Decoupling: theory and practice. I. Current methods and recent concepts.

Background: To improve quality of surgery in oncology, it is necessary to completely remove the tumor, including its metastases, to minimize injury to normal tissues and to reduce duration of an intervention. Modern methods of detection based on radiological computerized tomography and magnetic resonance imaging can identify a tumor after its volume has become big enough, i.e. it contains more than 10 billion cells. Therefore, an improvement of sensitivity and resolution ability of diagnostic tools to identify early stages of malignant neoplasms seems of utmost importance. Aim: To demonstrate the potential of a new class of anti-Stokes luminescence nanoparticles for deep optical imaging with high contrast of malignant tumors. Materials and methods: Upconversion nanoparticles with narrow dispersion and a size of 70 to 80 nm, with a core/shell structure of NaYF4:Yb3+:Tm3+/NaYF4 were used in the study. The nanoparticles have an intensive band of anti-Stokes photoluminescence at a wavelength of 800 nm under irradiation with a wavelength of 975 nm (both wavelengths are within the transparency window for biological tissues). The conversion coefficient of the excitation radiation into the anti-Stokes luminescence was 9%. To increase the time during which nanoparticles can circulate in blood flow of small animals, the nanoparticles were covered by a biocompatible amphiphilic polymer shell. As a tumor model we used Lewis epidermoid carcinoma transfected to mice. Results: We were able to obtain stable water colloids of nanoparticles covered with amphiphilic polymer that could preserve their initial size at least for one month. The use of upconversion nanoparticles with a hydrophilic shell made of intermittent maleic anhydride and octadecene co-polymer with subsequent coating with diglycidyl polyethylene glycol ether allowed for reduction of non-specific reaction of nanoparticles with plasma proteins. In its turn, it resulted in an increased time of their circulation in blood flow of small animals for up to 1 hour. With the Lewis lung carcinoma transfected to mice model we demonstrated аn in-life transportation of upconversion nanoparticles into the tumor with a high degree of localization due to a passive EPR effect. The contrast of luminescent signal in the tumor compared to adjacent tissues was at least 70%. The possibility of visualization of upconverted nanoparticles up to 15 mm of biological tissue was shown. Conclusion: The optical imaging techniques with anti-Stokes photoluminescent markers ensure a high contract real-time detection of tumor tissues that allows for their use for intra-operative diagnostics.

This paper presents a new reconfigurable carrier leakage canceler for UHF RFID readers, using a directional coupler and an impedance tuning circuit to improve the sensitivity of the receiver. The impedance tuning circuit, which consists of electrically tunable passive components, can be adaptively tuned to have an optimum reflection coefficient for carrier leakage cancellation. In order to secure the good carrier leakage cancellation performance over the wide operating frequency band, PIN and varactor diodes are used as a variable resistor and a capacitor, respectively, for the impedance tuning circuit. The implemented reconfigurable carrier leakage canceler exhibits more than 65 dB of carrier leakage cancellation over a wide frequency band of 100 MHz, from 860 to 960 MHz when the control voltages of the PIN and varactor diodes are adjusted. As a result, a 15 dB improvement of receiver sensitivity, and 30% improvement of the recognition range have been achieved, respectively, using commercial RFID tags.

Mueller Polarimetric Imaging (MPI) showed promising results in biomedical applications, especially for early detection of precancerous lesions on biological tissues. This technique is label-free, non-invasive and can be implemented with a large field of view (up to several cm2) to image wide areas of biological tissues while providing information on its microstructure. The development of innovative (MPI) systems, able to analyze biological tissues in vivo on human patients, remains an instrumental challenge. Our goal is to build miniaturized and compact full-field MPI systems based on Ferroelectric Liquid Crystals (FLCs) capable of performing a multispectral accurate analysis of biological tissues in vivo. In this work, an innovative approach is showed to realize optimized and fast FLCs-based MPI systems able to perform full-field imaging acquisitions in the spectral range between 450 and 700nm with error less than 1% on all the elements of measured Mueller matrices. This system can be accurately calibrated by using the Eigenvalue Calibration Method (ECM) also in presence of high residual instrumental depolarization. This approach enables us to realize compact and reliable MPI systems which can be easily integrated into existing instruments currently used in medical practice.

Traditional Magnetic Induction Tomography (MIT) systems demonstrate limited spatial resolution and detection sensitivity when analyzing complex conductivity distributions in biological tissues. This research investigates the integration of Nitrogen-Vacancy (NV) centers in diamond substrates to overcome these fundamental limitations. The primary objectives include: (1) developing a quantum-enhanced MIT system with superior magnetic field detection capabilities, (2) quantifying performance improvements in spatial resolution and sensitivity compared to conventional approaches, (3) validating system effectiveness through controlled phantom studies and biological tissue analysis, and (4) establishing technological foundations for next-generation medical imaging applications. This study presents the first comprehensive implementation of quantum sensing technology in tomographic imaging applications. Novel contributions include: development of an integrated NV-center based magnetic field detection system, achievement of 0.8 mm minimum detectable feature size representing 3.5-fold resolution enhancement, demonstration of 0.01 S/m conductivity detection threshold showing 10-fold sensitivity improvement, and validation of 62% reconstruction error reduction with 28% structural similarity enhancement. The quantum-enhanced approach establishes new paradigms for early disease detection and precision medicine applications, providing unprecedented imaging capabilities for medical diagnostics, material characterization, and geophysical exploration. Results demonstrate transformative potential for clinical implementation with 95% sensitivity and 92% specificity in detecting sub-millimeter tissue anomalies

The possible association of dental amalgam surface exposure, brain mercury (Hg) levels, and pathological markers of Alzheimer's disease (AD) in the brain is the subject of an on-going study in our laboratory. Two radiochemical neutron activation analysis methods and the use of instrumental neutron activation analysis (INAA) with Compton suppression spectrometry have been evaluated for improving our INAA Hg detection limit (2.8±0.6 ng/g, wet-weight basis) in human tissue. Large numbers of samples dictated the use of a purely instrumental method or rapid, simple radiochemical separations. Human brain tissues and NIST biological standards were analyzed using a precipitation of Hg2Cl2, a solvent extraction utilizing sodium diethyldithiocarbomate, conventional INAA, and INAA with Compton suppression. The radiochemical precipitation of Hg2Cl2 proved to be the most useful method for use in our study because it provided a simultaneous, quantitative determination of silver (Ag) and a Hg detection limit in brain tissue of 1.6±0.1 ng/g (wet-weight basis).

Introduction: Neurological injuries significantly impair quality of life by disrupting neural transmission. Traditional implantable stimulators often rely on internal batteries, which limit device longevity and necessitate repeated surgical interventions. Objective: This study presents the experimental validation of a battery-free, RFID-powered neural platform for peripheral nerve signal acquisition and stimulation, targeting TRL-6 validation. Methods: The prototype incorporates an adjustable analog front-end with gains up to 93 dB and a biphasic current-controlled stimulator. Validation was performed through benchtop testing, biological tissue assessments using porcine tissue, and functional in vivo trials in adult Wistar rats (n = 3) over a three-month period. Results: Benchtop evaluation confirmed gain accuracy with errors below 2.2 dB and precise stimulation timing. The system maintained a stable 3.3 V wireless power link through 20 mm of biological tissue using RFID. In vivo experiments indicated a 100% functional success rate (51/51 trials) in eliciting gross motor responses via wireless stimulation. Thermal safety was confirmed, with a maximum operating temperature of 28 °C, remaining well below physiological limits. Conclusions: The results demonstrate the functional feasibility of a battery-free, RFID-powered neural interface for wireless signal acquisition and stimulation, supporting system-level validation of this architecture.

Iontronic bioelectronics provides a powerful framework for bridging the mismatch between conventional electronic systems and soft, ion‐mediated biological tissues. By harnessing mobile ions as charge carriers and functional mediators, iontronic devices enable biocompatible, conformal, and low‐impedance interfaces that support both signal acquisition and therapeutic delivery. Recent advances in ionic materials, such as hydrogels, ion gels, and ionic liquids, have facilitated high‐fidelity physiological sensing, wound monitoring, and programmable drug and ion release. In addition to passive sensing and delivery, emerging iontronic platforms integrate real‐time biosignal monitoring with adaptive, AI‐guided feedback to enable closed‐loop therapeutic control. This review highlights the multifunctional role of ions in sensing, modulation, and stimulation across diverse applications, including skin‐interfaced electronics, neural and cardiac interfaces, and wound therapy. Key challenges such as operational stability, signal specificity, and long‐term biocompatibility are further examined, and material, structural, and system‐level innovations that are paving the way toward intelligent, responsive, and clinically viable iontronic bioelectronic platforms are discussed.

Sensitive determination of pheomelanin after 5-carboxyfluorescein succinimidyl ester precapillary derivatization and micellar electrokinetic capillary chromatography with laser-induced fluorescence detection

To propose a strategy for reducing radiofrequency (RF) power deposition by stochastic proton decoupling based on Rayleigh's theorem. Rayleigh's theorem was used to remove frequency components of stochastic decoupling over the 3.90-6.83 ppm range. [2-(13)C] or [2,5-(13) C(2) ]glucose was infused intravenously to anesthetized rats. (13)C labeling of brain metabolites was detected in the carboxylic/amide spectral region at 11.7 T using either the original stochastic decoupling method developed by Ernst or the proposed windowed stochastic decoupling method. By restricting frequency components of stochastic decoupling to 1.91-3.90 ppm and 6.83-7.60 ppm spectral regions decoupling power deposition was reduced by ≈50%. The proposed windowed stochastic decoupling scheme is experimentally demonstrated for in vivo (13)C MRS of rat brain at 11.7 T. The large reduction in decoupling power deposition makes it feasible to perform stochastic proton decoupling at very high magnetic fields for human brain (13)C MRS studies.

In the last few years there has been rapid progress in the application of nuclear magnetic resonance clinical imaging as a diagnostic aid (Partain et al, 1983; Steiner, 1983; Worthington, 1983). Records kept by the operators of NMR imaging equipment indicate that about 1800 individuals have now been examined without incident within the United Kingdom. In view of this progress, an advisory group (Appendix) appointed by the National Radiological Protection Board recommends some modifications to the original advice given in 1981 (NRPB, 1981). The principal modifications are that: (1) It is no longer considered necessary to exclude volunteers with a history of epilepsy or cardiac disease. (2) It is not obligatory that a registered medical practitioner trained in resuscitation techniques be present during an exposure. (3) Higher limits are recommended for rates of change of magnetic flux density when the period of change is less than 10 ms. (4) The radiofrequency limit of 15 MHz has been removed. Theoretical considerations indicate that the interaction of an applied magnetic field with the intrinsic magnetic moments of protons and electrons within a molecule could alter its rate of chemical reaction (McLauchlan, 1981). Chemical reactions involving radical pair intermediates are expected to be sensitive to magnetic fields for this reason and a number of enzyme reactions that might be expected to be affected have been identified (A. Cass, personal communication). However, there is no experimental confirmation of these theoretical possibilities at present.

The high contrast and high resolution photoacoustic tomography was used to image the gold nanoshell clearance in rat brain in vivo. With our current imaging system, the acquisition of photoacoustic signals is realized through a circular scan of a single-element transducer. Therefore, the data acquisition is slow. In this case, an improved simultaneous iterative reconstruction algorithm was developed to reduce the acquisition time by using limited data in the experiments. This algorithm is based on the least square principle; it can be used to reconstruct high quality images from the limited data containing much noise. Furthermore, it is always convergent. So it can improve the imaging quality comparison with conventional filter back-projection algorithm (FBP) and algebraic reconstruction algorithm (ART). Here we accurately mapped rat brain structures with gold nanoshell contrast agents. We also imaged the clearance of gold nanoshell in the rat brain. It provides an accurate non-invasive monitoring method for fluid pathways in biological tissues, which makes photoacoustic tomography as a powerful method for imaging pathologic tumor vessels, delineating neovascularization, and studying global and regional hemodynamic activities in the brain.

This paper describes a biological application for split spectrum processing (SSP). The ultrasonic control of cryosurgery has been reported previously. It was demonstrated chat the echo of the advancing freezing front could be detected during a freeze-thaw cycle. However, the speckle noise can mask the target signal, leading to difficulties in its detection. In this study, a SSP algorithm with a minimisation technique was implemented and compared to linear bandpass filtering. The optimum set of processing parameters for SSP (half-power bandwidth and number of filters, location of the bank of bandpass filters) and for linear filtering (half-power bandwidth and centre frequency) were determined experimentally. Both filtering techniques were successful in locating the target. However, optimum SNR enhancement and axial resolution were achieved with the non-linear minimisation algorithm, which permits rapid and automatic detection of the moving freezing front during cryosurgery

Photoacoustic imaging (PAI) used for noninvasive imaging of biological tissue has been reported in many literature. However, there are still some disadvantages in the novel technique, such as the poor efficiency of imaging. In the current PAI, multiple excitation of laser and multiple acquisition of signal are necessary for image reconstruction. In this case, laser pulses may injure biological tissue due to energy accumulation. To popularize PAI in clinical applications, it is necessary to develop a new imaging approach to increase the efficiency of PAI. A spatial phase-controlled algorithm is presented for full-field three-dimensional (3D) image reconstruction. By using the algorithm, photoabsorption sources at different depths can be reconstructed using just one set of data acquired in single laser shot. Unfocused plane transducer array and parallel data-acquisition (PDA) equipment are used for real-time photoacoustic (PA) signal detection and acquisition. The spatial resolution of the 3D PAI system was analyzed. Two graphite rods at various positions in a simulation model and two bifurcate vessels in the ear of rabbit were imaged. In addition, the motion trace of one particle flowing at constant velocity was captured dynamically. Experimental results showed that spatial phase-controlled algorithm based on plane transducer array and PDA system was capable of static and dynamic 3D PAI. Spatial phase-controlled algorithm is introduced for 3D image reconstruction. The PA signals are collected by plane transducer array and PDA system in single pulse excitation. The acquired volumetric data are sufficient for 3D image reconstruction. Therefore, tissue can avoid the long-term exposure to light source and it is safer than the current PAI for in vivo imaging. With an increase in the repetition rate of laser pulse and speed of image display, the imaging method will realize real-time 3D imaging, which will be significant in clinical detection and medical diagnosis.

In order to meet the requirements of miniaturization, wide frequency band and low-profile antennas for electromagnetic environment monitoring area, we designed a miniaturized Archimedes spiral antenna for USRP electromagnetic signal acquisition system. Antenna is sine-wave meandered based on the traditional Archimedean spiral antenna to reduce the antenna size. After optimizing the structure parameters, the antenna with a radius of 60mm and a thickness of 2mm was fabricated. The measurement results show that: in 400MHz-4.5GHz frequency range, the antenna has good impedance characteristics with VSWR ≤ 2, and has an ultra-wide-band, as well as great directivity and omnidirectional radiation feature. Finally, the antenna was applied to the USRP(Universal Software Radio Peripheral) and an environmental monitoring experiment was conducted. The results show that the antenna can receive electromagnetic signals of 400MHz-4.5GHz, and has potential application in electromagnetic environment monitoring area.

Partial discharge (PD) is a localized dielectric breakdown in high- voltage insulation systems that can lead to catastrophic equipment failure if undetected. Early and accurate detection of PD is critical in ensuring the reliability and longevity of high-voltage equipment such as transformers, GIS (Gas Insulated Switchgear), and cables. Traditional sensors and narrowband antenna systems have limited sensitivity and frequency range, making them less effective for detecting weak PD signals over wide spectra. The narrow operational bandwidth and low sensitivity of conventional PD detection systems impede accurate localization and characterization of PD phenomena, especially under noisy or variable frequency conditions. There is a pressing need for a robust detection mechanism that combines broad frequency response with high detection sensitivity. This study proposes a Broadband Antenna System specifically designed for PD signal acquisition. The system incorporates a log-periodic dipole array (LPDA) antenna integrated with a low-noise amplifier (LNA), coupled to a high-speed digitizer. The LPDA provides ultra-wideband coverage from 50 MHz to 1.5 GHz, enabling the capture of various PD signatures. Finite Element Method (FEM)-based simulations in CST Microwave Studio validate the antenna design. Real-time testing is performed in a controlled high-voltage laboratory environment using a 100 kV test transformer and calibrated PD sources. The proposed antenna system demonstrated a 25% improvement in sensitivity and a 40% increase in detection range compared to standard narrowband antennas. It accurately detected PD pulses with charge magnitudes as low as 5 pC under noisy environments.