There are different types of contraindications that would prevent a person from being examined with an MRI scanner. MRI systems use strong magnetic fields that attract any ferromagnetic objects with enormous force. Caused by the potential risk of heating, produced from the radio frequency pulses during the MRI procedure, metallic objects like wires, foreign bodies and other implants needs to be checked for compatibility. High field MRI requires particular safety precautions. In addition, any device or MRI equipment that enters the magnet room has to be MR compatible. MRI examinations are safe and harmless, if these MRI risks are observed and regulations are followed.

Safety concerns in magnetic resonance imaging include:

It is important to remember when working around a superconducting magnet that the magnetic field is always on. Under usual working conditions the field is never turned off. Attention must be paid to keep all ferromagnetic items at an adequate distance from the magnet. Ferromagnetic objects which came accidentally under the influence of these strong magnets can injure or kill individuals in or nearby the magnet, or can seriously damage every hardware, the magnet itself, the cooling system, etc.. See MRI resources Accidents.
The doors leading to a magnet room should be closed at all times except when entering or exiting the room. Every person working in or entering the magnet room or adjacent rooms with a magnetic field has to be instructed about the dangers. This should include the patient, intensive-care staff, and maintenance-, service- and cleaning personnel, etc..
The 5 Gauss limit defines the 'safe' level of static magnetic field exposure. The value of the absorbed dose is fixed by the authorities to avoid heating of the patient's tissue and is defined by the specific absorption rate. Leads or wires that are used in the magnet bore during imaging procedures, should not form large-radius wire loops. Leg-to-leg and leg-to-arm skin contact should be prevented in order to avoid the risk of burning due to the generation of high current loops if the legs or arms are allowed to touch. The patient's skin should not be in contact with the inner bore of the magnet.
The outflow from cryogens like liquid helium is improbable during normal operation and not a real danger for patients.
The safety of MRI contrast agents is tested in drug trials and they have a high compatibility with very few side effects. The variations of the side effects and possible contraindications are similar to X-ray contrast medium, but very rare. In general, an adverse reaction increases with the quantity of the MRI contrast medium and also with the osmolarity of the compound.

See also 5 Gauss Fringe Field, 5 Gauss Line, Cardiac Risks, Cardiac Stent, dB/dt, Legal Requirements, Low Field MRI, Magnetohydrodynamic Effect, MR Compatibility, MR Guided Interventions, Claustrophobia, MRI Risks and Shielding.

O-scan is manufactured and distributed by Esaote SpA
O-scan is a compact, dedicated extremity MRI system designed for easy installation and high throughput. The complete system fits in a 9' x 10' room, doesn't need for RF or magnetic shielding and it plugs in the wall. The 0.31T permanent magnet along with dual phased array RF coils, and advanced imaging protocols provide outstanding image quality and fast 25 minute complete examinations.
Esaote North America is the exclusive distributor of the O-scan system in the USA.

From FONAR Corporation;
in October of 2004, the company changed the product name of the Stand-Upâ„¢ MRI to the Uprightâ„¢ MRI. The Indomitableâ„¢, Uprightâ„¢ MRI is the only open MRI in the world that can perform positional MRI (pMRI), i.e. the Upright MRIâ„¢ scans patients in upright, weight-bearing positions, in addition to the conventional lie-down positions. The Uprightâ„¢ MRI is the only device that can scan patients in the position their symptoms occur, in their position of pain. In early clinical reports independently confirm the effectiveness and potential of positional MRI. In October 2000, Fonar received permission to market the Indomitableâ„¢ from the FDA.

From Siemens Medical Systems; Received FDA clearance in 2013.
The MAGNETOM Prisma is the 3T PowerPack for exploration that offers most demanding clinical and research challenges of today and the future. The latest parallel transmit technology, TimTX TrueShape, enables zooming into specific body regions for enhanced image quality. Furthermore, the Tim 4G integrated coil technology offers remarkable imaging flexibility and supports complex examinations across the whole body.
Onsite upgrades to the MAGNETOM Prisma for customers who have already installed the 3 Tesla MAGNETOM Trio are possible.

From Toshiba America Medical Systems Inc.;
the EXCELART is a superconducting whole body MRI system with a short wide-bore magnet, operating at 1.5 T. It features powerful high-speed gradients with a revolutionary gradient acoustic noise reduction system: Pianissimo. The dramatic reduction of gradient acoustic noise by Pianissimo greatly enhances patient comfort during exams. The standard array platform and a wide range of array coils ensure excellent images. A powerful 64-bit RISC-based computer system and newly developed array processor realize high productivity.