BIOLOGY PROJECT.

TOPIC: SONOGRAPHY.
 Medical Ultrasound.

Medical ultrasound (also known as diagnostic sonography or ultrasonography) is

a diagnostic imaging technique based on the application of ultrasound. It is used to
create an image of internal body structures such as tendons, muscles, joints, blood
vessels, and internal organs. Its aim is often to find a source of a disease or to
exclude pathology. The practice of examining pregnant women using ultrasound is
called obstetric ultrasound, and was an early development and application of clinical
ultrasonography.

Ultrasound refers to sound waves with frequencies which are higher than those audible
to humans (>20,000 Hz). Ultrasonic images, also known as sonograms, are made by
sending pulses of ultrasound into tissue using a probe. The ultrasound pulses echo off
tissues with different reflection properties and are recorded and displayed as an image.

Many different types of images can be formed. The commonest is a B-mode image
(Brightness), which displays the acoustic impedance of a two-dimensional cross-section
of tissue. Other types can display blood flow, motion of tissue over time, the location of
blood, the presence of specific molecules, the stiffness of tissue, or the anatomy of a
three-dimensional region.

Sonographer doing echocardiography on a child.

 1.SONOGRAPHY BY ORGAN OR SYSTEM:-

Sonography (ultrasonography) is widely used in medicine. It

is possible to perform both diagnosis and therapeutic
procedures, using ultrasound to guide interventional
procedures such as biopsies or drainage of fluid
collections. Sonographers are medical professionals who
perform scans which are then traditionally interpreted by
radiologists, physicians who specialize in the application and
interpretation of a wide variety of medical imaging
modalities, or by cardiologists in the case of cardiac
ultrasonography (echocardiography). Increasingly, clinicians
(physicians and other healthcare professionals who provide
direct patient care) are using ultrasound in office and
hospital practice (Point of Care Ultrasound).
Ultrasonography is used for:
1. Anesthesiology
2. Angiology (vascular)
3. Cardiology (heart)
4. Gastroenterology/Colorectal surgery
5. Gynecology and obstetrics
6. Hemodynamics (blood circulation)
7. Otolaryngology (head and neck)
8. Ophthalmology (eyes)
9. Pulmonology (lungs)
10. Urology (urinary)
11. Musculoskeletal
12. Nephrology (kidneys)
 FROM SOUND TO IMAGE:
The creation of an image from sound is done in three steps – producing a sound wave,
receiving echoes, and interpreting those echoes.

1.Producing a sound wave.

A sound wave is typically produced by a piezoelectric transducer encased in a plastic housing.
Strong, short electrical pulses from the ultrasound machine drive the transducer at the desired
frequency. the sound is focused either by the shape of the transducer, a lens in front of the
transducer, or a complex set of control pulses from the ultrasound scanner, in the
(beamforming) technique. This focusing produces an arc-shaped sound wave from the face of
the transducer. The wave travels into the body and comes into focus at a desired depth.

Materials on the face of the transducer enable the sound to be transmitted efficiently into the
body (often a rubbery coating, a form of impedance matching). In addition, a water-based gel is
placed between the patient's skin and the probe.
The sound wave is partially reflected from the layers between different tissues or scattered from
smaller structures. Specifically, sound is reflected anywhere where there are acoustic
impedance changes in the body: e.g. blood cells in blood plasma, small structures in organs,
etc. Some of the reflections return to the transducer.
2.Receiving the echoes.
The return of the sound wave to the transducer results in the same process as sending the
sound wave, except in reverse. The returned sound wave vibrates the transducer and the
transducer turns the vibrations into electrical pulses that travel to the ultrasonic scanner where
they are processed and transformed into a digital image.

3.Forming the image.

To make an image, the ultrasound scanner must determine two things from each received echo:

1. How long it took the echo to be received from when the sound was transmitted.
2. How strong the echo was.
Once the ultrasonic scanner determines these two things, it can locate which pixel in the image to
light up and to what intensity.
Transforming the received signal into a digital image may be explained by using a blank spreadsheet as
an analogy. First picture a long, flat transducer at the top of the sheet. Send pulses down the 'columns' of
the spreadsheet (A, B, C, etc.). Listen at each column for any return echoes. When an echo is heard,
note how long it took for the echo to return. The longer the wait, the deeper the row (1,2,3, etc.). The
strength of the echo determines the brightness setting for that cell (white for a strong echo, black for a
weak echo, and varying shades of grey for everything in between.) When all the echoes are recorded on
the sheet, we have a grayscale image. Images from the ultrasound scanner are transferred and displayed
using the DICOM standard. Normally, very little post processing is applied to ultrasound images.
 SOUND IN THE BODY.

Ultrasonography (sonography) uses a probe containing multiple acoustic transducers to send

pulses of sound into a material. Whenever a sound wave encounters a material with a different
density (acoustical impedance), part of the sound wave is reflected back to the probe and is
detected as an echo. The time it takes for the echo to travel back to the probe is measured and
used to calculate the depth of the tissue interface causing the echo. The greater the difference
between acoustic impedances, the larger the echo is. If the pulse hits gases or solids, the
density difference is so great that most of the acoustic energy is reflected and it becomes
impossible to see deeper.
The frequencies used for medical imaging are generally in the range of 1 to 18 MHz. Higher
frequencies have a correspondingly smaller wavelength, and can be used to make sonograms
with smaller details. However, the attenuation of the sound wave is increased at higher
frequencies, so in order to have better penetration of deeper tissues, a lower frequency (3–
5 MHz) is used.
To generate a 2D-image, the ultrasonic beam is swept. A transducer may be swept
mechanically by rotating or swinging. Or a 1D phased array transducer may be used to sweep
the beam electronically. The received data is processed and used to construct the image. The
image is then a 2D representation of the slice into the body.
3D images can be generated by acquiring a series of adjacent 2D images. Commonly a
specialised probe that mechanically scans a conventional 2D-image transducer is used.
However, since the mechanical scanning is slow, it is difficult to make 3D images of moving
tissues. Recently, 2D phased array transducers that can sweep the beam in 3D have been
developed. These can image faster and can even be used to make live 3D images of a beating
heart.
Doppler ultrasonography is used to study blood flow and muscle motion. The different detected
speeds are represented in color for ease of interpretation, for example leaky heart valves: the
leak shows up as a flash of unique color. Colors may alternatively be used to represent the
amplitudes of the received echoes.

LINEAR ARRAY TRANSDUCER.

 Modes.
Several modes of ultrasound are used in medical imaging.[20][21] These are:

 A-mode: A-mode (amplitude mode) is the simplest type of ultrasound. A single transducer
scans a line through the body with the echoes plotted on screen as a function of
depth. Therapeutic ultrasound aimed at a specific tumor or calculus is also A-mode, to allow
for pinpoint accurate focus of the destructive wave energy.[22]
 B-mode or 2D mode: In B-mode (brightness mode) ultrasound, a linear array of
transducers simultaneously scans a plane through the body that can be viewed as a two-
dimensional image on screen. More commonly known as 2D mode now.
 C-mode: A C-mode image is formed in a plane normal to a B-mode image. A gate that
selects data from a specific depth from an A-mode line is used; then the transducer is
moved in the 2D plane to sample the entire region at this fixed depth. When the transducer
traverses the area in a spiral, an area of 100 cm2 can be scanned in around 10 seconds.[21]
 M-mode: In M-mode (motion mode) ultrasound, pulses are emitted in quick succession –
each time, either an A-mode or B-mode image is taken. Over time, this is analogous to
recording a video in ultrasound. As the organ boundaries that produce reflections move
relative to the probe, this can be used to determine the velocity of specific organ structures.
 Pulse inversion mode: In this mode, two successive pulses with opposite sign are emitted
and then subtracted from each other. This implies that any linearly responding constituent
will disappear while gases with non-linear compressibility stand out. Pulse inversion may
also be used in a similar manner as in Harmonic mode; see below:
 Harmonic mode: In this mode a deep penetrating fundamental frequency is emitted into the
body and a harmonic overtone is detected. This way noise and artifacts due to reverberation
and aberration are greatly reduced. Some also believe that penetration depth can be gained
with improved lateral resolution; however, this is not well documented.
 Expansions.

An additional expansion or additional technique of ultrasound is biplanar ultrasound, in which the

probe has two 2D planes that are perpendicular to each other, providing more efficient localization
and detection.[25] Furthermore, an omniplane probe is one that can rotate 180° to obtain multiple
images.[25] In 3D ultrasound, many 2D planes are digitally added together to create a 3-dimensional
image of the object.

Doppler ultrasonography.

Duplex scan of the common carotid artery

Doppler ultrasonography employs the Doppler effect to assess whether structures (usually
blood)[26] are moving towards or away from the probe, and its relative velocity. By calculating the
frequency shift of a particular sample volume, for example flow in an artery or a jet of blood flow
over a heart valve, its speed and direction can be determined and visualized. Color Doppler is
the measurement of velocity by color scale. Color Doppler images are generally combined with
grayscale (B-mode) images to display duplex ultrasonography images.
Contrast ultrasonography (ultrasound contrast imaging)[edit]
A contrast medium for medical ultrasonography is a formulation of encapsulated gaseous
microbubbles[29] to increase echogenicity of blood, discovered by Dr Raymond Gramiak in
1968[30] and named contrast-enhanced ultrasound. This contrast medical imaging modality is
clinically used throughout the world,[31] in particular for echocardiography in the United States and
for ultrasound radiology in Europe and Asia.
Molecular ultrasonography (ultrasound molecular imaging)[edit]
The future of contrast ultrasonography is in molecular imaging with potential clinical applications
expected in cancer screening to detect malignant tumors at their earliest stage of appearance.
Molecular ultrasonography (or ultrasound molecular imaging) uses targeted microbubbles originally
designed by Dr Alexander Klibanov in 1997;[44][45] such targeted microbubbles specifically bind or
adhere to tumoral microvessels by targeting biomolecular cancer expression (overexpression of
certain biomolecules occurs during neo-angiogenesis[46][47] or inflammation[48] processes in malignant
tumors). As a result, a few minutes after their injection in blood circulation, the targeted microbubbles
accumulate in the malignant tumor; facilitating its localization in a unique ultrasound contrast image.
In 2013, the very first exploratory clinical trial in humans for prostate cancer was completed
at Amsterdam in the Netherlands by Dr Hessel Wijkstra.[49]

Elastography (ultrasound elasticity imaging)[edit]

Ultrasound is also used for elastography, which is a relatively new imaging modality that maps the
elastic properties of soft tissue.[54][55] This modality emerged in the last two decades. Elastography is
useful in medical diagnoses as it can discern healthy from unhealthy tissue for specific
organs/growths. For example, cancerous tumors will often be harder than the surrounding tissue,
and diseased livers are stiffer than healthy ones.[54][55][56][57]
There are many ultrasound elastography techniques.[55]

Compression ultrasonography[edit]
Compression ultrasonography is when the probe is pressed against the skin. This can bring the
target structure closer to the probe, increasing spatial resolution of it. Comparison of the shape of
the target structure before and after compression can aid in diagnosis.It used in ultrasonography of
deep venous thrombosis, wherein absence of vein compressibility is a strong indicator of
thrombosis.

A normal appendix without and with compression. Absence of comprehensibility indicates appendicitis.[61]


 Attributes.

As with all imaging modalities, ultrasonography has its list of positive and negative attributes.

Strengths

 It images muscle, soft tissue, and bone surfaces very well and is particularly useful for
delineating the interfaces between solid and fluid-filled spaces.
 It renders "live" images, where the operator can dynamically select the most useful section for
diagnosing and documenting changes, often enabling rapid diagnoses. Live images also allow
for ultrasound-guided biopsies or injections, which can be cumbersome with other imaging
modalities.
 It shows the structure of organs.
 It has no known long-term side effects and rarely causes any discomfort to the patient.
 Equipment is widely available and comparatively flexible.
 Small, easily carried scanners are available; examinations can be performed at the bedside.
 Relatively inexpensive compared to other modes of investigation, such as computed X-ray
tomography, DEXA or magnetic resonance imaging.
 Spatial resolution is better in high frequency ultrasound transducers than it is in most other
imaging modalities.
 Through the use of an ultrasound research interface, an ultrasound device can offer a relatively
inexpensive, real-time, and flexible method for capturing data required for special research
purposes for tissue characterization and development of new image processing techniques

Weaknesses

 Sonographic devices have trouble penetrating bone. For example, sonography of the adult brain
is currently very limited.
 Sonography performs very poorly when there is a gas between the transducer and the organ of
interest, due to the extreme differences in acoustic impedance. For example, overlying gas in
the gastrointestinal tract often makes ultrasound scanning of the pancreas difficult. Lung imaging
however can be useful in demarcating pleural effusions, detecting heart failure, and detecting
pneumonia.[62]
 Even in the absence of bone or air, the depth penetration of ultrasound may be limited
depending on the frequency of imaging. Consequently, there might be difficulties imaging
structures deep in the body, especially in obese patients.
 Physique has a large influence on image quality. Image quality and accuracy of diagnosis is
limited with obese patients, overlying subcutaneous fat attenuates the sound beam and a lower
frequency transducer is required (with lower resolution)
 The method is operator-dependent. A high level of skill and experience is needed to acquire
good-quality images and make accurate diagnoses.
 There is no scout image as there is with CT and MRI. Once an image has been acquired there is
no exact way to tell which part of the body was imaged.
 Risks and side-effects.

Ultrasonography is generally considered safe imaging,[63] with the World Health Organizations
saying:[64]
"Diagnostic ultrasound is recognized as a safe, effective, and highly flexible imaging modality
capable of providing clinically relevant information about most parts of the body in a rapid
and cost-effective fashion".
Diagnostic ultrasound studies of the fetus are generally considered to be safe during pregnancy.
This diagnostic procedure should be performed only when there is a valid medical indication,
and the lowest possible ultrasonic exposure setting should be used to gain the necessary
diagnostic information under the "as low as reasonably practicable" or ALARP principle.
However, medical ultrasonography should not be performed without a medical indication to
perform it. To do otherwise would be to perform unnecessary health care to patients, which bring
unwarranted costs and may lead to other testing. Overuse of ultrasonography is sometimes as
routine as screening for deep vein thrombosis after orthopedic surgeries in patients who are not
at heightened risk for having that condition.[65]
Similarly, although there is no evidence ultrasound could be harmful for the fetus, medical
authorities typically strongly discourage the promotion, selling, or leasing of ultrasound
equipment for making "keepsake fetal videos".[5][66]

Studies on the safety of ultrasound.

 A meta-analysis of several ultrasonography studies published in 2000 found no statistically

significant harmful effects from ultrasonography, but mentioned that there was a lack of data on
long-term substantive outcomes such as neurodevelopment.[67]
 A study at the Yale School of Medicine published in 2006 found a small but significant
correlation between prolonged and frequent use of ultrasound and abnormal neuronal migration
in mice.[68]

 A study performed in Sweden in 2001[69] has shown that subtle effects of neurological damage
linked to ultrasound were implicated by an increased incidence in left-handedness in boys (a
marker for brain problems when not hereditary) and speech delays. The above findings,
however, were not confirmed in a later follow-up study.[72]
 A later study, however, performed on a larger sample of 8865 children, has established a
statistically significant, albeit weak association of ultrasonography exposure and being non-right
handed later in life.[73]
ULTRASOUND IMAGE OF FOETUS.

ULTRASOUND IMAGE OF FETAL BRAIN.

 BIBLIOGRAPHY.
Brown, Sanford, 2009, 'What is sonography, and how is it being used in the heath care field?'.
Retrieved 4th, 2015 from, http://www.sanfordbrown.edu/student-life/blog/february-2009/how-
sonography-is-being-used-in-field

About the professions of Sonography', 2013. Retrieved September 1st 2015 from,
http://www.muhlenbergschools.org/prospective_ms.asp

Society of Diagnostic Medical Sonography, 2010, 'Diagnostic Medical Sonography'. Retrieved

September 4th, 2015 from,
https://www.sdms.org/career/careerbrochure/PDF/brochuredesktop.pdf