Quiz 1 Flashcards
What is it called when a structure appears in an unexpected location?
Superimposition
When imaging the abdomen, do you want to take it on inspiration or expiration?
Expiration
When viewing a transverse plane, which way is the transducer pointed?
Towards the examiner
When using the doppler, which color means blood is flowing away from the transducer?
Blue
Intensity of radiation decreases with the square of the distance from the source. This is known as what?
Inverse square law
Double the distance = 1/4 the intensity
Decreasing the distance = (original/new)^2
Describe the Photoelectric effect
Atomic number dependent
Desirable
Decreases as kVp increases
What is it called when an organ is less echoic than other structures? Give an example
Hypoechoic
Liver and Kidney are hypoechoic to the spleen
What structures are visible in the cranial dorsal part of the abdomen?
Right kidney
Spleen
Stomach
Liver
What general kVp and mAs settings do you want to use when radiographing the thorax?
High kVp, low mAs
Air provides contrast
More Compton effect
T/F: Resolution is better with higher frequency/smaller wavelength
True
Order these organs based on increasing echogenicity:
Liver, Prostate, Spleen, Kidney (Cortex/Medulla)
Medulla
Cortex
Liver
Spleen
Prostate
Describe the Compton effect
Atomic number independent (less tissue distinction)
Increases as kVp increases = less contrast
What is it called when a structure has the same echogenicity as another structure? Give an example
Isoechoic
Liver and Kidney
What could cause a radiograph to be underexposed?
kVp or mAs too low
When viewing the sagittal plane, which way is the transducer facing?
Cranially
What is edge shadowing?
Small shadow at the edge of round structures
Which transducer is best when performing a cardiac US?
Sector transducer
T/F: Radiolucent means an object appears darker?
True
What are the borders you should use when radiographing the abdomen?
Cranial - diaphragm
Caudal - greater trochanter of the femur
When doing VD, use frog leg positioning
What organs do you view on the left side?
Spleen
Left kidney
Bladder
Prostate/uterus
What organs do you view on the right side?
Right kidney
Liver
What are your DDx for a diffusely hyperechoic liver parenchyma?
Diabetus mellitus
Hyperadrenocorticism
Hepatic lipidosis
Lymphosarcoma
Which transducer is best to use when performing an abdominal US?
Convex transducer
What is the contrast medium in the abdomen?
Fat
What is it called when a structure has a higher echogenicity than other structures? Give an example
Hyperechoic
Spleen is hyperechoic to the Liver and Kidney
What structures are visible in the caudal ventral part of the abdomen?
Prostate
Bladder
What is the difference between power and gain?
Power is how strong the signal is when you send it out
Gain is how strong the signal is coming back
What change in the gal bladder will you see with cholecystitis?
Thickened gal baldder wall
What causes acoustic shadowing?
High acoustic impedance mismatch
Bones have a very high impedance
Air has a very low impedance
What are the dose limits for the general public/vets/pregnant women?
1/50/5 mSv/yr
What causes the renal pelvis to appear hyperechoic?
Fat
What is the formula for the interface?
Acoustic impedance (Z) = velocity (v) x tissue density (p)
Echo signs are the same as Rontgen signs plus…
Homogeneity
Texture
Compressibility
Surrounding tissue
Vascularity
Through-transmission
Other artefacts
Which vein in the liver has a hyperechoic wall?
Portal vein
T/F: the pylorus is more medial in the dog compared to the cat?
False!
It is more medial in the cat. If you see the pylorus medial in the dog, there could be hepatomagaly
What is acoustic enhancement?
When the machine overcompensates for fluid of homogeneous acoustic impedance that attenuates less sound than the surrounding tissue
The result is a hyperechoic area distal to the structure in comparison to the surrounding tissue
List the layers of the GIT and if they are hyper or hypoechoic
Serosa - hyper
Muscularis - hypo
Submucosa - hyper
Mucosa - hypo
Lumen-mucosa interface - hyper
What are the characteristics of a low contrast image?
Lots of grays
Good for lungs
X-rays penetrate more
More compton effect
More uniform absorption
Unequal magnification causes what?
Distortion
Ex: twisted pelvis
List the 5 opacities from dark to light
Air
Fat
Water
Bone
Metal
What contrast medium is used with MRI and what is it useful for?
Gadolinium
Only used for T1
Detects bad BBB and inflammation
What general kVp and mAs settings do you want to use when radiographing the abdomen?
Low kVp, high mAs
Fat provides contrast
More Photoelectric
Changing the mAs has what effect?
How much do you usually change it by?
Changes the number of X-rays
Double/Half
What are the assumptions that the US machine makes when generating an image?
The speed of sound in all body tissues is 1540 m/s
The US beam only travels in a straight line with a constant rate of attenuation
The US beam is infinitely thin with all echoes originating from its central axis
The depth of a reflector is accurately determined by the time taken for sound to travel from the transducer to the reflector and return
What is it called when an organ is homogeneously black (no signal)?
Give an example
Anechoic
Bladder
Border of two structures of same opacity in contact and border is not visible?
Sillhouette
T/F: Lesions in the down lung will be more dorsal in lateral view?
True
Where does dirty acoustic shadowing occur?
Tissue-gas interface
What is the slice thickness artifact commonly confused with?
Sediment
T/F: Optical density = Lighter?
False
Darker
Why do we use 2D/3D reformatting?
To make sagittal or dorsal views from transverse cuts
What does an intensifying screen do?
Converts xray photon to light photons which expose the film
Permits over 100x reduction in mAs
What structures are visible in the caudal dorsal part of the abdomen?
Rectum
Descending colon
What are your DDx for a diffusely hypoechoic liver parenchyma?
Avute hepatitis
Venous congestion
Lymphosarcoma
What contrast medium is used with CT imaging and what is it used to diagnose?
Iodinated IV
Nasal disease, thoracic masses, fragmented medial coronoid process, radiation therapy planning, portal vein anomalies
What are the Rontgen/Echo signs?
Size
Shape
Number
Location
Margination
Echogenicity
Where is it easiest to identify the ileum?
Right cranial abdomen, medial and ventral to the right kidney
What are the Roentgen signs?
Size
Shape
Number
Location
Margination
Opacity
What will an obstruction do to the gal baldder?
Dilation of the gal baldder and common bile duct
What are the different sequences of an MRI?
T1
T2
FLAIR
STIR
T/F: A reflected sound wave is generated at the interface of an impedance mismatch
True
Extent to which a film, image plate, or flat panel can be over and underexposed and still be acceptable
Exposure latitude
Conventional film - very steep, little wiggle room
Digital - less steep, much more wiggle room
T/F: Contrast is best with CT?
False
Best with MRI, then CT, then rads
Wha changes to the kVp and mAs can be made to increase the contrast of an image?
Double the mAs, increase kVp by 15%
What could cause a radiograph to be overexposed?
kVp ot mAs too high
Which rib do you use to assess the size of the pulmonary artery?
9th
When should a grid be used?
When the patient is thicker than 10cm
Need 2-3x more photons when grid is used so increase the mAs
Which side of the animal should you be on when performing an ultrasound?
Right
What are the characteristics of a high contrast image?
Black and white, few grays
Good for abdomen
X-rays penetrate less
More photoelectric effect
If free abdominal fluid is anechoic, is it a transudate, exudate, blood, or chyle?
Transudate
Which MRI sequence cannot detect fat?
STIR
Superimposition where overlapping creates summation opacity
Summation
Which lobe should you look at to assess the pulmonary artery and vein?
Cranial lobe
View in LL as opposed to RL (superimposed)
Which MRI sequence detects fat only?
T1
When looking at a normal animal, how should the echogenicity of the spleen compare to the left kidney?
Spleen should be hyperechoic to the left kidney
A corrugated intestine is secondary to what conditions?
Peritonitis
Pancreatitis
T/F: Radiographic density = Darker?
False
Lighter
What are the uses of contrast medium?
Enhanves blood vessels
Vascular leaks
GI
What structures are visible in the dorsal middle part of the abdomen?
Left kidney
Descending colon
SI
Cecum
What will cause attenuation?
Increased distance from the transducer
Increased acoustic impedance mismatch
Higher frequency transducers
What is the range of light intensities a medium can capture?
Contrast optimization
T/F: The renal cortex is hypoechoic to the renal medulla
False
Hyperechoic
When the stomach is empty, what organ does it resemble and why?
The kidney because of the rugal folds
Which imaging system(s) use Tomography and what is it?
CT and MRI
Images are slices from the patient
What structures are visible in the ventral middle part of the abdomen?
Spleen
SI
Omentum
What changes to the kVp and mAs can be made in order to decrease the contrast of an image?
Halve the mAs, decrease kVp by 15%
T/F: Penetration is better with higher frequency/smaller wavelength
False
Lower frequency/long wavelength
What is the difference between helical and multislice methods?
Helical: continuous and faster
Multislice: super fast, entire thorax in
Which imaging system has the best ability to differentiate between two adjacent objects?
Rads, then CT, then MRI
When are compression rads useful?
When viewing the bladder
T/F: You can see the common bile duct in a normal dog
False
But can be traced in a normal cat
For larger animals, do you want to use a high frequency or a low frequency?
Low frequency
What structures are visible in the cranial ventral part of the abdomen?
Liver
Stomach
Which MRI sequence detects everything?
T2
No bone or air
When looking caudally at a transverse section, what will you see dorsally, on the left, and ventrally?
Dorsal - fundus of the stomach
Left - body of the stomach
Ventral - pylorus of the stomach
What is the distance between one peak or trough and the next peak or trough?
Wavelength
What is it called when a false image is produced on the other side of the reflector due to its mirror like effect?
Mirror image artifact
T/F: The detail of an image is best with MRI?
False!
Best with rads, then CT, then MRI
What are some issues with radiographing the thorax in lateral recumbancy?
Lungs always look worse in lateral view
Sedation leads to atelectasis
T/F: The farther an object is from the cassette = larger the image appears?
What is this called?
True
Magnification
Where does clean acoustic shadowing occur?
Tissue-bone interface
Common with foreign bodies in the intestines
Changing the kVp has what effect?
How much do you usually change it by?
Changes the energy of the X-rays
16-20%
T/F: Radiopacity means an object appears lighter?
True
Describe the appearance of the spleen
Variable size
Hyperechoic capsule
Smooth margins
Splenic vein at hilus
Homogeneous fine granular appearance
Which MRI sequence cannot detect free water?
FLAIR
Does attenuation occur with higher or lower frequency?
Higher
What is it called when the returning signal is what we expected for a certain organ?
Normoechoic
