THE USE OF HYPERVENTILATION IN CONTRAST-ENHANCED MR OF BRAIN-TUMORS

Angiographic studies have demonstrated improved visibility of glial tu mors after hyperventilation. The present study was undertaken to deter mine whether hyperventilation would change the MR enhancement characte ristics of various glial tumors. Eighteen patients were studied twice: once with standard contrast-enhanced MR imaging and again with standa rd imaging plus hyperventilation. After hyperventilation, six low-grad e astrocytomas showed no change and three showed a small decrease in r elative enhancement (<10%), The ependymomas showed a 10% to 13% increa se in the degree of enhancement, but no change in the area of enhancem ent. All the anaplastic astrocytomas showed an increase in the degree of enhancement (mean, 38%), Three of the anaplastic astrocytomas showe d new foci of enhancement that were not seen on the nonhyperventilatio n study, Hyperventilation appears to be an inexpensive and safe method for increasing the conspicuity of abnormal areas of the blood-brain b arrier.