Abstract: A heat and moisture exchanger, comprises a rigid monolithic body (101). The rigid monolithic body (101) comprises a circumferential wall (102); and a structure of interconnected elements (106) surrounded by the circumferential wall (102). The structure (106) is open to fluid communication through the structure (106) between a first side (114) of the structure and a second side (115) of the structure (106) opposite the first side (114) of the structure (106). The circumferential wall (102) extends from the first side (114) to the second side (115) of the structure (106). The heat and moisture exchanger (100) is open on both of the first side (114) and the second side (115) of the structure (106), to allow fluid communication between the structure (106) and an exterior of the heat and moisture exchanger (100) on both sides (114, 115).

Abstract: A method and system for non-invasive quantitative assessment of radionuclide tracer levels in the blood stream. The method relies on the finding that the gamma-radiation signal acquired using a gamma scintillation probe, is the resultant from a wave-component with changing amplitude, resulting from the radiotracer in the bloodstream and a non-wave background component resulting from radiotracer distributed throughout the tissue surrounding the arterial vessel. The method involves phase-sensitive conversion of the ‘input signal’, extracting there from an output signal representing the signal component originating from the bloodstream, using the changes in arterial blood volume as the reference wave-form. A particular aspect of the invention concerns methods of quantitative PET or SPECT imaging wherein the concentration of radionuclides in the blood stream as a function of time after injection is assessed using the method of the invention.