Nukes pulmonary Flashcards
definition of ventilation defect sizes (as a fraction of segment)
small < 25% < moderate < 75% < LARGE
if you have two moderate defects, what does this equal?
2 moderate defects = 1 large defect. smalls do not add up
if your perfusion scan is normal, do you need to do the ventilation portion?
no. you have excluded a PE.
a triple match in the lower lobe:
intermediate probability
triple match in the upper lobe
low probability
high likelihood ratio # defects
>/- large V:Q mismatched segmental defects
high likelihood ratio number
17
effective dose of CTPA
21 mSv
fetus absorbed dose
<1 mGy
effect dose of perfusion scan only
1 mSv
effect dose of V/Q scan
1.3 mSv
Fetus absorbed does from a V?Q scan
0.4
fetus absorbed dose from perfusion scan only
0.25
breast absorbed dose CTPA
44 mGy
breast absorbed dose for V/Q scan
<1 mGy
which has a higher breast absorbed dose, CTPA or V/Q?
CTPA!!! CTPA is 44m Gy and V/Q scan is < 1mGy for breast absorbed dose
pt with AIDS
PCP pneumonia
PCP is gallium hot, thallium cold
Pt with HIV
kaposi sarcoma
Tl-201 scan (can see the heart) with uptake in the lungs
HIV patient with thallium and gallium avid lesions
lymphoma
the only one hot on both thallium and gallium
Kaposi thallium and gallium uptake
Kaposi is thallium hot and gallium cold
PCP thallium and gallium uptake
PCP is thallium cold and gallium hot
entities that cause V/Q mismatch
Vacular
- PE
- pulmonary artery atresia (unilateral lung out)
- vasculitis (multiple small defects)
Space occupying
- plueral effusion
- tumor
Scarring
- fibrosing mediastinitis
- radiation therapy
ddx for decreased perfusion to one lung
Vascular
- Massive PE
- pulmonary agenesis
- Swyer-James (vascular pruning once bronchiolitis obliterans has been around long enough)
Massively space occupying
- Huge pneumothorax
- Massive effusion
- Mediastinal fibrosis
- tumor
Metter pearl
a stable preggo patient gets a V/Q scan and the team tells you that they had a radiograph 2 days ago. Is this okay?
YES!!!
a radiograph 1-2 days old is okay for a stable patient
Metter pearl
an inpatient who is crumping gets a V/Q scan and the team tells you that they had a radiograph 2 days ago. Is this okay?
NO!!!
a NEW radiograph is required for an unstable patient
Metter pearl
can you interpret a V/Q scan without a chest radiograph?
NO!!!
a radiograph within 1-2 days may be okay for a stable patient
a NEW radiograph is required for an unstable patient
does a normal perfusion scan exclude pulmonary embolism?
abso-fucking-lutely (yes it does exclude a PE)
how do you differentiate between segmental pefusion defects caused by airway problems (COPD, asthma, mucus plug) compared with PEs?
Airway problems will cause segmental perfusion defects, but they will have an ABNORMAL ventilation scan
PEs will have a NORMAL ventilation scan
Mettler pearl
infiltrate on CXR > perfusion defect to same segment
pneumonia
versus a PE where the infiltrate < perfusion defect
infiltrate on CXR < perfusion defect
PE.
as opposed to pneumonia where infiltrate > perfusion defect
focal hot spot in the lung
due to an injected labeled clot that was dislodged from the end of a central line through where Tc-99m MAA was injected
(or just injected labeled clot from pulling blood back into your syringe)
differential for patchy defects on perfusion scan
fat emboli
tumor emboli **
vasculitis
inadequate number of particle injected
**(lymphangitis carcinomatosis pattern referred to as contour mapping)
Mettler pearl
collection of activity in the central bronchi on ventilation scan
COPD
Mettler pearl
normal finding in lung transplants
poor perfusion to the lung apices
when can you see esophageal activity in a ventilation scan
only in DTPA scan when it is swallowed instead of inhaled
