Optical Imaging (Basics) (BIOE 498/598 DP) 03/31/2014. Outline. Understand light Light propagation in biological tissues Fluorescence, phosphorescence… Importance of NIR Tissue oximetry Exogenous contrast agents Imaging with light Therapy with light Dual modality systems.
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(BIOE 498/598 DP)
Comparative energy spectra and location of non-ionizing light in the electromagnetic spectrum
2008 Nobel in Chemistry Awarded for“in vivo Optical Contrast Agent”
-- Optical contrast
-- In vivo imaging
In this equation, A is a function of refractive index, µa and µs are the absorption and scattering coefficients of biological tissues, respectively.
Energy diagram for photo-physical events related to absorption and fluorescence. The fluorescence lifetime is the average time that a population of fluorophores remains in the excited sate (S1-S3) after absorption of photons
Scattered and reflected
Scattered and absorbed
mal, msl, g
Scattered and transmitted
The NIR window is ideally suited for in vivo imaging because of minimal light absorption by hemoglobin (<650 nm) and water (>900 nm).
Near infrared (NIR) emission by NIR excitation is observed using a NIR-NIR system. Due to weaker scattering and absorption, NIR light can penetrate deeper into/from tissues. In contrast, excitation light in the visible (VIS) region cannot reach the imaging target in tissues in the conventional VIS-VIS imaging. In upconversion (NIR-VIS) imaging, although NIR excitation light can reach its target in tissues, only a weak VIS emission can be obtained.
Schematic diagram of how scattered, absorbed, or re-emitted photons can be used to obtain diagnostic information in living tissue.
Hematopoesis from a single stem cell
Cao et al. Shifting foci of hematopoiesis during reconstitution from single stem cells. Proc Nat AcadSci USA. 2004;101(1):221-226.
Optically labeled stem cells can be seen singly in vivo in bone marrow
Proc Natl AcadSci 2009 from University of Tsukuba, Japan and Univ. of Michigan Medical School.
Real-time imaging of labeled probes in 1-10 cc whole blood
(Benaron et al, 2011 Project with Stanford Stem Cell Center, Sloan-Kettering Cancer Center)
(Top) Clinical IBMI system installed for breast cancer surgery at the University Medical Center, Groningen, Netherlands. (Bottom) Real-time visualization of ovarian cancer surgery on a patient injected with a fluorescent folate-targeting probe (from van Dam G., et. al. Nature Medicine 2011).
Three-dimensional rendering of bones, skin and lung based on XCT data and FMT reconstruction of a K-ras mouse with lung tumors.
Nature Methods 29(6); 615-620 (2012).
Optical imaging geometries for fluorescence detection demonstrating (a) Planar Reflectance, (b) Diffuse Reflectance and (c) Diffuse Transillumination with multiple source (S1-S4) and detector (D1-D4) locations.
Example planar reflectance imaging system setup for detection of fluorescence in mouse cancer model. (b) Bright field and (c) fluorescence images of mouse after intravenous administration of tumor-targeted molecular probe in mouse with subcutaneous tumor (arrow).
Ntziachristos, Ripoll et al. 2005)
Carotid endarterectomy specimen in white light (left), near-infrared fluorescence signal before (autofluorescence, middle) and after incubation with MMP-sensitive activatableprobe (MMPSense, right) within the IVIS Spectrum.
Isotope and fluorochrome reporters can be used interchangeably for nonspecific and targeted agents; however, fluorochromes can also be used to make activation-sensitive agents for read-out of protein function.