Incorporation of an ultrasound and model guided permissible region improves quantitative source recovery in bioluminescence tomography

Bioluminescence imaging has shown great potential for studying and monitoring disease progression in small animal pre-clinical imaging. However, absolute bioluminescence source recovery through tomographic multi-wavelength measurements is often hindered through the lack of quantitative accuracy and suffers from both poor localisation and quantitative recovery. In this work a method to incorporate a permissible region strategy through not only a priori location (permissible region) but also based on a model of light propagation and hence light sensitivity is developed and tested using both simulations and experimental data. Reconstructions on two different numerical models (a simple slab, and the digital version of a heterogeneous mouse) show an improvement of localisation and recovery of intensity (around 25% for the slab model and around 10% for the digital mouse model). This strategy is also used with experimental data from a phantom gel, which demonstrated an improved recovered tomographic image

Ultrasound-mediation of self-illuminating reporters improves imaging resolution in optically scattering media

In vivo imaging of self-illuminating bio-and chemiluminescent reporters is used to observe the physiology of small animals. However, strong light scattering by biological tissues results in poor spatial resolution of the optical imaging, which also degrades the quantitative accuracy. To overcome this challenging problem, focused ultrasound is used to modulate the light from the reporter at the ultrasound frequency. This produces an ultrasound switchable light ‘beacon’ that reduces the influence of light scattering in order to improve spatial resolution. The experimental results demonstrate that apart from light modulation at the ultrasound frequency (AC signal at 3.5 MHz), ultrasound also increases the DC intensity of the reporters. This is shown to be due to a temperature rise caused by insonification that was minimized to be within acceptable mammalian tissue safety thresholds by adjusting the duty cycle of the ultrasound. Line scans of bio-and chemiluminescent objects embedded within a scattering medium were obtained using ultrasound modulated (AC) and ultrasound enhanced (DC) signals. Lateral resolution is improved by a factor of 12 and 7 respectively, as compared to conventional CCD imaging. Two chemiluminescent sources separated by ~10mm at ~20 mm deep inside a 50 mm thick chicken breast have been successfully resolved with an average signal-to-noise ratio of approximately 8-10 dB

Theoretical modelling of modulation depth of acoustic optical imaging at varying mechanical properties

The signal from acousto-optical imaging is affected by the mechanical properties of a sample. A theoretical model showed that speed of sound, density, peizooptical coefficient, and acoustic amplitude affect modulation depth

Modelling light propagation for fetal monitoring in utero

About one in three births in the United States is through Cesarean section. Current monitoring techniques are insufficient to determine hypoxia and acidosis in the fetus during labor. An FDA approved transvaginal fetal pulse oximeter has been used in clinical trials to show that the device can help decrease the rate of Cesarean section. However, this technique has not been adapted into normal hospital procedure. Past pre-clinical and clinical studies have shown the feasibility of transabdominal fetal pulse oximetry. To understand the fundamentals of transabominal fetal pulse oximetry, we examined a layer model with both Monte Carlo and NIRFAST simulations. The NIRFAST model was used to model concentric spheres to understand the effect on geometry. The simulations were used in order to determine how much optical power can be detected from the fetus with a light source at 850 nm. The signal decreased as the fetal depth increased and as source-detector distance increased. The results can be used to aid in the design of a transabdominal fetal pulse oximeter

Modelling iterative optical phase conjugation through random media

A 2D modelling study is presented on the transmission enhancement by iterative optical phase conjugation through diffusive random media. Factors affecting coherent control for enhancing the total transmission is discussed

Effect of the presence of amniotic fluid for optical transabdominal fetal monitoring using Monte Carlo simulations

About a third of babies are delivered by Cesarean section. There has been an increase in maternal deaths during labor due to complications with subsequent births after a C-section. Therefore, there is a clinical motivation to reduce the C-section rate. Current techniques are, however, inefficient at determining fetal distress leading to a high false positive rate for complications and ultimately a C-section. For the current study, Monte Carlo simulations were used to calculate the amount of signal received on a model of a pregnant mother, as well as, the percent of the signal that comes from the fetal layer. Models with and without a 1 mm amniotic fluid were compared and showed differing trends

Biophotonics computer app: fostering multidisciplinary distance self-paced learning with a user-friendly interface

The biophotonics app enables multidisciplinary and self-paced learning in both in-person or virtual environments. The app can work offline and has a user-friendly interface well accepted by students. App instructions are publicly available

Ultrasound-mediation of self-illuminating reporters improves imaging resolution in optically scattering media

In vivo imaging of self-illuminating bio-and chemiluminescent reporters is used to observe the physiology of small animals. However, strong light scattering by biological tissues results in poor spatial resolution of the optical imaging, which also degrades the quantitative accuracy. To overcome this challenging problem, focused ultrasound is used to modulate the light from the reporter at the ultrasound frequency. This produces an ultrasound switchable light ‘beacon’ that reduces the influence of light scattering in order to improve spatial resolution. The experimental results demonstrate that apart from light modulation at the ultrasound frequency (AC signal at 3.5 MHz), ultrasound also increases the DC intensity of the reporters. This is shown to be due to a temperature rise caused by insonification that was minimized to be within acceptable mammalian tissue safety thresholds by adjusting the duty cycle of the ultrasound. Line scans of bio-and chemiluminescent objects embedded within a scattering medium were obtained using ultrasound modulated (AC) and ultrasound enhanced (DC) signals. Lateral resolution is improved by a factor of 12 and 7 respectively, as compared to conventional CCD imaging. Two chemiluminescent sources separated by ~10mm at ~20 mm deep inside a 50 mm thick chicken breast have been successfully resolved with an average signal-to-noise ratio of approximately 8-10 dB

Biophotonics box: educational kit for multidisciplinary outreach activities in optics and photonics

The biophotonics box enables multidisciplinary/interdisciplinary and self-paced learning with at-home experiments using low-resource components. Experiments can increase the interest of students in STEM subjects by emphasizing the real-life applications in biology and medicine

Online learning combining virtual lectures, at-home experiments and computer simulations: a multidisciplinary teaching and learning approach

We developed a fully-remote biophotonics workshop integrating webinars, computer simulations and at-home experiments to meet the needs of undergraduate students with diverse backgrounds and learning styles. Similar strategies/resources could be used in multidisciplinary programs