Download Respiratory system scintigraphy

Respiratory system scintigraphy
1. Lung anatomy and physiology
2. Lung Ventilation Imaging
Radioactivity and its dynamic change in lung can be imaged with radioactive
detection equipment during the radioactive gas is inhaled and exhaled. Parameters of
lung ventilation function can be calculated.
2.1. Radiopharmaceuticals
 133Xe
 81mKr
 Radio-aerosols
3. Lung Perfusion Imaging
Particles with diameter greater than 10μm is injected intravenously and these
particles could not pass lung capillary bed because of the diameter of capillary is less
than 8μm. So these particles are blocked in capillary bed. The distribution of these
particles in lung is proportional to the blood flow in pulmonary artery.
3.1. Radiopharmaceuticals
99mTc-MAA (Macroaggregated Albumin)
3.2. Clinical Indications

Assessing the probability of acute or chronic pulmonary thromboembolic disease;
establishing the presence of chronic, unresolved pulmonary emboli;

Quantifying differential pulmonary function;

Evaluating lung transplants;

Evaluating the effects of congenital heart/lung disease;

Confirming the presence of bronchopleural fistulae;

Evaluating the effects of chronic pulmonary parenchymal disorders such as cystic
fibrosis.
3.3. 2.5 Clinical Usage
3.3.1. Diagnosis of Pulmonary Embolism
Ventilation and perfusion to broncho-pulmonary segments are matched in a healthy
individual. In pulmonary embolic disease, segmental reduction in perfusion occurs
with maintenance of normal ventilation. This leads to the mismatch of perfusion and
ventilation in the broncho-pulmonary segment.
Pulmonary embolism typically causes multiple, wedgeshaped, bilateral perfusion
defects. Perfusion lung scintigraphy has an extremely high sensitivity in the diagnosis
of pulmonary embolism , since a normal lung scan virtually excludes the diagnosis.
Since the scan "sees" a absent perfusion but not the embolus, it is not completely
specific. Criteria for the size and number of unmatched perfusion defects create a
"probability" factor in four classes.

Normal Perfusion - Less than 1% chance.

Low Probability - Matched Defects less than 10-30% chance (studies vary).

High Probability - Unmatched Defects, probability 90%.

Intermediate Probability - Outside other groups, probability 10-90%.
3.3.2. Evaluation of the Severity of Pulmonary Embolism
Perfusion lung scintigraphy is the best technique for evaluating the severity of
embolism. This can be achieved by simply counting the number of unperfused lung
segments on all six views obtained with the gamma camera, thus obtaining a reliable
index of severity of the disease.
3.3.3. Evaluation of Chronic Obstructive Pulmonary Disease
Chronic bronchitis causes a patchy, non-segmental decrease of perfusion in the lung
parenchyma. Defects may be located everywhere in the lungs, although they appear
more frequently in the lower regions, especially in exacerbations.
A quite recent application of perfusion lung scintigraphy is in evaluating the
inhomogeneity of pulmonary emphysema when considering surgical intervention to
reduce lung volume.
Aerosols are more suitable for evaluating ventilation in COPD.
（孙晓光）