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Instrumentation, sequences and applications for magnetic particles in imaging and spectroscopy
Citation Link: https://doi.org/10.15480/882.13690
Publikationstyp
Doctoral Thesis
Date Issued
2024
Sprache
English
Author(s)
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2024-11-15
TORE-DOI
Citation
Technische Universität Hamburg (2024)
As an emerging medical imaging modality, magnetic particle imaging (MPI) has demonstrated considerable potential in imaging scenarios where established techniques are limited or have adverse effects. However, it still faces several challenges for future clinical integration and for achieving theoretical predictions of performance. MPI is a quantitative, tracer-based, and indirect imaging technique, that measures the non-linear response of magnetic nanoparticles (MNPs) at high temporal and spatial resolution with very high sensitivity. Major milestones such as the in vivo measurement of a beating mouse heart in 2009 or the first MPI-tailored MNPs in the same year, have been complemented by progress in various disciplines that constitute the research field of MPI. These include image reconstruction, signal encoding, MNP synthesis, applications and hardware instrumentation as main categories. Today, real-time reconstructions are feasible for perfusion imaging, as well as simultaneous measurement and signal separation of different MNP systems, and intentional interaction of MNPs with their immediate environment by mechanical activation, hyperthermia or targeted drug delivery.
Initial progress toward the development of a full-scale, human-sized system by the Philips research division in Hamburg, Germany, in 2015 was accompanied by a number of challenges. The enormous engineering effort included the development of instrumentation needed to generate strong alternating and static magnetic fields in a cost-effective and maintainable manner, with a complexity similar to that of an Magnetic Resonance Imaging (MRI) system. Ultimately, the project struggled to maintain funding. At the Institute of Biomedical Imaging, Hamburg University of Technology, the challenge in instrumentation was addressed on a smaller scale, but still within the range of human proportions. A human-sized head scanner was introduced in 2019 that incorporated numerous straightforward solutions to previous difficulties, benefiting from smaller components and lower electrical specifications. A significant aspect of this thesis is the comprehensive redesign of this head-sized imaging system to align with clinical standards in terms of 3D acquisition speed, safety, and resolution. The design process incorporates both feasibility and clinical trial requirements, and achievable results are highlighted for an approved, but inferior, Ferucarbotran-based tracer. One part of this thesis is devoted to an in-depth examination of the transmit-receive signal chain of the device, accompanied by a comprehensive account of the development and design process of a high current linear toroidal transformer. The high-gain transformer can also be utilized in applications beyond medical imaging, operating in the kHz range, such as wireless power transmission. Another section in the present thesis investigates the suitability of a novel Ferucarbotran tracer, its MPI signal quality, composition, and performance in comparison to other MNPs.
In the fields of neurology and interventional radiology, a head-sized imaging system can be employed for the prompt diagnosis of various types of stroke, including ischemic stroke, which represents a significant cause of mortality in the context of cardiovascular disease. Intracerebral hemorrhage represents the second most common type of stroke for which perfusion imaging serves as an invaluable diagnostic tool. Our head-sized imaging system may facilitate long-term monitoring of such patients. In this study, we propose a negative contrast perfusion imaging technique based on a long-circulating tracer and a saline bolus, which enables the repeated generation of trackable dynamic changes in MNP concentration without increasing the total administered iron dose. It leverages several significant advantages of MPI over other modalities, including its sensitivity, linearity, and high temporal resolution for 3D volume tracking, enabling not only concentration changes but also the rate of these processes to be monitored. Given the limited iron uptake by the liver and spleen, reducing the administered dose is a crucial aspect to consider for repeated monitoring of an individual patient.
MNP spectrometry is a highly valuable tool during the preclinical stage of MPI, as it allows for the assessment and evaluation of the non-linear response and relaxation behavior with high signal quality and low noise in homogeneous fields. Concerning the instrumentation of MNP spectrometry, this work presents an arbitrary waveform magnetic particle spectrometer (MPS) for the purpose of measuring and emulating data, including the development and calibration of the device. This spectrometer is capable of measuring particles in a variety of excitation and offset fields. The data is then processed by a custom software framework, which assembles a realistic dataset that can be used for complex sequence emulation. In particular, the device can be utilized to assess different excitation types, MPI signal encoding, saturation behavior, and the magnetization behavior of nanoparticles on a small scale with short measuring times, typically below one minute.
Initial progress toward the development of a full-scale, human-sized system by the Philips research division in Hamburg, Germany, in 2015 was accompanied by a number of challenges. The enormous engineering effort included the development of instrumentation needed to generate strong alternating and static magnetic fields in a cost-effective and maintainable manner, with a complexity similar to that of an Magnetic Resonance Imaging (MRI) system. Ultimately, the project struggled to maintain funding. At the Institute of Biomedical Imaging, Hamburg University of Technology, the challenge in instrumentation was addressed on a smaller scale, but still within the range of human proportions. A human-sized head scanner was introduced in 2019 that incorporated numerous straightforward solutions to previous difficulties, benefiting from smaller components and lower electrical specifications. A significant aspect of this thesis is the comprehensive redesign of this head-sized imaging system to align with clinical standards in terms of 3D acquisition speed, safety, and resolution. The design process incorporates both feasibility and clinical trial requirements, and achievable results are highlighted for an approved, but inferior, Ferucarbotran-based tracer. One part of this thesis is devoted to an in-depth examination of the transmit-receive signal chain of the device, accompanied by a comprehensive account of the development and design process of a high current linear toroidal transformer. The high-gain transformer can also be utilized in applications beyond medical imaging, operating in the kHz range, such as wireless power transmission. Another section in the present thesis investigates the suitability of a novel Ferucarbotran tracer, its MPI signal quality, composition, and performance in comparison to other MNPs.
In the fields of neurology and interventional radiology, a head-sized imaging system can be employed for the prompt diagnosis of various types of stroke, including ischemic stroke, which represents a significant cause of mortality in the context of cardiovascular disease. Intracerebral hemorrhage represents the second most common type of stroke for which perfusion imaging serves as an invaluable diagnostic tool. Our head-sized imaging system may facilitate long-term monitoring of such patients. In this study, we propose a negative contrast perfusion imaging technique based on a long-circulating tracer and a saline bolus, which enables the repeated generation of trackable dynamic changes in MNP concentration without increasing the total administered iron dose. It leverages several significant advantages of MPI over other modalities, including its sensitivity, linearity, and high temporal resolution for 3D volume tracking, enabling not only concentration changes but also the rate of these processes to be monitored. Given the limited iron uptake by the liver and spleen, reducing the administered dose is a crucial aspect to consider for repeated monitoring of an individual patient.
MNP spectrometry is a highly valuable tool during the preclinical stage of MPI, as it allows for the assessment and evaluation of the non-linear response and relaxation behavior with high signal quality and low noise in homogeneous fields. Concerning the instrumentation of MNP spectrometry, this work presents an arbitrary waveform magnetic particle spectrometer (MPS) for the purpose of measuring and emulating data, including the development and calibration of the device. This spectrometer is capable of measuring particles in a variety of excitation and offset fields. The data is then processed by a custom software framework, which assembles a realistic dataset that can be used for complex sequence emulation. In particular, the device can be utilized to assess different excitation types, MPI signal encoding, saturation behavior, and the magnetization behavior of nanoparticles on a small scale with short measuring times, typically below one minute.
Subjects
Magnetic Particle Imaging | Hardware Development | Instrumentation | Arbitrary Waveform Spectrometer | Inductive Coupling Network | Human-sized head scanner | Resotran | Negative Contrast
DDC Class
616.07: Pathology
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