Noninvasive Histologic Grading of Solid Astrocytomas Using Proton Magnetic Resonance Spectroscopy
Stereotactic and Functional Neurosurgery
Background: Proton magnetic resonance spectroscopy (1H MRS) constitutes a promising modality to assess intracranial pathology. We present our experience using this method in grading solid brain astrocytomas.
Material and Methods: Using a 1.5-Tesla MRI unit, 71 patients with the radiographic diagnosis of astrocytoma were examined. Water-suppressed single-voxel 1H MRS was employed in all of our patients. The concentrations of choline (Cho), N-acetyl-aspartate (NAA), phosphocreatine-creatine (Pcr-Cr), myo-inositol (MI), lactate (Lac), lipids (Lip) as well as the metabolite ratios of Cho/Pcr-Cr, NAA/PCr-Cr and NAA/Cho were calculated. An appropriate surgical biopsy was performed. Standard pathology examination was employed in a double-blinded fashion.
Results: An increased concentration of Cho and decreased concentrations of Pcr-Cr and NAA were detected. The concentrations of Lac, Lip and MI varied inconsistently, even among tumors of the same histologic grade. The Cho/Pcr-Cr ratio was calculated. This ratio was found to be 2.15 +/- 0.26 in 27 patients with astrocytomas grade I and II, 2.78 +/- 0.09 in 18 patients with grade III, and 5.40 +/- 0.16 in 26 patients with grade IV.
Discussion: The increased concentration of Cho is due to the increased cellularity and a relatively increased number of membranous structures in highly malignant tumors. In abnormal anaerobic metabolic tumor states there is relatively less phosphorylization of creatine. By using the Cho/Pcr-Cr ratio the concomitant effects of structural and metabolic alteration can thereby be emphasized for diagnostic advantage.
Conclusion: The Cho/Pcr-Cr is a very important and statistically significant marker (p = 0.043) determining the degree of intracranial astrocytoma malignancy.
Fountas, Kosta N., Eftychia Z. Kapsalaki, Robert L. Vogel, Ionnis Fezoulidis, Joe S. Robinson, Efstathios Gotsis.
"Noninvasive Histologic Grading of Solid Astrocytomas Using Proton Magnetic Resonance Spectroscopy."
Stereotactic and Functional Neurosurgery, 82 (2-3): 90-97.