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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. System validation with standard liquids
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11. COST BM 1309 – Brussels 16 April 2014
System validation with standard liquids
Methanol
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12. 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 , (2002).
COST BM 1309 – Brussels 16 April 2014

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Preliminary results
0.1 mol/l NaCl solution
Temperature
Temperature
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14. COST BM 1309 – Brussels 16 April 2014
Preliminary results
Normal liver tissue at 37ºC
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15. COST BM 1309 – Brussels 16 April 2014
Preliminary results
Normal kidney tissue at 37ºC
COST BM 1309 – Brussels 16 April 2014

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

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

18. 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

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

20. Thank you