17-11-21 - Basics of Ultrasound Flashcards
What are hertz?
What are they defined as?
What is diagnostic sonography?
What frequency do diagnostic sonography use?
- The hertz (Hz) is the unit of frequency in the international system of units (SI)
- Hertz is defined as the number of cycles per second
- Diagnostic sonography is the use of medical ultrasound for medical diagnosis
- Diagnostic sonography generally uses frequencies of 1-20MHz (x10^6)
How do diagnostic ultrasounds work?
what results in attentuation
What can attenuation limit/ when is it greater ?
- Ultrasound uses short high frequency sound pulses that are transmitted into the body
- These sound pulses can be reflected, scattered, refracted, or absorbed
- The combined effects of reflection, refraction and absorption result in attenuation (reduction of amplitude/force) in the intensity of the sound pulse as it travels through the mater
- Attenuation limits depth of imagine and is greater at higher transmit frequencies
What are 3 advantages of ultrasound?
What are 3 disadvantages of ultrasound?
• Advantages of ultrasound:
1) Ultrasound is safe
2) No ionizing radiation
3) The equipment required is portable, compact, and relatively inexpensive
• Disadvantages of ultrasound
1) Highly operator dependent
2) Structures surrounded by bone, such as the brain and spinal cord, do not give clinically useful images
3) The attenuation of the ultrasound signal at the air/tissue boundaries means that the technique is not suitable for imaging structures in the lung or abdominal organs obscured by gas in the overlying bowel
What is the role of ultrasound transducers/probes?
What are the 3 different types of transducers?
What frequencies do they function at?
- Ultrasound transducers produce and detect ultrasound
- Ultrasound transducers are capable of sending an ultrasound, detecting the sound, and converting it into an electrical signal to be diagnosed
• 3 different types of transducers/probes:
1) Linear array probe – 7 - 11MHz
2) Curved array probe – 2 - 5 MHz
3) Phased array probe – 1 – 5MHz
What are piezoelectric crystals?
What are they used for in diagnostic sonography?
How does this work?
How do higher amplitude echoes affect these crystals?
- Piezoelectric crystals are ceramic crystals that deform and vibrate when they are electronically stimulated
- They are used in diagnostic sonography to generate an electric pulse that is processed into an image
- Echoes that return to the transducer distort the crystal elements and generate an electric pulse that is processed into an image
- High-amplitude echoes produce greater crystal deformation and generate a larger electronic voltage
- These displayed on the image as brighter pixels than low-amplitude echoes
- Because of this, standard 2D grey-scale images are often referred to as B-mode (brightness mode) Images
linear ray
type of probe
resolution
depth
image type
HFL38/13-6 what does this code mean => features
High frequency probe
Good image resolution
Low depth of imaging
Flat footprint produces undistorted images
13-6 MHz Range + 38mm Footprint
What are curved-array transducers?
frequency
image res
depth
what for
Aka Curvilinear Probe
Low Frequency Probe
Low image resolution
Good depth of imaging – good for abdominal scan
Slight distortion of images
Smaller curvilinear probes exist for intraluminal scanning
How does the phased-array transducer work?
What type of image format is produced?
Where is it able to scan?
Low US wave is generated from the centre of the footprint
This allows a small probe but large scanning area
Image produced is a ‘sector image’
By having a small footprint, the probe can scan in small or awkward areas
Example: Trans-thoracic echocardiography (between ribs
intraluminal
Where are they used?
what are the advantages/ what do they allow?
To be used in various lumens / orifices (Endovaginal, Endorectal, oesophageal)
Have several advantages
Places the probe close to area to be imaged
Overcomes poor imaging resulting from overlying structures (e.g. adipose tissue)
Allows use of high-frequency (higher resolution images)
What is A-mode imaging (amplitude mode)?
How is it represented?
- A-mode imagine (Amplitude mode) is a method of supplying echoes acquired in 1 dimension
- So, in A-mode imaging, you essentially get a graph where the horizontal axis shows depth and the vertical axis shows the strength of the echo.
What is B-mode (Brightness/ 2D mode)?
What are brightness and position on the screen determined by?
Aka Brightness / 2-D Mode
This is the most commonly used US mode, which produces a two-dimensional image
A ‘spike’ from a returning wave is represented as a pixel (or a dot)
The brightness is determined by the amplitude of the signal
Its position on screen is determined by depth of returning signal
What is echogenicity?
What are the 4 different types?
anechoic
hypoechoic
isoechoic
hyperechoic
What area do various structures fall into?
- Echogenicity is the ability to bounce an echo e.g return the signal in ultrasound examinations
-> anaechoic
Definition: No echo is returned.
Appearance: Appears black on ultrasound images.
Examples: Fluid-filled structures (e.g., cysts, blood, urine).
Common Cases:
Blood
Urine
Cysts
Abscesses (pus inside can appear anechoic or hypoechoic)
Isoechoic (Same as surrounding tissue)
isoechoic
Definition: Produces echoes similar to the surrounding tissue.
Appearance: Appears the same shade of grey as the neighboring tissue.
Examples:
Some soft tissues or organs with similar tissue composition.
Abscesses (sometimes may be isoechoic with the surrounding skin tissue).
Hypoechoic (Dark Grey)
Definition: Produces fewer echoes than surrounding tissues, making the area appear darker.
Appearance: Appears darker than the surrounding tissue.
Examples:
Pus in an abscess (may also appear anechoic in some cases).
Tumors or abnormal growths (e.g., some cancers, lymph nodes).
Hyperechoic (White or Bright)
Definition: Reflects a higher amount of sound, producing a bright or white appearance.
Appearance: Appears white or bright on the ultrasound image, often with a shadow behind.
Examples:
Bone
Gallstones
Metallic objects (e.g., surgical clips, foreign bodies).
What are the 3 different types of Doppler Ultrasound?
What do they each do?
colour = direction and magnitude of blood flow
power = visualization of small vessels but no directional info
pulsed = sampling volume positioned in a vessel
What does BART ultrasound show?
• BART ultrasound shows the movement of blood in colours, with blue being away from the probe and red being towards the probe
What is m-mode (motion mode) designed for?
How does it work?
What is this mode important for the study and documentation of?
- Motion mode is designed to document and analyse tissue motion
- Using the S2 image is a guide, a particular scan line is selected to correspond to the moving structure of interest
- This mode is particularly important in studying cardiac valve and wall motion, and in documenting mental foetal heart rate activity
How does 3D ultrasound imaging work?
What is the biggest clinical application of 3D ultrasound imaging?
- Data for 3D sonography are acquired as a stack of parallel cross sections with the use of a 2D scanner
- The biggest clinical application of 3D ultrasound is in the evaluation of gynaecologic and foetal anatomy
What does the gain control adjust on Ultrasound machines?
What effect does too little and too much gain have on the image?
- The gain control adjusts the amplification of the returning acoustic signals and is used to optimise the US image
- Reduce gain produces a dark image and detail is masked
- Too much gain produces a white image and detail is saturated?
What is the direction of the orientation marker on the probe when performing a longitudinal and transverse scan?
- The orientation marker on the transduce is directed cephalad (towards the head) when performing a longitudinal scan
- It is directed towards the right side of the patient when performing a transverse scan
How does acoustic enhancement work?
What are examples of where it occurs?
- Some structures allow sound to pass through them more easily than others.
- The most dramatic example is watery fluid, such as in an effusion or in a cyst.
- Because only a minimal amount of energy is absorbed by the fluid, the region that lies behind will receive more sound than the processor expects for that depth.
- This area will therefore appear uniformly brighter.
- This effect is called Enhancement.
- A good example is the effect of the bladder, acting as a window to deeper tissues.
What are the 4 manipulation manoeuvres of the US probe?
PART
How should the probe be orientated to the structure of interest?
- The probe should usually be at 90 degrees to the structure of interest, as this provides the maximum return echo
What is anisotropy?
Why may this be problematic?
What is an example of this?
What is the anisotropic effect dependent upon?
- What It Means:
Anisotropy occurs when the structure being examined (like a tendon or muscle) appears different depending on the angle at which the ultrasound beam is directed at it.
This happens because the tissue has a directional or anisotropic property, meaning its behavior changes when observed from different angles. Tendons, for instance, have fibers that run in one direction, and their appearance in ultrasound imaging will vary depending on how the sound waves interact with these fibers.
The Impact on Diagnosis:
Effect on Tendons: When an ultrasound beam is not perpendicular (at a 90-degree angle) to a tendon, the image may appear hypoechoic (darker) or more solid than it actually is. This might falsely suggest a condition like tendinosis (degeneration) or a tear when, in fact, the tendon is normal.
False Diagnosis: The result of anisotropy can lead to misinterpretation of the ultrasound, causing a false diagnosis of injury or pathology, even though the tissue is healthy.
