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

^&lt；133&gt；Xe和^&lt；81m&gt；Kr气体用于常规的换气检查，但这些气体不能用于动态测试，例如肺栓塞。~(99m)Tc-气溶胶也被应用于通风研究，但气溶胶颗粒太大，不利于通风。为避免上述缺点，开发了99m；99m&gt；Tc-tehnegas(^&lt；99m&gt；tc-GAS)。经电子显微镜观察，~(99)T；~(99m)Tc-GAS颗粒多为5~30 nm，经3次深吸气，约37MBq~(-1)~(-1)~(99m&GT；T_(-))~(-1)~(-1)~(-)气体被吸入肺内，发生器内注入~(99)~(99)m~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)~(-)~(99m)~(-1)~(-1)~(？)吸入~(99)m~(99m)Tc-气体后即刻出现血液活性，2小时后为吸入量/升血的0.2%。吸入后尿活度也增加，24小时后累积剂量为减半剂量的4.96%。~(99m)Tg；~(99m)Tc-GAS在肺内的生物半衰期为135小时，24小时后仍显像稳定。肺的辐射剂量为0.004 Gy37MBq。在与放射性惰性气体(~(133)Gt；Xe，~(11)T；~(81)M&GT；Kr)的对比研究中，~(99)M；~(99)T；Tc-气体在大多数患者中的分布与惰性气体相似。虽然阻塞性肺疾病患者的中心气道出现热区，但~(99m)Tc-Gt；~(99)Tg~(-1)GAS可渗透到周围肺野，提示~(99m)Tc~(-Gt)GAS吸入试验是评价慢性阻塞性肺疾病患者肺功能的一种安全、有效的方法。

^<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.