Introduction to Thoracic
Radiology
Dr. Meghan Woodland
September 30, 2010.
Indications
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Coughing
Dyspnea / Tachypnea
Heart Murmur, Collapse
Primary or Secondary Neoplasia
– Check for metastasis
• Thoracic Trauma
• Chest Wall Mass
• Exercise Intolerance, Weight Loss
Technical Factors
• Potential for Movement
– Respiration
– Decrease mAs
• High inherent contrast
– High kVp
• Collimation
– Should include thoracic
inlet to diaphragm
• Center over the heart
• Pull thoracic limbs
forward
Radiographic techniques: the dog
By Joe P. Morgan, John Doval, Valerie Samii
Determining the Phase of
Respiration
• Always expose at peak inspiration
– Maximizes lung contrast
– Better visualization of pulmonary parenchyma
– Less compression of lungs by diaphragm
• Inspiratory lateral view:
– Caudodorsal aspect of lung is caudal to T12
– Increased aeration of accessory lung lobe
– Separation of cardiac silhouette and diaphragm
• Inspiratory VD/DV view:
– Diaphragmatic cupola caudal to mid-T8
– Tips of lung caudal to T10
Inspiratory vs. Expiratory Lateral
Notice size of triangle
Inspiratory vs. Expiratory VD
Easy to see the difference in well
visualized lung
DV vs. VD
• DV
– Best view to evaluate cardiac silhouette and
caudal pulmonary vessels
– Less stressful for the patient
– Diaphragm rounded
– See small amounts of pleural air
• VD
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Best view to evaluate lungs
Heart appears elongated
Flat diaphragm – Mickey Mouse ears
See small amounts of pleural fluid
DV
VD
DV vs. VD
Right vs. Left Lateral
• Caudal Vena Cava
enters the right
diaphragmatic crus
• Right Lateral
– Better cardiac detail
– R crus forward
• See CVC go into it
• Left Lateral
– Heart appears round
– L crus forward
• See Cava go past
Caudal vena cava
Left or Right Lateral?
Left or Right Lateral?
The Effects of Lateral
Recumbency
• Lung lesions (mass, nodule, infiltrate)
may only be seen on a single view
• Only the non-dependent (up) lung can
be critically evaluated
– Dependent lung loses aeration
(atelectasis)
• Increased opacity
• Silhouettes with lesions
Sedation Induced Atelectasis
Interpretation of Thoracic
Radiographs
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Systematic approach is crucial
Heart (Cardiac Silhouette)
Lungs
Mediastinum
Pleural space
Chest wall
Bones, Abdomen, Neck
Normal Cardiac Silhouette
• Size is subjective
• Lateral views:
– Dog = 2 ½ - 3 ½ intercostal spaces
– Cat = 2 – 2 ½ intercostal spaces
• VD/DV views:
– 65% the width of the thorax
• Objective:
– Buchanan method
• Vertebral heart scale
Clock Face
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11-1 Aortic Arch
1-2 Main Pulmonary Trunk
2-3 Left Auricle
2-5 Left Ventricle
5-9 Right Ventricle
9-11 Right Atrium
Centrally – Left Atrium
Lateral View
• Make a Plus sign
• Bermuda triangle
– Right atrium
– Main pulmonary artery
– Aortic Arch
• Left atrium
• Left Ventricle
• Right Ventricle
Thoracic and Pulmonary
Vessels
• Aorta
• Caudal Vena Cava
• Cranial pulmonary
vessels
– Proximal third rib
• Caudal pulmonary
vessels
– Where crosses 9th rib
• Veins are ventral and
central
– Artery, bronchus, vein
– ABV’s
Trachea, Bronchial Tree
• Trachea ends at the carina
• Then splits to the main stem bronchi
followed by the lobar bronchi
• Tracheal rings can mineralize (age)
• Decreased tracheal diameter
– Tracheal narrowing (stenosis, extramural
compression)
– Tracheal hypoplasia
– Tracheal collapse
Lungs
• Normal anatomy
1
– Left
• Cranial (cranial
subsegment) 1
• Cranial (caudal
subsegment) 2
• Caudal 3
– Right
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Cranial 4
Middle 5
Caudal 6
Accessory 7
4
2
5
3
6
7
The Mediastinum
• Cranial, middle, caudal compartments
• Routinely visible structures:
– Cardiac silhouette, trachea, caudal vena
cava, aorta, +/- thymus, +/- esophagus
– Cranioventral mediastinal reflection
– Caudoventral mediastinal reflection
• Aka phrenopericardiac ligament
• Left side on VD radiograph
Mediastinal Reflection
Caudoventral mediastinal reflection
Extrathoracic Structures
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Sternum
Vertebrae
Ribs
Adjacent soft
tissues
• Diaphragm
The Diaphragm
• Cupola
– Cranioventral convex
portion
• Right and left crura
– Attach to cranioventral
border of L3 and body of
L4
– May cause irregularity on
these surfaces
• Appearance depends on
centering of X-ray beam
The Diaphragm
The End