Physical properties and use of pertechnegas as a ventilation agent.

Pertechnegas, a variant of technegas, produces similar ventilation images with a much increased clearance rate. This work aims to determine the properties of pertechnegas and its use as a ventilatory agent. Methods: Fourteen men and 11 women were scanned for PE after pertechnegas ventilation. Six were reimaged with technegas within 1 wk. Studies were reported according to PIOPED criteria. Pertechnegas samples were analyzed by transmission electron microscopy (TEM), cascade impaction (CI), aerosol mobility analysis (AMA), Fourier transform mass spectrometry (FTMS), x-ray photoelectron spectroscopy (XPS), paper strip (PC) and gas chromatography (GC). Results: Post-test probabilities were normal in 5, low in 8, high in 5 and indeterminate in 7. There were 15 Grade 1, 6 Grade 2 and 4 Grade 3 studies. All Grade 3 patients had FEV 1 < 1.5 liters, 3 with rates < 1.0 liter. Patients with high probability had proven deep venous thrombosis in three by venography and in one by doppler. TEM identified 0.3 μm salt particles. CI demonstrated a 7-min time to half clearance from the chamber for particles in the < 0.1 μm range. AMA indicated all particles were < 0.032 μm when salt was excluded. Pertechnegas behaves in PC as pertechnetate. GC demonstrated CO levels below 516 ppm. CO 2 concentrations were 0.146 ± 0.0009%. FTMS found molecular pertechnetate species including 99 TcO 3 (OH) + , 99 TcO 3 (OH) 3 + and Na 99 TcO 3 (OH) 3 + . XPS confirmed that these Tc species exist in oxidation state +7. Conclusion: Comparison with technegas images in the follow-up group proved equivalent in the first five views, but indistinct lung boundaries and a high background activity characterized the final anterior images. The active component of pertechnegas is molecular pertechnetate.