Arbitrary Shape Selective Excitation Summed Spectroscopy (ASSESS)

Summary

Vanderbilt researchers have developed a novel single-voxel localization technique for Magnetic Resonance Spectroscopy (MRS), termed ASSESS ("Arbitrary Shape Selective Excitation Summed Spectroscopy"). ASSESS can measure spectra from regions of arbitrary shape allowing the user to customize the region of interest.

MRS differs from Magnetic Resonance Imaging (MRI) in that it allows biochemical information to be obtained non-invasively from specific tissues of interest, whereas MRI only gives information about the structure. An example would be when a physician uses MRI to examine the brain and locate the exact region where the tumor is located. Once located, the physician can highlight an area within the tumor and obtain a spectrum of known metabolites, such as choline, creatine and lactate. These metabolites levels, as well as others, can aid in the diagnosis, such as the aggressiveness and stage of a tumor.

MRS can provide extensive information; however, it is critical that only the specific region of interest be examined since metabolites can vary greatly between various tissues. Unfortunately, when the volume is restricted, the signal-to-noise ratio is affected. Quantifiable MRS data requires maximum signal-to-noise ratio per unit of time while minimizing partial volume effects. Thus, in order to obtain accurate, quantifiable MRS data, not only is an adequate signal-to-noise ratio crucial, but limiting analysis to only the tissue of interest becomes crucial, as well, in order to produce accurate spectra. Vanderbilt researchers have developed a novel approach to maximize signal-to-noise ratio per unit of time while minimizing partial volume effects. Essentially this technology allows the end user to customize the region of interest such that data can be obtained from arbitrary shapes other than standard rectangles. By eliminating unwanted tissue, which is often included in standard rectangular regions of interest, the data obtained more accurately represents the actual region of interest.

This technology, dubbed 2D "Arbitrary Shape Selective Excitation Summed Spectroscopy" (ASSESS), through simple and straightforward Magnetic Resonance sequence design, theoretically can be implemented on any Magnetic Resonance scanner. It has been demonstrated, by both imaging and spectroscopy of rat brain regions of interests in vivo, to be able to maximize the attainable signal-to-noise ratio per unit of time through accurate localization from arbitrarily shaped region of interests. The work was first utilized on small animal scanners (Bruker, 4T; Varian, 4.7T/9.4T); however, it can be easily applied to a human scanner. This is currently underway at Vanderbilt University (Philips, 3T/7T).

1) Maximizes signal to noise ratio per unit of time
2) Minimizes partial volume effects
3) Easily implemented on any Magnetic Resonance Scanner

Instrument Business outlook predicts that the global market for laboratory molecular spectroscopy, which was worth more than $2.6 billion in 2005, will continue to show moderate single-digit growth of about 9%. According to Frost and Sullivan, Magnetic Resonance is one of the strongest markets in the imaging industry.

Currently, single-voxel localization techniques for MRS (PRESS/STEAM/ISIS) are restricted to selecting only rectangular-shaped regions of interest. Often these rectangular shaped areas include additional tissue outside of the specific region of interest. Since metabolites vary immensely from tissue to tissue, it is critical to only include tissue of interest in order to obtain accurate data. Another approach is to use higher field, but that technique is very expensive.

Vanderbilt University holds the copyright on the ASSESS technology, as well as the trademark on both "2D Arbitrary Shape Selective Excitation Summed Spectroscopy" and "ASSESS." Furthermore, Vanderbilt holds the U.S. Patent # 7,777,488 for this technology.