Questions related to Biomedical Optics
There are many fields where light field can be utilized. For example it is utilized in microscopy  and for vision based robot control . Which additional applications do you know?
Thank you in advance!
 Li, H., Guo, C. and Jia, S., "High-resolution light-field microscopy," Frontiers in Optics, FW6D. 3 (2017).
 Tsai, D., Dansereau, D. G., Peynot, T. and Corke, P. , "Image-Based Visual Servoing With Light Field Cameras," IEEE Robotics and Automation Letters 2(2), 912-919 (2017).
Dear professors and colleagues,
I am going to to study effect of the two photons absorption in Safranin O. Safranin O is organic material, so I think that the power needed to activate this effect doesn't need to be too high. However, the two photons absorption is a third-order nonlinear optical effect, so it is usually implemented with high-power pulsed lasers. I cannot afford to buy high-power pulsed lasers. So, can I stimulate effect of two photons absorption in safranin O by continuous wave laser (808 nm or 1064 nm)? And how much is the required power of laser? I hope the colleagues who have experience in this experiment share me useful information.
I look forward to hearing from you. Thanks in advance.
I am investigating methods to determine the photodynamic activity of photosensitizers for photodynamic therapy. One of the methods being used is absorption spectrometry. A work concludes that significant absorption of light was shown to be prerequisite but not sufficient for high photodynamic activity. My point of view is: When a photosensitizer absorbs more radiation at a certain wavelength, it will produce more Ros (Reactive oxygen species), i.e the absorption maximum will correspond to the wavelength active photodynamic effect best. However, this point of view contradicts the viewpoint in above work. I look forward colleagues to explain this question.
Thanks in advance.
I have three collimated optical beams with 1cm separation between the adjacent one. I want to shift one of the three beam laterally so that it goes closer towards or farther away from the adjacent beam by micrometer accuracy.
I am trying to analyse some OCT pullbacks using Osirix, having never used the software before. My aim is to measure CSA at various points of the pullback, and also to semi-quantitatively analyse the plaque characteristics. Any advice will be very hepful
I was wondering how to find non fluorescent plastic coverslips for optical in vivo imaging. We now use glass coverslips 3mm in diameter, 0,15mm thick, but want to find a plastic substitute. According to this paper http://www.ncbi.nlm.nih.gov/pubmed/16286964, PDMS seems to be good. But I cannot find any commercial supplier of coverslips made of this material. Could anyone be so kind to provide some advice?
What additional information does the phase measurement in a frequency-domain imaging technique provide compared with the continuous wave technique that measures only the amplitude of the diffuse light?
The Z-scan technique is proposed by Sheik-Bahae et al . Theoretically, when there is no nonlinear absorption, the Z-scan curve must be symmetric around the origin of the Z-axis. However, in practice, the Z-scan curve usually has a large asymmetry. I know the reason for this phenomenon for thermal-optic nonlinear mechanisms. For the electronic nonlinear mechanism, what are the reasons for this asymmetric phenomenon? (Except for experimental error).
Thank you and hoping for your insightful response.
 Sheik-Bahae, Mansoor, et al. "Sensitive measurement of optical nonlinearities using a single beam." IEEE journal of quantum electronics 26.4 (1990): 760-769.
I am wondering what is the impact of the presence of edema and/or necrosis on optical coefficients (absorption, scattering, anisotropy coefficients) in a biological tissue?
I cannot find any papers on this subject...
I do not have access in the ICRU report 46 and I am not able to retrieve complete information regarding the tissue composition of prostate, urethra and rectum for a Monte Carlo simulation of brachytherapy that I want to do. Is there any knowledge regarding the composing elements, their ratios and the density of each of these three structures? Any bibliographic reference is also well appreciated.
Thank you in advance,
I would like to measure optical coefficients (anisotropy, absorption and scattering) of a phantom developed in my lab. However, we just own a 3-port integrating sphere (it does not have a port in front of the entry port of the sphere). So, how can I measure the diffuse reflectance without placing a sample in the exit port (because I do not have an exit port directly in front of the entry port)? Thank you in advance.
I need to design an optical solid phantom with defined optical properties. Assuming that I know my required optical properties (including absorption and scattering coefficient and g which in fact are resembling tissue optical properties) how can I find out how much absorbing agent I need to add to the phantom mixture to obtain desired absorption coefficient?
Scattering coefficient could be calculated form Mie theory. Is it used for absorption as well?
Thanks very much,
I am very much interested in depth of imaging capabilities of UOT, however I would like to know if there has been efforts to take the spatial resolution from the mm to micron level. (Don't worry I'm not being that lazy - I am actively searching myself but I like the idea of working smarter not harder). If anyone has any leads, please let me know!
I have a simulation results, which in fact is a finite element mesh showing variation of light intensity at the surface.
Via experiments I have an image taken by a normal camera showing intensity over a surface.
Now I want to correlate these two together, to decide about next set of experiments and simulation, and in short get some useful data. In particular I'm interested to correlate the variation in intensity in simulations and experiments.
What can I do about that?
Any ideas or insights is appreciated.
I have to set up a phantom study as well as an in vivo study for measuring light reflectance spectra of human tissue using diffuse reflectance spectroscopy technique.
I have to choose up to 4 wavelengths but not sure what wavelengths do I need to perform my experiments.
Need to be mentioned that data obtained from experiments will be used for validating numerical a light propagation numerical model (Monte Carlo).
As my second question, what difference does it make using a LED as a light source instead of laser?
Thank you very much.
Wondering what would be the definition of attenuation and diffusion coefficients, their relationship with blood volume fraction ?
Does the relationship differs case to case (different tissue, and/or experimental setup, etc)? How this relationship could be formulated?
Any insight or introductions to suitable publications is greatly appreciated.
Hallo everyone! Have you any experience about the implementation of inverse Monte Carlo algorithm for the simulation of photon transport through biological tissues and th estimation of optical properties (absorption, scattering and anisotropy coefficients)?
I implemented the algorithm on Matlab, it works, but I have some doubts.
Thank you in advance for you kind attention,
Does COMSOL have the same capabilities as the monte carlo method in modeling light-tissue interactions in terms of calculating and obtaining light distribution over the surface as well as inside the tissue in 3D?
I am looking for an open source Optical-simulator to simulate simple light transmission through a block with specific absorption and scattering coefficients. Can anyone recommend me one, since online search was not very helpful ?
Or if you can suggest some other substitute from your experience. Any help will be highly appreciated.
I'm wondering if somebody tried to extract a local photon density in a turbid medium from local extinction measurements with gold nanoparticles present in the medium. Let's say that there's a known density of gold nanoparticles present as a localized inclusion and acting as a probe in a certain area inside a turbid medium, and one can measure the extinction (or absorption) values caused by them in this area. Is there a way to estimate the local photon density from such measurements?
The linearly polarized light incident to the tissue gives us different response from the surface and the bulk in the highly scattering tissues such as dermis, retina, etc.
The reflected light from the surface keeps the same polarization while the light reflected back from the layers in depth undergoes the multiple scattering that certainly depolarize the incident light. The de-polariztion ratio may account for the discrimination of the unhealthy from healthy tissues leading to the diagnosis of the disease.
The phenomena may contribute to diagnosis the diabetic retinopathy , dermal disorders and cutaneous and subcutaneous diseases.
I'd need to collect NIR light trans-urethrally with an optical fiber. Does anybody know if such optically transparent (~700 nm -900 nm) catheters exist? Can you recommend the company and model, please?
P.S. In particular, I'd be interested in catheters made from Ultra Clear Silopren LSR 7000 liquid silicone rubber (LSR) if somebody makes them. LSR 700 has ~ a striking 94% flat transmission in the entire VIS-NIR range!
The classical Beer-Lambert law (BLL) can be applied for extraction of optical properties of a sample (mu_a or mu_extinction in a more general case) under known and controlled illumination & detection conditions as for example in a conventional cuvette spectroscopy.
For turbid media applications, it has to be modified to account for scattering and increased optical pathlength. So, it transforms to the modified Beer-Lambert law (MBLL). Then, it is usually applied to get information about optical properties of chromophore(s) that are distributed in turbid media. For example, hemoglobin in tissues etc.
Does anybody know if MBLL (or BLL) was applied to obtain optical properties of a localized chromophore inclusion embedded in turbid media? Imagine doing spectroscopic cuvette measurements with the cuvette filled with a certain chromophore and detector embedded in a biological tissue, for example and trying to extract its mu_a. Has anybody tried to adopt MBLL for this purpose by accounting for absorbed and scattered photons?
I’d like to set up collaboration with those who have an access to human and/or canine prostates with cancer and might be interested in 1) exploring interstitial optical studies of prostates with cancer for diagnostic purposes and 2) using gold nanoparticles as contrast agents for prostate cancer detection. The goal is two-fold.
First, we want to establish a correlation between concentrations of major chromophores like Hb, HbO2 and H2O and a presence of PC, as well as measure optical absorption and scattering parameters of the organ on ex vivo excised prostates. Since those prostates will be excised anyway we’d like to perform optical measurements on them after excision before they go for some other destructive tests etc. Once this stage is completed and data make sense, we can proceed to a development of an endoscope for performing such measurements in vivo (illumination via rectum, detection via urethra). The approach would be similar to cystoscopy and will utilize a side-firing fiber (or its variation) as a detector and a cylindrical diffuser as the light source.
Second, we would like to target PC biomarkers (like PSMA) in the gland, functionalize gold nanoparticles with appropriate surface agents, deliver Au NPs to the prostate with cancer and detect them with the same technique (illumination via rectum, detection via urethra). This project is more challenging on a number of reasons: 1) preparing Au NPs for targeting PMSA and still protected from RES that can be efficiently accumulated in the gland has never been done (most studies in vitro); 2) since such studies would require working with Au NPs and patients, FDA approval can be an issue. Doing these experiments in dogs would be almost ideal. However, there are conflicting reports on PSMA as a biomarker in canine prostate cancer (see below). Thus, if PSMA can indeed be used and targeted in canine PC, no human prostates would be involved and entire experiments can be performed on canine prostates.
Why not going with rats, for example? Because of the size of the prostate. We really want to go through cm’s of prostate tissue, and dog’s prostate is almost an ideal substitute for a human prostate (sizewise). On the other hand, we’d like to target realistic Au NPs concentrations in the prostate that can be achieved in such studies. So, I’d really like to get your thoughts and possibly practical suggestions on this aspect. I do believe that such molecular imaging of PC via optical detection of Au NPs may not only improve the early cancer detection but pave the way for Au NPs-mediated thermal therapies for focal cancer ablation (but this is a scientist talking:) The nature of this project would require a multidisciplinary team of oncology urologists, molecular biologists, chemists.
We can detect Au NPs in the prostate via urethra using optical radiance technique. Moreover, the sensitivity is much better than the sensitivity of the clinical CT (see the comparison in the publication and relevant references). We can see <=10^10 Au nanorods in the prostate. It means that with saturating of 1-10% of existing PSMA copies per cell ( close to 10^6 sites per cell), detecting 10^10 Au NPs would correspond to seeing ~10^5 malignant cells in the prostate. This number corresponds to the so-called angiogenic switch indicating very promising potential for early cancer detection.
More details on the method are provided in our recent publication (below). I encourage you to read it, and I’d be happy to discuss logistics and answer questions on this topic because there is no way to address all relevant issues in this posting.
Really looking forward for the feedback!
I am pursuing research on smart glass- glass with optics embedded in it. I want to try this smart glass first using a functioning model of the eye instead of real eyes. I am looking for such model of an optical eye. Can I put eyeglass on the face with a dummy functioning eye to check whether the smart glass design works or not?
Any input is valuable. I want to add these results to a publication so I am really keen to find optimal solution of setup.
Does it mean that light is particle?
To my knowledge , the light detectors within any spectral range detects light based on photon property of light. The array detector function is also based on photon interaction with sensor. Interference as a significant wave effect of light occurs when it meets the adequate degree of spatial and temporal coherence and does not influence on the photon detection. Diffraction as other main wave effect of light takes place in the slits or periodical structures suitable for spectral resolution, however does not affect on photon detection. Despite, light in resonator performs as a wave , again the stationary or traveling wave formation ( axial and traverse modes in laser cavity) can not influence on photon detection principle. The propagation of light in fiber (LP modes) may be another example that wave characteristics of light contribute to the mode formation, however detection is always based on photon counting.
There is an indication (J. H. Ali, W. B. Wang, M. Zevallos and R. R. Alfano, "Near infrared spectroscopy and imaging to probe differences in water content in normal and cancer human prostate tissues," Technol. Cancer Res. Treat. 3, 491-497 (2004)) that cancer tissues may have lower water content in vitro. I'm wondering if somebody done similar studies (in vitro, ex vivo, in vivo). While the prostate is of the main interest, any other organs and tissues would do it as well!
I couldn't find much (or anything) on reports of spectrally resolved optical properties (absorption and scattering) of thermally coagulated muscle tissue. So, please share your knowledge on the topic. Human, bovine, porcine, canine - anything would be useful. Any group of muscles will do. Single-wavelength measurements will be useful as well.
I am modelling the oblique incident reflectance profiles using a diffusion model, but would like to examine the range in which it is valid.
I am new to the Optical Bloch Equation (OBE) and because of my background in NMR, I found the approach used by Erwin Hahn in the attached paper very fascinating and easy to follow. It has helped with understanding concepts used in
(1) the Springer Handbooks of Atomic, Molecular, and Optical Physics and
(2) the Atom-Photon Interactions by Claude Cohen-Tannoudji and Gilbert Grynberg.
However, I found out (possibly due to my limited knowledge in this area) that contemporary OBEs are slightly different (in terms of terminology) from OBEs as presented by E.L. Hahn.
Therefore, I would like experts to kindly explain some terms in the attached paper. These terms are 'po' (equivalent to NMR magnetic moment on page 24); the term equivalent to gyromagnetic ratio (on page 24) which is equal to 2po/Planck constant (which also appears before the applied field term in the last equation on page 26); and 'N' and 'g' (in the integrals 2a and 2b on page 26).
I want to know what these four terms stand for in optics and how they can be measured in the laboratory.
I understand that 'N(po)u' is a component of the polarization in the system where 'u' is the Bloch vector in the x direction.
It appears from published literature, that an individual Au nanocage produces about an order of magnitude higher absorption cross-section than an individual Au nanorod (considering 750-850 nm spectral range and corresponding dimensions of the nanoparticles). Does anybody know if there was some other shape that can do even better than nanocages? I'm looking for strong dominant absorbers (absorption>>scattering).
I am interested in using optical fibers with sharpened tips for detection in biochemical systems. We are coating the tips with metallic films or nanoparticles. I've noticed that groups that make these types of sensors always detect the transmitted light from the tip of the fiber. I am curious whether or not the reflected light could be harnessed to do the same sorts of measurements.
I know the relationship between the light transmittance and reflectance of a metallic-coated tapered optical fiber is not trivial, but is there any reason to believe the light reflectance would not be usable in measuring environmental changes?
Any info on the subject is tremendously helpful, even if it does not directly resolve my question.