A full Basic FATE examination includes images of the heart and pleura obtained from four different positions, or “windows”, in the thorax
From these positions 6 imaging views can be achieved:
– Position 1: Subcostal 4-chamber view
– Position 2: Apical 4-chamber view
– Position 3: Parasternal views: the long-axis and short-axis view
– Position 4: Pleural views. Right pleura and left pleura
This module will give an overview of these 6 imaging views and how to achieve them
At the end of module 4 (position 1) inferior vena cava (IVC) has been added as a service for those of you who want to learn IVC now
IVC is one of the extended views and therefore a part of Advanced FATE
The sector angle is important as it affects the frame rate dramatically
A narrow sector angle (width) allows either (1) a higher frame rate (the time required to build the image is reduced by reducing the number of beams for a whole sector) or (2) a better lateral resolution (the line density can be increased).
A higher frame rate increases temporal resolution
A higher line density increases lateral resolution
By using a sector just wide enough to include all relevant details, the capacity of the ultrasound system capacity is best used
The ultrasound image can be optimised by adjusting different user controls
The most important user controls are:
– Gain
– Depth
– Sector angle
– Time Gain Compensation
These user controls will be explained in greater detail in the next slides
It is important that you become familiar with these user controls on your own ultrasound system so you know how to optimise the ultrasound image in order to improve the diagnostic value of the images
This user control is similar to the brightness control of a television set
Some of the emitted echo signal is reflected back to the probe when the emitted beam hits a reflective interface in the tissue
The echo signal returning from the tissue is converted to an electronic signal by the probe
This signal is very weak and has to be amplified before it is processed into a greyscale image. The signal amplification is called “gain”
Undergain: If the user sets the gain control too low, the amplification of the electrical signals is too small, and the 2D greyscale image on the screen becomes too dark.
Overgain: If the gain control is set too high, the 2D greyscale image becomes too bright
During a “clean” rotation, the direction of the tail of the transducer should be kept 100% stable
Rotation can be:
– Right = clockwise
– Left = counterclockwise
For rotational instructions we do not make use of a secondary reference point
Example:
To obtain the correct subcostal 4 chamber view, alignment with the longitudinal axis of the heart often requires 10-20 degrees counterclockwise rotation
You will therefore often hear the supervisor saying: “Rotate the probe counterclockwise or rotate the transducer to the left”