Ventilation Scintigraphy With Radiolabeled Carbon Nanoparticulate Aerosol (Technegas): State-of-the-Art Review and Diagnostic Applications to Pulmonary Embolism During COVID-19 Pandemic.

ABSTRACT: Invented and first approved for clinical use in Australia 36 years ago, Technegas is the technology that enabled ventilation scintigraphy with 99m Tc-labeled carbon nanoparticles ( 99m Tc-CNP). The US Food and Drug Administration (FDA) has considered this technology for more than 30 years but only now is getting close to approving it. Meanwhile, more than 4.4 million patients benefited from this technology in 64 countries worldwide. The primary application of 99m Tc-CNP ventilation imaging is the diagnostic evaluation for suspicion of pulmonary embolism using ventilation-perfusion quotient (V/Q) imaging. Because of 99m Tc-CNP's long pulmonary residence, tomographic imaging emerged as the preferred V/Q methodology. The FDA-approved ventilation imaging agents are primarily suitable for planar imaging, which is less sensitive. After the FDA approval of Technegas, the US practice will likely shift to tomographic V/Q. The 99m Tc-CNP use is of particular interest in the COVID-19 pandemic because it offers an option of a dry radioaerosol that takes approximately only 3 to 5 tidal breaths, allowing the shortest exposure to and contact with possibly infected patients. Indeed, countries where 99m Tc-CNP was approved for clinical use continued using it throughout the COVID-19 pandemic without known negative viral transmission consequences. Conversely, the ventilation imaging was halted in most US facilities from the beginning of the pandemic. This review is intended to familiarize the US clinical nuclear medicine community with the basic science of 99m Tc-CNP ventilation imaging and its clinical applications, including common artifacts and interpretation criteria for tomographic V/Q imaging for pulmonary embolism.

99mTc-Leukocyte Scintigraphy Revealed Viral Pulmonary Infection in a COVID-19 Patient.

Tc-leukocyte scintigraphy was performed on a 40-year-old woman with spiking fevers. A focus of intense uptake in the right upper thorax was identified, concerning for infection along the central line in the superior vena cava. Additionally, heterogeneously increased uptake in both lungs was noted, which suggested pulmonary infection. CT images of the chest showed patchy ground-glass changes in both lungs and a large consolidation in the right lower lobe, which were consistent with changes for COVID-19 (coronavirus disease 2019). Severe acute respiratory syndrome coronavirus 2 RNA test was positive. This case demonstrates that leukocyte uptake in bilateral lungs could reveal viral pulmonary infection in COVID-19.