Patent Application
20050288581
The present invention relates generally to an image acquisition technique and specifically to acoustic coupling gels and devices, such as for co-registration of mammography and ultrasound images.
In modern healthcare facilities, medical diagnostic and imaging systems are used for identifying, diagnosing, and treating diseases. Diagnostic imaging refers to any visual display of structural or functional patterns of organs or tissues for a diagnostic evaluation. Currently, a number of modalities exist for medical diagnostic and imaging systems. These include, for example, ultrasound systems, X-ray imaging systems (including mammography system), molecular imaging systems, computed tomography (CT) systems, positron emission tomography (PET) systems and magnetic resonance imaging (MRI) systems.
One known imaging technique is mammography, by which a breast of a patient may be non-invasively examined or screened to detect abnormalities, such as lumps, fibroids, lesions, calcifications, and so forth. Typically mammography employs specialized radiographic techniques to generate images representative of a breast tissue. A mammography imaging system typically comprises an X-ray imaging system, which uses a source of radiation, such as an X-ray source, a breast-positioning sub-system, an X-ray detector for imaging, data acquisition computers, control software and display monitors. X-ray imaging is generally very effective for detailed characterization of benign and cancerous structures such as calcifications and masses embedded in the breast tissue.
Another known imaging technique is ultrasound. An ultrasound imaging system uses an ultrasound probe for transmitting ultrasound signals into an object, such as the breast of the patient being imaged, and for receiving reflected ultrasound signals there from. The reflected ultrasound signals received by the ultrasound probe are processed to reconstruct an image of the object. Ultrasound imaging is very effective at other types of diagnosis, such as for differentiating benign cysts and masses.
Co-registered mammography and ultrasound image acquisition is a technique wherein dual modality images are acquired with the patient in virtually the same position within a single examination so that the duel modality images (image sets) are intrinsically registered to one another. When the breast of the patient is in a compressed state, image data is generated by the ultrasound imaging system and is combined with data from the X-ray imaging system to leverage strengths of both techniques.
In an ultrasound imaging system, an ultrasonic coupling gel or paste is typically used to ensure proper contact between the ultrasound probe of the ultrasound system and skin of the patient being imaged. Ultrasound gels generally ensure good transmission of acoustic energy, but have certain drawbacks, particularly in applications such as multi-modality mammography. For example, they can be messy to apply, and generally require subsequent clean up of both the patient and imaging equipment (e.g. the ultrasound probe) that may come into contact with the gel during an imaging session. Further a non-uniform application of the coupling gel could easily lead to a sub-optimal image quality.
Thus, there exists a need for a new technique for providing acoustic coupling between the ultrasound probe and an object to be imaged. There is a particular need for a technique that is compatible for mammography and ultrasound imaging techniques for co-registered mammography and ultrasound image data acquisition.
Briefly, in accordance with one aspect of present invention, a combined mammography and ultrasound imaging system is provided. The system includes an ultrasound probe, which transmits ultrasound signals to a breast of a patient and receives reflected ultrasound signals from the breast. The system further includes a first acoustic coupling sheath. A first side of the first acoustic coupling sheath is coupled to a face of the ultrasound probe. The system also includes a mammography compression plate for compressing the breast of the patient. A second acoustic coupling sheath coupled to a side of the mammography compression plate contacts the breast of the patient.
A method of conducting a mammography examination is also provided. The method generally includes coupling an acoustic coupling sheath to a lower surface of a mammography compression plate. An object, like a breast of a patient, is then compressed between an X-ray detector and the acoustic coupling sheath via the mammography compression plate. Image data is acquired for reconstruction of mammography image.
In a variation of the invention, the method includes coupling a first side of a first acoustic coupling sheath to a face of an ultrasound probe. The method also includes coupling a second acoustic coupling sheath to a lower surface of a mammography compression plate. Then an object, like a breast of a patient, is compressed between an X-ray detector and the second acoustic sheath and via the mammography compression plate. The method further includes acquiring ultrasound image data by transmitting acoustic energy through the first acoustic coupling sheath, the mammography compression plate and the second acoustic coupling sheath to the compressed breast.
A method of acquiring a co-registered mammography and ultrasound image is also provided. The method includes coupling a first side of a first acoustic coupling sheath to a face of an ultrasound probe. The method also includes coupling a second acoustic coupling sheath to a lower surface of a mammography compression plate. An object, like a breast of a patient to be imaged is compressed between the second acoustic coupling sheath and an X-ray detector via the mammography compression plate. Mammography image data is acquired for reconstruction into a mammography image and for further analysis. Then ultrasound image data is acquired by transmitting acoustic energy through the first acoustic coupling sheath, the second acoustic coupling sheath and the mammography compression plate in conjunction with the analysis based on the mammography image.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
The present technique is directed towards co-registration of mammography and ultrasound images and specifically to acoustic coupling gels for such co-registration. In general, the co-registration technique employs a mammography imaging system and an ultrasound imaging system. As will be appreciated by those of ordinary skill in the art, the present techniques may also be applied in other medical and non-medical contexts.
Turning now to the drawings, and referring first to
The X-ray source 14 further comprises an X-ray tube and a collimator configured to generate a beam of X-rays when activated. The X-ray tube is one example of the X-ray source 14. Other types of the X-ray sources 14 may include some or all of emitters of a solid state X-ray source. The X-ray source 14 may be movable in one, two or three dimensions, either by manual or by automated means. The image data acquisition system 12 may move the X-ray source 14 via tracks, ball-screws, gears, belts, and so forth. For example, the X-ray source 14 may be located at an end of a mechanical support, such as a rotating arm or otherwise adjustable support, which may be moved by the image data acquisition system 12.
The X-ray detector 16 may be stationary, or may be configured to move either independently or in synchrony with the X-ray source 14. In a present embodiment, the X-ray detector is a digital flat panel detector. The image data acquisition system 12 may move the X-ray detector 16 via tracks, ball-screws, gears, belts, and so forth. The X-ray detector also provides support an object, such as a breast of a patient to be imaged in the mammography application described below.
The compression assembly 18 is configured to compress the patient breast to near uniform thickness against the X-ray detector 16 for performing mammography imaging. The compression assembly 18 comprises a mammography compression plate 20, which may be a flat, inflexible plate, or alternative compression device. The mammography compression plate 20 is configured to be radiolucent to transmit X-rays and is further configured to be sonolucent to transmit ultrasound signals. The compression assembly 18 may be used to acquire co-registered mammography, ultrasound images, tomosynthesis X-ray images and Doppler images.
The system controller 22 controls operation of the image data acquisition system 12 that provides for a physical motion required by the X-ray source 14 and/or the X-ray detector 16. Movement is, in turn controlled through the motor controller 24 in accordance with an imaging trajectory for use in mammography. Therefore, by means of the image data acquisition system 12, the system controller 22 may facilitate acquisition of radiographic projections at various angles through a patient. The system controller 22 further controls an activation and operation of other components of the system, including collimation of the X-ray source 14. Moreover, the system controller 22 may be configured to provide power and timing signals to the X-ray source 14. The system controller 22 may also execute various signal processing and filtration functions. In general, the system controller 22 commands operation of the mammography imaging system 10 to execute examination protocols and to acquire resulting data.
The system controller 22 controls the data acquisition and image-processing module 26. The data acquisition and image-processing module 26 communicates with the X-ray detector 16 and typically receives data from the X-ray detector 16, such as a plurality of sampled analog signals or digitized signals resulting from exposure of the X-ray detector to X-rays. The data acquisition and image-processing module 26 may convert the data to digital signals suitable for processing.
The operator interface 28 may include a keyboard, a mouse, and other user interaction devices. The operator interface 28 can be used to customize settings for the mammography imaging and for affecting system level configuration changes. The operator interface 28 is connected to the data acquisition and image-processing module 26, the system controller 22 and the display module 30. The display module 30 presents a reconstructed image of an object within a region of interest based on data from the data acquisition and image-processing module 26. As will be appreciated by those skilled in the art, digitized data representative of individual picture elements or pixels is processed by the data acquisition and image-processing module to reconstruct the desired image. The image data, in either raw or processed forms, may be stored in the system or remotely for later reference and image reconstruction.
The ultrasound imaging system 32 uses the ultrasound probe 34 for transmitting a plurality of ultrasound signals into an object, such as a breast of a patient being imaged, and for receiving a plurality of reflected ultrasound signals there-from. The ultrasound probe 34, according to aspects of present technique, includes at least one of an ultrasound transducer, a piezoelectric crystal, an opto-acoustic transducer and a micro electromechanical system device. As will be appreciated by those of ordinary skill in the art, the plurality of reflected ultrasound signals from the object carry information about thickness, size, and location of various tissues, organs, tumors, and anatomical structures in relation to transmitted ultrasound signals. The plurality of reflected ultrasound signals received by the ultrasound probe 34 are processed for constructing an image of the object. In certain embodiments, the ultrasound probe 34 can be hand-held or mechanically positioned using a robotic assembly.
The data acquisition and image-processing module 36 sends signals to and receives information from the ultrasound probe 34. Thus, the data acquisition and image-processing module 36 controls strength, width, duration, and a frequency of the plurality of ultrasound signals transmitted by the ultrasound probe 34, and decodes the information contained in the plurality of reflected ultrasound signals from the object to a plurality of discernable electrical and electronic signals. Once the information is obtained, an ultrasound image of the object located within a region of interest of the ultrasound probe 34 is reconstructed in accordance with generally known reconstruction techniques.
The operator interface 38 may include a keyboard, a mouse, and other user interaction devices. The operator interface 38 can be used to customize a plurality of settings for an ultrasound examination, and for effecting system level configuration changes. The operator interface 38 is connected to the data acquisition and image-processing module 36, the display module 40 and to the printer module 42. The display module 40 receives information from the data acquisition and image-processing module 36 and presents the image of the object within the region of interest of the ultrasound probe 34. The printer module 42 is used to produce a hard copy of the ultrasound image in either gray-scale or color. As noted above, some or all of these system components may be integrated with those of the X-ray system described above.
The ultrasound probe 46 is configured to transmit and receive ultrasound signals. The first acoustic coupling sheath 48 comprises a layer of adhesive on a first side 58. The first acoustic sheath is coupled to a face 60 of the ultrasound probe 46. The first acoustic coupling sheath 48 is further configured to act as an ultrasonic acoustic coupling to ensure proper contact for transmission of the ultrasound signals. The mammography compression plate 50 is sonolucent and radiolucent and is capable of transmitting both ultrasound signals and X-rays. The mammography compression plate 50 is primarily used for compressing the breast of the patient in combination with the X-ray detector 52 to a near uniform thickness for acquiring mammography images.
The second acoustic coupling sheath 54 is also sonolucent and radiolucent and is capable of transmitting both ultrasound signals and X-rays. The second acoustic coupling sheath 54 comprises layers of adhesive on a first side 62 and on a second side 64. The second acoustic coupling sheath may be of any suitable size to cover the entire breast, or only a portion thereof, as desired for the anatomical structures to be imaged. The second acoustic coupling sheath 54 is coupled to the mammography compression plate 50. The first side 62 of the second acoustic coupling sheath 54 abuts a lower surface 66 of the mammography compression plate 50, while the second side 64 is configured to contact a breast of a patient 56 to ensure proper contact for transmission of the ultrasound signals. The ultrasound probe 46, along with the first acoustic coupling sheath 48 moves over a top surface 68 of the mammography compression plate 50 either manually or mechanically to transmit ultrasound signals. As appreciated by those skilled in the art, a moistening agent or a wetting agent such as water or glycol may be applied over the top surface 68, i.e., between the ultrasound probe and the mammography compression plate, to reduce friction and improve wetting characteristics. During the ultrasound portion of a breast examination, then, the ultrasound signals are transmitted through the first acoustic coupling sheath 48, the mammography compression plate 50, the second acoustic coupling sheath 54 to the breast 56 and to receive reflected ultrasound signals there from to acquire images of the breast 56. It can be noted that the mammography compression plate enables exerting uniform and sufficient pressure on the breast for medical examinations.
Based upon the X-ray and ultrasound image data acquired, combined image may be produced. That is, while separate images may be used for diagnostic and other purposes, the image processing circuitry may be configured to register X-ray images with ultrasound images for enhanced diagnostic purposes. In other situations, based upon features visible in either X-ray or ultrasound images, or both, additional images may be acquired during an examination via either the mammography imaging system or the ultrasound imaging system, or both.
It should be noted that, while use of the sheaths described above is particularly useful for the mammography application, such use is not limited to breast imaging. The probe sheath, in particular, may be used in many other applications. In general, both sheaths are designed to be disposable for single use. Application of the sheaths is facilitated by adhesive provided on one or both of their faces. Such adhesive may be of any suitable type, such as adhesives commonly used in medical applications for transmission of acoustic energy. It should also be noted that size and configuration of the sheaths, and particularly of the probe sheath, may be adapted for specific equipment. A number of different sheaths may thus be designed for probes made by various manufactures, as well as for specific probe models. Similarly, sheaths designed to interface a mammography compression plate with the patient tissue may be made in various sizes and configurations, allowing for selection by clinicians based upon the size of the tissue to be imaged.
It should also be noted that the sheaths may be made of homogeneous material. These sheaths impregnated with acoustic gel may include, for example, sheaths commercially available from Sonotech Inc of Bellingham, Wash., USA. As appreciated by those skilled in the art these sheaths provide low and uniform attenuation throughout mammography and ultrasound fields of view during medical examinations as opposed to conventional gels, the thickness and distribution of which can vary substantially.
Furthermore, some medical examinations require imaging the breast at different orientations. For example, during cranio-caudal (CC) imaging, the ultrasound imaging is carried out with the ultrasound probe being above the breast. During medial lateral oblique (MLO) imaging, the imaging system components (e.g. mammography compression plate and X-ray detector) may be oriented to 30 degrees, 45 degrees and up to 90 degrees. In such situations where the imaging system components may be positioned at various angles such as those for oblique views of the breast, the acoustic-coupling sheaths enhance ease of use over standard gels, which may be less effective due to insufficient viscosity of the gel. (i.e. causing running of the gel).
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
This invention was made with Government support under contract number RO1 CA91713 01A1 awarded by the United States National Institutes of Health. The Government has certain rights in the invention.
