Thoracic Imaging: CT & VQ Flashcards
different types of CT scans?
radiation amounts?
normal CT: a bunch of individual x-ray images all put together to create a more detailed view by layer
HRCT: high resoultion: gives you are really good picture of whats on the “surface of the slice” good for systemic issues but doesnt give you a good idea about somethign which may be burried within slices
spiral CT: faster with less radition
CT: approx. 3.5 years of radiation (low additiona risk of fatal due to radiation)
indications for a chest CT
- follow-up for a chest x-ray
- suspected PE
- aortic dissection (suspected)
- trauma
- massess/nodules seen on xray
- staging cancer
- post-surgical eval.
- interstital lung disease
- “triple rule out” for AS, PE and aortic dissection
screening for lung cancer — low dose CT for those 50-80 with 20 pack year history or active smoker and quit in last 15
indications for using contrast in a CT? when to NOT use contrast?
contrast: used to evaluate anything vascular (or things which might have similar attenuation on imaging and need to be separated)
- PE
- mediastinal or hilar mass/adenopathy
- aortic aneurysum
- blunt or penitrating trauma
- cardaic CTA
not normally used for…
- diffuse lung injury
- chronic dyspnea
- pleural effusions
- pna
CONTRAINDICATED
- renal disease ( GFR < 30) prehydrate
- allergy can premed with steroids
- seafood allergy
what is seen at a CT at the aortic arch level
- aortic arch
- SVC
- azygous vein
what is seen on CT at the level of the Aorto-pulmonary window
- ascending aorta
- decending aorta
- SVC
- left pulmonary artery
seen at main pulmonary artery window CT
- main pulonary artery
- right pulmonary artery
- left pulmonary artery
- right main bronchus
- left main bronchus
seen on high cardiac level window CT
- left atrium
- right atriucm
- aortic root
- right ventricle
seen on low cardaic window on CT
- right atrium
- right ventricle
- left ventricle
- interventircular septum
what are the fissures of the lungs
- major fissures: in both lungs & able to be visualized
- minor fissure: in the right lung only and not always visualized
CT findings of COPD
- hyerinflated with flat diaphragm
- hyperlucency of the lungs (reduced lung markings)
- promience of the pulmonary arteries
Blebs: small < 1-2 cm subpleural air spaces with thin walls
- can ruputre (PTX) or combine (Bullae)
Bullae: > 2 cm
Cysts: gas filled (or uquid) with thin walls up to 4mm
cavities: THICK WALLS with varying size commong klebsella or TB (infections!)
what is bronchiectasis? findings on CT?
- irreversible dialation and damange to ariways in the lungs
signet ring sign : bonchus becomes larger than its associated pulmonary artery (big dark next to light)
tram-tracking : thickened walls and failure of the bonchi to taper off as it travels
when do you use a CT angiography ?
- PE suspected (with contrast)
- visualize the embolism and its bloackage (the block is darker and there is no light flow after the block)
when do you use a V/Q scan? what is it?
V/Q = ventilation perfusion scan
- done with suspected PE but the CT was inconclusive or the pt. has acute renal failure and the CT is unable to be performed
wells criteria 2-6 –> get d-dimer –> + d dimer get CT
perfusion (Q): tag a radiotracer RBC and wathces to see for obsturction
ventilation (V): follow-up done if perfusion is abnormal (inhale xeon-133) and check airflow distribution
how are V/Q ratios interpretated
- normal: no need for inhaltion scan
- negative or low probability: minor V/Q mismatch think lung disease
- postive or high probability: two ormore larger or moderate sized mismatches probably a PE
intermediate: has both fatures (doesnt tell you much)
catheter-base pulm. angiography
- old gold-standard for PE
- access the vein via femoral or brachial
- interpreted by looking at the LACK of flow to specific areas
will be used if there is high suspision for a PE but all ohter tests (V/Q) or CT arent showing
