Patent Abstract:
a multi - modality system and method for performing screening / detection , imaging and diagnosis / characterization of materials and objects in dense compressive media , such as in medical soft tissue applications , is disclosed . medical tissue applications include but are not limited to the detection and diagnosis of breast tumors . generally , the present invention involves coupling an ultrasound subsystem for exciting target tissues with a microwave subsystem for measuring the response , imaging and diagnosing the target tissues .

Detailed Description:
the following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventor of carrying out his invention . further , while a breast is used in the description of these embodiments , it is to be noted that any turbid medium may be processed with this invention . thus the present invention shall not be limited to the examples disclosed . the scope of the invention shall be as broad as the claims will allow . referring now to the drawings , fig1 shows the orientation of the system with respect to the patient 1 and the imaging target breast 2 in one preferred embodiment of the present invention . an ultrasound subsystem 10 and a microwave imaging subsystem 30 are employed in combination to detect and diagnose tumors in the breast 2 . an ultrasound transducer 22 and a microwave antenna 36 are oriented with respect to the target breast 2 of the patient 1 . in one preferred embodiment , the ultrasound transducer 22 is oriented along the same axis , the z - axis , as the microwave antenna 36 : the ultrasound transducer 22 aimed in the negative z direction and the microwave antenna 36 aimed in the positive z direction . a radio frequency transceiver 40 generates and transmits microwave signals to the microwave antenna 36 . the microwave antenna 36 transmits microwaves into the target breast 2 . reflected microwaves are collected by the microwave antenna 36 and received by the radio frequency transceiver 40 . a computer / signal and data processor 50 containing signal processing circuitry and data processing algorithms processes the output of the radio frequency transceiver 40 and sends the resultant data to the display 60 for access by the technician . the display 60 may be a video screen , a printing device , a photographic device , an oscilloscope , a spectrum analyzer , or any useful medium for communicating system output to the technician . the data may be usefully represented as individual spectra , one - dimensional line scans , two - dimensional cross - sectional constructions , or volume images . a scan controller / actuator 18 working in combination with a mechanical actuator 20 orients the ultrasound transducer 22 to enable scanning of the entire target breast 2 . an ultrasound electronics assembly 12 generates and transmits ultrasound waves to the ultrasound transducer 22 . the ultrasound transducer transmits the ultrasound waves to the target breast 2 to stimulate the tissues therein . fig2 provides a schematic representation of the ultrasound subsystem 10 . an ultrasound electronics assembly 12 is shown housing a waveform generator 14 and a power amplifier 16 . the waveform generator 14 produces an input ultrasound waveform . the power amplifier 16 conditions the input ultrasound waveform and transmits said ultrasound waveform to the ultrasound transducer 22 . the ultrasound transducer 22 transmits the amplified input ultrasound wave 8 into the target breast 2 . to maximize transmission of the ultrasound wave 8 into the breast , an ultrasound conductive gel may be used at the interface of the ultrasound transducer 22 and the target breast 2 . in a preferred embodiment of the present invention , the ultrasound transducer 22 must be physically relocated to perform a scan of the entire breast 2 . this scanning function is performed by a scan controller / actuator 18 working in combination with a mechanical actuator 20 . fig3 provides a schematic representation of the microwave imaging subsystem 30 comprising an rf subsystem 32 , a computer / data processor 50 and a display 60 . the rf subsystem 32 comprises an rf antenna 36 , a coupler 34 , and an rf transceiver 40 . the rf transceiver 40 comprises a waveform generator 42 , a power amplifier 44 , an amplifier 46 and a mixer 48 . the waveform generator 42 produces an input waveform . the power amplifier 44 conditions the input waveform and transmits said waveform through the rf coupler 34 to the rf antenna 36 . the rf antenna 36 transmits the microwave 6 into the target breast 2 . to efficiently transmit the microwave 6 to the breast 2 , the rf antenna 36 is in physical contact with the breast 2 . in a preferred embodiment of the present invention , the rf antenna 36 is made from a material that closely matches the dielectric constant of the breast 2 . in an alternative embodiment , a dielectrically loaded antenna , in which the antenna 36 is embedded in a material that matches the dielectric constant of the breast 2 , may be employed to reduce reflections . due to the wide propagation angle of the microwave 6 in the breast 2 , it is not necessary to move the rf antenna to scan the breast 2 . however , an alternative embodiment of the present invention may employ an rf antenna 36 scanning means , if desired . microwaves reflected by normal / cancerous tissue boundaries and / or inclusions are collected by the microwave antenna 36 and transmitted through the coupler 34 to an amplifier 46 . input waveforms from the waveform generator 42 and reflected microwaves from the amplifier 46 are passed through a mixer 48 and conveyed to an analog - digital processor 52 . data processing algorithms 54 such as demodulation , and lockin detection or fast fourier transform algorithms operate on the digital data from the analog - digital processor 52 . the resultant frequency and power data is transmitted to a display 60 for viewing by the technician . fig4 shows the microwave 6 transmission into the target breast 2 , and the resultant display of the reflected microwaves , at time t 0 prior to activation of the ultrasound subsystem 10 . in one preferred embodiment of the present invention , a continuous microwave 6 is employed . it is anticipated that other input waveforms and methods , such as frequency modulation and pulse - delay , may be usefully employed to reduce clutter signals and improve the probability of tumor detection . the microwave 6 is transmitted by the rf antenna 36 into the breast 2 . prior to activation of the ultrasound subsystem 10 , microwaves will be reflected back to the rf antenna 36 from the internal boundaries of the breast and from inclusions in the breast 2 such as a tumor 4 . the reflected microwaves will be of the same frequency as the transmitted input microwaves 6 . the reflected microwave will appear on the display 60 as a power spike 62 at the frequency of the transmitted wave . no position or shape information of the tumor 4 is detectable prior to activation of the ultrasound subsystem 10 . fig5 shows the ultrasound wave 8 transmission through the subject breast 2 , the resultant displacement of the target tumor 4 , and the spectral representation of the reflected microwaves 6 resulting from the ultrasound stimulation of the tumor 4 . at time t 0 , no ultrasound waves have been transmitted into the breast 2 . the tumor 4 is at rest at location z 0 . a continuous microwave is transmitted into the breast 2 and reflections from the boundary of the breast 2 and the tumor 4 are displayed as a power spike 62 at the same fundamental frequency as that of the input microwave 6 . at time t 1 , an ultrasound wave 8 is introduced into the breast 2 . in one preferred embodiment of the present invention , the ultrasound transducer 22 lens is designed to create a collimated ultrasound wave 8 which propagates essentially in a column through the breast 2 . the ultrasound wave 8 travels at a significantly lower rate of speed than the microwave 6 . at time t 2 , the ultrasound wave impacts the tumor 4 and displaces said tumor 4 to location z 2 . as the ultrasound wave passes the tumor 4 , the tumor oscillates between location z 2 and z 0 before coming to rest again at essentially the initial location z 0 . as the tumor 4 oscillates between position z 0 and position z 2 , the doppler effect results in a shift in the frequency of the reflected microwave . these frequency shifts appear on the display 60 as frequency sidebands 64 . presence of these sidebands indicates the presence of a tumor 4 . the sidebands 64 are short lived , essentially lasting for the duration of the ultrasonic pulse passing through the tumor 4 . the power of the sidebands is determined through displacement analysis . if a signal is reflected off of a target whose range is changing with time according to r ( t )= r 0 + δr ( t ), the received signal can be written as : s ( t )= cos [ ω c t + 2 π − δr ( t )/ λ + φ 0 ] where ω c is the carrier frequency and φ 0 is the phase for a small - amplitude oscillation of a target with a displacement d and a modulation frequency fm , the range is given by : s ( t )= cos [ ω c t + 2π −( d / λ ) sin ( ω m t )+ φ 0 ] p sideband = 10 log ( d 2 / 4 λ 2 )= 20 log ( π f c d / c ) dbc . if sensitivity is not sufficient , and to give system sensitivity a boost , a continuous wave may be employed such that : fig6 prevents an alternative embodiment of the ultrasound subsystem 10 featuring an array of ultrasound transducers 22 . use of an array of transducers 22 is an alternative to scanning with a single ultrasound transducer 22 . in this alternative , the design and operational complexities of a scanning system are traded against the design and operational complexity of a fixed array . a 4 × 4 array is shown for illustrative purposes . it is obvious and anticipated that arrays of various sizes may be usefully employed . fig7 presents an alternative embodiment and operation of the ultrasound subsystem 10 . fig7 a shows the ultrasound transducer 22 designed to generate a collimated ultrasound wave 8 . this configuration is used to perform the detection function . upon detection of a tumor 4 , an ultrasound transducer 22 designed to generate a focused ultrasound wave 9 is located such that the focal point of the ultrasound wave 9 is concentrated on the tumor 4 as shown in fig7 b . this configuration is used to perform the diagnosis function , enabling higher resolution definition of tumor size and shape , and the presence of multiple tumors . fig8 presents an alternative embodiment of the present invention employing paired ultrasound transducers 22 and microwave antennas 36 in multi - axis orientations . this configuration enhances detection of multiple tumors , particularly in the case where one or more tumors would be in the shadow of another tumor in a single - axis detection configuration . for illustrative purposes , one transducer 22 / antenna 36 pair is shown oriented along the z - axis working in combination with another transducer 22 / antenna 36 pair oriented along the x - axis . fig9 shows an alternative embodiment of the multi - modality imaging system implementing both the ultrasound transducer 22 and the microwave antenna 36 on the same side of the subject breast 2 . for illustrative purposes , a single microwave antenna 36 is depicted with an array of ultrasound transducers 22 . an alternative embodiment is to replace the array of ultrasound transducers 22 with a single ultrasound transducer 22 which is actuated to scan the target breast 2 . these alternative configurations enable simplified apparatus design . fig1 presents alternative scanning approaches . fig1 a illustrates a representative x - y planar scanning scheme wherein the ultrasound transducer 22 is moved sequentially from station to station in the x - y plane as shown for an exemplary 4 × 4 scanning matrix . in this scheme , the ultrasound transducer 22 transmits ultrasound waves 8 at each sequential location . fig1 b illustrates an alternative scanning scheme wherein the ultrasound transducer 22 is transmitting continuously as it is moved in circular paths of increasing diameter . in this example , the ultrasound transducer 22 begins operation at point a , is indexed to point b , follows path b , then is indexed to point c and follows path c . other continuous - scan patterns may be employed , such as moving the ultrasound transducer 22 in a continuously - increasing spiral pattern in the x - y plane . various embodiments of the present invention may be exercised in ways other than those illustrated in the examples shown in the figures . such alternative embodiments are within the contemplation of the present invention . the examples are not intended to limit the scope of this invention , which shall be as broad as the claims will allow . in addition , the present invention may be adapted to a variety of applications in both medical and non - medical fields . the field of medical soft tissue imaging includes orthopedics , dermatology , breast tumor screening / detection , imaging and diagnosis / characterization , and other medical applications . such alternative applications are within the contemplation of the present invention and the scope of the invention shall be as broad as the claims allow . the physical implementation of the present invention may be varied without departing from the spirit of the invention . elements and components may be implemented , added , interchanged , combined and / or packaged in a variety of embodiments . various changes may be effected in structure , design , choice of components and materials , etcetera without departing from the spirit of the present invention . such alternative embodiments , elements and implementations are within the contemplation of the present invention and the scope of the invention shall be as broad as the claims allow . accordingly , the scope of the invention should be determined not by the embodiments illustrated , but by their legal equivalents , and shall be as broad as the claims will allow . the following references are of utility in understanding the foregoing specification , and are incorporated herein by reference : christiane kuhl , et . al ., “ mri for diagnosis of pure ductal carcinoma in situ : a prospective observational study ,” the lancet , vol . 370 , issue 9586 , 11 aug . 2007 , pages 485 - 492 . li , xu , et . al . 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