Lung Vent Imaging (Aerosol) Flashcards
Describe the RPs involved in aerosol vent and the dose given.
RPs:
- Tc-99m DTPA
- Tc-99m MDP
- Tc-99m Cocktails
Dose:
- Amount of activity deposited depends on initial nebulizer concentration, length of breathing, and patient condition
-About 10% of initial dose is deposited into lungs, majority into nebulizer tubing (925-1110 MBq = 20-40 MBq in lungs)
Describe aerosol prep
-Liquid RP is diluted to 2-4 ml of saline and placed in nebulizer
-Particles formed by forcing air or O2 through a nebulizer @ 7-10 L/min
- 0.5-2 um in size
What are the distributions of the different droplet sizes?
1-3 um: Alveoli uptake, sedimentation
> um: Oropharynx, main stem bronchi
< 0.1um: Expired
What is the excretion and biological half-life of an aerosol?
Excretion: Tc-99m DTPA is broken down by lungs and absorbed. Cleared by GU system
Biological T 1/2: Membrane permeability
-Healthy non-smoker: 80 minutes (+/- 20 min)
-Healthy smoker: 24 minutes (+/- 9 min)
Patient prep?
None except for a CXR in the last 24 hrs
How do you administer aerosols?
-Pre or post perfusion
-Patient inhales during tidal breathing over several mins (nose clamps and mouthpiece, face mask)
-Supine/sitting
-Goals: 3-5 mins/2000cps
-100k-200k counts
Describe imaging procedure for aerosols
-LEAP collimator
-Patient sitting or semi supine, FOV centered over chest
-Acquire 250 000 cts per view
What are the disadvantages of aerosols?
-No wash-out phase
-Static views only
-aerated lung volume only
-10% of dose reaches lung
-activity artifacts
What are the advantages of aerosols?
-Pre or post perfusion
-multiple views; SPECT
-same views as perfusion
-start/stop breathing
-possible to image ventilator dependant patients
-portable
What are normal aerosol vent results?
-Uniform distribution throughout lung field
What are abnormal aerosol vent results?
-Patchy distribution
-Decreased uptake of areas of poor ventillation
What are some artifacts in aerosol vent?
-Mouth
-esophagus
-stomach
