ULTRASOUND MACHINEBY

DR/ DINA METWALY

ULTRASOUND MACHINE

A basic ultrasound machine has the following parts:

1. Transducer probe - probe that sends and receives the sound waves

2. Central processing unit (CPU) - computer that does all of the calculations and contains the electrical power supplies for itself and the transducer probe

3. Display - displays the image from the ultrasound data processed by the CPU

4. Keyboard/cursor - inputs data and takes measurements from the display

5. Disk storage device (hard, floppy, CD) - stores the acquired images

6. Printer - prints the image from the displayed data

ULTRASOUND TRANSDUCERS The transducer probe is the main part of the ultrasound machine. The transducer probe makes the sound waves and receives the

echoes. It is, so to speak, the mouth and ears of the ultrasound machine.

The transducer probe generates and receives sound waves using a principle called the piezoelectric (pressure electricity) effect. In the probe, there are one or more quartz crystals called piezoelectric crystals. When an electric current is applied to these crystals, they change shape rapidly. The rapid shape changes, or vibrations, of the crystals produce sound waves that travel outward. Conversely, when sound or pressure waves hit the crystals, they emit electrical currents. Therefore, the same crystals can be used to send and receive sound waves.

ULTRASOUND TRANSDUCERS Transducer probes come in many

shapes and sizes, The shape of the probe determines its field of view, and the frequency of emitted sound waves determines how deep the sound waves penetrate and the resolution of the image.

In addition to probes that can be moved across the surface of the body, some probes are designed to be inserted through various openings of the body (vagina, rectum, esophagus) so that they can get closer to the organ being examined (uterus, prostate gland, stomach); getting closer to the organ can allow for more detailed views.

SELECTION OF TRANSDUCER Superficial vessels and organs within 1 to 3cms depth and intra

operative imaging –

=7.5 to 15 Hz

Deeper structures in abdomen and pelvis within 12 to 15cms –

=2.25 to 3.5Hz

TRANSDUCER - PARTS A simple single-element, plane-

piston source transducer has major components including the Piezoelectric material, Sensor electrodes, Insulated layer, Backing block, Acoustic insulator Insulating cover, and Transducer housing.

ULTRASOUND CPC

1. The CPU is the brain of the ultrasound machine.

2. The CPU is basically a computer that contains the microprocessor, memory, amplifiers and power supplies for the microprocessor and transducer probe.

3. The CPU sends electrical currents to the transducer probe to emit sound waves, and also receives the electrical pulses from the probes that were created from the returning echoes.

4. The CPU does all of the calculations involved in processing the data. Once the raw data are processed, the CPU forms the image on the monitor.

5. The CPU can also store the processed data and/or image on disk.

ULTRASOUND TYPES Different Types of Ultrasound are present: The ultrasound that we have described so far presents a

two-dimensional image, or "slice," of a three-dimensional object (fetus, organ). Two other

types of ultras ound are currently in use, 3-D ultrasound imaging and Doppler ultrasound.

3D AND 4D ULTRASOUND 3D ultrasound - data set that contains a large number of 2D

planes. This volume data can be manipulated in different planes by

rotation. Dissected in any plane, to get multiplanar images . Special probes and software are necessary in order to perform

3D and 4D imaging. 4D ultrasound is also known as "Real-time 3D Ultrasound". The

3D datasets with their multiplanar reformations and renderings in real time, give us photographic quality images.

LIMITATIONS OF 3D US More heavy , requiring more user input Waiting for the 3D image to appear can be frustrating to

users Slow the image interpretation process, especially if

inexperienced, as the right algorithm needs to be chosen. The ability to obtain a good 3-D picture is very much

dependent on operator skill, the amount of liquor, fetus position and the degree of maternal obesity.

MODE USGUltrasound information can be displayed in several

ways. B-mode ((brightness mode))= gray-scale

1. This mode is most often used in diagnostic imaging; signals are displayed as a 2-dimensional anatomic image.

2. B-mode is commonly used to evaluate the developing fetus and to evaluate organs, including the liver, spleen, kidneys, thyroid gland, testes, breasts, and prostate gland.

3. B-mode ultrasonography is fast enough to show real-time motion, such as the motion of the beating heart or pulsating blood vessels. Real-time imaging provides anatomic and functional information.

A-mode (amplitude mode):

1. This display mode is the simplest; signals are recorded as spikes on a graph.

2. The vertical (Y) axis of the display shows the echo amplitude, and the horizontal (X) axis shows depth or distance into the patient.

3. This type of ultrasonography is used for ophthalmologic scanning.

M-mode(motion mode):

1. This mode is used to image moving structures;

2. signals reflected by the moving structures are converted into waves that are displayed continuously across a vertical axis.

3. M-mode is used primarily for assessment of fetal heartbeat and in cardiac imaging, most notably to evaluate valvular disorders.

Doppler:

1. This type of ultrasonography is used to assess blood flow.

2. Doppler ultrasonography uses the Doppler effect (alteration of sound frequency by reflection off a moving object). The moving objects are RBCs in blood.

3. Direction and velocity of blood flow can be determined by analyzing changes in the frequency of sound waves:› If a reflected sound wave is lower in frequency than the

transmitted sound wave, blood flow is away from the transducer.› If a reflected sound wave is higher in frequency than the

transmitted sound wave, blood flow is toward the transducer.› The magnitude of the change in frequency is proportional to blood

flow velocity.› Changes in frequency of the reflected sound waves are converted

into images showing blood flow direction and velocity.

For color Doppler ultrasonography:

1. color is superimposed on a gray-scale anatomic image.

2. The color indicates direction of blood flow. By convention, red indicates flow toward and blue indicates flow away from the transducer.

3. Doppler ultrasonography is also used to evaluate vascularity of tumors and organs, to evaluate heart function (e.g., as for echocardiography), to detect occlusion and stenosis of blood vessels, and to detect blood clots in blood vessels (e.g., in deep venous thrombosis).

ULTRASOUND INDICATIONS Ultrasound is not limited to diagnosis, but can also

be used in screening for disease and to aid in treatment of diseases or conditions.

1. Diagnostic uses

2. Therapeutic uses

3. Screening uses

DIAGNOSTIC USES Obstetrics & Gynecology:

1. measuring the size, number, sex& position of the fetus to determine the due date

2. checking the position of the placenta .

3. checking the fetus's growth rate by making many measurements over time

7. detecting ectopic pregnancy, the life-threatening situation in which the baby is implanted in the mother's Fallopian tubes instead of in the uterus

8. determining whether there is an appropriate amount of amniotic fluid cushioning the baby

9. seeing tumors of the ovary and breast

CARDIOLOGY (ECHOCARDIOGRAPHY)

1. seeing the inside of the heart to identify abnormal structures or functions

2. measuring blood flow through the heart and major blood vessels

3. Urology measuring blood flow through the kidney

4. seeing kidney stones

5. detecting prostate cancer early

Urology

SCREENING USES1. Ultrasound may be used to screen for blood vessel

diseases.

2. By measuring blood flow and blockage in the carotid arteries, the test can predict potential risk for future stroke.

3. Similarly, by measuring the diameter of the aorta in the abdomen, ultrasound can screen for aneurysm (abnormal dilatation) and the risk of rupture.

4. These tests may be indicated for an individual patient or they may be offered as a community wide health screening assessment.

THERAPEUTIC USES1. Ultrasound may be used to help physicians guide needles

into the body.

2. In situations where an intravenous line is required but it is difficult to find a vein, ultrasound guidance may be used to identify larger veins in the neck, chest wall, or groin.

3. Ultrasound may be used to guide a needle into a cavity that needs to be drained (for example, an abscess) or a mass that needs to be biopsied, where a small bit of tissue is removed for analysis.

BENEFITS VS RISKS Benefits1. Most ultrasound scanning is noninvasive (no needles or

injections).

2. Occasionally, an ultrasound exam may be temporarily uncomfortable, but it is almost never painful.

3. Ultrasound is widely available, easy-to-use and less expensive than other imaging methods.

4. Ultrasound imaging is extremely safe and does not use any ionizing radiation.

5. Ultrasound scanning gives a clear picture of soft tissues that do not show up well on x-ray images.

6. Ultrasound is the preferred imaging modality for the diagnosis and monitoring of pregnant women and their unborn babies.

7. Ultrasound provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies and fluid aspiration.

Risks For standard diagnostic ultrasound, there are no known harmful

effects on humans. But there is limitation of General Ultrasound Imaging

1. Ultrasound waves are disrupted by air or gas; therefore ultrasound is not an ideal imaging technique for air-filled bowel or organs obscured by the bowel. In most cases, barium exams, CT scanning, and MRI are the methods of choice in such a setting.

2. Large patients are more difficult to image by ultrasound because greater amounts of tissue attenuates (weakens) the sound waves as they pass deeper into the body.

3. Ultrasound has difficulty penetrating bone and, therefore, can only see the outer surface of bony structures and not what lies within (except in infants who have more cartilage in their skeletons than older children or adults).

4. For visualizing internal structure of bones or certain joints, other imaging modalities such as MRI are typically used.

ULTRASOUND PROCEDURE

PREPARATION In general, no preparation is needed for an ultrasound

examination; however, for certain examinations of the abdomen,

a period of fasting is useful or necessary. To avoid problems due to meteorism.

dietary restrictions (no gas-producing foods), premedication (antifoaming agents) are recommended. Special preparation is only necessary for certain

examinations

POSITIONING

The ultrasound examination is usually carried out with the patient in the supine position, it is often useful to turn the patient in an oblique position or to scan from the back in a prone position, e.g. When scanning the kidneys.

A COUPLING GEL is necessary to ensure good contact between the transducer

and the skin and to avoid artifacts caused by the presence of air between them.

The best coupling agents are

1. water-soluble gels, which are commercially available.

2. Water is suitable for very short examinations.

3. Disinfectant fluids can also be used for short coupling of the transducer during guided punctures.

4. Oil has the disadvantage of dissolving rubber or plastic parts of the transducer.

PRECAUTION

Be careful not to transmit infectious material from one patient to the next via the transducer or the coupling gel.

The transducer and any other parts that come into direct contact with the patient must be cleaned after each examination.

The minimum requirements are to wipe the transducer after each examination and to clean it with a suitable disinfectant every day and after the examination of any patient who may be infectious.

A suitable method for infectious patients, e.g. those infected with human immunodeficiency virus (HIV) and with open wounds or other skin lesions, is to slip a disposable glove over the transducer and to smear some jelly onto the active surface of the transducer.

ADJUSTMENT OF THE EQUIPMENT Most instruments have a standard setting for each

transducer and each body region. This standard can be adapted to the needs of each operator.

When starting with these standards, only slight adaptation to the individual patient is necessary.

The choice of frequency (and transducer) depends on the penetration depth needed. For examination of the abdomen, it may be useful to start with a lower frequency (curved array, 3.5 MHz) and to use a higher frequency if the region of interest is close to the transducer, e.g. the bowel.

Adaptation to the penetration depth needed: the whole screen should be used for the region of interest.

GUIDELINES FOR THE EXAMINATION1. Know the patient’s problem and medical history. An advantage of

ultrasound is that the patient’s doctor can carry out the examination

2. Make sure that the settings of the equipment and the orientation of the transducer are correct in relation to the image. This will avoid misinterpretations

3. complete examination of the whole body region, even if there is an obvious palpable mass or a localized point of pain.

4. Start with an anatomically constant area and move to the more variable area (e.g. from the liver to the region of the pancreas or the intestine).

5. Move the transducer in a slow constant pattern, while maintaining the defined scanning plane. Hold the transducer motionless when the patient moves, e.g. during respiration. It is possible to move a transducer in many directions by tilting it in the scanning plane and moving it perpendicularly, but with a combination of all these movements the less experienced operator will lose the orientation of the image.

6. Use anatomically constant, easily visualized structures for orientation (e.g. liver, aorta or fluid-filled bladder) and normal structures for comparison (e.g. right and left kidney or kidney and liver).

7. Examine each organ, structure or tumour in at least two planes. In this way, one can avoid missing small lesions or misinterpreting artifacts as real alterations.

8. Use palpation to displace fluid or gas from the bowel, to test the consistency of tumours and organs and to localize points of pain.

9. In clinically difficult situations or when the findings are doubtful, repeat the examination

10. a short time later. Such repeat examinations can be carried out even at the bedside. This is particularly useful with trauma patients and patients in intensive care.

DOCUMENTATION

As a rule, both a written report and pictorial documentation should be prepared for each ultrasound examination.

The written report should include:

1. a description of the problem that led to the examination;

2. a list of the organs (region) examined (generally, it is not necessary to describe normal findings but to note measurements only);

3. a description of pathological findings (the descriptions should be concise and clear, but without over-interpretation.)

4. the diagnosis or decision.

5. Pictorial documentation of pathological findings in two planes is necessary, but documentation of a normal finding (one representative scan of the organ or body region examined) is also useful, e.g. for later check-up examinations.