Diagnostic Imaging: Principles, Thoracic 1 and 2

Question 1

Order the following from most radiopacity to most radiolucent?:

• Soft tissue
• Fat
• Mineral/bone
• Air
• Metal

Answer 1

Most radiolucent-

• Air
• Fat
• Soft tissue
• Mineral/bone
• Metal

Most radiopacity-

Question 2

How should radiographs be approached?

What are the different radiograph signs observed for?

Answer 2

Systematic approach- evaluated systemically and identified for abnormalities described in terms of radiographic signs

Signs- shape, number, size, location, opacity

Question 3

What is basic interpretation?

Answer 3

• Deviation from normal appearance recognises
• Lesion accurately described in systemic fashion
• Pertinent aspects of lesion appreciated from their description
• Formulation of DDXs

Question 4

What should be radiographically appraised?

Answer 4

• Ensure study is of correct patient and required regions imaged
• Ensure study is complete- two orthogonal views
• Identify views and check the labelling
• Assess the technical quality of the image- exposure, climate, collimation, positioning, contrast, artefacts
• Ensure you have previous relevant exams

Question 5

What are the different search techniques?

Answer 5

System based- evaluate all systems present

Hypothesis-driven- use history/results- increased chance of mistakes (bias)

Mneumonic approach- ABCDE muscular skeletal (alignment, bones, cartilage/joints, devices, everything else)

Inside out, outside in

Question 6

How does a description need to be systematically done?

Answer 6

• Number- number of masses- simple but important, could be the major abnormality
• Size- measurement diameter- be accurate, relative size can suffice- heart to thoracic vertebrae
• Shape- rounded smooth- overall shape, margins, definition of margins
• Location- cranial, caudal etc- use of anatomical landmarks when possible, can be more general
• Opacity- soft tissue opacity- 5 basic opacity, soft tissue not distinguishable from fluid- unless we use contrast

Consider the possibility that lesion is an artefact of poor positioning

Question 7

What is the mass effect?

What is effacement?

Answer 7

Mass effect- if something changes in size it will affect its surroundings, enlarged heart, dorsal trachea

Effacement- more complex than simply obscured- loss of normal contrasting opacity and so borders are lost, serosal detail (fat) allows visualisation of different structures in abdomen

Question 8

What are the limitations of anatomical imaging?

Answer 8

2D representation of 3D structures

That’s why 2 views are needed at 90 degrees- orthogonal views

Only anatomical- not a definitive diagnosis- great for foreign bodies, fractures, ectopic ureters, hernias, calculi

Only a snapshot in time

Doesn’t show anything to do with functionality

Question 9

What are the indications for a thoracic image?

Answer 9

• Coughing
• Dyspnea
• Regurgitation
• Cardiac disease
• Tumour hunt
• Trauma
• Weight loss
• Chest wall abnormalities

Question 10

Why can normal radiographs not mean there is no disease?

Answer 10

• PTE
• Acute viral pneumonia
• Acute and chronic tracheobronchitis
• Lungworm
• Upper airway disease

Question 11

Describe the radiographic technique for a thoracic image?

Answer 11

• Prevent rotation
• Wedges under sternum
• Assess costochondral junctions and where ribs articulate
• GA vs Sedation
• GA atelectasis- the collapse of lung lobe
• Keep in sternal recumbancy
• Always take dorsoventral first

Question 12

How should thoracic radiographs be interpreted?

Answer 12

Assess radiograph overall- quality, phase of respiration, body condition

Systemic approach- many blind spots- ribs, mediastinal disease, tracheal disease

Normal or abnormal- many anatomical variants, use radiographic signs

Effects of recumbency- different positions of diaphragmatic crura in left vs right lateral, cardiac silhouette differs

BCS- widespread mediastinum, increased apparent opacity of lungs

Species differences-
psoas muscles in cats- caudal lung lobes don’t fully fille the space and makes them look smaller
differences in cardiac shape

Question 13

What are the different lobes of the lung?

Answer 13

Right- cranial, medial, caudal, accessory

Left- cranio-cranial, cranio-caudal, caudal

Question 14

What is abnormal about these three radiographs?

Answer 14

Left- decreased opacity

Middle- normal (lol)

Right- increased opacity

Question 15

After determining opacity what needs to be assessed?

What can be identified with increased and decreased opacity?

Answer 15

Determine whether the change is pleural, mediastinum and lungs

Decreased opacity-
pleural space- pneumothorax
air within pleural space, retraction of lungs (atelectasis), evaluation of the cardiac silhouette

Increased opacity- increased fluid or loss of air
rule out artefacts- technique, obesity
increased opacity is often the abnormality
increased fluid/cells and/or loss of air

Question 16

What needs to be assessed regarding different thoracic boundaries?

Answer 16

Normal sternum and spine

Mass, gas or thickening of soft tissues

Assess each rib individually- ribs normal in number, shape, opacity, size and position

Consider- degenerative, congenital, trauma, infection, neoplasia

Question 17

What are thoracic wall masses often associated with?

Question 18

What can be seen with a pleural space effusion?

Answer 18

Border effacement- heart and diaphragm

Pleural fissures- fluid between lung lobes

Retraction of lung margins from the chest wall

May mask underlying pathology- masses

Question 19

What is in the mediastinum?

How are masses classified according to location?

What are the most common places for masses?

Answer 19

Mediastinum- trachea, oesophagus, heart and vessels, sternal lymph node

Location- cranioventral, central, craniodorsal etc

Most common location- lymph nodes, thymus

Question 20

What can cause decreased lung opacity?

What can the different causes be with diffuse, focal and apparent decrease in opacity?

Answer 20

• Increased gas
• Decreased soft tissue/fluid

Diffuse-
artefact, hypovolemia, hyperinflation

Focal-
cavitary lung lesion, emphysema, thromboembolus

Apparent-
pneumothorax, pneumomediastinum, subcutaneous emphysema

Question 21

What can cause lung volume increase/decrease?

What is a mediastinal shift?

Answer 21

Volume Increase- swelling/mass
Volume Decrease- collapse/atelectasis

Mediastinal shift- example of the mass effect-
mass/swelling pushes mediastinum away
collapse pulls mediastinum toward it

Question 22

Decide where from caudodorsal, generalised and cranioventral the following lesions appear?:

Oedema
Atelectasis
Pneumonia
Bronchitis

Answer 22

Caudodorsal- oedema, haemorrhage, atelectasis

Generalised- haemorrhage, metastatic neoplasia, atelectasis, oedema, fibrosis, bronchitis

Cranioventral- pneumonia, haemorrhage, atelectasis

Question 23

What are the 4 lung patterns?

Answer 23

Bronchial pattern

Vascular pattern

Interstitial pattern

Question 24

What causes a bronchial pattern?

How does it appear?

What are the DDXs?

What is bronchiestasis?

Answer 24

Increased visibility of bronchial walls- thickened or increased opacity

Appears as ‘tramlines’ and ‘donuts’

DDXs-
calcification- increased opacity
chronic bronchitis- allergic, irritant, parasitic
peribronchial cuffing- oedema, PIE/EBP, pneumonia, neoplasia

Bronchiectasis-
lack of tapering, widening bronchi
implicated chronic and severe disease

Question 25

What causes alveolar pattern of lungs? How does it appear? What are the DDXs for diffuse and focal?

Answer 25

Cells ± fluid replaces air the alveoli Increased lung opacity, border effacement of adjacent structures, air bronchograms, lobar if entire lobe effects DDXs- Diffuse- pneumonia, oedema, haemorrhage Focal- pneumonia, oedema, haemorrhage, primary/secondary tumour, lobe collapse, infarct, lung lobe torsion

Question 26

What causes an interstitial pattern? What are the most common causes? What are the DDXs for genuine diffuse? What can cause a nodular interstitial pattern? What are the potential pitfals?

Answer 26

Cells or fluid in interstitial tissue- blood vessels less distinctly seen Most commonly artefactually- expiration, obesity, underexposure DDXs- artefact, ageing, lymphoma, diffuse metastases, pneumonitis Nodular- secondary neoplasia is most common, artifactual also common nodules need to be 4-5mm and surrounded by aerated lung Pitfalls- pulmonary osteoma (mineralised and irregular)- older dogs normal end on blood vessels skin masses (nipples)

Question 27

What is the cardiac silhouette? How does forwards heart failure lead to reduced cardiac output? What does right and left backwards heart failure lead to?

Answer 27

Summation of the heart, pericardial contents and pericardium Forwards heart failure leads to reduced cardiac output Right backwards heart failure- vena cava congestion- ascites Left backwards heart failure- pulmonary congestion/oedema

Question 28

Left vs right lateral recumbency affects the shape of the cardiac silhouette Which image shows right/left lateral recumbency?

Answer 28

Left is right image Right is left image

Question 29

Answer 29

Thought its useful to look at

Question 30

What is a vertebral heart score? What is normal in dogs and cats?

Answer 30

Compare the size of the silhouette (sum of short and long axis) to the vertebral length Dogs- 9.7 ± 0.5 Cats- 7.5 ± 0.3^2

Question 31

How can left-sided heart disease be seen on a radiograph?

Answer 31

Tracheal elevation from left ventricular enlargement Straightening of the caudal cardiac border- left ventricular enlargement Left atrial enlargement or 'tenting' May see bronchial compression cudal to carina Divergence of caudal mainstem bronchi to more than 60-90 degrees

Question 32

What are the signs of right-sided heart disease on a radiograph?

Answer 32

Increase in cardiac width and rounding of right size Increased R:L ratio Increased sternal contact- beware of obesity Reverse D on Dorsoventral view

Question 33

What pulmonary vessels can be evaluated in dogs and cats? How big/small should they be?

Answer 33

Cranial and caudal lobar vessels can usually be elevated in cats and dogs Usually not significantly wider then proximal 3rd of the 4th rib

Question 34

What is seen in a dog and cat radiograph with cardiogenic pulmonary oedema?

Answer 34

Interstitial (early/mild) or alveolar (late/severe) perihilar/caudodorsal predisposition Left-sided cardiomegaly is often apparent Maybe pulmonary vascular enlargement Cats- much more variable distribution often patchy interstitial/alveolar pattern cats with predominantly left-sided failure may develop pleural effusion

Question 36

What type of dogs are more prone to mitral valve disease? What is the typical pattern on a radiograph? What happens when in failure?

Answer 36

Tends to be smaller dog breeds Typical pattern of progressive left atrial enlargment Ultimately pulmonary oedema

Question 37

What dogs are more affected by dilated cardiomyopathy? What is seen on a radiograph?

Answer 37

Often large breed dogs Often significant if clinical- less obvious if deep-chested Significant left atrial ± right-sided enlargement

Question 38

What are the different cardiomyopathies in cats? Which is the most common? Why is generalised cardiomegaly usually seen?

Answer 38

Hypertrophic (HCM)- most common Dilated (DCM) Restrictive (RCM) Unclassified (UCM) chamber enlargement is not specific in cats- more generalised

Question 39

What is pericardial effusion? What causes it? How does it appear on a radiograph?

Answer 39

Fluid within the pericardial space Can be idiopathic or secondary to masses Round sometimes well-defined cardiac silhouette Generally no-specific chamber enlargement evident Subtle evidence of cause may be apparent

Question 40

What are the different common cardiovascular congenital diseases? How doe they appear on a radiograph?

Answer 40

Pulmonic stenosis- stenosis of pulmonary artery can see post-stenotic bulge, right-sided hypertrophy (backwards D) Patent ductus arteriosus- Increased pulmonary flow- left-sided enlargement and aortic enlargement Persistent right aortic arch- Most common vascular ring anomaly left displacement of the trachea and deviation of left consistent sign, megaoesophagus Peritoneal-pericardial diaphragmatic hernia

Question 41

What can hypovolaemia result in?

Answer 41

Results in micro-cardia and hypo-vascular lungs