Ultrasound (US) Flashcards
High frequency sound waves beyond the range of human hearing is called
ultrasound
(20 Hz to 20 kHz = normal range)
What is the normal frequency of soundwaves
for diagnostic ultrasounds?
1 - 30 MHz
What is the propagation velocity of sound?
1540 m/s
Ultrasound depends on __________
calculated as the velocity times the tissue density
Acoustic Impedance (Z)
Frequency x Wavelength = ________
Velocity
If you want to achieve better resolution on an ultrasound,
you must:
_____ frequency and _____ wavelength
increase frequency
and
decrease wavelength
If you want to achieve better penetration on an ultrasound
you must:
______ frequency and _______ wavelength
decrease frequency
and
increase wavelength
Attenuation occurs with _______ frequencies
which causes less information to return
higher
Penetration ______ as
frequency and resolution increase
decreases
Increasing the distance from the transducer can
cause ________, or loss of the ultrasound
attenuation
A reflected soundwave is generated at the interface of
an _________ __________
impedance__mismatch
Constant impedance occurs when an ultrasound
is traveling through a __________ medium
homogenous
Impedance (Z) is a characteristic of the
_________ medium
propagation
Round trip transit time is directly related to the _________,
or the distance of the sound wave reflection site
depth
Total roundtrip time divided by 2
is representative of the _______
interface
What are the 4 assumptions made by Ultrasound?
Assumptions of US:
The <u>speed</u> of sound in all tissues is 1540 m/s
The US beam only travels in a <u>straight line</u> with a <u>constant rate of attenuation</u>
The US beam is <u>infinitely thin</u> with <u>all echoes</u> originating from its <u>central axis</u>
The depth of the reflector is <u>accurately determined</u> by the time for sound to travel from the transducer to the reflector and back again
What are the 6 artifacts that you may encounter with
Ultrasound?
Acoustic Shadowing
Acoustic Enhancement
Edge Shadowing
Reverberation Artifact
Slice Thickness Artifact
Mirror Image Artifact
This artifact occurs distal to highly reflective objects
(high acoustic impedance mismatch)
because the interface absorbs or reflects the entire sound
resulting in an anechoic area
Acoustic Shadowing
Clean Acoustic Shadowing occurs at the interface of
tissue and ______
bone
Dirty Acoustic Shadowing occurs at the interface of
tissue and ______
gas
Which type of acoustic shadowing occurs
when most of the sound waves get absorbed
resulting in a complete absence of reverberation artifacts?
Clean Acoustic Shadowing
(tissue-bone interface)
Which type of acoustic shadowing occurs
when 99% of the sound waves get reflected
and a resultant reverberation artifact is produced?
Dirty Acoustic Shadowing
(tissue-gas interface)
What type of acoustic shadowing is present if
a homogenous anechoic shadow is produced?
CLEAN
What type of acoustic shadowing is produced if
an inhomogenous/reverberation artifact is present?
DIRTY
This type of ultrasound artifact occurs when
fluid of homogenous acoustic impedance attenuates
less sound than the surrounding tissues,
and the US machine overcompensates resulting in a
hyperechoic area distal to the structure
Acoustic Enhancement
This US artifact occurs as a small shadow at the border of
round structures
Edge Shadowing
This US artifact occurs at
curved surfaces like the urinary bladder and the gallbladder
and can mimic sediment
Slice Thickness Artifact
This US artifact occurs at
highly reflective air-fluid interfaces
(like the diaphragm-lung or pericardium-lung interfaces)
and at concave surfaces
Mirror Image Artifact
(false image produced on the other side of the reflector)
Coupling Gel is used for ultrasounds because
______ is the enemy of US
AIR
________ prevents loss of sound due to the
compressibility of air.
Air acts like a shock absorber and dampens the US wave.
Coupling Gel
What are the 4 types of US transducers?
Multi-frequency
Linear
Sector
Convex
_______ crystals both emit and receive ultrasound
and are a component of US transducers
Piezoelectric crystals
The smaller the animal, the _____ the frequency (MHz) required
for ultrasound
higher
T/F:
Patients must fast for 12 hours before an ultrasound
can be performed
TRUE
Stress must be avoided in patients that will be
undergoing ultrasound because stress can cause
_________
aerophagia
(AIR IS THE ENEMY OF ULTRASOUND!)
An ultrasound is performed on an animal in
______ recumbency
dorsal
In order to scan the sagittal plane,
the transducer must be ________ oriented
cranially
In order to scan the transverse plane,
the transducer must be oriented ____________
towards the examiner
What side of the body will you find the spleen?
LEFT
The bladder and prostate are seen when scanning
the _____ side of the patient
left
The liver is seen when scanning the
______ side of the patient
right
The equivalent term for opacity on a radiograph
Echogenicity
Vascularity can be assessed on ultrasound
by utilizing _______
Doppler
Homogenously black structures seen on ultrasound
that are related to very low intensity of returning echoes
Anechoic
This term refers in general to white structures
seen on an ultrasound due to high intensity of returning signals
Hyperechoic
Put the following in order of echogenicity
from least echogenic (black) to most echogenic (white):
bone/air, liver, spleen, prostate, urine, kidney
Blackest to Whitest:
Urine
Kidney
Liver
Spleen
Prostate
Fat
Bone/Air
(UK Loves Super Pretty Foreign Babes)
If a fluid appears anechoic on US,
it is most likely _________
Transudate
If a fluid appears speckled or more echogenic,
it is most likely ________
Exudate, Blood, or Chyle
What two locations in the abdomen will
be the first to accumulate free abdominal fluid?
Apex of Bladder
Between the Liver Lobes
T/F:
Arteries are easily visualized in ultrasounds, but veins
are nearly invisible
FALSE!
VEINS are Visible, arteries are not!
How would you distinguish the
portal veins from the hepatic veins
on an ultrasound?
Portal veins have hyperechoic walls (white)
and
Hepatic veins have isoechoic walls (blends in with surroundings)
The liver is ____echoic to the spleen
and coarser in appearance
hypoechoic
(liver is darker than spleen)
When examining the liver in ultrasound,
diffusely hypoechoic parenchyma with
a prominent portal vein wall
are indicative of what conditions?
Acute hepatitis
Venous congestion (would also see enlarged hepatic veins)
Lymphosarcoma
When examining the liver on ultrasound,
a diffusely hyperechoic parenchyma (whiter) with
reduced visualization of portal vein wall
is indicative of what conditions
Diabetes mellitus
Hyperadrenocorticism
Hepatic Lipidosis
Lymphosarcoma
A normal gallbladder is _____echoic to liver parenchyma
isoechoic
T/F:
When examining the gallbladder of a normal dog or cat,
the intrahepatic biliary ducts (hepatic and cystic) are
readily visualized
FALSE!
intrahepatic biliary ducts are NOT detected
in a normal dog or cat
The ___________ of the gallbladder can be
traced in normal cats, but not in dogs due to overlying
gas in the GI tract
Common Bile Duct
T/F:
Sludge, or anechoic content, can be seen in a normal
animal’s gallbladder
TRUE
A thickened gallbladder wall is indicative of
Cholecystitis
If hyperechoic clean shadows are seen in the gallbladder,
the most likely cause is
Choleliths (mineral deposits)
Dilation of the gallbladder and common bile duct
are indicative of
obstruction
The normal echogenicity of the splenic capsule is
hyperechoic (white)
The spleen has _______ echogenicity than the kidney
greater (whiter)
Fat and the splenic vein can be seen at the _____ of the spleen
hilus
The renal pelvis of the kidney is _____echoic due to fat
hyperechoic (white)
The renal cortex is ______ echogenic than the spleen
less
Renal cortex is darker than the spleen
The renal cortex of the kidney is _____ echogenic
than the renal medulla
more
Renal cortex is whiter than the renal medulla
The renal pelvis is normally ______ mm wide
1 - 2 mm
The proximal ureter is enlarged if it is greater
than _______ mm
3 - 4 mm
The normal renal size in cats is ______ +/- 0.46 cm
but in dogs, the size is variable
3.66
When would you want to ultrasound the urinary system?
To examine bladder neoplasia and calculi
The bladder appears _____echoic on US
anechoic (black)
The _______ is in close apposition with the liver caudally
and lies cranial to the last pair of ribs
stomach
In a dog, the stomach is normally ____mm in thickness
3 - 5 mm
In a cat, the stomach is normally _____mm in thickness
2 mm
What are the layers and corresponding echogenicities of
the layers of the stomach?
Serosa- hyper
Muscularis- hypo
Submucosa- hyper
Mucosa- hypo
Lumen-Mucosa Interface- hyper
______ peristaltic contractions per minute
are normal
4 - 5
In a ______ the jejunum and the ileum are of similar thickness
but
In a _______ the duodenum and the ileum are similar
dog - jejunum and ileum
cat - duodenum and ileum
The thickest layer of the intestines is the
________ and it is hypoechoic
mucosa
Which pattern is seen in the small bowel
if it is in a collapsed state, is hyperechoic, and no acoustic
shadowing is present?
Mucous pattern
Which pattern is seen in the small bowel
if the luminal content is anechoic?
Fluid pattern
Which pattern is seen in the small bowel
if it is hyperechoic and acoustic shadowing is present?
Gas pattern
The cecum in a ____ is difficult to identify due to intraluminal gas
dog
