ULTRASOUND SCAN

  Ultrasound, also identified as sonography or ultrasonography, is a medical diagnostic imaging technique based on the application of ultrasound. It uses high-frequency sound waves (1–20MHz) to produce pictures of the inside of the body such as tendons, muscles, joints, vessels and internal organs. Ultrasound is safe, noninvasive, and does not use ionizing radiation (U.S. Department of Health and Human Services, 2016). 

It is used to help diagnose the causes of pain, swelling and infection in the body’s internal organs and to examine a baby in pregnant women and the brain and hips in infants. It is also used to help guide biopsies, diagnose heart conditions, and assess damage after a heart attack (U.S. Department of Health and Human Services, 2016). 

There are different ways to display ultrasound signals. The three major types are A-Mode, B-Mode and M-Mode. A-mode (amplitude mode) is the simplest type of ultrasound. B-mode (Brightness mode) is the black and grey image we see on the monitor when we first turn on the machine. M-mode (Motion mode) is used to record movement of tissue over time (Kaur, 2013). 

There are three main types of diagnostic ultrasounds such as two- dimensional, 3D ultrasound imaging and Doppler ultrasound. Two- dimensional ultrasound displays a two-dimensional image, or slice, of a three-dimensional object. Advancements in ultrasound technology include threedimensional (3-D) ultrasound that formats the sound wave data into 3-D images. Doppler ultrasound is based upon the Doppler Effect. There are three types of Doppler ultrasound such as Color Doppler, Power Doppler and Spectral Doppler (Kaur, 2013)

ULTRASOUND SCANNER

Ultrasound scanners consist of the following parts:

 1.1.TRANSDUCER 

The transducer also known as probe is the part of the machine that produces the sound waves and receives the echoes. There are used three main types of transducer in medical imaging (Wang, et al, 2016).

a . LINEAR ARRAY TRANSDUCER

A Linear array has all the piezoelectric crystals set in a line across the transducer face. This produces a rectangular ultrasound image and is used for vessels, vascular access musculoskeletal imaging, anywhere we need a wide ‘near field’ but not a lot of depth (Wang, et al, 2016).

b. CURVED ARRAY TRANSDUCER 

A curved array is a transducer where the crystals are arranged along a curved surface, this produces a wide near field, and a wide far field. This produces an image with a curved upper and lower edge. This type of transducer is used for abdominal, obstetrics, gynaecology and anywhere we need a lower frequency and good depth penetration (Wang, et al, 2016). 

c. PHASED ARRAY TRANSDUCER 

A phased array transducer, is one which the crystals are fired in phases to produce image on the monitor. This type of transducer is used for cardiac imaging, difficult or deep intercostal views of the abdomen and sometimes for neonatal head imaging (Wang, et al, 2016)

1.2.TRANSDUCER PULSE CONTROLS 

The ultrasound machine operator creates and alters the frequency and duration of pulses coming from the probes (Wang, et al, 2016). 

1.3.THE CENTRAL PROCESSING UNIT (CPU) 

The brain of the ultrasound machine, it sends the electrical signals to the transducer probe and receives signals back from it. The CPU carries out all the data processing necessary to create the final image (Wang, et al, 2016). 

1.4.DISPLAY 

Monitor that converts the processed data from the CPU into black and white or color images (Wang, et al, 2016). 

1.5.THE KEYBOARD AND TRACKBALL 

These allow the ultrasonographer to add notes to the images as they are displayed (Wang, et al, 2016). 

1.6.STORAGE DEVICE 

It allows to store ultrasound machine images to hard disk, recordable CD or DVD, or radiographic film (Wang, et al, 2016). 

1.7.PRINTER 

Thermal printer is usually attached to the machine to produce hard copies of the images can be printed as required (Wang, et al, 2016). 

2. WORKING PRINCIPLE OF ULTRASOUND SCANNER 

Piezoelectric effect is the basic principle of production of ultrasound. Transducer consists of one or more crystals in a plastic housing. A high frequency potential difference is applied across the crystals causing them to change shape very rapidly is called the piezoelectric effect; hence the crystals are called piezoelectric crystals (Wilhjelm, et al, 2016). High frequency sound waves are generated. The sound waves are focused by an acoustic lens. 

When sound waves bounce back to the probe they cause the crystals to change shape and this generates a potential difference which can be measured. This signal is processed to form the ultrasound image. Because the same piezoelectric crystals are used for sending and receiving the ultrasound pulses they should operate in a switched or pulsed mode. This means that they emit a quick sound pulse, rest and then listen for the echo. This switching between transmitting and receiving modes happens many thousands of times a second (Wilhjelm, et al, 2016).

3. HOW AN ULTRASOUND MACHINE WORKS 

Ultrasound involves the use of a transducer also called probe, contain piezoelectric crystal sensor and then ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through the gel into the body. The transducer collects the sounds that bounce back and are detected with piezoelectric crystal sensor. The distance from the transmitter probe and the anatomical structure can be calculated, and this data is used to produce an image. Computers can manipulate the transducer data to present three-dimensional or moving images (Gill, 2012).

 4. CLINICAL APPLICATIONS OF ULTRASOUND 

In clinic using ultrasound machines can be used in obstetrics, cardiology, digestive diseases, and urology and gynecology diagnosis of diseases (Forsberg, et al., 1998).

4.1.OBSTETRICS

An ultrasound exam uses high-frequency sound waves to scan a woman’s abdomen and pelvic cavity, creating a picture of the baby and placenta. Ultrasound is used in early pregnancy to confirm intrauterine and to exclude ectopic pregnancy. A fetus can be detected starting at around seven weeks' gestation and this can be achieved even earlier using transvaginal probes (Forsberg, et al., 1998)

4.2.RENAL ULTRASOUND

A renal ultrasound is a safe and noninvasive test that uses sound waves to make images of the kidneys, ureters, and bladder. During the examination, an ultrasound machine sends sound waves into the kidney area and images are recorded on a computer. The black and white images show the internal structure of the kidneys and related organs. It can check the size, shape, and location of kidneys. It can be identified tumors in the bladder, renal masses, and bladder outflow obstruction due to an enlarged prostate (Forsberg, et al., 1998).

4.3.PELVIC ULTRASOUND

A pelvic ultrasound is a scan that looks at the organs and structures in pelvic area. It includes at uterus, cervix, vagina, fallopian tubes and Ovaries. It can use Doppler ultrasound to look at how blood is flowing in certain pelvic organs. Pelvic ultrasound may be done in 2 ways such as transabdominal and trans-vaginal. There are used for finding problems in the structure of the uterus, including endometrial conditions, find fibroid tumors, masses, cysts, and other types of tumors within the pelvis, find an intrauterine contraceptive device, diagnose pelvic inflammatory disease or other types of inflammation or infection and find the cause of bleeding after menopause (Forsberg, et al., 1998) 

4.4. BREAST ULTRASOUND

Breast ultrasound is an imaging test that uses sound waves to look at the inside of breasts using a wand-like device called a transducer over the skin to make the images of breasts. The transducer sends out sound waves that bounce off breast tissue. The sound waves are too high-pitched to hear. The transducer then picks up the bounced sound waves. These are made into pictures of the inside of breasts. It can be found breast problems. It also sees how well blood is flowing to areas in breasts. Breast ultrasound is not usually done to screen for breast cancer (Forsberg, et al., 1998).

4.5.CHEST ULTRASOUND

A chest ultrasound is an imaging test that uses sound waves to look at the structures and organs in chest. A chest ultrasound can look at lungs, heart, esophagus, mediastinum, space between the lungs and pleural space, and other structures in the chest. It can see how well lungs and heart are working and to see how well diaphragm moves. It may use ultrasound to see how blood flows through the organs in chest, guide a needle to take a sample of tissue, and guide a needle to remove fluids from the chest. A chest ultrasound can also be used to look at heart and its valves. the test is called an echocardiogram (Forsberg, et al., 1998). 

4.6. ABDOMINAL ULTRASOUND

An abdominal ultrasound is a procedure used to assess the organs and structures within the abdomen. This includes the liver, gallbladder, pancreas, bile ducts, spleen, kidneys, and abdominal aorta. Ultrasound may be used to easily view the abdominal organs and structures from outside the body, to guide needles used to biopsy, to drain fluid from a cyst or abscess and to assess blood flow to abdominal organs. An abdominal ultrasound uses a handheld probe called a transducer. Abdominal ultrasound may be used to assess the size and location of organs and structures in the belly. It can also be used to check the abdomen for conditions such as cysts, tumors, abscesses, blockages, clots in blood vessels, and infection (Forsberg, et al., 1998). 

5. TROUBLESHOOTING ULTRASOUND MACHINES