Validation of a new technique for measurement of intracranial pressure with a scintillation counter.
Intracranial pressure sensors and subdural and subgaleal sensing tambours were used to measure the pressure difference between the intracranial and subgaleal spaces in two monkeys. The pressure differential was transmitted to fluid bathing a piston, to which an isotope source (145Pm) was attached. The radiation signal emanating through a fixed collimator was detected transcutaneously by a sodium iodide crystal contained within a photomultiplier tube connected to a scintillation counter. After in vitro testing of linearity, in vivo infusion studies were performed. Linearity between intracisternal pressure and radioactivity (r = 0.99; p less than 0.001) was established in the two experimental animals for an interval of 5 months and 1 year, respectively. Autopsy findings confirmed that the sensing tambours became encapsulated with a pseudomembrane that did not attenuate the pressure signal. The results of this investigation suggest that this method for measurement of intracranial pressure without transcutaneous connections may be suitable for long term monitoring of intracranial pressure.