Quiz 1 Flashcards by Matt Lazarus

What is it called when a structure appears in an unexpected location?

Superimposition

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When imaging the abdomen, do you want to take it on inspiration or expiration?

Expiration

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When viewing a transverse plane, which way is the transducer pointed?

Towards the examiner

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When using the doppler, which color means blood is flowing away from the transducer?

Blue

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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

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Describe the Photoelectric effect

Atomic number dependent

Desirable

Decreases as kVp increases

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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

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What structures are visible in the cranial dorsal part of the abdomen?

Right kidney

Spleen

Stomach

Liver

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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

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T/F: Resolution is better with higher frequency/smaller wavelength

True

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Order these organs based on increasing echogenicity:

Liver, Prostate, Spleen, Kidney (Cortex/Medulla)

Medulla

Cortex

Liver

Spleen

Prostate

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Describe the Compton effect

Atomic number independent (less tissue distinction)

Increases as kVp increases = less contrast

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What is it called when a structure has the same echogenicity as another structure? Give an example

Isoechoic

Liver and Kidney

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What could cause a radiograph to be underexposed?

kVp or mAs too low

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When viewing the sagittal plane, which way is the transducer facing?

Cranially

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What is edge shadowing?

Small shadow at the edge of round structures

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Which transducer is best when performing a cardiac US?

Sector transducer

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T/F: Radiolucent means an object appears darker?

True

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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

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What organs do you view on the left side?

Spleen

Left kidney

Bladder

Prostate/uterus

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What organs do you view on the right side?

Right kidney

Liver

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What are your DDx for a diffusely hyperechoic liver parenchyma?

Diabetus mellitus

Hyperadrenocorticism

Hepatic lipidosis

Lymphosarcoma

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Which transducer is best to use when performing an abdominal US?

Convex transducer

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What is the contrast medium in the abdomen?

Fat

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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?

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