Single turn solenoid is a transmit and receive RF imaging coil that, in general, has a cylindrical shape. The solenoidal configuration of this coil is a further developed planar surface coil. While surface coils have a strong coupling and high signal to noise ratio to nearby signals they have a marked loss of signal beyond one radius from the center of the coil. With a solenoidal coil design the imaging object lies within one radius from the coil center, which improved imaging (of extremities, such as wrist or knee).

See also Radio Frequency Coil and Imaging of the Extremities.

A surface coil is essentially a loop of conducting material, such as copper tubing. The in-bore solenoidal sending coil is used as the transmitter of RF energy. This type of receiver coil is placed directly on or over the region of interest for increased magnetic sensitivity. The loop may form various shapes and be bent slightly to conform to the imaged body part. Surface coils have a good SNR for tissues adjacent to the coil and because the signal decrease with the distance, an eligibility homogeneity correction will equalize this over the field of view. A rule of thumb for surface coils is that the sensitivity decreases appreciably beyond a distance equal to the diameter of the coil.
The positioning of the coil is an important determinant of performance. As only the region close to the surface coil will contribute to the signal, there is an improvement in the SNR for these regions, compared to the use of receiver coils that surround the appropriate part of the body. These coils are specifically designed for localized body regions, and provide improved signal to noise ratios by limiting the spatial extent of the excitation or reception.

See also the related poll result: '3rd party coils are better than the original manufacturer coils'

The process of adjusting the transmitter and receiver circuitry so that it provides optimal signal performance at the Larmor frequency. A properly tuned scanner will produce images with a higher signal to noise ratio, and therefore improved diagnostic versatility.
More generally, tuning is the process of adjusting the components for optimal performance, including matching impedances.

Imaging techniques in which NMR signals are gathered from the whole object volume to be imaged at once, with appropriate encoding pulse RF and gradient sequences to encode positions of the spins. Many sequential plane imaging techniques can be generalized to volume imaging, at least in principle. Advantages include potential improvement in signal to noise ratio by including signal from the whole volume at once; disadvantages include a bigger computational task for image reconstruction and longer image acquisition times (although the entire volume can be imaged from the one set of data). Also called simultaneous volume imaging.

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.