Hydrogen MR Spectroscopy of Brain Tumors

Okolzin ., Trufanov G., Fokin V., Martinov B.

Medicomilitary Academy, Saint Petersburg, Russia

 

The research goal was studying efficacy of 1H MR spectroscopy (MRS) in diagnosis of brain tumors. MRS was based on use of two methods: CSI (Chemical Shift Imaging) and SVS (Single Volume Spectroscopy). They made it possible to get spectra of such various metabolites as N-acetylaspartate (NAA), creatine (Cr), choline (Cho), alanine (Ala), lactate (Lac), myo-inositol, citrate and to determine their concentration.

Material and Methods. MRT and hydrogen spectroscopy were carried out with applying a high-field MR tomograph. There were 74 cases with glial cerebral tumors, subject to MRT and MRS examinations. Rentgenographic CT, cerebral angiography and PET were used in 71%, 70% and 11% of cases respectively. Stereotaxic or postoperative biopsy allowed to carry out a histological study in 80% of patients.

Results. A content of metabolites was determined on the basis of spectra, obtained with MRS. A normal ratio of metabolites was as follows: the white substance -NAA/C=1.85±0.3, Cho/Cr=1.05±0.14, NAA/Cho=1.58±0.22; the gray substance - NAA/Cr=1.75±0.28, Cho/Cr=1.15±0.15, NAA/Cho=1.50±0.2. Benign tumors (Grade I, II) were characterized by the following indices: NAA/Cr=0.45±0,12, Cho/Cr=1.56±0.16, NAA/Cho=0.43±0.1, Lac/Cr=0.37±0.05. The same indices for malignant tumors (Grade III, IV) were as follows: NAA/Cr=0.73±0.16, Cho/Cr=3.26±0.61, NAA/Cho=0.22±0.08, Lac/Cr=1.41±0.21. Pathologic spikes, indicative of an increased content of alanine, were watched in meningiomas.

Conclusion. Thus, MRS is a non-invasive and highly informative method, permitting to differentiate a pathologic focus at a biochemical level and to make a supposition on a degree of tumor malignancy.