Magnetic Resonance Spectroscopy

POLICY NUMBER

A.6.01.24

DESCRIPTION

Magnetic resonance spectroscopy (MRS) is a noninvasive technique that can be used to measure the concentrations of different chemical components within tissues. The technique is based on the same physical principles as magnetic resonance imaging (MRI) and the detection of energy exchange between external magnetic fields and specific nuclei within atoms. With MRI, this energy exchange, measured as a radiofrequency signal, is then translated into the familiar anatomic image by assigning different gray values according to the strength of the emitted signal. The principal difference between MRI and MRS is that the emitted radiofrequency in MRI is based on the spatial position of nuclei, while MRS detects the chemical composition of the scanned tissue. The information produced by MRS is displayed graphically as a spectrum with peaks consistent with the various chemicals detected. MRS may be performed as an adjunct to MRI. An MRI image is first generated, and then MRS spectra are developed at the site of interest, at the level of the voxel(3-dimensional volume X pixel). The voxel of interest (VOI) is typically a cube or rectangular prism with a dimensional pixel with a volume of 1 to 8 cm³. While an MRI provides an anatomic image of the brain, MRS provides a functional image related to underlying dynamic physiology. MRS can be performed with existing MRI equipment, and modified with additional software and hardware, which are provided with all new MRI scanners. Imaging time in the scanner is increased by 15 to 30 minutes.

MRS has been studied most extensively in a variety of brain pathologies. In the brain, both 1-H (i.e., hydrogen proton) and 31-P are present in concentrations high enough to detect and thus have been used extensively to study brain chemistry. Proton MRS of the brain reveals 6 principal spectra. They include those:

Different patterns of these spectra and others (eg, myo-inositol, glutamate/glutamine) in the healthy and diseased brain, are the basis of clinical applications of MRS. The MRS findings characteristically associated with non-necrotic brain tumors include elevated Cho levels and reduced N-acetylaspartate (NAA) levels. The International Network for Pattern Recognition using Magnetic Resonance has developed a user-friendly computer program for spectral classification and a database of over 300 tumor spectra with histologically validated diagnoses to aid radiologists in MRS diagnosis.

One limitation of MRS is that it provides the metabolic composition of a given voxel, which may include more than one type of tissue. For some applications, the voxels are relatively large (eg, >1 cm³), although they may be somewhat smaller using a 3-tesla MRI machine versus a 1.5-tesla magnet. High-field strength increases the signal to noise ratio and spectral resolution. The 3-Tesla technique creates greater inhomogeneities, however, which require better shimming techniques. There are 2 types of MRS data acquisition: single-voxel or simultaneous multivoxel, also called chemical shift imaging. Reliable results are more difficult to obtain from some areas, eg, close to the brain surface or in children with smaller brains because of the lipid signal from the skull. Some techniques are used to deal with these issues; various MRS techniques continue to be explored as well. A combination of MRS is often used with other MRI techniques (eg, diffusion-tensor imaging, susceptibility-weighted imaging) and other types of imaging such as positron emission tomography.

Peripheral applications of MRS include the study of myocardial ischemia, peripheral vascular disease, and skeletal muscle. Applications in non-central nervous system oncologic evaluation have also been explored.

All findings reported in this policy refer to proton MRS, unless otherwise indicated.

Use of positron emission tomography (PET) in Alzheimer disease is addressed separately in the Selected Positron Emission Tomography Technologies for Evaluation of Alzheimer Disease medical policy.

Multiple software packages for performing proton MRS have been cleared for marketing by the U.S. Food and Drug Administration (FDA) through the 510(k) process since 1993. Single-voxel MRS is available on all modern magnetic resonance imaging scanners.

POLICY

Magnetic resonance spectroscopy is considered investigational.

POLICY EXCEPTIONS

Federal Employee Program (FEP) may dictate that all FDA-approved devices, drugs or biologics may not be considered investigational and thus these devices may be assessed only on the basis of their medical necessity.

POLICY GUIDELINES

The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.

Investigative is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized as a generally accepted standard of good medical practice for the treatment of the condition being treated and; therefore, is not considered medically necessary. For the definition of Investigative, “generally accepted standards of medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. In order for equipment, devices, drugs or supplies [i.e, technologies], to be considered not investigative, the technology must have final approval from the appropriate governmental bodies, and scientific evidence must permit conclusions concerning the effect of the technology on health outcomes, and the technology must improve the net health outcome, and the technology must be as beneficial as any established alternative and the improvement must be attainable outside the testing/investigational setting.

POLICY HISTORY

5/28/2008: Policy added.

12/28/2010: Policy description and statement unchanged. Add FEP verbiage to the Policy Exceptions section.

01/18/2012: Policy reviewed; no changes.

04/01/2013: Policy reviewed; no changes.

03/10/2014: Policy reviewed; no changes.

01/22/2015: Policy description updated regarding 6 principal spectra, limitations of MRS, and types of MRS data acquisition. Policy statement unchanged.

07/31/2015: Code Reference section updated for ICD-10.

01/18/2016: Policy description updated. Policy statement unchanged. Investigative definition updated in policy guidelines section.

05/31/2016: Policy number A.6.01.24 added.

10/16/2017: Policy description updated. Policy statement unchanged.

10/04/2018: Policy reviewed; no changes.

10/22/2019: Policy reviewed; no changes.

06/22/2020: Code Reference section updated to add new CPT codes 0609T, 0610T, 0611T, and 0612T, effective 07/01/2020.

10/14/2020: Policy reviewed; no changes.

01/17/2022: Policy reviewed; no changes.

12/13/2022: Policy description updated. Policy statement unchanged.

11/15/2023: Policy reviewed; no changes.

01/13/2025: Policy reviewed; no changes.

SOURCE(S)

Blue Cross & Blue Shield Association Policy # 6.01.24

CODE REFERENCE

This may not be a comprehensive list of procedure codes applicable to this policy.

Investigational Codes

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