Lung scintigraphy

The lung scintigraphy is a nuclear medical methods for assessing the blood flow ( perfusion ) and the ventilation ( ventilation ) of the lung . A distinction is made between lung perfusion, lung ventilation and lung inhalation scintigraphy. The combined method of lung ventilation and lung perfusion scintigraphy is also known as V / P scintigraphy .

Technical procedures

The regional ventilation conditions of the lungs can be visualized and also quantified with a lung ventilation scintigraphy or with a lung inhalation scintigraphy . For ventilation scintigraphy, the patient inhales a gas mixture that contains a radioactive component (for example ¹³³ xenon , ¹²⁷ xenon or ^81m krypton ). For inhalation scintigraphy, an aerosol made of particles marked with ^99m technetium is usually used, which, although it cannot penetrate the bronchial system as deeply as a gas, shows comparable test results with significantly lower technical effort. A gamma camera is then used to produce either planar recordings in various projections or three-dimensional images using SPECT technology.

In the Lungenperfusionsszintigraphie circulation conditions of the lung are depicted; they can also be quantified regionally. Here particles marked with ^99m technetium (for example macro- colloids or technetium-marked albumin particles (Tc-99m-MAA)) are injected intravenously . These particles lead to multiple microembolisms in the perfused lung sections; however, due to the small amount of substance, these embolisms are not hemodynamically effective. The recordings are made either as planar or as SPECT recordings.

Indications

The most common indication for lung scintigraphy is suspicion of pulmonary embolism . In this case, an examination of the ventilation is usually carried out with low activity, followed by a lung perfusion scintigraphy with slightly higher activity. Both recordings are compared with each other. If there are areas that are well ventilated but poorly supplied with blood (so-called mismatch ), the finding must be interpreted as a pulmonary embolism. If there are sections of the lung that are both poorly ventilated and poorly supplied with blood ( match , see also Euler-Liljestrand mechanism ), atelectasis or infiltrates from pneumonia may be present. Areas with poor ventilation but good circulation ( reverse mismatch ) can be found, for example, in chronic obstructive pulmonary disease . In the best case lies with the diagnosis a lung scan of the X-ray image before the lungs.

Lung perfusion scintigraphy to assess the postoperative lung function before a planned partial lung resection (for example in the case of lung cancer ) is carried out less frequently . An examination of the ventilation conditions is unnecessary here. There are planar images of ventral and dorsal customized and the disintegrations ( counts counted) to certain parts of the lung. The relative loss of counts due to the planned operation then roughly coincides with the expected relative loss of vital capacity .

Contraindications

According to the current guidelines for lung scintigraphy, pregnancy is not a contraindication for lung scintigraphy if pulmonary embolism is suspected , but is explicitly recommended because of the lower radiation dose compared to CT angiography (CTA). Scintigraphy is also preferable to CTA when breastfeeding because of the lower organ dose of the mammary gland, which is particularly sensitive to radiation during this period . After a lung scintigraphy, the breastfeeding woman should express and discard the milk for 48 hours. However, because of the injected contrast agent , which passes into breast milk, this is also recommended for CTA.

Radiation exposure

The radiation exposure for the patient during a lung scintigraphy is relatively low. At 1.5 mSv for a typical examination with lung inhalation and lung perfusion scintigraphy, each performed with ^99m technetium, it is above that for X-ray images of the lungs in two planes, but clearly below that for computed tomography of the thorax .

The organ dose for the mammary gland is 0.8 mSv for inhalation / perfusion scintigraphy compared to 20–50 mSv for thoracic CTA . When performing perfusion SPECT with reduced activity (50 MBq ) in accordance with the guidelines , the fetal dose is 0.11–0.20 mGy

literature

• Harald Schicha, Otmar Schober: Nuclear Medicine: Basic Knowledge and Clinical Application , 7th Edition, Schattauer , Stuttgart 2013, ISBN 978-3-7945-2889-9 .

Individual evidence

1. ↑ C. Schümichen, M. Schmidt, Th. Krause: DGN recommendation for action (S1 guideline) Lung scintigraphy as of 11/2017. (PDF) German Society for Nuclear Medicine eV, November 30, 2017, accessed on September 8, 2019 . 
2. ↑ Marika Bajc, Berit Olsson, Anders Gottsäter, Cecilia Hindorf, Jonas Jögi: V / P SPECT as a diagnostic tool for pregnant women with suspected pulmonary embolism . In: European Journal of Nuclear Medicine and Molecular Imaging . tape 42 , no. 8 , 2015, p. 1325-1330 , doi : 10.1007 / s00259-015-3056-z , PMID 25916742 , PMC 4480826 (free full text).

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