LESSON 4
MEDICAL ULTRASONOGRAPHY
MEDICAL THERMOGRAPHY
RADIONUCLIDE IMAGING
MEDICAL ULTRASONOGRAPHY
Medical sonography (ultrasonography) is an ultrasound-based diagnostic
imaging technique used to visualize muscles and internal organs, their size,
structures and possible pathologies or lesions. In physics the term "ultrasound"
applies to all acoustic energy with a frequency above human hearing (20,000 hertz
or 20 kilohertz). Typical diagnostic sonographic scanners operate in the frequency
range of 2 to 18 megahertz, hundreds of times greater than the limit of human
hearing.
Sonography is effective for imaging soft tissues of the body. Superficial
structures such as muscles, tendons, testes, breast and the neonatal brain are
imaged at a higher wave frequency (7-18 MHz), which provides better axial and
lateral resolution. Deeper structures such as liver and kidney are imaged at a lower
frequency 1-6 MHz with lower axial and lateral resolution but greater penetration.i
In diagnostic ultrasound examinations, very high freguency sound is directed
into the body from a transducer , placed in contact with the skin. In order to make
good acoustic contact, the skin is smeared with a jelly-like substance.
The creation of an image from sound is done in three steps - producing a
sound wave, receiving echoes, and interpreting those echoes. As the sound travels
through the body, it is reflected by the tissue interfaces to produce echoes. which
are picked up by the same transducer and converted into an electrical signal.
Since air, bones and other heavily calcified materials absorb nearly all the
ultrasound beam, ultrasound plays little part in the diagnosis of lung and bone
diseases.
, It images muscle and soft tissue very well and is particularly useful for
delineating the interfaces between solid and fluid-filled spaces.
It shows the structure of organs
It is noninvasive, painless, no radiation
Diagnostic US studies of the fetus are generally considered to be safe during
pregnancy.
A MODE- is the simplest type of US. A single transducer scans a line
through the body with the echoes plotted on screen as a function of depth.
This mode is used in ophthalmology and neurology.
B MODE – in this mode of US, a linear array of transducers
simultaneously scans a plane through the body that can be viewed as a
two dimensional image on screen.
M MODE – M stands from motion. In M mode a rapid sequence of B
mode scans whose images follow each other in sequence on screen
enables doctors to see and measure range of motion.
DOPPLER MODE – Dopplerography is to the doppler effect based
ultrasound method.
Sound reflected from a mobile structure shows a variation in frequency
which corresponds to the speed of movement of the structure. This shift
in frequency, which can be converted to an audible signal, is the principle
underlying the Doppler probe.
This method can also be exploited to image blood flowing through
the heart or blood vessels. If blood is flowing towards the transducer the
received signal is of higher frequency, than the transmitted frequency. At
the dopplerography method blood circulation to the detector appears as
red, to reverse blue. The direction of blood flow can readily be
determined and flow towards the transducer is by convention colored red,
where as blue indicates flow away from the transducer.
Doppler studies are used to detect venous thrombosis, arterial stenosis
and occlusion, particularly un the carotid arteries. In the abdomen
Doppler techniques can determine whether a structure is a blood vessel
MEDICAL ULTRASONOGRAPHY
MEDICAL THERMOGRAPHY
RADIONUCLIDE IMAGING
MEDICAL ULTRASONOGRAPHY
Medical sonography (ultrasonography) is an ultrasound-based diagnostic
imaging technique used to visualize muscles and internal organs, their size,
structures and possible pathologies or lesions. In physics the term "ultrasound"
applies to all acoustic energy with a frequency above human hearing (20,000 hertz
or 20 kilohertz). Typical diagnostic sonographic scanners operate in the frequency
range of 2 to 18 megahertz, hundreds of times greater than the limit of human
hearing.
Sonography is effective for imaging soft tissues of the body. Superficial
structures such as muscles, tendons, testes, breast and the neonatal brain are
imaged at a higher wave frequency (7-18 MHz), which provides better axial and
lateral resolution. Deeper structures such as liver and kidney are imaged at a lower
frequency 1-6 MHz with lower axial and lateral resolution but greater penetration.i
In diagnostic ultrasound examinations, very high freguency sound is directed
into the body from a transducer , placed in contact with the skin. In order to make
good acoustic contact, the skin is smeared with a jelly-like substance.
The creation of an image from sound is done in three steps - producing a
sound wave, receiving echoes, and interpreting those echoes. As the sound travels
through the body, it is reflected by the tissue interfaces to produce echoes. which
are picked up by the same transducer and converted into an electrical signal.
Since air, bones and other heavily calcified materials absorb nearly all the
ultrasound beam, ultrasound plays little part in the diagnosis of lung and bone
diseases.
, It images muscle and soft tissue very well and is particularly useful for
delineating the interfaces between solid and fluid-filled spaces.
It shows the structure of organs
It is noninvasive, painless, no radiation
Diagnostic US studies of the fetus are generally considered to be safe during
pregnancy.
A MODE- is the simplest type of US. A single transducer scans a line
through the body with the echoes plotted on screen as a function of depth.
This mode is used in ophthalmology and neurology.
B MODE – in this mode of US, a linear array of transducers
simultaneously scans a plane through the body that can be viewed as a
two dimensional image on screen.
M MODE – M stands from motion. In M mode a rapid sequence of B
mode scans whose images follow each other in sequence on screen
enables doctors to see and measure range of motion.
DOPPLER MODE – Dopplerography is to the doppler effect based
ultrasound method.
Sound reflected from a mobile structure shows a variation in frequency
which corresponds to the speed of movement of the structure. This shift
in frequency, which can be converted to an audible signal, is the principle
underlying the Doppler probe.
This method can also be exploited to image blood flowing through
the heart or blood vessels. If blood is flowing towards the transducer the
received signal is of higher frequency, than the transmitted frequency. At
the dopplerography method blood circulation to the detector appears as
red, to reverse blue. The direction of blood flow can readily be
determined and flow towards the transducer is by convention colored red,
where as blue indicates flow away from the transducer.
Doppler studies are used to detect venous thrombosis, arterial stenosis
and occlusion, particularly un the carotid arteries. In the abdomen
Doppler techniques can determine whether a structure is a blood vessel
