X-RAY SCATTER REDUCING DEVICE FOR USE WITH 2D MAMMOGRAPHY AND TOMOSYNTHESIS
Systems and methods for reducing X-ray scatter during breast imaging, and more specifically during tomosynthesis imaging. In one embodiment, an anti-scatter grid having a plurality of septa may be configured to be positioned relative to an X-ray imaging device such that each septum of the plurality of septa extends along a direction substantially parallel to a coronal plane of a subject during imaging of the subject using the X-ray imaging device. The X-ray imaging device may be operable in a tomosynthesis mode for imaging of a breast of the subject and may include the anti-scatter grid disposed between a breast platform and the X-ray detector. The anti-scatter grid may be configured to move in a direction substantially parallel to a sagittal plane of the subject during tomosynthesis imaging.
- 1-36. -36. (canceled)
- 37. A method of reducing x-ray scatter in a tomosynthesis system comprising an x-ray source and an x-ray detector, the method comprising:
positioning an anti-scatter grid between the x-ray source and the x-ray detector, wherein the anti-scatter grid comprises a plurality of septa; orienting the plurality of septa in an orientation substantially parallel to a coronal plane of a subject; compressing a breast of the subject; moving the x-ray source along a path about the breast of the subject; emitting a plurality of x-ray exposures from the x-ray source during movement of the x-ray source; and during emission of the plurality of x-ray exposures from the x-ray source, moving the x-ray anti-scatter grid relative to at least one of the x-ray source and the x-ray detector.
- View Dependent Claims (38, 39, 40, 41, 42, 43, 44)
- 45. A method of imaging a breast with an imaging system, the method comprising:
receiving a breast on a breast support platform, wherein an x-ray detector is disposed on a side of the breast support platform opposite the breast; compressing the breast between the breast support platform and a breast compression paddle; disposing an anti-scatter grid between the x-ray detector and the breast support platform; imaging the breast in a first imaging mode, wherein the first imaging mode comprises a tomosynthesis imaging mode; retracting the anti-scatter grid from between the x-ray detector and the breast support platform; and imaging the breast in a second imaging mode, wherein the second imaging mode comprises a mammography imaging mode.
- View Dependent Claims (46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56)
This application is being filed on 13 Mar. 2014, as a PCT International patent application, and claims priority to U.S. Provisional Patent Application No. 61/790,336, filed Mar. 15, 2013, which is incorporated by reference in its entirety into the present application.
The present invention generally relates to radiography and more specifically to anti-scatter devices and methods of reducing X-ray scatter for breast imaging.
X-ray mammography systems are widely used for breast imaging. More recently, advanced imaging systems based on tomosynthesis have been developed (or use in screening of breast cancer and other lesions. Tomosynthesis systems are three-dimensional (3D) mammography systems that allow high resolution breast imaging based on limited angle tomography at mammographic X-ray dose levels. In contrast to typical two-dimensional (2D) mammography systems, a tomosynthesis system acquires a series of X-ray projection images, each projection image obtained at a different angular displacement as the X-ray source moves along a path, such as a circular arc, over the breast. In contrast to conventional computed tomography (CT), tomosynthesis is typically bawd on projection images obtained at limited angular displacements of the X-ray source around the breast. Tomosynthesis reduces or eliminates the problems caused by tissue overlap and structure noise present in 2D mammography imaging. Digital breast tomosynthesis also offers the possibility of reduced breast compression, improved diagnostic and screening accuracy, fewer recalls, and 3D lesion localization.
Scattered X-rays generally cause blur and degrade the quality of X-ray images. Anti-scatter grids are typically used in conventional 2D X-ray imaging systems to reduce X-ray scatter by selectively blocking scattered X-rays, such as Compton scattered X-rays, while allowing primary X-rays to reach the X-ray detector. Thus, an anti-scatter grid enhances image quality and tissue contrast by reducing the number of detected X-rays that have been scattered by tissue. While anti-scatter grids have been developed for use in conventional X-ray imaging systems, such as 2D mammography, there is a need for X-ray scatter reducing devices and methods that work with tomosynthesis imaging.
Aspects and embodiments of the present disclosure are directed to providing systems and methods of reducing X-ray scalier for breast imaging, and more particularly for tomosynthesis imaging. Anti-scatter grids and X-ray imaging systems having anti-scatter grids incorporated therein are disclosed. In various embodiments, an X-ray imaging system may have an anti-scatter grid configured according to aspects disclosed herein and may be operable in at least one of a 2D mammography mode and a (3D) tomosynthesis mode. The use of an anti-scatter grid is particularly helpful for imaging a thick breast, for example a heterogeneously dense or an extremely dense breast.
Various aspects, embodiments, and advantages are discussed in detail below. Embodiments disclosed herein may be combined with other embodiments in any manner consistent with al least one of the principles disclosed herein, and references to “an embodiment,” “some embodiments,” “an alternate embodiment,” “various embodiments,” “one embodiment” or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described may be included in at least one embodiment. The appearances of such terms herein are not necessarily all referring to the same embodiment. Features and advantages discussed in connection with any one or more embodiments according to one or more aspects are not intended to be excluded from a similar role in any other embodiment or aspect.
Various aspects of at least one embodiment are discussed below with reference to the accompanying figures, which are not intended to be drawn to scale. The figures are included to provide illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of the disclosure. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every figure. In the figures:
Anti-scatter grids are often used in radiographic imaging to reduce the image degrading effects of scattered radiation on the image. Stationary anti-scatter grids can cause Moire pattern artifacts that are especially troublesome in a digital X-ray detector, for example due to the interference of the anti-scatter grid pattern with the pixel pattern of the X-ray detector. Thus, the resulting image exhibits Moire patterning or grid line artifacts that degrade image quality. Nonlimiting examples of anti-scatter grids for use in radiographic imaging include U.S. Patent Application Publication No. 2012/0170711 and U.S. Pat. Nos. 7,418,076 and 7,715,524, each of which is incorporated by reference herein in their entireties.
Aspects and embodiments of the present disclosure are directed to providing X-ray scatter reducing systems and methods that also allow the reduction or correction of Moire patterns for use in 2D and 3D mammography. In some embodiments, the anti-scatter grid may move relative to the X-ray detector, during X-ray exposure, to blur out Moire patterns. In various embodiments, Moire patterns may also be reduced by using image processing techniques.
According to one aspect of the present disclosure, it is appreciated that motion of the anti-scatter grid presents unique challenges for use in tomosynthesis imaging systems, which have hindered the use of anti-scatter grids for tomosynthesis imaging. For example, the motion of the anti-scatter grid must be synchronized with the X-ray exposure signal. However, in contrast with conventional 2D mammography, tomosynthesis imaging involves obtaining multiple X-ray projection images of the breast, each of the X-ray projection images obtained during a short X-ray exposure time at each of multiple angular displacements of the X-ray source relative to the breast. Therefore, the anti-scatter grid must move a distance effective to reduce Moire patterns during very short time durations corresponding to X-ray exposures of tomosynthesis imaging. Furthermore, tomosynthesis imaging systems typically impose tight spatial constraints on the distance that the anti-scatter grid may move during imaging.
Various aspects and embodiments presented herein address the challenges described above. In various embodiments, an anti-scatter grid includes thin strips, also referred to as septa or laminae. The septa may be made of a radio-opaque material or a highly X-ray absorbing material, such as lead, and may be separated by interspaces. Interspaces may be made of a radiolucent material or a low X-ray attenuating material such as carbon fiber or aluminum. In contrast to conventional anti-scatter grids, embodiments of anti-scatter grids disclosed herein may be configured to be positioned relative to an X-ray imaging device, and more particularly a tomosynthesis imaging device, such that each septum of the anti-scatter grid is oriented lengthwise along an axis that is substantially parallel to the coronal plane of the subject during imaging. In some embodiments, the anti-scatter grid may be configured to move along a direction substantially parallel to a sagittal plane of the subject during imaging. In some embodiments, the anti-scatter grid may have a septa density, also referred to as grid line density, of at least 70 septa per cm, in contrast to conventional anti-scatter grids which typically have septa density in the range of 30 to 50 septa per cm. The various embodiments disclosed herein allow the anti-scatter grid to move a relatively short distance compared to conventional anti-scatter grids, in durations synchronized with the X-ray exposures of tomosynthesis imaging, and in orientations configured to reduce Moire patterns in the resulting images.
It is to be appreciated that embodiments of the methods and apparatuses discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The methods and apparatuses are capable of implementation in other embodiments and of being practiced or of being carried our in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. In particular, acts, elements and features discussed in connection with any one or more embodiments are not intended to be excluded from a similar role in any other embodiment.
Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Any references to embodiments or elements or acts of the systems and methods herein referred to in the singular may also embrace embodiments including a plurality of these elements, and any references in plural to any embodiment or element or act herein may also embrace embodiments including only a singe element. The use herein of “including.” “comprising,” “having,” “containing,” “involving,” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well us additional hems. References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms.
It is to be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements or steps.
Turning now to the drawings,
The tomosynthesis imaging apparatus 102 includes an X-ray source 106, also referred to as an X-ray tube. The X-ray source 106 is configured to deliver an X-ray beam towards the breast of the subject 100 as indicated for example by line 108. In 2D mammography mode, the X-ray source may direct the X-ray beam during an X-ray exposure from a fixed position. In tomosynthesis mode, the X-ray source may move along a path such as an arc above the breast of the subject 100, as illustrated and described further below with reference to
The tomosynthesis imaging apparatus 102 further includes a platform 112 configured to position the breast of the subject 100 between the X-ray source 106 and the X-ray detector 110. The platform 112 is positioned between the X-ray source 106 and the X-ray detector 110 and remains stationary as at least one of the X-ray source and the X-ray detector rotates around the platform during tomosynthesis imaging of the breast of the subject 100. The tomosynthesis imaging apparatus 102 further includes an immobilization structure 114 configured to compress and immobilize the breast for imaging. The breast may be compressed to reduce motion of the subject and also to reduce scatter, separate overlapping structures in the breast, make the thickness of the imaged breast more uniform, and to provide more uniform X-ray exposure. While the platform 112 and the immobilization structure 114 have been described as separate elements with reference to
References to body planes are used herein to describe the orientation and motion of anti-scatter grids. It is to be appreciated that an anti-scatter grid may be fixed relative to the position of an arm of the X-ray imaging apparatus and the anti-scatter grid motion may be described based on the Cartesian coordinates of the arm which may be positioned relative to the body planes.
The tomosynthesis imaging apparatus 102 includes the anti-scatter grid 104 having a plurality of septa 116. The anti-scatter grid 104 has a septa density of at least 70 septa per cm. The anti-scatter grid 104 is positioned between the platform 112 and the X-ray detector 110 and is configured to reduce X-rays scattered by the breast tissue from reaching the X-ray detector 110 during imaging. The anti-scatter grid 104 is positioned relative to the tomosynthesis imaging apparatus 102 such that each septum 116 of the plurality of septa extends along a direction substantially parallel to the coronal plane 126 (or the x-z plane). In an embodiment, the plurality of septa may be exactly parallel to the coronal plane, slightly off-angle to (but generally in the plane of) the coronal plane, or some combination thereof. For purposes of illustration, as an example, the septa closest to the chest wall of the patient may be exactly parallel to the coronal lane while septa farthest from the chest wall may be slightly off-angle to (but generally in the plane of) the coronal plane. In another example, the septa closes to the chest wall of the patient may be slightly off-angle to (but generally in the plane of) the coronal plane while septa farthest from the chest wall may exactly parallel to the coronal plane.
While the X-ray detector 110 may be stationary during some imaging modes, the X-ray detector may move to maintain its orientation towards the X-ray source as the X-ray source moves during tomosynthesis imaging. The motion of the anti-scatter grid 104 may further be coupled to the motion of the X-ray detector 110. For example, the anti-scatter grid 104 may be rigidly attached to the X-ray detector 110. Thus, the anti-scatter grid may move along with the X-ray detector when the X-ray detector moves. For example, during tomosynthesis imaging, the anti-scatter grid may move or rotate with the X-ray detector to maintain its orientation towards a focal spot or the X-ray source 106, while simultaneously moving relative to the X-ray detector to reduce Moire pattern. In various embodiments, the anti-scatter grid 104 may be moving along with the X-ray detector 110 while the septa 116 maintain their orientation along a direction substantially parallel to the coronal plane 126. For example, the X-ray detector 110 along with the anti-scatter grid 104 may rotate around an axis parallel to the y-axis 122 (as shown for example in
The anti-scatter grid 104 is further configured to move along a second direction that is substantially parallel to the coronal plane 126 off the subject 100 during imaging. In various embodiments, the anti-scatter grid may move along at least one of a first direction that is substantially parallel to the sagittal plane of the subject 100 and a second direction that is substantially parallel to the coronal plane 126. For example, motion of the anti-scatter grid along the x-axis in conjunction with motion along the y-axis enables circular and or elliptical motion. In the case where the septa are slightly off parallel with the chest wall (coronal plane), circular motion or elliptical motion may further blur the grid lines and reduce Moire patterns.
The anti-scatter grid 104 may move along a trajectory that allows reducing Moire patterns in the resulting images. The motion trajectory of the anti-scatter grid may be linear, circular or elliptical. Furthermore, the anti-scatter grid 104 may move at a velocity effective to reduce Moire patterns during tomosynthesis imaging. Velocity profiles may minimize velocity variations of anti-scatter grids, thereby reducing grid lines. The velocity profile may be one of a sinusoidal profile and a trapezoidal profile. A sinusoidal profile may simplify the motion algorithm. For example, a rotary motor as shown and described further below with reference to
In some embodiments, the anti-scatter grid 104 may be retractable, either partially or fully, and/or decouplable so that it may be removed from the imaging area between the platform 112 and the X-ray detector 110 and/or the anti-scatter grid 104 can be swapped out for another grid having a different configuration. For example, the anti-scatter grid 104 may be retracted and/or decoupled outside the imaging area for operation in a 2D mammography mode and may be introduced back into the imaging area for operation in the tomosynthesis mode. Additionally and optionally, the anti-scatter grid 104 may be used in 2D mammography mode. Generally, for a multi-mode mammography system, the anti-scatter grid may be in the field of view for one mode, either stationary or moving during an exposure, and/or out of the field of view for another mode, e.g., in 2D mammography mode, magnification mode,, etc. In various embodiments, the anti-scatter grid 104 may be configured according to one or more features disclosed herein, such as features described with reference to
While only a single off-center position of the X-ray source 106 is illustrated in
The systems described herein enable movement of an anti-scatter grid relative to either or both of an X-ray source and an X-ray detector. For example, with reference to
Exemplary systems and structures that enable movement relative to particular planes or axes are described in further detail below. Movement of an anti-scatter grid along certain axes can display particularly desirable results when used in conjunction with tomosynthesis. Although a single motor is depicted in the following examples, multiple motors or actuators may be used in conjunction with an anti-scatter grid to move that element in any direction, as required or desired for a particular application. Additionally, a motor may drive a linkage or other element having multiple degrees of freedom to move the anti-scatter grid as desired relative to any plane or axis defined herein. Gears systems may be utilized to control rates of movement relative to cither or both of the detector and the emitter.
A rotary motor such as the motor 504 of
In one embodiment, the anti-scatter grid 104 of
In various embodiments, the motor (such as the motor 504 of
In some embodiments, the method may further include at least one of immobilizing und compressing the breast of the subject (operation 906), for example using un immobilization or compression structure as shown in
In various embodiments, the method of reducing X-ray scatter may also encompass reducing a Moire pattern in a resulting image. Thus, the method of reducing X-ray scatter may further comprise coupling a motion of the anti-scatter to that of the X-ray detector or emitter (operation 908) such that the anti-scatter grid moves with the X-ray detector or emitter during tomosynthesis imaging. Once coupled, the anti-scatter grid may be moved (operation 910) relative to either or both of the X-ray emitter or detector. In various embodiments, moving the anti-scatter grid may include rotating or translating the anti-scatter grid. In some embodiments, the method may include moving the anti-scatter grid along a first direction that is substantially parallel to a sagittal plane of the subject during tomosynthesis imaging, as shown for example in
In various embodiments, the X-ray imaging apparatus may be an integrated mammography and tomosynthesis apparatus configured to be operable in both 2D and 3D modes. In some embodiments, the method of reducing X-ray scatter may include using the same anti-scatter grid configured according to aspects disclosed herein for imaging in both 2D and 3D modes. In other embodiments the method may include retracting the anti-scatter grid configured according to aspects disclosed herein or switching the anti-scatter grid with a conventional anti-scatter grid for imaging in the 2D mammography mode.
Having described above several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the disclosure. Accordingly, the foregoing description and drawings are by way of example only, and the scope of the disclosure should be determined from proper construction of the appended claims, and their equivalents.