Foundations of Medical Imaging and Signal Recording - Biomedical Signal Analysis: Contemporary Methods and Applications - page 25

Transducer

Motion

x

Pulse

Patient

z

Figure 1.13
A-mode display.

Tabl e 1 . 4
Acoustical properties of some materials and biological tissues .
Medium

Speed of sound (m/sec) Impedance Attenuation

(10 6 kg/ m 2 s) (dB/cm at 1MHZ)

Air 344 0.0004 12

Water 1480 1.48 0.0025

Fat 1410 1.38 0.63

Muscle 1566 1.70 1.2-3.3

Liver 1540 1.65 0.94

Bone 4080 7.80 20.0

1.3 Computer-Aided Diagnosis (CAD) Systems

The important advances in computer vision, paired with artificial intel-
ligence techniques and data mining, have facilitated the development of
automatic medical image analysis and interpretation. Computer-aided
diagnosis (CAD) systems are the result of these research endeavors and
provide a parallel second opinion in order to assist clinicians in detecting
abnormalities, predicting the diseases progress, and obtaining a differ-
ential diagnosis of lesions.
Modern CAD systems are becoming very sophisticated tools with a
user-friendly graphical interface supporting the interactions with clini-
cians during the diagnostic process. They have a multilayer architecture
with many modules, such as image processing, databases, and a graph-
ical interface.