thoracic imaging Flashcards
what is the leading cause of mortality and morbidity?
respiratory diseases
pulmonary lung function tests: what kind of info, name a few tests
only global info about the lung, not which part of the lung has a problem
- spirometry
- N2-multibreath washout
- bodyplethysmography
what are the goldstandard imaging modalities for the diagnostic of pulmonary diseases? adv. and disadv. of the second one?
x-ray and CT
CT:
- rapid acquisition
- high spatial resolution
- contrast agent can be used
- but: exposure to radiation (children are at greater risk)
What is CT/SPECT for?
uses radioactive tracers and gives info about perfusion and ventilation
How does PET work and what is it mainly used for?
intravenous application of radioactive tracer -> will be absorbed in regions with high consumption of sugars -> used to find tumors / metastases
Which radiation free technique can we use to image lungs?
MRI
what are the 4 main challenges in lung MRI? (what can help)
1) lung tissue has a very low density (which depends on respiratory phase) -> hard to image
2) scan time must be very long to compensate for low SNR (increasing the resolution helps)
3) rapid signal decay in inhomogeneous tissues -> use weaker magnetic fields
4) MRI is slow, so breathing motion / heart beating has to be taken into account -> ECG gating, pulse gating, respiratory belt, retrospective gating, …
give examples of technological improvements in MR
- array coils (parallel imaging)
- gating and navigator techniques
- high quality magnets
- ultra-fast pulse sequences
- novel image reconstruction techniques
describe a MRI examination (set-up, time, …)
- supine position
- chest and spine receiver coils
- acquisition in breath-hold (not with kids) or free-breathing
- 20 to 45 minutes (if contrast agent for example)
what are two absolute and 3 relative contraindications for MRI?
absolute:
- heart pace maker or defibrillator
- coils (for aneurysm)
relative:
- metalic fragments
- op-clips
- ventricular shunts
give 3 examples of diseases to image without contrast agent and with contrast agent. Which caracteristic makes some things easier to visualize than others?
without:
- pneumonia
- cystic fibrosis
- tuberculosis
with:
- lung tumors
- pleural tumors
- pulmonary embolism
High proton density = stronger signal
2 techniques to make the lung more visible on MRI
1) ultra short echo (UTE)
2) balanced steady state free precession (bSSFP)
how does the resolution of bSSFP compare to CT? what about with a balanced SSFP (bSTAR) ?
CT is at sub 0.5 mm^3 resolution.
bSSFP: 2.5 mm^3
bSTAR scans data in a radial way (not linear) -> they were able to reachthe sub-millimeter resolution (0.9)
name 2 main groups of functional MRI methods
1) X-nuclei MRI:
- hyperpolarized 3He, 129Xe
- fluorine
2) 1H MRI:
- dynamic contrast-enhanced
- oxygen enhanced (takes too long)
- contrast agent free -> Fourier decomposition (suited for kids)
briefly explain how hyperpolarized gas MRI works
hyperpolarized means to force a lot of spins in the low energy state -> much stronger signal
