Ventilation scintigraphy with lipophilic cationic compounds

Objective On the basis of our hypothesis that lipophilic cations may be more suitable for ventilation lung scintigraphy than the conventional technetium-99m diethylenetriamine penta-acetic acid (Tc-99m-DTPA), comparative studies were carried out. Basic methods The nebulization potential of nine routine radiopharmaceuticals was compared on medical and scintigraphy-specific nebulizers. This was followed by ventilation scintigraphy in 14 patients with chronic obstructive airway disease (n = 13) or pulmonary embolism (n = 1) where either Tc-99m-methoxyisobutylisonitrile (n = 10) or Tc-99m-tetrofosmin (n = 4) was used. Same-patient comparison with Tc-99m-DTPA ventilation scan was available in six patients using the same acquisition protocol. Comparison with Tc-99m-DTPA was made with respect to the nebulization rates, radioactivity delivered per unit of radioactivity available for inhalation, and regional distribution of inhaled counts. Results Lipophilic cation solutions had a significantly higher nebulization rate compared with Tc-99m-DTPA using the medical nebulizer (235%, P<0.01) and 370% on scintigraphy-specific nebulizer (P<0.01). More than three times the counts of Tc-99m-methoxyisobutylisonitrile or Tc-99m-tetrofosmin was deposited in the body compared with Tc-99m-DTPA aerosol per megabecquerel activity inhaled (1.5 vs. 0.4 kcounts/MBq) (P<0.001), preferentially in the lungs (75.2 vs. 65.2%), at the expense of oropharynx and stomach. Within the lungs, about 50% more counts were deposited in the outer one-third lung with lipophilic cations. Overall, therefore, more than 12 times the radioactivity deposition was achieved in the peripheral one-third of the lungs with the lipophilic cations. Conclusion Ventilation lung scanning with lipophilic cations is a viable substitute of nanoparticle scintigraphy (technegas and pertechnegas, which are expensive and technically far more demanding). Nucl Med Commun 29:987-993 (C) 2008 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.