Biomedical Engineering Reference
In-Depth Information
Figure 1.2: Geometric parameters of an artery that make it possible to measure
by means of intravascular ultrasound.
1.1 Technical Aspects of the IVUS
The images of ultrasound [7] are based on the reception and transmission of high-
frequency sound waves. The transmitted wave propagates through the material
until it strikes the reflecting object. The reflected wave returns and is received by
a transducer. The time interval between the transmission and the reception of the
wave is directly related to the distance between the source and the reflector. The
advantage of ultrasound is that it can travel through water smooth tissue. Addi-
tionally, ultrasound is not harmful at the levels of energy used for the generation
of the image. A standard configuration of IVUS acquisition images consists of
three components. Figure 1.3 shows a scheme of a catheter with a miniaturized
piezoelectric transducer, the pull-back unit, and the console for reconstructing
the images. IVUS catheter has a rank of measures that oscillates between 2.9
and 3.5 F (0.96-1.17 mm) in diameter. The quality of the image depends on the
operation frequency, which is of the order of 20-50 MHz; the lateral resolution
is approximately of the order of 113
µ
m and the axial resolution is of the order
of 80
µ
m [8]. The IVUS images acquisition process is initiated when the catheter
is manually (guided by the angiography) inserted within the artery (Fig. 1.3(a)).
The catheter pull-back is made at linear constant velocity (usually 0.5 mm/sec)
