Moshe Ben-David

A new thermography-based approach to early detection of cancer utilizing magnetic nanoparticles theory simulation and in vitro validation

This work describes the utilization of tumor-specific magnetic nanoparticles together with an alternating magnetic field as a means to thermally mark a tumor so as to detect it using a thermal imaging system. Experiments were conducted using an in vitro tissue model, an inductive heating system, and an infrared camera. The thermal images, recorded by the infrared camera during the experiments, were analyzed using an algorithm that was developed as part of this work. The results show that small tumor phantoms (diameter of 0.5 mm) that were embedded under the surface of the tissue phantom (up to 14 mm below the surface) can be detected and located, indicating that the proposed method could potentially offer considerable advantages over conventional thermography and other methods for cancer early detection. Nevertheless, several issues should be clarified in future studies before the method can be offered for clinical use.

Broad band and low loss mid-IR flexible hollow waveguides

This paper introduces a deposition method to create a multilayered waveguide with alternating layers of high index of refraction contrast. A very thin Ag layer, practically transparent in the mid-IR radiation wavelengths of CO(2) and Er-YAG lasers, was created. This enabled a good contrast of the indices of refraction of silver/silver iodide. Theoretical calculations as well as experiments have shown that transmission was higher at these wavelengths for two pair layers, in comparison to one pair of silver/silver iodide. Windows of transmittance and small sensitivity to bending were demonstrated for those two pair layer waveguides. This method could be extended to an increased number of pairs to configure a true photonic band gap waveguide.

Coherent hollow-core waveguide bundles for thermal imaging

There has been very little work done in the past to extend the wavelength range of fiber image bundles to the IR range. This is due, in part, to the lack of IR transmissive fibers with optical and mechanical properties analogous to the oxide glass fibers currently employed in the visible fiber bundles. Our research is aimed at developing high-resolution hollow-core coherent IR fiber bundles for transendoscopic infrared imaging. We employ the hollow glass waveguide (HGW) technology that was used successfully to make single-HGWs with Ag/AgI thin film coatings to form coherent bundles for IR imaging. We examine the possibility of developing endoscopic systems to capture thermal images using hollow waveguide fiber bundles adjusted to the 8-10?mum spectral range and investigate the applicability of such systems. We carried out a series of measurements in order to characterize the optical properties of the fiber bundles. These included the attenuation, resolution, and temperature response. We developed theoretical models and simulation tools that calculate the light propagation through HGW bundles, and which can be used to calculate the optical properties of the fiber bundles. Finally, the HGW fiber bundles were used to transmit thermal images of various heated objects; the results were compared with simulation results. The experimental results are encouraging, show an improvement in the resolution and thermal response of the HGW fiber bundles, and are consistent with the theoretical results. Nonetheless, additional improvements in the attenuation of the bundles are required in order to be able to use this technology for medical applications.

Measuring tissue heat penetration by scattered light measurements

The monitoring of tissue morphological changes during clinical procedure such as laser thermotherapy, laser hair removal and others is important in order to prevent damage to healthy tissue. An optical system and method for the assessment of real time in vivo tissue morphological changes is proposed.

Optical Fibers for Biomedical Applications

The optical fibers are making new inroads into the biomedical applications. Absorption spectroscopy can be performed in situ. In situ studies are conducted for several applications—glucose and other blood analyte analysis, and NO and CO 2 measurements in breath and molecular tissue mapping. Quick and accurate measurements of blood analytes without sample preparation may enable a better treatment. Gas analysis of human breath may provide valuable biomedical and clinical information. The detection of gas traces such as ammonia and NO may be used for noninvasive medical diagnosis and monitoring the success of a medical treatment. Near infrared (NIR) and mid-IR (MIDIR) spectroscopy is a reliable method for obtaining the fingerprint of solids, liquids, and gases. It can detect small amounts of materials and quantify the amount of material inside a given sample. One of the methods of NIR and MIDIR spectroscopy is evanescent wave spectroscopy (EWS), which is also known as attenuated total reflectance spectroscopy.

A new method for tumor detection using induced acoustic waves from tagged magnetic nanoparticles

UNLABELLED Magnetoacoustic detection is a new method for the noninvasive, early detection of cancer. It uses specific superparamagnetic nanoparticles (NPs) that bind to tumor sites together with magnetic excitation and acoustic detection of the tumor-NPs complex. This work tests the feasibility of such method theoretically and experimentally. An extensive analytic model has been developed that shows an ability to detect small tumors, a few centimeters deep inside the tissue. A series of experiments were conducted to validate the theoretical model. The performance of specially designed solenoids was measured, and the detection of the tumor presence in phantom was demonstrated. Experimental results agree well with the theoretical calculations, providing preliminary proof of concept. We demonstrate the ability to detect a 5-mm diameter spherical tumor located 3 cm deep. Instrumentation and measurements are inexpensive and accurate. The accuracy, speed, and costs of this method show the potential for early detection of cancer. FROM THE CLINICAL EDITOR A sensitive and cost effective magentoacoustic tumor detection method is presented in this paper using superparamagnetic nanoparticles. The method is demonstrated in a phantom by detecting a 5-mm diameter spherical tumor located 3 cm deep.

Fluorescence Lifetime and Depth Estimation of a Tumor Site for Functional Imaging Purposes

Cancerous cells have irregular environmental conditions, such as temperature and pH, which distinguish them from their surroundings. Fluorescence lifetime imaging using near-IR (NIR) fluorescent probes, whose lifetime value is sensitive to pH and temperature, enables the estimation of these values, and provides functional information about the tumor. The lifetime value, extracted from the time-resolved intensity decay curve, combines the photon time delays, caused by the photon time of flight, and the intrinsic lifetime in which we are interested. In this study, we present a model, based on the diffusion approximation of the radiation transport equation, for extracting both the depth of an NIR fluorescent probe, and its intrinsic lifetime value, from a fluorescence time decay curve. The model was validated for different inclusion depths, fluorescent lifetime values, and scattering coefficients using a time-resolved Monte Carlo simulation. Our reported results are the first step toward performing functional imaging using fluorescence lifetime in vivo measurements.

An Alternative Approach to Analyze Fluorescence Lifetime Images as a Base for a Tumor Early Diagnosis System

Fluorescence lifetime imaging is a very promising imaging method for early detection of malignant tumors. It offers many advantages over conventional fluorescence methods, especially because the acquired signal does not rely on the fluorophore concentration in the tissue. As in all imaging method, the goal is to determine the exact location of a malignant tumor. However, since we are dealing with optical imaging, the inverse problem, i.e., extracting the tumor location coordinates is not an easy task to fulfill. In this paper, we describe an alternative method of interpreting the fluorescence lifetime image. The method extracts four features from each decay curve. We show that from these features one can extract the location of the tumor. The theoretical model is compared to the experimental results obtained from tissue-like phantoms.

The Role of Skew Rays in Biomedical Sensing

Hollow core waveguides are useful tools in biomedical optics both for transmission of radiation to the tissue to perform intervention and to sensing tissue optical parameters for diagnostics. These waveguides can also be used as an interaction chamber for sensing the presence and concentration of different aerosols and gases. To support the design and analyzing of such a device, we developed a computerized, ray tracing simulation. As aerosol particles tend to aggregate near the waveguides wall, the role of skew rays (i.e., rays that follow a helical path inside the waveguide) is investigated here and compared with merdional rays, which “zig-zag” through the optical axis. To test quantitatively the sensing quality of different types of beam, a measure for the beam-sensing quality is developed. As first step, the validation of the simulation results is presented. Then, a compression between the sensing quality of Guassian, ring-like, and Bessel beam is made. These results allow the optimization of ray coupling to a hollow core waveguide-based, aerosol-sensing devices.

Hollow corewaveguides for radiation delivery and sensing: Monte Carlo, ray tracing computer simulation

The use hollow core waveguides (HCWs) in biomedicine includes two different tasks: Power delivery in order to facilitate clinical procedures and measurement of beam parameters in order to sense the surrounding tissue and create a diagnosis. To study the interaction between light and waveguide a computer simulation of ray propagation inside a HCW was developed. The simulation is based on the statistical method of Monte Carlo repeated trials and of ray tracing optics. The simulation accounts for both meridional and skew rays, rough fiber surface, Imperfect reflection, arbitrary fiber geometry and the insertion of absorbing molecular clusters inside the fiber lumen for sensing purposes. Here we test skew rays. At first the effect of skewness on the number of wall hits and the optical distance is investigated. Then different beam profiles are tested to fulfill different tasks: Sensing and power delivery. The role of skew rays in each scenario is discussed.