Effect of particle number on lung perfusion images: concise communication

Twelve normal mongrel dogs were injected with decreasing numbers of 99mTc-labeled macroaggreagated albumin particles (99mTc-MAA), and lung images were recorded using both parallel-hole and pinhole collimators. The quality of normal lung images was found to decrease with decreasing numbers of injected radiolabeled particles (from 10,000 to 250 particles per injection). The quality was unaffected by adding carrier MAA. The minimum number of particles compatible with a good-quality image of the normal human lung is approximately 60 radiolabeled particles per gram of lung.