Ultrasound Knobology - 3.pdf

Ultrasound Knobology - 3 The Trackball The Trackball or Mouse pad is used for moving objects on the monitor and for scrolling back in freeze mode. It has a multi-function and can be used in conjunction with caliper placement, screen annotation, or moving the zoom or Doppler boxes to the...

Ultrasound Knobology - 3 The Trackball The Trackball or Mouse pad is used for moving objects on the monitor and for scrolling back in freeze mode. It has a multi-function and can be used in conjunction with caliper placement, screen annotation, or moving the zoom or Doppler boxes to the desired location. Res or Zoom Some ultrasound equipment has this function, which allows magnification of areas of the ultrasound image displayed on the monitor in real time. The trackball is used in conjunction with the Res/Zoom knob to choose the area for magnification. What does res mean on ultrasound? Frequency Adjustment. “Res” translates to the highest frequency band available on the transducer. These settings are used for superficial imaging. “Gen” represents mid- range frequencies that are often the default setting 2-D The 2-D knob stands for the 2-D mode of scanning or the traditional B-mode imaging. B stands for brightness (mode). In this mode, the image is displayed in grey scale and is comprised of pixels arranged in a sector or linear fashion with various shades of grey thus representing the Figure below. ❖ Two-dimensional ultrasound image of the fetal chest at the level of the four- chamber view. ❖ Note the various gradation of grey with the ribs being the brightest (echogenic) followed by the lungs and heart (labeled). ❖ The amniotic fluid (AF) is black in color (anechoic) reflecting a weak intensity of the returning echo. Ultrasound Modes  A-mode: A-mode (amplitude mode) is the simplest. A single transducer scans a line through the body with the echoes plotted on screen as a function of depth. A- Mode presents reflected ultrasound energy on a single line display. The strength of the reflected energy at nay particular depth is visualized as the amplitude of the waveform. B-Mode (Brightness Mode) In ultrasound B Mode is a setting that creates a two-dimensional (2D) greyscale image on your ultrasound screen and is the most commonly used mode. It is also commonly called 2D mode. B-mode is the single most important mode you need to master in order to be proficient at point of care ultrasound (POCUS). All of the other modes rely on you getting a good B-mode (2D) image. What is B-mode on ultrasound? B-Mode is image display composed of bright dots representing the ultrasound echoes. Thus B Mode converts A Mode information into a two dimensional grayscale display. The brightness of each dot is determined by the amplitude of the returned echo signal  Tip: Sometimes, you may be in a different mode or ultrasound machine setting and may wonder how to just reset your settings. Usually pushing the B-mode or 2D button on the ultrasound machine will reset everything and bring you back to the simple B-mode setting.  C- Mode is a color representation of blood flow velocity and direction. D- Mode is a spectral representation of blood flow velocity and direction. M-Mode Ultrasound M-mode is defined as a motion versus time display of the B-mode ultrasound image along a chosen line. The M-Mode knob activates the M-Mode function of the ultrasound machine and is a scrolling display allowing the operator to view and record organ motion. M Mode The motion is represented by the Y-axis and time is represented by the X-axis. Common applications for M-mode include looking at E point septal separation in cardiac scanning or calculating fetal heart rate for obstetrics. You can also use M-mode in lung ultrasound to evaluate for lung sliding and rule out pneumothorax.  The E-Point Septal Separation (EPSS) is an easy measurement to obtain that is accurate in estimating the Left ventricular ejection fraction (LVEF). Left ventricular ejection fraction (LVEF) is the measurement of how much blood is being pumped out of the left ventricle of the heart (the main pumping chamber) with each contraction EPSS is measured in the parasternal long axis view (PLAX) of the heart, which gives a view of the left ventricle and is often used to assess its function M-Mode M-Mode cursor line (dashed line) is shown through the fetal heart (small bracket) in the upper image. Note the corresponding M- Mode display (large bracket) in the lower image showing cardiac motion. M-Mode The M-Mode display corresponds to the anatomic components that the M-Mode cursor intersects. The M-Mode is used primarily to document motion, such as cardiac activity of the fetus in early gestation Here are the steps to acquiring an M-mode Image: 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 Ultrasound Modes cont. P -Mode is used to visualize very low blood flows in color. Unlike C Mode, this mode does not show the operator flow direction. Triplex is the simultaneous operation of B Mode, C Mode and D Mode. Colour Flow The colour flow knob activates color flow or color Doppler, which adds a box superimposed on the 2-D real-time image on the screen. The operator can control the size and location of the color box on the 2-D image. Color flow or colour Doppler detects blood flow in the insonated tissue and assigns colour to the blood flow based upon the direction of blood flow.  By convention, red is assigned for blood flow moving in the direction of the transducer (up) and blue is assigned for blood moving in the direction away from the transducer (down). The operator can also control the velocity scale of blood flow (pulse repetition frequency) and the filter or threshold of flow. These parameters are important in assessing various vascular beds.  Note that the display of colour flow follows the physical principles of Doppler flow and thus if the ultrasound beam is perpendicular to the direction of flow, colour Doppler information will not be displayed on the monitor. Newer ultrasound equipment tries to overcome this limitation by providing other means for display of blood flow such as Power Doppler which primarily relies on wave amplitude and B-flow (not to be confused with B Mode) both of which are relatively angle independent. What is B flow in ultrasound? B-Flow is a type of ultrasound imaging that allows visualization of blood flow by selectively enhancing the signal from moving blood cells while simultaneously suppressing tissue signal. Unlike colour Doppler, it does not show flow direction or amplitude What is pulse wave in ultrasound? ❖ Pulsed wave (PW) Doppler uses the Doppler principle that moving objects change the characteristic of sound waves. ❖ By sending short and quick pulses of sound, it becomes possible to accurately measure the velocity of blood in a precise location and in real time Advanced Ultrasound Modes (Doppler)  Initially, these Doppler modes may seem confusing but in reality, all Doppler settings are simply meant to detect speed going either Towards or Away from your probe. Understanding this is the first step to mastering ultrasound Doppler. Colour Doppler Mode The most common Doppler mode you will use is colour Doppler. This mode allows you to see the movement of blood in arteries and veins with blue and red patterns on the ultrasound screen.  A common question that comes up with colour Doppler is: What do the colors on ultrasound mean? The answer is: RED means there is flow TOWARDS the ultrasound probe and BLUE means that there is flow AWAY from the ultrasound probe. It is a misconception that red is arterial and blue is venous. It actually just depends on the direction blood is flowing relative to the angle of your ultrasound beam. Colour Doppler Steps Colour Doppler Step 1: Activate Colour Doppler Colour Doppler Step 2: Adjust Colour Doppler Area Colour Doppler Step 3: Adjust Colour Doppler Scale Colour Doppler Step 4:Adjust Colour Doppler Gain Colour Doppler Steps Power Doppler Mode There is a mode similar to colour 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 colour 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 colour. It is more sensitive than colour Doppler and is used to detect low flow states such as venous flow in the thyroid or testicles. The “Other” Doppler Modes Now some learners may feel like the “other doppler modes” such as Pulse wave, Continuous wave, and Tissue Doppler are very advanced settings. However, the same principles of colour Doppler apply to these other Doppler modes as well. The ultrasound probe is just detecting flow or motion either TOWARDS or AWAY from it. If flow/motion is towards the probe there will be a positive deflection and if it is away from the probe there will be a negative deflection. Here is an illustration that sums up the those Doppler modes Pulse Wave (PW) Doppler Mode Pulse Wave (PW) Doppler allows you to measure the velocity of blood flow (at a single point). A unique aspect of Pulse Wave Doppler is that you can specify to the ultrasound machine exactly where you would like the machine to measure the velocity using the Sample Gate. It’s usually seen by two horizontal lines along your cursor. You can move your cursor and your sample gate and place it exactly where you want to measure your blood velocity. See the example figures below: What is range gate in ultrasound? The focal area interrogated by spectral Doppler is known as the range gate (sample volume). The spectrum of velocities of blood cells within the range gate is displayed in a waveform on a two-dimensional display with time on the x-axis and frequency on the y-axis  In pulsed wave Doppler (PWD), the user defines a small area (the sample "volume" or "gate") within the B-mode image, and (based on pulse repetition frequency, or the time required for returning sound waves) only the Doppler shifts from that area are recorded. While avoiding the range ambiguity of continuous wave Doppler, the intermittent sampling of PWD, especially at targets that are further away from the transducer, renders the modality vulnerable to aliasing at higher velocities  Aliasing is a phenomenon inherent to Doppler modalities which utilize intermittent sampling in which an insufficient sampling rate results in an inability to record direction and velocity accurately  How can you fix aliasing in ultrasound? Assignment Note some terms What is resolution of ultrasound image? Image resolution determines the clarity of the image. Such spatial resolution is dependent of axial and lateral resolution. Both of these are dependent on the frequency of the ultrasound. Axial Resolution Axial resolution is the ability to see the two structures that are side by side as separate and distinct when parallel to the beam. Axial resolution corresponds directly to the wave length characteristics of the Ultrasound wave. As frequency increases wave length shortens allowing for greater resolution. What we loose is penetration. Again as frequency increases penetration decreases. Higher frequencies also provide finer tissue grain or smoothness. A less grainy look. Lateral resolution In simple ultrasound systems Lateral resolution is attributed to physical focus characteristics of the crystal element. The concaved shape of the element provides focus to the beam and the width of the beam at any particular point effects the ability of the ultrasound system to resolve small objects that are side by side. Transverse resolution Transverse resolution is unique to the phase array probe. It is the ability of the probe to resolve objects side by side, as in lateral resolution, but in this case it is measured transverse to what would be considered the normal imaging plane. Again this is assuming simplest probe construction. Contrast Resolution The ability of the system to resolve adjacent bright reflectors is called contrast resolution. This is in small part due to the cumulative effects of axial and lateral resolution. The systems scan converter plays a large role is this characteristic. Temporal resolution Temporal resolution is the time from the beginning of one frame to the next; it represents the ability of the ultrasound system to distinguish between instantaneous events of rapidly moving structures, for example, during the cardiac cycle What determines temporal resolution? Temporal resolution is chiefly determined by the image frame rate of the system (measured in Hertz), which may vary depending on a number of factors. Which ultrasound imaging modality has the best temporal resolution? An ultrasound system with a longer pulse duration will generally have better temporal resolution. Two imaging systems produce acoustic pulses; one pulse is 0.4 µsec long and the other is 0.2 µsec long Diagnostic Ultrasonography ❖Displaying Monitor ❖Transducer / Probe ❖Keyboard ❖Probe Connector ❖Printer (B/W Color) Ultrasound Machines Function Diagnostic ultrasound machines are used to give images of structures within the body. This section does not deal with other kinds of machine (e.g. therapeutic and lithotripsy). The diagnostic machine probes, which produce the ultrasound, come in a variety of sizes and styles, each type being produced for a particular special use.  Some require a large trolley for all the parts of the unit, while the smallest come in a small box with only a audio loudspeaker as output. They may be found in cardiology, maternity, outpatients and radiology departments and will often have a printer attached for recording images. Unlike X-rays, ultrasound poses no danger to the human body. How it works The ultrasound probe contains a crystal that sends out bursts of high frequency vibrations that pass through gel and on through the body. Soft tissue and bone reflect echoes back to the probe, while pockets of liquid pass the ultrasound straight through.  The echoes are picked up and arranged into an image displayed on a screen. The machine offers a number of processing options for the signal and image and also allows the user to measure physical features displayed on the screen. This requires the machine to incorporate a computer. TRANSDUCERS Device that can change one form of energy into another. ❖Piezoelectric property ❖Piezoelectric material The necessary element for generating acoustic waves.  6. ELECTRONIC CALIPERS one pair at least, with quantitative readout. 7. ADD DATA IS POSSIBLE patient identification, hospital name, date of examination etc. 8. HARD COPY should be possible. 9. MONITOR at least 13 cm 10 cm (preferably larger) 10. STABILIZING should be able to stabilize voltage variation of /- 10. 11. Biometric tables (it may not be universal and should be adjusted for local standards. WHAT WE HAVE TO CHECK WHEN WE RECEIVE THE SCANER ❑SERVICE MANUAL ❑USERS MANUAL Checking every instruction in the manual may takes time. But if you do so, you will save time, money, and frustration.  CHECK LIST 1. Voltage setting should be compatible with the electrical supply. 2. Interference on the screen/ whit sparks. 3. Transducer and cables test. 4. Check the cursor / measuring length, 5. Check the accessibility of the biometrics or measurement tables.  IMAGE ARTIFACTS Any missing or distorted image that does not match the real image of the part being examined ARTIFACT'S CAUSES Acoustic characteristics of the tissues. Scanners settings. Lack of users experience. Defected part within the scanner. To confirm any suspected abnormality, Use multiple projections at different angles COMMON ARTIFACTS Cysts artifact (strong back-wall effect). Abdominal wall artifact. Gas artifact. Reverberation artifact. Incomplete imaging artifact. Gain artifact. Shadows artifact. DAILY CHECKS - Visual Visually inspects all transducers. Cable, cracked surface, punctured, discolored casing Visually inspect the power cords. Verify that the trackball and DGC controls appears clean and free from gel or other contaminants. Once the system is powered on Verify that the monitor displays CORRECTLY the connected transducers identification, current date, time. DAILY ADJUSTMENT FOCUS. DEPTH GAIN COMPENSATION. OVERALL GAIN. ZOOM. MONITOR (B/C).