Title of Invention	METHOD OF ESTIMATING THE VOLUME OF A THREE-DIMENSIONAL OBJECT HAVING A KNOWN CONTOUR
Abstract	Process for estimating and segmenting the volume of a three-dimensional object in medical imaging, in which: a given number of base points is defined which constitute a first three-dimensional form defined by facets, - each facet of the first form being defined by three segments, the segments are divided by defining second- order points adapted to the outline of the object in such a way as to constitute a second three-dimensional form which is closer to the outline of the object than the first form, - each segment is iteratively divided into tailored sub-segments by defining third-order points adapted to the outline of the object in such a way as to constitute a third three-dimensional form which is closer to the outline of the object than the second form, - then the volume of the third three-dimensional form is calculated. Reference: Figure 1.

Title of Invention

METHOD OF ESTIMATING THE VOLUME OF A THREE-DIMENSIONAL OBJECT HAVING A KNOWN CONTOUR

Abstract

Process for estimating and segmenting the volume of a three-dimensional object in medical imaging, in which: a given number of base points is defined which constitute a first three-dimensional form defined by facets, - each facet of the first form being defined by three segments, the segments are divided by defining second- order points adapted to the outline of the object in such a way as to constitute a second three-dimensional form which is closer to the outline of the object than the first form, - each segment is iteratively divided into tailored sub-segments by defining third-order points adapted to the outline of the object in such a way as to constitute a third three-dimensional form which is closer to the outline of the object than the second form, - then the volume of the third three-dimensional form is calculated. Reference: Figure 1.

Full Text	The present invention relates to method of estimating the volume of a three-dimensional object having a known contour in certain medical imaging applications there is a need for accurate knowledge of the volume of three-dimensional objects, for example an organ or a part of an organ of the human body. Such processes are known which make it possible to approximate the volume of an object by knowing the outline of this object in various sectional cuts, the profile between the cuts then being modelled by a continuous slope. The three-dimensional object is thus modelled by a plurality of frustoconical volumes of small thickness. However, this process compels an operator to trace the outline of the object, this requiring meticulous and slow work. The present invention seeks to solve the problems of the above process by proposing a simple process which is easy to use and makes it possible to obtain the desired accuracy swiftly. The process, according to the invention, is intended for estimating the volume of a three-dimensional object in medical imaging, an outline of the object being known by means of a plurality of sectional snapshots. The process comprises the following steps: a given number of base points is defined which constitute a first three-dimensional form defined by facets whose vertices are the base points, each facet of the first form being defined by three segments and each segment being common to two adjacent facets, the segments are divided by creating second-order points adapted to the outline of the object in such a way as to constitute a second three- dimensional form which is closer to the outline of the object than the first form, the creation of a second-order point entailing the creation of two new facets and of three new segments, each segment is iteratively divided into tailored sub-segments by defining third-order points adapted to the outline of the object in such a way as to constitute a third three-dimensional form which is closer to the outline of the object than the second form, the creation of a third-order point entailing the creation of two new facets and of three new segments, then the volume of the third three-dimensional form is calculated. How ? It is thus merely necessary to define points rather than an outline, thus making the work easier. In one embodiment of the invention, the snapshots are taken as parallel sections. In another embodiment of the invention, a plurality of snapshots is processed to provide a description of the three-dimensional volume. Advantageously, each segment is divided into two. In one embodiment of the invention, the position of each second point is proposed as a function of the position of the two first adjacent points. Each second point can thus be proposed as a function of the orientation of the normals at the two first adjacent points. In one embodiment of the invention, the segments are divided into sub-segments until the change of volume resulting from a given division is negligible. It is thus possible to choose a threshold change of volume below which the iterative division into sub-segments is halted. This change-of-volume threshold corresponds to the desired accuracy of the process. In one embodiment of the invention, six first base points are defined and these are arranged on the top and on the bottom, on the front and on the back, and on each lateral edge of the object. A calculation of distribution of the density of the object in space can be performed after calculating the estimated volume of the object. Any point of the three-dimensional forms can be modified manually, for example to adapt it to an irregularity of the relief of the object such as a hollow or a bump. A different weighting is accorded to the points so as to approximate the actual outline of the object as closely as possible. A modification of a first base point will entail a corresponding modification of all the neighbouring points. On the other hand, a modification of a third point of the third form will not entail any modification of the first and second adjacent points and may slightly modify the position of the third adjacent points. In a very flexible manner, it is thus possible to effect improvements to the various forms culminating in making them closer to the actual outline of the three-dimensional object. Also, so as to maintain high flexibility of use, any point, including a third-order point, can be defined manually. The present invention will be better understood and other advantages will emerge with the detailed description of an embodiment taken by way of non-limiting example and illustrated by the appended drawings in which: Figure 1 isa perspective view of a final form according to the invention; Figures 2 and 3 are schematic views in two dimensions of the process according to the invention; and Figures 4 and 5 are schematic views in three dimensions of the process according to the invention. As may be seen in Figure 1, a final form which approximates a three-dimensional object consists of a plurality of facets defined by three segments, for example the segments 1 to 3 defining a plane triangular surface 4. The volume of the three-dimensional object, not represented, is thus approximated by means of triangular surfaces, the coordinates of the vertex points of which are known. It is thus possible to calculate the volume of the form. An operator begins by defining six points of object, an upper point 11, a lower point 12,a left lateral point 13, a right lateral point 14, a front point 15 and a back point which cannot be seen in Figure 1. This first form thus defines the three-dimensional object roughly, the positioning of these six base points must be performed accurately since their definition governs that of the future adjacent points. To obtain satisfactory definition, it may be necessary to check their positioning on various sections through the object. After having defined the six first points, an oblique view is added to the existing views, making it possible by orientation and centring to define additional points. It is then possible to define the additional points at the intersection of the normal to one of the segments of the base volume, the normal being calculated from the facets and points forming this segment, and of the edge of the three-dimensional object under study. A certain number of second points constituting a second form are defined manually or automatically. When the change of volume resulting from the defining of second points becomes less than a threshold, the defining of points can then be continued automatically by segmenting the existing facets until a sufficient match with the three-dimensional object under study is obtained, thereby constituting a third form. However, it is possible to continue defining points manually. When the final volume is defined, it is possible to modify points whose definition does not satisfactorily match an irregularity in the three- dimensional object under study, especially a hollow or a protuberance. The point is then moved along the normal to the facet to which the point belongs, the normal being calculated from the facets. The points adjacent to the modified points will also be modified so as to maintain the regularity of the volume defined by taking account of the said point's belonging to the first, second or third form. The movement of a point of the first form entails a corresponding movement of all the adjacent points. The movement of a point of the third form does not entail any movement of the adjacent points of the first and second forms. Figures 2 and 3 show schematically, in two dimensions, the procedure for defining the points. Starting from an outline 20, first base points 21 to 23 are defined and make it possible to define the said outline 20 roughly. The straight segments 24 to 26 joining the first base points 21 to 23 are then defined. The normals 27 to 29 to these segments 24 to 26 are then calculated. It is then possible to define second points 30 to 32 which more accurately approximate the outline 20, by moving along the normals 27 to 29. The segments 33 to 38 joining the points 21 to 23 and 30 to 32 are then defined, this making it possible to reproduce the previous steps, manually, semi-automatically or automatically until the desired accuracy is obtained. Figures 4 and 5 show schematically, in three dimensions, the procedure for defining the points. Two facets 40 and 41 belonging to an outline are represented. The facet 40 is demarcated by the base points 42, 43 and 44. The facet 41 is demarcated by the base points 43, 44 and 45. The base points 43 and 44 are therefore common to the facets 40 and 41 and define a segment 46. A second-level point 47 is defined thereafter, this entailing the creation of the additional facets 48 and 49 and of the additional segments 50 to 52. The invention thus makes available a process for estimating the volume of a three-dimensional object adapted to radiological imaging, which is easy to use since only a small number of points have to be defined on the edge of the three-dimensional object, is easy to control, thereby guaranteeing a good approximation of the outline, is fast, since the automatic definition phase can be performed in a few seconds and is easily reproducible insofar as it rests upon the definition of a small number of points on the outline of the object. We claim: 1. A method of estimating and segmenting the volume of a three-dimensional object an outline of said object being known by means of a plurality of sectional snapshots, comprising the steps of: defining a given number of base points in a first image of the object that represents a first three dimensional form defined by facets whose vertices are the base points; defining each facet of the first form by three segments and each segment being common to two adjacent facets; creating a second order points adapted to the outline of the object by dividing the segments so as to constitute a second three-dimensional form closer to the outline of the object than the first form, the creation of each second order point resulting in the creation of at least two new facets and at least three new segments; defining third or more order points adapted to the outline of the object by iteratively dividing each new segment into subsegments, so as to constitute a third or more three-dimensional form closer to the outline of the object than the second three-dimensional form, the creation of the third or more order points resulting in the creation of at least two additional new facets and at least three additional new segments; and estimating the volume of the third or more three-dimensional form of the object from the images of the object in a known manner. 2. The method as claimed in claim 1 wherein the snapshots are taken as parallel sections. 3. The method as claimed in claim 1 comprising processing of plurality of snapshots to provide a description of the three-dimensional volume. 4. The method as claimed in claim 1, 2 or 3 wherein each segment is divided by two. 5. The method as claimed in anyone of claim 1, 2, 3 or 4 wherein the position of each of the second point is a function of the position of the first two adjacent facets. 6. The method as claimed in claim 1 comprising the step of dividing the segments into additional subsegments until the change in volume for each further iteration resulting from a given division reaches a volume according to the desire of the operator or as defined by preset conditions. 7. The method as claimed in claim 1 wherein the given number of base points is six. 8. The method as claimed in claim 1 wherein any point of the three-dimensional forms can be modified. 9. The method as claimed in claim 1 wherein any of the points are defined manually. 10. The method as claimed in claim 1 wherein there is a change in the calculated volume, which defines a threshold below which the iterative division is stopped. 11. The method as claimed in claim 1 wherein each segment or subsegment is divided by a perpendicular to the segment or subsegment. 12. The method as claimed in claim 1 wherein the position of each of the second order is a function of the orientation of perpendiculars to the first two adjacent faces. 13. The method as claimed in claim 1 wherein the segments are divided into further additional segments until the change in volume resulting from a given division is negligible. 14. The method as claimed in claim 1 comprising calculating the distribution of density of the object in space. 15. The method as claimed in claim 1 wherein steps are repeated for a defined number of the plurality of snapshots.

Full Text

The present invention relates to method of estimating the volume of a three-dimensional object having a known contour
in certain medical imaging applications there is a need for accurate knowledge of the volume of three-dimensional objects, for example an organ or a part of an organ of the human body.
Such processes are known which make it possible to approximate the volume of an object by knowing the outline of this object in various sectional cuts, the profile between the cuts then being modelled by a continuous slope. The three-dimensional object is thus modelled by a plurality of frustoconical volumes of small thickness. However, this process compels an operator to trace the outline of the object, this requiring meticulous and slow work.
The present invention seeks to solve the problems of the above process by proposing a simple process which is easy to use and makes it possible to obtain the desired accuracy swiftly.
The process, according to the invention, is intended for estimating the volume of a three-dimensional object in medical imaging, an outline of the object being known by means of a plurality of sectional snapshots.
The process comprises the following steps: a given number of base points is defined which constitute a first three-dimensional form defined by facets whose vertices are the base points,
each facet of the first form being defined by three segments and each segment being common to two adjacent facets, the segments are divided by creating second-order points adapted to the outline of the object in such a way as to constitute a second three-
dimensional form which is closer to the outline of the object than the first form, the creation of a second-order point entailing the creation of two new facets and of three new segments,
each segment is iteratively divided into tailored sub-segments by defining third-order points adapted to the outline of the object in such a way as to constitute a third three-dimensional form which is closer to the outline of the object than the second form, the creation of a third-order point entailing the creation of two new facets and of three new segments,
then the volume of the third three-dimensional
form is calculated. How ?
It is thus merely necessary to define points rather than an outline, thus making the work easier.
In one embodiment of the invention, the snapshots are taken as parallel sections.
In another embodiment of the invention, a plurality of snapshots is processed to provide a description of the three-dimensional volume.
Advantageously, each segment is divided into two.
In one embodiment of the invention, the position of each second point is proposed as a function of the position of the two first adjacent points. Each second point can thus be proposed as a function of the orientation of the normals at the two first adjacent points.
In one embodiment of the invention, the segments are divided into sub-segments until the change of volume resulting from a given division is negligible. It is thus possible to choose a threshold change of volume below which the iterative division into sub-segments is halted. This change-of-volume threshold corresponds to the desired accuracy of the process.
In one embodiment of the invention, six first base points are defined and these are arranged on the
top and on the bottom, on the front and on the back, and on each lateral edge of the object.
A calculation of distribution of the density of the object in space can be performed after calculating the estimated volume of the object.
Any point of the three-dimensional forms can be modified manually, for example to adapt it to an irregularity of the relief of the object such as a hollow or a bump. A different weighting is accorded to the points so as to approximate the actual outline of the object as closely as possible. A modification of a first base point will entail a corresponding modification of all the neighbouring points. On the other hand, a modification of a third point of the third form will not entail any modification of the first and second adjacent points and may slightly modify the position of the third adjacent points. In a very flexible manner, it is thus possible to effect improvements to the various forms culminating in making them closer to the actual outline of the three-dimensional object.
Also, so as to maintain high flexibility of use, any point, including a third-order point, can be defined manually.
The present invention will be better understood and other advantages will emerge with the detailed description of an embodiment taken by way of non-limiting example and illustrated by the appended drawings in which:

Figure 1 isa perspective view of a final form according to the invention;
Figures 2 and 3 are schematic views in two dimensions of the process according to the invention; and
Figures 4 and 5 are schematic views in three dimensions of the process according to the invention.
As may be seen in Figure 1, a final form which approximates a three-dimensional object consists of a plurality of facets defined by three segments, for example the segments 1 to 3 defining a plane triangular surface 4. The volume of the three-dimensional object, not represented, is thus approximated by means of triangular surfaces, the coordinates of the vertex points of which are known. It is thus possible to calculate the volume of the form.
An operator begins by defining six points of object, an upper point 11, a lower point 12,a left lateral point 13, a right lateral point 14, a front point 15 and a back point which cannot be seen in Figure 1. This first form thus defines the three-dimensional object roughly, the positioning of these six base points must be performed accurately since their definition governs that of the future adjacent points. To obtain satisfactory definition, it may be necessary to check their positioning on various sections through the object.
After having defined the six first points, an oblique view is added to the existing views, making it possible by orientation and centring to define additional points.
It is then possible to define the additional points at the intersection of the normal to one of the segments of the base volume, the normal being calculated from the facets and points forming this segment, and of the edge of the three-dimensional object under study. A certain number of second points constituting a second form are defined manually or automatically. When the change of volume resulting from the defining of second points becomes less than a threshold, the defining of points can then be continued automatically by segmenting the existing facets until a sufficient match with the three-dimensional object under study is obtained, thereby constituting a third form. However, it is possible to continue defining points manually.
When the final volume is defined, it is possible to modify points whose definition does not satisfactorily match an irregularity in the three-
dimensional object under study, especially a hollow or a protuberance. The point is then moved along the normal to the facet to which the point belongs, the normal being calculated from the facets.
The points adjacent to the modified points will also be modified so as to maintain the regularity of the volume defined by taking account of the said point's belonging to the first, second or third form. The movement of a point of the first form entails a corresponding movement of all the adjacent points. The movement of a point of the third form does not entail any movement of the adjacent points of the first and second forms.
Figures 2 and 3 show schematically, in two dimensions, the procedure for defining the points. Starting from an outline 20, first base points 21 to 23 are defined and make it possible to define the said outline 20 roughly. The straight segments 24 to 26 joining the first base points 21 to 23 are then defined. The normals 27 to 29 to these segments 24 to
26 are then calculated. It is then possible to define
second points 30 to 32 which more accurately
approximate the outline 20, by moving along the normals
27 to 29. The segments 33 to 38 joining the points 21
to 23 and 30 to 32 are then defined, this making it
possible to reproduce the previous steps, manually,
semi-automatically or automatically until the desired
accuracy is obtained.
Figures 4 and 5 show schematically, in three dimensions, the procedure for defining the points. Two facets 40 and 41 belonging to an outline are represented. The facet 40 is demarcated by the base points 42, 43 and 44. The facet 41 is demarcated by the base points 43, 44 and 45. The base points 43 and 44 are therefore common to the facets 40 and 41 and define a segment 46. A second-level point 47 is defined thereafter, this entailing the creation of the additional facets 48 and 49 and of the additional segments 50 to 52.
The invention thus makes available a process for estimating the volume of a three-dimensional object adapted to radiological imaging, which is easy to use since only a small number of points have to be defined on the edge of the three-dimensional object, is easy to control, thereby guaranteeing a good approximation of the outline, is fast, since the automatic definition phase can be performed in a few seconds and is easily reproducible insofar as it rests upon the definition of a small number of points on the outline of the object.

We claim:
1. A method of estimating and segmenting the volume of a three-dimensional object an outline of said object being known by means of a plurality of sectional snapshots, comprising the steps of:
defining a given number of base points in a first image of the object that represents a first three dimensional form defined by facets whose vertices are the base points;
defining each facet of the first form by three segments and each segment being common to two adjacent facets;
creating a second order points adapted to the outline of the object by dividing the segments so as to constitute a second three-dimensional form closer to the outline of the object than the first form, the creation of each second order point resulting in the creation of at least two new facets and at least three new segments; defining third or more order points adapted to the outline of the object by iteratively dividing each new segment into subsegments, so as to constitute a third or more three-dimensional form closer to the outline of the object than the second three-dimensional form, the creation of the third or more order points resulting in the creation of at least two additional new facets and at least three additional new segments; and
estimating the volume of the third or more three-dimensional form of the object from the images of the object in a known manner.
2. The method as claimed in claim 1 wherein the snapshots are taken as parallel
sections.
3. The method as claimed in claim 1 comprising processing of plurality of snapshots
to provide a description of the three-dimensional volume.
4. The method as claimed in claim 1, 2 or 3 wherein each segment is divided by two.
5. The method as claimed in anyone of claim 1, 2, 3 or 4 wherein the position of
each of the second point is a function of the position of the first two adjacent
facets.
6. The method as claimed in claim 1 comprising the step of dividing the segments
into additional subsegments until the change in volume for each further iteration
resulting from a given division reaches a volume according to the desire of the
operator or as defined by preset conditions.
7. The method as claimed in claim 1 wherein the given number of base points is six.
8. The method as claimed in claim 1 wherein any point of the three-dimensional
forms can be modified.
9. The method as claimed in claim 1 wherein any of the points are defined manually.
10. The method as claimed in claim 1 wherein there is a change in the calculated
volume, which defines a threshold below which the iterative division is stopped.
11. The method as claimed in claim 1 wherein each segment or subsegment is divided
by a perpendicular to the segment or subsegment.
12. The method as claimed in claim 1 wherein the position of each of the second
order is a function of the orientation of perpendiculars to the first two adjacent
faces.
13. The method as claimed in claim 1 wherein the segments are divided into further
additional segments until the change in volume resulting from a given division is
negligible.
14. The method as claimed in claim 1 comprising calculating the distribution of
density of the object in space.
15. The method as claimed in claim 1 wherein steps are repeated for a defined
number of the plurality of snapshots.

Documents:

3612-del-1998-abstract.pdf

3612-del-1998-claims.pdf

3612-del-1998-correspondence-others.pdf

3612-del-1998-correspondence-po.pdf

3612-del-1998-description (complete).pdf

3612-del-1998-drawings.pdf

3612-del-1998-form-1.pdf

3612-del-1998-form-19.pdf

3612-del-1998-form-2.pdf

3612-del-1998-form-3.pdf

3612-del-1998-form-4.pdf

3612-del-1998-form-6.pdf

3612-del-1998-pa.pdf

3612-del-1998-petition-124.pdf

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Patent Number

232065

Indian Patent Application Number

3612/DEL/1998

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

15-Mar-2009

Date of Filing

30-Nov-1998

Name of Patentee

GE MEDICAL SYSTEMS SA,

Applicant Address

283, RUE DE LA MINIERE 78533 BUC CEDEX, FRANCE.

Inventors:

#	Inventor's Name	Inventor's Address
1	ERIC STEFANI	14, RUE DE LA BELLE FEUILLE, 92100 BOULOGNE BILLANCOURT, FRANCE.
2	JEROME KNOPLIOCH,	52BIS, RUE JACQUES DULUD 92200 NEUILLY-SUR-SEINE, FRANCE.

PCT International Classification Number

G06K 9/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	97 15639	1997-12-10	France