Publications by authors named "Helmar Waiczies"

Postoperative care of orthopedic implants is aided by imaging to assess the healing process and the implant status. MRI of implantation sites might be compromised by radiofrequency (RF) heating and RF transmission field (B1+) inhomogeneities induced by electrically conducting implants. This study examines the applicability of safe and B1+-distortion-free MRI of implantation sites using optimized parallel RF field transmission (pTx) based on a multi-objective genetic algorithm (GA).

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Article Synopsis
  • Theranostic imaging methods, particularly Fluorine-19 magnetic resonance imaging (F MRI), can help visualize and quantify CNS-acting drugs like siponimod in a non-invasive way, avoiding harmful radiation.
  • The study characterized the F MR properties of siponimod and confirmed that Ultrashort Echo Time (UTE) imaging is the most sensitive method for detecting its distribution in biological tissues, such as the liver and brain.
  • Results showed that siponimod concentrated mainly in the cerebrum of the brain and displayed varied distribution patterns in different organs, indicating the usefulness of F MRI in understanding drugs' behavior in patients.
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Purpose: Low SNR in fluorine-19 ( F) MRI benefits from cryogenically-cooled transceive surface RF probes (CRPs), but strong B inhomogeneities hinder quantification. Rapid acquisition with refocused echoes (RARE) is an SNR-efficient method for MRI of neuroinflammation with perfluorinated compounds but lacks an analytical signal intensity equation to retrospectively correct B inhomogeneity. Here, a workflow was proposed and validated to correct and quantify F-MR signals from the inflamed mouse brain using a F-CRP.

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Purpose: Design, implementation, evaluation, and application of a 32-channel Self-Grounded Bow-Tie (SGBT) transceiver array for cardiac MR (CMR) at 7.0T.

Methods: The array consists of 32 compact SGBT building blocks.

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The overall goal of this article is to demonstrate a state-of-the-art ultrahigh field (UHF) magnetic resonance (MR) protocol of the brain at 7.0 Tesla in multiple sclerosis (MS) patients. MS is a chronic inflammatory, demyelinating, neurodegenerative disease that is characterized by white and gray matter lesions.

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Kidney-associated pathologies would greatly benefit from noninvasive and robust methods that can objectively quantify changes in renal function. In the past years there has been a growing incentive to develop new applications for fluorine (F) MRI in biomedical research to study functional changes during disease states. F MRI represents an instrumental tool for the quantification of exogenous F substances in vivo.

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Magnetic resonance imaging (MRI) is indispensable for diagnosing neurological conditions such as multiple sclerosis (MS). MRI also supports decisions regarding the choice of disease-modifying drugs (DMDs). Determining tissue concentrations of DMDs has the potential to become an essential clinical tool for therapeutic drug monitoring (TDM).

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The brain ventricles are part of the fluid compartments bridging the CNS with the periphery. Using MRI, we previously observed a pronounced increase in ventricle volume (VV) in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS). Here, we examined VV changes in EAE and MS patients in longitudinal studies with frequent serial MRI scans.

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Thermal intervention is a potent sensitizer of cells to chemo- and radiotherapy in cancer treatment. Glioblastoma multiforme (GBM) is a potential clinical target, given the cancer's aggressive nature and resistance to current treatment options. The annular phased array (APA) technique employing electromagnetic waves in the radiofrequency (RF) range allows for localized temperature increase in deep seated target volumes (TVs).

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Targeted radiofrequency (RF) heating induced hyperthermia has a wide range of applications, ranging from adjunct anti-cancer treatment to localized release of drugs. Focal RF heating is usually approached using time-consuming nonconvex optimization procedures or approximations, which significantly hampers its application. To address this limitation, this work presents an algorithm that recasts the problem as a semidefinite program and quickly solves it to global optimality, even for very large (human voxel) models.

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The objective of this study was the design, implementation, evaluation and application of a compact wideband self-grounded bow-tie (SGBT) radiofrequency (RF) antenna building block that supports anatomical proton ( H) MRI, fluorine ( F) MRI, MR thermometry and broadband thermal intervention integrated in a whole-body 7.0 T system. Design considerations and optimizations were conducted with numerical electromagnetic field (EMF) simulations to facilitate a broadband thermal intervention frequency of the RF antenna building block.

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Objective: Design, implementation, evaluation and application of a quadrature birdcage radiofrequency (RF) resonator tailored for renal and cardiac sodium (Na) magnetic resonance imaging (MRI) in rats at 9.4 T.

Materials And Methods: A low pass birdcage resonator (16 rungs, d = 62 mm) was developed.

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Purpose: Cardiorenal syndrome describes disorders of the heart and the kidneys in which a dysfunction of 1 organ induces a dysfunction in the other. This work describes the design, evaluation, and application of a 4/4-channel hydrogen-1/sodium ( H/ Na) RF array tailored for cardiorenal MRI at 7.0 Tesla (T) for a better physiometabolic understanding of cardiorenal syndrome.

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Objective: Fluorine MR would benefit greatly from enhancements in signal-to-noise ratio (SNR). This study examines the sensitivity gain of F MR that can be practically achieved when moving from 9.4 to 21.

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Purpose: To study the role of temperature in biological systems, diagnostic contrasts and thermal therapies, RF pulses for MR spin excitation can be deliberately used to apply a thermal stimulus. This application requires dedicated transmit/receive (Tx/Rx) switches that support high peak powers for MRI and high average powers for RF heating. To meet this goal, we propose a high-performance Tx/Rx switch based on positive-intrinsic-negative diodes and quarter-wavelength (λ/4) stubs.

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Purpose: The aim of this study was to achieve millimeter spatial resolution sodium in vivo MRI of the human eye at 7 T using a dedicated six-channel transceiver array. We present a detailed description of the radiofrequency coil design, along with electromagnetic field and specific absorption ratio simulations, data validation, and in vivo application.

Methods: Electromagnetic field and specific absorption ratio simulations were performed.

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Diffusion-weighted imaging (DWI) provides information on tissue microstructure. Single-shot echo planar imaging (EPI) is the most common technique for DWI applications in the brain, but is prone to geometric distortions and signal voids. Rapid acquisition with relaxation enhancement [RARE, also known as fast spin echo (FSE)] imaging presents a valuable alternative to DWI with high anatomical accuracy.

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Magnetic resonance imaging (MRI) is the mainstay of diagnostic imaging, a versatile instrument for clinical science and the subject of intense research interest. Advancing clinical science, research and technology of MRI requires high fidelity measurements in quantity, location and time of the given physical property. To meet this goal a broad spectrum of commercial measurement systems has been made available.

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Neuroinflammation can be monitored using fluorine-19 (F)-containing nanoparticles and F MRI. Previously we studied neuroinflammation in experimental autoimmune encephalomyelitis (EAE) using room temperature (RT) F radiofrequency (RF) coils and low spatial resolution F MRI to overcome constraints in signal-to-noise ratio (SNR). This yielded an approximate localization of inflammatory lesions.

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There is increasing clinical use of combined positron emission tomography and MRI, but to date there has been no clinical system developed capable of simultaneous single-photon emission computed tomography (SPECT) and MRI. There has been development of preclinical systems, but there are several challenges faced by researchers who are developing a clinical prototype including the need for the system to be compact and stationary with MRI-compatible components. The limited work in this area is described with specific reference to the Integrated SPECT/MRI for Enhanced stratification in Radio-chemo Therapy (INSERT) project, which is at an advanced stage of developing a clinical prototype.

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Glioma regression requires the recruitment of potent antitumor immune cells into the tumor microenvironment. Dendritic cells (DC) play a role in immune responses to these tumors. The fact that DC vaccines do not effectively combat high-grade gliomas, however, suggests that DCs need to be genetically modified specifically to promote their migration to tumor relevant sites.

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Research in pathologies of the brain, heart and kidney have gained immensely from the plethora of studies that have helped shape new methods in magnetic resonance (MR) for characterizing preclinical disease models. Methodical probing into preclinical animal models by MR is invaluable since it allows a careful interpretation and extrapolation of data derived from these models to human disease. In this review we will focus on the applications of cryogenic radiofrequency (RF) coils in small animal MR as a means of boosting image quality (e.

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Purpose: Implementation, evaluation and application of a pulse sequence for retrospectively-gated sodium magnetic resonance imaging of the human heart.

Methods: Measurements were conducted at a magnetic field strength of 7.0 Tesla.

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The objective of this work was to examine the feasibility of three-dimensional (3D) and whole heart coverage (23)Na cardiac MRI at 7.0 T including single-cardiac-phase and cinematic (cine) regimes. A four-channel transceiver RF coil array tailored for (23)Na MRI of the heart at 7.

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The purpose of this study was to evaluate the feasibility of an eight-channel dual-tuned transceiver surface RF coil array for combined (1)H/(19)F MR of the human knee at 7.0 T following application of (19)F-containing drugs. The (1)H/(19)F RF coil array includes a posterior module with two (1)H loop elements and two anterior modules, each consisting of one (1)H and two (19)F elements.

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