Photon-Counting Computed Tomography for Imaging of Gadolinium Nanoparticle Loaded Bone Cements
Abstract
Purpose
Bioresorbable bone cements designed for percutaneous vertebral augmentation (PVA) have insufficient radiopacity, which limits their clinical use as CT imaging is essential for both precise cement implantation and longitudinal monitoring of implant performance. We aim to evaluate how the incorporation of gadolinium nanoparticles (GdNPs) and the use of photon-counting CT (PCCT) improves the visibility of a hydroxyapatite-based bioresorbable bone cement.
Methods
Gadolinium nanoparticles (GdNPs) were synthesized using a one-pot thermal decomposition method. Hydroxyapatite-based bone cement was loaded with GdNPs (0-10% w/w). Rat vertebrae were harvested, and a defect was drilled into the anterior face of the spine. This defect was filled with GdNP-loaded cement. The vertebrae and GdNP-loaded cement disks were imaged on both a micro-energy integrating-detector-CT (EID-CT, 70 kVp, 200 µA, 135 ms) and micro-PCCT (118 kVp, 40 µA, 160 ms). The contrast to noise ratio (CNR) between the cement and the vertebral bone was measured with both systems. Additionally, the concentration of gadolinium in each GdNP-loaded cement was measured using PCCT material decomposition images.
Results
When compared to the cements with no GdNP loading, the CNR measured between the 8% and 10% GdNP-loaded cement and vertebral bone were significantly greater for all PCCT energy bins (p < 0.05). The use of PCCT led to larger CNRs compared to CNRs measured using EID-CT images. The measured gadolinium concentration was correlated with the mass fraction of GdNP added. The measured concentration increased with increasing mass fraction of GdNP except for the 2% GdNP-loaded cement.
Conclusion
The integration of GdNPs and PCCT increased the CNR when compared cements with no GdNP-loaded and EID-CT, respectively. PCCT material decomposition images allowed for the quantification of gadolinium in the GdNP-loaded cements. These results demonstrate the possibility for improved cement materials and methods for the monitoring of bone cement implants.