of the HEC:
Computerized tomography scanning
What is a CT scanner?
Computerized tomography (also referred to as computerized axial tomography, CAT) is a scanning technique that uses x-ray to produce cross-sectional images of the body. The images provide more detail of body structures when compared to a standard x-ray. Hospitals have a high demand for CT scans due to the range of diseases and conditions that can be diagnosed.
The CT scanner uses motorized x-ray tubes that move around the patient. The x-ray that passes through the patient is picked up by detectors that send the data to a computer for processing.
Benefits of using a water chiller for a CT scanner
Heat load reduction
- The electrical componentry and x-ray tubes in CT scanners draw >95 KW of power. Excess heat in the scanner gantry must be removed on scan completion to allow for the next scan to be initiated.
- Shortened cooling time - the x-ray tubes can take between 20 – 30 minutes to cool sufficiently without assistance. A water chiller significantly reduces the cooling time and protects the scanner from overheating. Patient throughput, enhanced care and hospital efficiency are greatly improved. Unnecessary maintenance related to process overheating is also reduced helping to drive down overall operation costs.
Why Parker chillers?
The Parker Hyperchill Water Chiller has a proven track record of performance with all the major manufacturers of MRI and CT scanner systems. Key benefits include:
- Non-ferrous hydraulic circuit for increased reliability and reduced maintenance costs.
- Large water tank capacity increasing both process cooling stability and compressor lifespan. Reduced maintenance cost and hence the cost of ownership.
- Built-in maintenance indicators and fault switches safeguard the capital equipment.
- Configurable with a 5 bar pump to meet system pressure requirements.
The selection of the most reliable and efficient water chiller will help assure the uninterrupted use of MRI and CT scanners in diagnosing patient conditions. Parker Hyperchill Chillers offer state-of-the-art components and systems that protect these valuable assets from heat-related failures, improve efficiency and assure consistent, trouble-free performance.
After more than a century of experience serving our customers, Parker is often called to the table for the collaborations that help to solve the most complex engineering challenges. We help them bring their ideas to light. We are a trusted partner, working alongside our customers to enable technology breakthroughs that change the world for the better.
This post was contributed by James Brown, compressed air and gas treatment/analytical gas sales manager and Filippo Turra, product manager, Parker Gas Separation and Filtration Division EMEA