title: Magnetic-resonance-imaging-coupled broadband near-infrared tomography system for small animal brain studies.
abstract: A novel magnetic-resonance-coupled broadband near-infrared (NIR) tomography system for small animal brain studies is described. Several features of the image formation approach are new in NIR tomography and represent major advances in the path to recovering high-resolution hemoglobin and oxygen saturation images of tissue. The NIR data were broadband and continuous wave and were used along with a second-derivative-based estimation of the path length from water absorption. The path length estimation from water was then used along with the attenuation spectrum to recover absorption and reduced scattering coefficient images at multiple wavelengths and then to recover images of total hemoglobin and oxygen saturation. Going beyond these basics of NIR tomography, software has been developed to allow inclusion of structures derived from MR imaging (MRI) for the external and internal tissue boundaries, thereby improving the accuracy and spatial resolution of the properties in each tissue type. The system has been validated in both tissue-simulating phantoms, with 10% accuracy observed, and in a rat cranium imaging experiment. The latter experiment used variation in inspired oxygen (FiO2) to vary the observed hemoglobin and oxygen saturation images. Quantitative agreement was observed between the changes in deoxyhemoglobin values derived from NIR and the changes predicted with blood-oxygen-level-dependent (BOLD) MRI. This system represents the initial stage in what will likely be a larger role for NIR tomography, coupled to MRI, and illustrates that the technological challenges of using continuous-wave broadband data and inclusion of a priori structural information can be met with careful phantom studies.
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA. heng.xu@dartmouth.edu
authors.forename: Heng
authors.initials: H
authors.lastname: Xu
authors.forename: Roger
authors.initials: R
authors.lastname: Springett
authors.forename: Hamid
authors.initials: H
authors.lastname: Dehghani
authors.forename: Brian W
authors.initials: BW
authors.lastname: Pogue
authors.forename: Keith D
authors.initials: KD
authors.lastname: Paulsen
authors.forename: Jeff F
authors.initials: JF
authors.lastname: Dunn
mesh_terms: D000465:Algorithms; D000818:Animals; D001185:Artificial Intelligence; D001921:Brain / Q000098:blood supply / Q000166:cytology* / Q000378:metabolism*; D001931:Brain Mapping / Q000295:instrumentation* / Q000379:methods; D003196:Computer Graphics; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006454:Hemoglobins / Q000378:metabolism*; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008297:Male; D009716:Numerical Analysis, Computer-Assisted; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation* / Q000379:methods; D013382:Subtraction Technique; D018511:Systems Integration; D014584:User-Computer Interface
chemical_list: D006454:Hemoglobins