Thoracic Radiograph Positioning & Technique Flashcards
How does peak inspiration and expiration compare on radiographs?
INSPIRATION - increased conspicuity of pulmonary lesions
EXPIRATION - increased cardiothoracic ratio (heart looks larger)
What is commonly seen on expiration on radiographs? What are 2 causes of false positives?
mild to moderate unsctructured interstitial pulmonary pattern can border efface other pulmonary abnormalities
- pulmonary edema
- cardiomegaly
How are the crura seen normally on radiographs? What is seen in small breeds? What is indicative of inspiration? Expiration?
only the crura will be seen, either cranially or caudally
cupula may stay in contact with the cardiac silhouette
- INSPIRATION = more caudal, T11-T12
- EXPIRATION = more cranial, T10
How do the two crura, space between cardiac sihouette and diaphragm, and cranial lung lobe compare on inspiration vs expiration?
CRURA = more separated during inspiration
HEART/DIAPHRAGM = larger space between cardiac silhouette, diaphragm, and caudal vena cava on expiration
CRANIAL LUNG LOBE = larger on inspiration
What are 3 differences in in the diaphragm in cats?
- crura and cupula move together
- crura located more caudally, T13-L1
- cupula at T9-T10 with separation from cardiac silhouette
What are the 4 characteristics of the right lateral projection?
- conspicuity of left-sided pulmonary lesions and better inflation of left lobes
- oval to egg-shaped cardiac silhouette
- diaphragmatic crura parallel to each other
- cranial lobar vessels and airways cross each other at the cranial aspect of the cardiac silhouette
What are the 4 characteristics of the left lateral projection?
- conspicuity of right-sided pulmonary lesions and better inflation of right lobes
- circular cardiac silhouette
- diaphragmatic crura diverge from each other as they extend dorsal from caval hiatus
- cranial lobar vessels and airways are parallel cranial to the cardiac silhouette
How does the cardiac silhouette compare on right and left lateral projections?
RIGHT = oval to egg-shaped
LEFT = circular shape
How do the crura compare on right and left lateral projections?
RIGHT = parallel to each other
LEFT = diverge from each other as they extend dorsal from caval hiatus, overlaps cardiac silhouette
How do the cranial lobar vessels/airways compare in right and left lateral projections?
RIGHT = cross each other at the cranial aspect of the cardiac silhouette
LEFT = parallel cranial to the cardiac silhouette
How are patients set up for ventrodorsal projections? What are the 2 most important things seen?
dorsal recumbency
- oval cardiac shape with apex to the left (levocardiac position)
- diaphragmatic crura and cupula seen separately
How are patients set up for dorsovantral projections? In what 3 ways does it compare to ventrodorsal projections?
ventral recumbency
- better conspicuity of lesions in the caudodorsal lung lobes —> caudal lobes better inflated
- more upright appearance of the cardiac silhouette (circular)
- separate crura NOT seen, just cupula (one diaphragmatic margin)
What is the purpose of the humanoid ventrodorsal projection in animals?
pulling thoracic limbs caudally rotates the scapula out of the way and no longer superimposes over the cranial lung lobes = conspicuity of cranial lung fields
Which of the following radiographs are a left lateral projection?
3 - follow caudal vena cava to right crura which is caudal, and crura diverge from one another
Which radiograph is inspiratory and expiratory?
TOP = expiratory, crura pushed cranially
BOTTOM = inspiration
What is the cranioventral mediastinal reflection? What are commonly found here?
where right cranial lung lobe extends from the right side of the thorax to the left and the left cranial lung lobe extends from the left side of the thorax to the right
- internal thoracic vessels
- sternal lymph nodes
What is the caudoventral mediastinal reflection? How is it seen on radiographs?
area where accessory lung lobe extends from the right sides to the left
VD - extends between cardiac apex and the left side of the cupula
What is the carina?
terminal caudal portion of the trachea located dorsal to the cardiac silhouette and just cranial to the principle bronchi or bifurcation of the terminal trachea
What is an extrapleural sign?
indentation into the pleural space caused by some structure outside of the parietal pleura
What is diaphragmatic tenting?
hyperinflation of the lungs causes a convexity in the diaphragm associated with its margins that represent attachments to rubs
- also seen in pneumothorax when pressure in the pleural space in elevated
What is a lazy heart appearance?
in aging cats, the cardiac silhouette angle with the stenum becomes decreased so that it appears to by lying on the sternum
What is a redundant aortic arch, or aortic knob?
in aging cats, changes occur within the tunica intima and media of the aortic arch, resulting in an angular appearance of the aorta or circular appearance on the VD/DV image
- responsible for shifting the silhouette, giving the lazy appearance
What is plate-like atelectasis?
linear, focal area of atelectasis along known minor or subpleural fissues of the right or left cranial lung lobes —> soft tissue appearance in cranial thorax
What is a lobar sign?
feature of an alveolar pulmonary pattern, where there is abnormal lung adjacent to the interlobar fissure and the adjacent lung lobe is normal
What is an interlobar fissure?
x-ray beam directed tangentially to the fissure between the right middle and right caudal lung lobes, resulting in a soft tissue opacity
- becomes larger and more opaque with effusions
