SCIENTIFIC JOURNALS
All the publications authored by Carlos G. Juan in scientific journals are listed below in chronological order. If you would need further information or documentation, please do not hesitate to contact him.
C.G. Juan, B. Potelon, A. Aquino, H. García-Martínez, C. Quendo, "Multi-parameter simultaneous extraction with a novel microwave sensor based on coupled resonators," Scientific Reports, vol. 14, Art. No. 23076, 2024.
Editor: Nature
DOI: 10.1038/s41598-024-72061-3
Impact Factor: 3.8
Quartile: Q1 (Multidisciplinary)
Abstract—This work presents a microwave resonant multi‐parameter sensor devoted to the simultaneous extraction of three characteristics of a homogeneous solid sample: its dielectric permittivity, its loss tangent and its thickness. The device is composed of three coupled resonators in two different substrate boards, having the sample between the boards, in a sandwich configuration. Presence of the sample impacts the electrical response of the device, not only influencing resonators, but also by affecting inter‐resonator couplings. A method to analyse the response of the device, allowing for the extraction of the desired characteristics of the sample is proposed, as well as an experimental calibration procedure. The model is built upon 990 simulations, calibrated with three reference‐ samples measurements and then tested over 18 experimental measurements, with good results, thereby validating the multi‐parameter sensing approach.
A. Martínez-Lozano, R. Gutierrez, C.G. Juan, C. Blanco-Angulo, H. García-Martínez, G. Torregrosa, J.M. Sabater-Navarro, E. Ávila-Navarro, "Microwave imaging system based on signal analysis in a planar environment for detection of abdominal aortic aneurysms," Biosensors, vol. 14, no. 3, p. 149, 2024.
Editor: MDPI
DOI: 10.3390/bios14030149
Impact Factor: 5.4
Quartile: Q1 (Instruments & Instrumentation)
Abstract—A proof-of-concept of a microwave imaging system for the fast detection of abdominal aortic aneurysms is shown. This experimental technology seeks to overcome the factors hampering the fast screening for these aneurysms with the usual equipment, such as high cost, long-time operation or hazardous exposure to chemical substances. The hardware system is composed of 16 twin antennas mastered by a microcontroller through a switching network, which connects the antennas to the measurement instrument for sequential measurement. The software system is run by a computer, mastering the whole system, automatizing the measurement process and running the signal processing and medical image generation algorithms. Two image generation algorithms are tested: Delay-and-Sum (DAS) and Improved Delay-and-Sum (IDAS). Own-modified versions of these algorithms adapted to the requirements of our system are proposed. The system is carefully calibrated and fine-tuned with known objects placed at known distances. An experimental proof-of-concept is shown with a human torso phantom, including an aorta phantom and an aneurysm phantom placed in different positions. The results show good imaging capabilities with the potential for detecting and locating possible abdominal aortic aneurysms and reporting acceptable errors.
A. Martínez-Lozano, C. Blanco-Angulo, A. Rodríguez-Martínez, C.G. Juan, H. García-Martínez, J.M. Sabater-Navarro, E. Ávila-Navarro, "Toward intraoperative brain-shift detection through microwave imaging system," IEEE Transactions on Instrumentation and Measurement, vol. 72, p. 4011411, 2023.
Editor: IEEE
Impact Factor: 5.6
Quartile: Q1 (Instruments & Instrumentation; Engineering, Electrical and Electronic)
Abstract—This work shows a proof of concept of a radar-based microwave imaging (MWI) system for the detection of the brain-shift effect with minimum delay. The system is based on the estimation of the variations of both the position and the geometry of the brain in order to detect if remarkable variations have occurred. To that end, the system makes use of 12 twin antennas as sensing elements, which transmit broadband signals toward the patient’s head and receive the corresponding reflections. Printed monopole antennas with coplanar feed are considered, featuring a broad bandwidth and an omnidirectional radiation pattern. A signal processing strategy to estimate the detected distances to the target from the reflection seen by each antenna is also shown, as well as a calibration and fine-tuning procedure for accurate distance detection capabilities. To demonstrate the potential of the system, a cranium phantom and several brain phantoms, emulating different brain-shift cases, are fabricated and measured. The results show the effective detection of the brain-shift in all the cases under consideration, thereby demon- strating the potential of MWI systems for effective intraoperative brain-shift detection.
C.G. Juan, E. Bronchalo, B. Potelon, C. Quendo, V.F. Muñoz, J.M. Ferrández-Vicente, J.M. Sabater-Navarro, "On the selectivity of planar microwave glucose sensors with multicomponent solutions," Electronics, vol. 12, no. 1, p. 191, 2023.
Editor: MDPI
DOI: 10.3390/electronics12010191
Impact Factor: 2.690
Quartile: Q2 (Engineering, Electrical and Electronic)
Abstract—The development of glucose concentration sensors by means of microwave planar resonant technology is an active field attracting considerable attention from the scientific community. Although showing promising results, the current experimental sensors are facing some fundamental challenges. Among them, the most critical one seems to be the selectivity of glucose concentration against the variations of the concentrations of other components or parameters. In this article, we investigate the selectivity of microwave planar resonant sensors when measuring multicomponent solutions. Three sensors are involved, two of them having been designed looking for a more simplified system with a reduced size, and the third one has been specially developed to improve the sensitivity. The performance of these sensors is thoroughly assessed with a large set of measurements involving multicomponent solutions composed of pure water, NaCl, albumin at different concentrations and glucose at different concentrations. The impact of the simultaneous variations of the concentrations of glucose and albumin on the final measurements is analyzed, and the effective selectivity of the sensors is discussed. The results show a clear influence of the albumin concentration on the measurements of the glucose concentration, thereby pointing to a lack of selectivity for all sensors. This influence has been modeled, and strategies to manage this selectivity challenge are inferred.
C. Blanco-Angulo, A. Martínez-Lozano, R. Gutiérrez-Mazón, C.G. Juan, H. García-Martínez, J. Arias-Rodríguez, J.M. Sabater-Navarro and E. Ávila-Navarro, "Non-Invasive Microwave-Based Imaging System for Early Detection of Breast Tumours," Biosensors, vol. 12, no. 9, p. 752, 2022.
Editor: MDPI
DOI: 10.3390/bios12090752
Impact Factor: 5.743
Quartile: Q1 (Instruments & Instrumentation)
Abstract—This work introduces a microwave-based system able to detect tumours in breast phantoms in a non-invasive way. The data acquisition system is composed of a hardware system which involves high-frequency components (antennas, switches and cables), a microcontroller, a vector network analyser used as measurement instrument and a computer devoted to the control and automation of the operation of the system. Concerning the software system, the computer runs a Python script which is in charge of mastering and automatising all the required stages for the data acquisition, from initialisation of the hardware system to performing and saving the measurements. We also report on the design of the high-performance broadband antenna used to carry out the measurements, as well as on the algorithm employed to build the final medical images, based on an adapted version of the so-called Improved Delay-and-Sum (IDAS) algorithm improved by a Hamming window filter and averaging preprocessing. The calibration and start-up of the system are also described. The experimental validation includes the use of different tumour models with different dielectric properties inside the breast phantom. The results show promising tumour detection capabilities, even when there is low dielectric contrast between the tumoural and healthy tissues, as is the usual case for dense breasts in young women.
C. Blanco-Angulo, A. Martínez-Lozano, C.G. Juan, R. Gutiérrez-Mazón, J. Arias-Rodríguez, E. Ávila-Navarro, and J.M. Sabater-Navarro, "Validation of an RF image system for real-time tracking neurosurgical tools," Sensors, vol. 22, no. 10, p. 3845, 2022.
Editor: MDPI
DOI: 10.3390/s19194311
Impact Factor: 3.576
Quartile: Q1 (Instruments & Instrumentation)
Abstract—A radio frequency (RF)-based system for surgical navigation is presented. Surgical navigation technologies are widely used nowadays for aiding the surgical team with many interventions. However, the currently available options still pose considerable limitations, such as line-of-sight occlusion prevention or restricted materials and equipment allowance. In this work, we suggest a different approach based on a microwave broadband antenna system. We combine techniques from microwave medical imaging, which can overcome the current limitations in surgical navigation technologies, and we propose methods to develop RF-based systems for real-time tracking neurosurgical tools. The design of the RF system to perform the measurements is shown and discussed, and two methods (Multiply and Sum and Delay Multiply and Sum) for building the medical images are analyzed. From these measurements, a surgical tool’s position tracking system is developed and experimentally assessed in an emulated surgical scenario. The reported results are coherent with other approaches found in the literature, while overcoming their main practical limitations. The discussion of the results discloses some hints on the validity of the system, the optimal configurations depending on the requirements, and the possibilities for future enhancements.
C.G. Juan, B. Potelon, C. Quendo, H. García-Martínez, E. Ávila-Navarro, E. Bronchalo, and J.M. Sabater-Navarro "Study of Qu-based resonant microwave sensors and design of 3-D-printed devices dedicated to glucose monitoring," IEEE Transactions on Instrumentation and Measurement, vol. 70, p. 8005716, 2021.
Editor: IEEE
Impact Factor: 4.016
Quartile: Q1 (Instruments & Instrumentation; Engineering, Electrical and Electronic)
Abstract—A low-cost, additively manufactured, biocompatible glucose sensor based on the changes in the unloaded quality factor (Qu) with a single split-ring resonator is presented. An exposition of the fundamentals for the use of the Qu as sensing parameter with microwave planar resonant sensors is shown. The convenience of this sensing parameter is analyzed from the theoretical point of view, and practical design and optimization guidelines are inferred with a special focus on the optimization of Qu sensitivity to glucose concentration. For practical demonstration and experimental assessment, a novel inverted microstrip configuration is considered, built upon a customized structure made with a certified biocompatible material thanks to 3-D printing techniques, which is aimed to provide for a stronger interaction between the electromagnetic fields and the sample. Two metallization solutions are investigated, yielding devices operating at 4.50 and 4.62 GHz, with operating Qu of 16.36 and 22.00, relative Qu sensitivities of 1.377 and 2.727, Qu sensitivities to glucose content within the physiological range of 0.3 × 10^(−3) per mg/dL and 0.6 × 10^(−3) per mg/dL, sensing areas of approximately 11.7 × 8.8 mm2 and total structure sizes of 950.0 × 35.0 × 3.5 mm3. The devices show good performance with water–glucose solutions covering a wide range of concentrations, involving physiological as well as industry-related ones.
C.G. Juan, B. Potelon, C. Quendo, and E. Bronchalo "Microwave planar resonant solutions for glucose concentration sensing: A systematic review," Applied Sciences, vol. 11, no. 15, p. 7018, 2021.
Editor: MDPI
DOI: 10.3390/app11157018
Impact Factor: 2.679
Quartile: Q2 (Physics, Applied; Engineering, Multidisciplinary)
See the FULL ARTICLE HERE, and DOWNLOAD THE FULL TEXT HERE.
Article Awarded with "2021 Highly Cited Paper Award" by Applied Sciences.
Abstract—The measurement of glucose concentration finds interesting potential applications in both industry and biomedical contexts. Among the proposed solutions, the use of microwave planar resonant sensors has led to remarkable scientific activity during the last years. These sensors rely on the changes in the dielectric properties of the medium due to variations in the glucose concentration. These devices show electrical responses dependent on the surrounding dielectric properties, and therefore the changes in their response can be related to variations in the glucose content. This work shows an up-to-date review of this sensing approach after more than one decade of research and development. The attempts involved are sorted by the sensing parameter, and the computation of a common relative sensitivity to glucose is proposed as general comparison tool. The manuscript also discusses the key points of each sensor category and the possible future lines and challenges of the sensing approach.
A. Aquino, C.G. Juan, B. Potelon, and C. Quendo, "Dielectric permittivity sensor based on planar open-loop resonator," IEEE Sensors Letters, vol. 5, no. 3, p. 3000204, 2021.
Editor: IEEE
DOI: 10.1109/LSENS.2021.3055544
Impact Factor: —
Quartile: —
Abstract—Accurate characterization of the dielectric properties of solids and, especially, substrates is crucial for circuitry design and development. For applications requiring low cost, wieldy systems, many attempts have been made involving planar resonant microwave devices. However, most of them have a configuration in which the sample is placed onto the substrate. As a novelty, a structure considering the sample placement into a more sensitive area is presented and analyzed in this letter. The design of this kind of sensors is discussed, and the measurement results are presented. The proposed device is shown to be capable of measuring the full complex permittivity of the sample, and the results compare well with other previous attempts.
D. Zambrana-Vinaroz, J.M. Vicente-Samper, C.G. Juan, V. Esteve-Sala, and J.M. Sabater-Navarro, "Non-invasive device for blood pressure wave acquisition by means of mechanical transducer," Sensors, vol. 19, no. 19, p. 4311, 2019.
Editor: MDPI
DOI: 10.3390/s19194311
Impact Factor: 3.275
Quartile: Q1 (Instruments & Instrumentation)
Abstract—Blood pressure wave monitoring provides interesting information about the patient’s cardiovascular function. For this reason, this article proposes a non-invasive device capable of capturing the vibrations (pressure waves) produced by the carotid artery by means of a pressure sensor encapsulated in a closed dome filled with air. When the device is placed onto the outer skin of the carotid area, the vibrations of the artery will exert a deformation in the dome, which, in turn, will lead to a pressure increase in its inner air. Then, the sensor inside the dome captures this pressure increase. By combining the blood pressure wave obtained with this device together with the ECG signal, it is possible to help the screening of the cardiovascular system, obtaining parameters such as heart rate variability (HRV) and pulse transit time (PTT). The results show how the pressure wave has been successfully obtained in the carotid artery area, discerning the characteristic points of this signal. The features of this device compare well with previous works by other authors. The main advantages of the proposed device are the reduced size, the cuffless condition, and the potential to be a continuous ambulatory device. These features could be exploited in ambulatory tests.
C.G. Juan, E. Bronchalo, B. Potelon, C. Quendo, and J.M. Sabater-Navarro, "Glucose concentration measurement in human blood plasma solutions with microwave sensors," Sensors, vol. 19, no. 17, p. 3779, 2019.
Editor: MDPI
DOI: 10.3390/s19173779
Impact Factor: 3.275
Quartile: Q1 (Instruments & Instrumentation)
Abstract—Three microwave sensors are used to track the glucose level of different human bloodplasma solutions. In this paper, the sensors are evaluated as glucose trackers in a context close to real human blood. Different plasma solutions sets were prepared from a human blood sample at several added glucose concentrations up to 10 wt%, adding also ascorbic acid and lactic acid at different concentrations. The experimental results for the different sensors/solutions combinations are presented in this work. The sensors show good performance and linearity as glucose level retrievers, although the sensitivities change as the rest of components vary. Different sensor behaviors depending upon the concentrations of glucose and other components are identified and characterized. The results obtained in terms of sensitivity are coherent with previous works, highlighting the contribution of glucose to the dielectric losses of the solution. The results are also consistent with the frequency evolution of the electromagnetic signature of glucose found in the literature, and are helpful for selecting frequency bands for sensing purposes and envisioning future approaches to the challenging measurement in real biological contexts. Discussion of the implications of the results and guidelines for further research and development of more accurate sensors is offered.
C.G. Juan, H. García, E. Ávila-Navarro, E. Bronchalo, V. Galiano, O. Moreno, D. Orozco, and J.M. Sabater-Navarro, "Feasibility study of portable microwave microstrip open-loop resonator for non-invasive blood glucose level sensing: proof of concept," Medical & Biological Engineering & Computing, vol. 57, no. 11, pp. 2389–2405, 2019.
Editor: Springer
DOI: 10.1007/s11517-019-02030-w
Impact Factor: 2.039
Quartile: Q2 (Mathematical & Computational Biology)
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Abstract—Self-management of blood glucose level is part and parcel of diabetes treatment, which involves invasive, painful and uncomfortable methods. A proper non-invasive blood glucose monitor (NIBGM) is therefore desirable to deal better with it. Microwave resonators can potentially be used for such a purpose. Following the positive results from an in vitroprevious work, a portable device based upon a microwave resonator was developed and assessed in a multicenter proof of concept. Its electrical response was analyzed when an individual’s tongue was placed onto it. The study was performed with 352 individuals during their oral glucose tolerance tests, having four measurements per individual. The findings revealed that the accuracy must be improved before the diabetes community can make real use of the device. However, the relationship between the measuring parameter and the individual’s blood glucose level is coherent with that from previous works, although with higher data dispersion. This is reflected in correlation coefficients between glycemia and the measuring magnitude consistently negative, although small, for the different data sets analyzed. Further research is proposed, focused on system improvements, individual calibration, and multitechnology approach. The study of the influence of other blood components different to glucose is also advised.
C.G. Juan, E. Bronchalo, B. Potelon, C. Quendo, E. Ávila-Navarro, and J.M. Sabater-Navarro, "Concentration measurement of microliter-volume water–glucose solutions using Q factor of microwave sensors," IEEE Transactions on Instrumentation and Measurement, vol. 68, no. 7, pp. 2621–2634, 2019.
Editor: IEEE
Impact Factor: 3.658
Quartile: Q1 (Instruments & Instrumentation; Engineering, Electrical and Electronic)
Abstract—A glucose concentration sensor for microliter-volume water–glucose solutions is presented. The proposed sensor is composed of an open-loop microstrip resonator with a dielectric liquid holder (5–25-μL volume) glued onto the gap between the line ends. The resonator is coupled to two microstrip lines forming a two-port network whose S-parameter response provide information about the dielectric properties of the liquid under study. Three versions of the sensor at resonant frequencies between 2 and 7 GHz are presented. The sensors are assessed by measuring the complex permittivity of standard liquids reported in the scientific literature. Models of the sensors are presented, which properly match the experimental results. This paper presents an experimental study of the sensors as glucose concentration retrievers. The main novelty is the use of Q factor and the maximum S21 of the resonance as sensing magnitudes. The dependence of these parameters on the glucose concentration of the solutions obeys almost linear relationships. Good sensitivities have been obtained for the proposed sensors, which are coherent with previous works by other authors.
C.G. Juan, E. Bronchalo, G. Torregrosa, E. Ávila, N. García, and J.M. Sabater-Navarro, "Dielectric characterization of water glucose solutions using a transmission/reflection line method," Biomedical Signal Processing and Control, vol. 31, no. 1, pp. 139–147, 2017.
Editor: Elsevier
DOI: 10.1016/J.BSPC.2016.07.011.
Impact Factor: 2.783
Quartile: Q2 (Engineering, Biomedical)
Abstract—Diabetes mellitus (DM) is a disease that affects millions of people worldwide. In order to be managed, it requires the individuals to measure their blood glucose level in an uncomfortable way several times every day. Thereby, a reliable non-invasive, non-painful blood glucose monitoring system is desirable. Microwave technology has been regarded previously to develop such a sensor by dielectric means, but no clear dielectric characterization of blood glucose dielectric behavior has been hitherto shown. In this paper, a novel study of the effect on the dielectric behavior of water when glucose is added is presented, as a simplified case of blood glucose dielectric behavior. Different water glucose solutions have been dielectrically characterized using a transmission/reflection line method and the effect of the changes of the glucose level in the dielectric behavior has been discussed. Conclusions concerning the development of a non-invasive blood glucose sensor are offered and their validity is discussed.
J.M. Sabater-Navarro, A. Garcia Martinez, J.M. Vicente Samper, C.G. Juan, and M. Gil, "Computer vision haemorrhage detection," British Journal of Surgery, vol. 104, no. S1, p. 24, 2017.
Editor: Wiley
DOI: 10.1002/bjs.10481.
Impact Factor: 5.433
Quartile: Q1 (Surgery)
Abstract—In this paper it is described a computer vision algorithm designed to analyse the images captured by a laparoscopic camera, classifying the pixels of each frame in blood pixels and background pixels and finally detecting a massive haemorrhage. The pixel classification is carried out by comparing the parameter B/R and G/R of the RGB space colour of each pixel with a threshold obtained using the global average of the whole frame of these parameters. The detection of and starting haemorrhage is achieved by analysing the variation of the previous parameters and the amount of pixel blood classified.
C.G. Juan, E. Bronchalo, G. Torregrosa, A. Garcia, and J.M. Sabater-Navarro, "Microwave microstrip resonator for developing a non-invasive glucose sensor," International Journal of Computer Assisted Radiology and surgery, vol. 10, no. 1, pp. 172–173, 2015.
Editor: Springer
DOI: 10.1007/s11548-015-1213-2.
Impact Factor: 1.827
Quartile: Q2 (Engineering, Biomedical)
Abstract—A noninvasive blood glucose monitoring system is presented. A microwave microstrip patch resonator antenna is used to measure the displacements of its resonant frequency while being on the individual’s tongue. These changes are due to inversely proportional changes in the relative permittivity of the tongue, which are directly related with changes in the user’s blood glucose level. Simulations are performed to assess the feasibility of the configuration of the system and the veracity of the principles adopted and the hypothesis proposed. Then, highly detailed explanations of physical implementation and evaluation with diabetic and non-diabetic volunteers and comparison with commercial invasive glucometers are shown, and final results are discussed.
C.G. Juan, "Fundamentals of microwave technology for non-invasive blood glucose monitoring and review of the most significant works developed," Revista Doctorado UMH, vol. 31, no. 1, p5, 2015.
Editor: Miguel Hernández University of Elche
Abstract—A retrospective review of the most important researches made regarding non-invasive blood glucose monitoring is presented, and bases for further investigation in this field are offered. The problem of diabetes disease on its two known types as well as its consequences and its management is discussed, and the need for this kind of glucose monitoring to avoid the painful procedures is shown. Fundamen- tals of microwave technology concerning relative permittivity measurement and tissue characterization are provided to understand the operating principles of non-invasively measuring, and theory review on this concern is presented. Variations of the relative permittivity in some zones of the body as the blood glucose level changes are studied to assess the feasibility of this kind of glucose monitoring. Literature references of electrical properties of biological tissues are studied, and the most relevant researches made regarding non-invasive blood glucose monitoring are discussed, focusing on the systems based on microwave resonators.