共查询到20条相似文献,搜索用时 31 毫秒
1.
Signal intensities of longitudinally detected ESR (LODESR) of 1,1-diphenyl-2-picrylhydrazyl powder were precisely measured
at 250 to 950 MHz under a constant magnetic field microwave that was applied using a single-turn coil. The LODESR signal intensity
was reduced linearly due to smaller Zeeman splitting. Because the noise level was constant, the sensitivity of LODESR was
approximately proportional to the resonant frequency. As far as we know, this study represents the first attempt to measure
precisely the relationship between the signal intensities and resonant frequencies of ESR in an experimental condition. 相似文献
2.
By using a narrow single electron spin resonance (ESR) line agent, triarylmethyl, tris(8-carboxy-2,2,6,6-tetrahydroxyethylbenzo[1,2-d:4,5-d′]
bis(1,3)dithiole-4-yl)methyl sodium salt (TAM OX063), pulsed longitudinally detected ESR (LODESR) measurements of a phantom
or the chest of a living mouse at the operating frequency of ca. 300 MHz were taken and the effective longitudinal relaxation
time (T
1*) was estimated for oximetry. Under irradiation of a pair of π-pulses with a variable interval between pulses (τ), in-phase
LODESR signal intensities were obtained from the phantoms containing TAM dissolved in a physiological saline solution at a
concentration of 1 mM and various concentrations of oxygen. TheT
1* of the phantom was calculated from the plotted curve of the LODESR signal intensity against τ. It was found that the reciprocal
ofT
1*, i.e., the longitudinal relaxation rate, increased with the concentration of oxygen. In vivo pulsed LODESR measurements of
the chest of living mice that had received a TAM injection via the intraperitoneal route were made. While the LODESR measurements
were being made, the mice in one group breathed normal air and those in another group breathed 100% oxygen. It was found that
the longitudinal relaxation rate of the mice breathing 100% oxygen was significantly greater than that of mice breathing normal
air, indicating that breathing 100% oxygen elevates the thoracic longitudinal relaxation rate. 相似文献
3.
Panagiotelis I Nicholson I Hutchison JM 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,149(1):74-84
Longitudinally detected ESR (LODESR) involves transverse ESR irradiation with a modulated source and observing oscillations in the spin magnetization parallel to the main magnetic field. In this study, radiofrequency-LODESR was used for oximetry by measuring the relaxation times of the electron. T1e and T2e were measured by investigating LODESR signal magnitude as a function of detection frequency. We have also predicted theoretically and verified experimentally the LODESR signal phase dependence on detection frequency and relaxation times. These methods are valid even for inhomogeneous lines provided that T1e>T2e. We have also developed a new method for measuring T1e, valid for inhomogeneous spectra, for all values of T1e and T2e, based on measuring the spectral area as a function of detection frequency. We have measured T1e and T2e for lithium phthalocyanine crystals, for the nitroxide TEMPOL, and for the single line agent Triarylmethyl (TAM). Furthermore, we have collected spectra from aqueous solutions of TEMPOL and TAM at different oxygen concentrations and confirmed that T1e values are reduced with increased oxygen concentration. We have also measured the spin-lattice electronic relaxation time for degassed aqueous solutions of the same agents at different agent concentrations. T1e decreases as a function of concentration for TAM while it remains independent of free radical concentration for TEMPOL, a major advantage for oxygen mapping. This method, combined with the ability of LODESR to provide images of exogenous free radicals in vivo, presents an attractive alternative to the conventional transverse ESR linewidth based oximetry methods. 相似文献
4.
A. Colligiani M. Giordano D. Leporini M. Lucchesi M. Martinelli L. Pardi S. Santucci 《Applied magnetic resonance》1992,3(1):107-129
Multiple-quantum spectroscopies are reviewed in the frame of electron paramagnetic resonance. Some properties of different nonlinear techniques are discussed for both transverse and longitudinal detection. The connections of effects recently presented with the procedure of longitudinal detection of electron paramagnetic resonance (LODESR) in presence of double transverse irradiation are stressed. Peculiarities of LODESR spectroscopy and its capabilities in facing problems related to relaxations in presence of very slow dynamic processes are evidentiated. Recent results show the vitality of the LODESR technique, that in the future could be applied to new fields, owing to experimental updating. 相似文献
5.
Yokoyama H Sato T Ohya H Kamada H 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,150(2):194-197
A new magnetometer utilizing a longitudinally detected ESR (LODESR) method was developed. The probe head of the LODESR magnetometer is equipped with a single-turn coil (8 mm in diameter) which has a very wide bandwidth because the reactance of the coil is always smaller than the resistance of the transmission line (50 ohm) at frequencies less than 700 MHz. Thus, an absolute magnetic field could be measured over a wide range (2 to 9 mT) using this magnetometer without changing the probe head. 相似文献
6.
The design and evaluation of a multilayered element resonator (MLR), which consists of multiple layers of half-loop conductor plates and insulator sheets, are presented. An MLR and a bridge shielded loop-gap resonator (BLGR), which have similar sizes and resonant frequencies, were fabricated to compare their performances. Using the MLR and the BLGR, the modulation field width and signal intensity of a phantom containing a nitroxide radical were measured by employing a continuous-wave electron spin resonance (CW-ESR) technique at a radio frequency of 300 MHz. Using the same resonators, the longitudinally detected ESR (LODESR) signal intensities of the phantom were also compared. The loadedQ values of the resonators were almost the same. The modulation widths in the MLR were significantly wider than those in the BLGR when the modulation coils were driven at the same voltage. The signal intensities of CW-ESR and LODESR from the phantom in the MLR were significantly greater than those from the BLGR. Since eddy currents disturb the penetration of the modulation field in CW-ESR or detection of changes in magnetization in LODESR observations, these results show that, in the MLR, the eddy currents were suppressed to a greater degree than in the BLGR. 相似文献
7.
Hidekatsu Yokoyama Toshiyuki Sato Tateaki Ogata Hiroaki Ohya-Nishiguchi Hitoshi Kamada 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,129(2):201-206
A signal detector of longitudinally detected ESR (LODESR) is independent of the resonant frequency. We developed anin vivoLODESR spectrometer operating in the regions of 300, 700, and 900 MHz. Using this apparatus, we estimated signal intensities at different operating frequencies obtained from non- or high-dielectric loss phantoms that contained nitroxide radical solutions and from live rats that had received a nitroxide radical. Our result, higher signal intensities in the high-dielectric loss samples (such as physiological saline solution and animals) at a lower frequency, shows that the influence of a decrease in dielectric loss dominates over the signal reduction caused by smaller Zeeman splitting. We believe that this finding strongly supports anin vivoESR resonant frequency that tends to be low. 相似文献
8.
Steven K. Cool Koen Breyne Evelyne Meyer Stefaan C. De Smedt Niek N. Sanders 《Journal of fluorescence》2013,23(5):909-920
In vivo optical imaging has become a popular tool in animal laboratories. Currently, many in vivo optical imaging systems are available on the market, which often makes it difficult for research groups to decide which system fits their needs best. In this work we compared different commercially available systems, which can measure both bioluminescent and fluorescent light. The systems were tested for their bioluminescent and fluorescent sensitivity both in vitro and in vivo. The IVIS Lumina II was found to be most sensitive for bioluminescence imaging, with the Photon Imager a close second. Contrary, the Kodak system was, in vitro, the most sensitive system for fluorescence imaging. In vivo, the fluorescence sensitivity of the systems was similar. Finally, we examined the added value of spectral unmixing algorithms for in vivo optical imaging and demonstrated that spectral unmixing resulted in at least a doubling of the in vivo sensitivity. Additionally, spectral unmixing also enabled separate imaging of dyes with overlapping spectra which were, without spectral unmixing, not distinguishable. 相似文献
9.
Optically deviated focusing method based high-speed SD-OCT for in vivo retinal clinical applications
Ruchire Eranga Wijesinghe Kibeom Park Pilun Kim Jaeryung Oh Seong-Woo Kim Kwangtae Kim Beop-Min Kim Mansik Jeon Jeehyun Kim 《Optical Review》2016,23(2):307-315
The aim of this study is to provide accurately focused, high-resolution in vivo human retinal depth images using an optically deviated focusing method with spectral-domain optical coherence tomography (SD-OCT) system. The proposed method was applied to increase the retinal diagnosing speed of patients with various values of retinal distances (i.e., the distance between the crystalline eye lens and the retina). The increased diagnosing speed was facilitated through an optical modification in the OCT sample arm configuration. Moreover, the optical path length matching process was compensated using the proposed optically deviated focusing method. The developed system was mounted on a bench-top cradle to overcome the motion artifacts. Further, we demonstrated the capability of the system by carrying out in vivo retinal imaging experiments. The clinical trials confirmed that the system was effective in diagnosing normal and abnormal retinal layers as several retinal abnormalities were identified using non-averaged single-shot OCT images, which demonstrate the feasibility of the method for clinical applications. 相似文献
10.
11.
The concept of a multispectral confocal microscope for in vivo imaging is introduced. To demonstrate the concept we modified a slit-scan fluorescence confocal microendoscope incorporating a fiber-optic catheter for in vivo imaging to record multispectral images. The system was designed to examine cellular structures during optical biopsy and to exploit the diagnostic information contained within the spectral domain. Preliminary experiments were carried out in phantoms and cell cultures to demonstrate the potential of the technique. 相似文献
12.
Non-invasive Near Infrared Fluorescence Imaging of CdHgTe Quantum Dots in Mouse Model 总被引:2,自引:1,他引:1
Near infrared CdHgTe quantum dots (QDs) acted as biomarker for in vivo imaging were synthesized in aqueous solution. The size
and the fluorescence wavelength of the synthesized quantum dots can be arbitrary manipulated by using different refluxing
time. In particular, the fluorescence wavelength was extended to near infrared range (700∼900 nm), which make the in vivo
imaging possible. Meanwhile, the characteristics, such as morphology, size, spectra, stability and toxicity were investigated.
The dynamic bio-distribution, clearance from blood, liver and intestine in living animal were in vivo monitored by a NIR imaging
system. The circulation of CdHgTe QDs in living mice was addressed semi-quantitatively according to the changes of fluorescence
intensity. The high stability as well as high fluorescence intensity makes QDs particular interested candidates for in vivo
imaging studies. 相似文献
13.
An in vivo photoacoustic imaging system was designed and implemented to image the entire small animal head. A special scanning gantry was designed to enable in vivo imaging in coronal cross sections with high contrast and good spatial resolution for the first time to our knowledge. By use of a 2.25 MHz ultrasonic transducer with a 6 mm diameter active element, an in-plane radial resolution of approximately 312 microm was achieved. Deeply seated arterial and venous vessels in the head measuring up to 1.7 cm in diameter were simultaneously imaged in vivo with 804 nm wavelength laser excitation of photoacoustic waves. 相似文献
14.
15.
We propose an intrinsic optical method for in vivo neural recording using optic fiber-based surface plasmon resonance (SPR) phenomena. The fiber-based SPR method is electrical artifact free, labeling free, and feasible for a portable system compared with conventional in vivo neural recording systems. We simultaneously detected SPR signals and electrical neural activity from the rat somatosensory cortex evoked by electrical stimulation on the forepaw. Pharmacological analysis using a voltage-gated sodium channel blocker confirmed the neural origins of the optical signals. This fiber-based SPR system promises the enhanced ability to record in vivo neural activity for the investigation of neurons and their networks. 相似文献
16.
17.
A quadrature transmit/receive birdcage coil was optimized for squirrel monkey functional imaging at the high field of 9.4 T. The coil length was chosen to gain maximum coil efficiency/signal-to-noise ratio (SNR) and meanwhile provide enough homogenous RF field in the whole brain area. Based on the numerical simulation results, a 16-rung high-pass birdcage coil with the optimal length of 9 cm was constructed and evaluated on phantom and in vivo experiments. Compared to a general-purpose non-optimized coil, it exhibits approximately 25% in vivo SNR improvement. In addition to the volume coil, details about how to design and construct the associated animal preparation system were provided. 相似文献
18.
Hirata H Walczak T Swartz HM 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,142(1):159-167
The automatic frequency control (AFC) circuit in conventional electron paramagnetic resonance (EPR) spectrometers automatically tunes the microwave source to the resonance frequency of the resonator. The circuit works satisfactorily for samples stable enough that the geometric relations in the resonance structure do not change in a significant way. When EPR signals are measured during in vivo experiments with small rodents, however, the distance between the signal source and the surface-coil detector can change rapidly. When a conventional AFC circuit keeps the oscillator tuned to the resonator under those conditions, the resultant frequency change may exceed +/-5 MHz and markedly shift the position of the EPR signal. Such a shift results in unacceptable effects on the spectra, especially when the experimenter is dealing with narrow EPR lines. The animal movement also causes a mismatching of the resonator and the 50-ohm transmission line. Direct results of this mismatching are increased noise; shifts in the position of the baseline; and a high probability of overdriving the signal preamplifier with consequent loss of the EPR signal. We therefore designed, built, and tested a new surface-coil resonator using varactor diodes for tuning the resonance frequency to the fixed frequency oscillator and for capacitive matching of the resonator to the 50-ohm transmission line. The performance of the automatic matching system was tested in vivo by measuring EPR spectra of lithium phthalocyanine implanted in rats. Stability and sensitivity of the spectrometer were evaluated by measuring EPR spectra with and without the use of the automatic matching system. The overall experimental performance of the spectrometer was found to significantly improve during in vivo experiments using the automatic matching system. Excellent matching between the 50-ohm transmission line and the resonator was maintained under all experimental circumstances that were tested. This should allow us now to carry out experiments that previously were not possible. 相似文献
19.
Rapid near-infrared Raman spectroscopy system for real-time in vivo skin measurements 总被引:1,自引:0,他引:1
A rapid dispersive-type near-infrared (NIR) Raman spectroscopy system and a Raman probe were developed to facilitate real-time, noninvasive, in vivo human skin measurements. Spectrograph image aberration was corrected by a parabolic-line fiber array, permitting complete CCD vertical binning, thereby yielding a 3.3-16-fold improvement in signal-to-noise ratio. Good quality in vivo cutaneous NIR Raman spectra free of interference from fiber fluorescence and silica Raman scattering can be acquired in less than 1 s, which greatly facilitates practical noninvasive tissue characterization and clinical diagnosis. 相似文献
20.
PurposeA fast spin-echo sequence based on the Periodically Rotated Overlapping Parallel Lines with Enhanced Reconstruction (PROPELLER) technique is a magnetic resonance (MR) imaging data acquisition and reconstruction method for correcting motion during scans. Previous studies attempted to verify the in vivo capabilities of motion-corrected PROPELLER in real clinical situations. However, such experiments are limited by repeated, stray head motion by research participants during the prescribed and precise head motion protocol of a PROPELLER acquisition. Therefore, our purpose was to develop a brain phantom set for motion-corrected PROPELLER.Materials and methodsThe profile curves of the signal intensities on the in vivo T2-weighted image (T2WI) and 3-D rapid prototyping technology were used to produce the phantom. In addition, we used a homemade driver system to achieve in-plane motion at the intended timing. We calculated the Pearson's correlation coefficient (R2) between the signal intensities of the in vivo T2WI and the phantom T2WI and clarified the rotation precision of the driver system. In addition, we used the phantom set to perform initial experiments to show the rotational angle and frequency dependences of PROPELLER.ResultsThe in vivo and phantom T2WIs were visually congruent, with a significant correlation (R2) of 0.955 (p < .001). The rotational precision of the driver system was within 1 degree of tolerance. The experiment on the rotational angle dependency showed image discrepancies between the rotational angles. The experiment on the rotational frequency dependency showed that the reconstructed images became increasingly blurred by the corruption of the blades as the number of motions increased.ConclusionsIn this study, we developed a phantom that showed image contrasts and construction similar to the in vivo T2WI. In addition, our homemade driver system achieved precise in-plane motion at the intended timing. Our proposed phantom set could perform systematic experiments with a real clinical MR image, which to date has not been possible in in vivo studies. Further investigation should focus on the improvement of the motion-correction algorithm in PROPELLER using our phantom set for what would traditionally be considered problematic patients (children, emergency patients, elderly, those with dementia, and so on). 相似文献