V/Q Scan Flashcards
two inter alveoli connections that allow for collateral air movement
- Pores of Kohn
- Canals of Lambert
___ are better ventilated than the ____.
bases of the lungs are better than the apices
blood flow is gravity dependent.
when someone is standing or sitting, there is ___ more perfusion at the bases than apices.
3-5x
indications for V/Q scans
- PE?
- assessing anticoagulant tx
- covid reso
patient prep
- CXR within 24hrs
- rehearsing the breathing procedure
contraindications for V/Q
- severe pulmonary HTN
when do we reduce particle numbers?
- pts with pneumonectomy or lobectomy
- peds
- R-L cardiac shunts
- pulmonary HTN
- pregnancy
RP - ventilation aerosol
133Xe
RP - ventilation gas
DTPA, MDP, SC
dose of RP aerosol injected into nebulizer
900-1300 MBq
ideal aerosol size
0.1 - 0.5 um
patient receives approximately ___% of the dose added to the nebulizer
2-5%
ventilation technegas RP
pert
dose of pert for the technegas machine
400-900 MBq, pt only receives 10%
ideal size for the aerosol from technegas
30-60 nm
dose and rp for perfusion part of the study
74-222 MBq MAA
ideal # of particles
200k-700k with 350k ideal
why are ventilation images usually done first?
to check for image quality - positioning, artifacts
views for Q scan
ANT/POST, RAO/LPO, LAO/RPO, LATs, SPECT
difference with acquiring if using technegas vs. Xe gas or DTPA aerosols
technegas - statics and SPECT
Xe - dynamic views of inspiration, eq., expiration
Xe133
inspiration image is done by…
having the pt take a deep breath and holding it for 10 secs
Xe133
equilibrium images are done by…
having pt breathe into the machine and obtaining 3, 30 sec images
Xe133
how are washout images acquired
turning off the Xe and having the patient breathe normally into the machine
how long are patients supposed to breathe the aerosol for?
3-7 mins or 1500-2000 cps
which phase of the technegas production actually produces the technegas?
burn phase
when injecting the patient for the Q, patients can be sitting or supine. it’s up the patient. t/f
false
patients must be supine
inject the patient for the q scan over _____ respiratory cycles
3-5
what ensures a good injection?
3x the count rate of vent
if a V/Q scan is needed for a pregnant pt, what should we do?
- reduce the number of particles
- do perfusion first, vent, if needed, can be done the next day
advantage of vent imaging done with xenon
washout images allow for good sensitivity in detecting ventilation pathologies
what is the flow rate of O2 administered through the nebulizer?
8-12LPM
ab in same location on both V and Q
matched
likely indicator for vent abnormalities
matched
Q abnormality, normal vent
mismatched
mismatched defects most likely indicate…
PE
normal Q, abnormal vent
reverse mismatch
modified PIOPED
HIGH (>85% PPV)
2 or more large mismatched segmental defects with normal CXR
large = >75% of segment
what will happen if you pull blood back into the MAA syringe?
it’ll cause hot spots on the images
quantum mottle
less than 60k particles injected
indication for quantitative lung scan
- eval relative lung perfusion preoperatively
what are the best views for a quant lung scan?
ANT/POST
normal % uptake for right lung? left lung?
right lung = 55%
left lung = 45%
expiratory reserve volume of ____ is high risk for pulmonary insufficiency post op
<800 ml
