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Biomedical Signal and Image Processing
16.10 APPLICATIONS OF ULTRASOUND IMAGING
Ultrasound imaging is often used to provide the bearings for invasive and noninvasive surgery. One of the most well-known applications of ultrasound imaging is
monitoring the development of a baby (fetus) in the womb. The same system is sometimes used to determine the sex of the fetus.
A major application of Doppler ultrasound is the study of the heart and human
carotid artery disease wherein imaging and frequency shift are combined to produce
images of artery and ventricle lumens. As explained earlier, the frequency shift data
are used to color code the image, showing direction of flow. Analogous to optical
Doppler imaging, flow toward the ultrasound probe is represented in blue due to the
shift toward a higher frequency, and flow away from the probe is represented in red
(e.g., carotid arteries in red and veins in blue). Obstructions to blood flow are readily
evaluated by this method using handheld scanning devices.
Some ultrasound imaging devices provide a virtual reality images on a visor display for image-guided surgeries such as laparoscopic surgery. The virtual reality
image can be linked to the position and direction of the surgeon’s head to correlate
the previously recorded ultrasound images to the corresponding position the operator
is looking.
Three-dimensional ultrasound images are sometimes used in vascular surgery.
By placing a miniature ultrasound probe in a catheter, the probe can be inserted into
the lumen of blood vessels, in particular, the coronary arteries. When a 3-D image
of the lumen of the artery can be attained, surgeons obtain more preintervention
information on the extent of stenosis, or blockage, and these data could affect the
type of intervention chosen. The process also allows pre- and postintervention characterization of vessels to show the effectiveness of the chosen intervention.
Techniques that allow real-time guidance of the needle/fiber into the tissue using
ultrasound imaging are currently used for some medical diagnostics applications.
In addition to imaging heart valves and blood vessels, ultrasound is the most convenient and inexpensive method for medical evaluations such as gallbladder stones.
Ultrasound imaging is also being used for monitoring therapy methods, such as
hyperthermia, cryosurgery, drug injections, and as a guide during biopsies and catheter placements.
16.11 PROCESSING AND FEATURE EXTRACTION
OF ULTRASONIC IMAGES
Almost all image analysis techniques described in Chapters 4 and 5 are used to
trace the outline of organs and other anatomical features and extract features such
as volume of the objects. Further image signal and processing can yield tissue discrimination based on the measured frequency spectrum and the localization of these
frequency characteristics in the imaging field.
Since there are no definite regularities in the acoustic signals collected from the
various impedance discontinuities at the interface of different organ media, there
is no clear spatial frequency information on the noise. However, there is a certain
degree of omnipresent noise with undetermined frequency content. This noise will
Biomedical Signal and Image Processing
16.10 APPLICATIONS OF ULTRASOUND IMAGING
Ultrasound imaging is often used to provide the bearings for invasive and noninvasive surgery. One of the most well-known applications of ultrasound imaging is
monitoring the development of a baby (fetus) in the womb. The same system is sometimes used to determine the sex of the fetus.
A major application of Doppler ultrasound is the study of the heart and human
carotid artery disease wherein imaging and frequency shift are combined to produce
images of artery and ventricle lumens. As explained earlier, the frequency shift data
are used to color code the image, showing direction of flow. Analogous to optical
Doppler imaging, flow toward the ultrasound probe is represented in blue due to the
shift toward a higher frequency, and flow away from the probe is represented in red
(e.g., carotid arteries in red and veins in blue). Obstructions to blood flow are readily
evaluated by this method using handheld scanning devices.
Some ultrasound imaging devices provide a virtual reality images on a visor display for image-guided surgeries such as laparoscopic surgery. The virtual reality
image can be linked to the position and direction of the surgeon’s head to correlate
the previously recorded ultrasound images to the corresponding position the operator
is looking.
Three-dimensional ultrasound images are sometimes used in vascular surgery.
By placing a miniature ultrasound probe in a catheter, the probe can be inserted into
the lumen of blood vessels, in particular, the coronary arteries. When a 3-D image
of the lumen of the artery can be attained, surgeons obtain more preintervention
information on the extent of stenosis, or blockage, and these data could affect the
type of intervention chosen. The process also allows pre- and postintervention characterization of vessels to show the effectiveness of the chosen intervention.
Techniques that allow real-time guidance of the needle/fiber into the tissue using
ultrasound imaging are currently used for some medical diagnostics applications.
In addition to imaging heart valves and blood vessels, ultrasound is the most convenient and inexpensive method for medical evaluations such as gallbladder stones.
Ultrasound imaging is also being used for monitoring therapy methods, such as
hyperthermia, cryosurgery, drug injections, and as a guide during biopsies and catheter placements.
16.11 PROCESSING AND FEATURE EXTRACTION
OF ULTRASONIC IMAGES
Almost all image analysis techniques described in Chapters 4 and 5 are used to
trace the outline of organs and other anatomical features and extract features such
as volume of the objects. Further image signal and processing can yield tissue discrimination based on the measured frequency spectrum and the localization of these
frequency characteristics in the imaging field.
Since there are no definite regularities in the acoustic signals collected from the
various impedance discontinuities at the interface of different organ media, there
is no clear spatial frequency information on the noise. However, there is a certain
degree of omnipresent noise with undetermined frequency content. This noise will