A High-Sensitivity Benchtop X-Ray Fluorescence Emission Tomography (XFET) System With a Full-Ring of X-Ray Imaging-Spectrometers and a Compound-Eye Collimation Aperture.

The advent of metal-based drugs and metal nanoparticles as therapeutic agents in anti-tumor treatment has motivated the advancement of X-ray fluorescence computed tomography (XFCT) techniques. An XFCT imaging modality can detect, quantify, and image the biodistribution of metal elements using the X-ray fluorescence signal emitted upon X-ray irradiation. However, the majority of XFCT imaging systems and instrumentation developed so far rely on a single or a small number of detectors. This work introduces the first full-ring benchtop X-ray fluorescence emission tomography (XFET) system equipped with 24 solid-state detectors arranged in a hexagonal geometry and a 96-pinhole compound-eye collimator. We experimentally demonstrate the system's sensitivity and its capability of multi-element detection and quantification by performing imaging studies on an animal-sized phantom. In our preliminary studies, the phantom was irradiated with a pencil beam of X-rays produced using a low-powered polychromatic X-ray source (90kVp and 60W max power). This investigation shows a significant enhancement in the detection limit of gadolinium to as low as 0.1 mg/mL concentration. The results also illustrate the unique capabilities of the XFET system to simultaneously determine the spatial distribution and accurately quantify the concentrations of multiple metal elements.

System Modeling and Evaluation of a Prototype Inverted-Compound Eye Gamma Camera for the Second Generation MR Compatible SPECT.

We have reported the design of the MRC-SPECT-II system based on the inverted-compound-eye (ICE) gamma camera to offer a > 1% detection efficiency while maintaining a sub-500 µm imaging resolution [1]. One of the key challenges of using the ICE camera for SPECT imaging is whether one could develop an accurate point response function (PRF), given its complex aperture design and low fractionation accuracy of 3D printing. In this work, we will discuss (I) a combined experimental and analytical approach for deriving the precise PRF, and (II) an experimental imaging study to demonstrate the feasibility of using the ICE-camera for acquiring high-quality SPECT images with a sub-500 µm resolution. These studies would help to overcome one of the major hurdles for implement ICE-cameras for practical SPECT imaging.