Regional tumor oximetry: 19F NMR spectroscopy of hexafluorobenzene.
OBJECTIVE
An accurate method for monitoring oxygen tension (pO2) of individual tumors could be valuable for optimizing treatment plans. We have recently shown that 19F nuclear magnetic resonance (NMR) spin-lattice relaxometry of hexafluorobenzene (HFB) provides a highly sensitive indicator of tumor oxygenation. We have now refined the methodology to provide enhanced precision, and applied the method to investigate dynamic changes in tumor oxygenation.


METHODS
Dunning prostate adenocarcinoma R3327-AT1 was grown in the form of pedicles on the foreback of male Copenhagen rats. When the tumors reached approximately equal to 1 cm diameter, HFB (20 microl) was administered, either centrally or peripherally, by direct intratumoral (i.T) injection. Local pO2 was determined using pulse-burst saturation recovery (PBSR) 19F NMR spectroscopy on the basis of the spin-lattice relaxation rate, R1.


RESULTS
Interrogation of the central region of tumors provided typical values in the range pO2 = 1.4-6.4 mmHg, with a typical stability of +/-2 mmHg over a period of 20 min, when rats breathed 33% O2. Altering the inhaled gas to oxygen or carbogen (95% O2/5% CO2) produced no significant change. In contrast, interrogation of tumor periphery indicated baseline pO2 in the range 7.9-78.9 mmHg. Altering inspired gas produced significant changes (p < 0.0001) with O2 or carbogen, although the change was generally greater with carbogen. In each case, pO2 returned to baseline within 16 min of returning the inhaled gas to baseline.


CONCLUSIONS
We believe this method provides a valuable new approach with the requisite precision and accuracy to investigate tumor pO2.
Hunjan
S
S
Department of Radiology, UT Southwestern Medical Center, Dallas, TX 75235-9058, USA.
Mason
R P
RP
Constantinescu
A
A
Peschke
P
P
Hahn
E W
EW
Antich
P P
PP
D000818:Animals; D002245:Carbon Dioxide; D005461:Fluorine; D005466:Fluorocarbons / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010313:Partial Pressure; D011471:Prostatic Neoplasms / Q000378:metabolism*; D051381:Rats
D005466:Fluorocarbons; D002245:Carbon Dioxide; D005461:Fluorine; C011700:carbogen; C003005:hexafluorobenzene; D010100:Oxygen