THE RESPONSE OF HUMAN TUMORS TO CARBOGEN BREATHING, MONITORED BY GRADIENT-RECALLED ECHO MAGNETIC-RESONANCE-IMAGING

Purpose: Gradient-Recalled Echo (GRE) Magnetic Resonance Imaging (MRI) , which detects changes in blood vessel deoxyhaemoglobin content, has been investigated as a noninvasive monitor of changes in human tumor o xygenation and blood flow, in response to carbogen (95% O-2, 5% CO2) b reathing. Methods and Materials: GRE images (TE = 60 ms, TR = 200 ms, alpha = 40 degrees, 256(2) matrix) were acquired from 31 patients with primary and metastatic disease, prior to and during carbogen breathin g. Three patients underwent a follow-up examination after radiotherapy . Results: Seventeen out of 34 tumors showed enhanced image intensity, consistent with an improvement in tumor oxygenation and blood flow, w hile 11 showed no response; 6 studies were technical failures. In one patient a metastatic node that had eluded orthodox investigation was v isualized. A reduction in response was observed in the three patients studied postradiotherapy. Conclusion: This method, which can be perfor med on a standard clinical MRI instrument, provides a noninvasive meas urement of tumor response to oxygenation/blood flow modification. In p rinciple, this should enable the clinician to optimize treatment proto cols, such as carbogen breathing, for individual radiotherapy patients . (C) 1997 Elsevier Science Inc.