Pass-through photon-based biomedical transillumination

Vacas-Jacques, Paulino; Паез, Гонзало; Strojnik, Marija

doi:10.1117/1.2953191

Cited by 13 publications

(4 citation statements)

References 61 publications

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“…Experimentally, the coherence of the illuminating laser beam was decreased to shorten the time interval during which useful signal was collected. 9 Theoretically, and within the data-processing community, increasingly sophisticated models started to be developed to determine these parameters using statistical techniques. 10 Both of these schemes led to the evaluation of parameters, even though the time-gating interval in the first does not appear to be an intrinsic consequence of the tissue features, but rather of the probing beam.…”

Section: Signal Broadening Within Tissuementioning

confidence: 99%

Tissue characterization with ballistic photons

Strojnik

Паез

2009

SPIE Proceedings

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We propose tissue characterization with ballistic photons, those whose direction or propagation speed is not affected by the presence of tissue. The most critical aspect of the tissue characterization problem is calibration of experimental measurements. The calibration method relates the fringe irradiance (power modulation in one interferometer arm) with the sample concentration under controlled conditions. During this step, the absorption and scattering indices β a and β sc are determined as a function of concentration for each material or tissue of interest, using a set of containers to vary travel distance D. It is assumed that linear scattering coefficient, k sc (absorption coefficient, α a ), is proportional to the number of scattering particles per unit volume, or particle concentration, c, in [ml/l]. Attenuation is proportional to concentration of scattering (absorption) centers and the sample length. The sensitivity of method is estimated at 10 -19 with uncoated plate beam-splitters and intensified photon-counting detector. Signal broadening within tissueOptical means of tissue characterizations have become of great importance within the last 20 years, due to the availability of short pulse laser sources and detectors with nearly instantaneous response. 1-4 With the understanding of the structural changes introduced in the biological samples due to demanding sample preparation methods in electron microscopy practice, the optical techniques started to be once again considered superior in biological sample characterization.Identification of three parameters is believed to be the key to the knowledge and characterization of the biological samples under evaluation: the linear coefficient of absorption μ a [mm -1 ], the linear coefficient of scattering μ sc [mm -1 ], and an all-purpose fudge factor whose primary function is to relate linear tissue properties with their volume features. 5 Experimentally, these factors are difficult, if not impossible, to determine with a high degree of certainty because there does not exist a well-defined event in time to separate once-, twice-, and multiply-scattered photons from the ballistic photons. 6-8 We define the ballistic photons to be those that are transmitted through the sample without undergoing any scattering, not even suffering a small-angle deviation, and that are not absorbed by the sample.Previously, two partial solutions were implemented to address these shortcomings providing methodology to arrive at these two coefficients, μ a and μ sc , employing a certain amount of data fitting. Experimentally, the coherence of the illuminating laser beam was decreased to shorten the time interval during which useful signal was collected. 9 Theoretically, and within the data-processing community, increasingly sophisticated models started to be developed to determine these parameters using statistical techniques. 10 Both of these schemes led to the evaluation of parameters, even though the time-gating interval in the first does not appear to be an intrinsic consequence of ...

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Section: Signal Broadening Within Tissuementioning

confidence: 99%

Tissue characterization with ballistic photons

Strojnik

Паез

2009

SPIE Proceedings

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“…6,[8][9][10]12,13,18,35,40 The great advantage of the optical techniques is that they are noninvasive and nondestructive, producing no damage to the subject under test. Possibly, their greatest disadvantage is that the diagnostic work on a live subject introduces many adverse conditions, as compared to those in vitro.…”

Section: Introductionmentioning

confidence: 99%

Wavelength Selection Method with Standard Deviation: Application to Pulse Oximetry

2011

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Near-infrared spectroscopy provides useful biological information after the radiation has penetrated through the tissue, within the therapeutic window. One of the significant shortcomings of the current applications of spectroscopic techniques to a live subject is that the subject may be uncooperative and the sample undergoes significant temporal variations, due to his health status that, from radiometric point of view, introduce measurement noise. We describe a novel wavelength selection method for monitoring, based on a standard deviation map, that allows low-noise sensitivity. It may be used with spectral transillumination, transmission, or reflection signals, including those corrupted by noise and unavoidable temporal effects. We apply it to the selection of two wavelengths for the case of pulse oximetry. Using spectroscopic data, we generate a map of standard deviation that we propose as a figure-of-merit in the presence of the noise introduced by the living subject. Even in the presence of diverse sources of noise, we identify four wavelength domains with standard deviation, minimally sensitive to temporal noise, and two wavelengths domains with low sensitivity to temporal noise.

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“…An interferometric ex− perimental arrangement permits the formation of interfer− ence patterns only between the coherence−preserving, pass− −through photons and those in the reference beam [24,25]. A single pass interferometer is preferable to the Michelson two−pass interferometer in the process of identification of ballistic photons because of its increased sensitivity [26][27][28]. Previously, we performed Monte−Carlo simulation stu− dies on trans−illumination.…”

Section: Modulation Of Ballistic Beamsmentioning

confidence: 99%

Tissue characterization with ballistic photons: counting scattering and/or absorption centres

Corral-Martínez

Strojnik

Паез

2015

Opto-Electronics Review

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We describe a new method to separate ballistic from the scattered photons for optical tissue characterization. It is based on the hypothesis that the scattered photons acquire a phase delay. The photons passing through the sample without scattering or absorption preserve their coherence so they may participate in interference. We implement a Mach−Zehnder experimental setup where the ballistic photons pass through the sample with the delay caused uniquely by the sample indices of refraction. We incorporate a movable mirror on the piezoelectric actuator in the sample arm to detect the amplitude of the modulation term. We present the theory that predicts the path−integrated (or total) concentration of the scattering and absorption centres. The proposed technique may characterize samples with transmission attenuation of ballistic photons by a factor of 10

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Pass-through photon-based biomedical transillumination

Cited by 13 publications

References 61 publications

Tissue characterization with ballistic photons

Tissue characterization with ballistic photons

Wavelength Selection Method with Standard Deviation: Application to Pulse Oximetry

Tissue characterization with ballistic photons: counting scattering and/or absorption centres

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