This patent application claims priority from united states provisional patent application No. 60/874,654, filed 2006, 12, 13, which is hereby incorporated by reference in its entirety. This patent application also claims priority from U.S. provisional patent application No. 60/875,088, filed 2006, 12, 15, which is hereby incorporated by reference in its entirety.
Background
In recent years, ultrasound has received attention as a non-invasive bone assessment technique. Many efforts have been made to use ultrasonic energy to estimate bone tissue status in vivo as a metric for the diagnosis of osteoporosis and fracture risk assessment.
Of particular note, Hoop in U.S. Pat. No. 3,847,141 discloses an instrument for monitoring the calcium content of bone by measuring bone density. A pair of ultrasonic sensors are arranged on the opposite sides of the measured finger in a face-to-face manner, the transmitting sensor is aligned with the finger bone to repeatedly transmit pulses, and the opposite receiving sensor is also aligned with the finger bone to receive the pulses passing through the bone. The loop is designed such that the filtered acceptance signal triggers the transmission of the next pulse; the filtering adopts a band-pass filter, and only the received signal components within the range of 25kHz to 125kHz pass through the band-pass filter; hoop believes that the observed trigger frequency is proportional to the calcium content of the bone. So that he can take measurements as long as he considers the pulse transit time in this given band.
Pratt, jr. study bone strength in living organisms, such as horses. In the us patent (No. 4,361,154), the inventor has solved a problem whereby the transit time of 0.5MHz and 1.0MHz pulse signals through bone and soft tissue, and also the transit time of pulse-echo, and hence the transit time of signals through bone-only parts, can be determined. With the aid of a database he can assess the bone condition by determining the transit time. Another U.S. patent to Pratt, jr (serial No. 4,913,157) uses the same time of flight/velocity inference principle, using the latter optimum frequency of 2.25MHz as the transmit fundamental frequency, and further processes the pulse signal using a matched technique of filtering/fourier transform filtering.
A bone measurement system is disclosed in united states patent number 4,774,959 to Palmer et al. The system uses a series of signals of different frequencies to determine the slope of the attenuation as a function of frequency. Signals with frequencies of 200kHz to 600kHz are emitted by one sensor and received by the other sensor. Assuming that the attenuation versus frequency relationship is linear, i.e., assuming that the slope is constant, the desired result is determined by comparing the signals that pass through the heel bone and do not pass through the heel bone.
Another biological in vivo bone analysis system is disclosed in U.S. patent (No. 4,926,870) owned by Brandenburger. The system measures the transit time of the ultrasound signal through the bone along the desired path. The "canonical" waveform of the signal after traversing the correct path is derived from past experience. In determining the patient's bone, the orientation of the transducer is adjusted until the received signal waveform appears to conform to the "canonical" waveform, i.e., the desired path has been found. The measured transit time is used to determine the speed of the ultrasound waves through the patient's bone.
Rossman et al, in U.S. patent No. 5,054,490, disclose an ultrasonic densitometer that measures the physical properties and integrity of bone by measuring transit time. In yet another method, the Rossman et al instrument measures the absolute attenuation of an ultrasound signal at a particular frequency through bone and compares the absolute attenuation with the absolute attenuation of the same frequency signal component through a medium of known acoustic properties to analyze bone properties and integrity.
An instrument is disclosed by Mele et al in U.S. patent No. 5,564,423 and later by Cadossi et al in U.S. patent No. 6,436,042. It measures the wave velocity of ultrasonic waves through a bone-containing portion of a living body in relation to the amplitude. The method displays the received ultrasonic signals on a screen, and visually selects a specific waveform part for analysis.
Kaufman et al (U.S. patent nos. 5,259,384 and 5,651,363) and Chiabrera et al (U.S. patent nos. 5,785,656 and 5,879,301) made significant advances in ultrasonic bone assessment. In these patents, the "bone transfer function" of a given bone is estimated by statistical optimization, and the corresponding phase and attenuation functions are parameterized. These patents also describe the use of two-dimensional sensor arrays to obtain more reproducible estimates of bone density, structure and fracture risk.
Although the above-mentioned devices and methods are an advance over the prior art, further improvements to the prior art are necessary to more accurately assess the bone density, structure, quality and fracture risk of the subject. This enables the ultrasound technique to be widely used for accurate assessment of bone density, structure, quality, fracture diagnosis and fracture risk.
Disclosure of Invention
It is a primary object of the present invention to provide an improved method and apparatus for non-invasively determining properties of bone. A more specific but not limiting object is to provide a method and apparatus for non-invasive quantitative assessment of bone tissue in vivo, thereby making it possible to accurately diagnose and monitor osteoporosis.
To achieve the stated object, it is another object of the present invention to provide a more convenient and reliable way to assess bone tissue condition and diagnose osteoporosis than previously used measurement approaches.
A further object is to provide a simpler and less expensive approach to bone tissue assessment and osteoporosis diagnosis relative to previously disclosed measurement approaches.
It is yet a further object to locate a region of interest in the calcaneus, the size of which can be adjusted to suit different subjects, to make osteoporosis assessments clinically meaningful while maintaining excellent repeatability.
Compared with the prior art, the invention adopts a new method to reliably and repeatedly position the region of interest of the research object, thereby realizing the aim. More specifically, in the present invention, a pair of ultrasonic sensors is moved a certain distance along a certain angle. The distance is determined in dependence on the size of a part of the body of the subject.
Accordingly, the present invention employs a novel structure for determining a region of interest in the calcaneus of a living organism, and thus more accurately determining characteristics of the calcaneus, to thereby determine one or more bone properties, such as fracture risk, strength, density, quality and structure. This has the advantage of being simple, convenient and more sensitive to the measured bone condition. In contrast, previous techniques have not been able to obtain so much information in such a convenient and efficient manner.
The preferred form of the method and apparatus of the present invention for determining and locating a region of interest in the calcaneus bone is the repeatable placement of a pair of coaxially mounted ultrasonic transducers, depending on the size of a given subject's anatomy. The previous exemplary approach has been to use a fixed region of interest. An example of such a fixed region of interest is the fixation of an ultrasound sensor on a support on which the subject's foot is placed. This method is good in terms of reproducibility per se, but has the drawback that different parts of the calcaneus bone are measured for different subjects, making the measurements poorly comparable. This is due to the high heterogeneity of the calcaneus (i.e., different regions in the same calcaneus have very different bone densities, cortical bone thicknesses, and cancellous bone structures), while the size of the calcaneus varies from person to person. Therefore, for a fixed position sensor instrument, such as fixed to the back of the foot for a certain distance, the calcaneus bone measured by different persons will often be very different, so it is difficult to make a meaningful comparison of the measurements of different persons. Another approach that has been discussed is to use a two-dimensional array. While this approach sounds to emphasize the problem of "fixed region of interest," such systems tend to be very complex and expensive.
The present inventors have identified several key points in the development of a device and method for non-array ultrasound evaluation of the calcaneus bone that provides both good repeatability and ensures that relatively consistent regions of interest are measured for different individuals. First, and most importantly, the size of the calcaneus bone is closely related to the overall size of the foot. Other important observations are that the main region of interest is the posterior part of the calcaneus (as measured by an X-ray absorption gauge). Also, the mean value of this region of interest is at a fixed angle to the horizontal (conclusions from the comparison of photographs of the general electric apparatus LunarPIXI dual-energy X-ray bone densitometer of numerous subjects with photographs of the feet of normal X-rays).
In the preferred embodiment of the invention, and with reference to FIG. 1, a foot is placed on a horizontal surface of a positioning device and the rear end of the heel abuts against a vertical surface on the rear of the positioning device. A mechanical positioning device clamps a pair of sensors and is arranged coaxially in a face-to-face manner to face the medial and lateral sides of the heel of the subject. A threaded rod is driven by the handle to move the finger bell to the first metatarsal head (i.e., the medial protrusion of the anterior portion of the sole). The threaded rod is in turn connected to the sensor positioning device via a rack and pinion, so that the sensor is moved along a fixed angle by a distance proportional to the distance from the rear end of the heel to the first metatarsal head. In the preferred embodiment, this fixed angle is 50 degrees and the proportionality constant, α, for the sensor movement along this angle is 15/66, about 0.23. In a preferred embodiment, the reference point for the sensor is the angle of intersection of the horizontal and vertical planes of the positioning device. It should be understood, however, that any convenient location may be used as a reference point and is within the scope of the present invention.
Detailed Description
The invention shown in fig. 1 is used to implement the method of the invention to locate a region of interest of a calcaneus bone of a living subject. More specifically, it is a method for locating a region of interest of the calcaneus bone in a living organism for non-invasive quantitative bone state assessment by obtaining one or more of the quantifications at a given time: bone density, structure, quality, strength, and fracture risk. In general, the components used in the present apparatus are commercially available in a variety of forms, and will be described in the following detailed description of the apparatus as a whole.
Referring to figure 1, a calcaneus bone (not shown) for in vivo analysis is located within the heel [12] of a subject's foot [10], surrounded by soft tissue and outer skin [14 ]. The heel [12] is located between two coaxially oppositely mounted and acoustically coupled ultrasonic transducers [16] and [18] (located behind the foot [10 ]). The two sensors may be identical and are commercially available from Valpey-Fisher Corp, Inc., located in the United States of Mars, Hopkinton, Mass., United States. As shown, the sensor [16] is used for signal transmission, and the sensor [18] is used for receiving signals transmitted through the heel [12] (its superficial skin, surrounding soft tissues, and the heel bone itself).
As can be seen in fig. 1, the subject's foot [10] is placed on the positioning device [20 ]. The positioning device has a surface [22] on which the foot rests. The positioning device has a surface [24] against which the rear end of the heel rests. The arrangement shown in fig. 1 also implies the selection of a proportionality constant and an angle. The proportionality constant, α, is the linear distance (based on a reference point) that a pair of ultrasonic transducers moves along an angle divided by a certain length of the subject's foot. In the preferred embodiment of the invention, the length of the subject foot is the distance from the heel to the first metatarsal head. Referring to fig. 1, the location of the first metatarsal head is indicated by pointer [30 ].
Therefore, in the preferred embodiment of the invention, the foot [10] is placed on the horizontal surface [22] of the positioning device [20] with the heel resting on a vertical surface [24] thereof. The positioning device [20] includes a member for holding the sensors [16] [18] coaxially and facing the medial and lateral sides of the subject's heel [12], respectively. A threaded rod (under the horizontal portion [22], 44 in FIG. 2) is moved by the handle [32] to move the finger-bell [30] (46 in FIG. 2) to the first metatarsal head. The threaded rod is in turn connected to the sensor holder by a set of racks and gears (two and four in the preferred embodiment, see fig. 2 and three), so that the sensor is moved along a selected angle, θ, a distance proportional to the distance from the rear end of the heel to the first metatarsal head. Referring again to FIG. 2, rotation of the threaded rod [44] causes linear movement of the first rack [48] (on which the finger clock [46] is mounted). Referring again to fig. 3, the first rack [48] (shown in phantom) rotates a set of (4) gears. A first gear [50] is engaged with the first rack. The second gear [51] transmits rotation to the third gear [52] and reverses direction. The third gear [52] and the fourth gear [53] are fixed on the same shaft. The fourth gear [53] is engaged with the second rack [60] to move the sensor-mounted slider (element [36] in fig. 1) along the inclined surface. In the preferred embodiment of the invention, this predetermined proportionality constant, α, is achieved by selecting the gear ratio of gears [53] and [52 ]. The gear ratio selected in this embodiment is 15/66 to achieve the predetermined movement to locate the region of interest.
Thus, in the preferred embodiment and referring to FIG. 4, the angle θ selected is 50 degrees and the proportionality constant, α, which is the ratio of the distance the sensor travels from the reference point along the predetermined 50 degree slope to the distance from the heel end of the foot under test to the first metatarsal head is 15/66, about 0.23. Thus, if the heel-to-first metatarsal head distance is 180 millimeters, the sensor moves linearly from the reference point along a 50 degree slope by 0.23 × 180 — 41 millimeters. In the preferred embodiment, the sensor reference point [60] is the intersection of the horizontal [22] and vertical [24] portions of the positioning device near the heel. It should be understood that any convenient location may be used as a reference point and remain within the scope of this invention. It will be appreciated that this procedure allows for repeatable positioning of the sensor (1) over the calcaneus bone and (2) in a position that allows meaningful comparisons of bone properties measured from different subjects. These two points are key to making the invention disclosed herein useful for non-invasive ultrasound bone assessment to achieve the stated goals. As shown in FIG. 4, the reference point in this preferred embodiment is the intersection [61] of the horizontal and vertical portions of the positioning device, which is marked in large black dots. The 'x' 62 in the figure marks the determined center of the region of interest, to which the center of the ultrasonic sensor is to be aligned. The distance from the center of the region of interest to the reference point, d, is equal to alpha L, wherein alpha is a proportionality constant, and L is the size of the relevant part of the human body; in the preferred embodiment, α is 0.23 and L is the distance from the heel end to the first metatarsal head. It is noted that the reference point [61] in this embodiment, such as the large black dot in FIG. 4, may be understood as the origin of the reference coordinate, with the x-axis along the sole and the y-axis along the posterior end of the foot, as shown in FIG. 4. Note that the Parts used in the preferred embodiment of the present invention may be purchased from commercial sources (e.g., Small Parts, Inc. of Miami Lakes, Florida, USA, Fla, USA, U.S.) or manufactured by machining companies (e.g., Queen Screen and Manufacturing, Inc., Waltham, Massachusetts, USA, U.S.A.).
Note that in the preferred embodiment of the invention, the foot size measurement is taken as the distance from the heel end to the first metatarsal head. It is to be understood that the invention encompasses the use of a variety of foot size measurements, such as the distance from the heel to either toe, or some form of averaging of a set of such size measurements. Also, for example, the distance from the heel to any point on the ball line (the line connecting the first metatarsal head to the fifth metatarsal head) can be used. It should therefore be understood that any foot size measurement is within the scope of the present invention. It is also understood that foot size measurements include any foot, ankle anatomical dimension, such as the heel base to ankle distance. It will of course be appreciated that different foot size measurements may be used and the proportion of movement and corresponding relationship of the corresponding sensors adjusted. The distance from the heel end to the first metatarsal head is used in this embodiment because this position facilitates positioning and because of potential errors in positioning the toes.
Further, it should be understood that different angles (50 degrees selected in this embodiment) may be used in the present invention. It will be appreciated that different angles will position the ultrasound transducer at different regions of interest in the calcaneus bone. These different regions of interest may be used to assess different properties of bone, for example in the study of osteoporosis. For example, one region of interest may be used to assess changes in bone density, while another region of interest may better monitor the effectiveness of treatment at fracture risk. It should also be appreciated that varying the angles and proportionality constants described may achieve similar but different results. Such as monitoring another portion of the calcaneus bone or incorporating other information to optimize the position of the sensor. These methods are also understood to be within the scope of the present invention.
The invention shown in the preferred embodiment (see fig. 1 to three) uses the rotation of the handle to drive a threaded round bar, in conjunction with a set of racks and gears to achieve the desired movement and ultimately the positioning of the sensor. However, it should be understood that any mechanical device, whether employing gears, whether manual, spring powered, or electrically controlled, is understood to be within the scope of the present invention. It should also be understood that while the present embodiment employs a fixed ratio of x and y motion (thereby forming a fixed angle), it should be understood that the present invention encompasses the use of sensor position coordinates x and y as a function of a non-linear relationship that is a variable in length. This may be advantageous in conjunction with other new information that may be available to locate the region of interest. For example, the subject's feet may be very large or very small, and may be anatomically different between men and women.
In a further embodiment of the invention, a length that is not necessarily associated with the foot may be used to locate the region of interest of the calcaneus bone. For example, the height of a person may be used. Furthermore, in this alternative embodiment, the size of the bony portions of a group (at least one) of the subjects can be used to determine a region of interest in the calcaneus bone. In general, the set of lengths can be used to independently determine the x and y coordinates of the center of interest. This can be expressed by the following equation:
x＝f(L1，L2，L3，...，LN)
y＝g(L1，L2，L3，...，LN)
where x and y are the position coordinates of the region of interest relative to a reference point, L1, L2, L3. For example, let L1 be the height and L2 be the length of the heel to forefoot line, then a preferred embodiment of the present invention is:
x＝a*L1
y＝b*L2
it can be seen from this embodiment that the variables of the x and y coordinate functions do not necessarily have to be the same size for a part of the body. It should be understood that the present invention encompasses the use of multiple sizes and size combinations to define the region of interest designated by x and y. It should also be understood that the functions f and g may be linear or non-linear, or one linear and the other non-linear. Please note that a frame of reference must be selected to determine the x and y positions.
It will also be appreciated that the center of the region of interest location is specified by coordinates (x, y) relative to a reference frame, the center being a distance d from the origin of the reference frame. It will be appreciated, however, that the actual distance moved by the sensor is often not the distance d, since the starting position of the sensor is typically not the origin.
It will further be appreciated that in an alternative embodiment of the invention, the locating means does not have a vertical portion, but only a reference mark is made on the horizontal portion, i.e. the locating means has only one face on which the sole of the foot is placed. It will also be appreciated that this said "horizontal" portion does not necessarily have to coincide with a true horizontal plane, since the positioning device may be placed at an angle, for example 30 degrees, for the sake of comfort for the subject. It is also believed that the "vertical" portion of the positioning device used to position the heel need not be truly vertical, as the positioning device itself may tilt. Furthermore, the horizontal surface on which the foot is placed need not be flat, as in some embodiments it may be necessary to raise or lower the height of the heel (relative to the ball of the foot).
Thus disclosed herein is a method for locating a region of interest in the calcaneus bone of a subject's foot, comprising the steps of:
a. placing a subject's foot on a positioning device, said positioning device having a surface on which the bottom of said foot rests, said positioning device having a further surface against which the heel of said foot rests;
b. selecting a proportionality constant, an angle and a reference frame;
c. determining a size of the subject's foot;
d. a pair of ultrasonic transducers are mounted on each of the medial and lateral sides of the heel portion of the foot by moving the transducers in the frame of reference along the angle by a distance equal to the product of the proportionality constant and the dimension.
Thereby locating a region of interest of the calcaneus bone.
A method for locating a region of interest in the calcaneus bone of a subject's foot, comprising the steps of:
a. placing the subject's foot on a positioning device, said positioning device having a surface on which the bottom of said foot rests, said positioning device having another surface against which the heel of said foot rests;
b. respectively selecting x and y motion function formulas, and moving a pair of ultrasonic sensors according to the function formulas;
c. selecting a frame of reference and determining the size of at least one body part in said subject;
d. the pair of ultrasonic transducers are mounted on both the medial and lateral sides of the foot by positioning the transducers as a function of the motion to locate a region of interest of the calcaneus bone.
An apparatus for locating a region of interest in the calcaneus bone of a subject's foot, the apparatus comprising:
a positioning device having at least one surface and at least one ultrasonic sensor, said positioning device further comprising means for moving said at least one ultrasonic sensor according to a set of motion functions. Means are also included in the set of motion functions for using the size of at least one location in the subject. Means are also included in the positioning device to establish a frame of reference whereby the region of interest of the calcaneus bone in the foot of the subject is positioned.
It should be understood that the present invention does not necessarily require direct measurement of a part of the body. In the preferred embodiment, and with reference to FIG. 1, the handle [32] is used to adjust the pointer [30] to align with the first metatarsal head of the foot, while also moving the sensor [16] [18] to the desired calcaneus bone region of interest. In other embodiments, explicit use of the length of a body part (e.g., height) may require direct measurement and utilization. Both embodiments (i.e., with or without explicit measurement of the size of the selected body part) are understood to be within the scope of the present invention. Also, embodiments employing both methods (i.e., with or without explicit measurement of the size of the selected body part) should be understood to be within the scope of the present invention.
It should also be understood that the present invention may be employed with two distinct sensor configurations. The first is to place two sensors on opposite sides of the subject's heel to create a transmissive transmission state. The second is to constitute a pulse echo state by one sensor. In both cases, it will be appreciated that the method and apparatus of the present invention are capable of locating a desired region of interest in the calcaneus bone. It is further understood that both transmissive transmission and pulse echo states can be used in the method and apparatus of the present invention.
It is further understood that the techniques disclosed herein may be combined with any number of ultrasound signal processing methods and parameters. Thus, it is understood that any combination of ultrasonic parameters may be used in conjunction with the methods and apparatus of the present invention. Particularly the methods and apparatus disclosed in U.S. patent nos. 5,259,384, 5,651,363, 5,785,656 and 5,879,301, and U.S. patent application No. 20050197576, which are incorporated herein by reference in their entirety, are to be understood as being suitable for use in the present invention.
It should be appreciated that the method and apparatus disclosed herein for locating a region of interest in the calcaneus of a subject may be used not only with ultrasound, but also with other techniques, such as with an X-ray bone densitometer. For example, in this application, the thickness of a heel region of interest located using the methods disclosed herein may be measured. In this alternative embodiment of the invention, no ultrasonic sensor is employed. Thus disclosed herein is
A method for locating a region of interest in the calcaneus bone of a subject's foot, comprising the steps of:
a. placing the subject's foot on a positioning device, said positioning device having a surface on which the bottom of said foot is placed, said surface having a reference mark thereon for locating the placement of said foot;
b. selecting a motion function of x and y in a reference system and determining the size of at least one part of the body of the subject;
thereby locating a region of interest of the calcaneus of the subject.
It will be further appreciated that the overall width measurement of the heel taken at the identified region of interest has a variety of different uses, including but not limited to ultrasound bone assessment and X-ray bone assessment. It should therefore be appreciated that an alternative embodiment of the present invention not only locates this region of interest but also measures the heel width at this location.
It should be noted that the (x, y) coordinates disclosed above generally correspond to the center of the region of interest. This region of interest may be of various shapes, such as a circle or square. It should be understood that there are many options for the shape of the region of interest (e.g., triangular or trapezoidal, etc.), and that the (x, y) coordinate location may be selected at the center of the region of interest, as well as other locations of the region of interest, and all such embodiments are contemplated as falling within the scope of the present invention. In the preferred embodiment of the invention, the region of interest is circular and the (x, y) coordinate is located at the geometric center of the circular region of interest.
The invention described herein achieves the primary objective of the inventors, primarily to locate a region of interest that is valuable for clinical osteoporosis assessment, and to adjust the region of interest to the size of the calcaneus of the subject to maintain the relative position of the region of interest, while ensuring excellent repeatability. While various embodiments of the present invention have been disclosed, it should be understood that the invention is not limited to those embodiments. Numerous modifications and additions may be made to the preferred embodiment exemplifying the invention by those skilled in the art without departing from the spirit and scope of the present invention as defined in the appended claims. It is therefore to be understood that the patent protection claimed and provided herein is to be considered as extending to the claimed subject matter and that all equivalents thereof are fully within the scope of this invention.