Ventilation scintigraphy or pulmonary ventilation scintigraphy is one of three different nuclear medicine diagnostic procedures grouped under the term pulmonary scintigraphy. Ventilation scintigraphy is mainly used when pulmonary embolism is suspected. It allows precise assessment of ventilation conditions in the bronchial and pulmonary systems. Radioactive isotopes of the noble gases xenon or krypton are used as the radiation source.
What is ventilation scintigraphy?
Ventilation scintigraphy, or lung ventilation scintigraphy, is one of three different nuclear medicine diagnostic procedures used to check the lungs. Ventilation scintigraphy, or pulmonary ventilation scintigraphy, is one of three different nuclear medicine diagnostic procedures for checking the lungs. The three procedures, ventilation scintigraphy, lung perfusion scintigraphy and lung inhalation scintigraphy are combined under the term lung scintigraphy. The radiation source used for ventilation scintigraphy is radioactive isotopes of the noble gases xenon or krypton (radiopharmacon). The radioactive noble gas is inhaled and exhaled via a closed circuit. Ventilation scintigraphy is one of the non-invasive imaging techniques that provide detailed and precise images of the alveolar and bronchial ventilation situation. The diagnostic procedure is mainly used in cases of suspected presence of pulmonary embolism. If the suspicion is confirmed, a pulmonary perfusion scintigraphy is often also obtained to provide a differential diagnosis of whether the arterial perfusion situation is consistent with the ventilation scintigraphy or whether, for example, there is a chronic dysfunction of a specific area of the lung based on causes other than acute arterial occlusion (pulmonary embolism). The radiation exposure to which the patient is exposed during the examination is 1.1 to 1.2 mSv (millisievert), which is about half of the natural annual radioactive radiation in Germany in the lowlands. Natural radiation can be extremely high in other regions of the world, such as on the Atlantic coast of Brazil, where it reaches about 80 mSv per year.
Function, effect, and goals
Ventilation scintigraphy is mainly used in cases of suspected pulmonary embolism because the diagnostic procedure provides precise information about the ventilation conditions of the bronchi and lungs. Ventilation scintigraphy is also usually performed before lung resection, the removal of part of the lung. A third indication for combined use of ventilation and lung perfusion scintigraphy is after a so-called Norwood operation, a surgical correction of hypoplastic left heart syndrome. The study is also applied to identify and differentiate congenital lung abnormalities. The imaging, non-invasive, diagnostic procedure does not allow conclusions to be drawn as to whether there are acute or chronic failures of specific lung areas. To provide clarity in this regard, ventilation scintigraphy is often used in combination with lung perfusion scintigraphy when pulmonary embolism is suspected. This is an examination procedure to determine the perfusion conditions in the area of the lungs and bronchi. If the lung areas showing functional disturbances are congruent with areas in which circulatory disturbances or arterial occlusions due to thrombi have been detected, i.e. a so-called match is present, it is not an acute embolism because an arterial thrombus initially only leads to a circulatory disturbance. Instead, the findings provide evidence of atelectasis or infiltrates due to pneumonia. Atelectasis is an area of the lung in which the alveoli have collapsed and become irreversibly stuck together, thus losing their function for gas exchange. In such a situation, an X-ray of the lungs is recommended as a differential diagnostic procedure. Only in the presence of a mismatch between ventilation scintigraphy and pulmonary perfusion scintigraphy is the conclusion of acute pulmonary artery embolism obvious. To perform ventilation scintigraphy, it is important for the patient to master a calm breathing technique, especially during inspiration. Therefore, short breathing exercises by the patient under guidance are recommended before starting the examination.At the beginning of the ventilation scintigraphy, the patient inhales and exhales an air mixture for about 3 minutes via a breathing mask in a closed system, to which radioactive isotopes of the noble gas xenon or krypton are added in small quantities. During the inhalation phases, the images are taken. The entire procedure takes about 15 minutes. Often, to confirm the findings, additional cross-sectional images of the lungs are taken, which can be done within the ventilation scintigraphy. In this case, the time required for the examination is extended to about 30 minutes.
Risks, side effects, and hazards
Ventilation scintigraphy is, in principle, a non-invasive procedure, so there are no risks of infection or other risks that are generally associated with an invasive procedure. Also, no chemical substances or medications are used other than inhalation of the radiopharmaceutical, so there is no need to fear any side effects. Therefore, there are no interactions with other medications. The radiation exposure from the inhaled radiopharmaceutical in the form of radioactive isotopes of the noble gases xenon or krypton is low at 1.2 mSv. Nevertheless, for precautionary reasons, a required repeat examination should take place no earlier than 3 months after the previous ventilation scintigraphy. Pregnancy is considered an absolute contraindication for the diagnostic procedure. Ventilation scintigraphy for pregnant women is indicated only in absolutely exceptional situations. Breastfeeding mothers should not use their milk for up to 48 hours after the examination in order to exclude possible radiation exposure of the baby from the outset. In patients suffering from a particularly severe form of asthma or who are artificially ventilated, the benefits and risks of the examination should be weighed. As a rule, it is indicated to switch to another diagnostic procedure in these patients. Patients suffering from a milder form of asthma take a drug to dilate the bronchi (bronchial dilation) before the examination to avoid complications during the examination and to obtain the most meaningful diagnostic result.
