Katarina Svanberg

Lung function monitoring and prompt diagnosis of lung impairment are essential for optimal patient care. During surgery, anesthesia and ventilator assistance are standard, and mechanical ventilation is often required in severe cases, as highlighted during the recent COVID‐19 pandemic. There is a clear need for powerful, real‐time lung surveillance techniques that can provide feedback to ventilator settings. Gas in Scattering Media Absorption Spectroscopy (GASMAS) measures oxygen and water vapor in the gas‐filled cavities of the lungs, enabling assessment of lung aeration and oxygen concentration. Proof‐of‐concept studies in neonates have demonstrated the potential of GASMAS for continuous lung monitoring. This paper presents progress toward extending the method to older children and adults. By employing a semiconductor tapered amplifier, the diode‐laser output at the oxygen absorption wavelength (764 nm) was increased from ~30 mW to 900 mW. This enhanced power enabled model experiments on a polystyrene phantom and on ventilated porcine lungs, with added pork slabs simulating up to 9 cm total tissue thickness. Strong oxygen absorption signals were detected with both external illumination and internal delivery via the tracheal tube, demonstrating the potential of GASMAS for non‐invasive lung monitoring in large tissue phantoms simulating larger patient populations.

Malignant diseases are the second most common cause of death worldwide.¹ The incidence rate is expected to increase by 47% by 2040, reflecting both growth and aging of the population as well as changes in other risk factors associated with socioeconomic development.² In the combat of malignant diseases, there are presently three dominating and well-developed treatment modalities: surgery, chemotherapy, and radiation therapy, whereas other modalities such as immunotherapy^3,4 are receiving increased attention.

Acute rhinosinusitis is a common infectious disease, which, in more than 90% of cases, is caused by viruses rather than by bacteria. Even so, antibiotics are often unnecessarily prescribed, and in the long run this contributes to the alarming level of antibiotics resistance. The reason is that there are no good guiding tools for defining the background reason of the infection. One main factor for the clearance of the infection is if there is non-obstructed ventilation from the sinus to the nasal cavity. Gas in Scattering Media Absorption Spectroscopy (GASMAS) has potential for diagnosing this. We have performed a study of frontal sinuses of volunteers with a focus on signal stability and reproducibility over time, accurate oxygen concentration determination, and assessment of gas transport through passages, naturally and after decongestant spray administration. Different from earlier studies on frontal sinuses, water vapor, serving the purpose of oxygen signal normalization, was measured at 818 nm rather than earlier at 937 nm, now closer to the 760 nm oxygen absorption band and thus resulting in more reliable results. In addition, the action of decongestants was objectively demonstrated for the first time. Evaluated oxygen concentration values for left- and right-hand side sinus cavities were found to agree within 0.3%, and a left-right geometrical asymmetry parameter related to anatomical differences was stable within 10%.

Numerous natural materials are porous, contain free gas and are scattering light strongly. Scattering brings about a strong trapping of light and an associated prolonged transit time for photons through a medium. In contrast to the matrix materials, gas enclosures require very narrowband laser radiation for probing. We have in the present study used the gas in scattering media absorption spectroscopy method to study free oxygen in thin (cm) samples utilizing a tunable diode laser, while a pulsed dye laser was employed in corresponding measurements on larger samples, up to the meter scale. Time‐resolved spectroscopy was in both cases used to assess the temporal distribution of the detected photons, mapping the path lengths through the media, which ranged between few centimeters up to 100 m. This study explores the feasibility to extend recent successful monitoring of gases in neonatal infant lungs to the case of larger children or even adults, which could have very important applications, for example, in ventilator setting optimization for severely ill patients, suffering, for example, from SARS‐CoV‐2. The conclusion of our work is that this goal most realistically can be reached by applying intratracheal laser light illumination at the 1 W power level, employing a tapered amplifier, injected with a distributed feedback diode‐laser oscillator output and combined with wavelength‐modulation spectroscopy.

Avocados are considered very healthy due to the high content mono‐unsaturated lipid, essential vitamins and minerals, minimal sugar and no cholesterol and are therefore sometimes referred to as “the perfect fruits”. Avocados, mainly grown in Latin‐America, are harvested unripe and sent overseas. However, the ripening process is very difficult to assess visually and tactilely. A tool for precise noninvasive judgment of the status would be valuable as the fruit is too expensive to be cut open unripe or overdue. A white‐light source and a light‐emitting diode unit with four excitation wavelengths (365, 385, 395, and 405 nm) were used for reflectance and fluorescence spectroscopy in a fiber‐coupled set‐up for noninvasive monitoring. Twelve non‐ripe avocados, with approximately the same size and appearance, were studied and divided into three groups and kept at three different storage conditions; at room temperature, in a refrigerator and a combination of the two. We showed that fluorescence was useful for following the ripening process. A method, which compensates for the spatial variations in spectral properties around a fruit, is described. Remote fluorescence monitoring, intended for orchard use, was also demonstrated. A low‐cost device based on fluorescence for avocado ripeness assessment is proposed.

Advances in optical techniques have provided noninvasive diagnostics and effective means to improve clinical outcomes.^{1 – 3} Fiber-optic probes have been increasingly utilized to provide a minimally invasive approach in tissue characterization for various biomedical applications, such as cancer diagnostics, surgical guidance, and treatment response monitoring.^{4 – 7} Photodynamic therapy (PDT) in conjunction with fiber-optic probing is a promising modality to achieve optimal therapeutic efficiency for cancer treatment.^{8 – 10} PDT is a viable minimally invasive treatment, involving the administration of photosensitizer (PS), incubation time to allow the adequate accumulation of the drug in the tumor, and activation by light of appropriate wavelength. This process results in the generation of highly active oxygen radicals that cause tumor necrosis, apoptosis, and autophagy.^{11 – 13}

The Gas in Scattering Media Absorption Spectroscopy (GASMAS) technique was used to investigate the possible presence of free gas pores in human condyle bones extracted from the tibia in knee revision surgical procedures in response to arthrosis development. Following earlier studies showing free gas presence in femoral head bones, decaying because of inadequate blood flow, we investigated condyle bone, where the arthrosis degeneration process, affecting the cartilage cup, is of different origin. Only a minor gas presence was observed in affected condyle samples, in accordance with our finding for non-arthrosis samples. Further, studies of fresh or initially frozen samples showed very similar signals, suggesting that the handling procedure has only a minor importance in these studies. In contrast to the situation for femoral heads, the monitoring of a gas presence would add only little in assessing the arthrosis status in view of elective surgical procedures.

A joint Chinese-Swedish field campaign of Scheimpflug continuous-wave lidar monitoring of rice-field flying pest insects was pursued in very hot July weather conditions close to Guangzhou, China. The occurrence of insects, birds and bats with almost 200 hours of round-the-clock polarization-sensitive recordings was studied. Wing-beat frequency recordings and depolarization properties were used for target classification. Influence of weather conditions on the flying fauna was also investigated.

Osteonecrosis of the femoral head (ONFH), a recalcitrant and disabling disease, is caused by inadequate or fully disrupted blood supply to the affected segment of the subchondral bone. Theoretically, there will develop gas-filled pores during the bone decay process due to lacking blood supply. Unfortunately, the relationship between the gas-filled pores and ONFH is still unclear. Here, we have introduced diode laser absorption spectroscopy to detect oxygen and water vapor signals in the femoral heads from hip replacement in 19 patients. Five samples are affected by osteoarthritis (OA) and the others are related to ONFH. Oxygen and water vapor signals could be obtained, demonstrating the presence of gas-filled pores in both the OA and ONFH groups while the measurement results showed no significant difference. A study of gas exchange was also performed on one excised bone sample to study how these gas pores communicate with the ambient air. The results suggested that the obtained oxygen signals inside the bone samples originate from the invasion of ambient air, which is not expected in vivo. In conclusion, the ability to detect the gas signal of laser absorption spectroscopy shows the potential for the medical application of assessing the human femoral head in vivo.

Laser spectroscopy provides many possibilities for multi-disciplinary applications in environmental monitoring, in the ecological field, for food safety investigations, and in biomedicine. The paper gives several examples of the power of multi-disciplinary applications of laser spectroscopy as pursued in our research group. The studies utilize mostly similar and widely applicable spectroscopic approaches. Air pollution and vegetation monitoring by lidar techniques, as well as agricultural pest insect monitoring and classification by elastic scattering and fluorescence spectroscopy are described. Biomedical aspects include food safety applications and medical diagnostics of sinusitis and otitis, with strong connection to the abatement of antibiotics resistance development.