14 results on '"Thomas Wilhelm, Eigentler"'
Search Results
2. Radiofrequency applicator concepts for thermal magnetic resonance of brain tumors at 297 MHz (7.0 Tesla)
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Eva Oberacker, Andre Kuehne, Celal Oezerdem, Jacek Nadobny, Mirko Weihrauch, Marcus Beck, Sebastian Zschaeck, Cecilia Diesch, Thomas Wilhelm Eigentler, Helmar Waiczies, Pirus Ghadjar, Peter Wust, Lukas Winter, and Thoralf Niendorf
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rf hyperthermia ,thermal magnetic resonance ,hyperthermia treatment planning ,glioblastoma multiforme ,magnetic resonance imaging ,magnetic resonance thermometry ,Medical technology ,R855-855.5 - Abstract
Purpose 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). Reports on clinical applications of the APA technique in the brain are still missing. Ultrahigh field magnetic resonance (MR) employs higher frequencies than conventional MR and has potential to provide focal temperature manipulation, high resolution imaging and noninvasive temperature monitoring using an integrated RF applicator (ThermalMR). This work examines the applicability of RF applicator concepts for ThermalMR of brain tumors at 297 MHz (7.0 Tesla). Methods Electromagnetic field (EMF) simulations are performed for clinically realistic data based on GBM patients. Two algorithms are used for specific RF energy absorption rate based thermal intervention planning for small and large TVs in the brain, aiming at maximum RF power deposition or RF power uniformity in the TV for 10 RF applicator designs. Results For both TVs , the power optimization outperformed the uniformity optimization. The best results for the small TV are obtained for the 16 element interleaved RF applicator using an elliptical antenna arrangement with water bolus. The two row elliptical RF applicator yielded the best result for the large TV. Discussion This work investigates the capacity of ThermalMR to achieve targeted thermal interventions in model systems resembling human brain tissue and brain tumors.
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- 2020
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3. Radiofrequency antenna concepts for human cardiac MR at 14.0 T
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Thomas Wilhelm Eigentler, Christoph Stefan Aigner, Andre Kuehne, Sebastian Schmitter, Thoralf Niendorf, and Bilguun Nurzed
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Radiological and Ultrasound Technology ,Biophysics ,Radiology, Nuclear Medicine and imaging - Abstract
Objective To examine the feasibility of human cardiac MR (CMR) at 14.0 T using high-density radiofrequency (RF) dipole transceiver arrays in conjunction with static and dynamic parallel transmission (pTx). Materials and methods RF arrays comprised of self-grounded bow-tie (SGBT) antennas, bow-tie (BT) antennas, or fractionated dipole (FD) antennas were used in this simulation study. Static and dynamic pTx were applied to enhance transmission field (B1+) uniformity and efficiency in the heart of the human voxel model. B1+ distribution and maximum specific absorption rate averaged over 10 g tissue (SAR10g) were examined at 7.0 T and 14.0 T. Results At 14.0 T static pTx revealed a minimum B1+ROI efficiency of 0.91 μT/√kW (SGBT), 0.73 μT/√kW (BT), and 0.56 μT/√kW (FD) and maximum SAR10g of 4.24 W/kg, 1.45 W/kg, and 2.04 W/kg. Dynamic pTx with 8 kT points indicate a balance between B1+ROI homogeneity (coefficient of variation 1+ROI > 1.11 µT/√kW) at 14.0 T with a maximum SAR10g Discussion MRI of the human heart at 14.0 T is feasible from an electrodynamic and theoretical standpoint, provided that multi-channel high-density antennas are arranged accordingly. These findings provide a technical foundation for further explorations into CMR at 14.0 T.
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- 2023
4. Advanced Radio Frequency Applicators for Thermal Magnetic Resonance Theranostics of Brain Tumors
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Nandita Saha, Andre Kuehne, Jason M. Millward, Thomas Wilhelm Eigentler, Ludger Starke, Sonia Waiczies, and Thoralf Niendorf
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Cancer Research ,theranostics ,hyperthermia ,brain tumor ,MRI ,ThermalMR ,RF applicator ,Oncology ,Cardiovascular and Metabolic Diseases ,Technology Platforms - Abstract
Thermal Magnetic Resonance (ThermalMR) is a theranostic concept that combines diagnostic magnetic resonance imaging (MRI) with targeted thermal therapy in the hyperthermia (HT) range using a radiofrequency (RF) applicator in an integrated system. ThermalMR adds a therapeutic dimension to a diagnostic MRI device. Focused, targeted RF heating of deep-seated brain tumors, accurate non-invasive temperature monitoring and high-resolution MRI are specific requirements of ThermalMR that can be addressed with novel concepts in RF applicator design. This work examines hybrid RF applicator arrays combining loop and self-grounded bow-tie (SGBT) dipole antennas for ThermalMR of brain tumors, at magnetic field strengths of 7.0 T, 9.4 T and 10.5 T. These high-density RF arrays improve the feasible transmission channel count, and provide additional degrees of freedom for RF shimming not afforded by using dipole antennas only, for superior thermal therapy and MRI diagnostics. These improvements are especially relevant for ThermalMR theranostics of deep-seated brain tumors because of the small surface area of the head. ThermalMR RF applicators with the hybrid loop+SGBT dipole design outperformed applicators using dipole-only and loop-only designs, with superior MRI performance and targeted RF heating. Array variants with a horse-shoe configuration covering an arc (270°) around the head avoiding the eyes performed better than designs with 360° coverage, with a 1.3 °C higher temperature rise inside the tumor while sparing healthy tissue. Our EMF and temperature simulations performed on a virtual patient with a clinically realistic intracranial tumor provide a technical foundation for implementation of advanced RF applicators tailored for ThermalMR theranostics of brain tumors.
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- 2023
5. Cardiorenal sodium MRI at 7.0 Tesla using a 4/4 channel 1 H/ 23 Na radiofrequency antenna array
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Helmar Waiczies, Thoralf Niendorf, Florian von Knobelsdorff-Brenkenhoff, Erdmann Seeliger, Thomas Wilhelm Eigentler, Jeanette Schulz-Menger, Stephanie Funk, Daniel Wenz, Andre Kuehne, Laura Boehmert, and Armin M. Nagel
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Electromagnetic field ,Materials science ,Sodium ,chemistry.chemical_element ,Specific absorption rate ,Cardiorenal syndrome ,medicine.disease ,030218 nuclear medicine & medical imaging ,Antenna array ,03 medical and health sciences ,0302 clinical medicine ,Nuclear magnetic resonance ,chemistry ,medicine ,Sodium MRI ,Radiology, Nuclear Medicine and imaging ,Penetration depth ,030217 neurology & neurosurgery ,Radiofrequency coil - Abstract
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 (1 H/23 Na) RF array tailored for cardiorenal MRI at 7.0 Tesla (T) for a better physiometabolic understanding of cardiorenal syndrome. Methods The dual-frequency RF array is composed of a planar posterior section and a modestly curved anterior section, each section consisting of 2 loop elements tailored for 23 Na MR and 2 loopole-type elements customized for 1 H MR. Numerical electromagnetic field and specific absorption rate simulations were carried out. Transmission field ( B 1 + ) uniformity was optimized and benchmarked against electromagnetic field simulations. An in vivo feasibility study was performed. Results The proposed array exhibits sufficient RF characteristics, B 1 + homogeneity, and penetration depth to perform 23 Na MRI of the heart and kidney at 7.0 T. The mean B 1 + field for sodium in the heart is 7.7 ± 0.8 µT/√kW and in the kidney is 6.9 ± 2.3 µT/√kW. The suitability of the RF array for 23 Na MRI was demonstrated in healthy subjects (acquisition time for 23 Na MRI: 18 min; nominal isotropic spatial resolution: 5 mm [kidney] and 6 mm [heart]). Conclusion This work provides encouragement for further explorations into densely packed multichannel transceiver arrays tailored for 23 Na MRI of the heart and kidney. Equipped with this technology, the ability to probe sodium concentration in the heart and kidney in vivo using 23 Na MRI stands to make a critical contribution to deciphering the complex interactions between both organs.
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- 2019
6. 32-Channel self-grounded bow-tie transceiver array for cardiac MR at 7.0T
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Thomas Wilhelm, Eigentler, Andre, Kuehne, Laura, Boehmert, Sebastian, Dietrich, Antje, Els, Helmar, Waiczies, and Thoralf, Niendorf
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Male ,Phantoms, Imaging ,Radio Waves ,Humans ,Female ,Heart ,Equipment Design ,Signal-To-Noise Ratio ,Magnetic Resonance Imaging - Abstract
Design, implementation, evaluation, and application of a 32-channel Self-Grounded Bow-Tie (SGBT) transceiver array for cardiac MR (CMR) at 7.0T.The array consists of 32 compact SGBT building blocks. Transmission field (The compact SGBT building block facilitates a modular high-density array that supports accelerated and high spatial resolution CMR at 7.0T. The array provides a technological basis for future clinical assessment of parallel transmission techniques.
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- 2021
7. Simultaneous T
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Carl J J, Herrmann, Antje, Els, Laura, Boehmert, Joao, Periquito, Thomas Wilhelm, Eigentler, Jason M, Millward, Sonia, Waiczies, Joseph, Kuchling, Friedemann, Paul, and Thoralf, Niendorf
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Multiple Sclerosis ,Phantoms, Imaging ,Reference Values ,Brain ,Humans ,Magnetic Resonance Imaging - Abstract
The characteristic MRI features of multiple sclerosis (MS) lesions make it conceptually appealing to pursue parametric mapping techniques that support simultaneous generation of quantitative maps of 2 or more MR contrast mechanisms. We present a modular rapid acquisition with relaxation enhancement (RARE)-EPI hybrid that facilitates simultaneous TIn 2in1-RARE-EPI the first echoes in the echo train are acquired with a RARE module, later echoes are acquired with an EPI module. To define the fraction of echoes covered by the RARE and EPI module, an error analysis of TThere was a good agreement between TThis work demonstrates the feasibility of radially (under)sampled 2in1-RARE-EPI for simultaneous T
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- 2021
8. Multi-Channel RF Supervision Module for Thermal Magnetic Resonance Based Cancer Therapy
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Haopeng Han, Eckhard Grass, Andre Kuehne, Shuailin Wang, Eva Oberacker, Thomas Wilhelm Eigentler, and Thoralf Niendorf
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Cancer Research ,Computer science ,lcsh:RC254-282 ,Article ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,glioblastoma multiforme ,0302 clinical medicine ,Electricity meter ,Dielectric heating ,power meter ,Electronic engineering ,patient displacement ,thermal magnetic resonance ,Focal point ,Amplifier ,RF power amplifier ,lcsh:Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,hyperthermia ,Power (physics) ,radio frequency heating ,Oncology ,Cardiovascular and Metabolic Diseases ,phase meter ,030220 oncology & carcinogenesis ,hyperthermia treatment planning ,Radio frequency ,Technology Platforms ,Energy (signal processing) - Abstract
Simple Summary Glioblastoma multiforme (GBM) is the most lethal brain tumor. Combining hyperthermia with chemotherapy and/or radiotherapy improves survival of GBM patients. For radio frequency (RF)-induced hyperthermia, the RF signals’ power and phase need to be supervised to achieve a precise formation of the power deposition focal point, accurate thermal dose control, and safety management. Patient position during treatment also needs to be monitored to ensure the efficiency of the treatment and to avoid adverse effects in healthy tissue. This work demonstrates the development, implementation, evaluation, validation, and application of a multi-channel RF supervision module that meets the technical requirements of hyperthermia and provides a cost-effective solution for broad-band RF signal supervision and patient monitoring. It is a key component for a hyperthermia hardware system and facilitates future thermal magnetic resonance applications that integrate RF-induced heating, in vivo temperature mapping, and anatomic and functional imaging in a single RF applicator. Abstract Glioblastoma multiforme (GBM) is the most lethal and common brain tumor. Combining hyperthermia with chemotherapy and/or radiotherapy improves the survival of GBM patients. Thermal magnetic resonance (ThermalMR) is a hyperthermia variant that exploits radio frequency (RF)-induced heating to examine the role of temperature in biological systems and disease. The RF signals’ power and phase need to be supervised to manage the formation of the energy focal point, accurate thermal dose control, and safety. Patient position during treatment also needs to be monitored to ensure the efficacy of the treatment and avoid damages to healthy tissue. This work reports on a multi-channel RF signal supervision module that is capable of monitoring and regulating RF signals and detecting patient motion. System characterization was performed for a broad range of frequencies. Monte-Carlo simulations were performed to examine the impact of power and phase errors on hyperthermia performance. The supervision module’s utility was demonstrated in characterizing RF power amplifiers and being a key part of a feedback control loop regulating RF signals in heating experiments. Electromagnetic field simulations were conducted to calculate the impact of patient displacement during treatment. The supervision module was experimentally tested for detecting patient motion to a submillimeter level. To conclude, this work presents a cost-effective RF supervision module that is a key component for a hyperthermia hardware system and forms a technological basis for future ThermalMR applications.
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- 2021
9. Design, Implementation, Evaluation and Application of a 32-Channel Radio Frequency Signal Generator for Thermal Magnetic Resonance Based Anti-Cancer Treatment
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Haopeng Han, Thomas Wilhelm Eigentler, Shuailin Wang, Egor Kretov, Lukas Winter, Werner Hoffmann, Eckhard Grass, Thoralf Niendorf, and Technische Universität Berlin
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Cardiovascular and Metabolic Diseases ,radio frequency signal generator ,radio frequency antenna ,ddc:610 ,Technology Platforms ,lcsh:Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,610 Medizin und Gesundheit ,thermal magnetic resonance ,hyperthermia ,lcsh:RC254-282 ,Article ,radio frequency heating - Abstract
Thermal Magnetic Resonance (ThermalMR) leverages radio frequency (RF)-induced heating to examine the role of temperature in biological systems and disease. To advance RF heating with multi-channel RF antenna arrays and overcome the shortcomings of current RF signal sources, this work reports on a 32-channel modular signal generator (SGPLL). The SGPLL was designed around phase-locked loop (PLL) chips and a field-programmable gate array chip. To examine the system properties, switching/settling times, accuracy of RF power level and phase shifting were characterized. Electric field manipulation was successfully demonstrated in deionized water. RF heating was conducted in a phantom setup using self-grounded bow-tie RF antennae driven by the SGPLL. Commercial signal generators limited to a lower number of RF channels were used for comparison. RF heating was evaluated with numerical temperature simulations and experimentally validated with MR thermometry. Numerical temperature simulations and heating experiments controlled by the SGPLL revealed the same RF interference patterns. Upon RF heating similar temperature changes across the phantom were observed for the SGPLL and for the commercial devices. To conclude, this work presents the first 32-channel modular signal source for RF heating. The large number of coherent RF channels, wide frequency range and accurate phase shift provided by the SGPLL form a technological basis for ThermalMR controlled hyperthermia anti-cancer treatment.
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- 2020
10. Cover Image
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Thomas Wilhelm Eigentler, Lukas Winter, Haopeng Han, Eva Oberacker, Andre Kuehne, Helmar Waiczies, Sebastian Schmitter, Laura Boehmert, Christian Prinz, Hana Dobsicek Trefna, and Thoralf Niendorf
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Molecular Medicine ,Radiology, Nuclear Medicine and imaging ,Spectroscopy - Published
- 2020
11. Wideband Self‐Grounded Bow‐Tie Antenna for Thermal MR
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Eva Oberacker, Thomas Wilhelm Eigentler, Hana Dobsicek Trefna, Haopeng Han, Sebastian Schmitter, Helmar Waiczies, Lukas Winter, Andre Kuehne, Christian Prinz, Thoralf Niendorf, and Laura Boehmert
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Electromagnetic field ,Materials science ,Radio Waves ,Acoustics ,Thermometry ,Bow tie ,Imaging phantom ,030218 nuclear medicine & medical imaging ,magnetic resonance ,self‐grounded bow‐tie ,03 medical and health sciences ,Electromagnetic Fields ,0302 clinical medicine ,broadband antenna ,Broadband ,Dielectric heating ,Humans ,Computer Simulation ,Radiology, Nuclear Medicine and imaging ,ddc:610 ,Wideband ,thermal magnetic resonance ,Spectroscopy ,radiofrequency antenna ,ultrahigh field MR ,Phantoms, Imaging ,Specific absorption rate ,Magnetic Resonance Imaging ,thermal intervention ,Molecular Medicine ,Protons ,Antenna (radio) ,610 Medizin und Gesundheit ,030217 neurology & neurosurgery - Abstract
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-1) MRI, fluorine (F-19) 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. RF transmission (B-1(+)) field efficiency and specific absorption rate (SAR) were obtained in a phantom, and the thigh of human voxel models (Ella, Duke) for H-1 and F-19 MRI at 7.0 T. B-1(+) efficiency simulations were validated with actual flip-angle imaging measurements. The feasibility of thermal intervention was examined by temperature simulations (f = 300, 400 and 500 MHz) in a phantom. The RF heating intervention (P-in = 100 W, t = 120 seconds) was validated experimentally using the proton resonance shift method and fiberoptic probes for temperature monitoring. The applicability of the SGBT RF antenna building block for in vivo H-1 and F-19 MRI was demonstrated for the thigh and forearm of a healthy volunteer. The SGBT RF antenna building block facilitated F-19 and H-1 MRI at 7.0 T as well as broadband thermal intervention (234-561 MHz). For the thigh of the human voxel models, a B-1(+) efficiency >= 11.8 mu T/root kW was achieved at a depth of 50 mm. Temperature simulations and heating experiments in a phantom demonstrated a temperature increase Delta T >7 K at a depth of 10 mm. The compact SGBT antenna building block provides technology for the design of integrated high-density RF applicators and for the study of the role of temperature in (patho-) physiological processes by adding a thermal intervention dimension to an MRI device (Thermal MR).
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- 2020
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12. Cardiorenal sodium MRI at 7.0 Tesla using a 4/4 channel
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Laura, Boehmert, Andre, Kuehne, Helmar, Waiczies, Daniel, Wenz, Thomas Wilhelm, Eigentler, Stephanie, Funk, Florian, von Knobelsdorff-Brenkenhoff, Jeanette, Schulz-Menger, Armin M, Nagel, Erdmann, Seeliger, and Thoralf, Niendorf
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Male ,Phantoms, Imaging ,Radio Waves ,Transducers ,Magnetic Resonance Imaging, Cine ,Reproducibility of Results ,Torso ,Heart ,Kidney ,Electromagnetic Fields ,Image Processing, Computer-Assisted ,Feasibility Studies ,Humans ,Female ,Sodium Isotopes ,Protons - Abstract
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 (The dual-frequency RF array is composed of a planar posterior section and a modestly curved anterior section, each section consisting of 2 loop elements tailored forThe proposed array exhibits sufficient RF characteristics,This work provides encouragement for further explorations into densely packed multichannel transceiver arrays tailored for
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- 2019
13. Toward
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Christian, Prinz, Paula Ramos, Delgado, Thomas Wilhelm, Eigentler, Ludger, Starke, Thoralf, Niendorf, and Sonia, Waiczies
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Isoflurane ,Toluidines ,Phantoms, Imaging ,Temperature ,Hydroxybutyrates ,Fluorine ,Hyperthermia, Induced ,Thermometry ,Fluorine-19 Magnetic Resonance Imaging ,Flupenthixol ,Mice, Inbred C57BL ,Mice ,Pharmaceutical Preparations ,Crotonates ,Crown Ethers ,Nitriles ,Image Processing, Computer-Assisted ,Animals ,Fiber Optic Technology ,Nanoparticles ,Female ,Spin Labels - Abstract
This study examines the influence of the environmental factor temperature on theStudies on PFCE, isoflurane, teriflunomide, and flupentixol showed a relationship between temperature and their physicochemical characteristics, namely, chemical shift, TThe impact of temperature on the
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- 2018
14. Toward 19F magnetic resonance thermometry: spin–lattice and spin–spin-relaxation times and temperature dependence of fluorinated drugs at 9.4 T
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Ludger Starke, Paula Ramos Delgado, Thoralf Niendorf, Christian Prinz, Thomas Wilhelm Eigentler, and Sonia Waiczies
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In vivo magnetic resonance spectroscopy ,Materials science ,Radiological and Ultrasound Technology ,Solid-state physics ,Biophysics ,Spin–lattice relaxation ,Nanoparticle ,Ether ,Fluorine-19 NMR ,030218 nuclear medicine & medical imaging ,Flupentixol ,Spin–spin relaxation ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Nuclear magnetic resonance ,chemistry ,medicine ,Radiology, Nuclear Medicine and imaging ,medicine.drug - Abstract
This study examines the influence of the environmental factor temperature on the 19F NMR characteristics of fluorinated compounds in phantom studies and in tissue. 19F MR mapping and MR spectroscopy techniques were used to characterize the 19F NMR characteristics of perfluoro-crown ether (PFCE), isoflurane, teriflunomide, and flupentixol. T1 and T2 mapping were performed, while temperature in the samples was changed (T = 20–60 °C) and monitored using fiber optic measurements. In tissue, T1 of PFCE nanoparticles was determined at physiological temperatures and compared with the T1-measured at room temperature. Studies on PFCE, isoflurane, teriflunomide, and flupentixol showed a relationship between temperature and their physicochemical characteristics, namely, chemical shift, T1 and T2. T1 of PFCE nanoparticles was higher at physiological body temperatures compared to room temperature. The impact of temperature on the 19F NMR parameters of fluorinated compounds demonstrated in this study not only opens a trajectory toward 19F MR-based thermometry, but also indicates the need for adapting MR sequence parameters according to environmental changes such as temperature. This will be an absolute requirement for detecting fluorinated compounds by 19F MR techniques in vivo.
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