Fluorescence-enhanced three-dimensional lifetime imaging: a phantom study.

Near-infrared fluorescence optical imaging has the unique opportunity of differentiating diseased lesions from normal lesions based upon environmentally indicated changes in the lifetime of a fluorescent imaging agent. In this paper, we demonstrate three-dimensional lifetime tomography using the gradient-based penalty modified barrier function with simple bounds truncated Newton with trust region method to reconstruct lifetime maps in a clinically relevant, single breast-shaped ( approximately 1081 cm(3)) phantom from point-frequency-domain photon migration measurements at 100 MHz. A reverse differentiation technique is used to calculate the gradients.

Fluorescence-enhanced optical tomography of a large tissue phantom using point illumination geometries.

We demonstrate fluorescence-enhanced optical imaging of single and multiple fluorescent targets within a large (approximately 1081 cm3) phantom using frequency-domain photon migration measurements of fluorescence collected at individual points in response to illumination of excitation light at individual points on the boundary. The tissue phantom was filled with a 1% lipid solution with and without 0.01 microM Indocyanine Green (ICG) and targets consisted of vials filled with the 1% lipid containing 1-2.

Evaluation of anatomical structure and non-uniform distribution of imaging agent in near-infrared fluorescence-enhanced optical tomography.

To date, the assessment of fluorescence-enhanced optical imaging has not been performed owing to (i) the lack of tools necessary for objective assessment of image quality (OAIQ), and (ii) the difficulty to test an untested diagnostic contrast agent in patient studies. Herein, we focus upon the development of a framework for OAIQ which includes a model to simulate both natural tissue heterogeneity as well as heterogeneous distribution of a molecularly targeted fluorophore. Specifically, we use a novel tomographic algorithm previously developed and validated in our laboratory (Roy and Sevick-Muraca, IEEE Trans.

Fluorescence-enhanced optical tomography using referenced measurements of heterogeneous media.

A three-dimensional image reconstruction for fluorescence-enhanced frequency-domain photon migration (FDPM) measurements in turbid media is developed and investigated for three different simulated measurement types: 1) absolute emission measurement, or emission measurements of phase and amplitude attenuation made for a given incident point source of excitation light; 2) referenced emission measurements made relative to an excitation measurement conducted at a single reference point away from the incident source; and 3) referenced emission measurements made relative to the excitation measurement conducted at identical points of detection. The image reconstruction algorithm employs a gradient-based constrained truncated Newton (CONTN) method which implements a bounding parameter, which can be used to govern the level of contrast used to discriminate tissue volumes from heterogeneous background tissues. Reverse differentiation technique is used to calculate the gradients.

Influence of the refractive index-mismatch at the boundaries measured in fluorescenceenhanced frequency-domain photon migration imaging.

Over the past decade, developments towards near-infrared (NIR) optical tomography involve the recovery of interior optical maps from boundary measurements using the first principles of light propagation models. The refractive-index mismatch parameter in the boundary condition of the light propagation model, namely the diffusion equation, can significantly impact model prediction of measurements and therefore image recovery. In this contribution, the influence of refractive-index mismatch parameter between predictions and referenced measurements of fluorescence-enhanced frequency-domain photon migration (FDPM) are established; its greater influence on emission over excitation predictions are demonstrated, and the methods to accurately determine refractive index mismatch parameter from basic principles are reviewed.