High Field MRI Technology


The Altaire high-field performance Open MR has an open design that combines a 0.7T super-conductive field strength magnet and advanced magnet technology for imaging capabilities consistent with high-field systems (see below for more detail). In a clinical practice, the quality of the images is extremely important to you and your patients. Altaire offers the ideal combination of image quality and patient comfort, producing tangible benefits for both physicians and patients.

j1Through a unique blend of innovative Hitachi features called VOSI (Vertical-Field with Optimized Sub-System Integration) technology, each sub-system’s performance is optimized. Altaire has an extremely fast and powerful gradient system with 22mT/m gradient amplitude and 55T/m/s slew rate (both of which are comparable to traditional high-field systems), enabling it to perform advanced clinical imaging techniques such as single-shot and multi-shot EPI; EPI based Diffusion-Weighted Imaging; MR Angiography, including CE-MRA; RF fat saturation and steady-state gradient echo sequences.

Hitachi’s advanced, actively decoupled linear quadrature and multiple array coils, designed for anatomically specific regions of interest, provide very high signal-to-noise even with the most demanding sequences.

MRI is used for all parts of the body and is effective in clinical evaluation of many conditions.

Technical Discussion

The Altaire system achieves high-field performance by optimizing each of the sub-systems responsible for determining image quality: Signal-to-Noise Ratio, Spatial Resolution and Contrast Resolution.

Signal-to-Noise Ratio is used to describe the ability to differentiate true “signal” from “noise.” The Altaire system maximizes four separate aspects of signal to noise ratio to achieve comparable image quality to a 1.5T high-field magnet.

Coil Geometry

Altaire’s vertical magnet architecture enables the use of solenoid coils as opposed to the less efficient saddle-type coils required in typical horizontal high-field systems. On average, solenoid coils are found to allow 40% more signal-to-noise to be recognized.

Receiver Bandwidth

Minimal bandwidth results in higher signal-to-noise ratio. There is an inherent advantage in lower field strengths in that they are able to operate at a lower receiver bandwidth than traditional high-field systems. The 0.7T field strength, the highly uniform magnetic field and the precision gradient controls allow the system to operate at a significantly lower bandwidth than traditional 1.5T high-field systems. The Altaire realizes a 20% signal-to-noise ratio advantage over traditional high-field systems.

Receiver Pre-Amplifier Noise Figure

As the first stage of signal reception after the receiver coil, the preamplifier needs to apply significant gain without adding noise. Altaire’s pre-amplifier’ 0.5 dB noise figure indicates Hitachi’s attention to this critical stage in the signal reception process. Traditional systems use 0.7 dB pre-amplifiers. Hitachi’s VOSI driven design approach resulted in a higher performance device resulting in a 20% improvement in signal-to-noise over traditional high-field systems.

Coil Fill Factor

Hitachi has provided a broad range of coil rather than general –purpose coils so as to insure as high a coil fill factor as possible. Anatomically specific and flexible type coild optimize fill factor while providing a linearly increasing impact on signal-to-noise ratio.


In summary, the Altaire vertical field permanent magnet technology provides signal-to-noise comparable to high-field strength systems by optimizing each sub-system’s performance.

j2Spatial Resolution is defined as the ability to discriminate between the smallest structures. All factors contribute to high spatial resolution, but the prime factor is the gradient sub-system.

The Altaire’s 22mT/m gradient strength and 55T/m/s slew rate are comparable with conventional high-field imaging systems and allows the system to deliver imaging quality and advanced imaging techniques only before seen on high-field, closed systems.

Contrast Resolution is defined as the ability to discriminate between different tissue types, even in a low signal environment. Contrast resolution is a key determinant of an imaging system’s clinical usefulness.

VOSI technology choices assure Altaire’s high sensitivity to small differences in tissue contrast under the most demanding scanning parameters. Prime factors in this sensitivity are the Altaire’s main magnetic field, its RF technology and sophisticated pulse sequence control.

Conclusion: Altaire offers an Open MR system that delivers:

  • Image quality comparable to high-field super-conductive systems,
  • Scan times comparable to high-field super-conductive systems, and
  • Clinical capabilities comparable to high-field super-conductive systems.

Further Reading