Theranostic Aguix Nanoparticles As an MRI Contrast Agent for Tumor Delineation
Abstract
Purpose
AGuIX nanoparticles, composed of a polysiloxane core with gadolinium chelates, are a theranostic agent, providing both MRI contrast and radiosensitization. The ongoing NanoBrainMets clinical trial looks to evaluate the therapeutic efficacy of AGuIX by quantifying uptake within tumors delineated using standard gadolinium-based contrast agents (GBCAs). This study is the first to use AGuIX for GTV delineation and compare against GBCAs to examine its clinical utility as a contrast agent.
Methods
The concentration of AGuIX within 125 lesions was determined using MP2RAGE MRI scans and a previously defined longitudinal relaxivity constant . Contours were generated on MPRAGE scans utilizing standard GBCA for contrast and Contours comparisons included Dice-Sørensen coefficients, Hausdorff distance, volume ratios, and contrast to noise ratios (CNR). Auto-contours were also compared to physician-drawn contours as a performance baseline.
Results
For contours generated on AGuIX and GBCA MPRAGE scans, 82% had DSC scores of 0.8 or higher. When compared to physician contours, only 46.9% of GBCA auto-contours had DSC scores of 0.8 or higher. The mean Hausdorff distance was 1.9240 mm (~2 voxels). Mean volume ratios of 1.0962 were found and the mean CNR for AGuIX was 33.9% higher than for GBCA. Uptake distribution differences presented within the center of GTVs based on contrast agent, with some lesions having more homogenous AGuIX uptake.
Conclusion
Reliable contour performance for each contrast agent indicates AGuIX can be utilized as a clinical contrast agent without affecting clinical workflow. Longer retention, radiosensitivity, and higher CNR indicate that AGuIX may be a preferential choice for MR-guided RT. This study suggests that AGuIX can eliminate the need for additional Gadolinium-based contrast administration in addition to providing theranostic capabilities.