Technegas is an ultra-fine dispersion of Technetium-labelled carbon, produced by heating Technetium-99m in a carbon crucible for a few seconds at 2,750 degrees Celsius.
The resultant gas-like Technegas, thus produced in a Technegas generator, is a cluster of nano-sized (~35nm) pure carbon platelets of hexagonal shape fully encapsulating Technetium metal crystals. The small size and hydrophobic properties together confirm ideal characteristics for gas-like behaviour on inhalation into the lungs. Once inhaled by the patient suspected of having a Pulmonary Embolism, the patient is then imaged under a gamma camera in the ventilation part of a Ventilation/Perfusion SPECT scan. Technegas penetrates to the sub-segmental areas of the lung and is trapped by surfactant in the alveolar walls. The Technegas generator is a mobile, microprocessor which produces Technegas in a safe and controlled environment.
With the uptake in SPECT imaging, V/Q SPECT results with Technegas can be argued to be superior to Planar imaging and CT when comparing Specificity, Sensitivity, Accuracy and Negative Predictive Value. Of significant interest, when compared to CT, is the low radiation dose imparted by V/Q SPECT imaging. This is important in all patients but particularly in young women with proliferating breast tissue. No other diagnostic imaging method has proven itself more effective than the V/Q scan in the diagnosis of Pulmonary Embolism. Technegas, used in the ventilation part of the V/Q scan, is cost-effective, simple to perform and accurate. Study after study confirm that spiral CT should not be used in isolation to exclude a diagnosis of PE and negative findings on CT cannot definitely exclude PE.
“Lung Scintigraphy has a superior sensitivity combined with adequate specificity and low rate of non-diagnostic tests. The low radiation dose, the possibility to quantify the degree of embolism and to use the test for follow-up of treatment of embolism and its feasibility in very sick patients, contribute to the priority of lung scintigraphy over Computed Tomographic Pulmonary Angiography”. Bajc et al, 2002.