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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5782_Библиотеки_им_академика_М_И_Перельмана.pdf
CHAPTER 2 Scanning Planes and Scanning Methods 19
TRANSVERSE SCAN
Left lateral
Right lateral
Po
Posterior
(Skin surface)
Left Right
Image
Anterior
(Skin surface)
Anterior
Image
Medial
-POSTERIOR- APPROACH
Image
TRANSVERSE SCAN
-LEFT LATERAL- APPROACH
Posterior
(Skin surface)
sterior
Anterior
Image
Medial
TRANSVERSE SCAN
-RIGHT LATERAL- APPROACH
20 PART I General Principles
Lateral
Medial
Superior
Inferior
CORONAL SCAN
Coronal Scanning Plane
Scanning in coronal planes means that the ultrasound beam is
entering the body from either a right or left lateral direction and that
the anatomic portion of body structures being visualized from that
particular direction are:
• Lateral (right or left)
• Medial
• Superior
• Inferior
NOTE: Anterior and posterior are not seen on a coronal scan; therefore,
the transducer must be moved either anteriorly or posteriorly from a
coronal plane to visualize adjacent anatomy.
Image
-LEFT LATERAL- APPROACH
Lateral
(Skin surface)
Superior Inferior
Image
Medial
Image
CHAPTER 2 Scanning Planes and Scanning Methods 21
CORONAL SCAN
-RIGHT LATERAL- APPROACH
Lateral
(Skin surface)
Superior Inferior
Image
Medial
Image
Scanning Methods
NOTE: The primary role of a sonographer is to provide interpretable
images for diagnosis by a physician. This goal is totally dependent on the
skill of the operator. Becoming an accomplished sonographer happens
with practice and the development of good scanning methods.
Transducers
• Much has been accomplished with regard to the various types and
designs of transducers used in diagnostic ultrasound. The new
types and styles offer better penetration, better resolution, and better frame rates. Also, ergonomically designed transducers assist the
sonographer in producing optimal images and providing enhanced
patient care.
• Transducers come in a variety of shapes and sizes. The shape of the
transducer determines the field of view, and the frequency (MHz)
of the sound waves emitted determines how deep the sound waves
penetrate and affects the clarity of the image.
• The depth of the structure being imaged ultimately determines
which transducer should be used. Low frequency transducers have
the most penetration whereas high frequency transducers have less
penetration and are used for more superficial structures.
22 PART I General Principles
• Conventional diagnostic ultrasound transducers include:
• Curved array: 10-4, 8-5, 5-2, 5-1 MHz. Typically used for
abdominal, obstetric and gynecological imaging.
• Sector array: 12-4, 5-1, 4-1 MHz. Generally used for intercostal
scanning.
• Linear array: 18-5, 12-5, 9-3, 8-4 MHz. Typically used for small
or superficial structures and extremity Doppler.
• Endocavital: 10-3, 9-5, 8-5 MHz. Used for endovaginal and
endorectal imaging.
• TEE: 7-3 MHz. Used for transesophageal echocardiography.
• Hockey stick: 12.5 MHz. Intraoperative imaging.
• 3D: 7-3 MHz. Three dimensional imaging.
• All transducers have a focal zone; an area where the sound beam
is narrow and imaging is at its best. A transducer’s focal zone
is usually indicated by a small triangle just to the right of the
image. When scanning, every effort should be made to position the area(s) of interest in that focused area to obtain the best
images.
How to Use the Transducer
• Scanning should be a series of fluid motions. Practice rocking and
sliding the transducer to scan through body structures.
• Transducers can be easily manipulated into different posi-
tions which provide you with multiple options for thoroughly
evaluating an area(s) of interest and obtaining the best images
(Figure 2-2).
• The angle of incidence, or the angle at which the sound beam
strikes the surface of a structure, affects the image. When the transducer/sound beam angle is perpendicular, more sound waves are
reflected back, fewer are lost or scattered, and the result is a better,
more accurate image.
• Applying the correct amount of pressure with the transducer
can improve image quality. Typically, pressure should be applied
evenly and lightly but in some cases, more pressure is applied
to reach the focal zone or compress a vein. Experiment with
using more or less scanning gel as it affects the pressure as well.
Note that the pressure should never cause discomfort to the
patient.
• Positional orientation of the transducer verifies the scanning
plane. In most cases, the manufacturer of the transducer sets the
positional orientation. Sagittal scanning plane orientation, for
example, is usually indicated by a notch or raised portion on the
top surface of the transducer. Once the transducer orientation is
established, the scanning plane can be changed by rotating the
transducer 90 degrees.
CHAPTER 2 Scanning Planes and Scanning Methods 23
Perpendicular
.
AB
The transducer is straight up and down.
Rotating
The transducer is rolled with fingertips to
twist, first one way, or the other, to oblique
scanning planes for viewing the greatest
margins of structures.
Sternum
CDE
Angled
The transducer is angled superiorly,
inferiorly, or right and left laterally at
varying degrees.
Sliding
Using a fluid motion, slowly slide the
transducer along the length of a structure
then rotate the transducer 90º and slowly
slide through the structures width.
F
Subcostal
The transducer is angled
superiorly just beneath the
inferior costal margin.
Sternum
Intercostal
The transducer is between the ribs
It can be perpendicular, subcostal,
or angled.
Sternum
Figure 2-2 Transducer Positions and Motions. Transducers can be easily manipulated into different positions and motions
for optimal imaging. They include the following: A, Perpendicular, B, Rotating, C, Angled, D, Subcostal, E, Intercostal, F, Sliding.
How to Take Accurate Images and Measurements
• Scan according to how a structure is oriented or how it lies within
the body. The orientation, or lie, is determined by the length or
long axis (maximum length) of a structure. The long axis of a
structure can be seen in any scanning plane depending on how
that structure lies in the body. For example:
• The pancreas lies from right to left, across the body, at a slight
angle; therefore its long axis is seen in a transverse oblique scanning plane (Figure 2-3). Oblique the scanning plane by holding
the transducer perpendicular and very slowly, slightly rotate it one
way then the other until the required degree of oblique is achieved.
24 PART I General Principles
Inferior
RightL
Superior
Inferior
tL
t
Sa
Superior
Transverse
oblique plane
ROTATE
Gallbladder
Right
kidney
Pancreas
Transverse plane
eft
IVC
Midsagittal plane
Figure 2-3 Pancreas long axis would be seen in a transverse oblique scanning plane. The sonogra-
pher can resolve the long axis by slightly rotating the transducer and scanning through the pancreas
until the long axis is resolved, as demonstrated in this figure.
Sagittal plane
ROTATE
IVC
Pancreas
ef
Righ
Gallbladder
Right
kidney
gittal
oblique
plane
Figure 2-4 Right kidney long axis would be seen in a sagittal oblique scanning plane. Notice how the
Midsagittal plane
long axis is resolved by slightly rotating the transducer.
• In a true sagittal plane a kidney cannot be viewed in its entirety
because the kidneys are positioned at an angle in the body. Therefore, the sagittal plane must be at an oblique to match that angle
(Figure 2-4). Oblique the scanning plane by holding the transducer perpendicular and very slowly, slightly rotate it one way
then the other until the required degree of oblique is achieved.
Sagittal plane
Sagittal
e
plane
oblique plane
A
B
Right
kidney
Right
kidney
Gallbladder
Gallbladder
IVC
Pancreas
IVC
Pancreas
oblique plan
Transverse
ROTATE
Transverse
plane
Diaphragm
Liver
ROTATE
Gallbladder
Right
kidney
IVC
C
Coronal
plane
Coronal oblique
Figure 2-5 The orientation (longitudinal lie/long axis) of the gallbladder (GB) is variable because
it is suspended by a long mesentery and can lie in different locations throughout the abdomen. As
illustrated in the figures, once the orientation is determined, the sonographer can slightly rotate the
transducer, scanning through and evaluating the GB, until the long axis is established. A, GB long axis
will be seen in a sagittal oblique plane. B, GB long axis will be visualized in a transverse oblique plane.
C, GB long axis will be seen in a coronal longitudinal plane.
26 PART I General Principles
L × W × AP = Volume
ribs
ribs
Midline of body
La
• The long axis of the gallbladder can be seen in any of the three
scanning planes because of its variable position in the body (Fig-
ure 2-5). Once the orientation of the gallbladder has been deter-
mined oblique the scanning plane by holding the transducer
perpendicular and very slowly, slightly rotate it one way then
the other until the required degree of oblique is achieved.
• From the long axis scanning plane, slowly rotate the transducer 90
degrees into the short axis plane for anteroposterior views and width
measurements, which are taken at a structure’s widest margins.
• To accurately measure structures, begin by scanning as perpen-
dicular to the structure as possible for the truest representation of
its size. As previously discussed, if the sound beam is not perpendicular to the structure, the size of the structure is distorted on the
image. The degree of distortion depends on the degree of the angle
of the sound beam (or the angle of incidence).
• Typical measurements are calculated in volumes based on:
L represents length, W is width, and AP is the anteroposterior
dimension.
Surface Landmarks
• The following surface landmarks are used as references when
scanning:
Sternal notch
Sternum
Xiphoid process
of sternum
Medial angle of ribs
teral angle of ribs
Iliac crest
Inferior
costal
margin
Medial angle of
Lateral angle of
Umbilicus
Iliac crest
Symphysis pubis
CHAPTER 2 Scanning Planes and Scanning Methods 27
Review Questions
Answers on page 628.
1. Coronal planes divide the body into unequal _________ and
_________ sections.
2. When scanning in a coronal plane, the ultrasound beam enters the
body from
a) either an anterior or posterior direction.
b) a posterior direction.
c) a medial direction.
d) either a right or left lateral direction.
3. Transverse planes divide the body into unequal _______and _______
sections.
4. When scanning in a transverse plane, the ultrasound beam enters
the body from
a) either an anterior, posterior, right lateral, or left lateral direction.
b) either an anterior or posterior direction.
c) a right or left lateral direction.
d) either an anterior, posterior, or medial direction.
5. Sagittal planes divide the body into unequal _________ and ________
sections.
6. When scanning in a sagittal plane, the ultrasound beam enters the
body from
a) either an anterior or posterior direction.
b) either an anterior, posterior, right lateral, or left lateral direction.
c) either an anterior, posterior, or medial direction.
d) either a right or left lateral direction.
7. Scanning planes are _____ dimensional.
8. The anatomic area(s) not seen in a coronal plane
a) are lateral and medial.
b) is superior.
c) are anterior and posterior.
d) is inferior.
9. The anatomic area(s) not seen in a transverse plane
a) are lateral and medial.
b) is medial.
c) are superior and inferior.
d) are anterior and posterior.
10. The anatomic area(s) not seen in a sagittal plane
a) is posterior.
b) is lateral.
c) are superior and inferior.
d) are anterior and posterior.
11. Scanning planes are often obliqued (by very slightly twisting the
transducer). The degree of the oblique is determined by ___________
________________________________________.
28 PART I General Principles
12. The oblique scanning plane affords visualization of the
_____________________________.
13. The ___________ of the structure being imaged ultimately determines which transducer should be used.
14. When scanning, every effort should be made to position the area(s)
of interest in the transducer’s ________________________ to obtain
the best images.