Imaging Flashcards
What diseases don’t show many changes on a thoracic radiograph?
Pulmonary thromboembolism Acute viral pneumonia Acute & chronic tracheobronchitis Lungworm Upper airway disease Tracheal stenosis Bronchial foreign bodies Osteosarcoma mets
What false pathologies can GA create on radiographs?
Anaesthetic induced megaoesophagus
Atelectasis in lateral recumbency
What view should you always take first?
DV
Lateral will create artefact due to GA induced atelectasis
How can you assess rotation on a DV?
Position of the sternum relative to the dorsal spinous processes
How can you increase the diagnostic quality of a thoracic radiograph?
Inspiratory view
High KV/ low mAs technique - short exposure time reduces movement blur
What anatomical spaces are there in the thorax?
Pleural space
Thoracic wall
Mediastinum
Lungs
Name some focal lung pathologies. These will either have a craniodorsal or cranioventral distribution that needs to be described.
Pneumonia
Atelectasis
Haemorrhage
Name some generalised lung changes seen on radiography.
Fibrosis Bronchitis Pneumonia Oedema Haemorrhage Metastatic neoplasia
What pathologies cause mediastinal shift?
Pneumothorax
Masses
Describe the systematic approach you should take to interpreting a thoracic radiograph.
- Assess radiopacity
- Determine the anatomical compartment involved
- Assess thoracic boundaries - spine, sternum, ribs, diaphragm
- Consider the aetiology of the pathology
- Assess the lungs - opacity, volume, distribution of lesion
- Assess mediastinal shift
- Assess lung patterns
How does a bronchial pattern appear on a radiograph?
Increased radiopacity of the bronchial walls
= donuts and tramlines
What differential diagnosis would you consider with a bronchial pattern?
Calcification of the bronchi
Bronchitis - allergic, irritant, parasitic, idiopathic
Peribronchial cuffing - oedema, eosinophillic, neoplasia, pneumonia
Bronchiectasis
= widened bronchitis seen in chronic, severe disease
What is an alveolar pattern?
Increased cells or fluid (radiopacity) in the alveolar space
- border effacement
- lobar sign
- air bronchograms
= air in the bronchi stands out from the parenchyma as radiolucent
What does a generalised alveolar lung pattern suggest?
Haemorrhage
Pneumonia
Oedema
What does a focal alveolar lung pattern suggest?
Pneumonia Haemorrhage Oedema Primary or secondary lung tumour Infarction Lung lobe torsion Atelectasis
How does an interstitial pattern appear?
Increased fluid or cells in the interstitial space
Not as severe and not as well defined as an alveolar pattern
Usually occurs before the pathology spills over into the alveolar space
What differentials would you consider with an interstitial lung pattern?
Artefact - fat, expiration, underexposure
Ageing - pulmonary osteomata
Lymphoma
Metastatic neoplasia - diffuse or nodular
Pneumonitis - viral, parasitic, toxic or metabolic
Disease in transition
What size must a pulmonary nodule be to be picked up on radiography?
4-5mm
and surrounded by air
What pathologies can cause a diffuse decrease in radiopacity?
Artefact Hypovolaemia Hyperinflation Pneumothorax Pneumomediastinum Subcutaneous emphysema
What can cause a focal decrease in radiopacity in the lung?
Cavitatory lung lesion Emphysema Pulmonary thromboembolism Focal pneumothorax Focal pneumomediastinum
What radiographic changes will you see with a pleural effusion?
Border effacement of the heart and diaphragm
Pleural fissures
Retraction of the lung lobes from the margins of the chest wall
What radiographic changes will you see on a radiograph with pneumothorax?
Increased radiolucency in the pleural space (air)
Retraction of the lungs from the thoracic margins
Lungs appear more radiopaque
Elevation of the cardiac silhouette from the sternum
Mediastinal shift - opposite to the side with pneumothorax
What structures are contained in the mediastinum?
Heart and great vessels Oesophagus Trachea Sternal lymph nodes Thymus
What is the most common location of a mediastinal mass and how will this be seen on a radiograph?
Cranioventral mass
Widened mediastinum
Dorsal deviation of the trachea
Mild pleural effusion
How does pulmonary oedema appear on a radiograph?
Perihilar location
Initially interstitial pattern -> alveolar pattern when it spills over into the alveolar space
What is the typical distribution of aspiration pneumonia?
Cranioventral
Alveolar pattern
Radiographic signs does right sided CHF?
Hepatic congestion
Vena caval distension
Pleural effusion
Ascites
What radiographic signs does left sided CHF show?
Pulmonary oedema
Pouching of the left atrium
Pulmonary venous congestion
How can you do a vertebral heart score?
Measure the long axis of the heart
Measure the short axis of the heart
Compare to T4 - count the number of vertebrae that lie within length
What is the normal vertebral heart scores?
Dogs = 9.7 +/- 0.51 Cats = 7.5 +/- 0.32
What are the radiographic signs of left sided cardiac disease?
Dorsal deviation of the trachea
Tenting of the left atrium
Straightening of the caudal border of the heart
Compression of the bronchus caudal to the corina
Cowboy sign - divergence of the bronchi on DV
Perihilar alveolar pattern in the lungs (interstitial in early/mild)
Dilation of the lobar vessels
What are the radiographic signs of Right sided cardiac disease?
Increased cardiac width Rounding of the right side of the heart Reserve D shape on DV Increased right to left ratio Increased sternal contact (care in obese patients)
How can you assess the lobar vessels and what does their enlargement suggest?
Cranial lobar vessels - should be no bigger than the width of the proximal 1/3 of the 4th rib
Caudal lobar vessels - should be no bigger than the 9th rib where they cross
Venous congestion indicates left sided CHF
Congestion of the lobar arteries suggests pulmonary hypertension
How is the radiographic appearance of pulmonary oedema different in cats?
Patchy interstitial / alveolar pattern with a more variable distribution
May develop a pleural effusion in left sided CHF
(Unlike dogs that develop this in right sided CHF)
- border effacement, lobar sign, lung lobes retracted from wall
How does dilated cardiomyopathy appear on radiographs?
Massively enlarged cardiac silhouette (ddx pericardial effusion)
Signs of right and left atrial enlargement
Eg : left atrial - cowboy sign
Right atrial - increased sternal contact
What is the difference between the radiographic appearance of chamber enlargement in the cat?
Chamber enlargement is less specific in cats
= generalised cardiomegaly
How does a pericardial effusion appear on a radiograph?
Round, well defined enlargement of the cardiac silhouette
No specific chamber enlargement
What radiographic changes will you see in Pulmonic stenosis?
Post stenotic bulge over the pulmonary artery on DV
Small lobar vessels
Concurrent right sided enlargement with volume overload
What radiographic changes will you see with a PDA?
Decreased radiopacity of the lungs - increased pulmonary flow
Thick lobar vessels - increased pulmonary flow
Enlargement of the left side of the heart
Aortic enlargement
What radiographic signs will you see with a reverse PDA? (Hypertension with consequent right sided enlargement - cor pulmonae)
Right sided enlargement
What are the radiographic signs of a persistent right aortic arch?
Left deviation of the trachea
Ventral deviation of the trachea (megaoesophagus)
Focal megaoesophagus
What are the radiographic finding in a peritoneal pericardial diaphragmatic hernia?
Enlarged cardiac sillouhette
- due to gut contents in the pericardium
Looks like the diaphragm and pericardium communicate
- dorsomesothelial remnant
What would you suspect if you saw microcardia and radiopaque (hypo vascular) lungs?
Hypovolaemia
What does the right parasternal 4 chamber view tell us on echo?
Left ventricular and atrial shape
Contractility of the heart
Mitral valve
Atrial septum
Calculation of
End diastolic volume
End systolic volume
Ejection fraction
What are the normal dimensions on the right parasternal 4 chamber view?
Right heart is no more than 1/3 of the size of the left heart
Left ventricular walls are no more than 1/3 of the chamber diameter
What is the right parasternal 5 chamber view used for?
Assessing abnormalities of the aortic valve and left ventricular outflow tract
Doppler can be used to assess
- aortic stenosis
- aortic regurgitation
- ventricular septal defects
What are the 5 levels that you can look at on the right parasternal short axis view?
- Left ventricular apex
- Papillary muscle level
- Chordae tendinae level
- Mitral valve level
- Aortic level
What is the right parasternal short axis view used for at the level of the papillary muscles?
Positioning the cursors for M mode
At the tips of the papillary muscles
What is the right parasternal short axis view at the level of the mitral valve used for?
Mitral valve disease - irregular valve leaflets
Mitral valve stenosis - inadequate opening
Used to create the peaks on M mode
E peak - closure of mitral valve
A peak - opening of mitral valve
The space between the peaks indicates the length of diastolic filling
The greater the distance between the two indicates:
- Dilation
- Rounding of the left ventricle
- Poor stroke volume
What is the right parasternal short axis view used for at the level of the aorta?
Assessing the aortic valve leaflets
What is the left apical and parasternal views used for?
Imaging the long axis of the heart in the vertical plain
Can perform Doppler during this view - in line with the flow of the heart
*mist be parallel with flow to calculate the blood velocity
What is the subcostal view used for?
Measuring aortic outflow tract velocity in aortic stenosis
When do the smallest ventricular dimensions occur?
End systole
How can you measure fractional shortening and what value is normal?
Use M mode
Measure the distance between the left ventricular walls in diastole and in systole
FS = (distance in diastole - distance in systole) / disc in diastole
X100
Should be more that 25%
What does a fractional shortening of less than 25% indicate?
Poor heart contractility
What can make fractional shortening an unreliable measure of systolic function?
Significant mitral valve regurgitation
Wall motion abnormalities
Right sided heart disease associated with pressure overload
What is the pressure gradient across a heart valve?
4 x velocity^2
What is the normal e point septal separation of a dog? And what does this suggest?
<7mm
An increased E point septal separation indicates myocardial failure and is seen in DCM
What is the ejection fraction? And what is normal?
EF = (EDV - ESV) / EDV x 100
Normal >50%
A reduced ejection fraction indicates poor contractility and reduced volume of blood pumped out of the heart
= SV
What does a normal pulse wave spectral Doppler trace look like?
Peak above the line - flow towards the transducer
Peak below the line - flow away from the transducer
Pulse wave - peak velocity and depth limited
Continuous - peak velocity and depth not limited
Turbulent flow - filled in peak
What can colour flow Doppler show you?
Red - flow towards transducer
Blue - flow away from transducer
Green - turbulent blow flow
What view should you use to assess the diameter of the aorta and what is normal?
Right parasternal short axis view at the level of the aorta
Left atrium to aorta ratio should be less than 1.5
What echo abnormalities will you see with subaortic stenosis?
Increase aortic outflow tract velocity
Left ventricular septum and wall are thickened
What is normal aortic velocity? And what grades of aortic stenosis are seen?
Normal aortic velocity - <1.7m/s
Calculate the pressure gradient using the aortic velocity
PG = 4x velocity^2
0-40mmHg - mild
40-80mmHg - moderate
>80mmHg - severe
What abnormalities will you see with pulmonic stenosis?
Thickened right ventricular wall and septum
Increased pulmonic velocity
