The importance of endothelium and interstitial fluid in nuclear medicine
The interstitial space (ISS) can be thought of as an organ of translocation. Defined in this way the concentration of any substance in the ISS is equal to the ratio of an input to a clearance function. When substances accumulate, there is a disturbance of one or both functions. The three phase anatomy of the ISS give it unique properties including a high resistance to bulk flow, normal or even augmented diffusion of small ions, marked restriction to macromolecular transport, and some specificity for binding certain substances. Depositional disease in the interstitium can be approached in terms of minimizing the input function or maximizing the clearance function of the deposited substance. In the near future the clinician will have access to importance physical parameters of the ISS.