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 x - ray mammography screening devices and methods with a system and method for further , real - time diagnosis of the x - ray results comprising an ultrasound subsystem for exciting target tissues and 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 multi - modality system 6 of the present invention with respect to the patient 1 and the imaging target breast 2 in one preferred embodiment of the present invention . an x - ray screening subsystem 80 , an ultrasound subsystem 10 and a microwave imaging subsystem 30 are employed in combination to screen / detect , image and diagnose / characterize tumors in the breast 2 . an x - ray detection medium 88 is disposed on the surface of a platform 86 . the x - ray detection medium 88 may be any useful medium , typically a film or semiconductor detector array . the target breast 2 is rested on the platform 86 such that the x - ray detection medium 88 is between the platform 86 and the target breast 2 . a compression paddle 90 is positioned above the target breast 2 with a downward force sufficient to hold the target breast 2 still during the imaging process and to compress the target breast 2 to enable a consistent image across the target breast 2 . an ultrasound electronics assembly 12 and a radiofrequency subsystem 32 are oriented as shown in physical communication with the target breast 2 . an x - ray camera 84 produces an x - ray beam 92 which travels through the target breast 2 to the x - ray detection medium 88 . tissues within the target breast 2 having different x - ray absorbing characteristics cause the incident x - ray intensity reaching the x - ray detection medium 88 to vary . the differential exposure of the x - ray detection medium 88 results in the capture of a two dimensional image of the target breast 2 , either in the form of exposed film or data from the exposed semiconductor detector array . in the preferred embodiment of the present invention , the x - ray detection medium 88 is a semiconductor detection array which then communicates the sensed x - ray intensity data to a computer / signal and data processor 94 . the computer / signal and data processor 94 processes that input data for communication to the technician via a display 96 . the display may be a video screen , a printing device , a photographic device , or any useful medium for communicating system output to the technician . the x - ray screening subsystem 80 outputs information regarding the presence and x - y planar location of suspicious tissues . the technician uses that information to conduct imaging and diagnosis of the target breast in the suspicious areas using the ultrasound subsystem 10 in combination with the microwave imaging subsystem 30 . fig2 presents a diagram of the ultrasound subsystem 10 . an ultrasound electronics assembly 12 is shown housing a first waveform generator 14 and a second waveform generator 15 , and a first power amplifier 16 and a second power amplifier 17 . waveform generator 14 produces a first input ultrasound waveform having frequency f 1 . waveform generator 15 produces a second input ultrasound waveform having frequency f 2 . power amplifier 16 conditions said first input ultrasound waveform and transmits the amplified ultrasound waveform to ultrasound transducer 22 . power amplifier 17 conditions said second input ultrasound waveform and transmits the amplified ultrasound waveform to ultrasound transducer 23 . ultrasound transducer 22 transmits the first amplified input ultrasound wave into the target breast 2 . ultrasound transducer 23 transmits the second amplified input ultrasound wave into the target breast 2 . to maximize transmission of said first and second ultrasound waves into the target breast 2 , an ultrasound conductive gel may be used at the interface of the ultrasound transducers 22 / 23 and the target breast 2 . in the present embodiment of the invention , the ultrasound transducers 22 / 23 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 . receiving capability may be added to the ultrasound subsystem 10 to enable use of the ultrasound subsystem 10 as an imaging and diagnosis tool without operation of the microwave imaging subsystem 30 . fig3 presents a diagram of the microwave imaging subsystem 30 comprising a radiofrequency ( rf ) subsystem 32 , a computer / signal & amp ; data processor 50 and a display 60 . the rf subsystem 32 comprises a microwave antenna 36 , a coupler 34 , and a radiofrequency ( rf ) transceiver 40 . the rf transceiver 40 comprises a waveform generator 42 , a power amplifier 44 , a linear noise amplifier 46 and a mixer 48 . the waveform generator 42 produces an input microwave . the power amplifier 44 conditions the input microwave and transmits said input microwave through the rf coupler 34 to the rf antenna 36 . the rf antenna 36 transmits said input microwave into the target breast 2 . to efficiently transmit the input microwave into the target breast 2 , the rf antenna 36 is in physical communication with the target 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 target breast 2 to enhance transmission into the target breast 2 . in an alternative embodiment , a dielectrically loaded antenna , in which the rf antenna 36 is embedded in a material that matches the dielectric constant of the target breast 2 , may be employed to reduce reflections . due to the wide propagation angle of the microwave in the target breast 2 , it is not necessary to move the rf antenna to scan the target breast 2 . however , an alternative embodiment of the present invention may employ an rf antenna 36 scanning means , if desired . microwaves reflected by normal and cancerous tissue boundaries and / or inclusions are collected by the rf antenna 36 and transmitted through a coupler 34 to a linear noise amplifier 46 . input microwaves from the waveform generator 42 and reflected microwaves from the linear noise 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 . 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 . in the preferred embodiment , the microwave imaging subsystem 30 utilizes continuous wave transmission for the purpose of performing imaging based upon the doppler effects of the displaced materials . the microwave imaging subsystem 30 may also utilize pulse - delay methodology to enable use of the microwave imaging subsystem 30 as an imaging and diagnosis tool without operation of the ultrasound subsystem 10 . fig4 shows the multi - modality system 6 of fig1 . fig4 a depicts the configuration and operation of the x - ray screening subsystem 80 , the ultrasound subsystem 10 , and the microwave imaging subsystem 30 with respect to the target breast 2 in a preferred embodiment of the present invention . fig4 b presents a typical spectral and pictorial display of the output from the combined operation of the ultrasound subsystem 10 and the microwave imaging subsystem 30 . as discussed in connection with fig1 , the information from the x - ray screening subsystem 80 is used to identify areas of interest for further imaging and diagnosis of the target breast 2 . the combined operation of the ultrasound subsystem 10 and the microwave imaging subsystem 30 constructs two - dimensional images of planes within the target breast 2 . by phased array control of the ultrasound subsystem 10 , data is collected for multiple planes at different depths within the target breast 2 . these multiple planes are combined to produce three - dimensional images . according to fig4 a , at time t 0 , the unexcited tumor 4 is at rest in location y 0 and the microwave antenna 36 is transmitting microwaves 56 into the target breast 2 . prior to activation of ultrasound transducers 22 / 23 , microwaves are reflected back to the microwave antenna 36 from the internal boundaries of the breast 2 and from inclusions in the breast 2 such as a tumor 4 . the reflected microwaves are of the same frequency as the transmitted input microwaves 56 . as depicted in fig4 b , the reflected microwave appears on the display 60 as a power spike 62 at the frequency of the transmitted wave 56 . no position or shape information of the tumor 4 is detectable prior to activation of the ultrasound transducers 22 / 23 . at time t 1 , a first ultrasound transducer 22 transmits a first ultrasound beam 24 having a frequency f 1 into the target breast 2 , and a second ultrasound transducer 23 transmits a second ultrasound beam 25 having a frequency f 2 into the breast 2 . the lenses of the ultrasound transducers 22 / 23 are designed to create focused ultrasound beams 24 / 25 which intersect at the target tumor 4 . in the preferred embodiment , ultrasound frequencies f 1 and f 2 are high frequencies with a small differential , or beat frequency ( f 1 - f 2 ). the high frequencies of the input ultrasound waves 24 / 25 provide superior resolution and focus capability , but poor tissue displacement force . but as the first and second high - frequency ultrasound waves 24 / 25 propagate and interact , they produce a series of harmonic waves . one resultant harmonic is a low - frequency wave at the beat frequency ( f 1 - f 2 ) resulting from the cancellation of the high - frequency components of the input waves . this low - frequency harmonic component produces a force that excites and displaces the target tissue and tumor 4 . due to the non - linear density and elastic properties of tissues and tumors in the breast 2 , the displacement of target tumor 4 can be detected by the microwave imaging subsystem 30 . expressed mathematically : source 2 = cos ( 2π f 2 t )= cos ( ω 2 t ) where ω = 2πf = angular frequency , and t = time due to high power at the intersection point of the ultrasound beams , non - linearity effects of the tissue become pronounced and the mixing of the two ultrasound signals becomes : the resultant displacement d of the tissue is given by the equation : d = 1 ( 2π f )* sqrt ( 2 fz ) where f = energy flux ( i . e ., power per area ), z = tissue acoustic impedance , typically ˜ 1 . 5e 6 kg / m 2 / s , and f = acoustic frequency ( in this case f 1 - f 2 ). since ω 1 and ω 2 are high frequency to achieve good resolution , then terms with twice the frequency ( cos ( 2ω 1 ), cos ( 2ω 1 ) and cos ( ω 1 + ω 2 )) will be of high frequency and their effect on the motion will be limited . on the other hand , if ω 1 and ω 2 are selected to be close to each other such that ( ω 1 − ω 2 ) would be very small ( i . e ., in order of 100s - 1000s hz ), then the term cos (( ω 1 − ω 2 ) t ) will lead to a large displacement . at time t 2 , the low - frequency ultrasound component impacts the tumor 4 and displaces the tumor 4 to location y 2 . the tumor 4 oscillates between location y 2 and y 0 before coming to rest again at essentially the initial location y 0 . the ultrasound waves 24 / 25 travel at a significantly lower rate of speed than the microwave 56 . as the tumor 4 oscillates between position y 0 and position y 2 , the doppler effect results in a shift in the frequency of the reflected microwaves . 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 ultrasound pulse passing through the tumor 4 . the power of the sidebands 64 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 + 2π − δ r ( t )/ λ + φ 0 ] where ω c is the carrier frequency and ω 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 / 4λ 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 : fig5 shows an alternative embodiment of the present invention wherein the microwave antenna 36 is oriented on the same side of the breast as the ultrasound transducers 22 / 23 . the concept of operation and the method of use are identical to that of the embodiment of fig4 , but this alternative may provide packaging advantages over that embodiment . fig6 presents an alternative embodiment of the present invention wherein an acoustic hydrophone 28 is employed in combination with the microwave imaging modality to perform diagnosis and imaging functions . the acoustic hydrophone 28 receives sonic waves 29 generated by the motion induced in the tissue by the ultrasound beams 24 / 25 . the displacement data collected by the acoustic hydrophone 28 may be combined with the high - contrast , high - specificity data collected by the microwave modality to augment the diagnosis function . an alternative embodiment of the present invention employs ultrasound arrays 112 / 114 in place of the scanning ultrasound transducers 22 / 24 . fig7 illustrates an exemplary ultrasound array implementation . fig7 a presents a plan view of a 6 × 6 ultrasound array 112 with ultrasound transducer elements arranged in a matrix of rows 1 through 6 and columns a through f . fig7 b presents a side view of two 6 × 6 ultrasound arrays 112 / 114 . the two ultrasound arrays operate in cooperation to transmit ultrasound waves into the breast . by selectively activating ultrasound elements of each of the arrays , the paired arrays 112 / 114 can focus input ultrasound energy waves at the intersection of the ultrasound beam centerlines of the activated ultrasound elements . further , electronic tuning of the dual - array system permits focus between the centerline intersection points . this embodiment permits detection to be performed throughout a large volume of the breast without the need for scanning . this embodiment trades the physical complexity and longer examination time associated with scanning implementations for the greater electronic implementation complexity of the ultrasound array implementation . while a symmetrical 6 × 6 array is shown to illustrate the concept , many array configurations may be usefully employed . 3 × 120 and 5 × 120 non - symmetrical arrays and 1 × 120 linear arrays are found in literature . fig8 presents an alternative embodiment of the ultrasound subsystem 10 in which a single ultrasound transducer 26 is employed to input multiple ultrasound waves integrated into a single ultrasound beam 27 . fig8 a presents one preferred embodiment of this alternative wherein the microwave antenna 36 and the ultrasound transducer 26 are positioned on opposite sides of the breast 2 . an alternative embodiment positions a single annular ultrasound transducer around the microwave antenna 36 such that the transducer and antenna are on the same side of the breast 2 . fig8 b provides a diagram of the ultrasound system 10 with a single ultrasound transducer 27 . in this embodiment , waveform generator 14 produces a first input ultrasound waveform 8 having frequency f 1 . waveform generator 15 produces a second input ultrasound waveform 9 having frequency f 2 . a first power amplifier 16 conditions the first input ultrasound waveform 8 and transmits said first ultrasound waveform 8 to a summer 21 . a second power amplifier 17 conditions the second input ultrasound waveform 9 and transmits said second ultrasound waveform 9 to the summer 21 . the summer 21 combines said first and second input ultrasound waveforms 8 / 9 and transmits the combined waveforms 8 / 9 to a single ultrasound transducer 26 . the ultrasound transducer 26 transmits the combined input ultrasound waves 8 / 9 , in a single , integrated focused ultrasound beam 27 comprising both f 1 and f 2 components , into the breast 2 . as discussed relative to the embodiment of fig4 , the combined high - frequency ultrasound waves 8 / 9 propagate and interact to produce a series of harmonic waves . one resultant harmonic is a low - frequency wave at the beat frequency ( f 1 - f 2 ). this low - frequency harmonic component produces a force that excites and displaces the target tumor 4 . fig9 presents a diagram of an enhancement to the present invention wherein a closed - loop feedback control system utilizes information from the microwave imaging subsystem 30 to provide input instructions to the ultrasound subsystem 10 thereby enhancing the efficiency , accuracy and quality of the screening and diagnosis process . the ultrasound subsystem 10 excites the region of interest resulting in displacement d of the target tumor 4 . the microwave imaging subsystem 30 detects microwaves reflected by the excited target tumor 4 . the microwave imaging subsystem 30 processes the detected microwaves into detection , diagnosis and imaging information which is made available to the technician by means of the display 60 . microwave imaging subsystem information 102 is further processed by means of a computer / signal and data processor 50 into ultrasound subsystem input instructions 104 which are communicated to the ultrasound subsystem 10 . scanning process efficiency may be enhanced by providing real time instructions such as desired scanning regions , patterns and depths . image quality may be controlled by providing real time instructions relative to resolution , contrast , power levels , continuous waveform versus pulse , pulse rate , drift compensation / stability , accuracy , noise and scan velocity . various embodiments of the present invention may be exercised in ways other than 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 will 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 . 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 helpful in understanding the foregoing specification and are incorporated herein by reference : li , xu , et al . 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