Abstract
A new method for measuring distances using electrically charged jets of water is described,
and its precision examined. When combined with endoscopy, this method can be utilized
to measure the lengths and areas of objects inside human body cavities. The apparatus
used consists of a catheter with three metal needles at the tip, a personal computer,
and a commercially available videoendoscopy system. To test the system, a regulated
voltage was passed between the catheter tip and a wooden board, and two salt solutions
of different concentrations were ejected at three different angles from the catheter
to the board. The coordinates of the board were then computed from the amperages of
the currents passing through the three jets of saline, and optical distortion was
corrected using the computer. The length and area of an object could be measured rapidly
by setting electrically the coordinates to match the endoscopic image. Lengths ranging
from 10 to 50 mm were measured while varying the distance between catheter tip and
board (10, 20, and 30 mm), as well as the angle formed by the catheter and the board
(45, 60, and 90 degrees). The mean measurement error was less than 5.6 % and accuracy
was relatively independent of the angle between catheter and target.
