A. Field of Invention
This invention pertains to an ultrasonic scanning apparatus in which a mechanically resonating or vibrating member resembling a tuning fork supports an probe generating ultrasonic sound waves and detecting the resulting waves reflected from a target. The apparatus is particularly applicable for medical scanners used for imaging organs such as the eye of a patient.
B. Background of the Invention
Ultrasonic imaging refers to an apparatus that makes use of an ultrasonic probe which repeatedly emits pulses of high-frequency sound at a target as the probe is pivoted about an axis. The apparatus further includes a receiver that receives the resulting echo signals from the target. The received echo signals are electronically synchronized to the movement of the probes and processed and resulting signals are converted into a visual image or some other representation indicating various characteristics of the subject tissues. The apparatus is particularly useful for generating images of human organs and tissues and is used extensively for imaging a patient's eye.
Several techniques have been used for generating a sweeping sound for scanning the target, however, by and large these techniques use one of two main approaches that are in common use: a mechanical and an electronic approach. The mechanical approach includes a probe that generates a single ultrasonic beam. The probe is mounted on the end of an arm or similar mechanical member. The arm is supported by a hinge at the opposite end and is pivoted around the hinge in a reciprocating angular motion thereby causing the ultrasonic beam from the probe to sweep across and scan the target. This approach has several problems related to the fact that it is difficult to track or predict the movement/position of the probe accurately. Hence the resulting image may have some inherent errors.
The electronic approach uses a probe formed of a plurality of ultrasonic transducers arranged in an array. The electronic approach generally provides greater speed, precision and repeatability of sound beam motion than the mechanical approach. However, the array approach is inherently more expensive than the mechanical approach. In other words the electronic probe array provides greater accuracy but at a higher price.
As discussed above, in a typical ultrasonic scanner using the mechanical approach, the probe is mounted on a pivoting arm. An illustrative arrangement is illustrated in the above-identified application Ser. No. 12/046,681 filed Mar. 12, 2008 and Ser. No. 12/117,039 filed May 8, 2008, wherein the pivoting arm is reciprocated actively through a preselected arc. In the present invention, instead of pivoting arm, a cantilevered plate is used as a means of providing a reciprocating motion for the probe. The plate is made of a high quality steel or other similar material that has well known inherent resilient characteristics that provide it with a natural resonant mode similar to a tuning fork. The plate is fixed at one end while the probe is preferably mounted on the opposite end. Because of its resiliency, the plate has a natural frequency of resonance and therefore once it is displaced and released, the bar resonances angularly at its natural frequency for a long time even if it is not excited. In the present invention, an excitation device is provided to insure that the bar resonates at sufficient amplitude for the purposes of the subject device. The natural frequency of vibration of the plate is determined by the dimensions of the plate, the materials used to make the plate. Moreover, any other foreign elements mounted on the bar will affect its natural resonant frequency as well.
A tuning fork is formed of two opposed arms that resonate in opposite directions. This structure is replicated in the present invention by providing a counterbalancing arm constructed and arranged so that the arm and the plate form a resonant assembly with the tips or ends of the bar and the plate resonating simultaneously in opposite directions. While typically the arms of a tuning fork have identical dimensions (or, more properly, they are identical mirror images of each other), in the present invention, the bar and the plate need not be identical as long as their resonant characteristics are matching. In a preferred embodiment, the plate is formed with an elongated cutout or window and the counterbalancing bar is disposed in the window and affixed near the base of the plate.
As mentioned above, the present invention provides an ultrasonic device in which the mechanical vibrator uses a tuning-fork type resonating assembly. A preferred embodiment of the invention is shown in
As shown in
The plate 12 can be excited using various means. In one embodiment, an electromagnetic coil 20 is mounted adjacent to the plate 12 and the plate is either made of a ferromagnetic material or is provided with a ferromagnetic element 12A adjacent the coil 20. An electronic control circuit 22 provides excitation signals to the electromagnetic coil 20 that cause the plate 12 to vibrate at its resonant frequency F and predetermined amplitude A thereby reciprocating the probe 16 as discussed. Although it is possible to vibrate the plate 12 at various frequency, exciting the plate 12 to vibrate at its natural frequency F is very advantageous because it can be performed using only a small amount of energy. Moreover, the motion of the plate 12 and probe 16 are well known and therefore the position of the probe 16 can be tracked very easily. As previously discussed, it is important that the position of the probe 16 during the scanning of target T is important so that the readings obtained by the probe can be properly correlated with respective characteristics of the target T.
Therefore, if necessary, a sensor 24 may also be positioned adjacent to the plate 12 to determine the position of end 18 very carefully and to transmit this position to the control circuit 22. For example, the sensor 24 may be a Hall effect sensor used to sense a magnet 24A on the plate 12.
The device 10 may be implemented only with a plate 14 as the vibrating member. However, it may be advantageous to provide a counterbalancing bar for the device to counteract the vibration of plate 12. Therefore, in one embodiment, the plate 12 is formed with an opening or cutout 13 by making a U-shaped cut to form a secondary element or beam 30. The beam 30 can be formed so that when the plate is at rest, the beam 30 and plate 12 are co-planar. Alternatively, the beam 30 is bent so that it is disposed at a predetermined angle with respect to the plate 12.
The beam 30 acts as a counterbalancing bar to plate 12 and is attached to the plate 12 near end 14 as shown. The beam 30 and the plate 12 cooperate to define a vibrating system similar to a tuning fork with the ends of the beam 30 and plate 12 resonating in opposite directions simultaneously. Since the plate 12 and beam 30 have different shapes and sizes, the beam 30 is preferably shaped, sized and, if necessary, provided with additional weights to insure that it has the same mechanical and dynamic characteristics as plate 12 and therefore the two elements cooperate just like the two legs or tines of a tuning fork, with the plate 12 vibrating with its tip describing an arc A while the bar 30 describes an arc B with its tip. The resonant frequency of the resulting assembly, F, is in the same range as the frequency used in standard devices to reciprocate the probe. Typically, this frequency is in the range of 12-15 HZ.
In the embodiment with a composite resonating composite body composed of plate 12 and beam 30, an exciting means must also be provided to start and maintain the resonant state. This excitation may be provided by a single coil exciting the plate 12, this excitation being then automatically transferred to the bar 30. Alternatively the composite body is excited by a coil 32 acting on bar 30. In yet another embodiment, two coils 20, 32 are used. In all these cases, excitation signals are received from the controller 22. Preferably, the main plate 12 and the beam 30 are driven at the same frequency but out of phase by 180 degrees so that the net vibration of apparatus becomes negligible. As a result, when the apparatus is used, the vibration or shaking of the plate 12 is eliminated by the vibration of beam 30 and the end result is that the apparatus holding probe assembly shown in the figure experiences only at most a negligible shake or vibration.
In an alternate embodiment shown in
Returning to
In the drawing the plate 12 and beam 30 have a specific shape and configuration, However it should be understood that these elements can have other shapes as well.
Typically, an ultrasonic device 70 includes, as shown in
Numerous modifications may be made to the invention without departing from the scope of the invention as defined in the appended claims.
This application claims priority to U.S. Provisional Application Ser. No. 61/147,057 filed Feb. 2, 2009, incorporated herein by reference. The subject matter of this application is related to the subject matter of application Ser. No. 12/046,681 filed Mar. 12, 2008 and Ser. No. 12/117,039 filed May 8, 2008, both incorporated by reference in their entirety.
Number | Date | Country | |
---|---|---|---|
61149057 | Feb 2009 | US |