Radiology of Tissues Surrounding the Thorax Flashcards
Indications for thoracic radiographs.
Assessment of cardiac failure.
Characteristics of lung disease.
Detection of metastasis.
Work-up of cases where:
- Coughing / dyspnoea.
- Heart murmur.
- Trauma.
- Regurgitation.
- Collapse / cyanosis.
Pre-anaesthetic check / other screening.
Standard views for thoracic radiograph.
Dorsoventral (sternal recumbency):
- Take first – avoids atelectasis (min. lung collapse).
- Preferable for heart.
- Dyspnoeic animals.
Ventrodorsal (dorsal recumbency):
- Lungs / small pleural effusion.
- Avoid if dyspnoeic.
Right lateral.
Left lateral.
lateral projections named according to the side they are lying on.
Identifying left vs right lateral view radiographs.
Diaphragm varies in position / shape.
- Lowest (dependent) crus is most cranial.
- Caudal vena cava passes through right side so seen to cross the cranial aspect of diaphragm on left lateral view.
- Gastric fundus +/- gas is further cranial on left lateral view.
Dorsoventral vs ventrodorsal views of the thorax.
Dorsoventral gives single dome diaphragm.
Ventrodorsal gives more of a 3-dome diaphragm.
The diaphragm and its use in thoracic radiography.
Position of diaphragm can help assess stage of resp. cycle at time of radiograph:
- Expiratory:
– diaphragm upright and in contact w/ or overlapping cardiac silhouette.
- Inspiratory:
– caudally sloping w/ minimal or no contact between cardiac silhouette and diaphragm.
- Is inspiratory or expiratory preferable on radiograph?
- When may an expiratory view be desirable?
- Inspiratory. Pathologies can be missed due to superimposing structures in expiratory views.
- Detection of bullae.
- To confirm tracheal collapse.
- Detection of ‘air trapping’ (emphysematous change).
- Detection of a small pneumothorax.
- Detection of bullae.
Technical considerations for thoracic radiographs…
1. Positioning.
2. Movement.
3. Exposure.
4. Other?
- Aim to get thorax straight.
- Costo-chondral junctions superimposed on lateral.
- Spine/sternum superimposed on dorsoventral.
- Pull forelegs forward. - Consider sedation/GA.
Keep exposure times short. - High kV technique (helps keep exposure time low).
+/- grid (helpful to reduce scatter, but have to up exposure times). - Remove collars, leads etc.
Systematic approach for radiograph viewing.
- Peripheral soft tissue structures and cranial abdominal contents.
- Vertebrae, sternum, ribs.
- Pleural cavity and mediastinum.
- Trachea and lungs.
- Heart and blood vessels.
Peripheral soft tissues.
- Check cranial abdomen for the presence and position of normal viscera.
- Look for defects, swellings, FBs, emphysema, subcutaneous emphysema
- Metallic (shotgun pellets).
Diaphragmatic rupture.
- Visible integrity of diaphragm not v helpful.
- More helpful is the presence of abdominal viscera in the thorax.
- AND/OR absence of abdominal organs from their normal position in the abdomen.
- US if less identifiable.
Vertebrae, sternum, ribs.
Check alignment of vertebral bodies and of sternebrae.
- trauma.
- congenital sternal anomalies are common and usually identifiable.
Rib lesions (e.g. tumours) particularly easy to overlook so consciously check along each rib.
- Costal cartilages may mineralise at a young age and can look v patchy and irregular, esp. in dogs.
Rib fractures.
- Recent rib fractures have clearly defined edges w/ no sign of bone proliferation or mineralised callus.
- May be associated w/ subcutaneous emphysema.
- Several adjacent fractured ribs result in an unstable section of chest wall.
– ‘flail’ chest (uncommon). - Healed rib fractures have smooth bony callus at the site of the original fracture.
Pleural cavity.
- Potential space between visceral and parietal pleura surrounding lungs.
- Forms closed cavity.
- May occasionally see pleural reflections between lung lobes as thin lines, if aligned w/ x ray beam.
- Mediastinum.
- Cranial mediastinum on radiograph (DV/VD view).
- Formed between parietal layers of the 2 pleural cavities.
Continuous with the fascial planes of the neck cranially and the retroperitoneal space caudally. - Ill-defined soft tissue ‘band’.
- Contains cranial vena cava, arteries, LNs, nerves, fat, oesophagus and trachea.
- Not > 2x width of spine on dorsoventral view in the dog.
– can be wider normally in fat animals / brachiocephalic breeds.
- Not > 1x width of spine on dorsoventral view in the cat.
- Edges should be straight.
- Ill-defined soft tissue ‘band’.
- Caudal mediastinum (DV/VD view).
- Cranial mediastinum (lateral view).
- Fine radiopaque line between cardiac apex and left crus of diaphragm on DV/VD view.
- ‘Cardiophrenic ligament’.
- Just to left of midline.
- Fine radiopaque line between cardiac apex and left crus of diaphragm on DV/VD view.
- Ill-defined area of soft tissue above and below trachea.
Cranioventral mediastinal reflection representing tip of left lung lobe. (due to normal asymmetry of the lung lobes) – important to recognised so not over-interpreted as pathological.
