From GE Healthcare;
The Signa HDx MRI system is GE's leading edge whole body magnetic resonance scanner designed to support high resolution, high signal to noise ratio, and short scan times.
Signa HDx 3.0T offers new technologies like ultra-fast image reconstruction through the new XVRE recon engine, advancements in parallel imaging algorithms and the broadest range of premium applications. The HD applications, PROPELLER (high-quality brain imaging extremely resistant to motion artifacts), TRICKS (contrast-enhanced angiographic vascular lower leg imaging), VIBRANT (for breast MRI), LAVA (high resolution liver imaging with shorter breath holds and better organ coverage) and MR Echo (high-definition cardiac images in real time) offer unique capabilities.

(SNR or S/N) The signal to noise ratio is used in MRI to describe the relative contributions to a detected signal of the true signal and random superimposed signals ('background noise') - a criterion for image quality.
One common method to increase the SNR is to average several measurements of the signal, on the expectation that random contributions will tend to cancel out. The SNR can also be improved by sampling larger volumes (increasing the field of view and slice thickness with a corresponding loss of spatial resolution) or, within limits, by increasing the strength of the magnetic field used. Surface coils can also be used to improve local signal intensity. The SNR will depend, in part, on the electrical properties of the sample or patient being studied. The SNR increases in proportion to voxel volume (1/resolution), the square root of the number of acquisitions (NEX), and the square root of the number of scans (phase encodings). SNR decreases with the field of view squared (FOV2) and wider bandwidths. See also Signal Intensity and Spin Density.

Measuring SNR:
Record the mean value of a small ROI placed in the most homogeneous area of tissue with high signal intensity (e.g. white matter in thalamus). Calculate the standard deviation for the largest possible ROI placed outside the object in the image background (avoid ghosting/aliasing or eye movement artifact regions).
The SNR is then:
Mean Signal/Standard Deviation of Background Noise

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).

Volumetric imaging is a 3D technique where all the MRI signals are collected from the entire tissue sample and imaged as a whole entity, therefore providing a high signal to noise ratio. The acquisition of isotropic voxels or thin slices with high spatial resolution allows to create multiplanar reconstructions in all planes; a compensation for the usually longer scan time. The acquisition time can be reduced by parallel imaging technique.
New T2 weighted variants of 3D sequences (FSE-XETA, T2-SPACE, VISTA) have been introduced that differ from conventional FSE sequences. An echo train containing up to 200 echoes obtained at a minimum echo spacing allows very fast acquisition. A flip angle modulation (flip angle sweep - FAS) during the FSE readout carries magnetization as long as possible to avoid blurring and provide optimal signal at the effective echo time. This type of imaging is well suited for brain and spine MRI procedures.
Newer T1 weighted variants include Liver Acquisition with Volume Acquisition (LAVA) and T1W High Resolution Isotropic Volume Examination (THRIVE), which have advantages for dynamic breath hold imaging in liver and abdominal examinations.

See also Volume Imaging, 3 Dimensional Imaging.