Tomographic image reconstruction from optical projections in light-diffusing media

Abstract

The recent developments in light generation and detection techniques have opened new possibilities for optical medical imaging, tomography, and diagnosis at tissue penetration depths of ~10 cm. However, because light scattering and diffusion in biological tissue are rather strong, the reconstruction of object images from optical projections needs special attention. We describe a simple reconstruction method for diffuse optical imaging, based on a modified backprojection approach for medical tomography. Specifically, we have modified the standard backprojection method commonly used in x-ray tomographic imaging to include the effects of both the diffusion and the scattering of light and the associated nonlinearities in projection image formation. These modifications are based primarily on the deconvolution of the broadened image by a spatially variant point-spread function that is dependent on the scattering of light in tissue. The spatial dependence of the deconvolution and nonlinearity corrections for the curved propagating ray paths in heterogeneous tissue are handled semiempirically by coordinate transformations. We have applied this method to both theoretical and experimental projections taken by parallel- and fan-beam tomography geometries. The experimental objects were biomedical phantoms with multiple objects, including in vitro animal tissue. The overall results presented demonstrate that image-resolution improvements by nearly an order of magnitude can be obtained. We believe that the tomographic method presented here can provide a basis for rapid, real-time medical monitoring by the use of optical projections. It is expected that such optical tomography techniques can be combined with the optical tissue diagnosis methods based on spectroscopic molecular signatures to result in a versatile optical diagnosis and imaging technology.

Diffuse optical imaging of brain activation: approaches to optimizing image sensitivity, resolution, and accuracy

“…This is the basis of image reconstruction algorithms in which an image of Dl a (i.e., the vector x) can be obtained from a set of measurements (i.e., the vector y) through inversion of the matrix A (i.e., the effective pathlengths L i,j ). While several advanced imaging algorithms have been developed-including analytic diffraction tomography approaches (Cheng and Boas, 1998;Li et al, 1997;Matson and Liu, 1999;Schotland, 1997), perturbation approaches (Arridge and Schweiger, 1995;Barbour et al, 1995;O'Leary et al, 1995;Schotland et al, 1993;Yao et al, 1997), the Taylor series expansion approach (Jiang et al, 1996;Paulsen and Jiang, 1995), gradient-based iterative techniques (Arridge and Schweiger, 1998), elliptic systems method (ESM) (Gryazin et al, 1999;Klibanov et al, 1997), and Bayesian conditioning (Barnett et al, 2003;Eppstein et al, 1999) -the most widely used methods for diffuse optical functional brain imaging incorporate a semiinfinite forward model (Kienle and Patterson, 1997a;Patterson et al, 1989) and either backprojection (Colak et al, 1997;Franceschini et al, 2000;Maki et al, 1995, Walker et al, 1997 or perturbation approaches (Arridge, 1999).…”

Concurrent MRI and diffuse optical tomography of breast after indocyanine green enhancement

“…Thus far, DOT images of absorbing and scattering objects embedded in tissue-like media have been produced (2,(25)(26)(27)(28)(29)(30) by using phantoms. The experimental certainty of the phantom contrast makes the evaluation of the technique straightforward.…”

Interstitial diffuse radiance spectroscopy of gold nanocages and nanorods in bulk muscle tissues

“…Concentrated bare Au NR solution (6.2×10 13 NPs/ mL, 735 nm resonance, 10 nm diameter, ~33 nm length) was used as is (NR-100) and for volume dilution to prepare NR-10 (6.2×10…”

“…In their seminal papers, Feng et al 12 and Colak et al 13 offered a way of treating localized inclusions of absorbers or scatterers in turbid media via the perturbation approach.…”