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Magnetic Nanoparticles for Cancer Diagnosis
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
R. G. Aswathy, D. Sakthi Kumar
T1 longitudinal relaxation (spin-lattice relaxation) signifies the speed of magnetization that is parallel to static magnetic field recovery after inducing a disruption. Rapidly relaxing protons (short T1) recover complete magnetization along the longitudinal axis and yield high intensity signal. Complete magnetization on the longitudinal axis is not redeemed for protons that relax slowly (long T1) before successive RF pulses, and generally produce a low intensity signals [32]. T2 transverse relaxation (spin-spin relaxation) signifies how fast magnetization in the plane perpendicular to static magnetic field losses the phase coherence. When RF pulse is applied, proton nuclei spin in phase and after the pulse, the magnetic fields of all the nuclei interact and the energy is exchanged. The nuclei lose their phase coherence and spin in random manner [33].
Contrast enhancement agents and radiopharmaceuticals
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
MR contrast agents work by altering the magnetic environment (magnetic susceptibility) of the local tissue and are not directly visualised. This is unlike iodinated contrast agents that function by their ability to directly alter the image, being additive to the normal tissue attenuation. Many substances exist that possess inherent magnetic characteristics and the choice has to be based on the ability to produce these compounds in a physiologically acceptable form. The criteria for such compounds is that they affect the following parameters: Proton density.Spin–lattice relaxation time, T1.Spin–spin relaxation time, T2.Flow.
Future Developments of NMR Imaging
Published in Bertil R. R. Persson, Freddy Ståhlberg, Health and Safety of Clinical NMR Examinations, 2019
Bertil R. R. Persson, Freddy Ståhlberg
Trace amounts of paramagnetic metal ions have been shown to reduce the Tl relaxation time of nuclei in the surrounding environment due to the strong electron-nuclear magnetic moment interaction. This property can be utilized advantageously in the development of contrast agents that can be used to shorten the spin-lattice relaxation time, Tl, in specific tissues or organs.
Magnetic resonance imaging T1 indices of the brain as biomarkers of inhaled manganese exposure
Published in Critical Reviews in Toxicology, 2022
N. Jensen, R. Terrell, S. Ramoju, N. Shilnikova, N. Farhat, N. Karyakina, B. H. Cline, F. Momoli, D. Mattison, D. Krewski
Due to the large magnetic moment of Mn, owing to its five unpaired electrons, the presence of Mn ions in the brain shortens the T1-relaxation time and increase T1-weighted signal intensity on magnetic resonance imaging (MRI) (Kim 2004). As such, the deposition of Mn in the brain can be detected with T1-weighted MRI, a noninvasive clinical test (Zheng et al. 2011; Kwakye et al. 2015). T1-weighted MRI is thought to be a useful noninvasive marker of Mn exposure (Zheng et al. 2011). The imaging process involves placing the object into an external static magnetic field which produces magnetization within it, the direction of this magnetization can be altered by pulses of radiofrequency radiation (Fitsanakis et al. 2006). The magnetization returns to the direction of the original static magnetic field after the pulse occurs, the time associated with this return is called the spin lattice relaxation time or T1 (Fitsanakis et al. 2006). As Mn is a paramagnetic substance, it shortens the T1 relaxation time and increases the intensity of the signal obtained on MRI (Fitsanakis et al. 2006).
Capsules from synthetic diblock-peptides as potential artificial oxygen carriers
Published in Journal of Microencapsulation, 2021
Huayang Feng, Jürgen Linders, Sascha Myszkowska, Christian Mayer
The molecular diffusion in the capsule dispersion was studied with PFG-NMR. The NMR experiments were run on a Bruker Avance Neo II 500 MHz spectrometer (Bruker BioSpin, Rheinstetten, Germany) at a fluorine resonance frequency of 470 Hz. Simple single-pulse excitation was used to obtain fluorine line spectra. An external standard was used for a reliable determination of the chemical shifts. Spin-lattice relaxation times were determined in a conventional inversion recovery experiment. 19F-NMR diffusion experiments were run with a Bruker DIFBBI probe head. All measurements were performed at 298 K. For all measurements, the stimulated echo pulse sequence with two gradient pulses was used. A total number of 96 scans were accumulated for each setting. The time between two gradient pulses Δ was 25 ms. The gradients were adjusted to strengths G between 1 and 600 G/cm with a duration δ of 1.0 ms. All measurements (the full set of gradient strengths under the variation from 1 to 600 G/cm) were repeated two times.
Free radical formation in chloramphenicol heated at different temperatures and the best thermal sterilization conditions – application of EPR spectroscopy and UV spectrophotometry
Published in Pharmaceutical Development and Technology, 2018
The parameters of the EPR spectra of chloramphenicol heated at different temperatures and times changed with microwave power used during the measurements of the lines. The changes in amplitudes (A) of chloramphenicol thermally treated at the three condition sets with increasing microwave power are shown in Figure 5(a–c). Amplitudes (A) of EPR lines of the heated chloramphenicol increased with increases in microwave power and remained unsaturated up to microwave power of 70 mW (Figure 5(a–c)). These results suggest fast spin-lattice relaxation processes in the analysed samples. The broadening of EPR lines of chloramphenicol with increasing microwave power was observed (Figure 6(a–c)). The increase in linewidths (ΔBpp) of the EPR lines with an increase in microwave power is characteristic of homogenously broadened spectra9. Fast spin-lattice relaxation processes have been observed in thermally treated streptomycin12, sisomycin12, paromomycin12 and piperacylin12. EPR spectra of the other thermally treated drugs are usually homogeneously broadened1,2,12,13.