WO2018083492A1 - Appareil et procédé de mesure de densité mammaire - Google Patents

Appareil et procédé de mesure de densité mammaire Download PDF

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Publication number
WO2018083492A1
WO2018083492A1 PCT/GB2017/053324 GB2017053324W WO2018083492A1 WO 2018083492 A1 WO2018083492 A1 WO 2018083492A1 GB 2017053324 W GB2017053324 W GB 2017053324W WO 2018083492 A1 WO2018083492 A1 WO 2018083492A1
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WO
WIPO (PCT)
Prior art keywords
breast
density
scattering parameters
microwave
permittivity
Prior art date
Application number
PCT/GB2017/053324
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English (en)
Inventor
Chris Frank BORE
Original Assignee
Micrima Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Micrima Limited filed Critical Micrima Limited
Publication of WO2018083492A1 publication Critical patent/WO2018083492A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/0507—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves  using microwaves or terahertz waves
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/43—Detecting, measuring or recording for evaluating the reproductive systems
    • A61B5/4306—Detecting, measuring or recording for evaluating the reproductive systems for evaluating the female reproductive systems, e.g. gynaecological evaluations
    • A61B5/4312—Breast evaluation or disorder diagnosis
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7271—Specific aspects of physiological measurement analysis
    • A61B5/7275—Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
    • G—PHYSICS
    • G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
    • G16H—HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA
    • G16H50/00—ICT specially adapted for medical diagnosis, medical simulation or medical data mining; ICT specially adapted for detecting, monitoring or modelling epidemics or pandemics
    • G16H50/30—ICT specially adapted for medical diagnosis, medical simulation or medical data mining; ICT specially adapted for detecting, monitoring or modelling epidemics or pandemics for calculating health indices; for individual health risk assessment

Definitions

  • the invention relates to a breast density meter and method for measuring the density of breast tissue in vivo.
  • breast cancer is the second most common type of cancer and the fifth most common cause of cancer death.
  • diligent individuals subject themselves to regular mammograms for the purpose of detecting an existence of breast cancer.
  • An ancillary benefit of having a mammogram conducted is the ability of the radiologist to determine a radiographical density of the participant's breast tissue due to the fact that there is a prognostic relationship between breast density and cancer risk.
  • the radiographical density of a breast illustrated within a mammogram may vary due to differences in the amount of fat, connective tissues, and epithelial tissues that are present.
  • fibroglandular and connective tissues i.e. glands, ducts, and fibers
  • fibroglandular and connective tissues may appear to be radiographically dense/light on radiographic films.
  • fat has a relatively low x-ray attenuation and therefore appears to be the least radiographically dense/dark, when compared to the remaining breast tissue. Because of the distinct differences in x-ray attenuation between fat and fibroglandular tissue, segmentation of fibroglandular tissue from the rest of the breast is possible.
  • a known breast density estimation standard may be based upon a four-category Breast Imaging Reporting and Data Systems (BI-RADS) lexicon. Upon visually assessing a mammogram, a radiologist may classify the radiographical image of the breast into one of four BI-RADS compositional categories defined as:
  • the Applicants have recognised that there is a correlation between the density of breast tissue and the extent of microwave scattering there through, and that scattering parameters obtained for a breast (by appropriate measurements) can then be used to determine (an indication of) the density of the breast.
  • a breast density meter for measuring the density of breast tissue comprising: at least one microwave antenna configured to transmit microwave signals over a range of frequencies so as to illuminate a breast of a patient and to receive the microwave signals following scattering within the breast; and a processor configured to obtain a set of scattering parameters for the microwave signals over the range of frequencies and to determine a density value or a cancer risk score based on a density value for the breast from a predetermined correlation between density and the scattering parameters which is in turn derived from a predetermined correlation between density and a change in permittivity with frequency, the change in permittivity being calculatable from the scattering parameters.
  • the set of scattering parameters obtained by the processor is compared to reference data that corresponds to and/or is representative of a predetermined correlation between density and the scattering parameters.
  • the reference data may, for example, be in the form of a look-up table that is stored in memory and includes plural entries corresponding respectively to the scattering parameters and their corresponding density values.
  • the predetermined correlation between density and the scattering parameters may be a predetermined correlation between density and a change in scattering parameters with frequency.
  • each entry in the look-up table may correspond to a (e.g. identified or determined) change in scattering parameters with frequency and its corresponding density value.
  • the at least one microwave antenna may comprise a plurality of antennas that are spaced from one another to form an array, the plurality of antennas defining a transmitting antenna and receiving antennas.
  • the microwave antenna array may be formed on a substrate which is contoured or contourable to conform to the body part.
  • the substrate may be hemispherical.
  • the processor may be further configured to generate an image of the internal structure of the breast based on the measured scattering parameters.
  • the processor may generate a plurality of density values for different volumes within the breast.
  • the processor may generate an average of the plurality of density values to give a density value for the breast as a whole.
  • a method for measuring the density of breast tissue comprising: illuminating a breast of a patient with microwave signals emitted by at least one microwave antenna; receiving the microwave signals following scattering within the breast at said at least one microwave antenna; measuring scattering parameters for the microwave signals over a range of frequencies; and determining a density value or a cancer risk score based on a density value for the breast from a predetermined correlation between density and the scattering parameters which is in turn derived from a predetermined correlation between density and a change in permittivity with frequency, the change in permittivity being calculatable from the scattering parameters.
  • the measured set of scattering parameters is compared to reference data that corresponds to and/or is representative of a predetermined correlation between density and scattering parameters.
  • the reference data may, for example, be in the form of a look-up table that includes plural entries corresponding respectively to the scattering parameters and their corresponding density values.
  • the predetermined correlation between density and the scattering parameters may be a predetermined correlation between density and a change in scattering parameters with frequency.
  • each entry in the look-up table may correspond to a (e.g. identified or determined) change in scattering parameters with frequency and its corresponding density value.
  • the at least one microwave antenna comprises a plurality of antennas that are spaced from one another to form an array, the plurality of antennas defining a transmitting antenna and receiving antennas.
  • the method may further comprise generating an image of the internal structure of the breast based on the measured scattering parameters.
  • a plurality of density values may be generated for different volumes within the breast.
  • the method may further comprise determining an average of the plurality of density values to give a density value for the breast as a whole.
  • Figure 1 is a system diagram of a medical imaging system according to an embodiment of the invention.
  • Figure 2 is a schematic view of the medical imaging system
  • Figure 3 is a flowchart depicting a sampling method; and Figure 4 shows two graphs illustrating the polarisation intensity ⁇ and static conductivity a s , respectively, for three adipose-defined groups of samples.
  • FIG. 1 shows a medical imaging system 2 according to an embodiment of the invention.
  • the medical imaging system generally comprises a processor 4 and a microwave antenna array 6 in communication with the processor 4.
  • the antenna array 6 comprises a plurality N of antennas 16 which are arranged over the surface of, or within, a shell substrate 18.
  • the shell 18 has a curved profile as shown.
  • the shell 18 is part or hemi-spherical and is configured to approximate the shape of a breast.
  • the antennas 16 are arranged over the shell 18 such that they all point to a common focal point.
  • the antennas 16 are each electrically connected to a switching matrix 20.
  • the switching matrix 20 is in turn connected to both a transmit path and a receive path.
  • the transmit path comprises a signal generator 22 coupled to an amplifier 24.
  • the receive path comprises an amplifier 26 coupled to a detector 28 and the processor 4.
  • the switching matrix 20 selectively couples each of the antennas 16 to either the transmit path or the receive path.
  • the antenna array 6 is operated in a multi-static fashion. Specifically, the switching matrix 20 is controlled so as to connect one of the antennas 16 to the transmit path and the remaining antennas 16 to the receive path.
  • the signal generator 22 generates a stepped frequency continuous wave (CW) signal which is amplified by the amplifier 24 and then transmitted by the antenna 16 connected to the transmit path.
  • the stepped frequency continuous wave signal is a sequential series of pulses of continuous wave energy, where each pulse has its frequency stepped up across a range of frequencies, typically within the 3-8 GHz range.
  • the other antennas 16 receive the transmitted signal and the received signal is detected and then recorded by the processor 4.
  • the shell 18 receives a cup 30.
  • the cup 30 has a complementary shape to the shell 18 such that it fits tightly within the shell 18.
  • a layer of coupling fluid (dielectric constant controlled fluid) may be inserted in the gap 31 between the shell 18 and the cup 30 so as to improve the coupling between the antennas 16 and the cup 30 in order to minimise signal loss and thus improve transmission of the microwave signal.
  • An actuator (not shown), such as a motor, may be connected to the microwave antenna array 6.
  • the actuator is configured to move the microwave antenna array 6 relative to the cup 30 which remains stationary against the breast 36. Specifically, the actuator causes the microwave antenna array 6 to rotate relative to the cup 30 about the breast 36.
  • the microwave antenna array 6 rotates about the center of the shell 18 (i.e. its axis of symmetry).
  • This may be enabled by a threaded engagement between the cup 30 and the shell 18.
  • the outside of the cup 30 and the inside of the shell 18 may have threaded portions which engage to allow the shell 18 and the antenna array 6 to be rotated relative to the cup 30. This may also allow the cup 30 to be quickly and easily removed so as to enable the coupling fluid to be replaced.
  • the antennas 16 may be as described in WO 2009/060181.
  • the antennas 16 may comprise a slot 16 formed in a conductive element, the slot having a rectangular external boundary defined by a substantially closed internal edge of the conductive element.
  • a microstrip feed line may be spaced from the conductive element by a dielectric substrate with the distal end of the line positioned at the geometric centre of the slot.
  • a layer of coupling fluid may also be provided in the gap 35 between the cup 30 and the breast 36 in order to improve coupling between the antennas 16 and the breast 36.
  • FIG. 3 shows a flowchart of a data acquisition method.
  • the actuator is used to rotate the array 6 relative to the breast 36 while retaining the breast in position.
  • the acquisition process is then repeated with the antenna array 6 in the new configuration.
  • the processor 4 may record the relative difference between the measured phase and amplitude of the transmitted signal as compared to the phase and amplitude of the scattered signal, recorded as a complex number (having real and imaginary parts).
  • the signal detected at each antenna 16 is affected by scattering arising from objects within the imaged volume (i.e. the breast 36).
  • tumours can generate significant reflections as they exhibit much higher dielectric properties than adipose and connective tissues due to their significant water content and so can be identified in the acquired data.
  • the acquired data may be used by the processor 4 to construct an image of the internal structure of the breast 36.
  • the Data reconstruction may be performed using Phased Array (frequency domain), Delay and Sum (DAS - time domain) techniques or any other suitable technique, such as 3D Fourier Transformation, Back Projection, etc. From this, the processor 4 is able to identify (possibly, with additional user input or confirmation) a region of interest (if present) in which a possible tumour or other pathology may exist. It has been found that there is a correlation between the scattering parameters measured by the processor 4 and the density of the breast 36, and that this is in turn derived from a predetermined correlation between a change in permittivity with frequency and density.
  • the frequency dependent scattering coefficient (parameter) at a boundary is defined as:
  • Z 1 ( ⁇ ) is the frequency dependent impedance on the incident side of the boundary and ⁇ 2 ( ⁇ ) is the impedance on the transmitting side of the boundary.
  • the impedance is related to permittivity through:
  • ⁇ ⁇ is the frequency dependent permittivity on the incident side of the boundary and ⁇ 2 ( ⁇ ) is the permittivity on the transmitting side of the boundary.
  • the frequency dependent permittivity (and thus the change in permittivity with frequency) on the transmitting side of the boundary can be calculated from the scattering parameter(s) and vice versa by manipulating the above equation.
  • the correlation between the change in the permittivity (i.e. the change in ⁇ 2 ( ⁇ )) with frequency and density may be predetermined in any suitable or desired manner. However, in an embodiment this is done using a single pole Drude model of permittivity for biological tissues in the low microwave band (0.5-20GHz): Where ⁇ ⁇ is the relative permittivity at infinite frequency, ⁇ 0 is the permittivity of free space, ⁇ is the polarisation intensity, ⁇ is the angular frequency, ⁇ is the time constant, a is an exponent parameter, which takes a value between 0 and 1 , allowing the description of different spectral shapes and a s is the static conductivity contribution.
  • ⁇ and a s can be derived directly by fitting the Drude model to the values of ⁇ 2 ( ⁇ ) calculated from the scattering parameters obtained for the microwave signals over the range of frequencies. It was shown by Lazebnik et al (Phys Med Biol. 2007 Oct 21 ;52(20):6093-6115. A large- scale study of the ultrawideband microwave dielectric properties of normal, benign and malignant breast tissues obtained from cancer surgeries) that, while there is little or no correlation between ⁇ ⁇ , ⁇ and a and adipose content (i.e. breast density), there is a correlation between the polarisation intensity ⁇ and breast density and static conductivity a s and breast density. These relationships are illustrated in Figure 4.
  • Figure 4 shows two graphs illustrating the polarisation intensity ⁇ and static conductivity a s , respectively, for three adipose-defined groups of samples, where the upper and lower bounds indicate 25th and 75th quartile values.
  • adipose content and thus density
  • polarisation intensity ⁇ and static conductivity a s .
  • the change in permittivity with frequency therefore provides a good measure of breast density.
  • the change in permittivity relates to the 'colour' of the image or the change in the scattering parameters as a function of frequency.
  • the colour or microwave scattering (parameter) value(s) may therefore be correlated to density. This may be achieved empirically by generating test data for samples of known density or through calculation using, for example, equations linking permittivity and scattering coefficient through the impedance, as presented above. Alternatively, any other suitable method of correlating the data produced by the medical imaging system 2 to density may be used.
  • the medical imaging system 2 may enable the image to be toggled from scattering to density data or may allow the data to be overlaid in a single image.
  • the density values for each voxel may be averaged or assessed using some other statistical technique to provide a density value for the breast as a whole.
  • the density values may be used to provide a risk score for the patient. In this instance, the density values themselves need not be presented to the user or patient.
  • the density information may be generated from the raw data without generating an image of the breast 36.
  • the density information may be provided separately in a standalone test where there is no cause for scanning the breast 36 for suspicious lesions.
  • the system may therefore be embodied as a density measurement apparatus or meter which may or may not have the capability of imaging the breast. This information may serve as a useful pre- screening tool to identify the patient's risk score based on the breast density. This could be used to determine the screening frequency for the patient or other preventative measures based on the density assessment.
  • the system may be simplified from that described above.
  • the system may use a single antenna which serves to transmit and receive the microwave signal or a pair of antennas which transmit and receive. This may provide a single density value for the breast as a whole which is expected to correspond to the average value described above for the more complex antenna array.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Public Health (AREA)
  • Molecular Biology (AREA)
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  • Reproductive Health (AREA)
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Abstract

L'invention concerne un dispositif de mesure de densité mammaire destiné à de mesurer la densité d'un tissu mammaire et comprenant au moins une antenne hyperfréquences conçue pour émettre des signaux hyperfréquences sur une plage de fréquences de façon à éclairer le sein d'un(e) patient(e) et à recevoir les signaux hyperfréquences après leur diffusion à l'intérieur du sein. Un processeur est conçu pour obtenir un ensemble de paramètres de diffusion relatifs aux signaux hyperfréquences et pour déterminer une valeur de densité ou un indice de risque de cancer sur la base d'une valeur de densité mammaire à partir d'une corrélation prédéterminée entre une densité et les paramètres de diffusion qui sont à leur tour dérivés d'une corrélation prédéterminée entre une densité et un changement de permittivité en fonction de la fréquence, ce changement de permittivité pouvant être calculé à partir des paramètres de diffusion.
PCT/GB2017/053324 2016-11-04 2017-11-03 Appareil et procédé de mesure de densité mammaire WO2018083492A1 (fr)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109589115A (zh) * 2018-10-30 2019-04-09 水尚通讯技术(上海)有限公司 基于真实天线与分层模型的介质探测系统与方法
CN112545475A (zh) * 2020-11-05 2021-03-26 中国船舶重工集团公司第七0九研究所 一种基于fdtd的天线阵列共焦成像算法的脑部肿瘤检测方法及装置
CN114173677A (zh) * 2019-03-14 2022-03-11 美视医疗器械有限公司 混合医学成像探针、设备及过程

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006085052A2 (fr) * 2005-02-09 2006-08-17 The University Of Bristol Procedes et appareils permettant de mesurer la structure interne d'un objet
WO2009060181A1 (fr) 2007-11-05 2009-05-14 Micrima Limited Antenne pour examiner une structure d'humain ou d'animal

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006085052A2 (fr) * 2005-02-09 2006-08-17 The University Of Bristol Procedes et appareils permettant de mesurer la structure interne d'un objet
WO2009060181A1 (fr) 2007-11-05 2009-05-14 Micrima Limited Antenne pour examiner une structure d'humain ou d'animal

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
COLGAN TIMOTHY J ET AL: "A 3-D Level Set Method for Microwave Breast Imaging", IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, IEEE SERVICE CENTER, PISCATAWAY, NJ, USA, vol. 62, no. 10, 1 October 2015 (2015-10-01), pages 2526 - 2534, XP011668917, ISSN: 0018-9294, [retrieved on 20150916], DOI: 10.1109/TBME.2015.2435735 *
LAZEBNIK ET AL., PHYS MED BIOL., vol. 52, no. 20, 21 October 2007 (2007-10-21), pages 6093 - 6115
MAGDA EL-SHENAWEE: "Electromagnetic imaging for breast cancer research", BIOMEDICAL WIRELESS TECHNOLOGIES, NETWORKS, AND SENSING SYSTEMS (BIOWIRELESS), 2011 IEEE TOPICAL CONFERENCE ON, IEEE, 16 January 2011 (2011-01-16), pages 55 - 58, XP031923229, ISBN: 978-1-4244-8316-7, DOI: 10.1109/BIOWIRELESS.2011.5724362 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109589115A (zh) * 2018-10-30 2019-04-09 水尚通讯技术(上海)有限公司 基于真实天线与分层模型的介质探测系统与方法
CN114173677A (zh) * 2019-03-14 2022-03-11 美视医疗器械有限公司 混合医学成像探针、设备及过程
CN112545475A (zh) * 2020-11-05 2021-03-26 中国船舶重工集团公司第七0九研究所 一种基于fdtd的天线阵列共焦成像算法的脑部肿瘤检测方法及装置
CN112545475B (zh) * 2020-11-05 2022-12-02 中国船舶重工集团公司第七0九研究所 基于fdtd的天线阵列共焦成像算法的肿瘤检测方法及装置

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