The subacute risks and side effects of magnetic and RF fields (for patients and staff) have been intensively examined for a long time, but there have been no long-term studies following persons who have been exposed to the static magnetic fields used in MRI. However, no permanent hazardous effects of a static magnetic field exposure upon human beings have yet been demonstrated.
Temporary possible side effects of high magnetic and RF fields:
The results of some animal and cellular studies suggest the possibility that electromagnetic fields may act as co-carcinogens or tumor promoters, but the data are inconclusive. Up to 45 tesla, no important effects on enzyme systems have been observed. Neither changes in enzyme kinetics, nor orientation changes in macromolecules have been conclusively demonstrated.
There are some publications associating an increase in the incidence of leukemia with the location of buildings close to high-current power lines with extremely low-frequency (ELF) electromagnetic radiation of 50-60 Hz, and industrial exposure to electric and magnetic fields but a transposition of such effects to MRI or MRS seems unlikely.
Under consideration of the MRI safety guidelines, real dangers or risks of an exposure with common MRI field strengths up to 3 tesla as well as the RF exposure during the MRI scan, are not to be expected.

For more MRI safety information see also Nerve Conductivity, Contraindications, Pregnancy and Specific Absorption Rate.

See also the related poll result: 'In 2010 your scanner will probably work with a field strength of'

Rapid echo planar imaging and high-performance MRI gradient systems create fast-switching magnetic fields that can stimulate muscle and nerve tissues produced by either changing the electrical resistance or the potential of the excitation. There are apparently no effects on the conduction of impulses in the nerve fiber up to field strength of 0.1 T. A preliminary study has indicated neurological effects by exposition to a whole body imager at 4.0 T. Theoretical examinations argue that field strengths of 24 T are required to produce a 10% reduction of nerve impulse conduction velocity.
Nerve stimulations during MRI scans can be induced by very rapid changes of the magnetic field. This stimulation may occur for example during diffusion weighted sequences or diffusion tensor imaging and can result in muscle contractions caused by effecting motor nerves. The so-called magnetic phosphenes are attributed to magnetic field variations and may occur in a threshold field change of between 2 and 5 T/s. Phosphenes are stimulations of the optic nerve or the retina, producing a flashing light sensation in the eyes. They seem not to cause any damage in the eye or the nerve.
Varying magnetic fields are also used to stimulate bone-healing in non-unions and pseudarthroses. The reasons why pulsed magnetic fields support bone-healing are not completely understood. The mean threshold levels for various stimulations are 3600 T/s for the heart, 900 T/s for the respiratory system, and 60 T/s for the peripheral nerves.
Guidelines in the United States limit switching rates at a factor of three below the mean threshold for peripheral nerve stimulation. In the event that changes in nerve conductivity happens, the MRI scan parameters should be adjusted to reduce dB/dt for nerve stimulation.

Manufactured by Esaote S.p.A.;
a low field open MRI scanner with permanent magnet for orthopedic use. The outstanding feature of this MRI system is a patient friendly design with 24 cm diameter, which allows the imaging of extremities and small body parts like shoulder MRI. The power consumption is around 1.3 kW and the needed minimum floor space is an area of 16 sq m.
At RSNA 2006 Hologic Inc. introduced a new dedicated extremity MRI scanner, the Opera. Manufactured by Esaote is the Opera a redesign of Esaote's 0.2 Tesla E-Scan XQ platform, which now enables complete imaging of all extremities, including hip and shoulder applications. 'Real-time positioning' reportedly speeds patient setup and reduces exam times.
Esaote North America and Hologic Inc are the U.S. distributors of this MRI device.

Silicon Graphics workstations are used in products from many other industry-leading medical manufacturers including:
The CT and MR products from General Electric Medical Systems uses Silicon Graphics® O2 and OCTANE workstation.
From Siemens Medical Systems, Inc., the postprocessing CT and MR workstations use Silicon Graphics O2 workstations.
Toshiba America MRI Inc. uses Silicon Graphics O2 workstations in its MRI scanners.
Bruker uses Silicon Graphics O2 workstations in its MRI scanners.

Any abnormal reaction of a patient to an examination or procedure, like for example claustrophobia or side effects of MRI contrast agents.
A claustrophobic attack is MRI scanner dependent and more rare with an open MRI. An adverse reaction with magnetic resonance imaging contrast medium is very infrequent. In general, adverse reactions increase with the quantity of contrast media (usual dose of paramagnetic contrast agents is 0.1 mmol/kg) and also with the osmolarity of the compound.
Most frequently encountered adverse reactions are heat sensation, dizziness, nausea, hypotension due to vasodilatation, which can progress to hypotensive shock and anaphylactic reactions.
See also MRI Safety, Contrast Enhanced MRI, Breast MRI, and Cardiac MR imaging.