Introduction To Thoracic (Cardiac & Respiratory) Imaging Flashcards
What is the commonest modality used to image the thorax? Why?
CXR
Can see lung + cardiac pathology
Useful quick primary screen that is relatively cheap
What other modality’s can be used to image the thorax? Why?
CT: see multiple thoracic structures
CTPA: pulmonary angiography e.g. in embolism
US: pleural pathology
Why would you not use MRI as a first choice to image the thorax?
Expensive, takes time + is unpleasant for patients
What is MRI used mainly for in terms of imaging the thorax?
Cardiac investigation
How do X-rays work?
X-ray generator produces X-ray beams which come out of point source projector + spread out going through the patient + into the detector/film
How directions can thorax X-rays be done in? How do you achieve this?
PA: X-ray source anterior to patient, detector posterior
AP: X-ray source posterior to patient, detector anterior
What direction are most thoracic films taken in? Why?
PA
Want the heart to appear life size so it must be as near to detector as possible
How should thoracic images be read in a systematic way?
- Demographics (ID, DOB + name)
- RIP (rotation, inspiration + penetration)
- ADCDE (airway, breathing, cardiac, diaphragm + everything else)
How can you assess the rotation of a patient on an X-ray?
Sternal head of clavicle + spinous processes in midline of vertebrae (tear drops) - see if spinous processes equidistant from collar bone joint + if so, the patient is head on
How can you assess the inspiration of a patient on an X-ray?
You want to be able to see ribs 5-7 anteriorly
Start counting from the 2 dark ovals at the lung apex (rib 1) + follow their curvature
How can you assess the penetration of an X-ray?
You want to be able to see the vertebral column outline + invertebral discs behind the heart
What will the trachea look like on an X-ray?
Midline (should be lined up with spinous processes) mostly below the clavicle
Appears dark as air is in it whilst surrounding tissue is white due to sot tissue, fat + blood etc.
Should be able to trace it down to R + L bronchus at rib 2 where it bifurcates
What should the diaphragm look like on an X-ray?
Dome shaped on both sides
Why do the back of the ribs on an X-ray appear whiter than the front?
Because the front is cartilage
What is penetration?
How well the X-ray has been absorbed by the structures i.e. how well you can visualize them
Why should you not rely on the heart as a marker for the direction the patient is facing?
In conditions such as dextrocardio, the heart is on the right, so this will confuse the image
What in the airways do you want to mainly look at on X-ray?
Tracheal position
What do you want to look for in a X-ray in terms of breathing + cardiac structures?
Breathing: hilum + lung fields
Cardiac: cardiothoracic ratio
What should the hilum of the lung look like on X-ray?
Hilar point is V-shaped where bronchi start to divide
Appears whiter than surrounding lung tissue as its denser due to vessels + bronchi
If the lung hilum is not visible due to a larger white structure in the way, what may this be? Why might a patient have this?
Mediastinal lymphadenopathy
Tumour may have metastasized to the lymph nodes in the mediastinum
If a patient has mediastinal lymphadenopathy, what clinical picture may they present with?
Dysphagia Stridor in breathing (due to tracheal compression) Hoarse voice (due to RLN compression)
What should normal lung fields look like on an X-ray?
White lines should project to edge of thoracic cage meeting outer perimeter due to blood supply + tracheobronchial tree
What are the 4 different zones examined on X-ray of the lungs?
- Apical: above clavicle
- Upper: below clavicle + above lung hilum/cardiac shadow
- Middle: level with lung hilum
- Lower: below hilum + including costodiaphragmatic recess
What should the costodiaphragmatic recess look like on X-ray?
V-shaped black groove in lower zone of lungs
