The objective of the present work is to evaluate feasibility of deploying a High-Density Diffuse Optical Tomography (HD-DOT) instrument to a field setting to measure the effects of early life stressors on brain development. This goal was accomplished by imaging a cohort of typical and malnourished children in Cali, Colombia. Feasibility of performing brain imaging in this population using HD-DOT was assessed by replicating known brain responses during both tasks and rest.
A total of 22 participants were enrolled in the study (10 male; average age 107.2 months; age range 97-118 months). Participants completed a passive word listening task, and participants were also imaged as they rested quietly for 5 minutes while viewing a movie. Data acquisition was performed using a custom field-ready HD-DOT system with a small footprint optimized for field use. This continuous-wave system consisted of a 30 source by 48 detector array, (S-D separations of 1.3, 2.9, and 3.9 cm; first through third nearest neighbor measurements), sampled at a 10 Hz frame rate. Sources consisted of LEDs illuminating at 750 and 850 nm.
The passive word listening task revealed activations in the superior temporal gyrus, demonstrating sufficient data quality and sensitivity to known auditory language processing regions. Functional connectivity (FC) was measured using data collected during passive movie viewing and reveals sensitivity to at least two previously published functional networks. The results of this work confirm feasibility of performing neuroimaging in low-resource settings with HD-DOT. Future work will identify differences in brain function between the two populations.
During 2007, the Universidad del Valle Student Chapter presented a proposal for developing an educational outreach
activity for children from an underprivileged zone to the Optical Society of America Foundation (OSAF) and to SPIE.
The activity was carried out jointly by OSA and SPIE Universidad del Valle Student Chapters in the hillsides of
Santiago de Cali, in a zone known as "Pueblo Joven" during 2008. It was aimed to boys and girls with ages between 8
and 13 years and was called "Experience the magic of light and color". The main purpose was to bring the children some
basic concepts on optics and to encourage them to explore science through optics. The Universidad del Valle Student
Chapters designed a series of talks and practical workshops where children participated in hands-on experiments that
easily explain the fundamental concepts of light phenomena. Afterwards the children presented their achievements in a
small science fair offered to the community and tried to explain in their own words what they learned and built. In this
work, we present the most successful experimental designs and the educational standards we tried to develop with this
Laser light propagation in soft tissues is important because of the growing biomedical applications of lasers and the need
to optically characterize the biological media. Following previous developments of the group, we have developed low
cost models, Phantoms, of soft tissue. The process was developed in a clean room to avoid the medium contamination.
Each model was characterized by measuring the refractive index, and spectral reflectance and transmittance. To study
the laser light propagation, each model was illuminated with a clean beam of laser light, using sources such as He-Ne
(632nm) and DPSSL (473 nm). Laterally scattered light was imaged and these images were digitally processed. We
analyzed the intensity distribution of the scattered radiation in order to obtain details of the beam evolution in the
medium. Line profiles taken from the intensity distribution surface allow measuring the beam spread, and to find
expressions for the longitudinal (along the beam incident direction) and transversal (across the beam incident direction)
intensities distributions. From these behaviors, the radiation penetration depth and the total coefficient of extinction have
been determined. The multiple scattering effects were remarkable, especially for the low wavelength laser beam.
To determine the coherence of a laser device, the concept of visibility is used and applied to the measured interference patterns produced by this laser light in a specific interferometer. In this case, to determine the coherence of a Diode Pumped Solid State Nd -YAG Laser, a digital image processing procedure was developed and applied to the fringe patterns obtained with a rigid arm Michelson interferometer array in order to obtain the coherence function. A spatial filtered laser beam was used to illuminate the interferometer and to produce a circular fringe pattern. The interference pattern was captured on a spatial calibrated translucent screen and photographed by a digital camera. Afterwards, the images were digitally processed to calibrate the pixel distribution and to produce an intensity function from this calibrated image. Data processing of the intensity function values allows to produce the coherence function and to evaluate the coherence degree of the radiation. The interference patterns, intensity distributions and the coherence calculations of the Nd - YAG laser are presented.