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Microwave Medical Imaging
Raquel Conceição ([email protected])
Institute of Biophysics and Biomedical Engineering (IBEB),
Faculty of Sciences, University of Lisbon, Portugal
Fundação para a Ciência e a Tecnologia
7th FP, Marie Curie Intra-European Fellowship, REA grant 301269
EPSRC: EP/J007293/1
Medical Microwave Imaging Radar
Advantages:- non-invasive- non-ionising (MW)- low-power- potentially low-cost- comfortable – no compression, quick
- differences in dielectric properties between the constituent tissues of the healthy and cancer masses at MW frequencies in shallow parts of the body
Medical Microwave Imaging Radar
First studies date back from late 1990s:- Hagness et al (1998), Two Dimensional FDTD Analysis of aPulsed Microwave Confocal System for Breast CancerDetection: Fixed-Focus and Antenna-Array Sensors- Fear et al (1999), Microwave System for Breast TumorDetection
Applications include:- Breast cancer detection- Stroke detection- Bladder volume control- Lung edema- Bone analysis…
-> How does Medical Microwave ImagingRadar work?
(examples given for breast MWI)
• Antennas at different locations surrounding the breast
Artefact Removal algorithms (remove the skin response):
Differential Rotation
Average Subtraction
Adaptive Filtering
Subtract the rotated measurements from original stored waveforms – Klemm et al
Subtract the average of all the stored waveforms from each of the original backscattered signals – Li et al
The artefact in each channel is estimated as a filtered combination of the signal in all other channels – Bond et al
Artefact Removal algorithms (remove the skin response):
Other algorithms include:
Wiener Filter Root Least Squares Filter
Entropy-based Time Windowing Hybrid Artefact Removal
Frequency Domain Skin-Artefact Removal
Neighbourhood based Skin Subtraction
Independent Component Analysis Artefact Removal Algorithm
Beamformer algorithms – Data independent beamformers:
Delay and Sum Time shift and sum the backscattered signals Hagness et al.
Beamformer algorithms – Data independent beamformers:
Delay Multiply and Sum
Delay and Sum
Channel Ranked Delay and Sum
Additional pairing multiplication procedure after time shifting
Time shift and sum the backscattered signals
Gives extra weighting to signals with shorter propagation distances
Hagness et al.
Lim et al.
O’Halloran et al.
Beamformer algorithms – Data independent beamformers:
Microwave Space-Time (MIST) Beamformer
Coherence Weighted Beamformers
Compensation for frequencydependentpropagation effects to better spatially focus the backscattered signals – Bond et al
Extension of DAS beamformer by introducing an additional weighting factor called the “Quality Factor” (QF) – Klemm et al
Beamformer algorithms – Adaptive beamforming:
Minimum Variance Capon beamformer – Haykin et al
Multistatic Adaptive Microwave Imaging – Xie et al
Transmitter-Grouping Robust Capon beamformer – Byrne et al
Wideband Time-Domain Adaptive Beamforming – Byrne et al
Beamformer algorithms – Path Dielectric Estimation Techniques
Multiple Signal Classification Time-Of-Flight – Sarafianou et al
Transmission Coefficient Method – Bourqui et al
Optimisation Based Propagation Technique – Guo et al
• Creation of an energy profile of the breast
• High-energy regions may indicate the presence of tumours
-> How to simulate radar MicrowaveImaging?
(examples given for breast MWI)
Electromagnetic propagationin the breast is simulatedwith Finite-Difference Time-Domain (FDTD) modelling.
Breast models have a typical resolution of 0.5 mm.
Different tissues are present, such as: normal (adipose andfibroglandular) tissue, skin and tumour tissue.
Tissues are mapped into a 3D FDTD grid – a Debye formulation isused to attribute the appropriate dielectric properties to each tissue:
ε∞ permittivity of the free spaceΔε relative permittivityτ relaxation time constantσs conductivity
University of Bristol
University of Bristol/ Micrima
https://www.youtube.com/watch?v=i1OoRmPntVs
-> Example of radar Microwave Imagingprototypes
University of Bristol – array of
antennas
Multistatic-based prototype
Monostatic-based prototype
University of Calgary –single scanning antenna
Imaging: Confocal Microwave ImagingConsultant’s report Microwave Image
University of Calgary
Imaging: Confocal Microwave ImagingConsultant’s report Microwave Image
University of Calgary
To sum up:
• Presentation of monostatic and multistatic radar microwave imaging systems
• Break-down of radar Microwave Imaging: i) UWB pulse, ii) skin-artefact removal, iii) beamforming
• Simulation and patient results
• Small scale studies indicate significant dielectric contrast between healthy and cancer tissue
This work has been developed in the framework of COST Action TD1301, MiMed. The goal of this COST Action is to accelerate the technological, clinical and commercialisationprogress in the area of medical Microwave Imaging andtherapeutical techniques.
Action website: http://cost-action-td1301.org
We are a network of over 200 researchers from:25 COST countries (AT, BE, BG, CH, CY, CZ, DE, DK, EL, ES, FR, HR, IE, IL, IT,
MT, NL, NO, PT, RO, RS, SE, SO, TR, UK), 1 NNC (RU) and 3 IPC countries (CA, CN, US)
This work has been developed in the framework of COST Action TD1301, MiMed. The goal of this COST Action is to accelerate the technological, clinical and commercialisationprogress in the area of medical Microwave Imaging andtherapeutical techniques.
Questions?
Thank you!