is the temperature
the injectate through the catheter at the
delivery site. F, has been reported to be between
Measurement of Vascular Dimensions
Measurements of geometric dimensions of blood vessels, such as length,
quantifying dynamic behavior. Strain gages are popular for length
They are based either on
dimensional change or resistivity change. Change in resistance
is the cross-sectional area and
is the length of the strain gage
wire. The fractional change in resistance is given by:
is the Poisson ratio (ratio of radial strain to longitudinal strain).
The first term
the right-hand side is due to dimensional effect, the
second term to piezoresistive effect. Strain gage transducers can be
applied to measure length as well as pressure. In both cases, the resultant
change in resistance is detected by a Wheatstone bridge circuitry.
Superior resolution with high gage factors can be obtained with
High-resolution dimension measurement can also be obtained with
ultrasonic dimension gages. The disadvantage is more complex circuitry.
The method requires a pair of piezoelectric transducers
either sutured or glued on to the opposite sides of a vessel for pulsatile
diameter measurement or for wall thickness measurement. It is operated