Open MRI Permanent Magnet Systems: How They Work, Costs and Buying Guide
Quick answer: An open MRI with a permanent magnet is a low-field MRI scanner (usually 0.2T to 0.4T) whose magnetic field comes from large blocks of permanent magnet material, typically neodymium-iron-boron (NdFeB), instead of a helium-cooled superconducting coil. The open C-arm or two-pillar design is comfortable for claustrophobic, larger and paediatric patients. It needs no liquid helium, no quench pipe and very little power, so running costs are low. The trade-off is lower image signal and longer scan times than 1.5T or 3T systems. A refurbished permanent-magnet open MRI typically costs from about £90,000 to £194,000 as a complete turnkey project, depending on field strength.
At Rising Medical Technologies we supply, relocate and install open MRI systems for hospitals and diagnostic centres in the UK, the Middle East and Africa. This guide explains how permanent-magnet open MRI works, where it fits clinically, what it costs and what to check before you buy, based on the questions our customers ask us most.
What is a permanent magnet open MRI?
Every MRI scanner needs a strong, stable and uniform main magnetic field (called B0). There are three ways to create it:
Superconducting magnets: coils of niobium-titanium wire cooled with liquid helium to around −269°C. Used for almost all 1.5T and 3T scanners.
Resistive (electromagnet) systems: copper coils powered continuously by electricity. Rare today.
Permanent magnets: blocks of rare-earth magnet material, usually neodymium-iron-boron (NdFeB), mounted on an iron yoke. The field is always on and needs no power or cryogens to maintain it.
Because permanent magnets are heavy and their field strength is limited in practice, most permanent-magnet MRI scanners are low-field systems between 0.2 and 0.4 tesla. The magnet blocks sit above and below the patient, which naturally creates an open design with wide side access instead of a closed tunnel.
How a permanent magnet MRI works
The imaging principle is the same as any MRI. The main field aligns hydrogen protons in the body, radiofrequency (RF) pulses tip them, and receive coils pick up the signal as they relax. Gradient coils encode position so the computer can build cross-sectional images.
What changes is how the main field is made and kept stable:
Magnet poles and yoke: two pole pieces face each other across the patient gap, joined by a steel yoke in a C-shape or with two or four pillars. The yoke returns the magnetic flux, which also keeps the stray (fringe) field small.
Temperature control: NdFeB magnets lose a small amount of strength as they warm up. The magnet is therefore held at a constant temperature by built-in heaters, and the scan room must be kept within the manufacturer's temperature limits. Stable temperature means a stable field and consistent images.
Shimming: small iron or magnet pieces and shim settings correct the field uniformity across the imaging volume after installation.
Advantages of permanent magnet open MRI
1. Patient comfort and access
The open gantry suits patients who cannot tolerate a closed bore: claustrophobic and anxious patients, children (often with a parent beside them), larger patients and people with limited mobility. Fewer cancelled or sedated scans means better use of the scanner.
2. No liquid helium
Superconducting magnets need liquid helium, which is expensive and subject to supply shortages, and they need periodic helium refills and a cold head that runs continuously. A permanent magnet needs none of this. There is no risk of a magnet quench and no quench pipe to install.
3. Low running and power costs
The main field costs nothing to maintain. Electricity is mainly used by the gradients, RF system, computers, magnet temperature control and air conditioning, so power demand is far lower than a high-field system with its helium compressor and chiller. This matters a lot where electricity is expensive or the supply is unreliable.
4. Small fringe field
The iron yoke contains most of the magnetic field, so the 0.5 mT (5 gauss) safety line usually stays close to the magnet. This makes it easier to fit the scanner into an existing building, often without extra magnetic shielding.
5. Lower purchase and installation cost
A refurbished low-field permanent system, with RF shielding and installation, costs a fraction of a new 1.5T project. That makes MRI viable for smaller hospitals, private clinics and new imaging centres.
Limitations to understand
Lower signal-to-noise ratio (SNR): signal increases with field strength, so low-field images have less signal. Scans take longer to reach good quality and fine detail is more limited.
Fewer advanced applications: cardiac MRI, spectroscopy, functional MRI, advanced diffusion and high-resolution small-part imaging are better done at 1.5T or 3T.
Weight: whole-body permanent magnets are very heavy, often in the region of 10 to 20 tonnes depending on the model. Floor loading and the delivery route must be checked by a structural engineer.
Always on: the field cannot be switched off, even in an emergency. Strict MRI safety zoning and screening still apply.
Temperature sensitivity: the room air conditioning and magnet temperature control must run continuously. A long power or cooling failure can let the magnet drift and require time to stabilise.
Clinical applications
A well-maintained 0.3T to 0.4T open MRI handles most routine outpatient work:
Musculoskeletal: knee, shoulder, hip, ankle, wrist and elbow, including joint injuries and sports medicine.
Spine: cervical, thoracic and lumbar spine for disc disease, nerve compression and back pain.
Neuro: routine brain imaging, stroke follow-up, sinuses and internal auditory meatus (IAM) protocols.
Body and pelvis: routine abdomen and pelvis studies, depending on the system and coils.
Some open systems also allow interventional or positional work because of the free space around the patient.
Field strength comparison: 0.3T vs 0.35T vs 0.4T
0.3T permanent: entry-level MSK, spine and routine brain imaging. Typical refurbished turnkey cost*: £90,000 – £97,000.
0.35T: routine neuro, spine and MSK with improved image quality. Typical refurbished turnkey cost*: £142,000 – £164,000.
0.4T: faster scans and sharper routine clinical imaging. Typical refurbished turnkey cost*: £179,000 – £194,000.
*Turnkey means the refurbished system plus site survey, RF cage design, packing, shipping, installation, commissioning and applications training. Import duties and local taxes are not included. Use our CT & MRI price calculator for a quick estimate.
Permanent magnet vs superconducting MRI
Field strength: permanent open MRI is usually 0.2T – 0.4T; superconducting MRI is 1.5T or 3T.
Liquid helium: not needed for permanent magnets; superconducting magnets need it, with refills.
Quench pipe: not needed for permanent magnets; required for superconducting systems.
Power use: low for permanent magnets; high for superconducting systems, whose compressor and chiller run 24/7.
Patient experience: open with wide access, compared with an enclosed bore.
Image quality and speed: good for routine work but slower at low field; higher detail, faster scans and advanced applications at high field.
Project cost: lower for permanent open MRI; significantly higher for superconducting MRI.
For a deeper look at the wider buying decision, read our guide to refurbished vs new MRI scanners.
Well-known permanent magnet open MRI systems
Several major manufacturers have produced permanent-magnet open MRI scanners that are widely available on the refurbished market, including the Hitachi AIRIS and APERTO families (now part of Fujifilm Healthcare), the Siemens MAGNETOM C! (0.35T) and the dedicated extremity and positional scanners from Esaote. Availability of service, spare parts and software support for the exact model in your country should be part of your choice.
Site and installation requirements
RF shielding (Faraday cage): still required to keep outside radio signals out of the images.
Floor loading: confirmed by a structural engineer, with steel spreader plates or a reinforced slab if needed.
Air conditioning: stable temperature and humidity in the scan room and equipment room, with backup cooling where possible.
Power: a clean, stable supply with a voltage stabiliser and UPS for the computers. A generator is strongly recommended where mains power is unreliable.
Access route: door widths, corridors and lifting equipment checked for the magnet's size and weight.
MRI safety zoning: controlled access, signage and screening, because the field is always on.
Relocation and handling: why engineer supervision matters
A permanent magnet stays magnetised during transport, so it needs specialist handling: correct lifting points, secure crating and clear labelling to keep ferromagnetic objects away. From our own projects, the biggest avoidable risk is rough handling by general cargo crews during unloading from the container and storage. We keep every move under the supervision of our own engineers, from de-installation to final positioning, so the magnet, gantry and electronics arrive undamaged. You can request a shipping quote for any MRI relocation.
Buying checklist for a refurbished open MRI
Field strength, model, year of manufacture and software version
Coils included (knee, shoulder, spine, head, body, flex)
Image quality test results and phantom images
Service history and the availability of parts and engineers in your country
Who handles de-installation, transport, RF cage, installation and training
Warranty and service contract terms after handover
Frequently asked questions
Is a permanent magnet MRI always on?
Yes. A permanent magnet cannot be switched off, so the magnetic field is present 24 hours a day. MRI safety screening and access control apply at all times.
Does a permanent magnet open MRI need helium?
No. Permanent-magnet systems need no liquid helium, no cold head and no quench pipe, which is one of their main cost advantages.
How strong is a permanent magnet MRI?
Most are between 0.2T and 0.4T. That is lower than 1.5T or 3T superconducting scanners but sufficient for most routine musculoskeletal, spine and brain imaging.
Is open MRI image quality good enough for diagnosis?
For routine clinical questions, yes, when the system is well maintained and protocols are set up properly. For advanced applications such as cardiac MRI or very fine detail, a high-field system is the better choice.
How much does a permanent magnet open MRI cost?
A refurbished 0.35T open MRI system starts from around £80,000 for the scanner alone. As a complete turnkey project, typical ranges are £90,000–£97,000 for 0.3T, £142,000–£164,000 for 0.35T and £179,000–£194,000 for 0.4T.
How much power does a permanent magnet MRI use?
Much less than a superconducting system, because no power is needed to maintain the main field and there is no helium compressor. Power is used mainly by the gradients, RF electronics, computers, magnet heaters and air conditioning.
Can a permanent magnet MRI be relocated?
Yes. Permanent systems are regularly relocated between sites and countries. It requires specialist rigging, secure crating and engineer supervision, followed by re-installation, shimming and calibration at the new site.
Who is open MRI best for?
Claustrophobic and anxious patients, children, larger patients, elderly or less mobile patients, and clinics that mainly perform musculoskeletal and spine imaging.
Planning an open MRI project?
Rising Medical Technologies supplies refurbished open and high-field MRI systems with site survey, RF shielding, shipping, installation, training and after-sales support. Browse our MRI scanners, try the price calculator, or contact us on WhatsApp, phone or email for a quotation.
