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Optoacoustic signal measured in the reflection mode from a VLBW premature infant (1,020 g) using the medical grade optoacoustic system.
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Premature, very-low-birth-weight (VLBW; ≤1500 g) and low-birth-weight (LBW; 1500-2499 g) infants are at increased risk for severe neurological disability. 25-50% of the 63,000 VLBW infants born annually in the USA have major longterm cognitive or neurobehavioral deficits in which cerebral hypoxia plays an important role. At present, no technology i...
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Context 1
... optoacoustic signal from the SSS and the overlying tissues obtained in the reflection mode through the open fontanelle with the medical-grade optoacoustic system from a VLBW infant (1,020 g) is presented in Fig. 1. The first peak in the optoacoustic signal (at t = 0 s) was induced in the skin and hair. The second peak (at time = 1.6 µs) was induced in the SSS. The depth from the skin surface is shown in the upper X-axis and was calculated by multiplying the time scale (the lower X-axis) by the speed of sound in soft tissue (1.5 mm/µs). The SSS ...
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Citations
... Various technologies emerged in recent years to determine tissue oxygen consumption in different skin areas of a body (both human and animal); these include the use of pressure oxygen tension technique, opto-acoustic system [5], non-invasive Positron Emission Tomography (PET) [6][7], spectroscopy approach [8][9] and a hybrid of aforementioned approaches [10]. Among these techniques optical spectroscopy is a widely adopted approach that has attracted increasing attention owing to the system's inherent flexibility, cost efficiency and simplicity for use. ...
p> This paper presented the use of a three-wavelength system coupled with a prediction-correction model for the measurement of a person’s tissue oxygen levels and in the efforts towards the development of a field-portable system. This study considered light wavelength of market-available emitters in the range 500 − 650 nm for its practical implementation. This approach required the use of light attenuation and hemoglobin absorptivity information of three different wavelengths in determining tissue oxygen saturation value, StO2. It was found through the analysis of results using Monte Carlo method that considerable improvement in the accuracy of the predictions was obtained using the corrective models (ρ =0.874). The low mean prediction errors of similar magnitude, not exceeding 4 %, given by two wavelength combinations 538, 560, 633 nm and 538, 560, 650 nm were observed for signals with signal-noise ratio (SNR) of down to 30 dB. A significant statistical difference was found between the prediction errors and the wavelength combination used under this noise condition (ρ =0.011). This work concluded that the findings of this study provide insights into technology implementation of skin oximetry and the possible impacts it might have in medical arena. </p
... Our initial neonatal studies were performed with a medical-grade optoacoustic system 14,15,24 which is based on optical parametric oscillator (OPO), the Opolette HE 532 (Opotek Inc., Carlsbad, CA) operating in the wavelength range of 680-950 nm with a pulse duration and repetition rate of 6 ns and 20 Hz, respectively. In this study we used the multi- wavelength, fiber-coupled, high-power, compact laser diode system developed for optoacoustic monitoring, imaging, and sensing 15 . ...
... We developed fast acquisition and processing software which in combination with the high pulse repetition rate provides patient monitoring with less motion artifacts compared to the OPO-based optoacoustic systems. For cerebral oxygenation measurements in reflection and transmission modes we built wide-band, highly-sensitive optoacoustic probes 14,15,24 . The laser diode system provides both single measurements and continuous monitoring of SSS blood oxygenation in both modes. ...
... We used in adult studies a medical-grade optoacoustic system, described in our previous publications [26][27][28][29][32][33][34][35] . An optical parametric oscillator (OPO), the Opolette HE 532 (Opotek Inc., Carlsbad, CA), is used in the system as a source of pulsed near-IR light in the wavelength range of 680-950 nm with a pulse duration of about 6 ns and repetition rate of 20 Hz. ...
... For detection of optoacoustic signals with high SNR, we developed sensitive, wide-band, optoacoustic probes for monitoring, imaging, and sensing in the reflection and transmission modes [22][23][24][25][26][27][28][29][30][31][32][33][34][35] . In the transmission (forward) mode, light delivery and detection of optoacoustic signals are performed from opposite hemispheres (typically in the range of irradiation-detection angles from 120 o to 240 o ), while in the reflection (backward) mode light delivery and detection of optoacoustic signals are performed from the same hemisphere. ...
... We proposed to use optoacoustic methods and systems for noninvasive cerebral hypoxia monitoring in neonates by probing the superior sagittal sinus (SSS) in the reflection and transmission modes through the open anterior or posterior fontanelles as well as through the skull bone [16][17][18] . The SSS, a large central cerebral vein, represents an important site of monitoring because it drains all blood from the brain. ...
... The SSS, a large central cerebral vein, represents an important site of monitoring because it drains all blood from the brain. These transcranial methods and systems can also be used for optoacoustic brain imaging, tomography, sensing in neonates, children, and adults [16][17][18] . The optoacoustic technique combines the advantages of both optical (high contrast) and ultrasound (high resolution) techniques. ...
... Our first studies in neonates were performed with a medical-grade optoacoustic system [16][17][18] which utilizes an optical parametric oscillator (OPO), the Opolette HE 532 (Opotek Inc., Carlsbad, CA), as a source of pulsed nearinfrared light in the wavelength range of 680-950 nm with a pulse width of about 6 ns and repetition rate of 20 Hz. Based on results obtained with the OPO system, we developed and built a multi-wavelength, fiber-coupled, high-power, compact laser diode system for optoacoustic monitoring, imaging, and sensing 18 . ...
We proposed to use transmission (forward) mode for cerebral, noninvasive, transcranial optoacoustic monitoring, imaging, and sensing in humans. In the transmission mode, the irradiation of the tissue of interest and detection of optoacoustic signals are performed from opposite hemispheres, while in the reflection (backward) mode the irradiation of the tissue of interest and detection of optoacoustic signals are performed from the same hemisphere. Recently, we developed new, transmission-mode optoacoustic probes for patients with traumatic brain injury (TBI) and for neonatal patients. The transmission mode probes have two major parts: a fiber-optic delivery system and an acoustic transducer (sensor). To obtain optoacoustic signals in the transmission mode, in this study we placed the sensor on the forehead, while light was delivered to the opposite side of the head. Using a medical grade, multi-wavelength, OPObased optoacoustic system tunable in the near infrared spectral range (680-950 nm) and a novel, compact, fiber-coupled, multi-wavelength, pulsed laser diode-based system, we recorded optoacoustic signals generated in the posterior part of the head of adults with TBI and neonates. The optoacoustic signals had two distinct peaks: the first peak from the intracranial space and the second peak from the scalp. The first peak generated by cerebral blood was used to measure cerebral blood oxygenation. Moreover, the transmission mode measurements provided detection of intracranial hematomas in the TBI patients. The obtained results suggest that the transmission mode can be used for optoacoustic brain imaging, tomography, and mapping in humans.
Adequate oxygenation is essential for normal embryogenesis and fetal growth. Perturbations in the intrauterine oxidative environment during pregnancy are associated with several pathophysiological disorders such as pregnancy loss, preeclampsia, and intrauterine growth restriction. We proposed to use optoacoustic technology for monitoring placental and fetal umbilical blood oxygenation. In this work, we studied optoacoustic monitoring of oxygenation in placenta and umbilical cord blood ex vivo using technique of placenta perfusion. We used a medical grade, nearinfrared, tunable, optoacoustic system developed and built for oxygenation monitoring in blood vessels and in tissues. First, we calibrated the system for cord blood oxygenation measurements by using a CO-Oximeter (gold standard). Then we performed validation in cord blood circulating through the catheters localized on the fetal side of an isolated placental lobule. Finally, the oxygenation measurements were performed in the perfused placental tissue. To increase or decrease blood oxygenation, we used infusion of a gas mixture of 95% O2 + 5% CO2 and 95% N2 + 5% CO2, respectively. In placental tissue, up to four cycles of changes in oxygenation were performed. The optoacoustically measured oxygenation in circulating cord blood and in placental lobule closely correlated with the actual oxygenation data measured by CO-Oximeter. We plan to further test the placental and cord blood oxygenation monitoring with optoacoustics in animal and clinical studies.
Photoacoustic imaging (PAI), providing the unique contrast of optical absorption and the superb scalability of spatial resolution and penetration, has emerged as an enabling technique in both basic and translational brain research. In this paper, first, mechanisms behind neuro-PAI of endogenous absorber-encoded functional information (e.g., the concentration of hemoglobin, the oxygen saturation of hemoglobin, blood flow, oxygen metabolism, and water accumulation) and exogenous probe-labeled molecular targets (e.g., neural activity, glucose uptake, aberrant protein aggregation, and malignancy) are introduced. Then, two technical innovations-functional connectivity photoacoustic tomography and high-speed functional photoacoustic microscopy-for spatio-temporal interrogation of the brain at resting and activated states are highlighted, and two application niches in vascular cognitive impairment and brain cancer are discussed. Finally, the prospect of neuro-PAI is envisioned.
