Ch 12 Principle 2 Flashcards
What are the 2 principles of operation?
-Principle 1
-Principle 2
Explain sonography from the 1960s - the future
60s: introduced to A & M modes
70s: introduced to static grey scale 2D imaging
Late 70s: introduced to real time grey scale 2D with image memory
80s: introduced to color + spectral doppler (huge breakthrough to qualitatively and quantitatively assess blood flow and hemodynamics)
90s: introduced to static 3D imaging
2000s: this 3D imaging improved to real time 3D/4D. This was the first time we had the ability to manipulate 3D structures throughout time (cardiac cycle) and assess structures of interest from multiple angles. Refined 3D/4D US imaging of the fetus.
2010s: u/s contrast agents became widespread to improve endocardial definition for technically difficult cases and to assess for WMA and apical HCM
2020 (present): we are looking at principle 2 of how echoes are generated, vector flow imaging, cardiac strain imaging + POCUS
Future: we will see artificial intelligence, machine learning, deep learning, and VR/AR imaging reconstruction (we are already experiencing AI with measuring)
Differentiate principle 1 vs principle 2?
Principle 1:
-one to one correspondence
-higher frequency = reduced penetration
-multiple focuses = reduced temporal resolution
Principle 2:
-fewer pulses required
-focusing is NOT required, yet entire image is in focus
-fewer beams = higher FR = increases temporal resolution
-contrast resolution + penetration is improved
-artifacts reduced
Principle 1 + 2 are both composed of what 3 things?
- Beam former
- Signal processor
- Display
(3. is either the image processor in principle 1, or image former in principle 2)
With principle 2, the image processor is replaced by what?
The image former
(this now directs, focuses + apodizes the reception beam)
Does the beam former + signal processor in principle 2 function similar to principle 1?
Yes!
What is the image former?
-Massive, high speed, parallel processor that sorts out the echoes + places them in image memory in their proper location
-Is a retrospective beam forming process (meaning an echo from a given location arrives at the elements of a probe in a specific pattern depending on its original location)
Explain virtual beam forming with principle 2?
-It is still necessary, but no longer coupled directly to displayed scan lines
-It is accomplished by massive, computational postprocessing utilizing graphics processing units (GPUs)
With virtual beam forming, retrospective computed beam forming can be imagined in transmission + reception forms, explain them?
Virtual transmission beam:
-An imaginary laser
-A thin transmitted u/s beam that can be thought of as producing the excellent detail resolution in the image
Virtual reception beam:
-An imaginary reception beam that can be thought of as determining the echo produced at each pixel location in the image
Is principle 1 or 2 better?
Principle 2! It yields improvement in nearly every aspect of sonographic, anatomic imaging!
List 3 functions of the image former?
-Stores echo info received from the signal processor for each emitted pulse
-Sorts the combined echo info to determine the precise echo from each pixel location + store
-Sends stored echo info to the display
How is detail resolution with virtual beam forming improved?
No need for focus on imaging anymore! The entire image is in focus!
How is temporal resolution with virtual beam forming improved?
Principle 1: required many scan lines to form an image (decreasing FR)
Principle 2: no direct relationship b/w # of scan lines + # of pulses to produce an image
(FR determined by computational, retrospective beam forming + speed of the GPU)
Detail resolution + FR are determined by what in principle 2?
By computational processes + speed of processors
How is contrast resolution with virtual beam forming improved?
Virtual beams are thinner than conventional beams
(this decreases chance of slice thickness artifact)
