Thorax Practical Flashcards
what are the 4 radiographic views that can be used to assess the thorax of dog and cat
- right lateral
- left lateral
- dorsoventral
- ventrodorsal
which views are most commonly used in practice
right lateral and dorsoventral
how is the animal placed for right lateral view
right lateral recumbency and beam passes from left to right
how is the animal positioned in left lateral views
left lateral recumbency and beam passes from right to left
how is the animal positioned in a dorsoventral view
sternal recumbency and beam passes from dorsal to ventral
how is the animal positioned for ventrodorsal views
dorsal recumbency and beam passes from ventral to dorsal
Can you remember what the different options might be for restraining animals for thoracic radiography?
Unconscious – general anesthesia
Conscious – sedation / unsedated is animal quiet or sick
Physical restraint - positioning aids eg sandbags, ropes etc
Manual restraint – held by person in protective lead lined clothing
In the UK, which of these options would only be indicated in the case of an animal with severe dyspnoea / respiratory distress and why is this the case?
Manual restraint – risk to human from ionising radiation should be minimised and permitted dose when performing veterinary radiography is zero so need very good reason to do this in the UK.
How do you think the presence of dyspnoea / respiratory distress would affect the quality of the resulting radiograph?
Poor quality image due to movement blur.
Sedating/anaesthetising animals with respiratory distress may be contraindicated but the converse argument would be that at least you would be more likely to get diagnostic radiographs!
Why is it important to pull the forelegs as far forward / cranially as possible when radiographing the thorax?
To remove the triceps muscle mass from overlying the cranial region of the thorax on the radiograph.
The heart appears to be a different shape in the right and left lateral views? Why do you think this is the case?
The heart is fixed in position at the base by the great vessels but the apex is mobile and so in lateral recumbency the apex of the heart moves with gravity.
The apex naturally sits to the left so when the animal is in right lateral recumbency the apex falls towards midline and is held there so the heart is projected “side on”.
In L Lat views, the apex falls towards the L thoracic wall so the heart is projected more along its length
The heart appears to be a different shape in the Dorsoventral and Ventrodorsal views? Why do you think this is the case?
The heart is fixed in position at the base by the great vessels but the apex is mobile and so in dorsal recumbency (Ventrodorsal view) the apex of the heart falls with gravity towards the vertebral column and so the heart appears elongated.
In ventral recumbency, (Dorsoventral view) the heart has a more natural, upright position in the thorax with the apex located towards to sternum and therefore appears more rounded.
There is also increased contact with the diapgrham in this view
Why do you think the blood within the heart is not visible on radiographs?
Fluid produces the same opacity as soft tissue on radiographs.
The fluid and myocardium are superimposed onto each other.
What is the vertebral heart score in this dog and how would you assess its heart relative to the intercostal spaces and height of the thorax? Is this dog normal?
VHS approx 12. Heart slightly greater than 2/3 height and width of thorax. Suggested slightly enlarged
When assessing a dog with cardiac abnormalities what information does radiography provide about the heart?
Overall Size, Shape, Specific chamber enlargement, Location, Evidence of congestive failure (pulmonary oedema, etc)
What information does radiography not provide about the heart?
Internal structures of heart (valve leaflets, ventricular septum, etc) myocardial function or valve incompetence
Why do the lung lobes appear dark on radiographs?
Air filled therefore do not attenuate the X-Ray bean resulting in increased blackening of the film – described as being radiolucent
Why are the blood vessels in the lung visible?
They are a combination of fluid (blood) and soft tissue (vessel walls) and so are radio-opaque (grey) while the surrounding lung is air filled and therefore radiolucent (dark)
Why do you think the lungs look clearer in the L lateral view of one dog than the R lateral view of the other?
The lungs are better aerated in the L Lat view and therefore there is better contrast between the air filled lung and the vascular structures of the lungs and also the other soft tissue structures of the thorax.
This could be due to a number of reasons – stage of respiratory cycle image was taken at, GA v conscious dog, presence of respiratory disease, breed (eg. Brachycephalic) etc
What anatomical features allow you to recognise this as a cat and not a dog?
Clavicle, square olecranon, long fine vertebral bodies etc
What is the triangular arrow pointing to and what does this tell you about the cat?
Endotracheal tube – cat was under GA
Why are all the abdominal structures so well delineated in this cat? Which organs can you recognise and what is labelled *?
Presence of intraluminal fat – radiolucent areas between organs.
Falciform fat
Liver, stomach, left and right kidneys, small and largeintestine
what are the lines demonstrating
crura of the diaphragm parallel in right lateral view
heart long and in contact with sternum
what is demonstrated by the lines
crura of diaphragm V shaped left lateral
heart shorter, rounded and less contact with sternum
what are the lines demonstrating
2 bulges to diaphragm
heart rounded
increased contact between heart and diaphragm
what is demonstrated by the lines
3 subtle bulges to diaphragm
heart elongated
less contact between diaphragm and heart
what are the structures shown
- left ventricle
- left atrium
- right ventricle
- right atrium
- aorta
- caudal vena cava
what are the structures shown
- left ventricle
- left atrium
- right ventricle
- right atrium
- aorta
- caudal vena cava
Why does the presence of pulmonary oedema cause an increase in opacity of the lung?
Fluid replaces air in the alveoli therefore lung no longer radiolucent. Fluid attenuates the beam producing areas of soft tissue opacity.
How would you go ab out obtaining more information about the valvular and myocardial function in this dog?
Perform an ultrasound examination / echocardiography
what are the structures
- trachea
- carina
- bronchi
- a. left cranial lung lobe - cranial part
- b. left cranial lung lobe - caudal part
- left caudal lung lobe
- right cranial lung lobe
- right middle lung lobe
- right caudal lung lobe
- accessory lung lobe
- pulmonary blood vessels
what are the structures numbered
- trachea
- carina
- bronchi
- a. left cranial lung lobe - cranial part
- b. left cranial lung lobe - caudal part
- left caudal lung lobe
- right cranial lung lobe
- right middle lung lobe
- right caudal lung lobe
- accessory lung lobe
- pulmonary blood vessels
the trachea is superimposed onto the vertebral column