ABSTRACT
Diagnosis of disease can be very difficult as a single disease might well affect several parts of the body. For example, renal failure will affect the composition of blood and this in turn can cause a range of symptoms elsewhere in the body. In this particular example the analysis of a blood sample will be an important part of the diagnostic process. However, if we wish to test specifically the function of the kidneys then a more invasive test is required. A common test is to inject a pharmaceutical which is specifically absorbed by the kidneys and to follow the process of absorption. A radioactive label can be attached to the pharmaceutical and then a gamma camera used to image the uptake and excretion by the kidneys (see section 6.9.2). Thus renal function can be tested by applying a stimulus and then observing the response which the stimulus evokes.
