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Acoustically Reflective Nanoparticles for Tumor Diagnosis
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
R. G. Aswathy, D. Sakthi Kumar
Non-MB or nanobubbles are liquid–liquid emulsions, liposomes or solid NPs in size the range of 10–1000 nm [49–51]. These contrast agents can serve as an efficient tool for US imaging only if they show good biocompatibility, easy route of administration, and should provide contrast to the surrounding tissue with good contrast-to-tissue ratio (CTR). Non-MB-based contrast agents infiltrate extravascular space offering the prospect of acquisition of images apart from vascular compartment. Tiny free gas bubbles used in US imaging dissolve quickly in the media and hence the contrast arises near to the site of infusion. Owing to the insignificant intrinsic acoustic reflectivity, non-MB-based imaging agents are not spotted independently by US imaging. Therefore, alternative strategies for visualization of these contrast agents with US have been recommended. In present scenario, targeted contrast agents are in use and specifically target the molecular markers and are efficiently internalized to site of interest leading to molecular US imaging. Many passive and active targeting mechanisms are plotted and are utilized for this purpose successfully.
Fibroids and Reproduction: A Bird's-Eye View
Published in Botros R.M.B. Rizk, Yakoub Khalaf, Mostafa A. Borahay, Fibroids and Reproduction, 2020
Botros R.M.B. Rizk, Candice P. Holliday, Yakoub Khalaf
The specific appearance of a fibroid's outline can be well demonstrated on TVS, even of very small fibroids, because of the fibroid's pseudocapsule. The fibroid has a mixed tissue composition such that a heterogenous echo pattern develops on ultrasound. This echo can be highly attenuating for some fibroids. A fibroid should have a definite outline because heterogenous myometrium without a defined margin could be adenomyosis instead. Fibroids are typically hypoechoic when compared to neighboring myometrium, but then sometimes they can be isoechoic (or even hyperechoic if fatty or fibrous changes have occurred). Cystic degeneration of fibroids can be visualized on ultrasound as a central anechoic area that can contain internal echoes or fluid/fluid levels [3] (Figure 1.9). When fibroid tissue has been replaced with fibrous tissue, there is a total increase in reflectivity on ultrasound. Calcification of fibroids can also occur and is seen as echogenic foci or a bright outer rim that causes posterior acoustic shadowing on ultrasound.
Medical Imaging Informatics
Published in Arvind Kumar Bansal, Javed Iqbal Khan, S. Kaisar Alam, Introduction to Computational Health Informatics, 2019
Arvind Kumar Bansal, Javed Iqbal Khan, S. Kaisar Alam
Optical coherence tomography (OCT) is an optical imaging modality, based on low-coherence interferometry. Like ultrasound imaging, OCT is based on signal reflections. The light is split by using two arms. The sample arm contains the item of interest and a reference arm, typically a mirror, providing the reference signal for the interference. The reflected light from the sample and the reference light combines to produce an interference pattern, if both lights traveled the “same” distance (difference between two distances is less than the coherence length). Light outside the short coherence length does not produce an interference pattern. The mirror in the reference arm is scanned to produce a reflectivity profile of the sample. OCT can capture fine-resolution (μm) images from biological tissues, employing near-infrared light. Near-infrared wavelengths allow deeper penetration into the optical scattering media. However, it is limited to imaging the top one to two mm of biological tissues; at larger depths, not enough light is reflected from the sample to be detected.
Non-invasive imaging techniques to assess myocardial perfusion
Published in Expert Review of Medical Devices, 2020
Olivier Villemain, Jérôme Baranger, Zakaria Jalal, Christopher Lam, Jérémie Calais, Mathieu Pernot, Barbara Cifra, Mark K. Friedberg, Luc Mertens
As blood is a poor reflector of ultrasound energy (i.e. relative homogeneity of the acoustic impedance) it shows dark in the image. For some applications, like myocardial perfusion assessment, it can be useful to artificially increase blood reflectivity. This can be achieved by using an ultrasound contrast agent. As air is a very strong reflector of ultrasound energy due to its relative high compressibility and low density when compared to soft tissue, it is often used as a contrast agent. The injection of small air bubbles with a diameter similar to that of red blood cells, significantly increases blood reflectivity. This can be achieved by the injection of agitated saline or by the use of ultrasound contrast agents that contain encapsulated air bubbles to limit diffusion of air in the blood. Contrast imaging can be helpful for visualizing the endocardial border as contrast enhances the gray-scale difference between the myocardium and the blood pool in patients with poor image penetration (Figure 2). Ultrasound contrast agents can also be used to increase the brightness of perfused myocardial tissue although the presence of artifacts can make the interpretation of the perfusion images more difficult. At present, different contrast agents are commercially available for clinical use but regulatory approvals for pediatric use differ between countries. In the presence of right-to-left shunts, contrast agents should be used cautiously and only by experienced operators.
Multimodal imaging characteristics of congenital grouped hyper‐ and hypo‐pigmented fundus lesions
Published in Clinical and Experimental Optometry, 2020
Henrietta Wang, Angelica Ly, Michael Yapp, Nagi Assaad, Michael Kalloniatis
An 11‐year‐old Caucasian female was referred to CFEH for assessment of small, pigmented lesions in her right eye. Her BCVA was 6/6 in both eyes with a refractive correction of right +0.25/−0.25 × 180 and left +0.50/−0.25 × 5. Her fundus showed six, small distinct, scattered spots of pigmentation in the mid‐periphery of the right eye (Figure 4). Optomap monochromatic imaging showed hypo‐reflectivity of the lesions, more prominent on red than green separation (Figure 4). FAF revealed hypo‐autofluorescent spots at the location of the lesions (Figure 4). OCT revealed thickening of the RPE and associated posterior shadowing of the lesions. The two larger lesions showed an overlying conformational elevation in the EZ (Figure 4). IR imaging over the lesions was variable with some lesions showing hyper‐reflectivity and others showing hypo‐reflectivity (Figure 4). These findings support the diagnosis of atypically sparse CGP‐RPE. Similar to cases 1 and 2, given the non‐progressive nature of CGP‐RPE, the patient was advised to continue routine optometric review with her community optometrist.
Plasma concentration of MMP-1 and MMP-2 in boys with cryptorchidism and its lack of correlation with INSL3 and inhibin B
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2019
Ewa Matuszczak, Marta Diana Komarowska, Anna Sankiewicz, Łukasz Ołdak, Ewa Gorodkiewicz, Wojciech Debek, Robert Milewski, Marzena Tylicka, Adam Hermanowicz
The enzyme-linked immunosorbent assay (ELISA) is the most common method to determine matrix metalloproteinase concentrations [15]. Another choice can be Surface PLASMON RESONANCE Imaging (SPRI), which measures light reflectivity depending on the quantity of molecules on the surface. According to Gorodkiewicz et. al. ‘Surface Plasmon Resonance (SPR) is an optical detection process that occurs when a polarized light hits a prism covered by a thin (gold) metal layer. Under certain conditions (wavelength, polarization and incidence angle) free electrons at the surface of the biochip absorb incident light photons and convert them into surface plasmon waves’ [16]. ‘A dip in reflectivity of the light is seen under these SPR conditions. Perturbations at the gold surface of the biochip, such as an interaction between probe molecules immobilized on the chip and captured target molecules, induce a modification of resonance conditions which are in turn seen as a change in reflectivity and which can be measured’. In SPRI antibody-antigen or inhibitor-enzyme reactions are used [16]. The MMP-2 biosensor in comparison to ELISA is quicker and more duplicatable, and enables quantitative determination with the results similar to the ELISA test [17]. Several SPRI biosensors were used so far for determination of e.g. proteasomes, immunoproteasomes and many other [18–21].