Three-dimensional reconstruction in free-space whole-body fluorescence tomography of mice using optically reconstructed surface and atlas anatomy

Abstract

We present a 3-D image reconstruction method for free-space fluorescence tomography of mice using hybrid anatomical prior information. Specifically, we use an optically reconstructed surface of the experimental animal and a digital mouse atlas to approximate the anatomy of the animal as structural priors to assist image reconstruction. Experiments are carried out on a cadaver of a nude mouse with a fluorescent inclusion (2.4-mm-diam cylinder) implanted in the chest cavity. Tomographic fluorescence images are reconstructed using an iterative algorithm based on a finite element method. Coregistration of the fluorescence reconstruction and micro-CT (computed tomography) data acquired afterward show good localization accuracy (localization error 1.2+/-0.6 mm). Using the optically reconstructed surface, but without the atlas anatomy, image reconstruction fails to show the fluorescent inclusion correctly. The method demonstrates the utility of anatomical priors in support of free-space fluorescence tomography.

Figure 1

(a) Experimental setup and schematic drawings of (b) the galvo scanner and (c) the rotation stage: 1, the CCD camera; 2, the lens; 3, the white-light LED; 4, the filter wheel; 5, the rotation stage; 6, the galvo scanner; and 7, the laser diode assembly.

Figure 2

The 3-D surface contour of the animal (central) reconstructed from the white-light reflectance images from multiple acquisition angles (peripheral) using an inverse Radon transform. The area marked by a double-arrow on the surface contour represents the source and detector positions (shown as red and blue markers respectively), which define the ROI (22⩽z⩽30 mm) in reconstruction. (Color online only.)

Figure 3

Rendering of (a) the optically reconstructed animal surface and (b) the anatomical micro-CT data show good registration with each other in (c). Using the same parameters of spatial transformation as in (c), the FDOT reconstruction result (the FWHM matrix, shown as red in the online color figure) is registered with the micro-CT data in (d). Also shown in (d) is the internal structures obtained from the micro-CT data, in which the two ends of the glass capillary containing the fluorophore are marked by arrows.

Figure 4

Normalized FDOT result (i.e., the FWHM matrix, shown in color) registered to anatomical micro-CT images within the ROI (22⩽z⩽30 mm). In the anatomical images, the bright circle inside the chest cavity is the cross section of the glass capillary containing the fluorophore, which forms the fluorescent inclusion in the animal. The result on the left panel is reconstructed from the MOBY anatomy; that on the right is from the same animal surface but assuming homogeneity internally.

Figure 5

Plots of the normalized maximum in-plane intensity (broken line), the normalized rms error (dash-dotted line), and the localization error (solid line) versus the slice position within the ROI (22⩽z⩽30 mm). The dotted lines at the bottom are the ranges of coverage along the z axis of the illumination sources and the detectors (shorter and longer lines, respectively), which define the ROI. Note that the image quality close to the central slices is better (smaller rms and localization errors) and gradually degrades as it approaches the boundaries of the ROI.