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Lung Vent

PROCEDURE: LUNG VENTILATION SCAN
SECTION: PULMONARY 8.2
ORIGINAL DATE: 12–29–99
DATE REVISED: 9–22–16
REVIEWED: Annual

Indications

  • Diagnosis of pulmonary embolism.
  • Evaluation of ventilation.

Examination Time

  • 45 minutes

Patient Preparation

  • The aerosol ventilation study is usually performed after the perfusion study. This allows the aerosol study to be omitted when the perfusion study is normal. (However, the aerosol study may be performed before the perfusion study.)
  • Rehearse the breathing procedure to assure optimal patient cooperation; instruct the patient to breathe by mouth only.
  • Patient must have a chest X‑ray within 24 hours of the scan.
  • Imaging should be done in the same position (upright or supine) as perfusion imaging.

Equipment & Energy Windows

  • Gamma camera: Large field of view.
  • Collimator: Low energy, High Resolution, parallel hole. (LEHR)
  • Energy window: 20% window centered at 140 keV.

Radiopharmaceutical, Dose, & Technique of Administration

  • Radiopharmaceutical: Tc‑99m‑DTPA aerosol in 3 - 4 mls.
  • Dose:
    • Adult: 80-100 mCi ‑ if the aerosol study is performed second (approximately 6 mCi to the patient). 
    • Pediatric: 1.5 mCi/kg (Dosing Range 20-100 mCi)
    • Adult 40-60 mCi ‑ if the aerosol study is performed first (approximately 1 mCi to the patient).
    • Pediatric: 0.6 mCi/kg (Dosing Range 10-50 mCi)
  • Technique of administration: Via a positive pressure nebulizer: 
    1. Patient education is very important. Carefully explain exactly what will be happening during ventilation to the patient.
      • Note: Explain numbers 2 through 4 to the patient prior to beginning procedure.
    2. Place the mouthpiece in the patient's mouth.
    3. Place the nose clip on the patient's nose.
    4. Turn on the oxygen, instruct the patient to take normal breaths from the system.
    5. Add 99mTc DTPA to nebulizer. 
    6. Gradually turn on the oxygen to the desired flow rate, 10‑12 L/min. (An abrupt increase may cause detachment of the airline from the unit.)
    7. The patient should breath normally until the desired amount of radioactivity is delivered to the lungs. Be prepared to shut off the oxygen flow immediately if the patient releases the mouthpiece.
      • The patient breathes for 10‑12 minutes ‑ when the aerosol study is performed second.
      • The patient breathes for 3 - 5 minutes ‑ when the aerosol study is performed first. 
    8. After inhalation, turn off the oxygen and instruct the patient to continue breathing through the mouthpiece for an additional four or five tidal breaths to clear the system of aerosol.
    9. Remove the nose clip and mouthpiece from the patient. Have patient expel any saliva into disposable towel to minimize gastric radioactivity. If patient is coughing excessively after finishing with nebulizer, a mask (non-sterile, procedure) may be used to contain any possible Tc-DTPA contamination. If there is any question of contamination during or following the ventilation process please refer to 'NM Spill Policy 1.59' for guidance.
    10. The patient imaging procedure may be started as soon as convenient.

Patient Position & Imaging Field

  • Patient position: Supine (Sitting if the patient is unable to lie down).
  • Imaging field: Entire lungs.

Acquisition Protocol: Acquire analog images in the POST, LPO, L LAT, LAO, ANT, RAO, R LAT, and RPO projections:

  • If the aerosol study is performed second, start by measuring the count rate from the perfusion image in the POST projection. Then monitor the count rate as the patient inhales the aerosol and continue until the count rate equals 3‑4 times the base count rate . Acquire the aerosol ventilation images for the same times as the corresponding perfusion images.
  • If the aerosol study is performed first, acquire each image for approximately 500 K counts.

Data Processing: Screen cap images are created along with the Perfusion images, see Perfusion protocol for details.

SPECT ACQUISITION & PROCESSING PARAMETERS

Lung Ventilation

Time interval between tracer injection and imaging: Immediate

Camera/Collimator: LEHR

Patient position: Supine

Energy: 140 kev

Matrix: 128 X 128

Pixel size: 1.1 mm

Number of projections: 60 6 deg/view 30 / Head

Orbit CW or CCW: CW or CCW

Orbit type: Body Contour Circular

Start Angle: 0 deg

End Angle: 360 deg from start

Time per view: 15 sec/view

Gating (Y/N): N

Gating frames: Na

R to R window: Na

Uniformity and COR: Daily / Weekly

Prefilter Type: Hanning

Filter cutoff/power: 0.9

Motion correction: No – Repeat if motion

Attenuation correction Y/N: Y    CT

Normal database used Y/N: Y    Use MI Evolution for Bone

Reconstruction filter: OSEM

Screen caps to make: Plannar statics

Send to FUJI: Screen caps, CT, MIP, Trans Emission, Trans Fused

Send to Dr. PET: Full Study

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