The use of hyperventilation in contrast-enhanced MR of brain tumors.

Angiographic studies have demonstrated improved visibility of glial tumors after hyperventilation. The present study was undertaken to determine whether hyperventilation would change the MR enhancement characteristics of various glial tumors. Eighteen patients were studied twice: once with standard contrast-enhanced MR imaging and again with standard imaging plus hyperventilation. After hyperventilation, six low-grade astrocytomas showed no change and three showed a small decrease in relative enhancement (<10%). The ependymomas showed a 10% to 13% increase in the degree of enhancement, but no change in the area of enhancement. All the anaplastic astrocytomas showed an increase in the degree of enhancement (mean, 38%). Three of the anaplastic astrocytomas showed new foci of enhancement that were not seen on the nonhyperventilation study. Hyperventilation appears to be an inexpensive and safe method for increasing the conspicuity of abnormal areas of the blood-brain barrier.