Molecular Imaging of Cancer: Applications of Magnetic Resonance Methods

Gimi, Barjor; Pathak, Arvind P.; Ackerstaff, Ellen; Glunde, Kristine; Artemov, Dmitri; Bhujwalla, Zaver M.

doi:10.1109/jproc.2005.844266

Cited by 19 publications

(18 citation statements)

References 123 publications

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“…In the last equation, we introduced the local spectral shift as 1 A preliminary version of this work was presented at MedIm 2006 [28]. During the first review cycle of the present manuscript, a paper that describes a similar approach appeared in press [29].…”

Section: A Theorymentioning

confidence: 99%

“…AGNETIC resonance spectroscopy (MRS) has become an important tool in medical imaging; in particular, in human and animal neuroimaging [1], [2]. The measured magnetic resonance (MR) spectrum provides valuable information about metabolite concentrations; these can be estimated by fitting algorithms such as LCModel [3].…”

mentioning

confidence: 99%

“…The a priori information is fed into our extended BSLIM signal model, which then allows to find the compartments' spectra as the solution of a least-squares problem. 1 By taking advantage of the block-diagonal structure of the formulation, we obtain an algorithm that is as fast as the original SLIM method. An important point is that our model is distinct from the one used in GSLIM.…”

mentioning

confidence: 99%

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BSLIM: Spectral Localization by Imaging With Explicit $B_{0}$ Field Inhomogeneity Compensation

Khalidov

Ville

Jacob

et al. 2007

IEEE Trans. Med. Imaging

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Abstract-Magnetic resonance spectroscopy imaging (MRSI) is an attractive tool for medical imaging. However, its practical use is often limited by the intrinsic low spatial resolution and long acquisition time. Spectral localization by imaging (SLIM) has been proposed as a non-Fourier reconstruction algorithm that incorporates spatial a priori information about spectroscopically uniform compartments. Unfortunately, the influence of the magnetic field inhomogeneity-in particular, the susceptibility effects at tissues' boundaries-undermines the validity of the compartmental model. Therefore, we propose BSLIM as an extension of SLIM with field inhomogeneity compensation. A 0 -field inhomogeneity map, which can be acquired rapidly and at high resolution, is used by the new algorithm as additional a priori information. We show that the proposed method is distinct from the generalized SLIM (GSLIM) framework. Experimental results of a two-compartment phantom demonstrate the feasibility of the method and the importance of inhomogeneity compensation.Index Terms-Chemical shift imaging, constrained reconstruction, magnetic field inhomogeneity, magnetic resonance spectroscopy imaging (MRSI).

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Section: A Theorymentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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BSLIM: Spectral Localization by Imaging With Explicit $B_{0}$ Field Inhomogeneity Compensation

Khalidov

Ville

Jacob

et al. 2007

IEEE Trans. Med. Imaging

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“…This can be achieved by using polymeric backbones or in vivo binding of small sized contrast agents to serum proteins [7]. Multilabelled macromolecular T1-contrast agents for mMRI take advantage of the fact that relaxivity is a linear function of the number of lanthanide ions per contrast agent ( Figure 3) [1]. Various labelling concepts, including Gadoliniumloaded liposomes or polymeres with thousands of * * * * This page number is not for citation purposes Gadolinium atoms, have been developed to overcome this limitation in sensitivity.…”

Section: Positive Contrast Agentsmentioning

confidence: 99%

Molecular Magnetic Resonance Imaging

Hengerer¹

2005

Proceedings of the 2nd International University of Malaya Research Imaging Symposium (UMRIS) 2005: Fundamentals of Molecular Im

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Molecular MRI (mMRI) is a special implementation of Molecular Imaging for the non-invasive visualisation of biological processes at the cellular and molecular level. More specifically, mMRI comprises the contrast agentmediated alteration of tissue relaxation times for the detection and localisation of molecular disease markers (such as cell surface receptors, enzymes or signaling molecules), cells (e.g. lymphocytes, stem cells) or therapeutic drugs (e.g. liposomes, viral particles). MRI yields topographical, anatomical maps; functional MRI (fMRI) provides rendering of physiologic functions and magnetic resonance spectroscopy (MRS) reveals the distribution patterns of some specific metabolites. mMRI provides an additional level of information at the molecular or cellular level, thus extending MRI further beyond the anatomical and physiological level. These advances brought by mMRI are mandatory for MRI to be competitive in the age of molecular medicine. mMRI is already today increasingly used for research purposes, e.g. to facilitate the examination of cell migration, angiogenesis, apoptosis or gene expression in living organisms. In medical diagnostics, mMRI will pave the way toward a significant improvement in early detection of disease, therapy planning or monitoring of outcome and will therefore bring significant improvement in the medical treatment for patients.In general, Molecular Imaging demands high sensitivity equipment, capable of quantitative measurements to detect probes that interact with targets at the pico-or nanomolar level. The challenge to detect such sparse targets can be exemplified with cell surface receptors, a common target for molecular imaging. At high expression levels (bigger than 106 per cell) the receptor concentration is approx. 10 15 per ml, i.e. the concentration is in the micromole range. Many targets, however, are expressed in even considerably lower concentrations. Therefore the most sensitive modalities, namely nuclear imaging (PET and SPECT) have always been at the forefront of Molecular Imaging, and many nuclear probes in clinical use today are already designed to detect molecular mechanisms (such as FDG, detecting high glucose metabolism). In recent years however, Molecular Imaging has commanded attention from beyond the field of nuclear medicine. Further imaging modalities to be considered for molecular imaging primarily include optical imaging, MRI and ultrasound.

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“…[15][16][17] USPIOs consist of a magnetic core that is usually coated by various materials (eg, citrate, dextran, or oleic acid) to improve the solubility and the stability of the nanoparticles in colloidal suspension. 18,19 However, the coating is not always strongly retained by the core, and due to gravitational forces, USPIOs dispersed in an aqueous solution tend to aggregate and precipitate, resulting in a destabilization of the suspension. 20 Moreover, the lack of an efficient coating of the magnetic cores increases their susceptibility to aging effects -which can affect the surfaces via oxidation of magnetite (Fe 3 O 4 ) and maghemite (-Fe 2 O 3 ) -resulting in a particle with completely different physicochemical and magnetic properties than expected.…”

Section: Introductionmentioning

confidence: 99%

Ultrasmall superparamagnetic iron oxide (USPIO)-based liposomes as magnetic resonance imaging probes

Frascione¹,

Almer²,

Opriessnig³

et al. 2012

IJN

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Background: Magnetic liposomes (MLs) are phospholipid vesicles that encapsulate magnetic and/or paramagnetic nanoparticles. They are applied as contrast agents for magnetic resonance imaging (MRI). MLs have an advantage over free magnetic nanocores, in that various functional groups can be attached to the surface of liposomes for ligand-specific targeting. We have synthesized PEG-coated sterically-stabilized magnetic liposomes (sMLs) containing ultrasmall superparamagnetic iron oxides (USPIOs) with the aim of generating stable liposomal carriers equipped with a high payload of USPIOs for enhanced MRI contrast. Methods: Regarding iron oxide nanoparticles, we have applied two different commercially available surface-coated USPIOs; sMLs synthesized and loaded with USPIOs were compared in terms of magnetization and colloidal stability. The average diameter size, morphology, phospholipid membrane fluidity, and the iron content of the sMLs were determined by dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence polarization, and absorption spectroscopy, respectively. A colorimetric assay using potassium thiocyanate (KSCN) was performed to evaluate the encapsulation efficiency (EE%) to express the amount of iron enclosed into a liposome. Subsequently, MRI measurements were carried out in vitro in agarose gel phantoms to evaluate the signal enhancement on T1-and T2-weighted sequences of sMLs. To monitor the biodistribution and the clearance of the particles over time in vivo, sMLs were injected in wild type mice. Results: DLS revealed a mean particle diameter of sMLs in the range between 100 and 200 nm, as confirmed by TEM. An effective iron oxide loading was achieved just for one type of USPIO, with an EE% between 74% and 92%, depending on the initial Fe concentration (being higher for lower amounts of Fe). MRI measurements demonstrated the applicability of these nanostructures as MRI probes. Conclusion: Our results show that the development of sMLs is strictly dependent on the physicochemical characteristics of the nanocores. Once established, sMLs can be further modified to enable noninvasive targeted molecular imaging.

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Molecular Imaging of Cancer: Applications of Magnetic Resonance Methods

Cited by 19 publications

References 123 publications

BSLIM: Spectral Localization by Imaging With Explicit $B_{0}$ Field Inhomogeneity Compensation

BSLIM: Spectral Localization by Imaging With Explicit $B_{0}$ Field Inhomogeneity Compensation

Molecular Magnetic Resonance Imaging

Ultrasmall superparamagnetic iron oxide (USPIO)-based liposomes as magnetic resonance imaging probes

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