Duty cycle is the time during which the gradient system can be run at maximum power. The duty cycle is based on the total time and includes the cool down phase. The duty cycle on the RF pulse during MRI is restricted based on the specific absorption rate (SAR) limit.
SAR limits restrict radio frequency heating effects. The specific absorption rate increases with field strength, radio frequency power and duty cycle, type of the transmitter coil and body size. The especially in high and ultrahigh magnetic fields, important SAR issue can be readily addressed by reducing the RF duty cycle due to longer repetition times (TR) and the use of parallel imaging techniques. A TR longer than the minimum needed provides time for the tissue to cool down, but for the cost of a longer scan time. A parallel imaging technique reduces the RF exposure and the scan time.

See also High Field MRI.

From ISOL Technology

'MRI system is not an expensive equipment anymore. ENCORE developed by ISOL Technology is a low cost MRI system with the advantages like of the 1.0T MRI scanner. Developed specially for the overseas market, the ENCORE is gaining popularity in the domestic market by medium sized hospitals.
Due to the optimum RF and Gradient application technology. ENCORE enables to obtain high resolution imaging and 2D/3D Angio images which was only possible in high field MR systems.'
- Less consumption of the helium gas due to the ultra-lightweight magnet specially designed and manufactured for ISOL. - Cost efficiency MR system due to air cooling type (equivalent to permanent magnetic). - Patient processing speed of less than 20 minutes.'

A type of magnet that utilizes coils of wire, typically wound on an iron core, so that as current flows through the coil it becomes magnetized. The direction of the magnetic field is parallel to the long axis of the coil. Whole body electromagnets, used in medical imaging (also called resistive) are limited to their field strength, because the weight becomes prohibitively large at high field MRI. The magnetic field shuts down, if the current is switched of. Because this type of magnet generates heat, a good cooling system is essential.
For a stronger magnetic field, the wires must be manufactured of superconducting materials to reduce the power needed to produce the field.

See also Resistive Magnet, Superconducting Magnet and Upright™ MRI

Knee and shoulder MRI exams are the most commonly requested musculoskeletal MRI scans. Other MR imaging of the extremities includes hips, ankles, elbows, and wrists. Orthopedic imaging requires very high spatial resolution for reliable small structure definition and therefore places extremely high demands on SNR.
Exact presentation of joint pathology expects robust and reliable fat suppression, often under difficult conditions like off-center FOV, imaging at the edge of the field homogeneity or in regions with complex magnetic susceptibility.
MR examinations can evaluate meniscal dislocations, muscle fiber tears, tendon disruptions, tendinitis, and diagnose bone tumors and soft tissue masses. MR can also demonstrate acute fractures that are radiographically impossible to see. Evaluation of articular cartilage for traumatic injury or assessment of degenerative disease represents an imaging challenge, which can be overcome by high field MRI applications. Currently, fat-suppressed 3D spoiled gradient echo sequences and density weighted fast spin echo sequences are the gold-standard techniques used to assess articular cartilage.
Open MRI procedures allow the kinematic imaging of joints, which provides added value to any musculoskeletal MRI practice. This technique demonstrates the actual functional impingements or positional subluxations of joints. In knee MRI examinations, the kinematical patellar study can show patellofemoral joint abnormalities.

See also Open MRI, Knee MRI, Low Field MRI.

From Philips Medical Systems;
the Intera 3 T high field system, the first with a compact magnet, which is built on the same platform as the 1.5 T, is targeted to high-end neurological, orthopedic and cardiovascular imaging applications with maximum patient comfort and acceptance without compromising image quality and clinical performance. Useable for clinical routine and research. The Intera systems offer diffusion tensor imaging (DTI) fiber tracking that measures movement of water in the brain and can therefore detect areas of the brain where normal movement of water is disrupted.