Diagnosis and Evaluation

Meeting Abstract

H-MR Spectroscopic Imaging-guided Surgery of Brain Tumors and correlation with Neuropathology

A Bizzi, U. Danesi, B. Pollo, L. Bissola, P. Ferroli, C. Solero, A. Boiardi, G. Broggi

Istituto Neurologico Besta, Milano, Italy.

Purpose. Evaluate H-MR spectroscopic imaging in detecting tumor heterogeneity and infiltration to be used for guiding biopsy or surgical resection. 
Determine whether elevated choline correlates with cellular density, proliferation and/or grade.

Methods and Materials. Twenty-eight patients (M:F=16:12; mean age: 44 yrs.) with a new untreated intracranial mass were evaluated pre-operatively with H-MRSI using the multivoxel PRESS volume selection technique (TR/TE=1500/136; 2D phase-encoding). 
H-MRSI coordinates of surgical specimens were recorded using a intraoperative neuronavigation device. 
Biopsy slides were stained with HE, GFAP, vimentin and MIB1. 
In few patients genetic markers were investigated. 
The following histopathological diagnosis were made: 20 high grade gliomas, 6 low grade gliomas, 1 PNET, 1 metastatic carcinoma. 
Areas of choline, creatine and NAA signals were integrated and normalized to contralateral normal spectra. 
The Cho/NAA, Cho/Cr and Cr/NAA ratios for voxels within and around the T2-w. signal abnormality were calculated. 
Lesions were classified in homogeneous or heterogeneous, well-defined or infiltrating/multicenter by H-MRSI and MRI.

Results. Cho was elevated in all types of tumors with nCho values in the range between 1.5 and 5.4. 
In 5/28 cases we unexpectedly found moderate Cr elevation (Cho/Cr near or less than one): all 5 cases were astrocytomas (grade II and III) with intensive GFAP positive cells. 
Low grade gliomas had homogeneous abnormal spectra with well-defined borders; anaplastic astrocytomas showed an infiltrating appearance. 
Glioblastoma multiforme subdivided in two groups: with ”well-defined borders„; and with infiltrating appearance. 
Elevated nCho best correlated with cellular density.

Conclusion. 1. H-MRSI is a sensitive tool to depict tumor heterogeneity and borders and it is more specific than conventional MRI.
2. H-MRSI-guidance may improve pre-operative planning in heterogeneous, infiltrating lesions.
3. A new H-MRS profile was identified: the elevation of Cr with Cho was seen only in astrocytomas and it may suggest a specific tumor type.
4. Choline is elevated in all tumors and best correlates with cellular density.