<i>In vivo</i> physiological sensing is typically done either by imaging thin tissues or by examining changes in the attenuation coefficient. One known technique for thin tissue <i>in vivo</i> applications is the optical coherence tomography (OCT). However, deep tissue methods are usually based on diffusion reflection (DR), which correlates the optical properties to the reflected light intensity. The attenuation coefficient is composed of tissue absorption and scattering. We present a noninvasive nanophotonics technique, the iterative multi-plane optical property extraction (IMOPE) for extracting the scattering properties from a turbid medium. The reflectance-based IMOPE is most relevant for <i>in vivo</i> applications, hence, in this research we suggest a new theoretical description of phase accumulation in deep tissue, which is rarely mentioned in the literature, using a modified DR theory that represents the phase based on the effective pathlength. The IMOPE records multiple intensity images, reconstructs the phase using Gerchberg-Saxton (GS) algorithm. This algorithm is usually being used for beam shaping or phase reconstruction. We propose to calculate the phase second order moment to estimate the scattering. IMOPE experiments were conducted with tissue-like phantoms for calibration purposes, as well as <i>ex vivo</i> and <i>in vivo</i> measurement. The suggested technique was applied both in transmission and reflection mode. The transmission based IMOPE detected organic nanoparticles within tissues and the quantitative signature of milk components. The reflectance-based IMOPE was applied for tissue viability test and <i>in vivo</i> gold nanorods and blood flow detection.
Extracting optical parameters of turbid medium (e.g. tissue) by light reflectance signals is of great interest and has many applications in the medical world, life science, material analysis and biomedical optics. The reemitted light from an irradiated tissue is affected by the light's interaction with the tissue components and contains the information about the tissue structure and physiological state. In this research we present a novel noninvasive nanophotonics technique, i.e., iterative multi-plane optical property extraction (IMOPE) based on reflectance measurements. The reflectance based IMOPE was applied for tissue viability examination, detection of gold nanorods (GNRs) within the blood circulation as well as blood flow detection using the GNRs presence within the blood vessels. The basics of the IMOPE combine a simple experimental setup for recording light intensity images with an iterative Gerchberg–Saxton (G-S) algorithm for reconstructing the reflected light phase and computing its standard deviation (STD). Changes in tissue composition affect its optical properties which results in changes in the light phase that can be measured by its STD. This work presents reflectance based IMOPE tissue viability examination, producing a decrease in the computed STD for older tissues, as well as investigating their organic material absorption capability. Finally, differentiation of the femoral vein from adjacent tissues using GNRs and the detection of their presence within blood circulation and tissues are also presented with high sensitivity (better than computed tomography) to low quantities of GNRs (<3 mg).
Various techniques for recovering optical parameters were developed over the years. However each has its limitations, constraints and disadvantages (e.g. accuracy, computational speed, sample assembly, distinguishing between the different parameters, etc.). This research suggests an optical technique for extracting the reduced scattering coefficient (μs') of substances by examining the light transmission through or reflection from them. It uses the multiple planes Gerchberg- Saxton (G-S) algorithm to reconstruct the light phase created by the substance. At the end of the algorithm, μs' can be estimated from the standard deviation (STD) of the retrieved phase of the reemitted light. We will use the theory to compute the phase’s STD that directly correlated to the optical properties of different substances. Two possible applications for this technique, out of many others, are nanoparticles (NPs) penetration depth determination, for promoting topical medications, and detection of milk components quantitative signature as <i>en route </i>to milk content monitoring tool. For the former application, three materials were fabricated into NPs and all presented an activity enhancement with their size reduction. Then the NPs were applied on tissues and detected by our technique. For the latter, different milk content concentrations were examined resulting with different STD values suggesting it can be used as indicator for the milk component concentrations.
In recent years, infiltrating materials into the human body has become a great challenge many researches are facing. In medicine and cosmetics today, there are materials which are administrated to patients by injection only. The main challenge with topical medication is penetrating the skin barrier. The skin is an effective barrier between the body and the outside environment, which prevents foreign materials entering the body easily. However, reducing the size of the desired materials might help their skin penetration ability. Recently nanoparticles (NPs) are being evaluated for use in many fields like chemistry, biology, medicine, physics and optics. The technique used in this work for forming organic NPs (ONPs) is the application of sonic waves to an aqueous solution, known as sonochemistry. To investigate the physical penetration depth of ONPs into the human body, we first developed a novel optical technique for detecting NPs within tissues. The detection of NPs is done by the extraction and investigation of the reemitted light phase.