Video-rate near infrared tomography to image pulsatile absorption properties in thick tissue

Abstract

A high frame-rate near-infrared (NIR) tomography system was created to allow transmission imaging of thick tissues with spectral encoding for parallel source implementation. The design was created to maximize tissue penetration through up to 10 cm of tissue, allowing eventual use in human imaging. Eight temperature-controlled laser diodes (LD) are used in parallel with 1.5 nm shifts in their lasing wavelengths. Simultaneous detection is achieved with eight high-resolution, CCD-based spectrometers that were synchronized to detect the intensities and decode their source locations from the spectrum. Static and dynamic imaging is demonstrated through a 64 mm tissueequivalent phantom, with acquisition rates up to 20 frames per second. Imaging of pulsatile absorption changes through a 72 mm phantom was demonstrated with a 0.5 Hz varying object having only 1% effect upon the transmitted signal. This subtle signal change was used to show that while reconstructing the signal changes in a tissue may not be possible, image-guided recovery of the pulsatile change in broad regions of tissue was possible. The ability to image thick tissue and the capacity to image periodic changes in absorption makes this design well suited for tracking thick tissue hemodynamics in vivo during MR or CT imaging.

Chemical Imaging with a Solid-State near Infrared Spectrometer Based on a Digital Micro-Mirror Array Device Coupled with Hadamard Transform Spectroscopy

“…Applications of chemical imaging can be found in a wide variety of industries and sciences, including methods to quantify the concentration and assess the distribution of chemical components within matrices of pharmaceutical (Amigo and Ravn 2009;Cairos et al 2009;Gendrin, Roggo, and Collet 2008;Gerich, Dubois, and Kidder 2010;Lopes and Wolff 2009;Maurer and Leuenberger 2009), biomedical (Kalasinsky and Lewis 2004;Lee et al 2010;Li et al 2009), and polymer science (De Biasio et al 2010;Furukawa et al 2007;Gosselin, Rodrigue, and Duchesne 2008;Gosselin et al 2009) origin. For such an analysis, a spectrum is collected at each pixel location of the image and the chemical composition is determined for each pixel from an analysis of the resulting spectrum.…”

Endoscopic diffuse optical tomography for esophagus: Initial investigation

“…Differ from the breast cancer diagnosis, brain functional imaging focuses on the dynamic response to the purposive stimulus, frequency-domain DOT, CW measurement, and linear reconstruction methods are widely used to reduce the time of the imaging [5] [6] [7]. A video-rated imaging system has been developed for the fast imaging [8].…”

Rapid magnetic resonance-guided near-infrared mapping to image pulsatile hemoglobin in the breast

“…A near-IR (NIR) tomography system with spectral-encoded sources near 785 nm waveband was built, and its capacity to reveal the small-scale pulsatile variations of hemoglobin within the human breast was analyzed [1,2]. In this Letter, the system was incorporated into a magnetic resonance (MR) scanner with online finger pulse oximeter (PO) plethysmogram, and the temporal signatures of the human breast were recorded and analyzed with frequency synchronized to the PO signal.…”

“…The NIR sources were seven 785 nm single-mode laser diodes (Hitachi HL-7851G). The source locations were spectrally encoded into the signal, by having a different center wavelength at each laser diode, by about 1:5 nm interval [1,2]. These were set and maintained by current and temperature control.…”

“…After calibration with a slab-shaped homogeneous phantom measurement, the data were reconstructed using a region-based reconstruction algorithm [1,9,10]. This algorithm minimizes the difference of the measured data, Φ M , and the calculated data, Φ C , from the forward model $${\chi }^2=\sum _{i=1}^{\mathrm{NM}}{({\Phi }_i^C-{\Phi }_i^M)}^2,$$ where i is the index for each source-detector pair and NM is the total number of measurements.…”