Micro-CT imaging of multiple K-edge elements using GaAs and CdTe photon counting detectors

Abstract

Objective: To evaluate the performance of two photon-counting (PC) detectors based on different detector materials, gallium arsenide (GaAs) and cadmium telluride (CdTe), for PC micro-CT imaging of phantoms with multiple contrast materials. Another objective is to determine if combining these two detectors in the same micro-CT system can offer higher spectral performance and significant artifact reduction compared to a single detector system. 
Approach: We have constructed a dual-detector, micro-CT system equipped with two PCDs based on different detector materials: gallium arsenide (GaAs) and cadmium telluride (CdTe). We demonstrate the performance of these detectors for photon-counting (PC) micro-CT imaging of phantoms with up to 5 contrast materials with K-edges spread across the X-ray spectrum ranging from iodine with a K-edge at 33.2 keV to bismuth with a K-edge at 90.5 keV. We also demonstrate the use of our system to image a mouse prepared with both iodine and bismuth contrast agents to target different biological systems.
Main Results: When using the same dose and scan parameters, GaAs shows increased low energy (<50 keV) spectral sensitivity and specificity compared to CdTe. However, GaAs performance at high energies suffers from spectral artifacts and has comparatively low photon counts indicating wasted radiation dose. We demonstrate that combining a GaAs-based and a CdTe-based PC detector in the same micro-CT system offers higher spectral performance and significant artifact reduction compared to a single detector system. 
Significance: More accurate PC micro-CT using a GaAs PCD alone or in combination with a CdTe PCD could serve for developing new contrast agents such as nanoparticles that show promise in the developing field of theranostics (therapy and diagnostics).

A Deep Learning Approach for Rapid and Generalizable Denoising of Photon-Counting Micro-CT Images

“…PCDs acquire images at two or more energies simultaneously by detecting individual x-ray photons and sorting them into bins based on energy thresholds, making photon-counting CT (PCCT) a promising tool for spectral imaging tasks that require material decomposition. Moreover, PCD energy thresholds can be adjusted near the K-edges of various contrast agents, enabling their spectral separation in novel imaging procedures [ 2 , 3 ].…”