Ultrasound Physics The document discusses ultrasound physics and imaging. It defines ultrasound as high frequency sound waves beyond human hearing. Ultrasound imaging uses a transducer to transmit sound waves into the body and receive echoes, which a computer interprets into a 2D image. Tissues appear hypoechoic, hyperechoic, anechoic, or isoechoic depending on their echo properties. The document also discusses ultrasound modes, artifacts, spleen anatomy and pathologies visualized by ultrasound.

1. Ultrasound Physics
Presented by-
Dr. Mehrun Naher
MBBS(RMC)
CMU, DMU

2. What is Ultrasound?
 It is the high frequency sound waves whose frequencies are beyond the range of human
hearing.

3. How Ultra sound Works?
 Ultrasound imaging uses a small transducer (probe) to both transmit sound
waves into the body and record the waves that echo back.
 Sound waves travel into the area being examined until they hit a boundary
between tissues, such as between fluid and soft tissue, or soft tissue and bone.
 At these boundaries some of the sound waves are reflected back to the probe,
while others travel further until they reach another boundary and are reflected
back.
 Since the speed, direction, and distance sound waves travel differ depending on
the boundary they run into, a computer can interpret this information as a two-
dimensional image on a screen.

5. Transducer or Probes Types

6. Types of Ultrasound Images
 Hypoechoic: This term means "not many echoes." These areas appear dark gray
because they don't send back a lot of sound waves. Solid masses of dense tissue are
hypoechoic.

7.  Hyperechoic: This term means "lots of echoes." These areas bounce back many
sound waves. They appear as light gray on the ultrasound. Hyperechoic masses are not
as dense as hypoechoic ones are. They may contain air, fat, or fluid.

8.  Anechoic: This term means "without echoes." These areas appear black on
ultrasound because they do not send back any sound waves. Anechoic masses are often
fluid-filled.

9.  Isoechoic: Tissue or structures which produces an echo of the same strength as that
of the surrounding structures or tissues, making it difficult to isolate.

12. Ultrasound Mode
 A-mode: Amplitude Modulation, used in Opthalmology
 B-mode: Brightness Mode, used in Diagnostic sonography.
 M-mode: Motion Mode, used in Fetal heart rate measurement & Echocardiography.

13. What is Artifacts?
 A “False fact” or “Less fact” or “Artificial fact” is an Artifact.
 While taking an image of a patient by one imaging machine, some unwanted shadows
appear on the image which is not of tissue interest and these are called artifacts.

14.  Acoustic enhancement also called posterior
enhancement or enhanced through transmission, refers
to the increased echoes deep to structures that transmit
sound exceptionally well.
 This is characteristic of fluid-filled structures such as
cysts, the urinary bladder and the gallbladder. The fluid
only attenuates the sound less than the surrounding tissue.
The time gain compensation (TGC) overcompensates
through the fluid-filled structure causing deeper tissues to
be brighter. Simply it is seen as increased echogenicity
(whiteness) posterior to the cystic area. The presence of
acoustic enhancement aids in the identification of cystic
masses but some solid masses, especially lymphoma, may
also show acoustic enhancement posteriorly.
Type of Artifacts

15.  Acoustic shadowing: An acoustic
shadow is an ultrasound artifact occurring at
boundaries between significantly different
tissue impedances, resulting in signal loss
and a dark appearance. Shadow detection is
important as shadows can identify anatomical
features or obscure regions of interest.

16.  Comet tail artifact is a grey
scale ultrasound finding seen when
small calcific / crystalline / highly
reflective objects are interrogated and
is believed to be a special form
of reverberation artifact.

17.  Mirror image artifact in
sonography is seen when there is a
highly reflective surface
(e.g. diaphragm) in the path of the
primary beam.
 The primary beam reflects from
such a surface (e.g. diaphragm) but
instead of directly being received by
the transducer, it encounters another
structure (e.g. a nodular lesion) in
its path and is reflected back to the
highly reflective surface (e.g.
diaphragm). It then again reflects
back towards the transducer.

18. Spleen
 The spleen is a wedge-shaped organ lying mainly in the
left upper quadrant (left hypochondrium and partly in
the epigastrium) and is protected by the left 9th to
11th ribs.
 The ultrasound examination of the spleen is better
performed in supine or right lateral position, using an
intercostal approach, with a 3.5 to 5 MHz transducer.
 Visualized best obliquely in the 9th or 10th intercostal
spaces.
 Echogenicity usually higher when compared to the
liver, but may be iso- or hypoechoic.
 Deep breath hold can facilitate visualization of spleen

19. Normal measurement:
 Length< 12 cm
 AP diameter 4 cm to 7 cm

20. Pathologies
 Splenomegaly- An enlarged spleen is also known as splenomegaly
 Length >12cm
 Causes: Portal hypertension, Cirrhosis, Leukemia, Lymphoma, Hepatitis, Malaria,
Typhoid, Kalazar, Tuberculosis.

21.  Splenic cyst: Splenic epithelial cysts, also known
as splenic epidermoid cysts or primary splenic cysts,
are unilocular fluid lesions with thin and smooth walls.
 Usually shows an anechoic to hypoechoic well defined
intrasplenic lesion. Internal echoes may be present due
to debris. Their margin may be echogenic with distal
shadowing due to calcifications.

22.  Splenic abscesses are localized
collections of necrotic inflammatory tissue
caused by bacteria, parasites or fungi. They
uncommonly affect the spleen due to its
efficient reticuloendothelial
system phagocytic activity and,
consequently, are more likely seen in
immunosuppressed patients.
 Splenic abscesses are typically poorly-
demarcated with a variable appearance,
ranging from predominantly hypoechoic
with some internal echoes to hyperechoic.
They may contain septa of varying
thickness.

23.  Splenic mass: Hypoechoic lesions noted in spleen.