Contrast Agents: X-ray Contrast Agents and Molecular Imaging – A Contradiction?

Speck, Ulrich

doi:10.1007/978-3-540-72718-7_8

Cited by 18 publications

(13 citation statements)

References 12 publications

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“…However, the high content of contrast media required to elicit significant Housfield unit enhancement precludes the use of X-ray contrast agents for many nanoparticle/molecular imaging approaches [81]. To date, neither LDL nor HDL particles have been used as a tumor targeting vehicles for X-ray contrast media.…”

Section: Computed Tomographymentioning

confidence: 99%

Lipoprotein‐Based Nanoplatforms for Cancer Molecular Imaging

Corbin

Zheng

2011

Nanoplatform‐Based Molecular Imaging

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LIPOPROTEINS: NATURE'S ENDOGENOUS NANOCARRIEREfficient transport of key lipids, such as triacylglycerols (TAGs) and cholesterol, is an essential process in mammalian systems. These molecules respectively serve as a high-energy fuel source and as a structural building block for all cells. Like other essential nutrients and substrates these molecules must be delivered to cells through the blood. The hydrophobicity of these molecules, however, poses a daunting problem for their transport through the aqueous channels of the vascular system. Nature has uniquely addressed this dilemma through the lipoprotein carrier system. Plasma lipoproteins are macromolecular vehicles that transport neutral lipids (fat and cholesterol) through the circulatory system and extracellular fluid compartments of the body. These spherical emulsion-like complexes display a range of physicochemical properties; however, they have a common structural organization ( Fig. 18.1.) consisting of an apolar core of TAG and cholesterol esters surrounded by a monolayer of phospholipids and free cholesterol. Interspersed across the phospholipid monolayer are specific amphipathic proteins (apolipoproteins) whose hydrophilic domains extend toward the aqueous environment. These apolipoproteins act to stabilize and confer structural framework to the lipoproteins, modulate enzyme activity, as well as serve as receptor ligands for the lipoprotein delivery system [1]. Nanoplatform-Based Molecular Imaging Edited by Xiaoyuan ChenPlasma lipoproteins can be designated into various classes based on numerous physical parameters (e.g., electrophoretic mobility, diameter). The most commonly accepted classification is based on the density of the different lipoprotein species (see Table 18.1). According to this classification scheme the major density categories include the following.(1) Chylomicrons (d < 0.95 g/mL) are TAG-rich emulsions particles (80-88% by weight) that are synthesized by the intestine after a fatty meal. Chylomicrons are the largest particles in the lipoprotein family (80 nm to 1 m in diameter) and have the highest lipid-to-protein ratio.(2) Very low density lipoproteins (d = 0.95-1.006 g/mL) are also TAG-rich particles, however, they are synthesized by the liver. They are smaller than chylomicrons (30-80 nm in diameter) and contain relatively less TAG but more cholesterol and protein.(3) Low density lipoproteins (d = 1.020-1.063 g/mL) are particles formed from the intravascular catabolism of VLDLs. The LDL core is predominantly cholesterol ester molecules. Finally, (4) high density lipoproteins (d = 1.063-1.210 g/mL) These carriers are the smallest (6-12 nm in diameter) member of the lipoprotein family. Their core is mainly composed of cholesterol esters and they are composed of a relatively high proportion of protein (35-56% by weight).

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Section: Computed Tomographymentioning

confidence: 99%

Lipoprotein‐Based Nanoplatforms for Cancer Molecular Imaging

Corbin

Zheng

2011

Nanoplatform‐Based Molecular Imaging

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“…However, from the viewpoint of contrast agent based molecular imaging, CT has seen very limited use [3, 4]. Typical x-ray contrast agents are highly concentrated aqueous solutions (typically iodine-based), and thus cannot be employed for molecular imaging due to their high viscosity and limits on osmolality [5]. To further investigate the molecular imaging potentials for x-ray imaging, x-ray luminescence computed tomography (XLCT) has recently been studied and developed by several groups, including ours [2–4, 6–17].…”

Section: Introductionmentioning

confidence: 99%

Sensitivity study of x-ray luminescence computed tomography

Lun

Zhang

2017

Appl. Opt.

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X-ray luminescence computed tomography (XLCT) is a hybrid molecular imaging modality that combines the merits of both x-ray imaging (high resolution) and optical imaging (high sensitivity). In this study, we have evaluated the sensitivity of XLCT with phantom experiments by scanning targets of different phosphor concentrations at different depths. We found that XLCT is capable of imaging targets of very low concentrations (27.6 μM or 0.01 mg/mL) at significant depths, such as 21 mm. Our results demonstrate that there is little variation in the reconstructed target size with a maximum target size error of 4.35% for different imaging depths for XLCT. We have for the first time, compared the sensitivity of XLCT with that of traditional computed tomography (CT) for phosphor targets. We found that XLCT’s use of x-ray induced photons provides much higher measurement sensitivity and contrast compared to CT which provides image contrast solely based on x-ray attenuation.

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“…6, 7 However, their non-specific distribution and rapid pharmacokinetics have limited their vascular and targeting performance. 8 Iodinated blood pool CAs of low molecular weights require rapid CT image acquisitions due to their rapid clearance through the kidneys. 9 Several approaches have been reported which describe the encapsulation of water-soluble iodinated CAs ( e.g ., Iopamidol, Lipiodol, and Iopromide) into polymeric and lipid nanoparticulate systems.…”

Section: Introductionmentioning

confidence: 99%

Bismuth@US-tubes as a potential contrast agent for X-ray imaging applications

et al. 2013

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The encapsulation of bismuth as BiOCl/Bi2O3 within ultra-short (ca. 50 nm) single-walled carbon nanocapsules (US-tubes) has been achieved. The Bi@US-tubes have been characterized by high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Bi@US-tubes have been used for intracellular labeling of pig bone marrow-derived mesenchymal stem cells (MSCs) to show high X-ray contrast in computed tomography (CT) cellular imaging for the first time. The relatively high contrast is achieved with low bismuth loading (2.66% by weight) within the US-tubes and without compromising cell viability. X-ray CT imaging of Bi@US-tubes-labeled MSCs showed a nearly two-fold increase in contrast enhancement when compared to unlabeled MSCs in a 100 kV CT clinical scanner. The CT signal enhancement from the Bi@US-tubes is 500 times greater than polymer-coated Bi2S3 nanoparticles and several-fold that of any clinical iodinated contrast agent (CA) at the same concentration. Our findings suggest that the Bi@US-tubes can be used as a potential new class of X-ray CT agent for stem cell labeling and possibly in vivo tracking.

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Contrast Agents: X-ray Contrast Agents and Molecular Imaging – A Contradiction?

Cited by 18 publications

References 12 publications

Lipoprotein‐Based Nanoplatforms for Cancer Molecular Imaging

Lipoprotein‐Based Nanoplatforms for Cancer Molecular Imaging

Sensitivity study of x-ray luminescence computed tomography

Bismuth@US-tubes as a potential contrast agent for X-ray imaging applications

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