Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5836_Библиотеки_им_академика_М_И_Перельмана.pdf
x
them. Finally, special thanks are due to the editorial staff of Springer: they are a
marvelous team, providing invaluable support and maintaining immense patience
with the editor.
Bergamo, Italy Mauro Zago
Preface
xi
Contents
1 Basic Ultrasound Physics, Instrumentation,
and Knobology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Fikri M. Abu-Zidan
2 Introduction and Focused Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Mauro Zago
3 Abdominal Views: Technique, Anatomy,
Abnormal Images, Scanning Tips, and Tricks . . . . . . . . . . . . . . . . . . . 19
Fernando Ferreira, Eva T. Barbosa, and António R. Silva
4 Thoracic Views: Anatomy, Techniques,
Scanning Tips and Tricks, Abnormal Images . . . . . . . . . . . . . . . . . . . . 39
Andrea A. Casamassima and Mauro Zago
5 Including EFAST in Trauma Algorithms: When?
What Now? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Diego Mariani and Mauro Zago
6 The Role of EFAST in a Comprehensive US Trauma
Management (ABCDE-US): Facing with Clinical Scenarios. . . . . . . . 65
Mauro Zago and Diego Mariani
7 Prehospital Ultrasound in Trauma: Role and Tips. . . . . . . . . . . . . . . . 85
Miriam Ruesseler
8 CEUS: What Is It?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Massimo Valentino, Libero Barozzi, and Cristina Rossi
1
M. Zago (ed.), Essential US for Trauma: E-FAST, Ultrasound for Acute Care Surgeons,
DOI 10.1007/978-88-470-5274-1_1, © Springer-Verlag Italia 2014
1.1 Introduction
Using ultrasound in life-threatening conditions is one of the successful stories of
carrying portable technology to sick patients so as to improve outcome of their
management. The value of ultrasound will be optimized only after understanding its
limitations and pitfalls. This cannot be achieved without understanding basic ultra-
sound physics. This chapter will present basic physics in a simple way that is rele-
vant to clinicians who are keen to start using ultrasound in their clinical practice.
Practical issues will be explained without going into details.
1.2 Basic Ultrasound Physics
Ultrasound is a sound wave having a frequency higher than 20,000 Hz, which is
above the range of human hearing. It is a type of energy that can transmit through
air, fl uid, and solid material. Medical ultrasound machines generate ultrasound
waves and receive the refl ected echoes. B mode (brightness mode), which gives
black and white images, is the basic mode that is usually used in trauma patients.
The sound waves are emitted from piezoelectric crystals from the ultrasound
transducer. As ultrasound waves pass through various body tissues, they are refl ected
back to the transducer creating an image on the monitor. The resistance to propaga-
tion of ultrasound waves (acoustic impedance) will vary depending on the density
of material particles. As the material gets more solid, the particles will become
denser. The denser the material is, the more it refl ects the sonographic waves
(Fig. 1.1 ). Fluid transmits sound waves and has less waves refl ected back. This
F. M. Abu-Zidan , MD, FRCS, FACS, PhD, DipApplStats
Department of Surgery, Faculty of Medicine and Health Sciences ,
UAE University , 17666 , Al-Ain , United Arab Emirates
e-mail:
fabuzidan@uaeu.ac.ae
1
Basic Ultrasound Physics,
Instrumentation, and Knobology
Fikri M. Abu-Zidan
2
yields a black “anechogenic” or “anechoic” image. Other tissues have varying lev-
els of echogenicity. Stones, bones, and calcifi cations yield the brightest “white”
images and a shadow behind them. Between these two extremes, other tissues can
be outlined and identifi ed within the gray scale (Fig. 1.2 ). Fibrous tissue like the
diaphragm or capsule of the kidney will be white without a shadow. Air is a strong
ultrasound beam refl ector. It scatters the ultrasonic waves and prevents transmission
to deeper structures. That is why it is diffi cult to see behind subcutaneous emphy-
sema in a trauma patient.
1.3 Ultrasound Transducers
Transducers contain piezoelectric crystals that emit ultrasound. There are different
factors that can control the way these ultrasound waves are sent:
1 . Continuity : Emission of ultrasound waves can be either interrupted or continu-
ous. Emission of ultrasound waves as pulses will have two periods: a period in
which the pulse is sent and another period in which refl ected waves are received
to generate brightness (B) mode images. Continuous emission of ultrasound
waves is used for the Doppler mode.
2 . Frequency : By modifying the frequency in which waves are sent, it is possible to
have different applications controlling mainly the depth and resolution of the
images. Frequency and resolution have an inverse relationship. The lower
D
L
Fig. 1.1 The denser the material is, the more it refl ects the sonographic waves. Fluid [like bile in
the gallbladder ( GB )] transmits sound waves and has minimum waves refl ected back. This yields
a black “anechogenic” image. Stones ( S ) yield white images with a shadow behind them. Soft tis-
sues, like the liver ( L ), yield different gray color scales. Fibrous tissue like the diaphragm will be
white without a shadow ( D )
F.M . A b u-Zidan
3
frequency is, the poorer the image resolution, but the greater the depth of wave
penetration. Higher frequency probes have less depth penetration but have the
advantage of higher resolution.
The transducer frequencies commonly used for abdominal exam are between
2.5 and 5 MHz. This implies that for obese patients and deep structures, probes
of low frequencies should be used. In contrast, probes of high frequency
(10–12 MHz) should be used for superfi cial structures.
3 . Shape of the surface of the probe : Ultrasound waves are sent vertical to the sur-
face of the probe. By curving the surface, it is possible to widen the area of the
studied fi eld. It is understandable that the lateral resolution in the deeper struc-
tures will be less when using this type of probes. Lateral resolution is the ability
of ultrasound to differentiate between two objects located perpendicular to the
ultrasound beam. These probes are called convex array probes (Fig.
1.3 ). When
the surface is kept fl at, the waves will be parallel with each other, and the lateral
resolution will be much better. These are called linear array probes. These probes
usually have high frequencies of 10–12 MHZ indicating that their penetration is
less than others, but they have excellent resolution. That is why the shape of the
L
GB
IVC
D
Fig. 1.2 Ultrasound of the right upper quadrant in a patient complaining of right upper quadrant
pain to demonstrate acoustic impedance. The gallbladder ( GB ) and IVC contain fl uid which is
black. The liver ( L ) is a soft tissue and is gray in color. The diaphragm ( D ) is a fi brous tissue which
is white without a shadow, and a gallstone which is a solid structure ( arrow head ) is white with a
posterior acoustic shadow ( small arrows )
1 Basic Ultrasound Physics, Instrumentation, and Knobology
4
image of the linear array probe is rectangular compared with the convex array
probe images which will be wider in the area located away from the probe.
4 . Surface area of the probe : It is important to have no barrier between the studied
structures and the ultrasound waves. For example, the ribs will not permit ultra-
sound waves to pass through them when imaging intrathoracic structures through
the thoracic wall and will have a shadow behind them. The phased array probe
has a small surface that will enable the examiner to visualize the heart between
the ribs (Fig.
1.3 ).
5 . Orientation of the probe : Each piezoelectric crystal in the probe is represented
on specifi c points on the screen. Each probe will have a marker to identify a
specifi c side of the probe. The operator should know the probe side before start-
ing any diagnostic or interventional procedure. This side should be confi rmed
practically by putting gel on the surface and moving the index fi nger on it to see
which side it represents. It is advisable as agreed standard to have the marker that
represents the right side of the screen upward toward the head of the patient in
the sagittal or coronal sections (Fig. 1.4 ) and to the right side of the patient in
transverse sections (Fig. 1.5 ). This will save time as emergency physicians will
do both abdominal and thoracic images in emergency conditions and there is no
time to change the setting. The rule of thumb is that “the right side of the patient
should be on the right side of the screen.”
Convex array
Linear array
Phased array
Fig. 1.3 Changing the shape of the surface of the probe and its size has resulted in different types
for different applications
F.M . A b u-Zidan
5
U
D
U
D
Sagital section
Fig. 1.4 Sagittal section of the abdominal examination. The probe marker ( arrow ) should point
upward. The upper part of the abdomen ( U ) should be to the right side of the screen. U upward or
proximal, D down or distal
R
L
R
L
Transverse section
Fig. 1.5 Transverse section of the abdominal examination. The probe marker ( arrow ) should point
to the right. The right part of the body ( R ) should be to the right side of the screen. R right, L left
1 Basic Ultrasound Physics, Instrumentation, and Knobology
6
6 . Slicing the body to get images : It is important to appreciate that the B mode is a two-
dimensional (2D) section that depends on the anatomical site of the slice. The body
can be sliced at different planes depending on the position of the probe. Sections can
be sagittal, coronal, transverse, or oblique. These thin slices are of less than 1 mm
each. This implies that we are visualizing only a thin section of the body. Figure 1.6
demonstrates this principle. If the gallbladder shown in this image is sectioned verti-
cally, then it will appear as a single cavity. If it is transected transversely on the plane
shown in Fig.
1.6 , then it will appear as two cavities and possibly misinterpreted as
an intraperitoneal collection. If the transverse planes are moved to be more proxi-
mal, then it will be appreciated that this is a continuous cavity.
The fan - shaped movement is a very useful technique to obtain images by
using different angles to slice the body while keeping the probe at the same point.
This movement can be horizontal as shown in Fig. 1.7 or vertical.
Fig. 1.6 A schematic diagram demonstrating different sonographic images produced when the
body is sliced by ultrasound at different planes
Tips and Tricks
1. Choose the proper transducer depending on the indication and patient’s
age and built.
2. Use plenty of ultrasound gel to have proper contact between the transducer
and skin.
3. Check the orientation and side of the transducer.
4. Optimize the gain and depth of the image.
5. Use the fan-shaped movement gently.
F.M . A b u-Zidan
7
1.4 Knobology
There are basic buttons that a beginner user of point-of-care ultrasound should know
(Fig. 1.8 ). These include:
1 . On / off button: Ultrasound machines with rapid boot-up are more desirable
because the machine should be moved quickly between patients especially in
mass casualty situations. Long boot-up time may become problematic in this
situation.
2. The gain setting: The gain is the amplifi cation of the received ultrasound signal.
When the overall gain knob is turned to the right side, the received signal is mag-
nifi ed and more received signals are allowed to be processed. The ultrasound
image will become brighter and vice versa (Fig. 1.9 ). Time gain compensation
( TGC ) will change the gain factor so that equally refl ective structures will be
displayed with the same brightness regardless of their depth. Try to overuse/
underuse gain and TGC at different depths to easily understand the meaning of a
right regulation.
3. The image depth : It is always advised to have a deeper depth than needed and
then gradually reduce it to cover the area of interest. One of the pitfalls is to use
a shallow depth missing deeper important sonographic fi ndings.
4. The mode buttons: These buttons will select the mode of ultrasound waves.
Brightness mode ( B mode ) is the basic mode that is usually used. The B mode
gives a two-dimensional (2D) black and white image. Imaging one line over time
is called the moving mode ( M mode ).
Fan shaped movement
Fig. 1.7 Horizontal fan-shaped movement used to obtain sonographic images by changing the
angles in which the body is sliced while keeping the probe at the same point
1 Basic Ultrasound Physics, Instrumentation, and Knobology
8
5. The freeze button: This freezes the image so that certain structures can be mea-
sured, saved, or printed. When turned off, the real-time continuous display of
images is turned on.
6. The caliper and measurement buttons : These buttons will generate point markers
on the frozen image to defi ne distances of interest that can be measured.
TGC
Depth
Gain
Caliper
Measure
Freeze
On/off
Mode
B
M
Fig. 1.8 Basic buttons of a portable ultrasound machine that a beginner user of point-of-care
ultrasound should know
Gain
Fig. 1.9 The ultrasound image will become brighter when the gain is increased
F.M . A b u-Zidan