The MRI device is located within a specially shielded room (Faraday cage) to avoid outside interference, caused by the use of radio waves very close in frequency to those of ordinary FM radio stations.
The MRI procedure can easily be performed through clothing and bones, but attention must be paid to ferromagnetic items, because they will be attracted from the magnetic field. A hospital gown is appropriate, or the patient should wear clothing without metal fasteners and remove any metallic objects like hairpins, jewelry, eyeglasses, clocks, hearing aids, any removable dental work, lighters, coins etc., not only for MRI safety reasons. Metal in or around the scanned area can also cause errors in the reconstructed images (artifacts). Because the strong magnetic field can displace, or disrupt metallic objects, people with an implanted active device like a cardiac pacemaker cannot be scanned under normal circumstances and should not enter the MRI area.
The MRI machine can look like a short tunnel or has an open MRI design and the magnet does not completely surround the patient. Usually the patient lies on a comfortable motorized table, which slides into the scanner, depending on the MRI device, patients may be also able to sit up. If a contrast agent is to be administered, intravenous access will be placed. A technologist will operate the MRI machine and observe the patient during the examination from an adjacent room. Several sets of images are usually required, each taking some minutes. A typical MRI scan includes three to nine imaging sequences and may take up to one hour. Improved MRI devices with powerful magnets, newer software, and advanced sequences may complete the process in less time and better image quality.
Before and after the most MRI procedures no special preparation, diet, reduced activity, and extra medication is necessary. The magnetic field and radio waves are not felt and no pain is to expect.
Movement can blur MRI images and cause certain artifacts. A possible problem is the claustrophobia that some patients experience from being inside a tunnel-like scanner. If someone is very anxious or has difficulty to lie still, a sedative agent may be given. Earplugs and/or headphones are usually given to the patient to reduce the loud acoustic noise, which the machine produces during normal operation. A technologist observes the patient during the test. Some MRI scanners are equipped with televisions and music to help the examination time pass.
MRI is not a cheap examination, however cost effective by eliminating the need for invasive radiographic procedures, biopsies, and exploratory surgery. MRI scans can also save money while minimizing patient risk and discomfort. For example, MRI can reduce the need for X-ray angiography and myelography, and can eliminate unnecessary diagnostic procedures that miss occult disease.

See also Magnetic Resonance Imaging MRI, Medical Imaging, Cervical Spine MRI, Claustrophobia, MRI Risks and Pregnancy.
For Ultrasound Imaging (USI) see Ultrasound Imaging Procedures at Medical-Ultrasound-Imaging.com.

See also the related poll result: 'MRI will have replaced 50% of x-ray exams by'

(MRA) Magnetic resonance angiography is a medical imaging technique to visualize blood filled structures, including arteries, veins and the heart chambers. This MRI technique creates soft tissue contrast between blood vessels and surrounding tissues primarily created by flow, rather than displaying the vessel lumen. There are bright blood and black blood MRA techniques, named according to the appearance of the blood vessels. With this different MRA techniques both, the blood flow and the condition of the blood vessel walls can be seen. Flow effects in MRI can produce a range of artifacts. MRA takes advantage of these artifacts to create predictable image contrast due to the nature of flow.
Technical parameters of the MRA sequence greatly affect the sensitivity of the images to flow with different velocities or directions, turbulent flow and vessel size.
This are the three main types of MRA:
All angiographic techniques differentially enhance vascular MR signal. The names of the bright blood techniques TOF and PCA reflect the physical properties of flowing blood that were exploited to make the vessels appear bright. Contrast enhanced magnetic resonance angiography creates the angiographic effect by using an intravenously administered MR contrast agent to selectively shorten the T1 of blood and thereby cause the vessels to appear bright on T1 weighted images.
MRA images optimally display areas of constant blood flow-velocity, but there are many situations where the flow within a voxel has non-uniform speed or direction. In a diseased vessel these patterns are even more complex. Similar loss of streamline flow occurs at all vessel junctions and stenoses, and in regions of mural thrombosis. It results in a loss of signal, due to the loss of phase coherence between spins in the voxel.
This signal loss, usually only noticeable distal to a stenosis, used to be an obvious characteristic of MRA images. It is minimized by using small voxels and the shortest possible TE. Signal loss from disorganized flow is most noticeable in TOF imaging but also affects the PCA images.
Indications to perform a magnetic resonance angiography (MRA):
Conventional angiography or computerized tomography angiography (CT angiography) may be needed after MRA if a problem (such as an aneurysm) is present or if surgery is being considered.

See also Magnetic Resonance Imaging MRI.

(MRI) Magnetic resonance imaging is a noninvasive medical imaging technique that uses the interaction between radio frequency pulses, a strong magnetic field and body tissue to obtain images of slices/planes from inside the body. These magnets generate fields from approx. 2000 times up to 30000 times stronger than that of the Earth. The use of nuclear magnetic resonance principles produces extremely detailed pictures of the body tissue without the need for x-ray exposure and gives diagnostic information of various organs.
Measured are mobile hydrogen nuclei (protons are the hydrogen atoms of water, the 'H' in H20), the majority of elements in the body. Only a small part of them contribute to the measured signal, caused by their different alignment in the magnetic field. Protons are capable of absorbing energy if exposed to short radio wave pulses (electromagnetic energy) at their resonance frequency. After the absorption of this energy, the nuclei release this energy so that they return to their initial state of equilibrium.
This transmission of energy by the nuclei as they return to their initial state is what is observed as the MRI signal. The subtle differing characteristic of that signal from different tissues combined with complex mathematical formulas analyzed on modern computers is what enables MRI imaging to distinguish between various organs. Any imaging plane, or slice, can be projected, and then stored or printed.
The measured signal intensity depends jointly on the spin density and the relaxation times (T1 time and T2 time), with their relative importance depending on the particular imaging technique and choice of interpulse times. Any motion such as blood flow, respiration, etc. also affects the image brightness.
Magnetic resonance imaging is particularly sensitive in assessing anatomical structures, organs and soft tissues for the detection and diagnosis of a broad range of pathological conditions. MRI pictures can provide contrast between benign and pathological tissues and may be used to stage cancers as well as to evaluate the response to treatment of malignancies. The need for biopsy or exploratory surgery can be eliminated in some cases, and can result in earlier diagnosis of many diseases.

See also MRI History and Functional Magnetic Resonance Imaging (fMRI).

(PACS) A system used to communicate and archive medical imaging data, mostly images and associated textural data generated in a radiology department, and disseminated throughout the hospital. A PACS is usually based on the DICOM (Digital Imaging and Communications in Medicine) standard.
The main components in the PACS are:
Acquisition devices, which acquire their data in direct digital format, like a MRI system, are most easily integrated into a PACS.
Short term archives need to have rapid access, such as provided by a RAID (redundant array of independent disks), whereas long term archives need not have such rapid access and can be consigned, e.g. to optical disks or a magnetic.
High speed networks are necessary for rapid transmission of imaging data from the short term archive to the diagnostic workstations. Optical fiber, ATM (asynchronous transfer mode), fast or switched Ethernet, are examples of high speed transmission networks, whereas demographic textural data may be transmitted along conventional Ethernet.
Sophisticated software is a major element in any hospital-wide PACS. The software concepts include: preloading or prefetching of historical images pertinent to current examinations, worklists and folders to subdivide the vast mass of data acquired in a PACS in a form, which is easy and practical to access, default display protocols whereby images are automatically displayed on workstation monitors in a prearranged clinically logical order and format, and protocols radiologists can rapidly report worklists of undictated examinations, using a minimum of computer manipulation.

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Toshiba Medical Systems started 1914 and was a leading diagnostic imaging manufacturer with departments including research, development, production, service and support of medical imaging equipment and systems. 1976 Toshiba America Medical Systems, Inc. (TAMS) was founded to coordinate sales and service for previously established business operations in the USA.

In March 2016 Toshiba sold its Toshiba Medical Systems for $6 billion to Japan's Canon. After regulatory approval the company got renamed to Canon Medical Systems.

MRI Scanners:

0.2T to 1.0T:
1.5T:
3.0T: