Application of elastic magnetic fluids for nuclear magnetic resonance imaging

New studies on nuclear magnetic resonance spectroscopy (Nuclear Magnetic Resonance-NMR) proton of a magnetorheological nanofluid can help scientists distinguish

Photograph of iron oxide nanoparticles
(Photo: VatlyVietNam)

are healthy cells and pathogens or malignant tumors in the human body.

Natalia Noginova's research group (Norfolk State University, USA) and colleagues have found that iron oxide nanoparticles (g-Fe ₂ O ₃ ) affect the ability to recover spin in liquids. These nanoparticles surround. This effect differs from that of solids and also changes with different liquids. (Details in the recently published Journal of Applied Physics) .

Magnetic nanoparticles are promising candidates for many applications in science as well as technology and medicine, biology . such as drug delivery, localized heat therapy (cancer treatment) , selecting, separating cells, increasing the resolution of magnetic resonance images .

To understand the magnetic properties as well as the kinetics of nanoparticles and their influence on the surrounding environment, Noginova and colleagues studied the suspensions of magnetic nanoparticles in other solids and liquids. together. These nanoparticles are a new form of elastic magnetic nano fluid developed by the team of Emmanuel Gannelis at Cornell University (USA).

Figure 1. Magnetic liquid (photo taken by Noginova group).

Magnetic liquid is a magnetic liquid . Normal liquids are made up of molecules or ions. The particles that make up the magnetic liquid are completely different, besides the molecules and ions, the magnetic liquid also has one component, which is solid particles of several tens to several hundred nm in size. Magnetic fluids consist of three main components: magnetic particles (solids), surface covers (also called surface activators, solids or liquids) and solvents (liquids). Magnetic particles need to be dispersed in liquids to form a so-called suspension so that special properties can be obtained. In Vietnam, there is a group of Dr. Nguyen Hoang Hai studying the application of fluids from medicine, biology and environment.

Noginova and colleagues analyzed the samples by placing them in a strong magnetic field of 7 T of nuclear magnetic resonance equipment (NMR) at Norfolk State University. In nuclear magnetic resonance techniques, the pulse magnetic field is used to orient the spins of the hydrogen nucleus (proton) in the sample. Then, they measured the spin recovery time from the orientation state.

The team observed a significant expansion of the proton NMR spectral lines and an increase in recovery rate in different fluid samples as the concentration of nanoparticles increased . According to the scientists, the presence of magnetic nanoparticles affects the resonant frequency and spin recovery in the surroundings of magnetic nanoparticles. Simply understood, these nanoparticles are like tiny magnets, creating a secondary magnetic field that directly impacts the surrounding environment, changing the magnetic resonance properties.

"These effects are the source of recovery in liquids because liquids have a time-dependent component produced by the movement of host molecules," - Noginova said. observed in solids, where the host molecules cannot move ".

Figure 2. Resonance of the resonant line spectrum in different environments
a. water, b. toluene, c. polymer at different liquid concentrations
(In J. Appl. Phys. 101 (2007) 09C102).

This technique can be used to distinguish between tissues, healthy cells with diseased cells or tissues, destroyed in the human body by changing the recovery time in different tissues. . "The change in spin recovery involving basic nanoparticles is determined by diffusion of host molecules, which can be altered depending on the type of tissue" - Noginova explained.

Extensible spectral line and recovery can be used to significantly increase the contrast in magnetic resonance imaging techniques. For example, the intensity of the signal at the peak depends on the line width and therefore if the line is enlarged, the image may be darkened. The results of this study have just been published in the Journal of Applied Physics 101 (2007) 09C102.

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According to the Journal of Applied Physics & NanotechWeb.org, Vietnam Physics