Settings of the echocardiography machine
Modern echocardiography machines have tens of buttons and adjusting them affects image quality dramatically. Settings have to be optimized individually in our patients. With wrong settings important findings will be not documented and can be overlooked.
As for ordinary PC monitors, echo monitors can be calibrated only in the room in which the scanning will be performed. A bright room will have different calibration results than a dark room. It is important because when it’s not calibrated bright enough you may lose low-intensity signals and if it’s too bright signals from strong reflectors may be over-represented. With correct calibration you can use all the brightness range the monitor can display (Figure 1).
Figure 1. Correct monitor calibration.
Machine settings can be saved as presets. For different transducers, patients and structures different presets can be created. In many devices a number of predefined presets is already available for selection and modification.
Output power determines the energy transmitted by the transducer. Normally power is set up on maximum level to improve signal to noise ratio.
Gain is a postprocessing setting. This means that the information in the stored image is the same in different gain settings. However, the information is differently presented to our eyes  (Figure 2).
Figure 2. Effect of gain setting on image.
In general if the surrounding is bright (in emergency room, operating theatre), it is better to scan with higher gain in order to be able to detect some important findings.
Time-gain compensation allows adjusting gain setting on different depths to compensate for ultrasound attenuation and may be set up as a column of sliding knobs (Figure 3). Many newer machines have an option for automatic adjustment of gain throughout the image.
Compression is also a postprocessing setting. Changes of compression alter the number of grey shades in the image. The lower the compression the less the number of shades with the consequence of more contrast appearance (Figure 4). The disadvantage is the worse visualization of structures with low intensity reflection.
Reject control is used to eliminate low-level artificial signals displayed in the image as noise. Care should be taken not to filter important low-intensity signals from pathologic conditions.
Frequency of ultrasound is directly related to spatial resolution and inversely related to penetration. The main practical conclusion: the worse the acoustic window, the lower the frequency is to be used (Figure 5).
Harmonic imaging is now routinely used in most of the studies which resulted in decrease of artifacts. It should be noted that if you increase frequency to improve spatial resolution your system may switch from harmonic to fundamental imaging mode.
Normally depth should be high enough to include whole heart in a particular view. For example quality of 4-chamber view can be defined if the left atrium is completely visualized. But the larger the depth, the longer it takes for the machine to receive returning echoes, which can affect the frame rate of the image
Wide imaging sector width gives better overview of cardiac structure especially in patients with enlarged hearts. The main disadvantage is less spatial resolution and frame rate due to physics of ultrasound.
Frame rate determines the temporal resolution. High frame rate is necessary for visualization of mobile floating structures, for anatomic M-mode and for speckle tracking analysis. It should be noted that in some systems high frame rate results in decreased spatial resolution (Figure 6).
The Focus control gives opportunity to optimize the lateral resolution at a given depth. In some systems it is possible to set 2 focus positions simultaneously. But this setting leads to markedly decreased frame rate (Figure 7).
The zoom function allows magnifying region of interest on the screen. It is important to distinguish between ordinary zoom when the image appears larger, but the resolution of the magnified area does not change, and high resolution zoom when the resolution in the region of interest is increased. This function is important when performing precise measures such as left ventricular outflow tract or PISA radius.
- ↑ http://blog.gpsmed.com/2012/03/do-it-yourself-easy-ultrasound-optimization-quick-tip.html
- ↑ http://assets.escardio.org/Assets/Presentations/OTHER2010/EAE-clinical-application-echo/2.Voigt-set-up-echo-machine.pdf
- ↑ http://www.escardio.org/congresses/euroecho2010/Documents/teaching-course-slides/euroecho2010-image-optimization-hagendorff-100.pdf