Evaluation of the imaging aspects of brain tumors by Magnetic Resonance Spectroscopy

ABSTRACT

Magnetic resonance spectroscopy (MRS) is an established tool for in-vivo evaluation of the biochemical basis of human diseases. Magnetic resonance spectroscopy (MRS) provides a means to assess functional (metabolic activity) of the brain. On one hand, such lucid depiction of ‘live biochemistry’ helps one to decipher the true nature of the pathology while on the other hand one can track the response to therapy at sub-cellular level. Brain tumors have been an area of continuous interrogation and instigation for mankind. Our aim was to do valuation of these lesions by MRS. Methods: This study was conducted in a tertiary care hospital in which all patients underwent magnetic resonance imaging (MRI) at the same setting as the MRS examination. The MRS examination was performed with the stimulated echo acquisition mode (STEAM) pulse sequence in all children, and occasionally the point resolved spectroscopy (PRESS) sequence also was used. Qualitative spectra were obtained in all patients, and at times quantification data also were obtained. Results: We found that our spectra over the brain neoplasms were consistent with the MRS findings of brain neoplasms in the literature. There was markedly elevated choline with markedly decreased or absent N-acetylasparate and at times elevated lactate and lipid peaks. In children with meningiomas, there was also an elevated alanine peak. We found MRS to be extremely useful in 1) characterizing a brain mass as a neoplasm, 2) differentiating radiation necrosis and radiation-induced meningiomas from the recurrent primary tumor, 3) following treatment response of the primary neoplasm, 4) differentiating residual or recurrent primary neoplasm from postsurgical changes, and 5) identifying inactive neoplasms or neoplasms in remission. Conclusion: By having a basic understanding of the automated MRS in the normal brain for the different pulse sequences (STEAM and PRESS), it is possible to understand the abnormal MRS spectra seen in brain neoplasms.