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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
The mechanism of the contrast in US imaging is a mismatch in acoustic impedance. The contrast agents for US are elements that exhibit altered acoustic impedance relative to the surrounding biological backgrounds. Efficient application of US molecular imaging requires: (a) capability to image retained contrast with sensitivity; (b) removal of any unbound contrast from the imaged area; and (c) retention of the contrast agent by the molecular target [8]. US imaging uses contrast agents of two types: (a) microbubble (MB) and (b) non-MB-based contrast agents (Figure 5.1) [9, 10].
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.
Gold Nanomaterials at Work in Biomedicine *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Xuan Yang, Miaoxin Yang, Pang Bo, Madeline Vara, Younan Xia
X-ray CT is one of the most widely used modalities for medical imaging in the hospital. It can be used to obtain complementary anatomical information for diagnostics in a cost-effective fashion. For conventional X-ray CT, however, the contrast between different types of soft tissues is negligible, and a good contrast can only be achieved between hard and soft tissues when no contrast agent is applied [553]. As a result, conventional X-ray CT cannot be used alone to differentiate cancerous from normal tissues, rendering it essentially useless for the early stage detection of cancer or cancer metastasis. Various types of contrast agents, most of which are iodine-based compounds, have been developed to address this technical issue in terms of contrast [553]. Most of them, however, do not have targeting capabilities, resulting in contrast enhancement largely reliant on profusion.
Addition of terlipressin to norepinephrine in septic shock and effect of renal perfusion: a pilot study
Published in Renal Failure, 2022
Jinlong Wang, Mengjuan Shi, Lili Huang, Qing Li, Shanshan Meng, Jingyuan Xu, Ming Xue, Jianfeng Xie, Songqiao Liu, Yingzi Huang
Several parameters of renal contrast-enhanced ultrasound can reflect renal perfusion in patients with septic shock. Peak sonographic signal intensity reflects renal perfusion through the measurement of the maximum echo intensity of the contrast agent. Time to peak deals with the time needed to reach the peak sonographic signal intensity after the contrast agent signal appears in the kidney and is associated with renal microvascular dysfunction in septic shock [19]. Regional blood flow depends on the amount of contrast agent in circulation, the patient’s sebum thickness, and renal perfusion, which often lead to large variations in regional blood flow. Mean transit time is the time needed to enhance the renal cortex after contrast agent injection. In this study, we observed an increase in peak sonographic signal intensity and a decrease in time to peak in the terlipressin group compared to the usual care group. The lack of significant differences in regional blood flow and mean transit time between the two groups may be related to the small sample size and large variations.
Imaging features of hepatobiliary MRI and the risk of hepatocellular carcinoma development
Published in Scandinavian Journal of Gastroenterology, 2022
Jong-In Chang, Dong Hyun Sinn, Woo Kyoung Jeong, Jeong Ah Hwang, Ho Young Won, Kyunga Kim, Wonseok Kang, Geum-Youn Gwak, Yong-Han Paik, Moon Seok Choi, Joon Hyeok Lee, Kwang Cheol Koh, Seung-Woon Paik
All MR images were acquired using 3.0-T whole-body MRI systems (Achieva TX and Ingenia CX; Philips Healthcare, Best, The Netherlands) with a 32-channel phased-array receiver coil. The MRI examination included dual-echo spoiled 3-D gradient-echo T1-weighted in-phase and opposed phase images, single-shot and multi-shot turbo spin-echo T2-weighted images, and diffusion-weighted imaging with single-shot echo-planar images at b-values of 0, 100 or 800 s/mm2. For gadoxetic acid-enhanced imaging (Primovist, Eovist; Bayer Schering Pharma, Berlin, Germany), unenhanced, arterial phase (20–35 s; with an MR fluoroscopic bolus detection technique), portal venous phase (60 s), delayed phase (3 min) and 20-minute HBP images were obtained using a T1-weighted 3D gradient-echo sequence (THRIVE, Philips Healthcare, Best, The Netherlands). The contrast agent was administered intravenously at a rate of 1–2 mL/s for a total dose of 0.025 mmol/kg body weight, followed by a 20-mL saline flush. DWI with b-values of 0, 100 and 800 s/mm2 were acquired simultaneously. An apparent diffusion coefficient (ADC) map was generated from b values of 0 and 800 s/mm2 (Supplementary Table 1).
Genotoxic effects of gadobutrol and gadoversetamide active substances used in magnetic resonance imaging in human peripheral lymphocytes in vitro
Published in Drug and Chemical Toxicology, 2022
Ece Akbas, Fatma Unal, Deniz Yuzbasioglu
Contrast agents in magnetic resonance imaging have been widely applied in recent years to provide better contrast in images and to distinguish healthy tissues from pathological ones, thereby making the diagnosis of diseases more precise (Geraldes and Laurent 2009). Contrast agents are used in almost half of the MRI examinations performed today. Since it allows a higher quality in MR images, the use and the need for contrast agents are increasing day by day. Due to all these reasons, new contrast agents are consistently being explored and discovered (Xiao et al. 2016, Caspani et al. 2020). The most used contrast agents during MRI are gadolinium-based contrast agents (Wahsner et al. 2019). GBCAs have been largely used in radiology in the last 30 years since they have a higher magnetic moment compared to other agents and greatly improve the quality of MR images (Pullicino and Das 2017).