VETM3440 - Clinical Medicine II - Diagnostic Imaging Test 1 (Thoracic Radiology)

From Antonina Degroot set via quizlet

Describe how radiographs are made

- Electrons products at the cathode are sent to the anode in a vacuum at an accelerated speed
- Electrons interact with anode to release x-rays
- X-rays directed to patient and absorb, scatter or transmit
- They hit detector and an image is created (black where x-rays hit, white where they did not)

What two factors can we adjust? Explain them and what increasing them will do to the radiograph.

kVP:

- The potential across the tube (difference in electrical charge)

- Energy of x-rays

mAs:

- Number of x-rays

*increasing either increases exposure*

What are the six Roentgen signs?

Size

Margin

Shape

Opacity

Number

Location

"show me something obvious now lady"

What is opacity a function of?

Tissue type and thickness

Lightest opacity on radiograph?

Metal

Darkest opacity on radiograph?

Air

What is summation?

A special type of superimposition which creates a new opacity which is not actually present in the patient

What does negative summation versus positive summation do?

Negative summation:

- Decreases the opacity artificially (makes things look lighter)

- Ex. Overlapping gas

Positive summation:

- Increases the opacity artificially (makes things look darker)

- Ex. End on vessels overlapping on poles of kidneys

What is silhouetting/border effacement?

Two structures of the same opacity come into contact and you can no longer distinguish them from one another

How does magnification work when taking a radiograph?

Objects farther from the plate are magnified (think of a shadow)

How do we name a radiograph?

From where the beam enters to where the beam exits

Ex.

- Right lateral means that the beam enters from the left and exits on the right

- Ventral dorsal means that the beam enters ventrally and exits dorsally

What features are visible on radiograph in left sided cardiomegaly?

Lateral views:

- Wide and tall heart

- Dorsal tracheal elevation

- Flattened caudodorsal margin

DV/VD Views:

- Left atrium has a rounded opacity/enlargement at 6 o'clock position

- Left auricle 2-3 o'clock is enlarged

- In cats, their heart looks like a "❤️"

What features are visible on radiograph in right sided cardiomegaly?

Lateral views:

- Increased sternal contact

- Rounded cranial margin

- Increased volume of cardiac silhouette cranial to carina

DV/VD Views:

- Heart appears in a reverse "D" shape

- Right atrium at 9-11 o'clock is enlarged

- Mean pulmonary artery at 1-2 o'clock is enlarged

Why is right sided cardiomegaly exceptionally rare?

It means there would be obstruction of blood flow into the lungs

Where are pulmonary veins?

They are located 'central and ventral'

What are the characteristics of pulmonary veins?

- They should be smaller than the 4th rib in lateral and 9th rib in VD as they cross
- They're the same size as their accompanying artery

What is a sign of enlargement (pulmonary hypertension) of a pulmonary artery?

Tortuosity (wiggly) is a sign of enlargement

What are some components of normal lung anatomy?

- Veins are ventral and central
- Arteries and veins are the same size
- We should normally see vessels and airway markings, but not going to see alveoli

List the four pulmonary patterns

1. Unstructured interstitial
2. Structured interstitial
3. Alveolar pattern
4. Bronchial pattern

Describe an unstructured interstitial pattern

- Increased pulmonary opacity
- Partial obscuration of vascular markings
- Can be focal, multifocal or generalized
- Hazy looking

Describe a structural interstitial pattern

Presence of nodules or masses

Describe an alveolar pattern

- Increased pulmonary opacity

- Complete obscuration or vascular markings/ pulmonary vessels

Hallmarks of an alveolar pattern include:

- Air bronchograms

- Lobar sign

*don't need both to be considered alveolar*

What is an air bronchogram?

Air filled (dark) airways completely surrounded by white (kind of looks like a dead Christmas tree)

What is a lobar sign?

An aerated lung against a non-aerated lung

What is the definition of a bronchial pattern? What do you see?

Thickened airways - you should see little "donuts" (little white circles with black in the inside) and lines

How big should vessels be?

No bigger than ribs

How wide should the heart be?

2.5 - 3 intercostal spaces

What is the pleural space?

It is a theoretical space between the lungs and heart, you shouldn't see it normally

List the abnormalities that can occur in the pleural space

- Pleural fissures
- Gas
- Pleural effusion (fluid)
- Pneumothorax (collapsed lungs)
- Extrapleural sign (mass)

What are pleural fissures? Where are pleural fissures located? What do they indicate?

They are thin lines along the margins, between lung lobes - they can indicate scant effusion (get wider as effusion increases in volume)

Where should lungs normally go to?

The body wall

What is a sign of pleural effusion?

Lungs not touching the body wall - the fluid in the pleural space won't let the lungs fully expand

What are some visual indicates of pneumothorax?

- Gas in pleural space
- Lungs retracted
- No lung markings (vessels, bronchi) in air filled regions
- Dorsal deviation of the heart

What is an extrapleural sign?

A specific radiographic feature that helps distinguish pulmonary from extra pulmonary masses or lesions

Pulmonary masses:

- Make an acute angle with the body wall

Extra pulmonary masses:

- Make an obtuse angle with the body wall

What are the contents of the mediastinum?

- Vessels
- Lymphatics and lymph nodes
- Fat
- Esophagus
- Trachea
- Heart/pericardium
- Thymus (in young animals)

How can you tell that there is a cranial mediastinal mass?

The cranial mediastinum will appear widened

Two reasons why the trachea would be narrowed?

- Tracheal collapse
- Tracheal mass

How does a heart based mass look on radiograph in a lateral versus a DV/VD?

- Deviates trachea dorsally immediately cranial to the heart
- Sometimes deviates trachea laterally in a DV/VD

Where do esophageal foreign bodies often get stuck?

At the thoracic inlet, heart base or lower esophageal sphincter

What do esophageal foreign bodies appear as on radiograph?

Mineral or soft tissue structures in the esophagus

What is megaesophagus?

It is the dilation of the esophagus (may be focal or diffuse)

What is pneumomediastinum?

A condition where gas is present in the mediastinum

Three diseases of diaphragm

1. Hiatal hernia
2. Diaphragmatic hernia
3. Peritoneal-pericardial diaphragmatic hernia

What is hiatal hernia? What does it look like on radiograph?

- Herniation of gastric cardia into caudal aspect of the thorax (part of the stomach pushes cranially into thorax)
- Cranially rounded soft tissue or gas structure in plane with esophagus, broad base to diaphragm

What is diaphragmatic hernia?

Herniation of abdominal contents into the thorax (look for liver, spleen, intestines)

What is peritoneal-pericardial diaphragmatic hernia (PPDH) caused by?

- Failure of a midline fusion during development (it is always congenital, never traumatic)
- There are abdominal contents in the pericardial sac

What will PPDH look like?

- If its just the liver, it will appear as a soft tissue opacity
- If there is an intestine, than there will be tubule structures filled with gas

Why would dorsal deviation of the trachea be an artifact and not a true finding?

Due to neck position the trachea can be dorsally deviated (to decide if this is an artifact you can retake views or correlate clinical signs)

How are we able to tell if a mass is pulmonary or not?

Pulmonary masses shouldn't push against the heart