Tomography is imaging by sections or sectioning. A device used in tomography is called a tomograph, while the image produced is a tomogram. The mathematical basis for tomographic imaging was laid down by Johann Radon. It is applied in computed tomography and magnetic resonance tomography (MRT) also called magnetic resonance imaging (MRI) to obtain cross-sectional images of slices through the body of patients. Each of that slices is defined by thickness and spatial resolution (see voxel).

Inert hyperpolarized gases are under development for imaging air spaces, including those in the lungs. Because they mostly contain air and water, lungs are difficult organs to image.
These ventilation agents (gases) have potential in lung imaging and are currently used in studies of the pulmonary ventilation:
Specific isotopes of inert gases can be hyperpolarized. Hyperpolarized is a state in which almost all of the atoms nuclei are spinning in the same direction. Once the nuclei in the isotope 3He have been hyperpolarized using a laser, they remain in this state for several days. The inert, hyperpolarized gas can then be used in a lung imaging study, where the high concentration of polarized nuclei provides a sharp contrast in MRI. The technique is already being developed with a view to commercialization by Magnetic Imaging Technologies in Durham, North Carolina. According to the company, existing MRI equipment can be used with a few minor modifications, along with a gas polarizer. The technique could provide early detection and monitoring of pulmonary disease.
Hyperpolarized 129Xe can also be used as a magnetic resonance tracer because of its MR-enhanced sensitivity combined with its high solubility. This isotope differs from 3He in that it can dissolve in the blood. Strong enhancement of the nuclear spin polarization of xenon in the gas phase can be achieved by optical pumping of rubidium and subsequent spin-exchange with the xenon nuclei. This technique can increase the magnetic resonance signal of xenon by five orders of magnitude, thus allowing NMR detection of xenon in very low concentration. MR spectroscopy and imaging of optically polarized xenon shows considerable potential for medical applications (see also back projection imaging).
Nycomed Amersham anticipated the market for inert gases in pulmonary imaging. The company obtained an exclusive license for the use of helium (He) and xenon (Xe) as MRI contrast agents. Currently, the US FDA has not yet approved the commercial distribution of inert gas imaging equipment, because the technique is still undergoing trials.

The mobile intraoperative iMotion system produces real-time images used for MR guided surgery and offers functional magnetic resonance imaging, MR spectroscopy, perfusion imaging, and diffusion weighted imaging capabilities.
The iMotion 1.5 T magnet moves to the patient, gliding in and out of place as needed, without affecting surgical, anesthetic, and nursing management.

See also Intraoperative Magnetic Resonance Imaging, MR Guided Interventions.

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.

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GE Medical Systems and Amersham announced in April 2004 the completion of a share exchange acquisition of Amersham Health by GE. The result of this acquisition is the new GE Healthcare, based in the UK, totally owned by General Electric (GE).

Amersham plc, was a producer of contrast imaging agents used to enhance image quality in X-ray, magnetic resonance imaging, and ultrasound procedures. It was also a leading producer of radiopharmaceuticals used in nuclear medicine imaging. Amersham Health was the firm's imaging, diagnostics, and therapeutics segment. Amersham plc was involved in biotechnology research through its Amersham Biosciences unit, which made scanners, sequencers, microarrays, industrial separations, and other research supplies.