Guido Biffi Gentili

Dual-frequency patch antennas

Dual-frequency patch antennas may provide an alternative to large-bandwidth planar antennas, in applications in which large bandwidth is really needed for operating at two separate transmit-receive bands. When the two operating frequencies are far apart, a dual-frequency patch structure can be conceived to avoid the use of separate antennas. In this paper, a critical overview of possible solutions for dual-frequency patch antennas is presented, and future perspectives are outlined. Geometries are discussed in particular.

A coaxial antenna with miniaturized choke for minimally invasive interstitial heating

We present a new coaxial antenna for microwave interstitial coagulative therapy, working at 2450 MHz and endowed with a miniaturized sleeve choke in order to reduce back heating effects and make the system response less dependent on the antenna insertion depth into the tissue; the way the choke is implemented makes the overall transversal size minimum and allows small adjustments of the choke section length even during operation. We describe the main technical features of the antenna and show experimental results clearly proving the choke effectiveness. Numerical simulations well agree with experimental data, confirming the suitability of the proposed device for minimally invasive medical applications.

Design of dual-polarized series-fed microstrip arrays with low losses and high polarization purity

The design of a dual-polarized microstrip series-fed linear traveling-wave array is described in this paper. The array is composed of two identical subarrays formed by cascading an equal number of four-port aperture-coupled cross-patch elements and terminated on a two-port radiating matched load. By properly exciting the array, dual linear or circular polarization can be accomplished and by virtue of the symmetric arrangement of the antenna cross-polarization is annihilated. A straightforward design strategy is proposed for the synthesis of a desired current distribution along the array antenna. Some proof-of-concept linear arrays are developed and the corresponding numerical results, obtained through a full-wave approach based on the method of moments (MoM), are provided. As an independent validation, supplementary analyses by the finite integration technique (FIT) are also reported. Very close agreement is found between prescribed and synthesized array performance, which qualifies the proposed design approach as an accurate and effective tool for the synthesis of series-fed aperture-coupled patch arrays.

A versatile microwave plethysmograph for the monitoring of physiological parameters

A simple microwave technique for in vivo monitoring of human pulmonary and cardiac activity is here presented. The technique is based on detecting the changes in the modulation envelope of amplitude modulated waves passing through the human body. A simplified human chest model was developed, proving an unambiguous correlation between heart blood filling and microwave transmission through the chest. A prototype system for transmittance measurement was realized at the 868.5-MHz operating frequency, demonstrating the feasibility of a small, low cost microwave plethysmograph. In vivo measurements showed a good agreement with numerical simulations.

Electromagnetic and thermal models of a water-cooled dipole radiating in a biological tissue

An insulated, water-cooled dipole, radiating in a biological tissue, is analyzed with a theoretical electromagnetic and thermal model. The SAR (specific absorption rate) and temperature distributions are calculated taking into account the effect of the water flowing inside the applicator. The steady-state temperatures in a dissipative medium, interacting with the dipole, are evaluated for several thicknesses of the external casing, water temperatures, and blood perfusions. A correct design of the external casing thickness and a proper choice of the temperature and flow velocity of water make it possible to control the wall temperature of the applicator within physiological limits. The influence of the blood perfusion on the temperature distribution is investigated.<<ETX>>

FDTD electromagnetic and thermal analysis of interstitial hyperthermic applicators

The electromagnetic and thermal behavior of interstitial applicators was analyzed by using the finite-difference time-domain method. Two configurations were considered: a simple insulated dipole antenna radiating in a layered tissue, and an air cooled applicator radiating in a tissue-equivalent phantom. The proposed approach allows a detailed modeling of the complete structure of the applicator. Furthermore, specific absorption rate and temperature distributions can be determined considering real clinical or experimental conditions. The temperature distribution for the air cooled applicator has been compared with experimental results.<<ETX>>

Heart failure artificial intelligence-based computer aided diagnosis telecare system

In this paper we present an Artificial Intelligence-based Computer Aided Diagnosis system designed to assist the clinical decision of non-specialist staff in the analysis of Heart Failure patients. The system computes the patients pathological condition and highlights possible aggravations. The system is based on three functional parts: Diagnosis (severity assessing), Prognosis, and Follow-up management. Four Artificial Intelligence-based techniques are used and compared in diagnosis function: a Neural Network, a Support Vector Machine, a Decision Tree and a Fuzzy Expert System whose rules are produced by a Genetic Algorithm. In order to offer a complete HF analysis dashboard, state of the art algorithms are implemented to support a score-based prognosis function. The patients Follow-up is used to refine the diagnosis by adding Heart Failure type information and to detect any worsening of patients clinical status. In the Results section we compared the accuracy of the different implemented techniques.

Health technology management: A database analysis as support of technology managers in hospitals

Technology management in healthcare must continually respond and adapt itself to new improvements in medical equipment. Multidisciplinary approaches which consider the interaction of different technologies, their use and user skills, are necessary in order to improve safety and quality. An easy and sustainable methodology is vital to Clinical Engineering (CE) services in healthcare organizations in order to define criteria regarding technology acquisition and replacement. This article underlines the critical aspects of technology management in hospitals by providing appropriate indicators for benchmarking CE services exclusively referring to the maintenance database from the CE department at the Careggi Hospital in Florence, Italy.

A Coaxial Microwave Applicator for Direct Heating of Liquids Filling Chemical Reactors

A coaxial microwave applicator radiating in a liquid medium contained inside a chemical reactor is described. The applicator consists of an insulated asymmetrical dipole antenna that radiates almost isotropically. Hence, it appears well suited to directly heat the medium that fills the vessel, making it unnecessary to use a microwave oven as currently done in microwave assisted chemistry. The electromagnetic (EM) properties of the insulated dipole antenna emitting in high permittivity lossy media are first reviewed to define the applicator design criteria. A 3-D numerical EM solver is then employed to analyze the radiation of the applicator in the surrounding medium taking into account the whole structure of the reactor. Safe operations are always assured by the proper design of the applicator-vessel mechanical connection that drastically reduces unwanted stray radiation. The agreement between the theoretical analysis and the experiments performed is good, thus confirming that the coaxial applicator compares favorably with the traditional methods of activation, which use a single or multimode resonant EM cavity.

Dual-band dual polarization microstrip antenna

This paper describes the development of a multilayer dual-band dual-polarized antenna operating at L and C bands with a common aperture. Unlike earlier approaches, slot coupled patches are employed at both bands to reach cross-polarization suppression better than 30 dB. The antenna has been conceived to be used as a basic module in large series-fed arrays featuring light weight, high efficiency and beam scanning. Moreover, by properly scaling the geometry, the antenna can operate at any else pairs of frequencies with a ratio between 3.5-4.5.