BOLD MRI of human tumor oxygenation during carbogen breathing.

An MRI method is described for demonstrating improved oxygenation of human tumors and normal tissues during carbogen inhalation (95% O2, 5% CO2). T2*-weighted gradient-echo imaging was performed before, during, and after carbogen breathing in 47 tumor patients and 13 male volunteers. Analysis of artifacts and signal intensity was performed. Thirty-six successful tumor examinations were obtained. Twenty showed significant whole-tumor signal increases (mean 21.0%, range 6.5-82.4%), and one decreased (-26.5 +/- 8.0%). Patterns of signal change were heterogeneous in responding tumors. Five of 13 normal prostate glands (four volunteers and nine patients with nonprostatic tumors) showed significant enhancement (mean 11.4%, range 8.4-14.0%). An increase in brain signal was seen in 11 of 13 assessable patients (mean 8.0 +/- 3.7%, range 5.0-11.7%). T2*-weighted tumor MRI during carbogen breathing is possible in humans. High failure rates occurred due to respiratory distress. Significant enhancement was seen in 56%, suggesting improved tissue oxygenation and blood flow, which could identify these patients as more likely to benefit from carbogen radiosensitization.

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 oxygenation and blood flow, in response to carbogen (95% O2, 5% CO2) breathing. 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 breathing. 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, while 11 showed no response; 6 studies were technical failures. In one patient a metastatic node that had eluded orthodox investigation was visualized. A reduction in response was observed in the three patients studied postradiotherapy. CONCLUSION: This method, which can be performed on a standard clinical MRI instrument, provides a noninvasive measurement of tumor response to oxygenation/blood flow modification. In principle, this should enable the clinician to optimize treatment protocols, such as carbogen breathing, for individual radiotherapy patients.