Pulmonary ventilation imaging

Lung ventilation imaging is the distribution of lung ventilation by inhalation of a 99m sputum-labeled aerosol or radioactive gas (eg, 81s 氪). Clinically used to understand the patency of the respiratory tract and the ventilation function of various lung diseases, can also be used to evaluate the local lung ventilation function before or after the drug or surgery, to guide the treatment and observation of the effect, often combined with lung perfusion imaging, for Diagnosis and differential diagnosis of pulmonary embolism and obstructive pulmonary disease. Basic Information Specialist Category: Respiratory Examination Category: Radionuclide Applicable gender: whether men and women apply fasting: fasting Tips: Pay attention to guiding the subject to breathe at normal speed and depth. Otherwise, excessively calm inhalation will result in the largest peripheral airway deposition, and rapid inhalation will cause more central airway deposition. Normal value Since ventilation imaging is a dynamic continuous process, the duration of each period is short, and generally only the PA position is used. The normal image of inhalation and balance period is that the radioactivity distribution of the two lungs is more uniform and symmetrical. The lungs in the inhalation period are slightly larger than the equilibrium period. The radioactivity in the lungs is significantly reduced at the first minute of the elution period. The image is not clear in the first two periods, and the third time is not clear. The lung shadow has basically disappeared, there is no radioactive deposition in the airway, and the radioactivity is close to the background. Clinical significance Abnormal results: 1. Pulmonary perfusion imaging is normal, and pulmonary embolism diagnosis can be excluded. 2. Lung ventilation imaging showed abnormality, or the damaged lung lobe and lung segment showed corresponding radioactive defects, suggesting that the airway was completely or incompletely obstructed. 3. If pulmonary ventilation imaging is normal, and pulmonary perfusion imaging is abnormal, suggesting pulmonary vascular obstructive diseases, such as pulmonary embolism, pulmonary vasculitis. 4. If the lung ventilation and perfusion imaging are abnormal, most of them are pulmonary parenchymal diseases caused by airway diseases, such as chronic obstructive pulmonary disease. Need to check the crowd: In patients with impaired lung lobe, pulmonary vascular obstructive disease requires a confirmed patient, a patient with pulmonary parenchymal disease. Precautions Preparation before inspection: Note that the subject is instructed to breathe at normal speed and depth. Otherwise, excessively calm inhalation will result in the largest peripheral airway deposition, and rapid inhalation will cause more central airway deposition. Requirements for inspection: 1. Pay attention to the radiation protection of patients and medical personnel and prevent environmental pollution. 2. Often checked with a lung perfusion scan. Inspection process 1. Radioactive inert gas ventilation imaging 1, imaging agent: commonly used 133Xe radioactive gas, gamma ray energy is 80keV, physical half-life is 5.2d. The total dose of radioactivity per test is not less than 370MBq. 127Xe and 81mKr radioactive gases can also be used. 2, imaging equipment conditions: 1133Xe Pulmonary Function Meter: Consisting of 133Xe inhalation and recovery, including mask or mouth tube, spirometer, 133Xe injection and discharge piping system, valve, 133Xe recovery adsorption unit. Make sure the instrument is not leaking 133Xe. 2 gamma camera or SPECT imaging device: The probe is equipped with a low energy high sensitivity or low energy universal collimator. The energy peak is 80keV and the window width is 20%. The probe should be as close as possible to the subject's body surface. 3. Operating procedures: 1 Preparation before imaging: Explain the inspection procedure to the subject, make it quiet, take the seat, back against the probe, and include the whole lung in the field of vision. Wear a breathing mask (if you use a mouth tube, you must clip your nose), turn on the spirometer, and naturally breathe the gas supplied by the ventilator to adapt it. 2 Single inhalation imaging: 嘱 The subject is deeply aspirated to the maximum capacity of the lungs, then exhaled to the residual volume. When deep inhalation is started again, 133Xe is quickly injected into the ventilator inlet. At the maximum lung capacity, hold the breath for 10 to 15 seconds, and simultaneously start the imaging acquisition of 1 image frame, the image matrix is ​​256 × 256 pixels, and the count is 300 ~ 500k. 3 Balanced period imaging: the subject turns into tidal breathing, the ventilator changes the air supply mode, so that the subject repeatedly inhales 133Xe mixed with air for 3 to 5 minutes, after the 133Xe balance in the lung and the ventilator ( According to the stability of the display count rate, the air is sucked up to the maximum capacity, and the image is captured for 1 frame. The image matrix and the count are the same as the single inhalation. 4 Respiratory gating imaging (selected if necessary): Apply respiratory rhythm, trigger respiratory gating generator, and simultaneously acquire images of different periods of each respiratory cycle. Generally, each breathing cycle is divided into 8 to 12 frames, and the image matrix is ​​128×128 pixels. The number of collection cycles is determined by the image quality and several breath cycle images are superimposed. 5 Clear the imaging: change the ventilator control valve, the intake pipe only inhales the indoor fresh air, exhales the gas containing 133Xe, and adsorbs through the 133Xe recovery device. Start dynamic image acquisition, image matrix 128 × 128 pixels, 5 ~ 10s / frame, acquisition time 5 ~ 10min. Delayed removal imaging can be performed after 10 minutes if necessary. 2. Radioactive aerosol ventilation imaging 1. Imaging agent: The commonly used radioactive aerosol is 99mTc-DTPA solution, and similar radiopharmaceutical solutions (such as 99mTc-EHIDA, etc.) can also be used. The aerosol atomizer is used to atomize particles having a diameter of <10 μm (3 to 10 μm particles are deposited in the thin branch tube, and 1 to 3 μm particles can reach the alveoli), and the inhaled aerosol particles are deposited in the lungs by 5% to 10%. Those with conditions can also use 99mTc gas (technegas) for lung ventilation imaging. Because the particles are small and more uniform, the central airway deposition is less, the lung tissue imaging quality is better, and the imaging method is basically the same as the former. 2, imaging equipment conditions: 1 Aerosol atomizer: Connect the nozzles of the atomizer and medical oxygen to make it work. 2 gamma camera or SPECT: The probe is equipped with a low energy universal collimator with an energy of 140 keV and a window width of 20%. The image matrix is ​​the same as the perfusion imaging condition, and a 500k/frame count is acquired. 3. Operating procedures: 1 Preparation before imaging: Explain the inspection procedure to the subject, use the mouth to bite the mouth tube, use the nose clip, and test the oxygen to make it suitable for this kind of breathing. 2 radioactive aerosol inhalation: 740 ~ 1480MBq (20 ~ 40mCi) 99mTc-DTPA solution, the volume of 2 ~ 4ml, into the atomizer, control the gas flow rate of 8 ~ 10L / min, fully atomized, after filtration, An aerosol of a suitable size for the mist is produced. 嘱 The subject inhaled aerosol aerosol as much as possible, and the inhalation time is 5-8 minutes. 3 Image acquisition: The subject takes the lying position, and collects 4 frames of images of the front, back, left, and right sides or increases the front and back oblique positions by 6 to 8 frames. Not suitable for the crowd Patients with cardiovascular disease need to consult a doctor before the examination. Adverse reactions and risks May cause difficulty breathing.