1. Introduction to Thoracic Radiology
Dr. Meghan Woodland
September 30, 2010.

2. Indications Coughing Dyspnea / Tachypnea Heart Murmur, Collapse
Primary or Secondary Neoplasia
Check for metastasis
Thoracic Trauma
Chest Wall Mass
Exercise Intolerance, Weight Loss

3. Technical Factors Potential for Movement High inherent contrast
Respiration
Decrease mAs
High inherent contrast
High kVp
Collimation
Should include thoracic inlet to diaphragm
Center over the heart
Pull thoracic limbs forward
High kVp and low mAs will reduce the naturally high contrast in the thorax and increase the lung detail visible.
Radiographic techniques: the dog
 By Joe P. Morgan, John Doval, Valerie Samii

4. Normal lateral thorax

5. Patient is rotated
Abdomen should be collimated out

6. 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
In anesthetised patients, it may be necessary to manually inflate the lungs. As well, in sedated/anesthetised patients, you should obtain the DV/VD view before the laterals, because anaesthesia-induced atelectasis may arise quickly after induction. This is especially true in large or overweight dogs.

7. Inspiratory vs. Expiratory Lateral
Notice size of triangle

8. Inspiratory vs. Expiratory VD
Easy to see the difference in well visualized lung

9. 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

10. DV VD

11. DV vs. VD

12. Normal VD Thorax

13. Normal DV Thorax

14. Cranial thorax has been collimated out of image.

15. Radiograph should be centered at the thorax.

16. Patient is rotated!

17. 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

18. Left or Right Lateral?
Right lateral

19. Left or Right Lateral?
Left lateral

20. 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
Dependent lung loses aeration because of the increased pressure from mediastinal structures (especially the heart) and the dependent crus of the diaphragm. This is even more increased in anesthetised patients.

21. Sedation Induced Atelectasis

22. Interpretation of Thoracic Radiographs
Systematic approach is crucial
Heart (Cardiac Silhouette)
Lungs
Mediastinum
Pleural space
Chest wall
Bones, Abdomen, Neck
Structures seen on thoracic radiographs.
Also evaluate for radiographic quality.
Don’t forget the extrathoracic structures.

23. 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
Cardiac silhouette includes: pericardium, pericardial fluid, myocardium (including epicardium and endocardium), the origins of major vessels and blood.
Size of the cardiac silhouette on radiographs is breed dependent. Barrel-chested dogs such as the Bulldog, Yorkshire Terrier and Dachshund have a relatively large cardiac silhouette on lateral radiographs. Deep-chested dogs, such as the Doberman, have taller, more slender cardiac silhouettes.
Vertebral heart scale:
On the lateral radiograph, the distance between the ventral aspect of the carina and the cardiac apex is taken as length.
The width is the maximum width of the heart perpendicular to the length line.
The number of vertebral lengths is taken for length and width, beginning at T4.
Dogs: normal = 9.2 – 10.2 (>10.5 is cardiomegaly)
Cats: normal = 7.2 – 7.8 (>8.1 is cardiomegaly)

24. 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

26. Lateral View Make a Plus sign Bermuda triangle Left atrium
Right atrium
Main pulmonary artery
Aortic Arch
Left atrium
Left Ventricle
Right Ventricle

27. 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

28. 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
Expiratory lateral views are utilized to examine a patient for tracheal collapse.
Tracheal hypoplasia is common in certain brachiocephalic breeds, such as the bulldog.

29. Lungs Normal anatomy 1 4 2 5 3 6 7 Left Right
Cranial (cranial subsegment) 1
Cranial (caudal subsegment) 2
Caudal 3
Right
Cranial 4
Middle 5
Caudal 6
Accessory 7 1 4 2 5 3 6 7

31. 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
Thymus is visible in young dogs.
Cranial = pre-cardiac
Middle = cardiac
Caudal = post-cardiac

32. Mediastinal Reflection
Caudoventral mediastinal reflection

33. Extrathoracic Structures
Sternum
Vertebrae
Ribs
Adjacent soft tissues
Diaphragm

34. Pectus excavatum: congenital sternal anomaly.

35. The Diaphragm Cupola Right and left crura
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

36. The Diaphragm
Right versus left lateral

38. The End