Piero Tognolatti

Time-dependent microwave radiometry for the measurement of temperature in medical applications

Microwave radiometry has been considered for the noninvasive monitoring of internal temperature in biological bodies when the temperature is varied under the control of external sources and contacting fluid. The body temperature is modeled as a discrete-time controlled statistical process, whose estimate is cyclically updated exploiting radiometric measurements. The Kalman filter has been used, which is able, with the proper choice of parameters, to balance the temperature retrieval between a priori information and measurements. Prospective applications to medicine have been investigated for temperature monitoring within a neonatal head during a hypothermia treatment.

Lunar Microwave Brightness Temperature: Model Interpretation and Inversion of Spaceborne Multifrequency Observations by a Neural Network Approach

Understanding the lunar physical properties has been attracting the interest of scientists for many years. This paper is devoted to a numerical study on the capability of retrieving the thickness of the first layer of regolith as well as the temperature profile behavior from satellite-based multifrequency radiometers at frequencies ranging from 1 to 24 GHz. To this purpose, a forward thermal-electromagnetic numerical model, able to simulate the response of the lunar material in terms of upward brightness temperature (TB), has been used. The input parameters of the forward model have been set after a detailed investigation of the scientific literature and available measurements. Different choices of input parameters are possible, and their selection is carefully discussed. By exploiting a Monte Carlo approach to generate a synthetic data set of forward-model simulations, a physically based inversion methodology has been developed using a neural network technique. The latter has been designed to perform, from multifrequency TBs, the temperature estimation at the lunar surface, the discrimination of the subsurface material type, and the estimate of the near-surface regolith thickness. Results indicate that, within the simplified scenarios obtained by interposing strata of rock, ice, and regolith, the probability of detection of the presence of discontinuities beneath the lunar crust is on the order of 84%. The estimation uncertainty of the near-surface regolith thickness estimation ranges from 11 to 81 cm, whereas for the surface temperature, its estimation uncertainty ranges from about 1.5 K to 3 K, conditioned to the choice of radiometric frequencies and noise levels.

Finite element modelling of a thin‐film bulk acoustic resonator (FBAR)

Purpose – The paper aims to propose a three‐dimensional (3D) finite element analysis to evaluate the electrical performances of a FBAR (thin‐film bulk acoustic resonator) resonator.Design/methodology/approach – The piezoelectric theory that uses an equivalent circuit is able to evaluate the thickness‐extensional vibration modes in simple 1D configuration but it is not adequate to predict spurious modes with lateral wave vector. Therefore, a fully 3D finite element analysis has been carried out to evaluate the characteristics of a real FBAR prototype that has been fabricated in a research center.Findings – The measured characteristics of the FBAR prototype are compared with simulations obtained by the 3D finite element analysis. The agreement between experimental and numerical results confirms the accuracy of the proposed technique.Originality/value – The paper proposes a 3‐D numerical approach to design and analyze the electrical characteristics of a real FBAR which has been fabricated following the guide...

Remote sensing of the Moon sub-surface from a spaceborne microwawe radiometer aboard the European Student Moon Orbiter (ESMO)

Given the rising and renewed interest towards the study of Moon the European space Agency (ESA) approved, in March 2006, the phase-A for the feasibility study of the European Student Moon Orbiter (ESMO) mission proposed by the Student Space Exploration & Technology Initiative (SSETI). The objective of the ESMO mission is to acquire images of the moon in stable orbit, transmit them to the Earth and then to actively involve European students in a real space program experience. In order to accomplish the ESMO mission objectives, a Micro Wave Radiometric Sounder (MiWaRS) has been selected as a possible choice for flying on board of the ESMO satellite. This work summarizes the preliminary results obtained during the phase-A for the MiWaRS with special attention to the description of the radiometric system design and its scientific objectives.

New-born-infant brain temperature measurement by microwave radiometry

Hypothermia of the new-born-infant brain has been proposed as a neuroprotective therapy after hypoxia-ischaemia. At a preliminary stage of the new therapy the knowledge of the achievable brain temperature is desirable as well as its variation with time during treatment. There is the need, therefore, for non-invasive temperature measurement during hypothermia treatments. Multifrequency microwave radiometry has been considered for the measurement of the baby-head temperature during therapeutic cooling. Thermal and electromagnetic models for the baby head are required. A thermal model of the cooling has been arranged from the Pennes equation and data found in literature and the model used to generate the synthetic data to be exploited in temperature reconstruction. The inverse problem has been formulated in two different ways: (a) a retrieval based on a thermal model fitting by matrix pencil and least square minimisation; (b) a finite state-space approach with Kalman filtering of data. A numerical analysis has been performed showing that the radiometric measurements can partially compensate for errors in the model provided the temperature profile belongs to the class of functions specified by the model.

Hyperthermia phased arrays pre-treatment evaluation.

Abstract Purpose: In the hyperthermia treatment of deep-seated tumours by a phased array of radiofrequency (RF) antennas, heatability will be investigated in terms of power-to-tumour and other figures-of-merit of hyperthermia treatments to be optimised. The assumption is that each source is individually constrained to not exceed a maximal nominal power. The nominal power may differ from a source to another as a physical limit or an operative modality. Method: Under such constraint, new procedures for the maximisation of (i) power-to-tumour, (ii) heating efficiency and, in general, (iii) power ratios as tumour-heating selectivity are proposed. (iv) The problem whether a tumour is equally heatable after turning off some antennas is addressed as array thinning. Case study: An array of eight dipoles arranged on two lines around a head/neck is introduced to perform a numerical analysis. The achievable power-to-tumour according to the new optimizations and other performance indices adopted from the literature is tested against values of power that can be found to be sufficient for heating tumours to clinical temperatures. New solutions to data rendering in hyperthermia heating are proposed.

SDR-based system for satellite ranging measurements

In this article we describe how we used the pseudonoise (PN) techniques to perform ranging measurements on a geostationary satellite with a low-cost system consisting of a software algorithm, developed by means of an open-source programming environment, and supported by inexpensive programmable hardware. The system is based on software defined radio (SDR), a technique that is becoming more widespread whose use was approved by the United States Federal Communications Commission (FCC) in 2004 [12]. SDR allows the use of radio transceivers with minimal hardware, by replacing some hardware devices with rewritable software and editable algorithms. The biggest advantage of the SDR is the opportunity to reconfigure and modify the transceiver system characteristics according to the peculiarities of different standards. Examples of use of SDR are Universal Mobile Telecommunications System (UMTS), Global System for Mobile (GSM), Digital Video Broadcast (DVB)-S/DVB-S2/DVB-T, Wimax, etc., where a common hardware is compatible with all of the above Telecommunications Standards.

Figures of merit and their bounds in radiofrequency heating by phased arrays

Abstract Purpose: The problem of effective power delivery to a semi-deep target by a phased array has been addressed for application to hyperthermia treatment of some tumours in the thorax. Methods: Three efficiencies have been introduced, which estimate system ability in power transfer from generators to body, from body to tumour, and from generators to tumour. They are formulated in terms of a dissipation matrix and an interference matrix. Bounds to achievable efficiencies are obtained. Further figures of merit have also been introduced. The necessary mathematics has been developed. Results: A numerical analysis has been carried out for a partially interdigitated planar array of resonant dipoles. Results show how the new parameters can be exploited for optimal selection of the array’s degrees of freedom. Conclusion: The figures of merit and their bounds allow comparisons between RF heating devices and provide guidelines to phased array design.

Prototype Design of a Thin-Film Bulk Acoustic-Wave Resonator by the Finite Element Method

A thin film bulk acoustic wave resonator (FBAR) used in the RF frequency region of a few gigahertz is considered and its impedance is evaluated by using a harmonic analysis with the three-dimensional finite element method. In particular, the spurious characteristics caused by variations in the electrode area, as well as all the resonant modes and the mode shapes are analyzed. A design procedure is presented by using a prediction software tool. An experimental prototype is built and the measured results are compared to the numerical ones.

A Microwave Radiometer for Diagnosis of Breast Malignancy

A breast tumor is visible by a passive microwave radiometer if it changes the radiometer output of a healthy breast to an extent that overcomes the radiometric resolution. The characteristics of a new dual-band near-field radiometer are exposed. The deformation by an antenna pressed against the breast lowers the distance of a subsurface tumor from the contacted surface improving the tumor radiometric visibility. We show this result by modeling breast deformation, temperature and corresponding radiometer output both in the presence of a tumor and in its absence. For a 25% net breast deformation, a tumor of 10 mm diameter is visible by a 0.1degC radiometer and a 3 cm aperture antenna when it is 4 cm deep in the undeformed breast.