Key words ultrasound - Methods & techniques - B-mode - resolution - image quality - image optimization
Introduction
“Knobology” describes the pertinent knowledge and use of ultrasound
(US) equipment to achieve the best settings and applications for patient care. US
does not require ionizing radiation and is an indispensable imaging method in
medical diagnostics. A major limitation is that ultrasonic waves are transmitted
neither through bone nor air, which restricts its use. Apart from good knowledge of
anatomical structures and examination techniques, knowledge of how to achieve the
correct machine adjustments for the best image quality and to maximize the potential
of US equipment functions is essential [1 ]. In the
following document, we present techniques to optimize general device settings and
to
achieve optimal use of B-mode.
How to Manually Boot, On/Off
How to Manually Boot, On/Off
The US system is powered on and off using the partial power on/off control
located on the control panel. A steady color indicates that the power is on. In some
systems, flashing color indicates that it is plugged into the power supply and the
circuit breaker on the US system is in the ON position. No color indicates that the
power is off, unplugged from a power supply, or the circuit breaker on the US system
is in the OFF position. Modern mobile and handheld US systems are equipped with a
battery, which is automatically charged when the system is on power supply. Due to
complex software functions, booting and shutting down the system may take some time.
To avoid damage or disturbances of the US system, the power supply should not be
switched off while the US system is in the process of booting up or shutting
down.
Monitor
The monitor presents the information generated by the US exam and makes it available
for the user to review. The examination room should be darkened as much as possible
in order to avoid a loss of contrast on the screen due to incident light. It should
also be considered that the human eye needs about 20–30 minutes to achieve
complete dark adaptation. If the room is entered or darkened shortly before the
examination, the viewer of the US image could miss details that can only be
perceived after dark adaptation [2 ]
[3 ]. The position of the monitor should allow for a
near-perpendicular viewing angle for the examiner. An overly flat angle leads to a
loss of contrast perception. Finally, the display technology has to be considered:
A
liquid-crystal display (LCD) is a flat-panel display thought superior to the
cathode-ray tube (CRT) monitors used in the past [4 ].
The use of organic light emitting diodes (OLED) is a newer flat light-emitting
technology that provides increased contrast, but is still very expensive and
currently only installed in a few devices [5 ]. Some
mobile and handheld US devices are equipped with touchpad monitors, which allow
partial or complete management of system functions.
The Right Transducer
Crystals located at the tip of the transducer are agitated by an electrical current
and generate ultrasonic waves, which are transmitted into tissue via a coupling gel
between the probe and the patient’s skin. This process is based on the
principle of the piezoelectric effect [6 ]. The same
crystals serve as receivers of returning ultrasonic waves, which means that
soundwaves reflected back from the tissue are absorbed by the transducer crystals
and then generate specific electrical signals. These signals are decoded and
processed into imaging information. While millions of soundwaves per second are
produced when the crystal is agitated by a current and functions as a transmitter,
over 99% of the time is allocated to receiving the returning soundwaves.
This assures that all returning echoes are registered, because it takes longer to
receive returning waves from greater depths. The echoes of the emitted beam are
usually scattered and reflected when encountering inhomogeneous tissue or impedance
jumps at the transition between two tissue types or structures. This will create
returning waves with different strengths and transit times. This information is
evaluated by the US machine software and results in the image displayed on the
monitor [7 ].
Three different transducer types are commonly available. They complement each other
and serve different requirements with regard to body region, structural
representation, depth penetration and field of view. This is made possible by
variances in geometry, crystal arrangement and crystal activation.
Convex transducers (curved linear array) are typically used in abdominal and pelvic
sonography. Crystals are arranged next to each other along a curved (convex)
surface. This enables a widened field of view, especially in the depth display, but
also assures good near field resolution. The resulting image is cone-shaped with the
diameter increasing with the depth. Curved transducers with a small aperture and
wide scanning field are available for transcutaneous, intraoperative, and
intracavitary use. Variation of the width of the scanning field is possible with
modern convex transducers.
Linear transducers (linear array) use crystals positioned next to each other in a
straight line. Thus, the ultrasonic waves are arranged in parallel and produce a
higher and more uniform resolution at the expense of depth penetration as high
frequencies are used. The output image is rectangular.
Vector array transducers are a variety of classic linear array transducers that
enable trapezoidal widening of the acoustic window. This worsens the resolution at
a
depth, but expands the width of the image defined by the aperture of the transducer.
The technology allows for the depiction of extended structures and is used to
evaluate superficial structures with high resolution such as the thyroid gland,
superficial vessels, intestines, soft tissues, and joints. However, it produces more
artifacts when applied to curved parts of the body [7 ]. An additional function of vector array transducers is image steering,
which denotes lateral canting of the US window by up to 30 degrees. This may be
useful to examine superficial structures which otherwise would be hidden in the
acoustic shadow of totally reflecting structures (e. g. ribs).
Sector transducers (phased array) use smaller and narrower individual crystal
elements that are arranged in a horizontal or circular pattern and have a smaller
footprint. The functional difference lies in the control of the individual crystal
sections. Through a slight time and phase offset, spherical sound fields are
generated, which result in a fan- or pie-shaped image. Thus, this type of transducer
is more effective than the convex transducer for depth display but loses a lot of
information in the near field. The dimensions of the transducer facilitate its use
for narrow acoustic windows as they occur in intracavitary sonography,
echocardiography and neurosonography [8 ]. An important
advantage of sector transducers is the application of continuous wave (cw) Doppler
US, which is not possible using the other types of US transducers.
In addition to the conventional transducers that are connected to the US machine via
a cord, the use of newer wireless probes might become more prominent, allowing for
a
more comfortable exam, especially in the field of interventional imaging.
Furthermore, smaller and more mobile US devices have been developed [9 ]
[10 ].
Image Quality
Image quality depends on several factors. Above all, the transducer must be
adequately coupled to the patient with a sufficient amount of coupling gel. This
avoids interposition of air between the transducer and the skin and ensures that all
crystals are able to transmit and receive soundwaves. To achieve optimal image
quality, adequate depth penetration, image width, spatial and temporal resolution,
image contrast, artifact suppression [11 ]
[12 ], and application of zoom are relevant. [7 ]
[13 ] Hence, the best possible image parameter settings
should be achieved. The above-mentioned factors will be discussed in more detail in
the following sections. The goal should be to generate an image that is as realistic
and aesthetic as possible, which is representative of the depicted anatomy and
provides a meaningful clinical contribution.
Depth Penetration
Depth penetration influences the size of the examination window and the reproduction
scale. It depends on transducer frequency, transmission power, and Tissue Harmonic
Imaging (THI). Several aspects should be considered when determining depth
penetration. A high depth penetration is indispensable to achieve an overview of the
anatomy but goes hand in hand with slower image acquisition because an echo signal
must be sent/received for each additional image line. The tissue of the
patient is an important factor influencing this process since the speed of sound
depends on tissue density. In addition, the layer thickness rises with increasing
depth penetration, which further deteriorates the resolution. Lastly, the
signal-to-noise ratio should be mentioned. This ratio increases with decreasing
transmission frequency and makes it more difficult to distinguish an actual
ultrasonic signal from background noise artifacts. Therefore, a lower depth
penetration improves the representation of moving structures as well as smooth image
reproduction during transducer movements. For these reasons, the selected depth
should be deeper than the structures of interest ([Fig.
1 ]). Finally, a more lateral insertion of the sound window (B-image angle)
leads to a higher temporal resolution.
Fig. 1 US examination of the pancreas with inadequate a and
adequate b selection of depth penetration. The field of interest
(pancreas) is in the middle to the lower third of the adequate image b) but
in the upper third of the inadequate image example a .
Zoom
Zoom can help to enlarge an image section on the monitor. The read-write zoom has
no influence on depth penetration. It depends on the configuration of the
transducer used, and thus on the maximum possible range of the ultrasonic waves.
If, however, a section of the image is zoomed into, the echoes outside the
remaining examination area now no longer have to be evaluated, thus improving
temporal resolution as well as line density. It should be noted that by
comparison, a simple magnification of a frozen image does not gain any
advantages, as in digital image processing.
Resolution
Spatial resolution
It is essential to distinguish between different terms used for image resolution,
as they describe completely different aspects of US.
Ultrasonic waves propagate in the extended axis of the transducer, which is
therefore also referred to as the axial direction. The axial resolution ([Fig. 2 ]), depends on the nominal transducer
frequency and pulse length, which both determine the axial distance at which two
individual points can still be distinguished.
Fig. 2 Overview of ultrasonic axes a and examples for
varying line density. Examination of the right liver lobe with line
density at 1/8 b , 4/8 c and 8/8
d .
The second plane, called lateral resolution, defines the discrimination of two
points perpendicular to the beam propagation ([Fig.
2 ]). It is influenced by beam width and the transducer’s line
density. The latter is the number of pulses (scan lines) being laterally
transduced. The examiner can adjust the line density to affect the resolution,
but the maximum value is hardware-limited. A lower line density produces a
smoother image and might be advantageous for vascular delineation,
musculoskeletal tissue definition, or structures with curved or irregular
borders (a stronger reflection occurs with a perpendicular angle of incidence).
It should be further noted that ultrasonic signals must be transmitted and
received for thinner and thus more lines, which inevitably decreases the frame
rate (temporal resolution). Lateral resolution may be improved by narrowing the
acoustic window of convex transducers. Due to its manual widening (“wide
view”, “trapezoid image”) the anatomical overview
improves at the cost of lateral resolution. Some US systems also offer a
“speed of sound correction” to improve lateral resolution
depending on the particular characteristics of the insonated tissue
(e. g. breast vs. vessels) [14 ].
Although a two-dimensional image is displayed on the screen, it represents the
projection of a three-dimensional structure ([Fig.
2a ]). Therefore, the user must also consider how much information of
the Z-axis is summed up to an "infinitely" flat image. In
ultrasonography, this plane is called layer thickness and depends on the
selected transducer, image section, focus, and examination mode used
(e. g. B-mode, Doppler, or contrast-enhanced US). The layer thickness in
Doppler or contrast-enhanced US is higher than in B-mode. At low
frequencies/high depth penetration, the layer thickness can be up to
several centimeters and thus might create summation artifacts. Therefore, it is
crucial to be aware of the difference between layer thickness and line
density.
Transducer frequency
The transducer frequency is calculated from the ratio of speed and wavelength.
Since higher frequencies have a shorter wavelength and the wavelength is
reciprocally proportional to the resolution, the highest possible frequency
should always be selected (“try high”). This setting is limited
by the decreasing depth penetration that results from an increase in frequency
([Fig. 3 ]). The nominal frequencies of the
transducers are between 1 and 25 MHz and are generally determined by the
transducer itself. Thus, convex transducers are usually working at 2–8
MHz. Depending on the device, either a subrange (e. g. low, medium,
high) or a defined center frequency (e. g. resolution mode vs.
penetration mode or the center frequency number) can be set within this range to
influence depth penetration and resolution.
Fig. 3 Examination of the gallbladder and hepatic hilum using a
linear transducer in a slim person: High spatial resolution and adequate
depth penetration at lowest possible frequency a and loss of
depth penetration using a (too) high frequency b .
Tissue harmonic imaging
Tissue Harmonic Imaging (THI) improves the contrast ratio through increased
lateral resolution and reduced background noise by promoting the reduction of
side lobe artifacts [11 ] ([Fig. 4 ]). These are lateral incident artifact
echoes, which are mostly missing so-called harmonics. Harmonics are partials,
which are caused by a distortion of transmitted sound waves and arise in the
area of highest pressure, i. e. in the central axis area of the
transmitting lobe. THI only registers ultrasonic waves that contain harmonics
and thus simultaneously filters out the side lobe artifacts. In the case of
“Second Harmonic Imaging”, the second harmonic wave is used,
which corresponds to twice the underlying transmission frequency [15 ]
[16 ]
[17 ]. Disadvantages of the past are no longer
relevant today due to technology improvements, which is why it is typically not
practical to switch off THI [18 ].
Fig. 4 THI improves the contrast ratio through increased lateral
resolution and reduced background noise by promoting the reduction of
side lobe artifacts. The spleen is shown with a and without THI
b .
Pulse inversion is a technique to compensate the limited bandwidths of THI.
Following the normal ultrasonic beam, an inverted replica is sent and the
received signals are analyzed. Pulse inversion works at all received frequencies
and is therefore able to improve the resolution [13 ].
Compounding
Compounding is a tool for image optimization that combines multiple images
resulting from multiple aperture positions (spatial compounding) or multiple
transmission frequencies (frequency compounding) into a single composite frame
in real time. This technique suppresses background noise, speckles, and
artifacts [11 ] and improves resolution and contour
display. At the same time, the image looks greasy and diagnostically valuable
enhancements as well as shadowing artifacts may be lost. Thus, compounding is
reasonable only in a limited and targeted way. In addition, it should be used
according to subjective preference. Compounding consists of three different
types: Spatial compounding can be achieved using several techniques, including
combination of different insonation angles (beam steering), transducer rotation,
and varying transducer positions . Frequency compounding can be achieved by
using multiple sources at varying frequencies, or by taking several images at
different frequency sub-bands [19 ]
[20 ]
[21 ]
[22 ]. In strain compounding, multiple strains are
created by external forces inducing tissue motion [23 ]. The signal-to-noise ratio can be improved through
processing.
Focal zone
The focal zone or plane is the part of the US beam where its diameter is focused
and narrowest. Proximal to this zone, the beam diameter is wider. It increases
again when travelling past this zone. This causes a thicker layer width and
decreased image resolution. Since the layer thickness is lowest in the focus
area, it should always be at the level of interest or start just above the
structure to be displayed. In the case of a cyst, the transition from the
parenchyma to the fluid space to be visualized is located at the beginning of
the focus area. One could argue that the echoes exiting the cyst also pass
through an impedance jump required for the diagnosis. However, the principle
applies that the layer thickness increases with increasing distance to the
transducer, even if the focus zone is set. Classically, US devices offer one
focal plane, while newer machines allow two focal planes or even a continuous
focus (sometimes called eFocus or range focus) ([Fig.
5 ]). An increasing number of foci lowers the frame rate.
Fig. 5 Classically, US devices offer one focal plane a, b .
Newer machines allow two or more focal planes or even a continuous focus
(sometimes called eFocus) c . Examination of the pancreas using a
near focus zone a , a far focus zone b , and eFocus
c .
Sectoral width
Reducing the sectoral width will improve lateral resolution by narrowing the
acoustic window and can be altered when using convex probes. In most scanners,
this can be easily performed by pressing the “select” button and
using the trackball to alter the image width. Otherwise, you may find this on a
separate button either on the console or touch screen. An example of different
sectoral widths is shown in [Fig. 6 ].
Fig. 6 US examination of the liver with wide a and narrow
b sectoral width.
Temporal resolution
In addition to the spatial resolution, temporal resolution also has a
considerable impact on image quality. Influencing factors are frames per second,
line density, image section, zoom and persistence (persist function). It should
be mentioned that with newer devices, image section and zoom are no longer of
great relevance due to much higher computing power. Accordingly, a high temporal
resolution can be achieved even with large image sections. Frame rate (frames
per second, FPS) must be adapted to the structure of interest. For example, a
low frame rate used with convex transducers in the abdomen may be sufficient but
would produce very blurred images if used with sector transducers in
echocardiography ([Fig. 7 ]).
Fig. 7 Echocardiography using low persistence a and high
persistence b .
Persistence defines how much of the previous image is taken over into the current
frame. This makes the resulting live image appear smoother and less wobbly. This
can be useful to a certain extent, especially when working with the US machine
for a long time. At the same time, relevant abnormalities can be concealed and a
low persistence must be selected, especially for fast-moving structures such as
the heart [24 ].
Contrast resolution
Numerous settings influence contrast resolution and should be adjusted
accordingly for optimum image quality. These include nominal frequency,
brightness, dynamic range, gray maps/curves and B-color [24 ].
Dynamic range
Dynamic range defines the echo strengths shown on the monitor, comparable to
the windowing technique in computed tomography. Each received US wave is
assigned a gray value and usually displayed on the monitor with 256
gradations. A higher dynamic range would be technically conceivable,
especially by the transducer (150 dB), but too broad to be presented on the
display. Furthermore, it would be redundant, because the human eye can only
distinguish 50–60 of these gradations. A high dynamic range offers
more information about the echo patterns, appears brighter and softer and is
therefore preferable for representing organ parenchyma. For anechoic imaging
of vessels, a low dynamic range is favored. Accordingly, a low dynamic range
image results in a more “black-and-white” like shape and
thus, higher contrast ([Fig. 8 ]). Dynamic
range is available on live or frozen images.
Fig. 8 Imaging of the right liver lobe and right kidney using
a low dynamic range with high contrast and coarse echo pattern
a and high dynamic range with adequate representation of
the whole range of parenchymal echos of both parenchymal organs
b .
Gray maps/curves
Whereas dynamic range defines the total number of gray scales displayed, gray
maps determine which ultrasonic signal intensity is displayed in which gray
scale (how bright/dark). Typically, an S-shaped curve is used
instead of a linear correlation. This increases contrast at intensities that
often occur in US images. In general, it is possible to choose between many
different gray maps but this is only necessary in rare cases. Gray maps may
be adjusted on live or frozen images ([Fig.
9 ]).
Fig. 9 Imaging of right liver lobe and contracted gallbladder
using a linear correlated gray map a and an S-shape gray map
b .
Brightness
The overall brightness of the image can be adjusted by alternating gain or
depth dependently via a manual control. Time gain control
(TGC)/depth gain control (DGC) compensates for the naturally weaker
amplitudes from deeper layers of the image. In standard settings, the depth
compensation works well, but must be reduced for structures that hardly
attenuate the sound (e. g. liquids). If a high-end machine is used,
the adjustments are set automatically where necessary.
The signal gain can also be configured. It controls the image brightness and
should be selected so that structures of low echogenicity (e. g.
liquids) are displayed in black, and highly echogenic structures such as
bones are in white. If this setting is unbalanced, it will lead to a loss of
detail due to unused gray scales. When working with an exaggerated signal
amplification, the sound lobe diameter analyzed by the device increases but
the spatial resolution in the layer thickness plane decreases.
Speckle reduction
Speckle reduction (SR) uses algorithms to reduce the graininess of the image
(so-called “speckle noise”). This phenomenon is caused by
alternating positive and negative pressure phases in the course of the
ultrasonic wave, which causes brighter pixels through superposition and
darker pixels through artificial deletion. Smoothing algorithms are used to
reduce this undesirable graininess. However, this also means that edges are
smoothed and appear less sharp [25 ]
[26 ]. The SR allows for a more realistic
representation with better discrimination of structures. However, details of
1–2 mm in size might be lost.
Chromatic colors
The human eye has a significantly higher resolution in color vision compared
to black and white. Therefore, it makes sense to display sonographic images
in color gradations (monochromatic) or gray scales in different colors
(polychromatic). This is highly dependent on the examiner's
adaptation to a color scheme. Unbiased students prefer the monochromatic
display, opposed to experienced ultrasound users, who are used to black and
white images and thus favor this setting [27 ].
However, the advantage of B-mode colorization over gray mode imaging for the
detection of focal liver lesions could not be proven ([Fig. 10 ]) [28 ].
Fig. 10 Different gradations (polychromatic, monochromatic)
are shown in grayscales a and in different colors b
and c .
Other factors
Transmission power
Transmission power describes the energy per unit of time
(mW/cm2 ) and influences image quality ([Fig. 11 ]). Depending on transmission power, US
applications exert both mechanical and thermal effects on the tissue. Although
no adverse effects of diagnostic US have been noticed in several studies, US
examination should still follow the ALARA principle (“as low as
reasonably achievable”). This is particularly important in fetal US
(developing tissue and bone) and in ophthalmology, which is why special
examination presets exist for such sensitive tissues [29 ]
[30 ]
[31 ].
Fig. 11 Examination of the right liver lobe using different
settings for transmission power: Energy at 100% (10a ) and
at 10% (10b ). Note the reduction of brightness and loss
of detail.
Presets
Particular combination settings of the above-mentioned parameters of B-mode
imaging can be used in so-called presets, which are either specified by the
device manufacturer or can be defined by the user. It is strongly recommended
that beginners first develop a feeling and understanding for the corresponding
effects of the settings, so that presets can be used in a targeted and
situation-specific way.
Automatic image optimization
Most of the newer ultrasonic devices offer the function of automatic image
optimization. This can work well in many cases, but also poorly as can be seen
in [Fig. 12 ]. It is usually of benefit to
manually adjust the image optimization settings as described in this article and
summarized in six steps in [Table 1 ]. Otherwise,
an optimal image setting is not ensured. If the function is nevertheless used,
it should be noted that the automatic image optimization function works best if
the transducer is held still and the patient does not move.
Fig. 12 Inadvertent effects of automatic image optimization:
Manually adjusted image of the filled urinary bladder before a
and after b automatic image optimization.
Table 1 Six steps to achieve optimal settings for B-Mode
US.
Steps
B-Mode parameter
Remarks
1st
Transmission power
Depth penetration is improved and scattering is reduced with
increasing transmission power; in accordance with the ALARA
principle.
2nd
Gain
Signal amplitude is increased and noise is reduced with
increasing gain. Adjust as low as possible to avoid
overexposure. Use time gain control (TGC)/depth gain
control (DGC) if necessary for compensation of strongly
enhanced or diminished tissue attenuation.
3rd
Frequency
Spatial resolution is improved at the cost of depth
penetration by increasing center frequency (and
inversely).
4th
Depth penetration
Adjust to the structure of interest, no higher than
required.
5th
Focal zone(s)
At the level of interest or use focus.
6th
Further settings
Only in the case of insufficient image quality: change the
preset, adjust the dynamic range, gray maps, persistence,
and/or frame rate.
Trackball or Touchpad
The trackball or touchpad is the mouse of the US device and is the common
operating instrument of the screen cursor. The ball can be rotated freely in all
axis directions and is used for uncomplicated movements of the cursor on the X
and the Y axis on the monitor. Other functions are also controlled with it, such
as scrolling through a video, positioning the body marker, or adjusting a scale.
The same concept is utilized with a touchpad instead of a trackball.
Freeze
This function is used to pause the moving live image to be able to judge
individual frames more precisely, or to save and store them. Today's
devices also offer the possibility of rewinding a certain period of time. This
is particularly advantageous for locating structures that are only briefly
visible in the moving image and often elude targeted freezing attempts.
Loop function
Current devices offer the possibility of rewinding a certain period of video time
by continuously storing the captured images, similar to the freeze function
above. The length of the loop depends on the system used, while the frame rate
is also subject to the converter and image depth.
Panoramic imaging
Due to the limited extension of the acoustic window, depicting large structures
and their topographical relations is difficult with traditional US imaging. The
examiner usually makes a subjective assessment of the extension of large organs
or pathologies. Overview images are not possible with classical US examinations.
To overcome this disadvantage of US, panoramic images up to 60 cm long can be
produced by merging several images during an even and continuous transducer
movement along the structure of particular interest ([Fig. 13 ]). In addition to displaying large organs such as the liver,
it can also be used to clearly display the topographical relation and dimensions
of tumors, as well as vascular and intestinal tract anatomy. Therefore,
panoramic imaging and storage of image loops are very helpful tools to
communicate US findings [32 ]
[33 ].
Fig. 13 The normal appendix depicted using panoramic imaging.
3D Ultrasound
A clear representation of anatomy and topography can also be accomplished using
three-dimensional (3D) US. While the procedure has already been established for
prenatal US, precise volumetry, determination of spatial requirements, and
topography studies can also improve diagnostic accuracy in abdominal sonography
or echocardiography. Meanwhile, reconstruction in real time is also available in
the latest devices (4D sonography) [34 ]
[35 ].
Documentation
Clips
The clips function makes it possible to record short films, and thus display
moving structures. Usually motion image data are captured prospectively,
while some machines provide the possibility to store films retrospectively.
This is feasible because the devices continuously store the live image in a
memory and overwrite the oldest images with the newest ones after a certain
period of time (“first in, first out”). The length and the
supported file formats (e. g. AVI, JPEG and DICOM) depend on the
system used, while the frame rate also hinges on the converter and the image
depth. It is also possible to save individual images from the clips.
Measurements
The measurement function is an essential part of the US examination, as many
diagnostic criteria are based on quantitative findings.
This function is available during an examination or with stored images. The
desired measuring points are searched with the trackball or touchpad and set
by the "enter" or "set" button. The
measurement function includes not only the distance between two points, but
also areas, volumes, angles, circumference as well as methods with more
complex calculations (gray scale and strain histograms, strain ratio, shear
wave velocity, quantification of US beam attenuation and tissue
heterogeneity) depending on the examination mode.
Pictogram, body marker
The pictogram is a simple way of making the location of the sound window
comprehensible to viewers of the recorded images. Depending on the device,
the representation of the pictogram is more or less elaborate and is usually
positioned using the trackball/touchpad. In Germany, the use of a
pictogram is mandated by health care providers, but a relatively large
number of examiners renounce this function [36 ].
Store
The “store” button allows for permanent storage of single
frames of the live image. Different storage media are available ranging from
the local hard disk and USB sticks to network storage, where DICOM is the
standard format. DICOM stands for "Digital Imaging and Communication
in Medicine" and enables communication and data exchange between
different systems, such as the ultrasound machine and a viewing workstation
or the patient management system. Once transmitted, the content is available
on servers or local storage [37 ]. The DICOM
format not only contains the image data but also additional image-related
information like patient data, equipment, examination details, and basic
image metadata. Nowadays, video clips or cine loops can also be stored,
which unlocks additional potential in diagnostics but involves large amounts
of data. These large datasets, particularly videoclips which can involve
several thousands of images may take up a significant amount of space on
Picture Archive and Communications Systems (PACS), which comes at a cost.
However, scanners can be configured to only transfer relevant
images/video clips selected by the operator.
Print out
This method of preserving images is often used as a quick way of passing them
on to patients, but in the course of digitalization it is no longer
appropriate for the documentation of examination findings.
Further Literature and Illustrations
Further Literature and Illustrations
We explicitly refer to the further literature on B-mode ultrasound, imaging examples
[38 ]
[39 ], and the guidelines of the European Federation of
Societies for Ultrasound in Medicine and Biology (www.EFSUMB.org).
