Pulmonary Scintigraphy: Treatment, Effects & Risks

One of the most important imaging procedures for lung examination is pulmonary scintigraphy. It is the standard procedure especially in the diagnosis of pulmonary embolism.

What is pulmonary scintigraphy?

Pulmonary scintigraphy is used for various lung diseases and malformations in addition to the diagnosis of pulmonary embolism. Pulmonary scintigraphy is one of the noninvasive procedures and is a nuclear medicine imaging examination method to assess blood flow and ventilation in the lungs. Even the smallest circulatory abnormalities can be visualized using a gamma camera, making it essential for the diagnosis of pulmonary embolism. In addition to the diagnosis of pulmonary embolism, lung scintigraphy is used for various lung diseases and malformations. It also offers the advantage that this method can be used to calculate blood flow between the lobes of the lungs to assess surgical risks and provide prognosis after removal of lung tissue in lung cancer.

Function, effect, and goals

A lung scintigraphy is composed of several techniques that can be combined:

  • Ventilation scintigraphy
  • Inhalation scintigraphy
  • Perfusion scintigraphy

Ventilation scintigraphy requires a radioactive noble gas, usually 133Xenon, to be inhaled and exhaled by the patient. The body does not absorb noble gases. During inhalation and exhalation, the gamma camera records 3 images (three-phase scintigraphy): image 1 is taken during inhalation, image 2 during distribution of the gas in the lungs, and image 3 during exhalation of the gas. The gas distribution indicates the ventilation in the respective area. The purpose of this technique is to determine if airflow is obstructed or if the distensibility of the lungs is limited. However, it is technically complex and the patient must inhale and exhale at the right moment. In inhalation scintigraphy, minute, radioactively labeled, particles of a carrier substance are finely vaporized or nebulized and added to the patient’s breathing air. It is usually used before perfusion scintigraphy because it allows the ventilation and blood flow in the lungs to be compared. It also allows the physician to identify the original symptoms and use this knowledge to initiate the correct therapy. In perfusion scintigraphy, the patient is injected intravenously with radioactively labeled protein building blocks that travel through the veins to the lungs. Where blood flow is disturbed, fewer radioactive particles are visible. The patient’s posture during the injection is important in the distribution of the radioactive particles. In healthy individuals, deeper lung areas are imaged more due to gravity, whereas in pulmonary hypertension (increased blood pressure in the lungs), all areas are imaged evenly. If a life-threatening embolism due to a blood clot is suspected, perfusion scintigraphy is usually the first choice and is combined with chest X-ray. It can also detect right-to-left shunts in the pulmonary circulation, where blood is pumped from the lungs into the body through a connection between the pulmonary and systemic circulation without a supply of oxygen. Normally, the radioactive particles remain in the lungs and are also broken down via the lungs. In the case of a shunt, however, they migrate into the systemic circulation and are excreted in the urine via the kidneys. Using the volume of blood that flows through the kidneys per minute, the computer can calculate the volume and extent of the shunt. In lung cancer, inhalation scintigraphy is combined with perfusion scintigraphy before and after surgery to assess the function of the lung or the remaining portion of the lung before and after surgery and to provide a prognosis after surgery. Lung scintigraphy with gallium citrate allows the assessment of cartilage framework diseases and inflammatory processes in the lung and is particularly used in the investigation of pneumoconiosis or tuberculosis. Pneumonia and pulmonary infarction can also be detected more quickly via lung scintigraphy than with other examination methods.

Risks, side effects and dangers

Side effects are rare with lung scintigraphy; at most, there is a risk of minor radiation exposure from the radioactive drugs used, which is considerably less than normal radiation exposure in a year. There are no known interactions with other drugs. In the case of intravenous injection, mild allergic reactions to the protein components may sometimes occur. If protein allergy is present, consider whether pulmonary scintigraphy is useful in this case. Patients who have to take blood thinners (e.g., Marcumar) should expect a small amount of bleeding at the puncture site. Nuclear medicine examinations such as a lung scintigraphy can also be performed during pregnancy with restrictions, but here the healthy development of the child is what counts first and foremost. Possible side effects and risks should be carefully weighed and discussed with the pregnant woman. If necessary, the dose can be reduced. Breastfeeding women should not breastfeed for 48 hours after nuclear medicine examinations. No special preparation is necessary for lung scintigraphy and patients do not need to appear fasting. Patients suffering from asthma should take bronchodilator medication before the examination. The costs are covered by statutory health insurance. Since lung scintigraphy is associated with few risks and side effects, it is a highly recommended method for examining blood flow and ventilation of the lungs and the best examination procedure for diagnosing pulmonary embolism. There are minor limitations in its informative value at most in chronic obstructive pulmonary disease (COPD).