An apparatus and method for measuring the volume of an object with particular
application to measuring the volume changes in the limbs of patients suffering
from lymphedema. The apparatus is comprised of a cylinder having a measurement
chamber for placing a patient's limb. The chamber is sealed and a gas having known
light absorption characteristics is injected into the chamber and mixed with the
ambient air therein. A reference laser beam is projected through ambient air to
a photocell on the cylinder and the optical absorption value of the reference beam
is recorded. A second laser beam is projected through the air-gas mixture of the
measurement chamber and the light absorption value is recorded. The ratio of the
absorption value of the reference beam to the second laser beam is determined and
this value is used to calculated a value which is proportional to gas concentration,
which in turn is proportional to the volume of an object placed within the cylinder.
