Dr. Andrea Liliana Pacheco Tobo Profile

Dr. Andrea Liliana Pacheco Tobo

at Tyndall National Institute

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Publications (7)

SPIE Journal Paper | 30 November 2023 Open Access

Laser absorption spectroscopy measurements of different pulmonary oxygen gas concentrations in transmittance and remittance geometry: phantom study

Andrea Pacheco, Jean Matias, Konstantin Grygoryev, Martin Hansson, Sara Bergsten, Stefan Andersson-Engels

JBO, Vol. 28, Issue 11, 115003, (November 2023) https://doi.org/10.1117/12.10.1117/1.JBO.28.11.115003

KEYWORDS: Lung, Sensors, Oxygen, Absorption spectroscopy, Tissues, Optical properties, Absorption, Transmittance, Laser spectroscopy, Signal to noise ratio

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SPIE Journal Paper | 1 November 2021 Open Access

Lung tissue phantom mimicking pulmonary optical properties, relative humidity, and temperature: a tool to analyze the changes in oxygen gas absorption for different inflated volumes

Andrea Pacheco, Konstantin Grygoryev, Walter Messina, Stefan Andersson-Engels

JBO, Vol. 27, Issue 07, 074707, (November 2021) https://doi.org/10.1117/12.10.1117/1.JBO.27.7.074707

KEYWORDS: Capillaries, Lung, Absorption, Optical properties, Tissue optics, Liquids, Humidity, Sensors, Data acquisition, Tissues

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Significance: Gas in scattering media absorption spectroscopy (GASMAS) enables noninvasive gas sensing in the body. It is developing as a tool for diagnosis and monitoring of respiratory conditions in neonates. Phantom models with relevant features to the clinical translation of GASMAS technology are necessary to understand technical challenges and potential applications of this technique. State-of-the-art phantoms designed for this purpose have focused on the optical properties and anthropomorphic geometry of the thorax, contributing to the source–detector placement, design, and optimization. Lung phantom mimicking the alveolar anatomy has not been included in the existent models due to the inherent complexity of the tissue. We present a simplified model that recreates inflated alveoli embedded in lung phantom. Aim: The goal of this study was to build a lung model with air-filled structures mimicking inflated alveoli surrounded by optical phantom with accurate optical properties (μa = 0.50 cm − 1 and μs′=5.4 cm−1) and physiological parameters [37°C and 100% relative humidity (RH)], and to control the air volume within the phantom to demonstrate the feasibility of GASMAS in sensing changes in pulmonary air volume. Approach: The lung model was built using a capillary structure with analogous size to alveolar units. Part of the capillaries were filled with liquid lung optical phantom to recreate scattering and absorption, whereas empty capillaries mimicked air filled alveoli. The capillary array was placed inside a custom-made chamber that maintained pulmonary temperature and RH. The geometry of the chamber permitted the placement of the laser head and detector of a GASMAS bench top system (MicroLab Dual O2 / H2O), to test the changes in volume of the lung model in transmittance geometry. Results: The lung tissue model with air volume range from 6.89 × 10 − 7 m3 to 1.80 × 10 − 3 m3 was built. Two measurement sets, with 10 different capillary configurations each, were arranged to increase or decrease progressively (in steps of 3.93 × 10 − 8 m3) the air volume in the lung model. The respective GASMAS data acquisition was performed for both data sets. The maximum absorption signal was obtained for configurations with the highest number of air-filled capillaries and decreased progressively when the air spaces were replaced by capillaries filled with liquid optical phantom. Further studies are necessary to define the minimum and maximum volume of air that can be measured with GASMAS-based devices for different source–detector geometries. Conclusions: The optical properties and the structure of tissue from the respiratory zone have been modeled using a simplified capillary array immersed in a controlled environment chamber at pulmonary temperature and RH. The feasibility of measuring volume changes with GASMAS technique has been proven, stating a new possible application of GASMAS technology in respiratory treatment and diagnostics.

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Proceedings Article | 5 March 2021 Presentation

A standardized approach to validate solid phantom recipes for 3D anthropomorphic phantoms in biophotonics

Sanathana Konugolu Venkata Sekar, Treasa Jiang, Pranav Lanka, Claudia Nunzia Guadagno, Andrea Pacheco, Antonio Pifferi, Stefan Andersson-Engels

Proceedings Volume 11633, 1163307 (2021) https://doi.org/10.1117/12.2579257

KEYWORDS: Biophotonic applications, 3D imaging standards, Solids, Tissue optics, Optical properties, Standards development, Tissues, Spectroscopy, Scattering

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SPIE Journal Paper | 17 November 2020 Open Access

Anthropomorphic optical phantom of the neonatal thorax: a key tool for pulmonary studies in preterm infants

Andrea Liliana Pacheco Tobo, Haiyang Li, Monisha Chakravarty, Sanathana Konugolu Venkata Sekar, Stefan Andersson-Engels

JBO, Vol. 25, Issue 11, 115001, (November 2020) https://doi.org/10.1117/12.10.1117/1.JBO.25.11.115001

KEYWORDS: Optical properties, Lung, Absorption, Heart, Bone, Optical phantoms, Tissue optics, Oxygen, Skin, Silicon

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Proceedings Article | 20 November 2019 Paper

Simulation of near-infrared light propagation through the thorax of a neonate: addressing the optimisation of source and detector positions for measuring lung oxygen content in preterm infants

Andrea Pacheco, Emilie Krite Svanberg, Eugene Dempsey, Stefan Andersson-Engels

Proceedings Volume 11190, 111901C (2019) https://doi.org/10.1117/12.2537875

KEYWORDS: Lung, Sensors, Light, Oxygen, Absorption, Image segmentation, 3D modeling, Light sources, Tissue optics, Skin

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Gas in scattering media absorption spectroscopy shortly called GASMAS, is a tunable diode laser spectroscopic technique developed for the measurement of gas present in turbid media. The technique relies on the sharp and specific absorption lines of gases which enables sensitive measurements of gas concentrations in the presence of a scattering solid medium with much broader absorption features. The Biophotonics laboratory at Tyndall National Institute (Biophotonics@Tyndall) is currently exploring the clinical translation of GASMAS technology into the respiratory healthcare of neonates. In this study, we use computational tools to assess the potential gain in gas absorption signal. One of the challenges in the development of the GASMAS technique is to obtain a sufficiently good signal in the measurements, as the light attenuation is high in tissue and the lungs are interior organs. To have an estimation of the capabilities and limitations in this specific application of gas spectroscopy, we model the transmission of near infrared (NIR) light in tissue when a 760 nm source and a set of 68 detectors are placed in different locations over the thorax. We segmented the main organs of the thorax from anonymized DICOM images of a neonate. This is followed by the creation of 3D computational models to solve light propagation with the diffusion equation, and the modelling of light propagation through the thorax of an infant including optical properties of lung, heart, arteries, bone, muscle, trachea, fat and skin. Finally, we calculate a map of the optimal light source – detector configurations to obtain the highest signal from oxygen gas imprint in the lungs. The use of computational tools such as NIRFAST Slicer 2.0 for investigation and further understanding of the advantages and limitations of the technology is fundamental.

Such simulations enable the recreation of different clinical scenarios and identification of the minimum requirements necessary to further improve the application and develop a bedside clinical device that can potentially be used for continuous monitoring of lung function and control of ventilator settings. The potential capability of measuring non-invasively oxygen, water vapour and carbon dioxide in the lungs, would reduce the need for intubation and extracorporeal membrane oxygenation, as well as lower the incidences of chronic lung disease.

Proceedings Article | 11 July 2019 Paper

A solid phantom recipe for biophotonics applications: a step towards anatomically correct 3D tissue phantoms

Sanathana Konugolu Venkata Sekar, Andrea Pacheco, Pierluigi Martella, Haiyang Li, Pranav Lanka, Antonio Pifferi, Stefan Andersson-Engels

Proceedings Volume 11074, 110741C (2019) https://doi.org/10.1117/12.2526867

KEYWORDS: Optical properties, Tissue optics, Absorption, Scattering, Optics manufacturing, Optical phantoms, Solids, Silicon, Tissues, Biophotonic applications

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Proceedings Article | 4 March 2019 Presentation + Paper

Oxygen gas concentration measurements in the lungs of neonate chest phantom with realistic geometry and tissue optical properties using diode laser spectroscopy

Andrea Pacheco, Pierluigi Martella, Haiyang Li, Monisha Chakravarty, Eugene Dempsey, Stefan Andersson-Engels

Proceedings Volume 10890, 108900J (2019) https://doi.org/10.1117/12.2507977

KEYWORDS: Lung, Oxygen, Optical properties, Image segmentation, Heart, Absorption, Tissues, 3D modeling, Bone, Silicon

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