Lorenzo Leija

Dr. Lorenzo Leija

orcid

Research Focus & Metrics

Academic Career Length

24Years (2003-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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20 July 2022 in Electronics
Verified
Journal Article
Open access
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CTCinthya Lourdes Toledo-Peral
Cinthya Lourdes Toledo-Peral
GVGabriel Vega-Martínez
Gabriel Vega-Martínez
JGJorge Airy Mercado Gutierrez
Jorge Airy Mercado Gutierrez
GRGerardo Rodriguez-Reyes
Gerardo Rodriguez-Reyes
AVArturo Vera-Hernández
Arturo Vera-Hernández
JGJosefina Gutiérrez-Martínez
Josefina Gutiérrez-Martínez
Virtual reality (VR) and augmented reality (AR) are engaging interfaces that can be of benefit for rehabilitation therapy. However, they are still not widely used, and the use of surface electromyography (sEMG) signals is not established for them. Our goal is to explore whether there is a standardized protocol towards therapeutic applications since there are not many methodological reviews that focus on sEMG control/feedback. A systematic literature review using the PRISMA (preferred reporting items for systematic reviews and meta-analyses) methodology is conducted. A Boolean search in databases was performed applying inclusion/exclusion criteria; articles older than 5 years and repeated were excluded. A total of 393 articles were selected for screening, of which 66.15% were excluded, 131 records were eligible, 69.46% use neither VR/AR interfaces nor sEMG control; 40 articles remained. Categories are, application: neurological motor rehabilitation (70%), prosthesis training (30%); processing algorithm: artificial intelligence (40%), direct control (20%); hardware: Myo Armband (22.5%), Delsys (10%), proprietary (17.5%); VR/AR interface: training scene model (25%), videogame (47.5%), first-person (20%). Finally, applications are focused on motor neurorehabilitation after stroke/amputation; however, there is no consensus regarding signal processing or classification criteria. Future work should deal with proposing guidelines to standardize these technologies for their adoption in clinical practice.

27 September 2020 in Molecules
Verified
Journal Article
Open access
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MMMauricio A. Medina
Mauricio A. Medina
Goldie H. OzaGoldie H. Oza
Goldie H. Oza
AÁA. Ángeles-Pascual
A. Ángeles-Pascual
MMMarlene Gonzalez Montiel
Marlene Gonzalez Montiel
RARené Antaño-López
René Antaño-López
JTJosé Tapia-Ramírez
José Tapia-Ramírez
Magnetic nanoparticles such as cobalt ferrite are investigated under clinical hyperthermia conditions for the treatment of cancer. Cobalt ferrite nanoparticles (CFNPs) synthesized by the thermal decomposition method, using nonionic surfactant Triton-X100, possess hydrophilic polyethylene oxide chains acting as reducing agents for the cobalt and iron precursors. The monodispersed nanoparticles were of 10 nm size, as confirmed by high-resolution transmission electron microscopy (HR-TEM). The X-ray diffraction patterns of CFNPs prove the existence of cubic spinel cobalt ferrites. Cs-corrected scanning transmission electron microscopy–high-angle annular dark-field imaging (STEM–HAADF) of CFNPs confirmed their multi-twinned crystallinity due to the presence of atomic columns and defects in the nanostructure. Magnetic measurements proved that the CFNPs possess reduced remnant magnetization (MR/MS) (0.86), which justifies cubic anisotropy in the system. Microwave-based hyperthermia studies performed at 2.45 GHz under clinical conditions in physiological saline increased the temperature of the CFNP samples due to the transformation of radiation energy to heat. The specific absorption rate of CFNPs in physiological saline was 68.28 W/g. Furthermore, when triple-negative breast cancer cells (TNBC) in the presence of increasing CFNP concentration (5 mg/mL to 40 mg/mL) were exposed to microwaves, the cell cytotoxicity was enhanced compared to CFNPs alone.

24 March 2020 in Electronics
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Journal Article
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RORocío Ortega
Rocío Ortega
Citlalli Jessica Trujillo-RomeroCitlalli Jessica Trujillo-Romero
Citlalli Jessica Trujillo-Romero
MCMario Francisco Jesús Cepeda-Rubio
Mario Francisco Jesús Cepeda-Rubio
LLLorenzo Leija
Lorenzo Leija
AVArturo Vera-Hernández
Arturo Vera-Hernández
It is worldwide known that the most common type of cancer among women is breast cancer. Traditional procedures involve surgery, chemotherapy and radiation therapy; however, these treatments are invasive and have serious side effects. For this reason, minimally invasive thermal treatments like microwave ablation are being considered. In this study, thermal behavior of three types of slot-coaxial antennas for breast cancer microwave ablation is presented. By using finite element method (FEM), all antennas were modeled to estimate the heat transfer in breast tumor tissue surrounded by healthy breast tissue. Experimentation was carried out by using the antennas inserted inside sphere-shaped-tumor phantoms with two different diameters, 1.0 and 1.5 cm. A microwave radiation system was used to apply microwave energy to each designed antenna, which were located into the phantom. A non-interfering thermometry system was used to measure the temperature increase during the experimentation. Temperature increases, recorded by the thermal sensors placed inside the tumor phantom surrounded by healthy breast phantom, were used to validate the FEM models. The results conclude that, in all the cases, after 240 s, the three types of coaxial slot antenna reached the temperature needed produce hyperthermia of the tumor volume considered in this paper.

1 September 2010
Verified
Conference Paper
Closed access
RORocío Ortega
Rocío Ortega
LLLorenzo Leija
Lorenzo Leija
AVArturo Vera-Hernández
Arturo Vera-Hernández
MCM. F. J. Cepeda
M. F. J. Cepeda
Most phantom models do not include distinct definitions of tumor and normal tissue. This article proposes a novel solid breast - tumor phantom for microwave hyperthermia in breast cancer treatment. According to tissue dielectric properties reported, we performed phantom. A Network Analyzer and Dielectric Probe Kit measured dielectric constant and electrical conductivity for both breast normal tissue and tumor phantom. Measurements were through at frequency range from 2 to 3 GHz due microwave operation frequency is usually 2.45 GHz. At 2.45 GHz breast phantom had an electrical conductivity of 0.1304±0.0680 S/m and a dielectric constant of 4.4401 ± 1.2514. At the same frequency, tumor phantom had an electrical conductivity of 2.7015 ± 0.0783 S/m and a dielectric constant of 55.2566 ± 1.1899. The presented results highly correlate with the expected values. Therefore this phantom can be used for microwave hyperthermia in breast cancer treatment and antenna performance analysis and optimization.

24 March 2021 in Electronics
Verified
Journal Article
Open access
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Citlalli Jessica Trujillo-RomeroCitlalli Jessica Trujillo-Romero
Citlalli Jessica Trujillo-Romero
LLLorenzo Leija
Lorenzo Leija
AVArturo Vera-Hernández
Arturo Vera-Hernández
GRGenaro Rico-Martínez
Genaro Rico-Martínez
JGJosefina Gutiérrez-Martínez
Josefina Gutiérrez-Martínez
According to statistics of the American Cancer Society, the number of young people diagnosed with bone tumors is growing. Surgery and radiotherapy are the common treatments, however they have several side effects which affect the patient’s life. Therefore, a cheaper and less side-effect therapy called thermal ablation has been explored. The goal of this paper is to measure the therapeutic temperatures and the viability of a double slot antenna designed to treat bone tissue by microwave ablation. The antenna (at an operating frequency of 2.45 GHz) was designed, modeled, constructed, and experimentally evaluated. The finite element method was used to predict the antenna performance by means of 2D axisymmetric models. The modeling parameters were used to build the antenna. The experimental evaluation shows that the antenna behavior is repeatable and the standing wave ratio (SWR) was around 1.5–1.8. Temperatures around 60–100 °C were achieved over the bone tissue. The antenna insertion modifies the antenna performance. An insertion lower than 3.5 cm is not recommended because the convection effects modified the tissue temperature. The thermal patterns showed a heat focus near to the slots, which makes it possible for use in the treatment of small tumors.

17 September 2021 in Electronics
Verified
Journal Article
Open access
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Texar Javier Ramírez GuzmánTexar Javier Ramírez Guzmán
Texar Javier Ramírez Guzmán
Citlalli Jessica Trujillo-RomeroCitlalli Jessica Trujillo-Romero
Citlalli Jessica Trujillo-Romero
RMRaquel Martinez-Valdez
Raquel Martinez-Valdez
LLLorenzo Leija
Lorenzo Leija
AVArturo Vera-Hernández
Arturo Vera-Hernández
JGJosefina Gutiérrez-Martínez
Josefina Gutiérrez-Martínez
Bone cancer is rare in adults, the most affected persons by this disease are young people and children. The common treatments for bone cancer are surgery, chemotherapy, and targeted therapies; however, all of them have side-effects that decrease the patient’s quality of life. Thermotherapy is one of the most promising treatments for bone cancer; its main goal is to increase the tumor temperature to kill cancerous cells. Although some micro-coaxial antennas have been used to treat bone tumors, most of them are designed to treat soft tissue. Therefore, the purpose of this work is to analyze the thermal behavior of four micro-coaxial antennas specifically designed to generate thermal ablation in bone tissue to treat bone tumors, at 2.45 GHz. The proposed antennas were the metal-tip monopole (MTM), the choked metal-tip monopole (CMTM), the double slot (DS) and the choked double slot (CDS). The design and optimization of the antennas by using the Finite Element Method (FEM) allow to predict the optimal antenna dimensions and their performance when they are in contact with the affected biological tissues (bone, muscle, and fat). In the FEM model, a maximum power transmission was selected as the main parameter to choose the optimum antenna design, i.e., a Standing Wave Ratio (SWR) value around 1.2–1.5. The four optimized antennas were constructed and experimentally evaluated. The evaluation was carried out in multilayer phantoms (fat, muscle, cortical, and cancellous bone) and ex vivo porcine tissue at different insertion depths of the antennas. To fully evaluate the antennas performance, the standing wave ratio (SWR), power loss, temperature profiles, and thermal distributions were analyzed. In the experimentation, the four antennas were able to reach ablation temperatures (>60 °C) and the highest reached SWR was 1.7; the MTM (power loss around 16%) and the CDS (power loss around 6.4%) antennas presented the lowest SWR values depending on the antenna insertion depth, either in multilayer tissue phantom or in ex vivo tissue. These proposed antennas allow to obtain ablation temperatures with an input power of 5 W after 5 min of treatment; these values are lower than the ones reported in the literature.