Source: http://www.google.com/patents/US6157703
Timestamp: 2014-03-07 23:28:21
Document Index: 524670491

Matched Legal Cases: ['arts 410', 'art 410', 'arts 420', 'art 420', 'arts 410', 'art 420', 'arts 410']

Patent US6157703 - Beam hardening filter for x-ray source - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsAn x-ray beam hardening filter is disclosed. The x-ray beam hardening filter comprises a support member and a beam hardening sheet, the beam hardening sheet having a multidimensional array of regularly spaced apertures. The apertures are configured to have an x-ray transmissive quality. An actuator,...http://www.google.com/patents/US6157703?utm_source=gb-gplus-sharePatent US6157703 - Beam hardening filter for x-ray sourceAdvanced Patent SearchPublication numberUS6157703 APublication typeGrantApplication numberUS 09/167,639Publication dateDec 5, 2000Filing dateOct 6, 1998Priority dateOct 6, 1998Fee statusPaidPublication number09167639, 167639, US 6157703 A, US 6157703A, US-A-6157703, US6157703 A, US6157703AInventorsGiovanni Pastrone, Edward G. SolomonOriginal AssigneeCardiac Mariners, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (36), Non-Patent Citations (4), Referenced by (9), Classifications (6), Legal Events (11) External Links: USPTO, USPTO Assignment, EspacenetBeam hardening filter for x-ray sourceUS 6157703 AAbstract An x-ray beam hardening filter is disclosed. The x-ray beam hardening filter comprises a support member and a beam hardening sheet, the beam hardening sheet having a multidimensional array of regularly spaced apertures. The apertures are configured to have an x-ray transmissive quality. An actuator, engaging the support member, is capable of moving the multidimensional array of apertures into or out of a path of an x-ray beam, thereby selectively introducing varying levels of x-ray energy filtration. In one embodiment, multiple layers of beam hardening sheets are added to the x-ray beam hardening filter to create additional levels of x-ray energy filtration. Advantages of the x-ray beam hardening filter include the relatively small distance the x-ray beam hardening filter must move in order to absorb the incident x-ray beam, the ability to introduce varying levels of x-ray filtration, and the compact structure of the x-ray beam hardening filter.
According to a preferred embodiment, an arrangement of varying levels of x-ray radiation is accomplished via a multidimensional array of apertures 130 which are disposed about the surface area of the beam hardening sheet 120. The array of apertures 130 are chemically etched into the surface of the beam hardening sheet 120 at regularly spaced intervals with a hole pitch of A.sub.p. Each aperture 130 has a diameter A.sub.d. Each aperture 130 is preferably no closer than to any other aperture than a distance approximately equal to diameter A.sub.d. The apertures 130 are configured to allow x-ray photons to freely pass through them, whereas other areas of the beam hardening sheet 120 (that is, without apertures 130) are configured to absorb some of the x-ray photons incident thereon.
The support member 110 comprises a receiver. According to one embodiment, the receiver is a rectangular aperture 160. Within rectangular aperture 160, a cam 140, having a diameter C.sub.d, is at least partially enclosed. The cam 140 rotates within rectangular aperture 160 based upon external control of a motor (not shown). The cam 140 is mounted to a cam shaft (not shown) at a rotation location 150. The rotation location 150 is offset from a center point of the rectangular aperture 160 a distance approximately equal to one-quarter of the aperture 130 pitch A.sub.p. The rectangular aperture 160, it may be noted, has a major axis with a length of approximately twice the distance between the rotation location 150 and an outer most point on cam 140, and a minor axis approximately equal to the cam 140 diameter C.sub.d.
FIG. 4A depicts a top view of a cam bearing 400. The cam bearing 400 has an outer diameter (CBO.sub.d) 402 and an inner diameter (CBI.sub.d) 404. According to one embodiment, the outer diameter 402 is larger than the minor axis of the rectangular aperture 160, whereas the inner diameter 404 is smaller than the minor axis of the rectangular aperture 160.
FIG. 4B depicts a side view of the cam bearing 400. Viewed from the side, cam bearing 400 essentially comprises three washer-shaped body parts 410, 420 and 430. Part 410 has is relatively thin (e.g., 0.010 inches), whereas parts 420 and 430 are relatively thick (e.g., 0.040 inches). Part 420 is configured to be at least thick enough such that support member 110 can slide between parts 410 and 430. In such an embodiment, the rectangular aperture 160 is modified to have not only the rectangular aperture 160 described above, but also a bulbous end extending from one side, the bulbous end creating an opening at least sufficiently large to pass the outer diameter (CBO.sub.d) 402 through it. The rectangular aperture 160 has a minor axis approximately equal to the diameter of part 420, but smaller than the diameter (CBO.sub.d) 402. Accordingly, the support member 110 is capable of dropping over the cam bearing 400 so that the bulbous end surrounds the cam bearing 400. The support member 110 is then slid from the bulbous end and toward the rectangular aperture 160 until it comes to rest within the cavity created by parts 410, 420 and 430. Alignment of the support member 110 is finalized with direction guides 170.
FIGS. 5A-C depict a cam-filter control 500. The cam-filter control 500 comprises a cam 530 and a position plate 510. An inner diameter 520 of the cam-filter control 500 is configured to slide over the cam shaft 220. Furthermore, the cam 530 and the position plate 510 are attached together such that the outermost point 532 (relative to rotation location 150) on the cam 530 is aligned to a point approximately 10 the midpoint of the outer diameter of the position plate 510. The position plate 510 is substantially similar to the position plate 310, described above, the primary difference being it is secured to the cam 530 to form the cam-filter control 500.
If n beam hardening sheets are used in the x-ray beam hardening filter 600, then one or more actuators are preferably capable of moving the beam hardening sheets (e.g., 610 and 620) in 2.sup.n different positions. For example, if four beam hardening sheets are employed, as many as four actuators can be used and 2.sup.4 (16) different positions of the four beam hardening sheets are possible. Different configurations of the actuators can accomplish such a positioning either by varying the cam shape or, simply by individually controlling each motor and cam.
According to a preferred embodiment, beam hardening sheet 610 absorbs twice the x-ray energy of beam hardening sheet 620. Doubling the absorption quality of each successive beam hardening sheet added to the filter, while employing actuators capable of 2.sup.n positioning gives a high degree of control and selectivity of the x-ray beam hardening filter 600.