Chest Imaging Flashcards
what are the different densities on CXR
air- black fat- grey soft tissue/ muscle- grey/ white bone- white metal - bright white
is the cardiothoracic ratio (CTR) measure on a PA or AP CXR
PA (not done on AP as makes heart look bigger)
what is the CTR
ratio of maximal horizontal cardiac diameter to maximal horizontal thoracic diameter
what is a normal CTR
less than 0.5 (heart half of thoracic width)
how many ribs should be present on CXR when fully inspired
the anterior ends of at least 6 ribs should be visible
how do you know a CXR is correctly centred
the medial ends of the clavicles should be equidistant form the spinous processes of the upper thoracic vertebrae
what are the mediastinal borders
aorta pulmonary artery left auricle left ventricle right atrium trachea hemidiaphragm stomach bubble horizontal fissure
what are the pulmonary hila
junctions between the heart and the lungs
where pulmonary arteries and bronchi enter and the pulmonary veins exit the lungs
which hilum is higher
the left
what is the dominant structure in the hilum
pulmonary artery
which diaphragm is higher
right side 1.5cm higher than left
what are the zones of the lung
each has upper (to 2nd rib), middle (2nd to 5th rib) and lower- not the same as lobes
which lung has only two lobes
left- although has lingula
how do you tell the anterior from posterior part of ribs
anterior curved, posterior straight (horizontal)
what pathologies occur in the lung apices
masses (pancoast tumour), pneumothorax
what pathologies occur behind the heart
consolidation, masses, hiatus hernia
what pathologies occur below the diaphragm
free gas, misplaced lines and tubes, gastric distention, bowel obstruction
what in the bones and soft tissues is often misses on CXR
fractures, masses, mastectomy, subcutaneous emphysema, evidence of previous surgery
what are the review areas on CXR
common areas for missed findings- lung apices, behind heart, below the diaphragm, bones and soft tissues
what causes lobar collapse
obstruction of a lobar bronchus (tumours, foodstuffs, mucus impaction)
lobe no longer ventilated, air gets resorbed, volume loss, collapses
what does a collapsed lobe look like on CXR
density increases
adjacent major fissure dragged out of position
what does a left lower lobe collapse look like on CXR
volume loss on left, elevation of the hemidiaphragm
increased density in left retrocardiac region (white sail sign)
loss of clarity in medial aspect of left hemidiaphragm
left hilum displaced downwards
left hemithorax looks smaller
what does a left upper lobe collapse look like on CXR
volume loss on the left, elevation of the left hemidiaphragm
loss of clarity of heart shadow
veil like diffuse opacification of the left hemithorax
what does a right upper lobe collapse look like on CXR
volume loss on the right
loss of clarity of the upper right mediastinum
density in the right upper zone
elevation of the horizontal fissure
what does a right middle lobe collapse look like on CXR
loss of clarity of the right heart border
density in the right lower zone
right hemidiaphragm PRESERVED
(small lobe)
what does a right lower lobe collapse look like on CXR
volume loss on the right loss of clarity of the right hemidiaphragm density in right lower zone depression of the horizontal fissure (can still see right heart border)
what does the bronchus intermedius mean for lobar collapse
is the common origin for bronchus to both the middle and lower right lobes, if obstructed both will collapse
what does a combined right middle and lower lobe collapse look like on CXR
volume loss on the right
loss of clarity of the right hemidiaphragm and right heart border
density in right lower zone
depression of the horizontal fissure and oblique fissue
what pattern does consolidation follow
same positions and obscuring same borders as lobar collapse but without the volume loss
what is the lingula adjacent to
the left heart border
what does right middle lobe consolidation look like
increased density in tight lower zone
loss of clarity of the right heart border
right hemidiaphragm preserved
what does consolidation of the lingula look like
obscures the left heart border
left hemidiaphragm preserved
what does left upper lobe consolidation look like
increased density in left upper zone
loss of clarity of the left upper mediastinum
volume preserved
air bronchograms
what is an air bronchogram
where the bronchus contains air but the surround lung doesnt- is filled with blood/ pus/ etc
air filled bronchi running through fluid filled alveoli
when can you see the pleural cavity on CXR
only when it is filled with air (pneumothorax) or fluid (pleural effusion)
what does fluid in the pleural space look like
collects at lung bases
forms curved appearance of a meniscus at the lung edges
blunts the costophrenic angles
what causes a pneumothorax
rupture of the visceral pleura
what do pneumothoraxes look like on CXR
small- dark cresent without lung markings bounded medially by the lung edge, often at epex
larger- will have larger black air space with no lung markings
normally lung markings go all the way to the edge of the thorax
what does a tension pneumothorax look lik
displaced mediastinum
large air space in thorax with no lung markings
depressed hemidiaphragm
collapse lung (squashed by the air, unable to be ventilated)
what results from heart failure in the lungs
pulmonary oedema
what are the radio-logical signs of pulmonary oedema due to heart failure in order of occurrence/ severity
- dilation of upper lobe vessels/ cardiomegaly
- interstitial opacities (peribronchovascular cuffing (doughnut sign, haziness around bronchioles) and septal line (kerly B lines- peripheral lines usually at lung bases)
- airspace opacification (alveoli fill with fluid, when severe and acute has a perihilar/ batwing appearance, air bronchograms)
- pleural effusion
what is the mnemonic for the x rays signs of heart failure
ABCDE A- alveolar oedema (bat wing opacities) B- kerly B lines C- cardiomegaly D- dilated upper lobe vessels E- pleural effusion
what is the correct placement for an endotracheal tube
tip 5 cm above the carina
width 2/3rds trachea diameter
cuff should not expand the trachea
when is an endotracheal tube malpositioned
if extends beyond carina - commonly goes into right main bronchus (more vertical than left) (causes early collapse of unventilated lung)
may have entered oesophagus
what is the correct position of an nasogastric tube
subdiaphragmatic
in stomach (overlying gastric bubble on CXR)
at least 10 cm from gastro-oesophageal junction
passes carina in the midline
how might an NG tube be misplaced
tip remaining in oesophagus
in bronchus or lung
coiled in upper airway
intracranial insertion (skull base trauma/ surgery)
where are central venous lines inserted
right and left internal jugular/ subclavian veins
where are peripherally inserted central catheters inserted
cephalic, basilic or brachial veins
where should the tip of a central venous catheter be
at the cavoatrial function- right side
bend in line should be at 2nd anterior intercostal space
how can a central venous catheter be misplaced and what might this cause
tip too high- proximal SVC- risk of thrombus formation
tip too low- distal right atrium/ right ventricle- increased risk of arrhythmia
coiled or displaced in another vein
where should a peripherally inserted central catheter go
up arm towards axilla
under clavicle
towards heart
tip ends at cavoatrial junction/ in central vein
how might a peripherally inserted central catheter be misplaced
tip too high:superficial upper limb vein
tip too low:distal right atrium or right ventricle
tip in the right internal jugular vein
tip in the azygos vein
what are the different types of sizes of pulmonary masses
miliary nodules: <2 mm
pulmonary micronodule: 2-7 mm
pulmonary nodule: 7-30 mm
pulmonary mass: >30 mm
what are the morphologies of pulmonary nodules
solid pulmonary nodules
- calcified pulmonary nodules
partly solid pulmonary nodules
ground glass pulmonary nodules
what are the possible distribution of pulmonary nofules
perilymphatic pulmonary nodules
- perifissural pulmonary nodules
centrilobular pulmonary nodules
random pulmonary nodules
what does a basal predominance of pulmonary modules suggest
cancer- mets
does calcification of nodules suggest cancer
no
where in lung do primary lung cancers tend to be
apical- smoker
what does TNM stand for in lung cancer staginf
tumour size
intrathoracic lymph Node staging
metastases
what does a contrast enhanced CT do in lung cancer
assess tumour size
shows mets
guides biopsy of peripheral lesions
what does a FDG-PET CT do in lung cancer
shows nodal mets distant mets (not brain) delineated tumour in an area of collapse
what is a pneumoperitoneum
when perforation of a hollow viscous (stomach, duodenum, small/ large bower) causes gas in the peritoneal cavity
what is seen on CXE in penumoperitoneum
when patient in erect position
gas rise up under the diaphragm - think black line between diaphragm and subdiaphragmatic structures
(easier to see on right)
what is the presentation of a PE
dyspnoea either at rest or on exertion
pleuritic chest pain, cough, orthopnoea and haemoptysis
if caused by deep vein thrombosis,calf/thigh pain and swelling may occur
what Ix for a PE
D-dimers can be useful in low-risk patients to rule out a VTE
Chest radiographs are often performed to look for alternative causes for symptoms and to decide on appropriateness of V/Q scan (only if CXR normal)
CTAP to visualise the clot
V/Q scan (ventilation perfusion scan) to look for mismatched perfusion defect caused by clot
what might be seen on CXR in PE
non specific findings- plerual effusion, cardiomegaly, atelectasis (collapse of lung due to reduced/ absent gas exchange)
how do you tell CXR is PA not AP
scapular will not be over the film
how can you tell a CXR has good exposure
(enough radiation)
can see spine behind heart, left hemidiaphragm is visible to the spine
what is a silhouette sign
loss of a silhoutte e,g loss of heart borders
if you can see all the heart borders where must a lesion be on the left side
lower lobe
is blood white on CT
no- unless clotted
if blood white on CT then will have had contrast/ be clotted
what is white on CT
bones and metal
what is black on CT
air
what is seen in lung on CT in COPD
emphysema- seen as black holes: smokers in apices, alpha def in bases
what lymph nodes should be check in lung cancer
tracheobronchial- bronchopulmonary- supraclavicular
