The APE nebuliser — a new delivery system for the alveolar targeting of particulate technetium 99m diethylene triamine penta-acetic acid

Abstract

We report the validation of a new delivery system--aerosol production equipment (known by the acronym APE), which generates a particulate aerosol of technetium 99m diethylene triamine penta-acetic acid (DTPA) with a mass-median aerodynamic diameter of 0.35 microns and a geometric standard deviation of 1.8 Twenty subjects were studied; in group 1 were 12 healthy men with normal spirometry; in group 2 were 8 men with AIDS who had mildly abnormal lung function following an episode of pneumocystis pneumonia-spirometry FEV1 3.08 (0.73) L, FVC 4.83 (0.82) L [mean (SD)]. The APE nebulizer was used to form a particulate aerosol with 200 MBq of 99mTc DTPA, which was collected in a 35 1 reservoir of air, which was subsequently inhaled. The mean (SD) inhalation time was 4.7 (0.44) min. The output of the nebulizer (% of activity inhaled) was 82%. Using planar imaging, the penetration index (right lung) in group 1 was 0.93 (0.18), mean (SD), and in group 2 it was 0.91 (0.12). There was virtually no tracheal deposition and extrapulmonary deposition (oropharynx and stomach) was less than 5% of the aerosol delivered. Single-photon emission tomography (SPET) studies carried out in five patients from group 1 confirmed homogeneous intrapulmonary deposition of 99mTc-DTPA. In view of the excellent intrapulmonary deposition of 99mTc-DTPA produced by the APE nebulizer, it may provide an alternative to conventional ventilation studies using radioactive gases.

Use of Single Photon Emission Computed Tomography in Aerosol Studies

“…Generation of submicronic particles with reasonably high output for inhalation has been a task for PE diagnostic use in nuclear and thoracic medicine. This problem was tackled, e.g., by Burch et al (1986) using Technegas [99mTc-labelled carbon particles with sizes < 200 nm dispersed in argon gas (Strong and Agnew, 1989;Isawa et al, 1991)]; and more recently by Miller et al (1991) using another novel aerosol delivery system. Note that for most of the alternatives to Tc99m DTPA aerosols, an increased retention due to slow clearance from the lung will increase the radiation dose to the patient [e.g.…”

“…Burch et al (1986) used it to compare the transverse lung slices in the same patient after Technegas inhalation and lung perfusion. Similarly Miller et al (1991) utilized SPECT (transverse slices) to confirm the homogeneity of intrapulmonary deposition with minimal trachea! and extrapulmonary (oropharynx and stomach) deposition with their aerosol (mass median aerodynamic diameter, MMAD, 0.35pm, geometric standard deviation, GSD, 1.8) .…”

Aerosol recovery from large-volume reservoir delivery systems is highly dependent on the static properties of the reservoir

“…In these systems, minimal initial fluid volumes are required and the whole volume of the generated aerosol will be inhaled without loss of aerosol during expiration. In the ambient dry atmosphere inside the aerosol reservoir, the aerosol droplets will evaporate depending on relative humidity and solute content [8]. Under optimal drying conditions it is possible to generate dry particles [6,8,9].…”

“…In the ambient dry atmosphere inside the aerosol reservoir, the aerosol droplets will evaporate depending on relative humidity and solute content [8]. Under optimal drying conditions it is possible to generate dry particles [6,8,9]. Depending on choice of the solute concentration and drying conditions, the diameter of the aerosol particles will decrease during evaporation [8], improving penetration in the peripheral airways after inhalation with increased deposition after hygroscopic growth [8,10].…”

“…Depending on choice of the solute concentration and drying conditions, the diameter of the aerosol particles will decrease during evaporation [8], improving penetration in the peripheral airways after inhalation with increased deposition after hygroscopic growth [8,10]. This mechanism has been described to be particularly advantageous for the alveolar targeting of aerosols in certain diagnostic and therapeutic applications [8,10,11].…”