Electromagnetics Research Group Department of Physics University of Malta Charles V Sammut

Electromagnetics Research Group Charles V Sammut (Group Leader & Head, Dept of Physics) Louis Zammit Mangion (Dept of Physics) Pierre Schembri Wismayer (Head, Dept of Anatomy) Postgraduate research students: Lourdes Farrugia Eman O Farhat Stephen Vella Julian Bonello Ruth Grech Marguerat Giuseppe Gauci COST BM 1309 – Brussels 16 April 2014

Electromagnetics Laboratory Main T&M equipment VNA R&S ZVA-50 10MHz-50GHz (with extension to 90 GHz) Dielctric measurement kit (85070E Agilent Dielectric Probe kit) plus additional probes and WGs to cover 10MHz-90GHz Speag Time domain E and H measurement system with miniature optic fibre coupled sensors, 10MHz-6GHz Spectrum analyser R&S 50Hz-50GHz Hand-held instruments: Anritsu Spectrum analyser (9 kHz-18 GHz) Narda SRM-3006 Narda NBM-550 Narda EFA 300 Additional before end 2014: Interference & direction analyser VNA 85MHz-14GHz Frequency selective personal radiation monitor 80MHz-6GHz Selective frequency broadband ELF analyser 5Hz-100kHz Frequency counter (400 MHz – 40 GHz) Power meter, power sensors (10MHz-20GHz) EMC/EMI capabilities to pre-compliance standard COST BM 1309 – Brussels 16 April 2014

Electromagnetics Laboratory Other facilities Anechoic chamber 700MHz-18GHz (soon) A range of antennas covering RF & MW frequencies to 90GHz Sweep oscillators, function/signal generators (<50Hz – 90GHz) Power amplifiers 100kHz-3GHz, 100W Multichannel temperature sensor Constant temperature bath: 0 – 99 ± 0.02ºC Software: ANSYS, HFSS, FEKO, Maxwell, CST, SEMCAD X (including full suite of computational phantoms), Narda EFC-400 Supercomputing cluster (7 T Flop) COST BM 1309 – Brussels 16 April 2014

COST BM 1309 – Brussels 16 April 2014 Ongoing Research Complex permittivity measurements Liquids as a function of frequency and temperature Biological tissues: Rat and canine healthy & tumour Bovine and porcine liver and muscle Cortical bone Design and development of wideband fractal antenna arrays for radio astronomy (in collaboration with the Astrophysics Group) – part of the SKA project Measurement and simulation of RF & MW emissions from mobile phone base stations, broadcast stations, radar Measurement and simulation of occupational exposure to ELF magnetic fields Measurement and modelling of near fields of mobile phone base station antennas Measurement and modelling of occupational exposure to MRI static and gradient magnetic fields COST BM 1309 – Brussels 16 April 2014

Dielectric properties of biological tissues for medical applications RF & MW diagnostics: Tomography & radiometry (TD1301) MW imaging (breast tumours) (TD1301) Terahertz imaging (skin lesions) (BM1205 & MP1204) RF & MW therapeutics: (BM1309) RF fields are being used in a range of new medical treatments (e.g.: Conductive Keratoplasty to correct hyperopia; RF ablation – liver tumours, enlarged prostate, Wolff-Parkinson-White syndrome, sleep apnea, snoring, physiotherapy,…) Tissue ablation by MW hyperthermia (e.g.: MW endometrial ablation; liver, kidney and lung tumours) Potential for bone tumours COST BM 1309 – Brussels 16 April 2014

Complex permittivity of biological tissues Accurate knowledge of the permittivity of body tissues is crucial for both diagnostic and therapeutic procedures Diagnosis relies on detecting a difference in permittivity between healthy and diseased tissue Design of RF and MW applicators for tissue ablation requires extensive simulation, which requires detailed knowledge of permittivity at the treatment frequency and over a range of temperatures σi is the static ionic conductivity; The dielectric spectrum of a tissue is characterized by three main relaxation regions ; and at low, medium and high frequencies, and other minor dispersions such as the often reported dispersion. In its simplest form, each of these relaxation regions is the manifestation of a polarization mechanism characterized by a single time constant τ. COST BM 1309 – Brussels 16 April 2014

Measurement of permittivity Motivation - to address gaps in knowledge: Most published values are in the frequency range 100 MHz- 20 GHz Scarce experimental data at higher and lower frequencies; current models require experimental validation outside this frequeny range and at higher temperatures Permittivity values used for dosimetric studies derived from the 1996 database - mostly human, bovine and ovine at 37ºC Values at higher temperatures are required for hyperthermia modelling Almost all accepted values were measured using ex-vivo samples In-vivo permittivity values are higher than ex-vivo for the same tissue type at RF and lower frequencies Dosimetric studies involve the use of human body or organ phantoms. Calculation of SAR in body tissues requires computational phantoms which are generated from magnetic resonance images, some of which have sub-mm resolution. However, the values assigned to the individual pixels are accepted values available in the literature. COST BM 1309 – Brussels 16 April 2014

Measurement of permittivity The permittivity of biological tissues can be modelled Cole-Cole equation We use open-ended coaxial probes and obtain reflection measurements, from which the parameters of the Cole-Cole equation are obtained We also use an X-band rectangular waveguide kit to carry out transmission and reflected measurements on solid samples (bone) σi is the static ionic conductivity; The dielectric spectrum of biological tissues is characterized by three main relaxation regions at low, medium and high frequencies, and other minor dispersions. These relaxation regions correspond to different polarization mechanisms characterized by constants τ. Cole-Cole equation has n=4 COST BM 1309 – Brussels 16 April 2014

System validation with standard liquids COST BM 1309 – Brussels 16 April 2014

COST BM 1309 – Brussels 16 April 2014 System validation with standard liquids Methanol COST BM 1309 – Brussels 16 April 2014

COST BM 1309 – Brussels 16 April 2014 System validation with standard liquids Formamide Barthel, J.; Buchner, J.; Wurm,B. The dynamics of liquid formamide, N-methylformamide, N,N-dimethylformamide, and N,N-dimethylacetamide. A dielectric relaxation study, Journal of Molecular Liquids, vols 98–99, pp. 51-69, (2002). COST BM 1309 – Brussels 16 April 2014

COST BM 1309 – Brussels 16 April 2014 Preliminary results 0.1 mol/l NaCl solution Temperature Temperature COST BM 1309 – Brussels 16 April 2014

COST BM 1309 – Brussels 16 April 2014 Preliminary results Normal liver tissue at 37ºC COST BM 1309 – Brussels 16 April 2014

COST BM 1309 – Brussels 16 April 2014 Preliminary results Normal kidney tissue at 37ºC COST BM 1309 – Brussels 16 April 2014

COST BM 1309 – Brussels 16 April 2014 Preliminary results Normal muscle tissue at 37ºC COST BM 1309 – Brussels 16 April 2014

COST BM 1309 – Brussels 16 April 2014 Preliminary results Canine and rat tumours COST BM 1309 – Brussels 16 April 2014

COST BM 1309 – Brussels 16 April 2014 Preliminary results Bone (cortical) The lower meausred values are most likely due to loss of water content in the bone sample during preparation. Gabriel et al used an open-ended coaxial probe for their measuerment on freshly excised bovine bone. We used a transmission (through) measurement with our WG structure. The problem that needs to be addressed is sample preparation – this is currently too invasive COST BM 1309 – Brussels 16 April 2014

COST BM 1309 – Brussels 16 April 2014 Preliminary results Bone (cortical) COST BM 1309 – Brussels 16 April 2014

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