T2 Contrast

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Horst Weller - One of the best experts on this subject based on the ideXlab platform.

  • relaxivity optimization of a pegylated iron oxide based negative magnetic resonance Contrast agent for T2 weighted spin echo imaging
    ACS Nano, 2012
    Co-Authors: Elmar Poselt, Hauke Kloust, Ulrich I Tromsdorf, Marcus Janschel, Christoph Hahn, Christoph Maslo, Horst Weller
    Abstract:

    Concerning the outer sphere relaxation theory, the sensitivity of a T2 MRI Contrast agent, expressed by the transverse relaxivity r2, depends on the diffusion length of water molecules relative to the particle size. For T2-weighted spin–echo imaging, theoretical concepts reveal three regimes regarding the r2 relaxivity depending on the nanocrystal size: the motional averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r2 maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T2 Contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30–200 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T2 Contrast agents by tuning the cluster size of SPIO nanocrystals.

  • relaxivity optimization of a pegylated iron oxide based negative magnetic resonance Contrast agent for T2 weighted spin echo imaging
    ACS Nano, 2012
    Co-Authors: Elmar Poselt, Hauke Kloust, Ulrich I Tromsdorf, Marcus Janschel, Christoph Hahn, Christoph Maslo, Horst Weller
    Abstract:

    Concerning the outer sphere relaxation theory, the sensitivity of a T2 MRI Contrast agent, expressed by the transverse relaxivity r2, depends on the diffusion length of water molecules relative to the particle size. For T2-weighted spin–echo imaging, theoretical concepts reveal three regimes regarding the r2 relaxivity depending on the nanocrystal size: the motional averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r2 maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T2 Contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30–200 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T2 Contrast agents by tuning the cluster size of SPIO nanocrystals.

  • Relaxivity Optimization of a PEGylated Iron-Oxide-Based Negative Magnetic Resonance Contrast Agent for T2-Weighted Spin–Echo Imaging
    ACS nano, 2012
    Co-Authors: Elmar Poselt, Hauke Kloust, Ulrich I Tromsdorf, Marcus Janschel, Christoph Hahn, Christoph Maßlo, Horst Weller
    Abstract:

    Concerning the outer sphere relaxation theory, the sensitivity of a T2 MRI Contrast agent, expressed by the transverse relaxivity r2, depends on the diffusion length of water molecules relative to the particle size. For T2-weighted spin–echo imaging, theoretical concepts reveal three regimes regarding the r2 relaxivity depending on the nanocrystal size: the motional averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r2 maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T2 Contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30–200 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T2 Contrast agents by tuning the cluster size of SPIO nanocrystals.

Xiaoyuan Chen - One of the best experts on this subject based on the ideXlab platform.

  • Interplay between longitudinal and transverse Contrasts in Fe3O4 nanoplates with (111) exposed surfaces.
    ACS nano, 2014
    Co-Authors: Zijian Zhou, Xiaoyuan Chen, Zhong Chen, Zhenghuan Zhao, Hui Zhang, Zhenyu Wang, Ruifang Wang, Jinhao Gao
    Abstract:

    Iron oxide has been developed as either T1 or T2 magnetic resonance imaging (MRI) Contrast agents by controlling the size and composition; however, the underlying mechanism of T1 and T2 Contrasts in one iron oxide entity is still not well understood. Herein, we report that freestanding superparamagnetic magnetite nanoplates with (111) exposed facets have significant but interactional T1 and T2 Contrast effects. We demonstrate that the main contribution of the T1 Contrast of magnetic nanoplates is the chemical exchange on the iron-rich Fe3O4(111) surfaces, whereas the T2 relaxation is dominated by the intrinsic superparamagnetism of the nanoplates with an enhanced perturbation effect. We are able to regulate the balance of T1 and T2 Contrasts by controlling structure and surface features, including morphology, exposed facets, and surface coating. This study provides an insightful understanding on the T1 and T2 Contrast mechanisms, which is urgently needed to allow more sophisticated design of high-performa...

  • a synergistically enhanced t1 T2 dual modal Contrast agent
    Advanced Materials, 2012
    Co-Authors: Zijian Zhou, Dengtong Huang, Qiaoli Chen, Xiaoyuan Chen, Zhong Chen
    Abstract:

    Among various molecular imaging techniques, magnetic resonance imaging (MRI) is one of the most powerful and non-invasive diagnostic tools because MRI can provide images with excellent anatomical details based on the interaction of protons with the surrounding molecules of tissues.[1] MRI Contrast agents, generally in the form of T1 positive Contrast agents and T2 negative Contrast agents, can greatly improve the sensitivity of MRI by increasing the Contrast of the target from the background. For example, superparamagnetic iron oxide (SPIO) nanoparticles with strong magnetic moments are the prevailing T2 Contrast agents, especially in the imaging and detection of lesions from normal tissues.[2] The significant drawbacks of SPIO nanoparticles as T2 Contrast agents are, however, magnetic susceptibility artifacts and negative Contrast effects (i.e., dark MR images),[3] which may limit their clinical applications. On the contrary, T1 imaging, typically using paramagnetic materials as Contrast agents, has excellent resolution between tissues due to its high signal intensity (bright and positive MR images).[4] Although ultrasmall (~3 nm in diameter) iron oxide nanoparticles can be used as T1 Contrast agents,[5] the gadolinium species possessing seven unpaired electrons are still the prevailing T1 Contrast agents in clinical use.[4]

Jinhao Gao - One of the best experts on this subject based on the ideXlab platform.

  • Composition Tunable Manganese Ferrite Nanoparticles for Optimized T2 Contrast Ability
    Chemistry of Materials, 2017
    Co-Authors: Lijiao Yang, Zhong Chen, Jingyu Xin, Chengjie Sun, Ruixue Wei, Bin W. Ren, Hongyu Lin, Jinhao Gao
    Abstract:

    Manganese-doped magnetite nanoparticles as magnetic resonance imaging (MRI) Contrast agents have been well developed in recent years due to their higher saturation magnetization and stronger transverse (T2) Contrast ability compared to parent magnetite. However, the underlying role that manganese doping plays in altering the Contrast ability of magnetite is still not thoroughly understood. Herein, we investigate the effects of manganese doping on changes of ferrite crystal structures, magnetic properties, and Contrast abilities. We developed a successful one-pot synthesis of uniform manganese-doped magnetite (MnxFe3–xO4) nanoparticles with different manganese contents (x = 0–1.06). The saturation magnetization and T2 Contrast ability of ferrite nanoparticles increase along with rising manganese proportion, peak when the doping level of MnxFe3–xO4 reaches x = 0.43, and decrease dramatically as the manganese percentage continues to augment. At high manganese doping level, the manganese ferrite nanoparticles...

  • Europium-engineered iron oxide nanocubes with high T1 and T2 Contrast abilities for MRI in living subjects.
    Nanoscale, 2015
    Co-Authors: Lijiao Yang, Zijian Zhou, Guoming Huang, Hanyu Liu, Hui Zhang, Jinhao Gao
    Abstract:

    Magnetic resonance imaging (MRI) Contrast agents with both positive (T1) and negative (T2) Contrast abilities are needed in clinical diagnosis for fault-free accurate detection of lesions. We report a facile synthesis of europium-engineered iron oxide (EuIO) nanocubes as T1 and T2 Contrast agents for MRI in living subjects. The Eu(III) oxide-embedded iron oxide nanoparticles significantly increase the T1 relaxivity with an enhanced positive Contrast effect. EuIO nanocubes with 14 nm in diameter showed a high r1 value of 36.8 mM−1 s−1 with respect to total metal ions (Fe + Eu), which is about 3 times higher than that of Fe3O4 nanoparticles with similar size. Moreover, both r1 and r2 values of EuIO nanocubes can be tuned by varying their sizes and Eu doping ratios. After citrate coating, EuIO nanocubes can provide enhanced T1 and T2 Contrast effects in small animals, particularly in the cardiac and liver regions. This work may provide an insightful strategy to design MRI Contrast agents with both positive and negative Contrast abilities for biomedical applications.

  • Interplay between longitudinal and transverse Contrasts in Fe3O4 nanoplates with (111) exposed surfaces.
    ACS nano, 2014
    Co-Authors: Zijian Zhou, Xiaoyuan Chen, Zhong Chen, Zhenghuan Zhao, Hui Zhang, Zhenyu Wang, Ruifang Wang, Jinhao Gao
    Abstract:

    Iron oxide has been developed as either T1 or T2 magnetic resonance imaging (MRI) Contrast agents by controlling the size and composition; however, the underlying mechanism of T1 and T2 Contrasts in one iron oxide entity is still not well understood. Herein, we report that freestanding superparamagnetic magnetite nanoplates with (111) exposed facets have significant but interactional T1 and T2 Contrast effects. We demonstrate that the main contribution of the T1 Contrast of magnetic nanoplates is the chemical exchange on the iron-rich Fe3O4(111) surfaces, whereas the T2 relaxation is dominated by the intrinsic superparamagnetism of the nanoplates with an enhanced perturbation effect. We are able to regulate the balance of T1 and T2 Contrasts by controlling structure and surface features, including morphology, exposed facets, and surface coating. This study provides an insightful understanding on the T1 and T2 Contrast mechanisms, which is urgently needed to allow more sophisticated design of high-performa...

Zhong Chen - One of the best experts on this subject based on the ideXlab platform.

  • Composition Tunable Manganese Ferrite Nanoparticles for Optimized T2 Contrast Ability
    Chemistry of Materials, 2017
    Co-Authors: Lijiao Yang, Zhong Chen, Jingyu Xin, Chengjie Sun, Ruixue Wei, Bin W. Ren, Hongyu Lin, Jinhao Gao
    Abstract:

    Manganese-doped magnetite nanoparticles as magnetic resonance imaging (MRI) Contrast agents have been well developed in recent years due to their higher saturation magnetization and stronger transverse (T2) Contrast ability compared to parent magnetite. However, the underlying role that manganese doping plays in altering the Contrast ability of magnetite is still not thoroughly understood. Herein, we investigate the effects of manganese doping on changes of ferrite crystal structures, magnetic properties, and Contrast abilities. We developed a successful one-pot synthesis of uniform manganese-doped magnetite (MnxFe3–xO4) nanoparticles with different manganese contents (x = 0–1.06). The saturation magnetization and T2 Contrast ability of ferrite nanoparticles increase along with rising manganese proportion, peak when the doping level of MnxFe3–xO4 reaches x = 0.43, and decrease dramatically as the manganese percentage continues to augment. At high manganese doping level, the manganese ferrite nanoparticles...

  • tunable t1 and T2 Contrast abilities of manganese engineered iron oxide nanoparticles through size control
    Nanoscale, 2014
    Co-Authors: Guoming Huang, Zhong Chen, Lijiao Yang, Hui Li, Jiahe Chen, Zhenghuan Zhao, Xiaomin Wang
    Abstract:

    In this paper, we demonstrate the tunable T1 and T2 Contrast abilities of engineered iron oxide nanoparticles with high performance for liver Contrast-enhanced magnetic resonance imaging (MRI) in mice. To enhance the diagnostic accuracy of MRI, large numbers of Contrast agents with T1 or T2 Contrast ability have been widely explored. The comprehensive investigation of high-performance MRI Contrast agents with controllable T1 and T2 Contrast abilities is of high importance in the field of molecular imaging. In this study, we synthesized uniform manganese-doped iron oxide (MnIO) nanoparticles with controllable size from 5 to 12 nm and comprehensively investigated their MRI Contrast abilities. We revealed that the MRI Contrast effects of MnIO nanoparticles are highly size-dependent. By controlling the size of MnIO nanoparticles, we can achieve T1-dominated, T2-dominated, and T1–T2 dual-mode MRI Contrast agents with much higher Contrast enhancement than the corresponding conventional iron oxide nanoparticles.

  • Interplay between longitudinal and transverse Contrasts in Fe3O4 nanoplates with (111) exposed surfaces.
    ACS nano, 2014
    Co-Authors: Zijian Zhou, Xiaoyuan Chen, Zhong Chen, Zhenghuan Zhao, Hui Zhang, Zhenyu Wang, Ruifang Wang, Jinhao Gao
    Abstract:

    Iron oxide has been developed as either T1 or T2 magnetic resonance imaging (MRI) Contrast agents by controlling the size and composition; however, the underlying mechanism of T1 and T2 Contrasts in one iron oxide entity is still not well understood. Herein, we report that freestanding superparamagnetic magnetite nanoplates with (111) exposed facets have significant but interactional T1 and T2 Contrast effects. We demonstrate that the main contribution of the T1 Contrast of magnetic nanoplates is the chemical exchange on the iron-rich Fe3O4(111) surfaces, whereas the T2 relaxation is dominated by the intrinsic superparamagnetism of the nanoplates with an enhanced perturbation effect. We are able to regulate the balance of T1 and T2 Contrasts by controlling structure and surface features, including morphology, exposed facets, and surface coating. This study provides an insightful understanding on the T1 and T2 Contrast mechanisms, which is urgently needed to allow more sophisticated design of high-performa...

  • a synergistically enhanced t1 T2 dual modal Contrast agent
    Advanced Materials, 2012
    Co-Authors: Zijian Zhou, Dengtong Huang, Qiaoli Chen, Xiaoyuan Chen, Zhong Chen
    Abstract:

    Among various molecular imaging techniques, magnetic resonance imaging (MRI) is one of the most powerful and non-invasive diagnostic tools because MRI can provide images with excellent anatomical details based on the interaction of protons with the surrounding molecules of tissues.[1] MRI Contrast agents, generally in the form of T1 positive Contrast agents and T2 negative Contrast agents, can greatly improve the sensitivity of MRI by increasing the Contrast of the target from the background. For example, superparamagnetic iron oxide (SPIO) nanoparticles with strong magnetic moments are the prevailing T2 Contrast agents, especially in the imaging and detection of lesions from normal tissues.[2] The significant drawbacks of SPIO nanoparticles as T2 Contrast agents are, however, magnetic susceptibility artifacts and negative Contrast effects (i.e., dark MR images),[3] which may limit their clinical applications. On the contrary, T1 imaging, typically using paramagnetic materials as Contrast agents, has excellent resolution between tissues due to its high signal intensity (bright and positive MR images).[4] Although ultrasmall (~3 nm in diameter) iron oxide nanoparticles can be used as T1 Contrast agents,[5] the gadolinium species possessing seven unpaired electrons are still the prevailing T1 Contrast agents in clinical use.[4]

Renjun Pei - One of the best experts on this subject based on the ideXlab platform.

  • redox triggered aggregation of esionps with switchable t1 to T2 Contrast effect for T2 weighted magnetic resonance imaging
    Journal of Materials Chemistry B, 2021
    Co-Authors: Yi Cao, Zheng Mao, Youxin Zhou, Ye Zhang, Renjun Pei
    Abstract:

    Magnetic resonance imaging (MRI) Contrast agents (CAs) have drawn increasing attention in cancer diagnosis. However, since the signals they generate are always “on” and may bring interfering background signals to the region of interest, their selectivity and sensitivity need further improvement. Herein, extremely small iron oxide nanoparticles (ESIONPs) conjugated through a disulfide bond with polyethylene glycol (PEG) that is terminally modified with folic acid (FA), namely ESIONPs-s-s-PEG-FA, were designed and synthesized to target tumor tissues and selectively activate the T2 MRI Contrast effect in the reducing environment of tumor cells. Due to the breakage of disulfide bonds by the high glutathione (GSH) concentration in tumor cells, the hydrophilic PEG chains detached from the surface of ESIONPs, which led to the aggregation of ESIONPs and the activation of the T2 Contrast effect. In vitro results showed that ESIONPs-s-s-PEG-FA could effectively target tumors to assemble in the reductive environment and switch from a T1 Contrast agent (CA) to a T2 one. Furthermore, MRI in tumor-bearing mice also indicated the obvious targeting capacity and the “turn on” of the T2 Contrast effect. In addition, the results of the biosafety assay suggest that the tumor-targeted T1/T2 switchable CA is equipped with favorable biocompatibility for cancer diagnosis.

  • Redox-triggered aggregation of ESIONPs with switchable T1 to T2 Contrast effect for T2-weighted magnetic resonance imaging.
    Journal of materials chemistry. B, 2021
    Co-Authors: Yi Cao, Zheng Mao, Youxin Zhou, Ye Zhang, Renjun Pei
    Abstract:

    Magnetic resonance imaging (MRI) Contrast agents (CAs) have drawn increasingly attention in the cancer diagnosis. However, since the signal they generate is always “on” and may bring disturbed background signal to the region of interest, their selectivity and sensitivity need further improvement. Herein, extremely small iron oxide nanoparticles (ESIONPs) conjugated through a disulfide bond with polyethylene glycol (PEG) that is terminally modified with folic acid (FA), namely ESIONPs-s-s-PEG-FA, was designed and synthesized to target tumor tissues and selectively activate the T2 MRI Contrasting effect in the reducing environment of tumor cells. On the basis of the breakage of disulfide bond by the high glutathione (GSH) concentration in tumor cells, the hydrophilic PEG chains detached from the surface of ESIONPs, which led to the aggregation of ESIONPs and the activation of T2 Contrasting effect. In vitro results showed that ESIONPs-s-s-PEG-FA could effectively target tumor to assemble in the reductive environment and switch from a T1 Contrast agent (CA) to a T2 one. Furthermore, MRI in tumor-bearing mice also indicated the obvious targeting capacity and the “turn on” of T2 Contrast effecting. In addition, the results of biosafety assay suggest that the tumor-targeted T1/T2 switchable CA is equipped with favorable biocompatibility for cancer diagnosis.