Micromachined Oblique Incidence Refleciometry (OIR) Probe for Skin Cancer Detection

We present the design, fabrication and in-vivo testing of a new micromachined probe for skin cancer detection based on oblique incidence reflectometry (OIR). The device miniaturization and fabrication precision provided by micromachining ensure reliable and repeatable high performance of the probe. The developed probe has been tested in a pre-clinical condition. An overall sensitivity of 100% and specificity of 93% haven been achieved in the classification of malignant and benign skin lesions

A novel micro optical probe for early diagnosis of upper gastrointestinal (GI) cancers

In this paper, we present the development of a new micro fiber optical sensor probe with side viewing capability for early diagnosis of cancers in upper gastrointestinal tract. The probe consists of a oblique incidence source and a collection array of microfabricated curved SU-8 waveguides for collecting spatially resolved diffuse reflectance from tissue surface. The probe has been used to measure ex-vivo esophagus specimens to differentiate cancerous tissues from benign ones

Micromachined “side-viewing” optical sensor probe for detection of esophageal cancers

In this paper, we report the design, fabrication and testing of a new miniaturized optical sensor probe with “side viewing” capability for oblique incidence diffuse reflectance spectrometry. The sensor probe consists of a lithographically patterned polymer waveguides chip and two micromachined positioning substrates and source/collection fibers to achieve 45° light incidence and collection of spatially resolved diffuse reflectance. Diffuse reflectance of human esophageal surface has been successfully measured for differentiation of cancerous tissues from normal ones

Photoacoustic tomography through a whole adult human skull with a photon recycler

Photoacoustic tomography (PAT) of the human brain is challenging due to the fact that the skull strongly absorbs and scatters light, and attenuates and distorts ultrasound as well. For the first time, we demonstrated the feasibility of PAT through a whole adult human skull. A photon recycler (PR) was built to increase light transmittance through the skull. Both a graphite target and a canine brain were imaged through the skull. Use of the PR was found to improve the photoacoustic signal-to-noise ratio by a factor of 2.4. In addition, subtraction of photoacoustic signals that arise from light absorption within the skull significantly improved the contrast of the target. Our results indicate that PAT can potentially be applied to in vivo human brain imaging

Iterative image reconstruction in elastic inhomogenous media with application to transcranial photoacoustic tomography

Photoacoustic computed tomography (PACT) is an emerging computed imaging modality that exploits optical contrast and ultrasonic detection principles to form images of the photoacoustically induced initial pressure distribution within tissue. The PACT reconstruction problem corresponds to a time-domain inverse source problem, where the initial pressure distribution is recovered from the measurements recorded on an aperture outside the support of the source. A major challenge in transcranial PACT brain imaging is to compensate for aberrations in the measured data due to the propagation of the photoacoustic wavefields through the skull. To properly account for these effects, a wave equation-based inversion method should be employed that can model the heterogeneous elastic properties of the medium. In this study, an iterative image reconstruction method for 3D transcranial PACT is developed based on the elastic wave equation. To accomplish this, a forward model based on a finite-difference time-domain discretization of the elastic wave equation is established. Subsequently, gradient-based methods are employed for computing penalized least squares estimates of the initial source distribution that produced the measured photoacoustic data. The developed reconstruction algorithm is validated and investigated through computer-simulation studies

A Forward-Adjoint Operator Pair Based on the Elastic Wave Equation for Use in Transcranial Photoacoustic Computed Tomography

Photoacoustic computed tomography (PACT) is an emerging imaging modality that exploits optical contrast and ultrasonic detection principles to form images of the photoacoustically induced initial pressure distribution within tissue. The PACT reconstruction problem corresponds to an inverse source problem in which the initial pressure distribution is recovered from measurements of the radiated wavefield. A major challenge in transcranial PACT brain imaging is compensation for aberrations in the measured data due to the presence of the skull. Ultrasonic waves undergo absorption, scattering, and longitudinal-to-shear wave mode conversion as they propagate through the skull. To properly account for these effects, a wave-equation-based inversion method should be employed that can model the heterogeneous elastic properties of the skull. In this work, a forward model based on a finite-difference time-domain discretization of the three-dimensional elastic wave equation is established and a procedure for computing the corresponding adjoint of the forward operator is presented. Massively parallel implementations of these operators employing multiple graphics processing units are also developed. The developed numerical framework is validated and investigated in computer-simulation and experimental phantom studies whose designs are motivated by transcranial PACT applications

Label-free photoacoustic tomography of whole mouse brain structures ex vivo

Capitalizing on endogenous hemoglobin contrast, photoacoustic-computed tomography (PACT), a deep-tissue high-resolution imaging modality, has drawn increasing interest in neuroimaging. However, most existing studies are limited to functional imaging on the cortical surface and the deep brain structural imaging capability of PACT has never been demonstrated. Here, we explicitly studied the limiting factors of deep brain PACT imaging. We found that the skull distorted the acoustic signal and blood suppressed the structural contrast from other chromophores. When the two effects are mitigated, PACT can potentially provide high-resolution label-free imaging of structures in the entire mouse brain. With 100-μm in-plane resolution, we can clearly identify major structures of the brain, which complements magnetic resonance microscopy for imaging small-animal brain structures. Spectral PACT studies indicate that structural contrasts mainly originate from cytochrome distribution and that the presence of lipid sharpens the image contrast; brain histology results provide further validation. The feasibility of imaging the structure of the brain in vivo is also discussed. Our results demonstrate that PACT is a promising modality for both structural and functional brain imaging

Inguinal plasty and appendectomy as treatment for Amyand's hernia: case report and literature review

Amyand's hernia is described as the presence of the caecal appendix within the hernial sac of an incarcerated inguinal hernia. It was reported as an incidental finding in 1% of cases and with evidence of appendicitis in 0.1% of cases. The approach involves performing appendectomy and inguinal repair in the same surgical time, depending on the clinical scenario and the surgeon's decisions. We presented the case of a 76-year-old male patient with a diagnosis of Amyand's right inguinal hernia diagnosed during trans-operative right inguinal plasty