X-ray Luminescence Computed Tomography Research Articles

Spectrally resolving and scattering-compensated x-ray luminescence∕fluorescence computed tomography

The nanophosphors, or other similar materials, emit near-infrared (NIR) light upon x-ray excitation. They were designed as optical probes for in vivo visualization and analysis of molecular and cellular targets, pathways, and responses. Based on the previous work on x-ray fluorescence computed tomography (XFCT) and x-ray luminescence computed tomography (XLCT), here we propose a spectrally-resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography (SXLCT or SXFCT) approach to quantify a spatial distribution of nanophosphors (other similar materials or chemical elements) within a biological object. In this paper, the x-ray scattering is taken into account in the reconstruction algorithm. The NIR scattering is described in the diffusion approximation model. Then, x-ray excitations are applied with different spectra, and NIR signals are measured in a spectrally resolving fashion. Finally, a linear relationship is established between the nanophosphor distribution and measured NIR data using the finite element method and inverted using the compressive sensing technique. The numerical simulation results demonstrate the feasibility and merits of the proposed approach.

Tomographic molecular imaging of x-ray-excitable nanoparticles

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.

X-Ray Luminescence Computed Tomography via Selective Excitation: A Feasibility Study

X-ray luminescence computed tomography (XLCT) is proposed as a new molecular imaging modality based on the selective excitation and optical detection of X-ray-excitable phosphor nanoparticles. These nano-sized particles can be fabricated to emit near-infrared (NIR) light when excited with X-rays, and, because because both X-rays and NIR photons propagate long distances in tissue, they are particularly well suited for in vivo biomedical imaging. In XLCT, tomographic images are generated by irradiating the subject using a sequence of programmed X-ray beams, while sensitive photo-detectors measure the light diffusing out of the subject. By restricting the X-ray excitation to a single, narrow beam of radiation, the origin of the optical photons can be inferred regardless of where these photons were detected, and how many times they scattered in tissue. This study presents computer simulations exploring the feasibility of imaging small objects with XLCT, such as research animals. The accumulation of 50 nm phosphor nanoparticles in a 2-mm-diameter target can be detected and quantified with subpicomolar sensitivity using less than 1 cGy of radiation dose. Provided sufficient signal-to-noise ratio, the spatial resolution of the system can be made as high as needed by narrowing the beam aperture. In particular, 1 mm spatial resolution was achieved for a 1-mm-wide X-ray beam. By including an X-ray detector in the system, anatomical imaging is performed simultaneously with molecular imaging via standard X-ray computed tomography (CT). The molecular and anatomical images are spatially and temporally co-registered, and, if a single-pixel X-ray detector is used, they have matching spatial resolution.

MO‐E‐204C‐05: X‐Ray Luminescence Computed Tomography Via Selective X‐Ray Excitation

Purpose: X‐ray luminescence computed tomography (XLCT) is proposed as a new molecular imaging modality for imaging X‐ray‐excitable phosphorescent nanoparticles three‐dimensionally, in living subjects. Some of these nano‐sized particles can emit near‐infrared (NIR) light when excited with X rays and are particularly well suited for in‐vivo biomedical imaging because the signals can propagate long distances in tissue. Method and Materials: The imaging mechanism used in XLCT consists in irradiating the subject using a sequence of programmed X‐ray beams, while sensitive photo‐detectors measure the light coming out of the subject. By restricting the X‐ray excitation to a single, narrow beam of radiation, the origin of the light photons can be inferred regardless of where these photons were detected, and how many times they scattered in tissue. By including an X‐ray detector in the system, anatomical imaging is performed simultaneously with molecular imaging via standard X‐ray computed tomography. The molecular and anatomical images are spatially and temporally co‐registered. Simulations of an XLCT system were performed using an analytical beam model. A preliminary experiment was also conducted using a superficial treatment beam and an EM‐CCD camera. Results: Tracer uptake in a 2 mm‐diameter target can be detected and quantified with sub‐picomolar sensitivity using less than 1 cGy of radiation dose, a result that makes XLCT potentially more sensitive than PET, currently one of the most sensitive molecular imaging modalities. Provided sufficient signal‐to‐noise ratio, the spatial resolution of the system can be made as small as needed by narrowing the beam aperture. In particular, 1 mm uniform spatial resolution was achieved for a 1 mm‐wide X‐ray beam. Images reconstructed from experimental XLCT measurements showed good agreement with the simulation model. Conclusion: Preliminary simulations and experiments show that XLCT is a feasible approach for small objects, such as research animals or dedicated organ imaging.