Silver Nanoparticle Contrast Agents for Dual-Energy X-Ray Imaging
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Solution Overview
Problem
Current dual-energy x-ray imaging techniques face challenges in achieving sufficient contrast between tissue types, particularly in breast imaging, due to the limitations of iodinated contrast agents, which have non-specific vascular permeation, rapid renal clearance, and suboptimal attenuation profiles within the mammographic energy range.
Innovation Solution
The development of stabilized silver nanoparticle contrast agents and encapsulated nanoparticles, which are synthesized using methods like the Brust method and stabilized with polyethylene glycol, offering improved attenuation profiles and reduced cytotoxicity, allowing for enhanced contrast in dual-energy x-ray imaging by exploiting the favorable k-edge of silver at 25.5 keV.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If iodinated contrast agents are used in dual-energy x-ray imaging, then imaging contrast can be achieved, but the contrast is insufficient due to non-specific vascular permeation and rapid renal clearance
Solution Approach 1:
The patent changes the fundamental parameter of the contrast agent from iodine-based to silver nanoparticle-based. This parameter change enables the contrast agent to exploit the k-edge at 25.5 keV, which falls within the mammographic energy range, thereby achieving superior contrast while improving reliability through the nanoparticles' stable accumulation in the interstitial space
Solution Approach 2:
The patent employs composite material structure by encapsulating silver nanoparticles with silica shells and coating them with polyethylene glycol. This composite approach combines the high atomic number advantage of silver with the biocompatibility and stability benefits of silica and PEG, resolving the contradiction between achieving high contrast and ensuring agent stability
2Measurement precision
If silver nanoparticles are used to provide superior contrast, then radiographic contrast increases, but cytotoxicity may increase
Solution Approach 1:
The patent introduces silica as an intermediary shell between the silver nanoparticle core and the biological environment. This intermediary layer prevents direct contact between the silver nanoparticles and biological tissues, thereby reducing cytotoxicity while preserving the radiographic contrast enhancement properties of the silver core
Solution Approach 2:
The patent creates a composite nanoparticle structure with silver core, silica shell, and PEG coating. This composite design isolates the potentially toxic silver while maintaining its radiographic properties, and the PEG outer layer further enhances biocompatibility by reducing protein adsorption and immune recognition
3Measurement precision
If iodinated contrast agents are used, then imaging can be performed, but soft-tissue noise is not sufficiently suppressed
Solution Approach 1:
The patent changes the energy spectrum parameters by selecting low-energy (20-30 keV) and high-energy (40-60 keV) beams that bracket the silver k-edge at 25.5 keV. This parameter change enables optimal contrast between the silver nanoparticles and surrounding soft tissue, while the dual-energy measurement allows for noise suppression through subtraction imaging
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Silver nanoparticles provide superior contrast to iodine in dual-energy breast x-ray imaging, with up to twice the radiographic contrast, and when encapsulated with silica and PEG coatings, they reduce toxicity and improve biocompatibility, effectively suppressing soft-tissue noise while maintaining signal from the contrast agent.
Implementation Method 1
The discrete jump in attenuation due to the photoelectric effect of the extra k-shell electrons means that the contrast material exhibits a markedly different attenuation profile to the surrounding tissue
Implementation Method 2
Silver filtration is also used in the clinical setting, which could provide additional benefit with a silver imaging agent
Data Source
AI summary
Contrast agents for x-ray imaging including stabilized metal nanoparticles and encapsulated nanoparticles, as well as methods for imaging tissue with these agents, are disclosed. Also disclosed are methods of dual energy x-ray imaging using metal nanoparticle contrast agents or encapsulated metal nanoparticles.