1,721,167 research outputs found
Structured illumination and time gated detection for diffuse optical imaging
No full textStructured illumination and time gated detection for diffuse optical imagin
Temporal propagation of spatial information in turbid media
No full textThe time-resolved propagation of spatial frequencies in turbid media is investigated. We discuss the relevant
information content in terms of the spatial Fourier component of the propagating pulse. We present a
method to record and analyze the time-gated spatial frequency response of highly scattering media. We dem-
onstrate that high spatial frequency information appears in the early time-gated signal, whereas low fre-
quencies persist for longer times
Imaging of highly scattering media by spatially modulated pulsed light
No full textThe use of spatially modulated light is finding application in biomedical optics having potential use in imaging and tomography of tissues and small animals. We describe the time-resolved propagation of spatial frequencies in turbid media. We present a set-up based on a ps laser source, spatially modulated by a micro-mirror device and a time-gated intensifier. We discuss the relevant information content that can be useful for imaging of tissues, in terms of the spatial Fourier components of the propagating pulse. We demonstrate that high spatial frequencies appear in the early time-gated signal whereas low frequencies persist for longer times and that the combined use of high spatial frequencies and early time gates can be used to improve the resolution in imaging
Analysis of ICCD time-gated images through turbid media using a perturbative model
No full textOptical imaging through turbid media has gathered a great interest as a non-invasive method to localize tumors inside the body. A step forward in this direction could be provided by a parallel detector that allows one to acquire a huge amount of data in a short time. This could result in a more stable reconstruction of the optical properties of the sample and in a more reliable diagnosis. We used a system based on a fast gated intensified CCD camera capable of a gate width <200 ps to acquire time sliced images of the light transmitted though a phantom simulating the optical properties of the human breast. Light pulses emitted by a laser diode (633 nm) were delivered to the central position of the phantom, while the output plane was imaged by the ICCD (fan geometry). Experimental data were analyzed using an analytical expression for homogeneous medium and a perturbative model, both derived from the Random Walk Theory (RWT). By using the perturbative approach we evaluated the depth (along Z axis) of scattering inclusions and their scattering coefficient
Clinical system for skin tumour detection by fluorescence lifetime imaging
No full textA portable system based on Fluorescence Lifetime Imaging has been developed and tested for the detection of skin tumors in humans. The Heme precursor δ-aminolevulinic acid, which promotes the preferential accumulation of the endogenous Protoporphyrin IX in proliferative tissues, is used as an exogenous marker to target the tumor. Then, using a gated intensified camera, two or more images of the sample are acquired after different delays with respect to the excitation pulses. The images are processed in order to calculate the spatial map of the fluorescence decay time of the sample. The localization of the tumor is based on the longer decay time detected in neoplastic tissues with respect to healthy ones
Time-domain transmittance imaging in turbid media using an intensified CCD camera
No full textA fast gated intensified charge coupled device (CCD) with picosecond time resolution was demonstrated to be used as a parallel detector to perform time-resolved optical imaging through turbid media. It allowed to sample in a short time the intensity profile in many thousands of points over an area of 6 cm in diameter. It was concluded that the intensifier operated at 80 MHz and it can be coupled to high frequency pulsed diode
Use of a fast CCD camera for imaging through turbid media”
No full textIn this paper we present a system for optical imaging in turbid media based on an intensified CCD camera. The time-gating capability of the light intensifier has been used to acquire time sliced images of the light transmitted through phantoms made of intralipid and ink solutions. Then, we analyzed the images by fitting the time series with a theoretical expression for photon migration. This allowed us to recover the maps of the absorption (mu (a)) and scattering (mu (s)') coefficients in an extended area of the samples. Using our system a possible heterogeneity in the sample can be easily detected. We characterized the performances of the system following two approaches. First, we evaluated the linearity of the relationship between the recovered absorption coefficient and the ink concentration and between the recovered scattering coefficient and the intralipid content (homogeneous samples). Then, we measured the apparent contrast in the mu (s)' maps resulting from small inclusions with a scattering coefficient higher and lower with respect to a homogeneous background (heterogeneous samples). Results encourage further researches
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