An application of ^<99m>Tc-technegas to pulmonary ventilation study

^<133>Xe和^< 81> Kr气体用于常规通风检查，但这些气体不可用于门诊检查，例如肺栓塞。^<99m> tc -气溶胶也应用于通风研究，但气溶胶粒径太大，无法评估通风情况。^<99m> tc - techgas （^<99m>Tc-gas）的开发就是为了避免这些缺点。^<99m>Tc-gas是由燃烧（2500‰）产生^<99m> tc -高技术酸盐在碳坩埚中的技术气体发生器。电子显微镜下，绝大多数^<99m>Tc-gas的颗粒直径为5-30nm。通过三次深吸气吸入肺内约37MBq的^<99m>的tc -气体，同时在发生器内注入296MBq的^<99m>的tc -高技术酸盐。吸入^<99m> tc气体后立即出现血液活性，2小时后为吸入剂量/分血量的0.2%。吸入后尿活性增加，24小时累积剂量为抽吸剂量的4.96%。^<99m>Tc-gas在肺中的生物半衰期为135h，即使在24h后肺图像仍稳定。肺部辐射剂量为0.004 Gy/37MBq。在与放射性惰性气体（^<133>Xe, ^<81m>Kr）， ^<99m>Tc-gas的对比研究中，大多数患者的Tc-gas分布与惰性气体相似。阻塞性肺疾病患者虽然在中央气道出现热点，但^<99m>Tc-gas穿透到周围肺野。这些结果表明，^<99m> tc气体吸入研究是一种安全有效的评估慢性阻塞性肺疾病患者通气功能的方法。

^<133>Xe and ^<81m>Kr gas are used for the routine examination of ventilation, but these gases are not available for ambulant test, for example to pulmonary embolism. ^<99m>Tc-aerosol is also applied to ventilation study, but particle size of aerosol is too large to asess the ventilation. ^<99m>Tc-technegas (^<99m>Tc-gas) was developped to avoid such disadvantages.^<99m>Tc-gas is produced by burning (2500ﾟC) ^<99m>Tc-pertechnetate in a carbon crucible in the technegas generator. Most particles of ^<99m>Tc-gas were 5-30nm in diameter as determined by electron microscopy.About 37MBq of ^<99m>Tc-gas was inhaled in the lung by three times of deep inspiration, when 296MBq of ^<99m>Tc-pertechnetate was injected in the generator. Blood activity was appeared immediately after inhalation of ^<99m>Tc-gas and it was 0.2% of the inhaled dose/litter of blood after 2 hours. Urine activity was also increased after inhalation and cumulative dose was 4.96% of the in haled dose after 24 hrs. Biological half time of ^<99m>Tc-gas in the lung was 135 hrs and pulmonary image was stable even after 24 hrs. Radiation dose to the lung was 0.004 Gy/37MBq.In a comparative study with radioactive inert gases (^<133>Xe, ^<81m>Kr), ^<99m>Tc-gas showed a similar distribution to the inert gas in most patients. Although the patients with obstructive lung disease showed hot spots in the entral airways, ^<99m>Tc-gas penetrated to the peripheral lung fields.These results suggest that ^<99m>Tc-gas inhalation study is safe and useful method to evaluate ventilatory function even in patients with chonic obstructive pulmonary diseases.