1. Faculty of engineering, Cairo university.
Biomedical engineering Dept.
Ultrasound applications in
biomedical engineering.
Presented by: Zeyad Khaled Samir.
Presented to: Dr. Mohammed Hesham.
Section: 1
BN: 36
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Introduction.
IN the past few years, Ultrasound has payed an important role in
biomedical engineering, and has helped propel biotechnology to new
heights. This report discusses the uses and applications of ultrasound in
the medical field.
What are ultrasonic waves?
Most medical applications of ultrasound are based on the properties of
longitudinal waves in the frequency range 1-15 MHz. Ultrasonic waves
travel at similar velocities (about 1500 m s −1) in most biological
tissues, and are absorbed at a rate of about 1 dB cm −1 MHz −1.
Absorption occurs chiefly due to relaxation processes. It leads to
thermal effects in biological systems. Mechanical effects, such as
streaming and cavitations, are also important in certain situations,
particularly at low frequencies. Highly focused ultrasound is used in
neurosurgery; it is the only method for producing trackless damage
deep in the brain. Diagnostic imaging using ultrasound finds
applications in all tissues. Although u1trasound has been used in
medicine since the 1930's, it is only recently that these techniques have
been widely used and their potential fully recognized. Medical
ultrasonics is now in a period of rapid growth and is on the verge of
making a significant impact on clinical medicine. This field offers an
open proving ground to many technologies developed for other
applications, gives inspiration to the development of new technological
advances, and provides a host of challenging and important problems
that are unique to medicine and biology. The future of ultrasound in
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medicine depends upon talented people from medicine and the
physical sciences working in close collaboration and upon the
emergence of a new breed of research scientist trained in both
medicine and engineering and dedicated not to the technology of
destruction but rather to the preservation of life and humanity. The
object of this paper is to present a review of the principles of medical
ultrasonics and an introduction to a variety of its applications.
Imaging.
The potential for ultrasonic imaging of objects, with a 3 GHZ sound
wave producing resolution comparable to an optical image, was
recognized by Sokolov in 1939, but techniques of the time produced
relatively low-contrast images with poor sensitivity. Ultrasonic imaging
uses frequencies of 2 megahertz and higher; the shorter wavelength
allows resolution of small internal details in structures and tissues. The
power density is generally less than 1 watt per square centimetre to
avoid heating and cavitation effects in the object under
examination. High and ultra-high ultrasound waves are used in acoustic
microscopy, with frequencies up to 4 gigahertz. Ultrasonic imaging
applications include industrial nondestructive testing, quality control
and medical uses.
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Ultrasound image of a fetus at 12 weeks.
Medical sonography (ultrasonography) is an ultrasound-based
diagnostic medical imaging technique used to visualize muscles,
tendons, and many internal organs to capture their size, structure and
any pathological lesions with real time tomographic images. Ultrasound
has been used by radiologists and sonographers to image the human
body for at least 50 years and has become a widely used diagnostic
tool. The technology is relatively inexpensive and portable, especially
when compared with other techniques, such as magnetic resonance
imaging (MRI) and computed tomography (CT). Ultrasound is also used
to visualize fetuses during routine and emergency prenatal care. Such
diagnostic applications used during pregnancy are referred to
as obstetric sonography. As currently applied in the medical field,
properly performed ultrasound poses no known risks to the
patient. Sonography does not use ionizing radiation, and the power
levels used for imaging are too low to cause adverse heating or
pressure effects in tissue. Although the long-term effects due to
ultrasound exposure at diagnostic intensity are still unknown, currently
most doctors feel that the benefits to patients outweigh the risks. The
ALARA (As Low As Reasonably Achievable) principle has been advocated
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for an ultrasound examination – that is, keeping the scanning time and
power settings as low as possible but consistent with diagnostic
imaging – and that by that principle nonmedical uses, which by
definition are not necessary, are actively discouraged.
Ultrasound is also increasingly being used in trauma and first aid cases,
with emergency ultrasound becoming a staple of most EMT response
teams. Furthermore, ultrasound is used in remote diagnosis cases
where teleconsultation is required, such as scientific experiments in
space or mobile sports team diagnosis.
According to RadiologyInfo, ultrasounds are useful in the detection
of pelvic abnormalities and can involve techniques known
as abdominal (transabdominal) ultrasound, rectal (transrectal)
ultrasound in men.
