Metabolic alterations: a biomarker for radiation-induced normal brain injury-an MR spectroscopy study.
OBJECTIVE
To assess if interval changes in metabolic status in normal cerebral tissue after radiation therapy (RT) can be detected by 2D CSI (chemical shift imaging) proton spectroscopy.


METHODS
Eleven patients with primary brain tumors undergoing cranial radiation therapy (RT) were included. 2D-CSI MRS was performed before, during, and after the course of RT with the following parameters: TE/TR 144/1500 ms, field of view (FOV) 24, thickness 10 mm, matrix 16 x 16. The metabolic ratios choline/creatine (Cho/Cr), N-acetylaspartate (NAA)/Cr, and NAA/Cho in normal brain tissue were calculated.


RESULTS
NAA/Cr and Cho/Cr were significantly decreased at week 3 during RT and at 1 month and 6 months after RT compared to values prior to RT (P < 0.01). The NAA/Cr ratio decreased by -0.19 +/- 0.05 (mean +/- standard error [SE]) at week 3 of RT, -0.14 +/- 0.06 at the last week of RT, -0.14 +/- 0.05 at 1 month after RT, and -0.30 +/- 0.08 at 6 months after RT compared to the pre-RT value of 1.43 +/- 0.04. The Cho/Cr ratio decreased by -0.27 +/- 0.05 at week 3 of RT, -0.11 +/- 0.05 at the last week of RT, -0.26 +/- 0.05 at 1 month after RT and -0.25 +/- 0.07 at 6 months after RT from the pre-RT value of 1.29 +/- 0.03. Changes in Cho/Cr were correlated with the interaction of the radiation dose and dose-volume at week 3 of RT, during the last week of RT (P < 0.005), and at 1 month after RT (P = 0.017).


CONCLUSIONS
The results of this study suggest that MRS can detect early metabolic changes in normal irradiated brain tissue.
Sundgren
P C
PC
Department of Radiology, University of Michigan University Health Systems, Ann Arbor, Michigan 48109, USA. sundgren@med.umich.edu
Nagesh
V
V
Elias
A
A
Tsien
C
C
Junck
L
L
Gomez Hassan
D M
DM
Lawrence
T S
TS
Chenevert
T L
TL
Rogers
L
L
McKeever
P
P
Cao
Y
Y
D000328:Adult; D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001921:Brain / Q000378:metabolism / Q000528:radiation effects*; D001932:Brain Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D002794:Choline / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011832:Radiation Injuries / Q000378:metabolism*
D001224:Aspartic Acid; D003401:Creatine; D002794:Choline