Differentiation between brain tumor recurrence and radiation injury using MR spectroscopy.
OBJECTIVE
The purpose of our study was to explore the feasibility and utility of 2D chemical shift imaging (CSI) MR spectroscopy in the evaluation of new areas of contrast enhancement at the site of a previously treated brain neoplasm.


METHODS
Two-dimensional CSI (point-resolved spectroscopy sequence [PRESS]; TR/TE, 1,500/144) was performed in 29 consecutive patients (4-54 years old; mean age, 34 years) who had a new contrast-enhancing lesion in the vicinity of a previously diagnosed and treated brain neoplasm. Clinical and imaging follow-up, and histopathology in 16 patients, were used as indicators of the identity of a lesion.


RESULTS
Diagnostic-quality spectra were obtained in 97% of the patients. The Cho/Cr (choline/creatine) and Cho/NAA (choline/N-acetyl aspartate) ratios were significantly higher, and the NAA/Cr ratios significantly lower, in tumor than in radiation injury (all three differences, p < 0.0001). The Cho/Cr and Cho/NAA ratios were significantly higher in radiation injury than in normal-appearing white matter (p < 0.0003 and p < 0.0001, respectively), whereas NAA/Cr ratios were not different (p = 0.075). Mean Cho/Cr ratios were 2.52 for tumor, 1.57 for radiation injury, and 1.14 for normal-appearing white matter. Mean Cho/NAA ratios were 3.48, 1.31, 0.79, and mean NAA/Cr ratios were 0.79, 1.22, and 1.38, respectively. When values greater than 1.8 for either Cho/Cr or Cho/NAA ratios were considered evidence of tumor, 27 of 28 patients could be correctly classified.


CONCLUSIONS
Two-dimensional CSI MR spectroscopy can differentiate tumor from radiation injury in patients with recurrent contrast-enhancing intracranial lesions. In these lesions, the Cho/NAA and Cho/Cr ratios may be the best numeric discriminators.
Weybright
Patrick
P
Department of Radiology, University of Michigan, Ann Arbor, MI 48109-0030, USA.
Sundgren
Pia C
PC
Maly
Pavel
P
Hassan
Diana Gomez
DG
Nan
Bin
B
Rohrer
Suzan
S
Junck
Larry
L
D000293:Adolescent; D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001932:Brain Neoplasms / Q000737:chemistry / Q000175:diagnosis* / Q000532:radiotherapy; D002648:Child; D002675:Child, Preschool; D002794:Choline / Q000378:metabolism; D003287:Contrast Media; D003401:Creatine / Q000378:metabolism; D003937:Diagnosis, Differential; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis*; D011832:Radiation Injuries / Q000175:diagnosis*
D003287:Contrast Media; D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline