磁性纳米粒子组合的温度依赖磁力放松计
Soudabeh Arsalani1, Patricia Radon1, Dietmar Eberbeck1
1Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, D-10587 Berlin, Germany.
Physics in medicine and biology
|July 31, 2023
概括
磁性放松度成像 (MRXI) 使用磁纳米粒子 (MNP) 进行非侵入性成像. 这项研究确定了Synomag MNPs是MRXI的最佳选择,因为它在不同温度下产生一致的放松信号,从而使潜在的温度成像成为可能.
科学领域:
- 生物医学工程 生物医学工程
- 纳米技术纳米技术
- 医疗成像医学成像
背景情况:
- 磁性放松计成像 (MRXI) 是一种用于成像磁纳米粒子 (MNP) 的定量技术.
- 在MRXI中图像分辨率严重依赖于放松幅度 (ΔB).
- 了解不同温度下的MNP行为对于优化MRXI性能至关重要.
研究的目的:
- 评估商业磁纳米粒子 (MNP) 系统用于磁性放松计成像 (MRXI) 应用.
- 为了研究温度对MNP放松信号的影响,在流体和固定状态.
- 确定最适合的MNP系统,以提高MRXI分辨率并实现温度成像.
主要方法:
- 测量室温 (299 K) 放松信号的八个商业MNP系统在流体和固定状态.
- 研究了高温 (高达335K) 对四个MNP系统 (Synomag,Perimag,BNF,Nanomag) 的影响.
- 分析了温度,阻塞温度 (TB) 和放松幅度 (ΔB) 之间的关系.
主要成果:
- 流体MNP样本显示,随着温度的增加,ΔB显著下降.
- 固定MNP的行为有所不同: ΔB随着TB<299K的温度下降,而TB>299K则增加.
- 在两个状态中,Synomag在299K和335K之间呈现出始终高的ΔB,超过了其他系统.
结论:
- 由于其稳定的性能,Synomag是未来体外和体内MRXI研究的最佳MNP候选者.
- 温度显著影响MNP放松信号,在流体和固定状态下有不同的行为.
- MRXI显示了温度成像的可行性,为先进的诊断能力提供了潜力.
相关概念视频
Paramagnetism
2.5K
Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
2.5K
Atomic Nuclei: Nuclear Relaxation Processes
677
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis.
677
Ferromagnetism
2.4K
Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
2.4K
Magnetic Susceptibility and Permeability
1.2K
In linear magnetic materials, like paramagnets and diamagnets, magnetization is proportional to the magnetic field intensity. The constant of proportionality, a dimensionless number, is called magnetic susceptibility. The value of the susceptibility depends on the type of material.
When diamagnetic materials are placed under an external magnetic field, the moments opposite to the field are induced. Hence, the susceptibility for diamagnets has a minimal negative value of 10-5–10-6. Since...
When diamagnetic materials are placed under an external magnetic field, the moments opposite to the field are induced. Hence, the susceptibility for diamagnets has a minimal negative value of 10-5–10-6. Since...
1.2K
Atomic Nuclei: Types of Nuclear Relaxation
323
Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
323
Atomic Nuclei: Nuclear Spin State Population Distribution
1.0K
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
1.0K


