Tomographic molecular imaging of x-ray-excitable nanoparticles

Abstract

X-ray luminescence computed tomography (XLCT) is proposed as a new dual molecular/anatomical imaging modality. XLCT is based on the selective excitation and optical detection of x-ray-excitable nanoparticles. As a proof of concept, we built a prototype XLCT system and imaged near-IR-emitting Gd(2)O(2)S:Eu phosphors in various phantoms. Imaging in an optically diffusive medium shows that imaging performance is not affected by optical scatter; furthermore, the linear response of the reconstructed images suggests that XLCT is capable of quantitative imaging.

Fig. 1.

(Color online) A phantom containing phosphor inclusions is moved on a rotation/translation stage while being irradiated by a narrow, stationary x-ray beam. At each position, the XL signal was measured with an EM-CCD camera. Inset, XL spectrum for GOSE.

Fig. 2.

(Color online) Sample images acquired with an EMCCD camera (white arrow) of the turbid phantom under three different x-ray irradiations (bottom-right inset). Each image maps to a sinogram bin (red cross, bottom-left inset). The hot spot in the middle image was caused by a defect in the phantom.

Fig. 3.

(Color online) A turbid phantom (left), composed of phosphor suspended in an optically diffusive cylinder, was acquired using XLCT to produce a sinogram (middle), which was reconstructed with 100 iterations of ML-EM (right). The simulation (bottom row) modeled the light propagation in a diffuse medium.

Fig. 4.

(Color online) A gradient phantom (left), composed of various phosphor concentrations embedded in a gel, was acquired using XLCT to produce a sinogram (middle), which was reconstructed with 100 iterations of ML-EM (right).

Fig. 5.

Response linearity for all seven phosphor inclusions, shown for the experimental and simulated gradient phantom.