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