Hunter's angle (HA) is a term coined from a neurosurgeon, Hunter Sheldon, at Huntington Medical Research Institutes. He placed his comb on the spectrum at approximately a 45° angle and connected several of the peaks. If the angle and peaks roughly corresponded to the 45° angle, the curve was considered probably normal. If the peaks strayed off the comb's angle, the curve was abnormal. This is a quick and useful visual method to read MRS and determine normal from abnormal. It is important to remember, however, that this angle was used with STEAM spectra from the brain 2.
Hunter's angle is the line formed by the metabolites in MR spectroscopy.
Metabolites myoinositol, choline, creatine, and N-acetyl aspartate (NAA) peaks are ascending in normal spectrum (Figure 1), any alteration in the ascending nature of the peaks means the spectrum is abnormal.
Hunters angle is an alternative of doing complex ratios and analysis of the spectra.
- 1. Lin A, Ross BD, Harris K et-al. Efficacy of proton magnetic resonance spectroscopy in neurological diagnosis and neurotherapeutic decision making. NeuroRx. 2005;2 (2): 197-214. doi:10.1602/neurorx.2.2.197 - Free text at pubmed - Pubmed citation
- 2. Mangrum W, Christianson K, Duncan S et-al. Duke Review of MRI Principles. Mosby. (2012) ISBN:1455700843. Read it at Google Books - Find it at Amazon
MR spectroscopy (MRS)
- Hunter's angle
- lactate peak: resonates at 1.3 ppm
- lipids peak: resonate at 1.3 ppm
- alanine peak: resonates at 1.48 ppm
- N-acetylaspartate (NAA) peak: resonates at 2.0
- glutamine-glutamate peak: resonate at 2.2-2.4 ppm
- gamma-aminobutyric acid (GABA) peak: resonate at 2.2-2.4 ppm
- citrate peak: resonates at 2.6 ppm
- creatine peak: resonates at 3.0 ppm
- choline peak: resonates at 3.2 ppm
- myo-inositol peak: resonates at 3.5 ppm