Optical Imaging Techniques

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Questions and Answers

What is the primary function of the laser in the SLOT setup?

To project the sample properties along one line (correct)

To filter out unwanted light

To detect fluorescence

To scatter light through the specimen

What is the purpose of the filter in the SLOT setup?

To project the sample properties

To amplify the laser signal

To detect fluorescence

To block unwanted light (correct)

What is the advantage of using a scanning laser optical tomograph?

It is less efficient than traditional CT scans

It can only be used for small specimens

It can image specimens in 3D with high efficiency (correct)

It can only detect absorption properties

What is the relationship between the SLOT setup and traditional CT scans?

They project sample properties in the same way Signup and view all the answers

What is the significance of the paper by R.-A. Lorbeer et al.?

It demonstrated the efficiency of 3D fluorescence microscopy Signup and view all the answers

What is the purpose of the xy-scanner in the SLOT setup?

To move the laser beam Signup and view all the answers

What is the significance of the photophone sketched by Bell?

It was the first device to convert sound into light Signup and view all the answers

What is the advantage of using fluorescence detection in the SLOT setup?

It is more specific to certain biomarkers Signup and view all the answers

What is the unit of measurement for the optical absorption in figure (A) and (B)?

cm Signup and view all the answers

What is the advantage of using ICG-PEG in photoacoustic angiography?

Removing speckles Signup and view all the answers

What is the purpose of subtracting image (A) from image (B) to obtain image (C)?

To calculate the differential absorption Signup and view all the answers

What is the scale of the spatial resolution in the high-resolution image?

60 mm Signup and view all the answers

What is the detection limit of the photoacoustic angiography technique?

fmol Signup and view all the answers

What is the purpose of the open-skull photo in figure (D)?

To validate the in vivo results Signup and view all the answers

What is the primary mechanism of photoacoustic tomography (PAT)?

Laser absorption in the specimen leading to thermoelastic expansion Signup and view all the answers

What is the role of the transducer in photoacoustic tomography?

To detect the sound wave emitted by the specimen Signup and view all the answers

What is the function of the conical lens in the Reflection-mode Dark-field Confocal Photoacoustic Microscopy setup?

To provide annular illumination with a dark center Signup and view all the answers

What is the purpose of the motor driver and translation stages in the setup?

To move the sample during imaging Signup and view all the answers

What is the purpose of embedding the mouse in a water tank in the PAT experiment?

To provide a medium for acoustic wave propagation Signup and view all the answers

What is the benefit of using optoacoustics in the stimulation of whiskers experiment?

It measures blood dynamics and saturation in the brain Signup and view all the answers

What is the benefit of multispectral optoacoustic tomography?

It enables the estimation of the distribution of a given substance by unmixing images at several wavelengths Signup and view all the answers

What is the unit of measurement on the x-axis of the image in the stimulation of whiskers experiment?

Centimeters Signup and view all the answers

What is the purpose of the heater and temperature controller in the setup?

To control the temperature of the sample Signup and view all the answers

What is the advantage of using gold nanoparticles in photoacoustic imaging?

They have a distinct spectral dependence of absorption Signup and view all the answers

What is the significance of the 'Differential absorption' label in the stimulation of whiskers experiment?

It indicates the difference in laser absorption between left and right stimulation Signup and view all the answers

In which journal was the study on stimulation of whiskers using optoacoustics published?

Nature Biotech Signup and view all the answers

What is the purpose of the ultrasonic transducer in the setup?

To detect the ultrasound signal from the sample Signup and view all the answers

What is the benefit of using Hb and HbO2 in photoacoustic imaging?

They have different spectral dependences of absorption Signup and view all the answers

What is the ultimate goal of photoacoustic tomography (PAT)?

To image the specimen's functional parameters Signup and view all the answers

What is the purpose of the photodiode in the setup?

To detect the reflected light from the sample Signup and view all the answers

What is the primary function of the VIPA in the setup from Scarcelli et al?

To act as a highly dispersive element, similar to a tilted etalon or Fabry Perot Signup and view all the answers

Which part of the human lens was found to be harder in older lenses?

A broader part Signup and view all the answers

What is the limitation of the Brillouin measurements?

The values are acquired at one frequency and deducing the mechanic properties for a different regime Signup and view all the answers

What is the significance of the paper by Scarcelli et al?

It demonstrated the use of VIPA in resolving spectral signals Signup and view all the answers

What is the characteristic of the central part of the lens at approximately 1mm depth?

It is harder than the rest of the lens Signup and view all the answers

What is the trend observed in the overall stiffness of human lenses with age?

It remains the same Signup and view all the answers

What is the purpose of the study by Scarcelli et al?

To measure the stiffness of human lenses using Brillouin microscopy Signup and view all the answers

What is the significance of the results from Brillouin microscopy in living human eyes?

They provide valuable insights into the mechanical properties of the lens Signup and view all the answers

Study Notes

CT with Visible Light: Scanning Laser Optical Tomograph (SLOT)

SLOT scans a laser through a specimen to project sample properties (absorption and scattering) along one line, similar to CT scans with X-rays.
The setup includes a laser, xy-scanner, photodetector, and filter.

Photoacoustic Tomography (PAT)

PAT involves illuminating a specimen with a laser, which leads to thermoelastic expansion and subsequent sound waves that are detected and used for image reconstruction.
A demonstration of PAT involved illuminating the head of a living mouse, embedded in a water tank, with a laser, and detecting the sound waves with a transducer.

Optoacoustics in Living Animals

Stimulation of whiskers in a living mouse was measured by optoacoustics, showing blood dynamics and saturation in the brain.
Photoacoustic angiography was demonstrated in vivo (in rats) through the skull, with high resolution and sensitivity.

Reflection-Mode Dark-Field Confocal Photoacoustic Microscopy

This technique uses a tunable laser, photodiode, and ultrasonic transducer to image samples.
The setup includes a conical lens, sample holder, and heater and temperature controller.

Volumetric Imaging of Rat Microvasculature In Vivo

Maximum amplitude projections of rat microvasculature were obtained using optoacoustic imaging.

Molecular Imaging and Spectral Imaging (Multispectral Optoacoustic Tomography)

Spectral imaging involves estimating the distribution of substances by unmixing images at several wavelengths based on their spectral dependence of absorption.
Examples of substances imaged include hemoglobin (Hb), oxygenated hemoglobin (HbO2), gold nanorods (AuNR), and AF750.

Brillouin Microscopy

Brillouin microscopy resolves spectral signals by measuring the Brillouin shift, which is related to the stiffness of materials.
The technique was used to measure the stiffness of eye lens tissue, showing that the central part of the lens is harder than the rest.
Results in living human eyes showed that the overall stiffness of the lens does not change with age, but a broader part of the lens becomes harder.

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Description

Learn about Scanning Laser Optical Tomograph (SLOT) and Photoacoustic Tomography (PAT), two optical imaging techniques used to reconstruct images of specimens.