Imaging of superficially grown GFP-expressing tumors. (a) A white light image of the mouse. The two s.c. tumors are shown, indicated by red arrows. (b) Image obtained with epi-illumination showing bright signals from the tumors and strong skin autofluorescence. (c) Transillumination image obtained by superimposing all 33 sources used during the FPT imaging, demonstrating CCD shot-noise limited detection. (d–f) Coronal tomographic slices obtained from three different depths. The reconstructed images (in color) were overlaid on the white light image after a threshold was applied at 50% of the maximum reconstructed value. No activity is present at 6-mm depth (d). Conversely, the tumors are reconstructed with good size definition and contrast at 2-mm (e) and 1-mm (f) depth.

Tumor growth observed by FPT (a) and x-ray CT (b) studies. The FPT volume calculations were obtained by integrating all voxels above a threshold of twice the mean of the reconstructed values at a volumetric region of interest around the reconstructed tumor image.

Quantification accuracy for reconstructions of GFP-expressing (a) and YFP-expressing (b) tumor cells (human glioma cell line) contained in thin capillary glass tubes inserted in the esophagus of killed nude female mice and obtained postmortem. The black circles show the reconstructed fluorescence values, which were fitted with a linear relation (gray line). Insets show a coronal slice from the reconstructed fluorescence images for the lowest (5 × 10⁴) and the highest (1 × 10⁶) cell number. The z coordinate is the depth of the reconstructed slice, which corresponds to the maximum of the reconstructed intensity.

FPT of lung cancer at 10 and 20 days of tumor growth and corresponding x-ray CT images. (a–g) Images obtained from the first imaging session 10 days after the injection of the cancer cells. (h–n) Corresponding images obtained at the 20th day of tumor growth. (a and h) A white light image of the mouse. (b and i) An epi-illumination image of the mouse demonstrating high skin autofluorescence. Light from the GFP-expressing tumor is not detected. (c and j) A FPT reconstructed coronal slice (in color) obtained from the tumor depth (≈7 mm from top surface) overlaid on the white light image of the mouse. (d, e, k, and l) CT coronal (d and k) and axial (e and l) slices; the tumor position is marked by arrows. (f and m) FPT axial reconstructed slice corresponding to the yellow dashed rectangle on e and l, respectively. (g and n) A 3D rendering from the CT data demonstrating the position of the tumor in the animal.

Visualization of tumor- and virus-mediated gene delivery. (a and b) Reconstructed coronal slices corresponding to the unmixed signals at the GFP and YFP channels, respectively. (c and d) Spectrally deconvolved reconstructed slices representing the GFP-expressing virus-transduced cells and the YFP-expressing tumor cells, respectively. (e) The corresponding two unmixed images overlaid.