Preoperative proton MR spectroscopic imaging of brain tumors: correlation with histopathologic analysis of resection specimens.
OBJECTIVE
Tumor progression is often difficult to distinguish from nonneoplastic treatment response on the basis of MR images alone. This study correlates metabolite levels measured by preoperative MR spectroscopic (MRS) imaging with histologic findings of biopsies, obtained during image-guided resections of brain mass lesions, to clarify the potential role of MRS in making this distinction.


METHODS
Twenty-nine patients with brain tumors underwent high-resolution (0.2-1 cc) 3D proton MRS imaging and MR imaging before undergoing surgery; 11 had a newly diagnosed neoplasm, and 18 had recurrent disease. Surgical biopsies were obtained from locations referenced on MR images by guidance with a surgical navigation system. MR spectral voxels were retrospectively centered on each of 79 biopsy locations, and metabolite levels were correlated with histologic examination of each specimen.


RESULTS
All mass lesions studied, whether attributable to tumor or noncancerous effects of previous therapy, showed abnormal MR spectra compared with normal parenchyma. When the pattern of MRS metabolites consisted of abnormally increased choline and decreased N-acetyl aspartate (NAA) resonances, histologic findings of the biopsy specimen invariably was positive for tumor. When choline and NAA resonances were below the normal range, histologic findings were variable, ranging from radiation necrosis, astrogliosis, and macrophage infiltration to mixed tissues that contained some low-, intermediate-, and high-grade tumor.


CONCLUSIONS
This study demonstrated that 3D MRS imaging can identify regions of viable cancer, which may be valuable for guiding surgical biopsies and focal therapy. Regions manifesting abnormal MR spectra had a mixture of histologic findings, including astrogliosis, necrosis, and neoplasm.
Dowling
C
C
Department of Radiology, University of California, San Francisco 94143-1290, USA.
Bollen
A W
AW
Noworolski
S M
SM
McDermott
M W
MW
Barbaro
N M
NM
Day
M R
MR
Henry
R G
RG
Chang
S M
SM
Dillon
W P
WP
Nelson
S J
SJ
Vigneron
D B
DB
D000293:Adolescent; D000328:Adult; D000368:Aged; D016477:Artifacts; D001706:Biopsy; D001921:Brain / Q000473:pathology / Q000601:surgery; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D005260:Female; D005910:Glioma / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D013238:Stereotaxic Techniques