• Fluorescence mediated tomography: A development of fluorescence reflectance imaging that captures images from multiple angles. Subsequent computational analysis calculates the point of origin of the fluorescent light in three dimensions.
• Fluorescence lifetime imaging: The length of time that a fluorophore remains in an excited state can provide additional information. For example, fluorescence resonance energy transfer usually leads to a decrease in the length of time the donor fluorophore is excited. Measuring the lifetime of intrinsic fluorophores can provide more information either about the exact fluorophore or its local environment.
• Protease-activated probes: Fluorophores are less effective at high local concentrations. Many fluorophores fused to a cleavable substrate generate a high local concentration, and therefore weak fluorescence. Upon substrate cleavage the fluorophore concentration drops and fluorescence increases.
• Diffuse optical tomography: Diffuse light is propagated through tissue at multiple angles and captured, subsequent computational analysis determines the optical properties of the tissue in three dimensions. Provides good tissue penetration, haemoglobin is easily imaged, but limited resolution and contrast agents.
• Photoacoustic microscopy: Absorption of light by tissue can lead to the emission of sound waves that can be recorded and analysed. Provides good penetration and ability to detect intrinsic signals. Still being developed, difficult to detect exogenous contrast agents, resolution limited to the cellular level.
• Optical coherence tomography: Coherence between light reflected from the sample and a reference signal is measured. Greater than mm penetration, ability to detect intrinsic signals, good resolution and three-dimensional information. Problems detecting exogenous contrast agents.
• Photoacoustic flow cytometry: Similar to flow cytometry except that circulating cells are analysed in vivo using blood flow in small vessels to generate a flow of cells through the imaging path. Many anatomical sites can be imaged. Either conventional reflectance, fluorescence or photoacoustic measurements can be made. Can analyse cells in circulation with sub-micron resolution. Very complicated to set up.
• Laser scanning endoscopes: Modified objectives with a narrow 1–2 mm diameter enable a laser scanning microscope to be used endoscopically. High resolution images of internal organs can be obtained.
Reference:
Illuminating the metastatic process by Erik Sahai , Nature Reviews cancer, volume 7, October 2007
No comments:
Post a Comment