Caption

Kidney function. Coloured SPECT (single photon emission computed tomography) scans showing the functioning of the human kidney. Sixteen scans are seen ranging over 30 minutes (from top left to bottom right) after the patient has been injected with a fluid that contains a radioactive tracer. These gamma-camera images show the accumulation of the radioactive tracer in the kidneys (seen as yellow & red), as the blood is filtered through the glomeruli. Greatest accumulation, correspond- ing the greatest filtering, is seen in the middle scans (10 to 20 minutes into the study).