Biomedical Engineering Reference
In-Depth Information
developed for special applications. Imaging and image-
processing methods provided the information-enhancing
possibility for physicians.
Ultrasound
In 1880, Madame Maria Sklodowska Curie and her
husband Pierre discovered radium and subsequently re-
ceived the Nobel Prize. Pierre's brother Jacques discov-
ered the piezoelectric effect. When high-frequency
electric fields are imposed on a piezoelectric material,
mechanical vibration results. Because the frequencies of
these vibrations are above the audible frequency domain,
the vibrations produced are termed ''ultrasound.''
Mulwert and Voss reported the first ultrasound therapy
intervention in 1928 when they tried to cure certain
deafness with ultrasound irradiation. Pohlmann, in 1939,
made the first ultrasound therapy equipment for treating
humans. In 1942, K. Tr. Dussik was the first to attempt to
apply ultrasound for diagnostics. After World War II,
ultrasound was used in different fields of medicine. The
one-dimensional method (A-scan) was followed by the
two-dimensional method (B-scan). Essentially, these are
imaging methods with which place and form of tissues
and organs can be examined.
By the application of the Doppler effect, ultrasound
was expanded to dynamic measurement areas. Reflection
of ultrasound from certain moving parts of the body
makes the measurement of radial velocity of the
reflecting surface possible. This phenomenon is applied,
for instance, in measurement of the blood flow velocity
and in the examination of fetal heart movements.
Considerably higher power must be applied in the
case of therapy. Accordingly, the problem of regulating
and making accurate measurements of ultrasound dose
and energy had to be solved. Today, medical application
of ultrasound is expanding rapidly, and equipment with
new features appears on the market continually. As
a result, quantity and diversity of knowledge required for
the application of ultrasound is growing.
CT and MRI
In the field of imaging, the computer tomograph (con-
ceived by William Oldendorf and developed by Godfrey
Hounsfield and Allen Cormack) brought revolutionary
change. The first successful clinical experiments oc-
curred in 1972. The Nobel Prize was bestowed upon the
two inventors in 1979, and Godfrey Hounsfield was
knighted in 1981. The basic idea of computer tomogra-
phy went beyond X-ray imaging. The principle is also
becoming important in fields where the source is non-
ionizing radiation.
The basic phenomenon of magnetic resonance imaging
was first observed in 1946. Certain atomic particles in
strong magnetic fields absorb very high-frequency elec-
tromagnetic waves selectively. Particularly those nuclei in
which at least one proton or one neutron is unpaired
show this phenomenon. This absorption can be measured
and evaluated. In the human body, water and lipid (fat)
molecules, which contain hydrogen, show the effect in
measurable magnitude. This noninvasive, relatively
hazard-free diagnostic method is based on this selective
absorption phenomenon. The first MRI equipment was
put on the market during the early 1980s. Since then, its
application has become broad including, among others,
the study of the brain, breast, heart, kidneys, liver, pan-
creas, and spleen.
Nuclear medicine
The use of radioactive isotopes as tracers by George C.
de Hevesy in 1912 was a great epoch-making discovery
for which Hevesy was recognized with the Nobel Prize in
1943. Wide-ranging application of radioactive tracers
became possible after World War II. Radioactive isotopes
came to the market after the 1950s. Around this time,
development of the equipment necessary for measure-
ments was completed as well. Importance of manmade
scintillation crystals was extraordinary. These crystals
make possible the detection, counting, and measurement
of the radiation emitted from disintegrating nuclei. The
development of synthetic crystals, the electron multi-
plier, and spectrum analyzers altogether resulted in the
general application of nuclear-measuring technique in
health care. In the following decades, the evolution of
imaging and image-processing technology further broad-
ened the field of nuclear measuring techniques. The in-
troduction of the gamma camera made possible the
imaging of larger parts of the body.
Microscope and endoscope
Most likely, Zacharis Jansen, a Dutch optician, discov-
ered the compound microscope in 1590. Its general use
gave enormous impetus to the development of medical
sciences. With its help, otherwise invisible elements of
the body could be studied. Since this discovery, many
varieties of microscopes have been developed. At the far
end of the spectrum are sophisticated devices, such as the
electron microscope and the atomic-force microscope.
For centuries, physicians wanted to directly visualize
the inner parts of the functioning body. Various endo-
scopes were developed to assist in achieving this goal.
The major improvement in endoscopes started with the
invention of Bozzini, a physician in Frankfurt. Bozzini
succeeded in introducing a beam of light into a hollow
organ and directing the reflected light to the eye of the
