Introduction to Thoracic Radiology Dr. Meghan Woodland September 30, 2010.
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Transcript of Introduction to Thoracic Radiology Dr. Meghan Woodland September 30, 2010.
Introduction to Thoracic Introduction to Thoracic RadiologyRadiology
Dr. Meghan Woodland
September 30, 2010.
Indications
• 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
forwardRadiographic 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 – 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 pastCaudal 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
• 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
• 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– Left
• Cranial (cranial subsegment) 1
• Cranial (caudal subsegment) 2
• Caudal 3
– Right• Cranial 4
• Middle 5
• Caudal 6
• Accessory 7
1
2
3
4
5
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
• 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