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There have been three basic approaches to optical tomography since the early s: diffraction tomography, diffuse optical tomography and optical coherence . There have been three basic approaches to optical tomography since the early s: diffraction tomography, diffuse optical tomography and.
Fujimoto Author information. Keywords: Optical coherence tomography , Biomedical imaging , Microscopy , Interferometry , Femtosecond optics.
Published: received: July 29, Released: February 03, accepted: - [Advance Publication] Released: - corrected: -. Article overview. References This article reviews the principles and applications of OCT. Already have an account? Login in here. The Review of Laser Engineering. Journal home Journal issue Special issue About the journal. Laser Review.
Optical Coherence Tomography Find more supplier details at the end of the encyclopedia article , or go to our List of suppliers for optical coherence tomography instruments and components. Optical coherence tomography leverages this concept by replacing the mirror in the sample arm with the sample to be imaged Figure 2. Find more supplier details at the end of the encyclopedia article , or go to our. Figure 6. Although scans need to be interpreted carefully due to the intrinsic limitations and artifacts of this technology, OCT-A has emerged as one of the major advances in medical retina.
Fujimoto Author information. The incident light is then converted into photo-current by optical detectors, which are square law intensity detection devices. The generated photo-current is proportional to the time average of the incident electric field multiplied by its complex conjugate and is given by:. The first two terms on the right hand side of the equation represent the DC component of the current and self interference.
The final term in this equation accounts for the interference between the reference and sample electric fields and is used to extract the axial depth profile or structural information in OCT. When simplified, the AC component of the photocurrent can be written as follows:.
Various spectral slices of the combined broadband output from the reference and sample arms are spatially encoded using a collimator, diffraction grating, and a linear detector array. Resampling of the data obtained from the linear detector array is performed in order to correct for the nonlinear spatial mapping of wavenumbers.
After resampling and subtraction of the DC background, the depth profile structural information can be obtained by performing the inverse Fourier transform operation. A cone of collimated beams of different wavelengths emerges from the grating plane and each spectral slice is mapped to an individual pixel in the linear CCD array.
The resulting spectrum shown is then inverse Fourier transformed to provide depth-dependent scattering information. In swept-source OCT, the broad bandwidth optical source is replaced by a rapid-scanning laser source.
By rapidly sweeping the source wavelength over a broad wavelength range, and collecting all the scattering information at each wavelength and at each position, the composition of the collected signal is equivalent to the spectral-domain OCT technique. Collected spectral data is then inverse Fourier transformed to recover the spatial depth-dependent information. Swept-source OCT systems are advantageous for their extremely fast scan rates, on the order of 50, to several MHz axial scans per second. In FD-OCT systems, the interference signal is distributed and integrated over many spectral slices, and is inverse Fourier transformed to obtain the depth-dependent reflectivity profile of the sample.
click However, in TD-OCT systems, the interference signal of the broadband fields is integrated over time as the reference path delay is modulated in a periodic manner with constant speed to obtain the same information. Magnetomotive optical coherence tomography MM-OCT is a novel extension of OCT for imaging a distribution of magnetic molecular imaging agents in biological specimens.
In the MM-OCT system, the magnetic field is generated using an electromagnet and in vivo imaging is performed while the specimen is placed within the gradient of the magnetic field. Usually, a ring-shaped, water-cooled solenoid is used and the sample is placed such that the z-axis of A-scans is along the central axis or open bore of the solenoid ring.
The gradient of the magnetic field applies force on the magnetic nanoparticles MNPs resulting in their motion.