respiratorysystem呼吸系统ppt课件.ppt

4.3 Hypoplasia or Aplasia of Pulmonary Artery Lung perfusion scan shows perfusion defects or reduced tracer distribution of the affected lung without corresponding ventilation abnormalities. Hypoplasia or aplasia of pulmonary artery can be differentiated from PE, considering clinical history and chest radiograph. 4.4 Pulmonary Artery Impairment with Collagenosis and Aortitis Collagenosis and aortitis commonly affect pulmonary artery. Lung perfusion scan shows segmental defects. Ventilation function is usually normal. Lung perfusion scan can provided the extent and scope of the lung arteries impairment. V/Q scan interpretation of these conditions must be based on their clinical data. 4.5 Asthma Asthma produces bronchospastic narrowing of the airways, resulting in decreased ventilation. Focal lobar, segmental or subsegmental ventilation defects are present on the ventilation image during an acute asthma attack. Bronchospasm induces localized hypoxia, which in turn produces localized vasoconstriction and perfusion scan defects that match the ventilation defects. Most V/Q defects caused by asthma will resolve with 24 hours of bronchodilator therapy. Thank you! 3.1 Principle The radioactive gas or aerosol in the closed system can be inhaled by respiratory passage, and deposit on the lining of the bronchoalveolar spaces. The distribution of radioactivity within the lungs is proportional to regional ventilation. So regional airway patency and ventilation function can be assessed through γ camera or SPECT detecting the radioactivity distribution of lungs. 3.2 Methods Pharmaceuticals used in ventilation imaging can be divided into two groups on the basis of their various physical forms; radioactive gas, and aerosols. The most commonly used radioactive gases are Xenon-133 (133Xe), but aerosol imaging is by far the most usual technique for ventilation imaging. 3.2 Methods 3.2.1 Radioaerosol imaging Currently, the most commonly used radioaerosol is Tc-diethylenetriaminepenta