Remote measurement of fluid volume by x-ray fluorescence

A technique utilizing x-ray fluorescence has been used to measure remotely the volume and, thereby, the hydrostatic pressure of a cesium nitrate solution in vitro. The excitation radiation source was 99m-Tc, and the x-ray spectra were measured with a sodium iodide spectrometry system. This technique may be applicable to long term in vivo measurements of intracranial pressure for conditions such as hydrocephalus.