Deposition of aqueous aerosol of technetium-99m diethylene triamine penta-acetic acid generated and delivered by a novel system (AER(x)) in healthy subjects

Deposition of technetium-99m diethylene triamine penta-acetic acid aqueous radioaerosols generated by a novel aerosol delivery system (AER(x)) was stu died in six healthy subjects using both planar and single-photon emission t omography (SPET) imaging. AER(x) is a microprocessor-controlled. bolus inha lation device that is actuated at pre-programmed values of inspiratory flow rate and volume. The aims of the study were to determine the effects of po sture and inhaled volume upon deposition of the aerosol in the lungs. Each subject inhaled the radioaerosol in two positions (supine vs sitting) and w ith two inspiratory manoeuvres [vital capacity (VC) vs "fixed volume" of 11 above functional residual capacity]. Simultaneous transmission-emission pl anar and tomographic images were acquired. The results showed diffuse depos ition of the aerosol in the lung. Neither the breathing manoeuvre nor the p osture was found to affect the distribution of the aerosol as measured by t he ratio of the activity (counts per pixel) in the peripheral:central (pene tration index, PI) or in the apex:base regions of the planar lung images (P >0.1). A small, albeit statistically significant, difference in PI (P<0.03) was found between VC and fixed volume sitting manoeuvres with SPET only. T he PI values themselves indicate that the radioaerosol was well distributed in the lung, with the periphery having 45%-64% of the activity of the cent ral region. Superposition of transmission SPET lung outline on emission SPE T visually confirmed the excellent peripheral deposition of the aerosol. Th e AER(x) system showed high efficiency of delivery, with approximately 50% of the extruded dose in the device depositing in the lung. The uniformity o f radioactivity distributed throughout the lung is attributed to the fine p article size (mass median aerodynamic diameter of 2 mu m) of the aerosol an d the electronic control of aerosol inhalation by the device. In conclusion , the AER(x) system can be ideal for Jiff use aerosol deposition of therape utic or diagnostic agents and is largely unaffected by inhaled volume and p osture. The efficiency of the device device can limit the total radiation e xposure of patients and staff administering the radioaerosols, and can make it suitable for delivery of expensive drugs.