MRI measurements correctly predict the relative effects of tumor oxygenating agents on hypoxic fraction in rodent BA1112 tumors.
OBJECTIVE
We evaluate whether magnetic resonance imaging (MRI) with blood oxygenation level-dependent (BOLD) contrast correctly predicts the relative effects of tumor-oxygenating agents on hypoxic fraction in BA1112 rhabdomyosarcomas in WAG/Rij rats.


METHODS
The response of ten tumors to carbogen (95% O(2)/5% CO(2)), a perfluorocarbon emulsion (PFC), and the combination of PFC + carbogen was studied with high spectral and spatial resolution MR imaging of the water resonance at 4.7 Tesla. Decreases in MR signal linewidth indicate increases in tumor blood oxygen levels.


RESULTS
Average MR signal linewidth was decreased 2.0% by carbogen, 2.5% by PFC + air, and 4.9% by PFC + carbogen. PFC + carbogen caused a larger linewidth decrease than either treatment alone (p < 0.04 by ANOVA). Maps of pixels responding to treatment indicate that combining PFC with carbogen significantly enlarges the area of the tumor in which oxygen levels are increased (p < 0.01 by ANOVA).


CONCLUSIONS
MRI predicts that PFC + carbogen will increase radiosensitivity more than either treatment alone; this agrees with the known effects of these treatments on hypoxic fraction. Utilizing MRI to choose the treatment that maximizes the size and extent of increases in tumor oxygenation could reduce hypoxic fraction.
Al-Hallaq
H A
HA
Department of Radiology, The University of Chicago, Chicago, IL, USA.
Zamora
M
M
Fish
B L
BL
Farrell
A
A
Moulder
J E
JE
Karczmar
G S
GS
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000627:therapeutic use*; D015687:Cell Hypoxia / Q000187:drug effects; D005466:Fluorocarbons / Q000627:therapeutic use*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009368:Neoplasm Transplantation; D010100:Oxygen / Q000097:blood* / Q000627:therapeutic use*; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use*; D011853:Radiobiology; D051381:Rats; D012208:Rhabdomyosarcoma / Q000097:blood* / Q000503:physiopathology; D014407:Tumor Cells, Cultured
D005466:Fluorocarbons; D011838:Radiation-Sensitizing Agents; D002245:Carbon Dioxide; C011700:carbogen; D010100:Oxygen