28. Principles of interpretation - Thorax Flashcards
1
Q
What three factors contribute to atelectasis in lateral recumbency?
A
- weight of e.g. heart
- Reduced excursion of dependent thoracic wall
- Cranial excursion of dependent portion of diaphragm
2
Q
Which cranial lobar vessels are readily identifiied in lateral projections (which projection) and why?
A
- ONLY RIGHT CRANIAL LOBAR VESSELS PROPERLY VISIBLE-> best visualised in LEFT LATERAL view. In right lateral are dorsally displaced and superimposed on L lateral vessels
- Left cranial vessels usually cannot be seen as superimposed on mediastinum or on other vessels
3
Q
How does the heart differ between lateral projections?
A
- In LL: Slightly rounded and apex slightly elevated from sternum
4
Q
Why are the caudal lobar vessels better visualised in DV vs VD?
A
- Magnificaiton
- More parallel to plate
- Less atelectasis
5
Q
How does the cardiac silhouette differ between VD and DV projections?
A
- IN DV: ventral diaphragm pushed forward, contacting and displacing heart to left
- IN DV: Heart more round
6
Q
Which combination of rx settings is preferred in the thorax and WHY?
A
- High kVp; low mAs
- Long scale of contrast -> many grey shades. Important as inherent marked contrast provided by lungs