Apparent versus real exposures of nuclear medicine technologists during aerosol lung ventilation scanning.

The exposure of nuclear medicine technologists to airborne radiocontaminants is generally far below the compliance limits. Most of the contamination is external rather than internal deposition. Higher contamination levels approaching the allowable limits are rare. Personal respiratory protection is unwarranted and may have undesirable impressions on patients undergoing lung scanning. Exposures are well controlled by suitable work practices that are in keeping with as low as reasonably achievable (ALARA) principles.

Differences in particle deposition between the two lungs.

Certain inhalational diseases show a predilection for a particular region of one or the other lung that may be related to the site of deposition of inhaled particles. We conducted inhalation studies with monodispersed aerosol particles in 22 healthy student volunteers to determine how deposition varied between the two lungs. Ventilation lung scans were obtained with the subjects seated in front of a gamma camera while breathing radiolabelled particles. Subsequently we made paired comparisons of the radioactivity deposited in corresponding regions of the right and left lungs. Although regional differences in deposition between the left and right lung were often statistically significant, they were not always consistent between individuals. Particle deposition and the degree of penetration differed between the two lungs with there being generally more deposition in the perihilar region of the right lung. We suggest that the anatomy of the central airways may influence the pattern of deposition, thereby introducing disparities in particle deposition between the two lungs. The present findings lend support to experimental lung cast data and to the concept that anatomical differences between the two lungs influence the site of deposition.

A simple method for studying lung ventilation.

A simple method of precisely administering a compact gas bolus during selectable portions of the inspiratory cycle was developed to examine certain fundamental attributes of lung physiology and ventilation. The method allows for a small, well-defined bolus to be delivered during different phases of inspiration in a precise fashion. A pneumatically driven three-way switching valve is synchronized to the breathing pattern and controls the interjection of radioxenon boli in the inspiratory stream, spiking a small portion of the inhaled breath. The 133Xe dispersion and redispersion in the lungs is mapped and the clearance followed. Regional differences are analysed to determine how ventilation might influence the development of lung diseases due to inhaled toxins. Scintillation imaging at 20 frames s-1 allows near real-time characterization of the ventilation distribution. Novelty comes from the application of fast data gathering, the flow through valve design for delivery of tightly compacted boli and from tracing different fractions of the breath. The procedure involves low radiation exposure. An apparatus and method for acquiring data on lung filling and emptying not previously available is described. Potential applications are identified which may allow the re-examination of orthodox lung physiology.

The topography of particle deposition in the human lung.

The effect of varying particle size on the site of deposition of inhaled particles in the human lung was measured in 11 young healthy male subjects. The simultaneous inhalation of two chemically inert, radiolabelled particles, differing in size but in no other respect, controlled for all other variables including airways geometry, breathing pattern and posture. Under conditions of quiet respiration the larger particles (3.5 microns) were preferentially deposited in the upper rather than the lower zones of the lungs as compared with the smaller particles (1.1 microns). Furthermore, the penetrance of the larger particles beyond the mucociliary escalator was greater for 3.5 microns particles in all lung zones and particularly at the apex. These findings may be of significance in the pathogenesis of those diseases induced by the inhalation of particles, vapours or fumes.