China
Africa
Explore chapters and articles related to this topic
Magnetic Materials for Biomedicine, Catalysis and Others
Published in Chen Wu, Jiaying Jin, Frontiers in Magnetic Materials, 2023
Magnetic resonance imaging (MRI) is one of the most commonly used imaging diagnostic techniques clinically. It utilizes contrast agent to enhance the contrast between normal and diseased tissues for improved sensitivity and accuracy of diagnosis. According to its effect on the proton relaxation time, the contrast agent can be divided into positive and negative ones, also known as the T1- weighted and T2- weighted contrast agent, the corresponding relaxation of which are denoted as r1 and r2. The T1- and T2- weighted contrast agent shortens the longitudinal and transverse relaxation time of hydrogen proton and enhance the brightness and darkness of magnetic resonance imaging, respectively.
Diagnostic Ultrasound
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Contrast agents in general are for increasing the imaging signal to identify the presence of blood or its absence, for example, to delineate vessel or heart walls. For ultrasound we thus need a substance that is echogenic (prone to produce echoes). Revisiting the first section, we remember that what caused a large reflection of sound energy was the difference in acoustic impedance between the tissue and the contrast agent. In that sense, heavy particles that exhibit a large density difference compared to tissue, could be possible candidates. These might, however, have other drawbacks such as clogging vessels. But gas bubbles, on the other hand, actually differ more in both density and sound speed (in fact the determining factor is the elasticity, or compressibility, which is a more proper term when speaking of fluids). The first contrast agents were neither stable nor small enough to be able to cross the lung capillary bed and therefore could only be used to identify, for example, shunts in the venous and arterial circulations.
Nanosensors and their Potential Role in Internet of Medical Things
Published in Suresh Kaushik, Vijay Soni, Efstathia Skotti, Nanosensors for Futuristic Smart and Intelligent Healthcare Systems, 2022
For medical diagnostic or therapeutic applications, nanoparticles are being produced from polymers or lipids. Novel nanoparticles can be designed to carry therapeutic moieties or contrast agents in various diagnostic imaging technologies, such as computed tomography (CT) or magnetic resonance imaging (MRI) since they have high payload capacity and can increase the time available for imaging. The contrast agents usually used for MRI are gadolinium, manganese oxide, or iron particles, and for CT, the agents are iodine, barium, krypton, or xenon. To increase the imaging time, the basic idea adopted was to increase the size of the contrast agents to nanoparticle range using different nanoparticles, typically in the size of 1-100 nm, which would slow down its clearance from the blood. Diagnostic or therapeutic moieties can included in the lipid nanoparticles in mainly four ways- by conjugating on the surface, by filling into the internal lipophilic space (as micelles), by embedding in the lipophilic membrane (liposomes), or by encapsulating in the core of liposomes (Bawa et al. 2016).
Performance of near-infrared dyes as effective contrast agents for breast cancer detection through simulation of photoacoustic imaging
Published in Journal of Modern Optics, 2020
A. Prabhakara Rao, Saugata Sinha
Biological tissue specimens contain intrinsic chromophores like hemoglobin, lipid, water, melanin etc. which are generally exploited as the source of contrast in PA images. Spatially varying concentration of these chromophores determines the optical absorption property of the tissue specimen at different locations. For finding out specific functional information related to the abundance of a particular chromophore, the tissue specimen is imaged using a wavelength that corresponds to the absorption peak of that particular chromophore. In this way, it is possible to recover different functional information of a tissue specimen using multiple wavelengths. Using multi-wavelength PA imaging, researchers found out oxygen saturation levels, characterized atheromatous plaque, differentiated between malignant and non-malignant prostate and thyroid cancer [24–27]. Although the optical absorption properties of the malignant and non-malignant tissue are different, sometimes, specifically at the early stage of cancer, that difference is not big enough to be reflected in the acquired PA images. The endogenous chromophore variation between malignant and non-malignant tissue is not always sufficient to create the required contrast for efficient visualization of malignant lesions. Also, in the case of deep tissue imaging, the amount of light that reaches deep inside tissue is quite small which in turn generates small amplitude PA signals. To improve the PA contrast between malignant and non-malignant tissue, researchers use external or exogenous chromophores [28]. These exogenous contrast agents are injected intravenously in a targeted imaging scheme for improving the contrast between malignant and non-malignant tissue.
Solvent Extraction, Sequential Separation and Trace Determination of La (III), Ce (III), Nd (III) and Gd (III) with 2, 14-bis[m-nitrophenyl]-Calix[4]Resorcinarene-8, 20-bis[N- phenylbenzo]-dihydroxamic Acid
Published in Solvent Extraction and Ion Exchange, 2023
C. R. Sharma, R. N. Patadia, Y. K. Agrawal
Gadolinium is used in magnetic resonance imaging (MRI) as a contrast agent. Its high magnetic moment allows it to produce strong signals in MRI scans, making it useful for detecting tumors, inflammation, and other abnormalities.[9,10] Gadolinium compounds are also used in some types of optical fibers and in certain types of lasers. Additionally, gadolinium has been proposed for use as a neutron absorber in nuclear reactors.[11] Overall, gadolinium has many unique properties and potential applications in many different fields of science and technology.