Why patient should do the examination? (value of test).
Evaluation of the airflow (ventilation) and blood flow (perfusion) in the lungs; Diagnosis of the probability of pulmonary embolism (low, intermediate or high). Assessment of regional lung function. provide preoperative estimates of lung function in lung cancer patients, where pneumonectomy is planned. Quantifying right to left shunts and differential pulmonary blood flow. The V/Q scan is particularly beneficial in some circumstances where radiocontrast given in CTPA would be inappropriate, as in allergy to contrast agent, pregnancy or kidney failure.
Who benefits from getting tested?
Patients with clinical suspicion of: Acute pulmonary embolism with or without comorbidities such as COPD, left heart failure, pneumonia, and tumors.Chronic thromboembolic pulmonary hypertension.Right to left cardiac shunts. As pre-operative preparation for patients with operable lung neoplasm. As well as Pre-operative evaluation and post-operative monitoring in lung transplant patients.
Are there any contraindications to the examination?
Patients with mechanically/magnetically activated devices as cardiac pacemaker, cochlear implants.Patients with metallic foreign body in the eye.Pregnant women in the first trimester (benefits versus risk to be assessed).Ferromagnetic surgical clips or prosthesis.
What other tests should be done with this examination?
Complementary CT scan or X-ray of the chest is acquired within 24 hours of the V/Q scan. Other investigations done prior to the scan should be delivered by the patient for review by the nuclear medicine physician before the scan including radiological modalities (e.g. echocardiography, CTPA, lower limb Doppler..) as well as Laboratory tests (e.g. D-dimer level..)
Examination preparations
No specific preparations needed.
A brief description of the examination procedure
On arrival, the patient’s medical history is taken, The procedure is usually done on 2 separate days, The standard planar examination consists of 8 ventilation views and 8 perfusion views (anterior, posterior, both lateral, both anterior oblique, and both posterior oblique). V/Q SPECT images are also acquired in both studies. Scanning time takes about 45 minutes in each study. Perfusion lung scan: An IV cannula is inserted, the patient lies in supine position in front of the gamma camera, 185 MBq of 99mTc-MAA (10-100 Um particle size) is injected. In cases of pregnancy, a reduced administered activity of 18.5–37 MBq of 99mTc-MAA. Afterwards, lung imaging is performed. Ventilation lung scan: 1100 MBq of 99mTc-DTPA in the form of aerosolized liquid droplets is delivered to the patient via a nebulizer, the patient then lies in supine position in front of the gamma camera and lung imaging is performed. perfusion lung scan is done alone without ventilation if the patient was unable to perform ventilation technique for any reason, in cases presenting for differential quantification or for detection of right to left shunts, the latter requires additional spot views of the brain and kidneys.
Where I can get tested?
Are there any aftercare or precautions to be done?
Patients should stay away from children (less than 12 years of age) and pregnant ladies, for at least 24 hours starting after administration of the radiotracer.