Measurements of optical properties of high-density media

Zaccanti, Giovanni; Bianco, Samuele Del; Martelli, Fabrizio

doi:10.1364/ao.42.004023

Cited by 129 publications

(95 citation statements)

References 15 publications

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“…In other words, the scattering cross section in the high density medium decreases relative to the single particle (Mie) scattering cross section. This effect was already observed by Zaccanti et al [11] in optical transmission measurements of Intralipid, but also has been investigated by many others, e.g. see Refs [10,22,23].…”

Section: / Optics Express 3891supporting

confidence: 64%

“…In this case the scattering coefficient µ s does not follow the linear relation µ s = Cσ s , but instead the Mie scattering cross section σ s depends in a complex way on particle concentration C and therefore the relation µ s = Cσ s (C) holds. As already shown in other light scattering experiments [10,11] dependent scattering leads to a reduction in the scattering rate can thus lead to a decrease of the OCT signal attenuation.…”

Section: Introductionsupporting

confidence: 67%

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Multiple and dependent scattering effects in Doppler optical coherence tomography

et al. 2010

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Doppler optical coherence tomography (OCT) is a technique to image tissue morphology and to measure flow in turbid media. In its most basic form, it is based on single (Mie) scattering. However, for highly scattering and dense media multiple and concentration dependent scattering can occur. For Intralipid solutions with varying scattering strength, the effect of multiple and dependent scattering on the OCT signal attenuation and Doppler flow is investigated. We observe a non-linear increase in the OCT signal attenuation rate and an increasingly more distorted Doppler OCT flow profile with increasing Intralipid concentration. The Doppler OCT attenuation and flow measurements are compared to Monte Carlo simulations and good agreement is observed. Based on this comparison, we determine that the single scattering attenuation coefficient µ s is 15% higher than the measured OCT signal attenuation rate. This effect and the distortion of the measured flow profile are caused by multiple scattering. The non-linear behavior of the single scattering attenuation coefficient with Intralipid concentration is attributed to concentration dependent scattering.

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Section: / Optics Express 3891supporting

confidence: 64%

Section: Introductionsupporting

confidence: 67%

Multiple and dependent scattering effects in Doppler optical coherence tomography

et al. 2010

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“…The obtained values are close to the values estimated by MIE theory or values reported in literatures (Vanstaveren et al, 1991;Flock et al, 1992;Zaccanti et al, 2003), as seen in Table 1 and Figure 6. For comparison, fitting result from Faber's model is also presented in Table 1 (Faber et al, 2004).…”

Section: Animal Model Of Colon Cancersupporting

confidence: 90%

Combining Optical Coherence Tomography with Fluorescence Imaging

Yuan¹,

Chen²

2010

Advances in Lasers and Electro Optics

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“…Similarly, as the probability of multiple scattering events increases even further (i.e. for very high N), light is increasingly deflected away from the detector, and can be described with diffusive Scientific RepoRts | 6:38828 | DOI: 10.1038/srep38828 approximations (the so-called photon diffusion limit) 12,13 . Figure 1C shows a typical OD curve for Escherichia coli grown in rich media, with the single and multiple scattering regimes indicated.…”

mentioning

confidence: 99%

General calibration of microbial growth in microplate readers

Stevenson

McVey

Clark

et al. 2016

Preprint

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Optical density (OD) measurements of microbial growth are one of the most common techniques used in microbiology, with applications ranging from studies of antibiotic efficacy to investigations of growth under different nutritional or stress environments, to characterization of different mutant strains, including those harbouring synthetic circuits. OD measurements are performed under the assumption that the OD value obtained is proportional to the cell number, i.e. the concentration of the sample. However, the assumption holds true in a limited range of conditions, and calibration techniques that determine that range are currently missing. Here we present a set of calibration procedures and considerations that are necessary to successfully estimate the cell concentration from OD measurements.Bacteria and yeast are widely studied microorganisms of great economic, medical and societal interest. Much of our understanding of bacterial and yeast life cycles stems from monitoring their proliferation in time and the most routine way of doing so is using optical density (OD) measurements. The applications of such measurements range from routine checks during different cloning techniques 1 ; through studying cellular physiology and metabolism 2,3 ; to determining the growth rate for antibiotic dosage 4,5 ; and monitoring of biomass accumulation during bio-industrial fermentation 6 . Here we introduce a set of calibration techniques that take into account the relevant parameters affecting OD measurements, including at high culture densities, in a range of conditions commonly used by researchers.OD measurements have become synonymous with measurements of bacterial number (N) or concentration (C), in accordance with the Beer-Lambert law. However, OD measurements are turbidity measurements 7,8 , thus the Beer-Lambert law can be applied, with some considerations, only for microbial cultures of low densities. OD measurements in plate readers, increasingly used for high-throughput estimates of microbial growth, operate predominantly at higher culture densities where OD is expected to have a parabolic dependency on N 8 . Additionally, the proportionality constants (either in low or high density regimes) strongly depend on several parameters, for example cell size, which need to be included in robust calibration techniques. Yet, these techniques, essential when using OD measurements for quantitative studies of microbial growth, including growth rates, lag times and cell yields, have thus far not been established.The Beer-Lambert law (Supplementary Note 1) assumes that light is only absorbed to derive OD ~ C, which is true if the light received by the detector of a typical spectrophotometer is the light that did not interact with the sample in any way 7,9 . In general, when microbial cells are well dispersed in the solution (for the cases where N is small, i.e. single scattering regime) and the geometry of the spectrophotometer is suitable, the Beer-Lambert law is a good approximation for turbidity measurements, and N (or C) is ~...

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Measurements of optical properties of high-density media

Cited by 129 publications

References 15 publications

Multiple and dependent scattering effects in Doppler optical coherence tomography

Multiple and dependent scattering effects in Doppler optical coherence tomography

Combining Optical Coherence Tomography with Fluorescence Imaging

General calibration of microbial growth in microplate readers

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