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ultra sound.pptx

  1. Nature of sound General Definition “Sound is a disturbance of mechanical energy that propagates through matter as a pressure wave ” Frequency the measurement of the number of times that a repeated event occurs per unit of time. It is also defined as the rate of change of phase of a sinusoidal waveform. Period An interval of time that an event, chain of events, instance or happening, takes place within. It is measured between a start point and an end point and generally repeats, or progresses, in a cycle with the end point of one period being the start point of the next. f T 1 
  2. What is ultrasound
  3. Speed of Sound Speed of Sound in body  1500m/s ~ 1600m/s Average Speed of Sound in soft tissue 1540m/s
  4. Sonar in the Sea
  5. THERAPEUTIC ULTRASOUND (1920-1940) • Researchers began to determine the conditions under which ultrasound was safe. • Applied ultrasound to therapy, surgery, and cancer treatment • Ultrasound was used to treat members of European soccer teams as a form of physical therapy, to appease arthritic pain and eczema and to sterilize vaccines
  6. The generation of images by ultrasound is based on the pulse-echo principle. It is initiated by an electric pulse that leads to the deformation of a piezoelectric crystal housed in a transducer. This deformation results in a high-frequency (>1,000,000 Hz) sound wave (ultrasound), which can propagate through a tissue when the transducer is applied, resulting in an acoustic compression wave that will propagate away from the crystal through the soft tissue at a speed of approximately 1530 m/s.. In diagnostic ultrasound imaging, the applied frequency is generally between 2.5 and 17 MHz, which is far beyond the level audible by humans, and is thus termed ultrasound . HOW THE IMAGE IS FORMED IN ULTRASOUND MACHINE
  7. HOW THE IMAGE IS FORMED IN ULTRASOUND MACHINE Electric field applied to piezoelectric crystals located on transducer surface Mechanical vibration of crystals creates sound waves Each crystal produces an US wave Summation of all waves forms the US beam Wave reflects as echo that vibrates transducer Vibrations produce electrical pulses Scanner processes and transforms to image
  8.  The principal determinants of the ultrasound wave are: (1) wavelength (λ), which represents the spatial distance between two compressions  frequency (f), which is inversely related to wavelength  velocity of sound (c), which is a constant for any given medium  These three wave characteristics have a set relationship as c = λf. An increase in the frequency (i.e., shortening of the wavelength) implies less deep penetration due to greater viscous effects leading to more attenuation
  9. Lower frequencies = less resolution but deeper penetration Higher frequencies = smaller wavelength capable of reflecting from smaller structures The shorter the wavelength, the better the resolution, giving aclearer image Readily absorbed by tissue = less penetration Higher frequency = higher resolution Muscles, tendons 7-18 mHz
  10. AMPLIFICATION  The echoes that return from deeperstructures are not as strong as thosethat come from tissues nearer the surface  Amplification done by the time-gain-compensation (TGC) amplifier
  11. TGC ( TIME GAIN COMPENSATION  Attenuation correction settings.  Optimal settings of time-gain compensation (TGC) can provide a uniform display of signal intensity for echoes from similarly reflecting structures, across various depths of the scan sector.
  12. Transmitter(TX) Beamformer Beam steering Receiver Processor Transducer Moniter Memory Scan Converter Hard copy Digital Storage Front End Back End Transmitter(TX) Beamformer Beam steering Receiver Processor Memory Scan Converter 1.Generate Ultrasound 2. Receive Echo signal 1.Change RF data to Image data 2.Process Image data can be available to display on Monitor BLOCK DIAGRAM OF ULTRASOUND SYSTEM
  14.  a. TX Data / Pulser : produce high voltage to vibrate piezoelectric transducer  b. Limiter : eliminate high voltage  c. Pre-amp : amplify Echo signal  d. TGC : readjustment gain from attenuation by depth  e. ADC : convert Analog signal to Digital signal  f. BF : RX focusing to reduce the time delay RX
  15. Ultrasound system modes
  16. B-Mode (Brightness Mode) in ultrasound is a setting that creates a two-dimensional (2D) greyscale image on your ultrasound screen and is the most used mode. It is also commonly called 2D mode.
  17. M-Mode (Motion Mode)  Ultrasound M-mode is defined as a motion versus time display of the B- mode ultrasound image along a chosen line. The motion is represented by the Y-axis and time is represented by the X-axis.
  18. M-mode imaging step by step • M-mode Step 1: Acquire 2D image and Center Structure of Image • M-mode Step 2: Push the M-mode button to make the M-mode cursor line appear • M-mode Step 3: Place the M-mode cursor line along the structure of interest • M-mode Step 4: Push the M-mode button again to activate M-mode • M-mode Step 5: Push the Freeze Button • M-mode Step 6: Scroll to the desired image • M-mode Step 7: Push the Measure Button • M-mode Step 8: Measure Area of Interest
  19. Second Harmonic Imaging  Current ultrasound systems are based on fundamental and harmonic imaging. In fundamental imaging the transducer listens for the ultrasound of equal frequency to the emitted wave. However, at higher amplitudes of the transmitted wave, wave distortion may occur during propagation, causing harmonic frequencies (multiples of the transmitted frequency), which can be received by the transducer when properly implemented, Such second harmonic images have significantly improved signal-to- noise ratio and improved endocardial border definition .
  20. Doppler Imaging  The Doppler effect states that the frequencies of transmitted and received waves differ when the acoustic source moves towards or away from the observer (due to wave compression or expansion, depending on the direction of motion)  The Doppler effect can be applied to measuring blood (and tissue) velocities, by measuring the difference between the frequency of emitted and received ultrasound, which will be reflected off moving red blood cells  This difference between the emitted and received frequency is termed the Doppler shift or Doppler frequency , which is directly proportional to the velocity of the reflecting structures (red blood cells, i.e., blood flow)
  21. Continuous Wave Doppler  The Doppler modalities used in echocardiography are pulsed wave (PW) and continuous wave (CW) Doppler, as well as color flow mapping (color flow Doppler). In CW, separate piezoelectric crystals continuously emit and receive ultrasound waves, and the difference between the frequencies of these waves (the Doppler shift) is calculated continuously
  22. Pulsed Wave Doppler  As opposed to CW, in PW Doppler ultrasound is emitted and received in a similar manner to 2D imaging: individual pulses are emitted as brief. After emitting such a pulse, the transducer “listens” to returning signals only during a short, defined time interval following pulse emission.
  23. Color Doppler Step by step • Color Doppler Step 1: Activate Color Doppler • Color Doppler Step 2: Adjust Color Doppler Area • Color Doppler Step 3: Adjust Color Doppler Scale • Color Doppler Step 4:Adjust Color Doppler Gain
  24. Power Doppler Mode  There is a mode like color Doppler that you may encounter called Power Doppler. This mode does not show up as red or blue on the screen but only uses a single yellow color signifying the amplitude of flow. So, you can’t tell if the flow is going towards or away from the probe given that it has only one color. It is more sensitive than color Doppler and is used to detect low flow states such as venous flow in the thyroid
  25. PROBES
  26. 3D probe types
  27. Phased Array (Sector) Ultrasound Probe  The phased array (or sector array) transducer is commonly branded as the “cardiac probe” and has a frequency range from 2-6MHz. It has a similar frequency range as the convex probe but has a smaller and flat footprint.  The advantage of this probe is that piezoelectric crystals are layered and packed in the center of the probe making it easier to get in-between small spaces such as the ribs
  28. Linear Ultrasound Probe  The linear ultrasound probe is a high- frequency transducer (5-15 MHz) that will give you the best resolution out of all the probes but is only able to see superficial structures. A general rule of thumb is that if you are going to ultrasound anything less than about 8cm, then use the linear probe. Anything above 8cm you won’t be able to see much.  The linear probe will give you a rectangular field of view that corresponds with its linear footprint
  29. CONVEX Ultrasound Probe  The convex ultrasound probe has a frequency range of 2-5MHz. It is considered a low-frequency probe and has a large/wide footprint. The convex ultrasound probe is often used for abdominal and pelvic ultrasound exams. However, it can also be used for cardiac and thoracic ultrasound exams but is limited by the large footprint and difficulty with scanning between rib spaces
  30. Endocavitary Ultrasound Probe  The Endo cavitary probe has a convex footprint with a wide view but has a much higher frequency (8-13 MHz) than a convex ultrasound probe. The image resolution of the endo cavitary probe is exceptional, but like the linear probe, it must be adjacent to the structure of interest since it has such a high frequency/resolution, but poor penetration.
  31. 3D , 4D convex probe  3D imaging allows fetal structures and internal anatomy to be visualized as static 3D images. However, 4D ultrasound allows us to add live streaming video of the images, showing the motion of the fetal heart wall or valves, orblood flow in various vessels. It is thus 3D ultrasound in live motion
  32. Indicator (Orientation Marker) Position  The “probe indicator” on the ultrasound probe can be identified as an orientation marker on one side of the probe. This corresponds to the indicator or orientation marker on the ultrasound image.
  33. Ultrasound IMAGE Indicator (Orientation Marker) Position  In general, for almost all standard applications and procedures the indicator orientation marker position will be on the LEFT side of the screen. In cardiac mode, the indicator orientation marker will be on the RIGHT side of the screen.
  34. How to do ultrasound examination step-by- step  Step 1: Power Button  the most important button of all is the power button! Simple enough!
  35.  Step 2: Switch to the Correct Ultrasound Probe/Transducer  we should already know what ultrasound probe we need to use based on the application we are performing. So after turning on the ultrasound machine, the next most important step is to switch to the correct ultrasound transducer
  36.  Step 3: Application Preset  after switching to the correct ultrasound probe, the next step is to select the correct application preset for that transducer.  Each transducer will have a different list of application presets based on its frequency and footprint.
  37.  Step 4: Depth  there are some ultrasound settings that may need to be adjusted to optimize your ultrasound settings further.  The first of these ultrasound settings you should adjust is the depth. The ultrasound depth setting is simply how deep you want the ultrasound machine to be able to scan.
  38.  Step 5: Gain (Overall)  After optimizing your depth, the next ultrasound setting you should adjust is your gain.  Ultrasound gain simply means how bright or dark you want your image to appear. It increases or decreases the strength of the returning ultrasound signals that you visualize on the screen.
  39.  All ultrasound machines will have an “Overall” Gain setting that, when increased or decreased, will make the entire ultrasound image brighter or darker. This is good to use when your entire imaged is too dark (under-gained) or too bright (over-gained)
  40. Step 6: Near/Far Field Gain and Time Gain Compensation (TGC)  Adjusting the Time Gain Compensation (TGC) allows you to adjust the gain at almost any depth of your ultrasound image, not just the near and far-fields. The top rows of the Time Gain Compensation control the nearfield gain and the bottom rows control the far-field gain
  41. Step 7: Freeze, Measure (Caliper), Image/Video Capture  Freeze  Just like the world implies, the “freeze” button freezes a frame for you, so you have time to view it in more detail. The ultrasound machine will usually store a 10-30 seconds of data and you can scroll back to see previous frames as well.  Calipers (measure)  Calipers are an important feature of ultrasound machines that allows you to measure the distance of specific structures of interest.  Image/Video Capture  All ultrasound machines will allow you to save an image and/or video clip of your ultrasound scan. This is important if you are trying to archive, bill, or use any ultrasound images/videos as teaching files.
  42. Advantages of Ultrasound  It’s a noninvasive process  It’s a painless treatment  This is the only way to tell the difference between a cyst and a solid mass by special mode called elastography  Patient is never exposed to radiation during an ultrasound  Ultrasounds do not cause any health problems  We can use ultrasound to detect blood flow through vessels  Widely available  Ultrasound devices are more accurate which can place objects within 5 mm of distance  It provides clear image of soft tissues which do not show up in X-Ray images
  43. Disadvantages of Ultrasound  Many cancers cannot be detected via an ultrasound  ultrasound requires a highly experienced and skilled operator, as well as good equipment  It has poor penetration through bone or air  The quality of results and use of equipment's depend on skills of operator  Image resolution is less comparing to CT and MRI scan  Air or bowel gas prevents visualization of structures  Hard tissue cannot be imaged  Deep structures cannot be visualized
  44. Conclusion  Ultrasound is a wide sector. It has so many advantages. As a technical engineer we can be change maker by using ultrasound. So, considering all the positive sides we can say we can make hope to people and provide them a healthy life by bringing newer advances in ultrasound