Normal blood is about 1% sodium chloride or ordinary salt. This fact
makes possible the use of ²⁴Na in some measurements of the blood and
other fluids. The figure illustrates this technique. A sample of ²⁴NaCl
solution is injected into a vein in an arm or leg. The time the
radioisotope arrives at another part of the body is detected with a
shielded radiation counter. The elapsed time is a good indication of the
presence or absence of constrictions or obstructions in the circulatory
system.
[Illustration: Showing]
1 ²⁴NaCl solution injected
2 Blood carries ²⁴NaCl to both legs
3 High reading—good circulation
Site of constriction
4 Low reading—poor circulation
The passage of blood through the heart may also be measured with the aid
of sodium-24. Since this isotope emits gamma rays, measurement is done
using counters on the outside of the body, placed at appropriate
locations above the different sections of the heart.
[Illustration: Showing:]
1 ²⁴Na intravenously injected
To lungs, To body, From arm, From right lung, From left lung
2 Geiger counter detects radiations from ²⁴Na
3 Ink writing recorder shows route of ²⁴Na