What causes MRI cold head failure? In this article, we reveal expert tips to keeping your MRI cold head running at peak efficiency.
The MRI coldhead is responsible for cooling the superconducting magnets that generate the magnetic fields necessary for MRI imaging. The superconducting magnets operate at extremely low temperatures, requiring a cryogenic cooling system to maintain their temperature. The coldhead is responsible for cooling the superconducting magnets and maintaining their operating temperature. If the coldhead fails, the magnets can heat up and damage the MRI machine, leading to costly repairs and downtime.
Preventing coldhead failure is essential for the optimal performance of an MRI machine. Regular maintenance, including inspections and checks for coolant leaks and mechanical wear, can help prevent issues before they lead to failure. Regular testing and monitoring of the superconducting magnets and coldhead can also help detect any potential issues before they become larger problems.
MRI Cold Head: How It Works
High-pressure helium gas from the Compressor Unit flows into the Cold Head via the helium supply connector (flex lines). Inside the cold head, helium passes through the displacer-regenerator assembly, where its expansion creates cooling for the first and second-stage cold stations. The gas then exits through the motor housing to the crankcase and returns to the Compressor Unit through the helium return connector.
Coldhead Failure Indications
Coldheads can fail for a variety of reasons, including age and wear and tear, coolant leaks, electrical faults, and mechanical failures. Age and wear and tear are significant factors in coldhead failure. Over time, the components of the coldhead can deteriorate, leading to reduced efficiency and eventual failure.
MRI machines are an essential component of medical facilities worldwide. They provide detailed imaging that enables healthcare professionals to accurately diagnose and treat a range of medical conditions. However, the performance and longevity of MRI machines depend on many factors, including the condition of their components, such as the coldhead. Learn more about the symptoms of a failing coldhead below.
1. Grinding or high-pitched noise
Abnormal sounds from the coldhead, such as grinding or high-pitched noises, often indicate mechanical or contamination issues, respectively. Both require service by a qualified MRI cryogen technician.
Worn or faulty internal coldhead components typically cause mechanical issues. Contamination issues arise from oil contamination in the coldhead, compressor, absorber, or coldhead lines, often due to impurities or oil in these lines.
While a grinding or high-pitched noise emanating from the coldhead by itself does not indicate immediate failure, it is advisable to schedule coldhead service in a timely manner to avoid any further damage to your system.
Replace absorber every 10,000 operating hours to help keep closed loop helium system free of contaminants.
2. Increased liquid helium boil-off rates
If you notice increased liquid helium loss, it may be due to a drop in coldhead efficiency. Other causes of liquid helium loss in MRI is high pressure, leak, or drop in cryostat efficiency.
3. Higher magnet pressure
Associated with increased liquid helium boil-off. *Ensure magnet heater assembly is functional and set to the correct pressure before troubleshooting cryostat system.
4. Separation of internal temperature readings
Checking the temperature difference between the first and second stages of the coldhead (if applicable) requires a Lakeshore meter or similar voltmeter and the expertise of an MRI cryogen specialist to evaluate magnet conditions. In some magnet models, coldhead temperatures are available via local or remote magnet monitor.
5. Nearing Mechanical End of Life
Mechanical failures, such as bearing wear, motor failure, or damage to the coldhead assembly, can cause MRI cold head failure. Regular inspections often identify these issues early and help prevent failure. The average coldhead lasts about 3 to 5 years, depending on the model.
6. Loose Coldhead bolts
In rare instances after a coldhead installation, some systems may experience a temporary drop in peak efficiency and may require tightening the coldhead bolts to spec. Schedule follow up visit, if needed.
7. Contaminated Coldhead lines
Oil and coolant leaks are another common cause of coldhead failure. A coolant leak can cause the coldhead to lose its cooling efficiency, leading to higher temperatures that can damage the MRI machine. Electrical faults can also contribute to MRI cold head failure. These can be caused by issues such as loose connections, damaged wiring, or electrical surges.
8. Low Pressure in Compressor and Coldhead lines
Ensure you compressor assembly is charged to the correct pressure on both high side and low side. Additionally, inspect the helium flex lines for leaks in main line or connectors if your compressor is not holding pressure. If no leak detected along flex lines, the compressor may need to be replaced.
My Coldhead Failed. Now What?
When coldhead failure occurs, it’s essential to address the issue quickly to prevent increased liquid helium loss or further damage to the machine. This may involve replacing the coldhead or making repairs to the existing unit. It’s important to work with an experienced technician who is familiar with MRI machines and coldhead replacement procedures for your specific MRI model to ensure that the repair is done correctly and safely.
How long does a MRI cold head replacement take?
The MRI coldhead replacement procedure typically requires 3 to 4 hours to complete. Although the replacement itself can be accomplished in 2 to 2.5 hours, allocating additional time to achieve a thorough vacuum down of the coldhead—ideally to below 10 microns—ensures optimal performance and reliability.
A follow-up visit may be required in the weeks following a coldhead replacement to:
- Tighten the coldhead bolts, if applicable.
- Ensure inner stage and outer stage temperatures are within specification.
If your MRI machine’s coldhead needs to be replaced or repaired, it’s essential to work with an experienced and reliable coldhead replacement service. The service should have a deep understanding of MRI machines and the components that contribute to their optimal performance. They should be able to provide prompt and reliable service, and be able to source high-quality replacement parts.
MRI Coldhead Price
The price of an MRI cold head typically ranges from $7,500 to $14,000, including installation and warranty. Magnet model, cold head type, and location determine the price variation.
Key Takeaways
In conclusion, MRI cold head failure is a common issue that can lead to downtime and costly repairs. Regular maintenance and inspections can help prevent coldhead failure, and quick action is necessary when issues do arise.
Working with an experienced MRI cryogen specialist is essential to ensure that any repairs or replacements are done safely and correctly. Contact a reputable coldhead replacement service to ensure the continued optimal performance of your MRI machine.
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