Part III Flashcards
Multiplanar imaging
Surface rendering
3D Ultrasound
Employed in diagnosis for ex. Examinations of blood flow and fetal heart rate
Continuous Wave
Type of UTZ employed best in operational modes
Pulsed Wave
Type of UTZ employed that measure high ratio accurately
-no depth resolution
Continuous Wave
Type of UTZ employed that is transmitted in pulses
-good depth resolution
transmit time - cycle (on)
receive time - listening/dead time (off)
Pulsed Wave
No. Of separate packets of sound that are sent out every second
Units - Hertz, Hz, per sec
Pulse Repetition Frequency
Pulse duration plus listening time
Pulse Repetition Period
Period no of cycles
Pulse Duration
Percentage of time that the transducer is emitting soundwaves
Duty Factor
Structure in an image that does not directly correlate with the actual tissue being scanned
Ultrasound Artifacts
Occurs when an UTS beam encounters two strong parallel reflections
Reverberation Artifact
False echoes due to repeated reflections between two interfaces with high acoustic impedance mismatch
Spurious
Caused by the sound bouncing back and forth and then returning back to the receiver
Reverberation
Two subtypes of reverberation
Comet-tail artifact
Ring down artifact
Short-train of reverberations from an echogenic focus that has strong parallel reflections within it
Comet-tail artifact
A type of continuous sound wave returning to the transducer often caused by fluid trapped between gas bubbles
Ring down artifact
Appears as an area of low amplitude echoes (hypo or ana)
Behind a strongly attenuated tissue
-characterized by a signal void behind structures that strongly absorb or reflect ultrasonic waves
Acoustic Shadowing
Artifact useful in finding all types of calcifications
Acoustic shadowing
Aries from behind low attenuated object of interest provides increased echo
-appears as localized area of increased Cho amplitude behind an area of low attenuation
Acoustic Enhancement / Posterior Enhancement
Occurring at edges of rounded structures
Edge shadowing
Occurs when a reflective object located beyond the widened UTS beam, after the focal zone, create false detectable echoes that are displayed as overlapping the structure of intensity
Ultrasound beam width artifact
Avoid UTS beam width artifact by:
Adjust focal zone to the depth level interest
-by placing the transducer at the center of the object being studied
Occur due to the thickness of the beam and are similar to beam width artifact
Slice Thickness Artifact (Partial Volume Effect)
The energy within the UTS beam exists as several side lobes radiating at a no of angles from a central lobe
-arises from a strong reflection that is outside of the central beam and where the echoes are displayed as if they originated from with the central beam
Side Lobe Artifact
Result in a mirror image of a structure occurring in a UTS display
-arise due to specular reflections of the beam at a large smooth interface
Mirror Image Artifact
UTS Interactions
Scattering
Absorption
Defraction
Refraction
Reflection
Transmission
[UTS Interaction] soundwaves travel in all directions
Scattering
[UTS Interaction] happens when soundwaves pass through a tissue and the beam gradually decreases
Absorption
How to determine the strength of echo/intensity of UTS wave
HIGH AMPLITUDE, STRONGER ECHO, HIGH INTENSITY OF UTS
Where beam diverged or scattered but not in all directions
Defraction
Where we come to one of those boundaries between 2 different tissues and energy gets bent usually caused by change in speed
Refraction
Where its shows coming in and reflecting off of a flat surface that it would come in at an angle and goes off at the same angle
Reflection
Sound waves goes through the tissue
Transmission
UTS FACTORING
Gain
Time Gain Compensation
Mode Display
Depth
Resolution Expansion Selection (RES)
[UTS Factoring] Too low/too much may display false echoes
-darken image to emphasize bone
-intensity of returning echoes is amplified to produce a clearer image
Gain
Too much gain can cause [..]
Cystic structure look solid instead of fluid filled
If TGC is not present [..]
Tissue attenuation causes gradual loss of display deeper of tissues
Compensate for different values of echoes
Applies amplification or gain to compensate for the attenuation
TGC
[TGC Curve] to suppress or increase echoes in the near field
Near Gain
[TGC Curve] to suppress or increase echoes in the far filed
Far Gain
[TGC Curve] controls inward incline of the TGC
-used to display an even texture throughout the organ or structure under study
Slope
[TGC Curve] control used to delay the start of the slope
Delay
[TGC Curve] controls the point where the slope ends
Knee
Controls the deep portions of the FOV of the UTS image
Depth
If depth is too deep [..]
Minify the image
If depth is too superficial [..]
Magnify the image
Magnifies the part of the image
Zoom box
-particularly useful to display and measure small structures
Depth
Image Storages
Photographic Paper
Thermal Paper
Video Tape Recorder
VCD/DVD
Flash Drive
Digital Recording System or PACS
Simple emulsion film (1990s)
First image/storage recorder used
Photographic Paper
[thermal paper] cheapest, image disappears in 1 month
Type I
[thermal paper] expensive, better, glossy
Thermal Paper
