Studies on regional cerebral pH in patients with cerebral tumours using continuous inhalation of 11CO2 and positron emission tomography.

Regional cerebral pH (rpH) was measured in 12 patients with cerebral tumours and in 5 normal subjects using continuous inhalation of 11CO2 and positron emission tomography (PET). Cerebral tumours with a disrupted blood-brain barrier (BBB) on computed tomography scanning had a similar rpH to that of equivalent regions of contralateral brain tissue (mean tumour rpH, 6.98; mean contralateral brain pH, 6.99). Cerebral tumours with an intact BBB were consistently found to be more alkaline than contralateral brain tissue (mean tumour rpH, 7.09). There was no significant difference between the mean rpH values obtained for peripheral cortical gray and central white matter in normal subjects (7.02 and 6.98, respectively). It is concluded that in spite of reports of raised levels of aerobic glycolysis in neoplastic tissue, there is no evidence that cerebral tumour rpH values are depressed.