A new study has determined that perfusion images acquired before and during vasodilation could distinguish between patients with pulmonary arterial hypertension (PAH) and controls without the disease. The study, published in Respiratory Research, revealed significant differences in the heterogeneity associated with vertical gradients in perfusion.

“Here, we used positron-emission tomography and high-resolution computer tomography (PET-CT) imaging characterize the spatial distributions of pulmonary perfusion and ventilation in patients with PAH,” the authors wrote. “We hypothesized that differences in pulmonary perfusion images acquired at baseline and during vasodilation could identify characteristic perfusion patterns between controls and PAH subjects, even in PAH subjects deemed ‘non-responders’ to acute vasodilation during cardiac catheterization.”

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The research team studied 9 participants: 5 healthy controls and 4 patients with PAH. Spirometry data on all participants were collected, and PET-CT imaging with radioisotope injection was performed at baseline and while the participants were breathing oxygen and nitric oxide (O2+iNO).

The results revealed significant perfusion differences between patients with PAH and controls when breathing O2+iNO. Specifically, the authors found significantly lower vertical gradients in perfusion as well as residual perfusion heterogeneity in the patients with PAH.

The magnitude of vasodilation in the healthy controls when breathing O2+iNO was unexpected, and the significant differences between patients with PAH and controls suggest that PET-CT imaging while breathing O2+iNO could serve as a biomarker for PAH.

The authors hope that this finding could result in earlier detection of PAH and subsequent improvements in survival among these patients. They caution that the small sample size limits the ability to draw firm conclusions and that larger studies on the inhalation of NO during imaging modalities such as dual-energy CT, which are available in clinics, will be necessary to more broadly implement these findings.


Winkler T, Kohli P, Kelly VJ, et al. Perfusion imaging heterogeneity during NO inhalation distinguishes pulmonary arterial hypertension (PAH) from healthy subjects and has potential as an imaging biomarker. Respir Res. Published online December 1, 2022. doi:10.1186/s12931-022-02239-8