Chest Imaging Flashcards
How do different structures appear on x-ray?
Air = black Soft tissue = grey/white Fat = grey Bone = white Metal = bright white
What type of x-ray view is used to measure the cardiothoracic ratio?
PA CXR = shouldn’t use AP CXR because it makes the heart seem artificially large
What is the cardiothoracic ratio?
The ration of the maximal horizontal cardiac diameter to the maximal horizontal thoracic diameter = normal is <0.5
What should be visible if a CXR is suitably inspired?
The anterior ends of at least 6 ribs
What should be visible if a CXR is correctly centred?
Medial ends of the clavicles should be equidistant from spinous processes of the upper thoracic vertebrae
What is the position of the left lung hilum in relation to the right lung hilum?
The left hilum is usually higher than the right
What is the position of the right diaphragm on a normal CXR?
Right diaphragm lies about 1.5cm above the left diaphragm
What are review areas?
Common areas for missed findings = lung apices, behind heart, below diaphragm, bones and soft tissue
What causes lobar collapse?
Happens when there is obstruction of the lobar bronchus = caused by tumours, mucus impaction or aspirated foodstuffs
What does lobar collapse cause on a CXR?
Causes adjacent major fissure to be displaced, with increased density and loss of clarity
What does infection of the lingular segments of the left upper lobe cause on CXR?
Obscures left heart border
What does pleural effusion cause on a CXR?
Blunting of the costophrenic angles
How does a small pneumothorax appear on a CXR?
Dark crescents without lung markings bounded medially by lung edge
What are the radiological signs of pulmonary oedema?
Dilatation of upper lobe vessels/cardiomegaly
Interstitial opacities = peribronchovascular cuffing
Airspace opacification = perihilar if severe, air bronchograms
Pleural effusions
What causes air bronchograms?
Air filled bronchi running through fluid filled alveoli
What are the features of heart failure on a CXR?
Alveolar oedema = bat wing opacities
Kerley B lines and cardiomegaly
Dilated upper lobe vessels and pleural effusion
What is the correct placement for an endotracheal tube?
Tip 5cm above carina
Width 2/3 of tracheal diameter
Cuff shouldn’t expand trachea
What are some examples of endotracheal tube malposition?
Tip may extend past carina
Tip most commonly seen in right main bronchus
May have entered oesophagus
What is the correct placement for a nasogastric tube?
Subdiaphragmatic position in stomach
At least 10cm beyond gastro-oesophageal junction
What are some examples of nasogastric tube tip malposition?
Remaining in oesophagus
Traversing either bronchus or more distally into lung
Coiled in upper airway or intracranial insertion
Where are central venous catheters inserted via?
Internal jugular or subclavian veins
Where should the tip of red, blue and purple venous catheters be positioned?
Tip should be at cavoatrial junction
What are some examples of red, blue and purple venous catheter line malpositions?
Tip in proximal SVC = increased thrombus risk
Tip in distal right atrium/ventricle = increased arrhythmia
Coiled or displaced in another vein
Where should the tip of yellow venous lines be positioned?
At cavoatrial junction or subclavian vein
What are some examples of malposition of yellow venous line tip?
Superficial upper limb vein or azygous vein
Distal right atrium/ventricle
Right internal jugular vein
What are the different sizes of pulmonary nodules and masses?
Miliary nodule = <2mm
Pulmonary micronodule = 2-7mm
Pulmonary nodule = 7-30mm
Pulmonary mass = >30mm
What are the different morphologies of pulmonary nodules?
Solid (calcified), partly solid or ground glass
What are the distributions of pulmonary nodules?
Perilymphatic (perifissural), centrilobular or random
How is contrast CT used to assess lung cancer?
Assesses tumour size, shows metastases and can guide biopsy of peripheral lesions
What does FDG-PET CT visualise in lung cancer?
Nodal metastases and distal metastases (not brain)
Delineating tumour in area of collapse
What is pneumoperitoneum?
Gas in the peritoneal cavity = radiograph taken with patient in erect position
How does pneumoperitoneum appear on CXR?
Thin black line between diaphragm and subdiaphragmatic structures = easier to see on right
What does a CXR of a pulmonary embolism show?
Usually normal or shows non-specific findings like cardiomegaly
What are some investigations used for pulmonary embolisms?
CT pulmonary angiogram = used to look for clot
V/Q scan = looks for defects caused by clot
