Comparability of Quantifying Relative Lung Ventilation with Inhaled Tc-Technegas and Xe in Patients Undergoing Evaluation for Lung Transplantation.

Tc-Technegas was recently approved by the U.S. Food and Drug Administration as a radiopharmaceutical for ventilation scintigraphy. However, there are currently no data comparing the quantification of relative lung ventilation with Tc-Technegas with that performed using the standard approach with inhaled Xe. We performed a secondary analysis of data from prospectively recruited participants in a phase 3 trial undergoing evaluation for lung transplantation who received both Xe and Tc-Technegas ventilation imaging. The Xe and Tc-Technegas images were analyzed asynchronously using semiautomatic segmentation to extract the relative lung ventilation percentages. The anterior and posterior Tc-Technegas images were analyzed to derive 3 sets of relative ventilation percentages (posterior, anterior, and geometric mean data) and compared with the values from posterior Xe images. We evaluated for correlation and agreement between the relative lung ventilation percentages obtained using these 2 radiopharmaceuticals. In a cohort of 74 participants, we found a strong positive correlation in the relative lung ventilation quantified using Xe with that using Tc-Technegas. A high level of agreement was demonstrated on the Bland-Altman plot comparing the 2 imaging modalities. Seventy-two of 74 participants (97.3%) had their relative ventilation percentage measurements within ±15% for Xe and Tc-Technegas. The differences in relative ventilation measurements were within the 95% CI limits of the mean for 70 of 74 participants (94.6%) and within a narrower ±10% threshold for 68 of 74 participants (91.9%), again reflecting the comparability of the 2 techniques. The strongest correlation coefficient ( = 0.79) was observed between the relative ventilation percentages obtained from Xe and posterior Tc-Technegas images. The geometric mean method had a slightly lower but still comparable correlation ( = 0.77), and as expected, the correlation with the anterior Tc-Technegas images was worst ( = 0.70). We showed a strong positive correlation and high agreement between the relative lung ventilation percentages obtained using Xe and Tc-Technegas. These data provide important clinical evidence supporting the use of Tc-Technegas for quantification of relative lung ventilation.