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FUS 1.4 The views aquired and artifacts

Transverse and longitudinal views:

There are two primary types of views in ultrasonography: transverse and longitudinal.

Transverse view (also known as axial or cross-sectional view): In a transverse view, the ultrasound probe is placed perpendicular to the long axis of the structure being imaged. This orientation produces images that are essentially cross-sections or “slices” of the tissue being examined.

Longitudinal view (also known as sagittal or longitudinal plane view): In a longitudinal view, the ultrasound probe is aligned parallel to the long axis of the structure being imaged. This orientation creates images that display the length and overall appearance of the tissues.

In many cases, both transverse and longitudinal views are used in conjunction to provide a more comprehensive assessment of the area of interest. By comparing and contrasting these two orientations, medical professionals can gain a better understanding of the size, shape, and internal structures and tissues, as well as identify any abnormalities that may be present.

Shifting from transverse and longitudinal view requires rotating the probe 90° in either a clockwise or counterclockwise direction.

[graphic outlining Transverse and longitudinal use]

[Video demonstrating transition from transverse to longitudinal view of the blood vessel in real time]

Techniques for maneuvering the ultrasound probe:

There are several techniques for maneuvering the ultrasound probe in order to obtain useful images of the underlying anatomy.
The pressure technique puts the target structure in place by applying vertical pressure to the transducer.
The alignment (sliding) technique moves the transducer antero-posteriorly and laterally aligning the area imaged with the target structure.
Tilting the transducer may place the angle Of the probe to the target closer to 90° and will increase the resolution.
Rotating the transducer will change the axis of the image from transverse to longitudinal.

[Video demonstrating these movements]

One’s ability to acquire useful ultrasound graphic images depends upon mastering these four techniques. This requires practice in order to master the hand eye coordination between navigating the probe on the patient and generating the ideal image on the computer screen of the structure of interest.

This requires practice on real patients. This is one of the reasons why learning ultrasound without applying the theory at the bedside is a pointless exercise. You must apply the theory while mastering the technical hand-eye coordination maneuvers of the ultrasound device itself In order to acquire useful images which can guide management dependably.

Artifacts:

An ultrasound artifact is an error or distortion in an ultrasound image that does not represent the actual anatomy or physiology of the tissue being examined. Artifacts can result from various factors, such as limitations in the ultrasound equipment, the nature of sound wave propagation, or the interaction between sound waves and the body’s tissues.

While some artifacts can be easily recognized and ignored, others can potentially lead to misinterpretation or incorrect diagnoses.

Here are some common ultrasound artifacts:

Reverberation artifact: This occurs when the ultrasound beam encounters a highly reflective surface, causing the sound waves to bounce back and forth between the transducer and the reflecting surface. This results in multiple, equally spaced, parallel lines on the image that do not correspond to the actual tissue structures.

Shadowing artifact: Shadowing occurs when the ultrasound beam encounters an object that absorbs or scatters the sound waves, such as a dense structure like bone or a calcified mass. Air can also block sound waves and cause shadowing below the air pocket. This reduces the amount of sound waves that can penetrate a structure, creating a dark area (or shadow) beneath it on the image.

Acoustic enhancement artifact: This occurs when the ultrasound beam passes through a structure with low attenuation, such as a fluid-filled cyst. The sound waves travel through the low-attenuation medium with minimal loss of energy, resulting in an area of increased brightness (or enhancement) beneath the structure.

[posterior enhancement diagram]
[posterior shadowing diagram]
[real picture of riverberation, shadowing and enhancement]

[recreated https://www.scienceabc.com/wp-content/uploads/2016/08/How-does-an-ultrasound-work.jpg]
[real examples of US echogenicity]

Doppler Mode:

The Doppler Effect is a phenomenon that occurs when there is a change in frequency and wavelength of a wave due to the relative motion between the source of the wave and the observer.
The Doppler effect is used in ultrasonography to visualize blood flow within vessels.
The color Doppler displays the vascular flow in red and blue superimposed ontop of the B-Mode black and white image. The vascular flow towards the transducer is in red and towards the opposite direction in blue.

The color will vary depending on the orientation of probe. Therefore you cannot deduce whether the vessel is an artery or vein by the color superimposed by the ultrasound device. You need to determine this through other anatomical clues seen on the image.

There is a subset of the Doppler mode called Power Doppler. In Power Doppler all doppler echoes as one color regardless of its direction and speed. The power Doppler is useful as it is more sensitive to smaller sized and lower-flow vessels. You can also see more artifacts by other types of motion within the tissue while using Power Doppler.

[doppler mode diagram]

 

The use of Doppler is very important within aesthetic medicine as it allows us to visualize the important vasculature we are mapping when we study the face with ultrasonography. Doppler mode allows us to improve the safety of our injections by recognizing the anatomical locations of significant blood vessels within the face. By utilizing these techniques, we can also treat vascular complications with increased efficacy.