[H₀] Conventional symbol historically used for the constant magnetic field in an MR system; it is physically more correct to use B0.

[B₀] A conventional symbol for the main magnetic field strength (magnetic flux density or induction) in a MRI system. Although historically used, H0 (units of magnetic field strength, ampere//meter) should be distinguished from the more appropriate B0 [units of magnetic induction, tesla].
In current MR systems it has a constant value over time varying from 0.02 to 4 T. Field strengths of 0.5 T and above are generated with superconductive magnets. High field strengths have a better signal to noise ratio (SNR). The optimal imaging field strength for clinical imaging is between 0.5 and 2.0 T.

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

From Siemens Medical Systems;
This open MRI system is a dedicated extremity scanner, which is easy to use and easy to install. Whether you want to use it as a supplement to your whole-body scanner or you want to specialize in orthopedic exams, MAGNETOM Jazz™ offers you a cost effective opportunity to make the most of your capabilities.

From Hitachi Medical Systems America, Inc.;
because of its dependability, the MRP-7000™ remains popular more than a decade after the first U.S. system was shipped. This system maintains a high resale value, what has made it one of the most sought-after scanners on the used MRI equipment market.

From MagneVu;
The MagneVu 1000 is a compact, robust, and portable, permanent magnet MRI system and operates without special shielding or costly site preparation.
This MRI device utilizes a patented non-homogeneous magnetic field image acquisition method to achieve high performance imaging. The MagneVu 1000 MRI scanner is designed for MRI of the extremities with the current specialty areas in diabetes and rheumatoid arthritis. Easy access is afforded for claustrophobic, pediatric, or limited mobility patients.
In August 1998 FDA marketing clearance and other regulatory approvals have been received.
Until 2008, over 130 devices in the US are in use. Some further developments of MagneVu's extremity scanner are: 'truly Plug n' Play MRI™' and iSiS ( which adds wireless capability to the second generation MV1000-XL).