Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-09-29
2002-09-10
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S425000, C382S128000, C382S132000, C382S280000, C382S286000, C378S042000, C128S922000
Reexamination Certificate
active
06449502
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a bone measurement method and apparatus. This invention particularly relates to a method and apparatus for acquiring a quantitative index value, which represents a condition of a structure of a bone tissue of a human body, or the like, the condition being useful in making a diagnosis of osteoporosis, or the like, in accordance with a radiation image.
2. Description of the Prior Art
Bone mineral analysis, i.e., quantitative determination of amounts of calcium in bones, is useful for making a diagnosis for preventing fractures of bones.
Specifically, the amounts of the bone mineral are determined by the density of bone trabeculae, which are the cancellous matter constituting the internal regions of bones, i.e. the bone density. Therefore, if the bone density is low, the image density of a bone pattern in a bone image will become high. If the bone density is high, the image density of the bone pattern in the bone image will become low.
Therefore, by investigating small changes in the amounts of calcium contained in bones, osteoporosis can be found early, and fractures of the bones can be prevented.
Various techniques for bone mineral analysis have been proposed and used in practice. Such techniques include microdensitometry (MD technique), single photon absorptiometry (SPA technique), dual photon absorptiometry (DPA technique), quantitative digited radiography (QDR technique), quantitative computer tomography (DQCT technique), and dual energy quantitative computer tomography (DQCT technique).
The above-enumerated techniques are the ones for measuring the so-called “bone density.” The bone density has heretofore been utilized popularly as an index value for a diagnosis of osteoporosis. Recently, besides the bone density value, it has been proposed to quantitatively represent the condition of a bone structure as an index value.
Specifically, in a simple sense, the bone density value is the value of the ratio of the mass to the volume. Therefore, the bone density value does not reflect a difference in condition of distribution of bone trabeculae, which are the substance as the bone for supporting a load, i.e. a difference in bone structure. However, primarily, osteoporosis is the problem of the bone strength. The bone strength markedly depends upon the condition of a distribution of bone trabeculae. Therefore, a technique for representing the condition of a bone structure as an index value is a technique useful for a diagnosis of osteoporosis.
By way of example, as an index value for representing the condition of a bone structure, there have heretofore been known a star volume and an index value obtained with node-strut analysis.
As an aid in simplifying the explanation, a processing technique for calculating the star volume as an index value will hereinbelow be referred to as the star volume technique. Also, a processing technique for calculating an index value with node-strut analysis will hereinbelow be referred to as the node-strut analysis technique.
FIG. 3
is an explanatory view showing index values with the star volume technique. In the star volume technique, marrow space star volume (Vm) and trabecular star volume (Vt) are defined. The marrow space star volume (Vm) represents the mean value of the values of the bone marrow cavity volume of the regions, each of which extends from a predetermined point, a, in the bone marrow cavity along every direction without being obstructed by the bone trabeculae. The trabecular star volume (Vt) represents the mean value of the values of the volume of the regions, each of which extends from a point, b, in the bone trabecula along every direction to the end of the bone trabecula. In
FIG. 3
, the hatched regions indicate the bone trabeculae, and the other region indicates the bone marrow cavity. The star volume is considered as being a gap-free stereological index, which represents the size of the bone trabecula in the bone marrow cavity as a three-dimensional value in units of mm
3
or &mgr;m
3
by elaborating the sampling technique. In cases where the continuity of the bone trabeculae is high, Vm takes a small value. In cases where the level of disappearance or porosity of the bone trabeculae is high, Vm takes a large value. Conversely, in cases where the continuity of the bone trabeculae is high, Vt takes a large value. In cases where the level of disappearance or porosity of the bone trabeculae is high, vt takes a small value.
The value of Vmi at an arbitrary point i in the bone marrow cavity is defined by Formula (1) shown below.
Vmi=(&pgr;/3)×l
0m
3
(1)
In Formula (1), in cases where the length, over which the bone-marrow cavity is continuous along an arbitrary direction extending from the point i, is represented by l
0
, l
0m
3
represents the mean value of the values l
0
3
calculated with respect to all of radial directions extending from the point i.
The value of Vtj at an arbitrary point j in the bone trabecula is defined by Formula (2) shown below.
Vtj=(&pgr;/3)×&Sgr;l
1
4
/&Sgr;l
1
(2)
wherein l
1
represents the length, over which the bone trabecula is continuous along an arbitrary direction extending from the point j. The values of l
1
are calculated with respect to all of radial directions extending from the point j, and &Sgr; represents the calculation of the sum of the values with respect to all of the radial directions.
In such cases, Vmi may be calculated for each sampling point, and the mean value of the Vmi values, which have been calculated for all of the sampling points, may be taken as Vm. Also, Vtj may be calculated for each sampling point, and the mean value of the vtj values, which have been calculated for all of the sampling points, may be taken as Vt.
As the index value representing the bone trabecula structure, either one of Vm and Vt may be employed.
Also, for example, as illustrated in
FIG. 4
, the three-dimensional coordinate system, which has the coordinate axes for the age of an object, the bone density value, and the value of Vt, is formed. A judgment as to the condition of the bone tissue is made in accordance with a position on the three-dimensional coordinate system, at which the received results are plotted. Specifically, in cases where the age of the object, the bone density value, and the value of Vt are located at a point P
1
, it is judged that the bone tissue is in the condition A (e.g., the condition suspected to be osteoporosis). In cases where the age of the object, the bone density value, and the value of Vt are located at a point P
2
, it is judged that the bone tissue is in the condition B (the condition requiring care). Also, in cases where the age of the object, the bone density value, and the value of Vt are located at a point P
3
, it is judged that the bone tissue is in the condition C (the normal condition).
The node-strut analysis technique is a technique for two-dimensionally rating the continuity of the bone trabeculae. Specifically, a connection point, at which three or more bone trabeculae are connected with one another, is defined as a node (Nd) (indicated by the white dot in FIG.
5
), and a terminal point, at which the bone trabecula is not connected with other bone trabeculae, is defined as a terminus (Tm) (indicated by the black dot in FIG.
5
). As illustrated in
FIG. 5
, the center lines (struts) of the bone trabeculae, which lines connect the points, are classified into NdNd (the strut connecting the connection points with each other), NdTm (the strut connecting a connection point and a terminal point with each other), TmTm (the strut connecting the terminal points with each other), CtNd (the strut connecting Ct, i.e. the cortical bone, and a connection point each other), and CtTm (the strut connecting the cortical bone and a terminal point with each other). The lengths of the respective struts are measured.
Thereafter, the index values described below are defined in accordance with the lengths of the struts, the number N
Nd
of the
Fuji Photo Film Co. , Ltd.
Lateef Marvin M.
Lin Jeoyuh
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