Sonography Practical
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Introduction

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.  

Brief Explanation

  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 because all sound waves are reflected at their surface and nothing passes through them – in fact they produce a vertical shadow under them. Areas filled with tissue allow some penetration and reflection 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.   

Theoretical part

Ultrasound and its properties

Ultrasound is mechanical longitudinal sound waves with frequencies higher than the upper audible limit of human hearing (f = 20 kHz), so humans cannot hear it. It’s wavelength is very short and travels straightforwardly through the medium. Ultrasound has a strong reflection from barriers and it is better absorbed by solid materials than liquids. Ultrasound travels in different speed through mediums of different materials.

Acoustic impedance

Acoustic impedance is a physical quantity characterizing the acoustic property of a medium. The medium ultrasound travels through counteracts according to it’s acoustic impedance. At the interface of two different mediums with different acoustic impedance the wave can refract and reflect. The wave divides, one part is reflexed and the other continues traveling into the second medium. That is the basic principle of echography.

Relationship expressing the ratio of intensities R at the interface of two mediums of acoustic impedance Z1 (before reaching the interface) and Z2 (after the interface):

R = ((Z1 - Z2) / (Z1 + Z2))²

Ultrasound in animal kingdom

Ultrasound often occurs in animal kingdom. Many animals can use it and produce it. For example bats use it for orientation in space and hunting. Dolphins can also communicate using ultrasound. Ultrasound is even used by some species of insect, for example mosquitoes and moths. There is also big amount of species that can’t produce ultrasound but are able to hear it, for example dogs, cats and mice.

Ultrasonography

Ultrasonography is a diagnostic imaging technique based on ultrasound and used for visualisation of muscles and internal organs, their sizes, structures, pathologies and damages. This diagnosis uses ultrasound of frequency 2 - 15 MHz

Ultrasound imaging

Waves that are reflected at the impedance interfaces are then recorded in the ultrasonic transducer (sensor, probe) in time between transmitted impulses. Record is achieved by using reverse piezoelectric effect. The waves make the crystals in the transducer vibrate, so they generate electric current that is then processed in the computer of the device.

Types of areas in ultrasound image

hyperechoic - white areas on the screen (areas with high intensity of reflexes)

hypoechoic - grey areas on the screen (low intensity of reflexes)

anechoic - black areas on the screen (no reflexes come)

Limits for ultrasound imaging methods

Thermal effects

Between the ultrasonic transducer and the surface of the body is formed an air layer. The impedance of the air is too low, so it is necessary to make sure that the wave travels  through a medium that has similar acoustic impedance as human body; therefore during the examination a gel (or at least water) is applied to the area of contact of the transducer with the skin.

When traveling through living tissue, ultrasound causes warming of the tissue as the result of absorption of energy. The extent to which ultrasound raises the temperature of the tissue depends on the type of the tissue. The least warmed are liquids, then soft tissues. Solid tissues such as bones are the most warmed ones. Warming also depends on the length of the exposure of ultrasound, intensity of the device and whether is the transducer held on one place or moving. It especially happens at the tissue interface but also in homogeneous tissue. The extent of absorption depends on the frequency of ultrasound. The higher the frequency is, the higher is the absorption and dispersion in tissues and the penetration of ultrasound decreases.

The quality of the detail resolution improves with the increasing frequency, but the sharpness decreases. Penetration increases with a lower frequency. In practice are used recurrent frequency probes. (lower frequencies are used when observing structures in depth, higher frequencies are used for structures situatef closer to the the surface).

Mechanical effects

As a result of the dilution and densification of the medium occur sudden and accelerated changes in the pressure of the vibration of the molecules, which could occasionally lead to mechanical damage to the structures,for instance due to cavitation. During this physical phenomenon, a vacuum tube is formed in flowing fluids or in places of fluid with rapid pressure changes, which can damage the cellular structures, when they are destructed.

Physico-chemical effects

Ultrasonic effects can also accelerate chemical reactions and excitation of molecules, blood circulation or metabolism in structures.

Ultrasound is a good method for displaying soft tissues, but unsuitable for examination of lungs and bones due to side effects.

Importance in Clinical Medicine 

Ultrasound examinations can help to diagnose a variety of conditions and to assess organ damage following illness. 

Ultrasound is used to help physicians evaluate symptoms such as: 

  • Pain 
  • Swelling 
  • Infection 

Ultrasound is a useful way of examining many of the body's internal organs, including but not limited to the: 

Heart and blood vessels, including the abdominal aorta and its major branches, liver, Gallbladder, Spleen, Pancreas, Kidneys, Bladder, Uterus, ovaries, and unborn child (fetus) in pregnant patients, Eyes, Thyroid and parathyroid glands, scrotum (testicles), Brain, Hips and  spine in infants 

Ultrasound is also used to: 

  • Guide procedures such as needle biopsies, in which needles are used to sample cells from an abnormal area for laboratory testing. 
  • Image the breasts and guide biopsy of breast cancer. 
  • Diagnose a variety of heart conditions, including valve problems and congestive heart failure, and to assess damage after a heart attack. Ultrasound of the heart is commonly called an “echocardiogram” or “echo” for short. 

Doppler ultrasound images can help the physician to see and evaluate: 

  • Blockages to blood flow (such as clots) 
  • Narrowing of vessels 
  • Tumors and congenital vascular malformations 
  • Less than normal or absent blood flow to various organs 
  • Greater than normal blood flow to different areas which is sometimes seen in infections 

With knowledge about the speed and volume of blood flow gained from a Doppler ultrasound image, the physician can often determine whether a patient is a good candidate for a procedure like angioplasty.

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 similar benefit but greater risk with as it is non-ionising (compare CT which is ionising) and does not involve very strong magnetic fields (as MRI), moreover it is a very good diagnostic tool. 

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 refections 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 images can be observed due to the fact that low frequencies can travel farther whilst high frequencies provide a better image but at shorter ranges.

Ultrasound imaging methods

Ultrasonography has become the most widespread diagnostic imaging method over the last 50 years. As mentioned above, its basic principle is the registration, processing and display of partially reflected ultrasound waves from the interface of two environments with different acoustic impedance. Based on the processing and display of the reflected ultrasound signals by the ultrasonic transducer, we recognize these basic views:

Display A - amplitude mode display (reflections modulate amplitude of deflections)

This method is one of the first when using ultrasound waves in medicine. It is the simplest way of impression in one-dimensional view. It is still used in technical spheres or ophthalmology to measure the distance of individual optical interfaces in the eye. The individual registered echoes (reflections) are displayed in the monitor as a sequence of time-shifts displayed in distance units. The displacement position corresponds to the reflection site and its amplitude of the reflected acoustic energy.

Display B - brightness mode (reflects the brightness of the on-screen brightness)

This is a representation which stood up as another progressive shift in ultrasonography. Reflected ultrasound waves are displayed as gray scale pixels. The position of the points corresponds to the position of the non-homogeneous (echogenic) environment with different acoustic impedance and the brightness corresponds to the intensity of the reflected wave (in the sense - the greater the brightness of the point, the higher the intensity of the reflected wave).

Display 2D - real mode (which we also use for practical classes)

It is the most widely used two-dimensional view. The plane of soft tissue cut is defined by the type of ultrasonic probe. Known sectoral, linear and convex probes determine the shape of the ultrasonic field. Several segments of one-dimensional display in B mode create an image, with the two-dimensional ultrasonic field being acquired either by mechanical(1.) rotation of one ultrasonic transducer in the plane of display or electronically(2.), when the probe is made up of several miniature transducers whose mutual arrangement determines the resulting ultrasonic field. The 2D view allows, among other things, different measurements in the image (it is possible to determine the cross-sections of some vessels, the size and depth of the storage of the structures monitored).

Display M - motion mode

This view is a variation of the display B method, developed especially for the needs of cardiac examination and monitoring of moving structures (movements of the heart wall, valves). When capturing the moving structure, the so-called floating echo appears on the screen with A - the image of the movement can be distinguished. By replacing time base variations with luminous points, it is possible to record the time course of their mutual movement.

Other (future perspective) views include 3D viewing (a special probe generating a three-dimensional ultrasonic field), real-time 3D viewing, or panoramic representation.

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.  

Practical part

Task 1: Image of phantom structures

Record and log (or print) the image of the phantom structures in the best possible quality from different perspectives.

Task 2: Identification of internal phantom structures

Identify the individual internal phantom structures and measure their dimensions.

For the purposes of the practice, we divide phantoms (identified structures) into 2 groups:

Cysts - typically anechoic (dark, to black), often rounded, smooth, regular surface

Tumors - Typically echogenic formations (appear light, white), various, irregular shapes, with rough surface with bumps

Further classification of findings requires many other parameters and data and is therefore beyond practical exercises.

Device description

For this particular examination we use the SonoSite 180 plus. It is a portable, software-driven and fully digitized ultrasound device. The system also allows ECG measurement, biopsy and any manipulation of captured images. In addition, downloaded data can be viewed on the monitor, transferred to a personal computer, or subsequently processed.

SonoSite 180 plus controls

Image.png

1. Power switch

2. Near - Profit driver in the near field

3. Far - Profit driver in the far field

4. Gain - Total gain controller

5. Driver menu

6. Optimization, Depth and Magnification

7. Control ball

8. Patient - device setup menu

9. Function button

10. LCD screen brightness control

11. Battery charge indicator

12. LCD Contrast Controller

13. LCD screen

14. Arrows search in the last image loop

15. Buttons to select display mode

Important Notes: 

  • For safety reasons, 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 structures.   
  • Image 2.png
       

Workflow

The device is operated manually. In a normal procedure, the treated object is treated with a surface-applied gel. In the case of the practice, ordinary water is sufficient to eliminate unwanted reflections. (TIP! Choose a system when looking for structures, for example, from top to bottom, and then you can better navigate.)

1. Turn on the ultrasound device by pressing and holding the power switch on the back left side of the instrument handle, then the device will beep and the screen will light up. Before working on the task, make sure that there are no pictures of previous practices in the device, and if so, delete them.

2. Create a new profile for the patient on the device. Press the patient and select exam / patient information in the menu that appears next. Another options will appear, select the new patient option (at the same time deleting the previous patient data). A menu with the labels name, id, accession, exam, LMP or HR will pop up. Write the group number as the name, you do not have to fill in the other information. Pressing Patient returns you to the normal view.

3. Get to know the device, its controls, and usage options. The head of the ultrasound you are examining a phantom with needs to be correctly rotated, the image reflects reversed (depends on its position). Also, set the correct depth on your device from which you are examining. Use the Depth button. The probe should be used on the surface covered with the liquid (gel). Note that you will need to save, transfer to the PC, print or draw the relevant images you capture and measure (the procedure for transferring, viewing, and printing images will be described below).

4. Record a distinct and clear picture of the internal structures of the phantom. Capture the structure you find from different, ideally perpendicular, angles. Then sketch it and describe it in the log.

5. Measure the dimensions of each identified internal structure. Distance measurement is done using a control ball that moves the cursor to the selected locations. Use the freeze button to "freeze" the image so that you get a recorded structure on it. You will see two colorful dots (blue and green) on the screen, or cursors that can be scrolled through the control balls to different locations on the screen (in your case, to the start and finish of the structure). After the first cursor is fixed using the Select button, the second cursor is released. Then fix the second cursor in another place and press the Select button again. The measured value is displayed at the top left of the screen. Take a scale placed on the table, measure the actual dimensions of the structure. Write the results in the log and compare to  each other.

6.Transfer images to your computer. To do this, use the Site Link Image Manager program. In the Sono Praktikum folder (folder documents, desktop shortcuts), in your groups’ of folders, create a new folder with the number of your group. Set the image saving to your folder in Site Link Image Manager. Choose Configure in the top menu bar, select Image Files Location, set Documents and settings \ USER \ Documents \ Sono Practitioner \ Your Circle Components \ Your Group Folder and Confirm. To start the transfer, click Start, the Image upload complete message appears when the transfer is done.

7. Viewing files. You may use any graphics software on your computer to view the files. You should find the pictures in the folder you created in the Patient Name.No and Exam Date.YYYY Month DD.

8. Print pictures. To do so, use Picture and Fax Viewer. Once you have opened the image in the program, click on the print icon and click Next, then mark all the images you print and confirm. Confirm the printer option and then print 4 images per page. Click Finish.

9. Delete pictures from the device.

Conclusion   

In conclusion, Ultrasonography is considered one of the best non-invasive techniques 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( WHAT IS 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.    

References

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