Changes in oxygenation of intracranial tumors with carbogen: a BOLD MRI and EPR oximetry study.
OBJECTIVE
To examine, using blood oxygen level dependent (BOLD) MRI and EPR oximetry, the changes in oxygenation of intracranial tumors induced by carbogen breathing.


METHODS
The 9L and CNS-1 intracranial rat tumor models were imaged at 7T, before and during carbogen breathing, using a multi-echo gradient-echo (GE) sequence to map R(2)*. On a different group of 9L tumors, tissue pO(2) was measured using EPR oximetry with lithium phthalocyanine as the oxygen-sensitive material.


RESULTS
The average decline in R(2)* with carbogen breathing was 13 +/- 1 s(-1) in the CNS-1 tumors and 29 +/- 4 s(-1) in the 9L tumor. The SI vs. TE decay curves indicate the presence of multiple components in the tumor. Tissue pO(2) in the two 9L tumors measured was 8.6 +/- 0.5 and 3.6 +/- 0.6 mmHg during air breathing, and rose to 20 +/- 7 and 16 +/- 4 mmHg (mean +/- SE) with carbogen breathing. Significant changes were observed by 10 minutes, but changes in pO(2) and R(2)* continued in some subjects over the entire 40 minutes.


CONCLUSIONS
EPR results indicate that glial sarcomas may be radiobiologically hypoxic. Both EPR and BOLD data indicate that carbogen breathing increases brain tumor oxygenation. These data support the use of BOLD imaging to monitor changes in oxygenation in brain tumors.
Dunn
Jeff F
JF
NMR and EPR Research Centers, Department of Diagnostic Radiology, Dartmouth Hitchcock Medical Center, Hanover, New Hampshire, USA. jeffrey.f.dunn@dartmouth.edu
O'Hara
Julia A
JA
Zaim-Wadghiri
Youssef
Y
Lei
Hao
H
Meyerand
M Elizabeth
ME
Grinberg
Oleg Y
OY
Hou
Huagang
H
Hoopes
P Jack
PJ
Demidenko
Eugene
E
Swartz
Harold M
HM
D000818:Animals; D001254:Astrocytoma / Q000378:metabolism* / Q000473:pathology; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology; D002245:Carbon Dioxide / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D008279:Magnetic Resonance Imaging; D009368:Neoplasm Transplantation; D010092:Oximetry; D010100:Oxygen / Q000378:metabolism* / Q000494:pharmacology*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D051381:Rats; D011917:Rats, Inbred Lew; D014407:Tumor Cells, Cultured
D011838:Radiation-Sensitizing Agents; D002245:Carbon Dioxide; C011700:carbogen; D010100:Oxygen