Tissue-like Phantoms Research Articles

Fast and sensitive diffuse correlation spectroscopy with highly parallelized single photon detection

Diffuse correlation spectroscopy (DCS) is a well-established method that measures rapid changes in scattered coherent light to identify blood flow and functional dynamics within a tissue. While its sensitivity to minute scatterer displacements leads to a number of unique advantages, conventional DCS systems become photon-limited when attempting to probe deep into the tissue, which leads to long measurement windows (∽1 sec). Here, we present a high-sensitivity DCS system with 1024 parallel detection channels integrated within a single-photon avalanche diode array and demonstrate the ability to detect mm-scale perturbations up to 1 cm deep within a tissue-like phantom at up to a 33 Hz sampling rate. We also show that this highly parallelized strategy can measure the human pulse at high fidelity and detect behaviorally induced physiological variations from above the human prefrontal cortex. By greatly improving the detection sensitivity and speed, highly parallelized DCS opens up new experiments for high-speed biological signal measurement.

Gold nanoclusters performing as contrast agents for non-invasive imaging of tissue-like phantoms via two-photon excited fluorescence lifetime imaging.

Recently, gold nanoclusters (AuNCs) have received considerable scientific interest due to their ability to generate intrinsic photoluminescence (PL), making them suitable for a wide range of applications, such as sensing, biolabeling and bioimaging. Fluorescence lifetime imaging microscopy (FLIM) is an extremely promising technique when it comes to tissue imaging, especially once combined with near-infrared two-photon excitation (TPE) due to deep tissue penetration and improved spatial resolution. In this paper, we carried out an innovative study on the ability of bovine serum albumin stabilized gold nanoclusters (BSA-AuNCs) to perform as reliable label-free contrast agents for the visualization of tissue-like agarose phantoms via TPE-FLIM. We prove that BSA-AuNCs exhibit uniform and reproducible TPE PL in the first biological window, when embedded in phantoms, under 820 nm excitation provided by a Ti:Sapphire pulsed laser. The two-photon origin of the emission signal inside the phantom is demonstrated by the quadratic dependence of the PL intensity on the excitation power. Moreover, we focused on the evaluation of BSA-AuNCs' potential as contrast agents at different concentrations inside phantoms, simulating an ex vivo environment, at three NIR excitation wavelengths, in view of defining the optimal experimental conditions for future real-tissue imaging assays. The present study aims at translating our previous results on the successful performance of BSA-AuNCs as contrast agents for in vitro FLIM imaging, using visible light, towards non-invasive ex vivo NIR imaging applications. Besides the advantageous use of the combined techniques TPE-FLIM, the novelty of our work consists of demonstrating for the first time the capacity of BSA-AuNCs to perform as bright contrast agents inside cancer-tissue mimicking phantoms. We prove that BSA-AuNCs show great promise as fluorescent contrast agents for TPE-FLIM towards image-assisted tumor surgery.

Sub-wavelength lateral detection of tissue-approximating masses using an ultrasonic metamaterial lens

Practically applied techniques for ultrasonic biomedical imaging employ delay-and-sum (DAS) beamforming which can resolve two objects down to 2.1λ within the acoustic Fresnel zone. Here, we demonstrate a phononic metamaterial lens (ML) for detection of laterally subwavelength object features in tissue-like phantoms beyond the phononic crystal evanescent zone and Fresnel zone of the emitter. The ML produces metamaterial collimation that spreads 8x less than the emitting transducer. Utilizing collimation, 3.6x greater lateral resolution beyond the Fresnel zone limit was achieved. Both hard objects and tissue approximating masses were examined in gelatin tissue phantoms near the Fresnel zone limit. Lateral dimensions and separation were resolved down to 0.50λ for hard objects, with tissue approximating masses slightly higher at 0.73λ. The work represents the application of a metamaterial for spatial characterization, and subwavelength resolution in a biosystem beyond the Fresnel zone limit.

Diffuse correlation spectroscopy measurements of blood flow using 1064nm light.

.Significance: Diffuse correlation spectroscopy (DCS) is an established optical modality that enables noninvasive measurements of blood flow in deep tissue by quantifying the temporal light intensity fluctuations generated by dynamic scattering of moving red blood cells. Compared with near-infrared spectroscopy, DCS is hampered by a limited signal-to-noise ratio (SNR) due to the need to use small detection apertures to preserve speckle contrast. However, DCS is a dynamic light scattering technique and does not rely on hemoglobin contrast; thus, there are significant SNR advantages to using longer wavelengths () for the DCS measurement due to a variety of biophysical and regulatory factors.Aim: We offer a quantitative assessment of the benefits and challenges of operating DCS at 1064 nm versus the typical 765 to 850 nm wavelength through simulations and experimental demonstrations.Approach: We evaluate the photon budget, depth sensitivity, and SNR for detecting blood flow changes using numerical simulations. We discuss continuous wave (CW) and time-domain (TD) DCS hardware considerations for 1064 nm operation. We report proof-of-concept measurements in tissue-like phantoms and healthy adult volunteers.Results: DCS at 1064 nm offers higher intrinsic sensitivity to deep tissue compared with DCS measurements at the typically used wavelength range (765 to 850 nm) due to increased photon counts and a slower autocorrelation decay. These advantages are explored using simulations and are demonstrated using phantom and in vivo measurements. We show the first high-speed (cardiac pulsation-resolved), high-SNR measurements at large source–detector separation (3 cm) for CW-DCS and late temporal gates (1 ns) for TD-DCS.Conclusions: DCS at 1064 nm offers a leap forward in the ability to monitor deep tissue blood flow and could be especially useful in increasing the reliability of cerebral blood flow monitoring in adults.

Fluorescence Spectroscopy Study of Protoporphyrin IX in Optical Tissue Simulating Liquid Phantoms.

Fluorescence spectroscopy has been extensively investigated for disease diagnosis. In this framework, optical tissue phantoms are widely used for validating the biomedical device system in a laboratory environment outside of clinical procedures. Moreover, it is fundamental to consider that there are several scattering components and chromophores inside biological tissues and the interplay between scattering and absorption may result in a distortion of the emitted fluorescent signal. In this work, the photophysical behaviour of a set of liquid, tissue-like phantoms containing different compositions was analysed: phosphate buffer saline (PBS) was used as the background medium, low fat milk as a scatterer, Indian ink as an absorber and protoporphyrin IX (PpIX) dissolved in dimethyl formamide (DMF) as a fluorophore. We examined the collected data in terms of the impact of surfactant Tween-20 on the background medium, scattering effects and combination of scattering and absorption within a luminescent body on PpIX. The results indicated that the intrinsic emission peaks are red shifted by the scattering particles or surfactant, whilst the scattering agent and the absorbent can alter the emission intensity substantially. We corroborated that phantoms containing higher surfactant content (>0.5% Tween 20) are essential to prepare stable aqueous phantoms.

Cerenkov luminescence and PET imaging of 90Y: capabilities and limitations in small animal applications

The in vivo sensitivity limits and quantification performance of Cerenkov luminescence imaging have been studied using a tissue-like mouse phantom and 90Y. For a small, 9 mm deep target in the phantom, with no background activity present, the Cerenkov luminescence 90Y detection limit determined from contrast-to-noise ratios is 10 nCi for a 2 min exposure with a sensitive CCD camera and no filters. For quantitative performance, the values extracted from regions of interest on the images are linear within 5% of a straight line fit versus target activity for target activity of 70 nCi and above. The small branching ratio to decay with positron emission for 90Y also permits low-statistics PET imaging of the radionuclide. For PET imaging of the same phantom, with a small animal LSO detector-based scanner, the 90Y detection limit is approximately 3 orders of magnitude higher at 10 µCi.

Modelling and measurement of ultrasound vibration potential distribution in an agar phantom

Ultrasound vibration potential (UVP) is an electric signal generated from the vibration of particles or ions along with the trajectory of the ultrasound pulses travelling through a colloidal suspension or ionic electrolyte. Therefore, it may be used to characterize or image the physiochemical property of particles or ions. This paper presents a modelling method based on the principle of static charged disc dipole and its equivalent circuit to model the ultrasound vibration potential distribution (UVPD) inside domains of interest. A tissue-like testing phantom (in 82 × 56 × 66 mm) embedded with one or more sample cells made from either agar or colloids with two electrodes fitted at optimized locations outside of the phantom is reported. TheUVP measurements in peak-to-peak amplitude of 162/309 μV and 419/499 μV are measured from two interfaces of a single cell setting with either KCL (1 M) or nanoparticles (SiO2 in 21 nm, 1 wt%) mixed with agar. Results from the measurement comply with the modelling of UVPD. The experimental results are evidenced from the relative changes of normalised UVP signals from setting up six interfaces of three cells. The results demonstrate the feasibility of using the static electricity modelling method to estimate UVPD. This implies the potential of UVP for medicine and engineering.

Ultrafast ultrasound imaging of surface acoustic waves induced by laser excitation compared with acoustic radiation force.

Two generation mechanisms-optical perturbation and acoustic radiation force (ARF)-were investigated where high frame rate ultrasound imaging was used to track the propagation of induced SAWs. We compared ARF-induced SAWs with laser-induced SAWs generated by laser beam irradiation of the uniformly absorbing tissue-like viscoelastic phantom, where light was preferentially absorbed at the surface. We also compared the frequency content of SAWs generated by ARF versus pulsed laser light, using the same duration of excitation. Differences in the SAW bandwidth were expected because, in general, laser light can be focused into a smaller area. Finally, we compared wave generation and propagation when the wave's origin was below the surface. We also investigated the relationship between shear wave amplitude and optical fluence. The investigation reported here can potentially extend the applications of laser-induced SAW generation and imaging in life sciences and other applications.

Bio-Inspired Breastfeeding Simulator (BIBS): A Tool for Studying the Infant Feeding Mechanism.

This work introduces a bio-inspired breastfeeding simulator (BIBS), an experimental apparatus that mimics infant oral behavior and milk extraction, with the application of studying the breastfeeding mechanism in vitro. The construction of the apparatus follows a clinical study by the authors that collects measurements of natural intra-oral vacuum, the pressure from infant's jaw, tongue and upper palate, as well as nipple deformation on the breast areola area. The infant feeding mechanism simulator consists of a self-programmed vacuum pump assembly simulating the infant's oral vacuum, two linear actuators mimicking the oral compressive forces, and a motor-driven gear representing the tongue motion. A flexible, transparent and tissue-like breast phantom with bifurcated milk duct structure is designed and developed to work as the lactating human breast model. Bifurcated ducts are connected with a four-outlet manifold under a reservoir filled with milk-mimicking liquid. Piezoelectric sensors and a CCD (charge-coupled device) camera are used to record and measure the in vitro dynamics of the apparatus. All mechanisms are successfully coordinated to mimic the infant's feeding mechanism. Suckling frequency and pressure values on the breast phantom from the experimental apparatus are in good agreement with the clinical data. Also, the change in nipple deformation captured by BIBS matches with those from in vivo clinical ultrasound images. The fully-developed breastfeeding simulator provides a powerful tool for understanding the bio-mechanics of breastfeeding and formulates a foundation for future breastfeeding device development.

A Device for Wireless Powering of Battery-Free Implants via Inductive Coupling

A device for wireless powering of battery-free implants with 500-mW power consumption is considered. The design of the device is described. The device provides relatively high stability of operation (power drop less than 10%) in the case of coil misalignment typical of medical applications (up to 20 mm). The results of engineering tests and tests with a tissue-like phantom (isotonic solution) are presented.

Optical characterization of tissue-simulating phantom components at 405nm

Optical properties of India ink (1950375, Parker, Quink, England) and 1-µm polystyrene microsphere (07310-15, Polysciences, USA) have been predicted at 405nm. For this purpose, a single integrating sphere system and spectrophotometric transmission spectroscopy have been used to estimate the radiometric characteristics. Radiometric measurements utilized to retrieve optical coefficients based on two different methods. Extinction coefficient has been estimated using collimated transmittance. To reconstruct absorption and scattering coefficients, total transmittance, diffuse reflectance and transmittance were measured. Polystyrene albedo was 0.9925 and was 0.1044 for ink. The agreement of PS scattering coefficient in comparison to Mie theory was obvious. Full Text: PDF ReferencesB.W. Pogue, and M.S. Patterson, "Review of tissue simulating phantoms for optical spectroscopy, imaging and dosimetry", J. Biomed. Opt. 11, 4(2006). CrossRef D. Coluccia, J. Fandino, M. Fujioka, S. Cordovi, C. Muroi, and H. Landolt, "Intraoperative 5-aminolevulinic-acid-induced fluorescence in meningiomas", Acta. Neurochir. 152 (2010). CrossRef P. Valdes et al. "https://www.spiedigitallibrary.org/conference-proceedings-of-spie/8928/892809/Quantitative-spectrally-resolved-intraoperative-fluorescence-imaging-for-neurosurgical-guidance-in/10.1117/12.2039090.short", Congress. Neuro. Surg. 10, 1(2014). CrossRef S. J. Madeson, M. S. Patterson, and B. C. Wilson, "The use of India ink as an optical absorber in tissue-simulating phantoms", Phys. Med. Bio. 37, 5(1997). CrossRef P. Ninni, F. Martelli, and G. Zaccanti, "The use of India ink in tissue-simulating phantoms", Opt. Express. 18, 26(2010). CrossRef F. Martelli, and G. Zaccanti, "Calibration of scattering and absorption properties of a liquid diffusive medium at NIR wavelengths. CW method", Opt. Express.15, 2(2007). CrossRef L. Spinelli et al. "Determination of reference values for optical properties of liquid phantoms based on Intralipid and India ink", Biomed. Opt. Express. 5, 7(2014). CrossRef Y. Liu, Y. Kim, and V. Beckman, "Development of a bioengineered tissue model and its application in the investigation of the depth selectivity of polarization gating", App.Opt. 44, 12 (2005). CrossRef B. Wilson, M. Patterson, and S. Flock, "INDIRECT VERSUS DIRECT TECHNIQUES FOR THE MEASUREMENT OF THE OPTICAL PROPERTIES OF TISSUES", Photochem. Photobiol. 46, 5(1987). CrossRef L. L. Sandell, and T. C. Zhu, "A review of in‐vivo optical properties of human tissues and its impact on PDT", J. Biophotonics. 4,(2011). CrossRef A. Shahin, M. Sayem El-Daher, and W. Bachir, "Determination of the optical properties of Intralipid 20% over a broadband spectrum", Phot. Lett. Poland. 10, 4(2018). CrossRef A. Karinov, A. Mokeeva, E. Segeeva, P. Agrba, and M. Kirillin, "Optical properties of mouse biotissues and their optical phantoms", Opt. Spec. 115, 2(2013). CrossRef C. Matzler, Matlab Functions for Mie Scattering and Absorption, version 2 (Bern, Bern university 2002). DirectLink D. Roysten, R. Poston, and S. Prahl, "Optical properties of scattering and absorbing materials used in the development of optical phantoms at 1064 nm", JBO. 1, 1(1996). CrossRef A. Shahin, and W. Bachir, "Broadband spectroscopy for characterization of tissue-like phantom optical properties", Pol. J. Med. Phys. Eng. 21, 4(2017). CrossRef

Finite Bending and Straightening of Hyperelastic Materials: Analytical Solution and FEM

In this research, an incompressible, isotropic, nonlinear elastic rectangular block and a circular cylindrical sector are studied under bending and straightening moments, respectively. Analytical approaches are presented on implementing of the left Cauchy–Green tensor and Cauchy stresses. In addition, finite element analysis of both problems is carried out using UHYPER user-defined subroutine in ABAQUS to verify the analytical methods. Four different invariant-based strain energy functions, including neo-Hookean, Mooney–Rivlin, Arruda–Boyce, and recently proposed polynomial Exp-Exp models, are examined, and the results are compared. Material parameters of silicon rubber for the strain energy functions are identified by applying an optimization procedure. Finite element method results confirmed the analytical approach with great compatibility. Results showed that the length of the unbent beam does not affect the stress. Likewise, the initial angle of curved structure does not affect the unbending moment and stresses. Moreover, the Exp-Exp model had a slightly different result rather than other strain energies, which means that this model is more conservative than its counterparts. Furthermore, the Exp-Exp strain energy function is calibrated for tissue-like phantom and is compared with experimental data.

Light transport with the equation of radiative transfer: The Fourier Continuation – Discrete Ordinates (FC–DOM) Method

We present a method for the treatment of the time dependent radiative transfer equation under the discrete ordinate approximation. The novelty of the proposed approach stems, in part, from the incorporation of a spectral method for the calculation of the spatial differential operators based on the Fourier Continuation procedure introduced recently by Bruno and co–authors. This is a spatially dispersionless and high order method, which can handle arbitrary geometries, including those encountered in the forward model of light transport in optical tomography. We validate our theoretical results by comparison with analytic and experimental outcomes of the fluence measurements on tissue-like phantoms. The method makes it possible to calculate the time of flight of photons in random media efficiently and with high accuracy.

Three‐dimensional frequency‐domain optical anisotropy imaging of biological tissues with near‐infrared light

Near-infrared optical imaging aims to reconstruct the absorption and scattering coefficients in order to detect tumors at early stage. However, the reconstructions have only been limited to and due to theoretical and computational limitations. The authors propose an efficient method of the reconstruction, in three-dimensional geometries, of the anisotropy factor g of the Henyey-Greenstein phase function as a new optical imaging biomarker. The light propagation in biological tissues is accurately modeled by the radiative transfer equation (RTE) in the frequency-domain. The reconstruction algorithm is based on a gradient-based updating scheme. The adjoint method is used to efficiently compute the gradient of the objective function which represents the discrepancy between simulated and measured boundary data. A parallel implementation is carried out to reduce the computational time. We show that by illuminating only one surface of a tissue-like phantom, the algorithm is able to accurately reconstruct optical values and different shapes (spherical and cylindrical) that characterize small tumor-like inclusions. Numerical simulations show the robustness of the algorithm to reconstruct the anisotropy factor with different contrast levels, inclusion depths, initial guesses, heterogeneous background, noise levels, and two-layered medium. The crosstalk problem when reconstructing simultaneously and g has been reported and achieved with a reasonable quality. The proposed RTE-based reconstruction algorithm is robust to spatially retrieve and localize small tumoral inclusions. Heterogeneities in g-factor have been accurately reconstructed which makes the new algorithm a candidate of choice to image this factor as new intrinsic contrast biomarker for optical imaging.

Optical method to extract the reduced scattering coefficient from tissue: theory and experiments.

Tissues are considered challenging in terms of structure and composition analysis due to their tendency to multiple scatter the incident light. One of the most common theories for extracting optical properties of tissue is diffusion reflection (DR). In this Letter, we propose a new paradigm for estimating the reduced scattering coefficient of a medium from the reflected light phase. The technique is a modified DR theory wherein the phase is calculated by the product of the wavenumber and the average pathlength. This theory is supported by the reconstructed phase of tissue-like phantom experiments from an iterative algorithm.

Three-Dimensional Highly Sensitive Diffusion Reflection-Based Imaging Method for the in Vivo Localization of Atherosclerosis Plaques Following Gold Nanorods Accumulation.

In this work, we present a novel, simple, and highly accurate three-dimensional (3D) diffusion reflection (DR) imaging system and method for the detection of accumulation sites of gold nanorods (GNRs) within the tissue. GNRs are intensively used for diagnosis purposes of varied diseases, mainly because of their ability to well absorb visible light, which introduces them as terrific contrast agents in various imaging and theranostics methods. Lately, these GNRs unique absorption properties have served in DR intensity-based measurements, suggesting a novel diagnostic tool, DR-GNRs. In this paper, we show a new measurement system and method for DR, based on its radial collection from the tissue. These radial measurements enabled a unique 3D presentation of the DR-GNR, introducing the dimensions ρ for the radius, θ for the angle, and Γ for the reflected intensity. On the basis of the diffusion model, which enables to correlate between the sample’s optical properties and its reflectance, a unique, radial map is presented. This map introduces the slopes of the DR curves in each measured angle, which are linearly correlated with the tissue’s optical properties and with the GNRs concentrations within the tissue, thus enables the exact radial localization of the GNRs in the sample. We show the detection of macrophage accumulation in tissue-like phantoms, as well as the localization of unstable plaques in hyperlipidemic mice, in vivo. This highly accurate, powerful technology paves the way toward a real-time detection method that can be successfully integrated in the rapid increasing field of personalized medicine.

Technical Note: Experimental verification of magnetic field-induced beam deflection and Bragg peak displacement for MR-integrated proton therapy.

Given its sensitivity to anatomical variations, proton therapy is expected to benefit greatly from integration with magnetic resonance imaging for online anatomy monitoring during irradiation. Such an integration raises several challenges, as both systems mutually interact. The proton beam will experience quasi-continuous energy loss and energy-dependent electromagnetic deflection at the same time, giving rise to a deflected beam trajectory and an altered dose distribution with a displaced Bragg peak. So far, these effects have only been predicted using Monte Carlo and analytical models, but no clear consensus has been reached and experimental benchmark data are lacking. We measured proton beam trajectories and Bragg peak displacement in a homogeneous phantom placed inside a magnetic field and compared them to simulations. Planar dose distributions of proton pencil beams (80-180MeV) traversing the field of a 0.95T NdFeB permanent magnet while depositing energy in a PMMA slab phantom were measured using EBT3 radiochromic films and simulated using the Geant4 toolkit. Deflected beam trajectories and the Bragg peak displacement were extracted from the measured planar dose distributions and compared against the simulations. The lateral beam deflection was clearly visible on the EBT3 films and ranged from 1 to 10mm for 80 to 180MeV, respectively. Simulated and measured beam trajectories and Bragg peak displacement agreed within 0.8mm for all studied proton energies. These results prove that the magnetic field-induced Bragg peak displacement is both measurable and accurately predictable in a homogeneous phantom at 0.95T, and allows Monte Carlosimulations to be used as gold standard for proton beam trajectory prediction in similar frameworks for MR-integrated proton therapy.

Fluorescence molecular imaging based on the adjoint radiative transport equation

A new reconstruction algorithm for fluorescence diffuse optical tomography of biological tissues is proposed. The radiative transport equation in the frequency domain is used to model light propagation. The adjoint method studied in this work provides an efficient way for solving the inverse problem. The methodology is applied to a 2D tissue-like phantom subjected to a collimated laser beam. Indocyanine Green is used as fluorophore. Reconstructed images of the spatial fluorophore absorption distribution is assessed taking into account the residual fluorescence in the medium. We show that illuminating the tissue surface from a collimated centered direction near the inclusion gaves a better reconstruction quality. Two closely positioned inclusions can be accurately localized. Additionally, their fluorophore absorption coefficients can be quantified. However, the algorithm failes to reconstruct smaller or deeper inclusions. This is due to light attenuation in the medium. Reconstructions with noisy data are also achieved with a reasonable accuracy.

High-resolution Imaging of Myeloperoxidase Activity Sensors in Human Cerebrovascular Disease

Progress in clinical development of magnetic resonance imaging (MRI) substrate-sensors of enzymatic activity has been slow partly due to the lack of human efficacy data. We report here a strategy that may serve as a shortcut from bench to bedside. We tested ultra high-resolution 7T MRI (µMRI) of human surgical histology sections in a 3-year IRB approved, HIPAA compliant study of surgically clipped brain aneurysms. µMRI was used for assessing the efficacy of MRI substrate-sensors that detect myeloperoxidase activity in inflammation. The efficacy of Gd-5HT-DOTAGA, a novel myeloperoxidase (MPO) imaging agent synthesized by using a highly stable gadolinium (III) chelate was tested both in tissue-like phantoms and in human samples. After treating histology sections with paramagnetic MPO substrate-sensors we observed relaxation time shortening and MPO activity-dependent MR signal enhancement. An increase of normalized MR signal generated by ultra-short echo time MR sequences was corroborated by MPO activity visualization by using a fluorescent MPO substrate. The results of µMRI of MPO activity associated with aneurysmal pathology and immunohistochemistry demonstrated active involvement of neutrophils and neutrophil NETs as a result of pro-inflammatory signalling in the vascular wall and in the perivascular space of brain aneurysms.

Phantom Preparation and Optical Property Determination

Tissue-like optical phantoms are important in testing new imaging algorithms. Homogeneous optical phantoms with determined optical properties are the first step of making a proper heterogeneous phantom for multi-modality imaging. Typical recipes for such phantoms consist of epoxy resin, hardener, India ink and titanium oxide. By altering the concentration of India ink and titanium oxide, we are able to get multiple homogeneous phantoms with different absorption and scattering coefficients by carefully mixing all the ingredients. After fabricating the phantoms, we need to find their individual optical properties including the absorption and scattering coefficients. This is achieved by solving diffusion equation of each phantom as a homogeneous slab under canonical illumination. We solve the diffusion equation of homogeneous slab in frequency domain and get the formula for theoretical measurements. Under our steady-state diffused optical tomography (DOT) imaging system, we are able to obtain the real distribution of the incident light produced by a laser. With this source distribution we got and the formula we derived, numerical experiments show how measurements change while varying the value of absorption and scattering coefficients. Then we notice that the measurements alone will not be enough for us to get unique optical properties for steady-state DOT problem. Thus in order to determine the optical properties of a homogeneous slab we want to fix one of the coefficients first and use optimization methods to find another one. Then by assemble multiple homogeneous slab phantoms with different optical properties, we are able to obtain a heterogeneous phantom suitable for testing multi-modality imaging algorithms. In this paper, we describe how to make phantoms, derive a formula to solve the diffusion equation, demonstrate the non-uniqueness of steady-state DOT problem by analysing some numerical results of our formula, and finally propose a possible way to determine optical properties for homogeneous slab for our future work.