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Copy of Photoacoustic Effect (From Principles to Applications)

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by Salomon May on 4 December 2013

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Transcript of Copy of Photoacoustic Effect (From Principles to Applications)

Presented by:
Haocheng Quan, Salomon May, Shijie Yao, Xin Liu, and Zezhou Li
12/03/2013

Nano-particles Enhanced
Photoacoustic Imaging

Introduction
History
Theory
Details about Early Cancer Detection
Applications
Common Problems
New ideas regarding PA Usage
Questions

TABLE OF CONTENTS
532 nm






Scanning mice with CA injected IV.

Evaluating results.

Comparison of Pre-Inj and Pos-Inj images and conclusions.
Procedure for in-vivo PA Imaging
Analysis of nanoparticle’s light absorbent spectra.

Determining the right laser wavelength due to spectra peaks.
Scanning phantom with different CAs and comparison.

Analyzing results of the phantom scan. Ratio of PA signal due to new CAs.

Evaluating feasibility for in-vivo imaging.
Pros and Cons
SWCNT-QSY-RGD/RAD as CAs
SWCNT-QSY-RGD
SWCNT-QSY-RAD
Photoacoustic scan Pos-Inj with Pulse Echo as Background
Photoacoustic scan Pre-Inj with Pulse Echo as Background
Pulse Echo scan of mice tumor. U87MG cells injected to the mice’s leg to form the tumor
Pros and Cons
SERS-Gd as CA
Comparison of PA signal between SERS-Gd and SWCNT-QSY-RGD
SERS-Gd
SWCNT-QSY-RGD
Photoacoustic scan Pos-Inj
Photoacoustic scan Pre-Inj
Applications
Photoacoustic Tomography/Photoacoustic microscopy
PAT/PAM
Cancer Detection

Skin Cancer
Breast Cancer
Brain Cancer
Diagnosis
--- Oxygen Tracking
Oxygen Tracking
-- Lihong Wang,Early Cancer Detection w/ Photoacoustic Tomography,Youtube
Monitor
E.D.Montigny,Photoacoustic Tomography : Principles and applications,2011 Ecole Polytechnique de Montreal
Cancer Detection
Single Wall Nanotube SWNT

SERS Gd Nanoparticles
By Using Contrast Agent
Combine MRI, PAT and Raman with the same agents.

Three-modality nanoparticles

Generally,
MRI works good in relative large region
Raman has a really good resolution
PAT can bridge the gap.
MRI, PAT&Raman
Identification of atherosclerotic plaques
M.F.Kircher,A brain tumor molecular imaging strategy using a new triple-modality MRI-photoacoustic-Raman nanoparticle, Nature Medicine Vol.18, 2012
Tissue Damage
Photobleaching
Toxicity

Common Problems
Problems may be:
The photochemical destruction of a dye (photoacoustics).
Complicate the measurement of PA signal

Loss of activity caused by photobleaching can be controlled---
a) reducing the intensity or time-span of light exposure,
b) increasing the concentration of nanoparticles,
c) reducing the frequency and thus the photon energy of the input light,
d) more robust nanoparticles that are less prone to bleaching (e.g. SERS Gd, SWCNT-QSY-ICG).
Photobleaching
Tissue Damage
Nanoparticles have much larger surface area to unit mass ratios which in some cases may lead to greater pro-inflammatory effects.

May translocate from the site of deposition to distant sites such as the blood and the brain. Besides lungs, the effects of nanoparticles on brain, blood, liver, skin and gut also need a closer investigation.

A new branch of toxicology raised up---Nanotoxicology. 
Toxicity
Photoacoustic Effect
From Principles to Application
THERMAL INJURY!

Laser energy-->temp rises-->tissue proteins burnt
Exposure time
Laser pulses---additive thermal effects
The principal thermal effects of laser exposure depend upon the following factors:
The absorption and scattering coefficients of the tissues at the laser wavelength.
Irradiance or radiant exposure. 
Duration of the exposure and pulse repetition characteristics. 
Extent of the local vascular flow.
Size of the area irradiated.
Alexander Graham Bell
Photophone
History
Physical Mechanisms Behind the Photoacoustic Effect
Prospects of PAT
Efficiency? Gold nanocages
1. Tunable NIR-absorbing Contrast Agent
Endogenous contrast
Exogenous contrast
2. Combining Anatomical & Functional Imaging
3. Multi-scale in-vivo Imaging

4. Melanoma Detection
Photoacoustic endoscope

Combined with other imaging modalities

Imaging biological events(photoacoustic tomography of gene expression,simultaneous photoacoustic and thermoacoustic tomography of the breast,、photoacoustic and thermoacoustic tomography of the brain)

photoacoustic tomography of metabolic rate of
oxygen
And then there will be more…
Efficiency?
Information?
Resolution?
Real-world Application?
Xia, Y. N. Acc. Chem. Res. 2011, 44, 914
Proc. IEEE 2008, 96, 481
Wang, L. H. V. Science, 2012, 335, 1458
Wang, L. H. V. Nat. Biotech. 2006, 24, 848
Wang, L. H. V. Nat. Prot. 2007, 2, 79

development of PA techniques
development of the laser in the 1960s

indirect gas-phase cell type of PA detection in the 1970s and 1980s

latter direct detection approach

investigated for biomedical imaging in the mid-1990s and the first images began to appear thereafter

obtained the first truly compelling in vivo images in the early to mid-2000s
--From Principles to Applications
spectrophone
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