Sonography Practical

What is Sonography?
Sonography is a painless non-invasive medical procedure that uses high-frequency sound waves to produce visual images of organs, tissues, or blood flow inside the body. Depending on the situation, sonography may be used to examine the abdomen, genitalia, heart and capillaries etc.

How does it work?
Sonography is based on ultrasound (frequency above 20 KHz). When high frequency sound waves travel forwards, they continue to move until they make contact with an object. Then a certain amount of the sound bounces back.

For example, sound waves go through areas that are hollow or fluid-filled such as the bladder and blood vessels. These areas appear black on the screen. Areas filled with tissue allow some penetration and refraction of sound and produce a grayish-white image. Really hard structures such as bone produce a bright white image as the sound waves completely bounce back to the transducer. A layer of aqueous gel is applied over the skin to make sure that the sound has an air-free path to the organ.The ultrasound waves penetrate the body, strike the organ moving through various types of tissue with different acoustic impedances and reflect back to the surface.The reflected waves are processed by the computer into a 2D image that appears on screen. The image is called as Sonogram.

Medical Importance of Sonography
Sonography refers to the use of ultrasound waves to produce images of the internal structures of the body of a patient. It requires almost no preparation.

Sonography may be used in the diagnosis of different symptoms or diseases. For example, it is used in cases to determine cause of pain, swelling or infection of internal organs. Another important use of sonography is to examine pregnant women to determine the condition of the fetus and/or the progress of the pregnancy.

The procedure involves placing a small transducer on the skin. The transmitted high-frequency sound waves collect the sound bouncing back from different objects in the body that all have different densities. Then a computer uses those sound waves and creates an image.

The advantage of Sonography in comparison to other imaging methods as X-ray is that it uses no ionizing radiation. It captures images of structures and movement of internal organs or blood flowing through vessels in real time.

Moreover, it can only conduct imaging in thin sections of the body. Presently, physicians are developing 3D ultrasound technology that formats the sound wave into a three-dimensional image.

Literary Review
Sonography is when a sound wave strikes an object, and  it gets partially reflected and by measuring these echo waves, it is possible to determine how far away the object is, as well as the object’s size. As compared to other non-invasive techniques for viewing the internal organs like x-rays, MRIs or CT scans, the ultrasonography technique comes out on the top as it has lesser risk compared to the benefit unlike the other methods which have almost equal benefit but greater risk.

How does it work?
Ultrasound has a frequency in the range of 2 to 20 MHz meaning that people are unable to hear them. The wave then moves through various types of tissue with different acoustic impedances affecting the magnitude of the wave that are reflected. The detector inside the device then picks up these different intensities of vibrations and converts them into an image of the said area. The image received is in 2D as this makes it most clear to the professional operating the machine and because a single planar scan is most accurate with ultrasound measurement devices.

Advantages:

 * Noninvasive examination, doesn’t need needles or any injections.
 * Not painful.
 * Widely available, easy to use and less expensive than any other imaging tests.
 * Extremely safe, and doesn’t use any ionizing radiation.
 * Gives clear picture of soft tissues which can’t be seen well by x-ray images.
 * The preferred imaging for the diagnosis and monitoring of pregnant women, and unborn babies.
 * Provides real-time imaging.

Disadvantages:

 * Can't penetrate bone or gas.
 * If the body size of the patient is too great, this will effect the imaging quality negatively.
 * Completely depends on the operator's/sonographer's expertise.

Imaging Principle:
The basic calculations of ultrasound imaging have to do with acoustic impedance. Acoustic impedance can be summarized as, opposition to the flow of sound through a surface. Also the equation listed below describes the very nature of this term.

Acoustic impedance = Density*Velocity

If a targeted object is deep one must use a low frequency whilst when something superficial is observed, it is necessary to use a higher frequency. This way more clear results can be observed due to the fact that low frequencies can travel farther whilst high frequencies provide a better image but at shorter ranges.

Ethics:

 * In case of the fetal sex, disclosure can be done only with an adequate consent process.
 * In obstetric sonography, the procedure  can be performed only after 18 weeks and sessions must not exceed the limit prescribed in the guidelines.
 * There must be a Doctor-patient confidentiality.

Risks
For standard diagnostic examination, there are no known harmful effects on humans.

The Equipment
SonoSite 180 Plus, the portable ultrasound device uses a convex probe that is a transceiver with an operating mean of 2MHz.Because of the convex form of the probe, the image formed by the probe is narrow closest to the probe and becomes wider with depth.

Provided dummy with internal structures. In usual cases a special type of gel, which is made out of mostly water, is used to carry the acoustic energy, given by the head of the probe, to the targeted tissue without interfering with air at any point, due to its incredibly high absorption and low impedance. For this practical, water is used instead of the gel.

The Methodology
For this practical, you will be working with the Sonosite 180 Plus device. It is a portable ultrasound device capable of examination and imaging in a variety of modes. These may include: In this practical, the focus will be on basic 2D grayscale imaging (brightness, B-scan). The imaging will be conducted on the provided dummy.
 * 2D (B-scan)
 * M-mode
 * Doppler modes

System Controls:

 * 1) Power switch, located on the rear of the system handle,
 * 2) Near – affects gain of shallow echoes
 * 3) Far – affects gain of deeper echoes,
 * 4) Gain – affects overall gain,
 * 5) Menu controls,
 * 6) Menu, Depth, Zoom,
 * 7) Trackball,
 * 8) Patient,
 * 9) Function key,
 * 10) Battery charge indicator,
 * 11) LCD brightness control,
 * 12) LCD contrast control,
 * 13) LCD,
 * 14) Cine Arrow keys and Freeze key,
 * 15) Mode controls

Important Notes:

 * For safety precautions, the device should only be used for sonographic imaging on the provided dummy, and not on real human structures.
 * Accompanying the sonography device is a convex sector cardiological probe with a mean operating frequency of 2 MHz. The shape of the probe allows for a fan shaped image, where it will be narrow when close to the probe and wider as depth increase into the provided dummy. The lower frequency of the probe allows for improved imaging of deeper internal structures. However, the probe does not allow for high quality imaging for more superficial internal structures.

Switching the Device On/Off:
Turning the Device On: Press and hold the Power switch until the device beeps

Turning the Device Off: Press and hold the Power switch until the device beeps twice and the display turns off

Waking up the Device from Sleep Mode: Press any button on the device to wake up the system.

2D Imaging:
Turning on 2D Imaging: When the system is turned on, it will initiate in 2D mode. If the system is another imaging mode, it can be returned to 2D mode by pressing the 0 key.

To adjust the viewing angle of the display: The display screen is on a hinge which allows the user to change the viewing angle. The display screen angle can simply be adjusted by holding it from the top and moving it forwards or backwards, without surpassing the maximum angle of the hinge.

To adjust the display brightness and contrast: The brightness and contrast controls are located on the right side of the display screen. The upper part of each control will increase the value, while the lower part will decrease the value of the desired setting.

To adjust gain: Gain refers to the level of image amplification. The gain controls, as well as near and far, are located on the left side of the display screen. This will allow for the increase or decrease of the amount of gain applied to the near field, far field, or overal image.

To adjust depth: The depth controls are located on the left underneath the screen. Pressing the “up” Depth key will decrease depth, where as the “down” Depth key will increase the depth. The depth value will be displayed in the bottom right corner of the display screen. Vertical depth scale is marked in 1 cm increments and 5 cm in larger increments.

To zoom the image: Press the Zoom key. The image will be magnified by a factor of two. To exit the magnification, press the Zoom key again. Zooming will only work during real-time imaging and will not work on frozen/saved images.

To freeze the image: Live

To change the image orientation: Press the 0 key and the Menu key, then select Orientation from the on-screen menu. Select the Orientation again for the desired orientation. There four different possible orientations. Next to the on-screen menu, the current orientation setting is displayed.

2D Measurements:
Three types of measurements can be conducted in 2D mode:
 * Distance

Only Distance will be measured in this practical. After freezing the image, the internal structures can be measured.
 * Area (ellipse)
 * Circumference (ellipse)

To perform a distance measurement: The measuring cursor can be moved around over the image using the Trackball. Use the Trackball to place the First Caliper. Press the Select key to place the First Caliper and to activate the Second Caliper. Use the Trackball to position the Second Caliper. Press the Select key to place the Second Caliper. Measurement is complete and the measured value is shown in the image or in the bottom left corner of the display screen. To exit the measurement mode, press the Freeze key.

Procedure:

 * 1) Begin by turning on the sonographic device.
 * 2) Understand how the device and its various modes are operated and adjusted.
 * 3) Use the device to analyze the interior of the provided dummy to determine the different internal structures.
 * 4) Sketch (in scale compared to the neighboring structures) and describe the results in the appropriate section of the provided report sheet.
 * 5) Once all the sketches are complete and all the internal structures have been identified, measure the proportions of each structure.

Conclusion
In conclusion, Ultrasonography is considered one of the best non-invasive technique used to locate objects within the body. With this technology it is possible to examine the human body without the need for surgery or other procedures. And in medicine they use this device to detect changes, appearance, and counter of an organs, vessels and tissues.

The Future of Ultrasonography
In the first-generation units, image conversion was carried out by inbuilt hardware, thereby making the systems quite bulky. The current generation of ultrasound equipment uses external computing systems that perform the scan conversion and image display. This has resulted in device portability and enhanced the computing power with major improvements in image quality. Developments in signal multiplexing technology have enabled the adoption of a new generation equipment: 3-D and 4-D systems. It is expected that with these factors in mind, manufacturers of 3DUS and 4DUS devices will continue their efforts toward improving calculation power.