Diagnostic Imaging: Principles, Thoracic 1 and 2 Flashcards
Order the following from most radiopacity to most radiolucent?:
- Soft tissue
- Fat
- Mineral/bone
- Air
- Metal
Most radiolucent-
- Air
- Fat
- Soft tissue
- Mineral/bone
- Metal
Most radiopacity-
How should radiographs be approached?
What are the different radiograph signs observed for?
Systematic approach- evaluated systemically and identified for abnormalities described in terms of radiographic signs
Signs- shape, number, size, location, opacity
What is basic interpretation?
- Deviation from normal appearance recognises
- Lesion accurately described in systemic fashion
- Pertinent aspects of lesion appreciated from their description
- Formulation of DDXs
What should be radiographically appraised?
- 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
What are the different search techniques?
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
How does a description need to be systematically done?
- 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
What is the mass effect?
What is effacement?
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
What are the limitations of anatomical imaging?
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
What are the indications for a thoracic image?
- Coughing
- Dyspnea
- Regurgitation
- Cardiac disease
- Tumour hunt
- Trauma
- Weight loss
- Chest wall abnormalities
Why can normal radiographs not mean there is no disease?
- PTE
- Acute viral pneumonia
- Acute and chronic tracheobronchitis
- Lungworm
- Upper airway disease
Describe the radiographic technique for a thoracic image?
- 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
How should thoracic radiographs be interpreted?
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
What are the different lobes of the lung?
Right- cranial, medial, caudal, accessory
Left- cranio-cranial, cranio-caudal, caudal
What is abnormal about these three radiographs?
Left- decreased opacity
Middle- normal (lol)
Right- increased opacity
After determining opacity what needs to be assessed?
What can be identified with increased and decreased opacity?
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
What needs to be assessed regarding different thoracic boundaries?
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
What are thoracic wall masses often associated with?
What can be seen with a pleural space effusion?
Border effacement- heart and diaphragm
Pleural fissures- fluid between lung lobes
Retraction of lung margins from the chest wall
May mask underlying pathology- masses
What is in the mediastinum?
How are masses classified according to location?
What are the most common places for masses?
Mediastinum- trachea, oesophagus, heart and vessels, sternal lymph node
Location- cranioventral, central, craniodorsal etc
Most common location- lymph nodes, thymus
What can cause decreased lung opacity?
What can the different causes be with diffuse, focal and apparent decrease in opacity?
- Increased gas
- Decreased soft tissue/fluid
Diffuse-
artefact, hypovolemia, hyperinflation
Focal-
cavitary lung lesion, emphysema, thromboembolus
Apparent-
pneumothorax, pneumomediastinum, subcutaneous emphysema
What can cause lung volume increase/decrease?
What is a mediastinal shift?
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
Decide where from caudodorsal, generalised and cranioventral the following lesions appear?:
Oedema
Atelectasis
Pneumonia
Bronchitis
Caudodorsal- oedema, haemorrhage, atelectasis
Generalised- haemorrhage, metastatic neoplasia, atelectasis, oedema, fibrosis, bronchitis
Cranioventral- pneumonia, haemorrhage, atelectasis
What are the 4 lung patterns?
Bronchial pattern
Vascular pattern
Interstitial pattern
What causes a bronchial pattern?
How does it appear?
What are the DDXs?
What is bronchiestasis?
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
What causes alveolar pattern of lungs?
How does it appear?
What are the DDXs for diffuse and focal?
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
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?
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)
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?
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
Left vs right lateral recumbency affects the shape of the cardiac silhouette
Which image shows right/left lateral recumbency?
Left is right image
Right is left image
Thought its useful to look at
What is a vertebral heart score?
What is normal in dogs and cats?
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
How can left-sided heart disease be seen on a radiograph?
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
What are the signs of right-sided heart disease on a radiograph?
Increase in cardiac width and rounding of right size
Increased R:L ratio
Increased sternal contact- beware of obesity
Reverse D on Dorsoventral view
What pulmonary vessels can be evaluated in dogs and cats?
How big/small should they be?
Cranial and caudal lobar vessels can usually be elevated in cats and dogs
Usually not significantly wider then proximal 3rd of the 4th rib
What is seen in a dog and cat radiograph with cardiogenic pulmonary oedema?
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
What type of dogs are more prone to mitral valve disease?
What is the typical pattern on a radiograph?
What happens when in failure?
Tends to be smaller dog breeds
Typical pattern of progressive left atrial enlargment
Ultimately pulmonary oedema
What dogs are more affected by dilated cardiomyopathy?
What is seen on a radiograph?
Often large breed dogs
Often significant if clinical- less obvious if deep-chested
Significant left atrial ± right-sided enlargement
What are the different cardiomyopathies in cats?
Which is the most common?
Why is generalised cardiomegaly usually seen?
Hypertrophic (HCM)- most common
Dilated (DCM)
Restrictive (RCM)
Unclassified (UCM)
chamber enlargement is not specific in cats- more generalised
What is pericardial effusion?
What causes it?
How does it appear on a radiograph?
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
What are the different common cardiovascular congenital diseases?
How doe they appear on a radiograph?
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
What can hypovolaemia result in?
Results in micro-cardia and hypo-vascular lungs
