Abstract
Two radioaerosol preparations, TechneScan -DTPA (99mTc-DTPA, 40 mCi/3 ml; IPEN-CNEN, São Paulo, SP, Brazil) and TechneScan -DTPA/AEROSOL (99mTc-DTPA/A, 15 mCi/1.5 ml with 0.5 ml ethanol; Mallinckrodt Medical, St. Louis, MO, USA), were compared in pulmonary ventilation studies in terms of total radiocounts and clearance after inhalation. An aerosol with ethanol is supposed to better distribute the radioparticles in the lungs. Twenty normal nonsmoking volunteers (10 men and 10 women), mean age of 23.2 years (range: 20 to 35 years), were studied. Images were obtained immediately and 30, 60 and 90 min after inhalation. Total and regional counts were obtained and the clearance half-lives of both lungs were determined. There was no difference in total counts between the two types of radioaerosol at any time (mean of approximately 188,000 cpm for male and female subjects at time zero in both aerosols). The highest count was obtained in the middle region of both lungs (P<0.001) with both preparations. The clearance half-life did not differ between aerosols (mean of ~80-88 min for male and female subjects for both aerosols). Small nonsignificant regional differences were observed. No differences between genders or between right and left lung were observed. 99mTc-DTPA/A generated the highest output of radioaerosol. 99mTc-DTPA with alcohol costs approximately five times more than the aerosol without alcohol. The present results show that either kind of aerosol may be adopted routinely for use in pulmonary examinations without affecting diagnosis. We suggest that the amount of 740 mBq (20 mCi) of 99mTc-DTPA in 1.5 ml saline can be used for routine examinations resulting in reduction of costs in pulmonary ventilation studies without diagnostic impairment.
Highlights
Improvements in nebulizer efficiency has led to the widespread use of radioaerosols for the evaluation of global and regional pulmonary ventilation [1]
Total counts obtained after 99mTcDTPA inhalation for the right and left lungs and for both genders were not significantly different from the radioactive counts obtained after 99mTc-diethylenetriaminepentaacetic acid (DTPA)/A inhalation (Figure 3)
The highest regional radioactive counts obtained after both 99mTc-DTPA and 99mTcDTPA/A radioaerosol inhalation occurred in the middle region of the lung (P≤0.0001), followed by the lower and upper regions, respectively
Summary
Improvements in nebulizer efficiency has led to the widespread use of radioaerosols for the evaluation of global and regional pulmonary ventilation [1]. The most commonly used one is the jet nebulizer This device generates droplets of a median mass diameter of 1.2 to 6.9 μm and a geometric standard deviation of 1.7 to 2.2 μm, depending mainly on the air flow rate [12]. The UltraventTM system (Mallinckrodt Medical Inc., St. Louis, MO, USA) [13] produces excellent results in intrapulmonary radioaerosol distribution after short periods of inhalation [4,14,15]. MO, USA) [13] produces excellent results in intrapulmonary radioaerosol distribution after short periods of inhalation [4,14,15] It generates particles with a median mass diameter of 0.9 μm according to manufacturer specifications [16]
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