Chest Digital Twin Guides Light Therapy Dosing for Pneumonia

Light-based therapies may help treat infection or inflammation, but externally applied light must pass through chest tissues before reaching the lungs. This makes dosing difficult because anatomy and disease patterns vary between patients. Researchers have now developed a chest “digital twin” to help plan personalized light delivery for pneumonia treatment.

Researchers at the University of São Paulo in Brazil and international collaborators created a computational model that generates a patient-specific digital twin of the thorax. The system uses computed tomography scans, three-dimensional anatomical reconstructions, and high-performance computing simulations. Its purpose is to estimate how much light reaches different lung regions when illumination is applied from outside the body.

The model represents thoracic anatomy as small volumetric elements called voxels. It assigns optical parameters to tissues to estimate light absorption and scattering at different wavelengths. In the study, 12 tissue and structural categories were represented, including skin, fat, muscles, bones, major organs, normally ventilated lung tissue, collapsed regions, infiltrates, and blood vessels.

The platform used Monte Carlo simulation to calculate the behavior of millions of photons as they traveled through heterogeneous chest anatomy. The group included four individuals from Hospital das Clínicas of the University of São Paulo Medical School, including one control subject and three patients with focal bacterial pneumonia, diffuse bacterial pneumonia, and COVID-19 viral pneumonia. Two additional volunteers underwent optical measurements for experimental validation of the model.

The reconstructions showed that healthy lung area decreased from about 91% in the reference subject to 58.9% in focal pneumonia, 54.1% in diffuse pneumonia, and about 69.9% in COVID-19. Light at 808 nanometers produced the highest lung energy deposition among the tested configurations. Lateral and dorsal illumination gave more uniform distribution than frontal illumination alone, while multi-angular illumination at 808 nanometers produced the most uniform and efficient distribution.

Using 808-nanometer infrared light at 100 milliwatts per square centimeter on the skin, average lung irradiance was 0.0234 milliwatts per square centimeter in a healthy lung. It fell to 0.0166 in focal pneumonia, 0.0120 in diffuse pneumonia, and 0.0113 in COVID-19. The work was published in the Proceedings of the National Academy of Sciences, with participation from Texas A&M University and Victoria University of Wellington.

“We're scientists committed to the relevance of our research. We want to solve problems, but we also operate with social responsibility. We don't want to create technology that's too expensive, can't be integrated into the Unified Health System, or used widely. A good treatment must be accessible to the population. The economic reality must be taken into account in what we're developing,” said Vanderlei Bagnato of the São Carlos Institute of Physics at the University of São Paulo.

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São Carlos Institute of Physics at the University of São Paulo