Patent Description:
Herewith it is possible to identify any occlusion present in the coronary arteries and/or veins and to determine their location, size and extent of the occlusions if present.

Such a method and apparatus is for example disclosed in U. Patent Application Publication No. <CIT>.

Usually several two-dimensional image projections are needed and acquired from different view points (that is taken at different imaging positions of the imaging means relative to the patient) based on which a suitable three-dimensional contour image of the targeted organ is constructed. However the selection of the correct set of different two-dimensional image projections for the reconstruction of a three-dimensional representation (3D contour image) of the target volume still requires the acquisition and the analyzing by a diagnostician of multiple two-dimensional image projections before a decision on the correct set is being made.

This tends to lead to unnecessary lengthy imaging treatment session for the patient, which is undesirable due to radiation exposure, but also to incorrect selection of the correct set of image projections resulting in less accurate diagnosis and subsequent treatment of the patient.

It is an object of the invention to provide an improved method according to claim <NUM> and apparatus according to claim <NUM> for reconstructing a three-dimensional representation of a target volume inside an animal or human body allowing for a faster and more sophisticated imaging technique, thus reducing the acquisition and the analyzing time of the imaging diagnosis and limiting the imaging treatment session for the patient as well as avoiding diagnosis errors by the diagnostician. Optional features of the invention are defined in the dependent claims.

According to the disclosed method, step ii) is preceded by the steps of:.

Accordingly, with these features an improved reconstructing method is obtained, wherein an optimal set of two-dimensional image projections is obtained and proposed, based on which a correct three-dimensional contour image of said target volume is being reconstructed. Thus with this correct three-dimensional contour image the diagnostician is capable of performing a more accurate diagnosis and subsequent treatment of the patient, which in turn is subjected to a less lengthy imaging treatment session, which is beneficial in terms of radiation exposure time, discomfort, etc..

In a further aspect of the method, method step a3) comprises the step of a3a defining a first subset of second operational orientation settings of said imaging means for orientation in said second imaging position, said first subset of second operational orientation settings being distinct from said first operational orientation setting.

By defining a first subset of second operational orientation settings of said imaging means for orientation in said second imaging position, wherein said first subset of second operational orientation settings is distinct from said first operational orientation setting any duplication of acquiring identical or more or less identical two-dimensional image projections is being avoided. Herewith the length if the imaging treatment session is further reduced (which is beneficial for the patient), but also incorrect or unsuitable three-dimensional contour images are not reconstructed thus avoiding incorrect analysis and diagnosis of the target volume of the patient by the diagnostician.

More in particular method step a3) comprises the step of a3b defining a second subset of second operational orientation settings of said imaging means for orientation in said second imaging position, said second subset of second operational orientation settings being conformal to said first operational orientation setting.

This second subset defines and represents a series of operational orientation settings which are conformal to the operational orientation setting belonging to the first image projection being acquired and thus should be avoided when acquiring a second image projection of the target volume. With this 'no-go set' operational orientation settings analysis and diagnosis errors of the target volume of the patient by the diagnostician are avoided.

In particular as the method step a4) comprises the step of selecting said one of said second operational orientation settings from said first subset of second operational orientation settings an improved reconstructing method is obtained resulting in a correct three-dimensional contour image based on which the diagnostician is capable of performing a more accurate diagnosis and subsequent treatment of the patient.

Method step a4) is preceded by the step of determining a longitudinal orientation of said target volume in said first two-dimensional image projection. Method step a4) comprises the step of selecting said one of said second operational orientation settings to correspond to a second imaging position being defined in a plane perpendicular to said longitudinal orientation of said target volume being determined.

Herewith two distinct image projections are acquired based on which a correct three-dimensional contour image is being reconstructed and thus a correct analysis and diagnosis of the target volume of the patient by the diagnostician can be performed.

The acquisition of two distinct image projections and the resulting three-dimensional contour image is thus obtained as the step of determining said longitudinal orientation of said target volume in said first two-dimensional image projection comprises the steps of defining in said first two-dimensional image projection a first point of interest inside said target volume as well as a second point of interest inside said target volume and determining said longitudinal orientation of said target volume based on said first and second point of interest.

In particular said first subset of second operational orientation settings limit an angle between a first plane in which said first imaging position corresponding to said first operational orientation setting is defined and a second plane in which said second imaging positions corresponding to said second operational orientation settings are defined between a range of <NUM>°-<NUM>°. Herewith the acquisition of an incorrect set of two-dimensional image projections and an inaccurate three-dimensional contour image based on this set is thus avoided further improving the reconstructing method according to the invention.

In a further automation of the reconstruction method of the invention the method step a5) is preceded by the step of positioning said imaging means in said second imaging position corresponding to said second operational orientation setting.

In particular said target volume is a coronary artery and said imaging means comprise an X-ray imaging device.

In the apparatus for reconstructing a three-dimensional representation of a target volume inside an animal or human body according to the disclosure said displaying means are arranged for displaying said first two-dimensional contour image of the target volume being obtained with the imaging means being positioned in said first imaging position for a user; and said transformation means are arranged for acquiring a first operational orientation setting of said imaging means corresponding with said first imaging position; and for defining based on said first operational orientation setting a first set of second operational orientation settings of said imaging means for orientation in a second imaging position; and for selecting from said set one of said second operational orientation settings; and for using said second operational orientation setting being selected for acquiring said second two-dimensional image projection of said target volume using said imaging means being positioned in the second imaging position corresponding to said second operational orientation setting.

Accordingly, with these features an improved apparatus for reconstructing a three-dimensional representation of a target volume is obtained, wherein an optimal set of two-dimensional image projections is obtained and proposed, based on which a correct three-dimensional contour image of said target volume is being reconstructed. Thus with this correct three-dimensional contour image the diagnostician is capable of performing a more accurate diagnosis and subsequent treatment of the patient, which in turn is subjected to a less lengthy imaging treatment session, which is beneficial in terms of radiation exposure time, discomfort, etc..

The invention will now be described in more detail with reference to the accompanying drawings, which drawings show in:.

<FIG> shows in very schematic form various elements of a known imaging device <NUM>. An object <NUM>, here a human patient <NUM> is shown lying in lithotomy position on a table <NUM> which is supported by a base <NUM>. Above the table <NUM> imaging means <NUM> are positioned which imaging means <NUM> are movable accommodated in a structure (not shown) forming part of the imaging device <NUM>. This allows for a controlled positioning of the imaging means <NUM> at any angle or orientation relative to a target volume <NUM>' inside the patient's body <NUM>.

The imaging means <NUM> can be any imaging technique capable of obtaining 2D image projection of a target volume (here indicate with reference numeral <NUM>) in an object <NUM>. For example X-ray radiation imaging means can be used when implementing the method and apparatus according to the invention.

It should be noted that the object <NUM> lying on the table <NUM> can be a human or animal body or any other object which is to be subjected to the apparatus and method according to the invention.

According to the invention the imaging device <NUM> during operation interact with a data acquisition apparatus <NUM>. Data acquisition apparatus <NUM> can be a separate apparatus that is communicatively linked to the imaging device <NUM> or the data acquisition apparatus <NUM> can form an integral part of the imaging device <NUM>. Data acquisition apparatus <NUM> is at least composed of a data image storage <NUM>, a processing unit <NUM> and a display unit <NUM>. The data storage unit <NUM> is communicatively connected with the imaging means <NUM> via data-communication link 13a. Data storage unit <NUM> is bi-directionally connected to the processing unit <NUM>, which in turn is bi-directionally connected to the display unit/means <NUM>. Also processing unit <NUM> is bi-directionally connected to the imaging device <NUM> via communication link <NUM>.

Preferably the storage unit <NUM>, the processing unit <NUM> and the display unit/means <NUM> are constructed in one constructional entity, however they can also be separate parts.

The processing unit <NUM> or the display unit <NUM> also comprises image transformation means <NUM> (in <FIG> depicted as being comprises in the processing unit <NUM>) for reconstructing a three-dimensional contour image of the target volume from (using) two-dimensional image projections being acquired with the imaging means <NUM>.

In <FIG> and <FIG> two side views are shown of the apparatus as shown in <FIG>. In <FIG> the apparatus according to the invention is shown with the patient <NUM> lying in longitudinal direction. The imaging device <NUM> as shown in this side view of <FIG> is positioned at an angle α1 relative to a vertical axis Z which is orientated perpendicular to the horizontal table <NUM> on which the patient <NUM> is positioned. Also, the vertical axis Z points directly to the target volume <NUM>' which in this example represents the heart of the patient <NUM>. As shown in <FIG>, imaging device <NUM> is positioned at an angle α1 relative to the vertical axis Z pointing towards the target volume <NUM>'.

During operation the imaging device <NUM> will emit X-ray radiation <NUM> towards the target volume <NUM>' to acquire a two-αdimensional image projection of the target volume <NUM>'. These imaging techniques are known in the art.

As clearly shown in <FIG>, the imaging device <NUM> can be orientated in a range of angles, where positive angles are denoted CRA (Cranial) and negative angles are denoted CAU (Caudal) relative to the body of the patient, which angle ANG ranges between the extreme angle CRA45 (α = +<NUM>°) near the head of the patient and the other extreme angle CAU45 (α = -<NUM>°) near the feet/extreme end of the patient). At α = <NUM>°, the imaging device <NUM> is positioned right above the patient <NUM> at the axis Z. In <FIG> the imaging device <NUM> is shown as being positioned approximately at the position CRA <NUM>, meaning α = <NUM>°.

In <FIG> a frontal view is shown which corresponds with the side view as depicted in <FIG>. In <FIG> it is shown that the imaging device <NUM> can also be positioned at different angles ROT in the range of β ≈ -<NUM>° (the right anterior oblique view RAO) and β ≈ +<NUM>° (left anterior oblique view LAO).

Each two-dimensional image projection obtained with the imaging device <NUM> can be characterised by its angular orientation relative to the patient <NUM> by means of its angular orientation α (ANG) and rotational orientation β (ROT) relative to the object <NUM> lying on the table <NUM>.

Such a two-dimensional image projection is for example shown in <FIG> depicts an implementation of the method according to the invention as implemented in an apparatus <NUM> according to the invention. Reference numeral <NUM> corresponds to the display unit <NUM> as shown in <FIG> and implements a working environment on a display means. A part of the working environment <NUM> (working environment field <NUM>) is used to display the first image projection <NUM>' that depicts the target volume <NUM>' in a two-dimensional projection. It is noted that the two-dimensional image projection <NUM>' as shown in the working environment <NUM> has been obtained with the imaging device <NUM> being positioned in an angular orientation α1 and a rotational orientation β1.

The method and apparatus according to the invention implements transformation means <NUM> for reconstructing a three-dimensional contour image of the target volume <NUM>' from (using) at least two different two-dimensional image projections being obtained with the imaging device <NUM> for analysis and diagnosis by an user or diagnostician. At least two different two-dimensional image projections are to be acquired using the imaging device <NUM>, which two two-dimensional image projections need to be sufficiently distinct from each other in order to acquire an accurate 3D representation after reconstruction.

It will be clear that if the two image projections being used are both obtained at more or less the same orientation (position) of the imaging device <NUM> relative to the target volume <NUM>, both image projections more or less will overlap in the same two-dimensional plane of the projections and an accurate 3D reconstruction is less feasible or even impossible.

Hereto, according to the method and apparatus according to the invention, the first two-dimensional image projection obtained at the angular orientation α1 and the rotational orientation β1 of the imaging device <NUM> is acquired via the imaging device <NUM> and stored in the storage unit <NUM> via the communication link 13a. The processing unit <NUM> acquires the first two-dimensional image projection from the storage unit <NUM> and communicates it towards the display unit <NUM>.

The display unit <NUM> displays the first two-dimensional image projection <NUM>' (characterised by the angular orientation α1 and the rotational orientation β1 corresponding with the first imaging position) is displayed at the working environment field <NUM> of the working environment <NUM> of the display means. Simultaneously, the first operational orientation setting (α1; β1) which represents the angular and rotational orientation of the imaging device <NUM> at the time of acquiring the first two-dimensional image projection <NUM>' is acquired by the processing unit <NUM> and/or the display unit <NUM>.

Based on the first operational orientation setting (α1; β1) a first set of second operational orientation settings (α2; β2) is defined. The first set of second operational orientation settings (α2; β2) represents a set of possible second imaging positions characterised by angular orientation α2 and rotational orientation β2 in which the imaging device <NUM> can be positioned for acquiring a second image projection <NUM>" which can be used together with the first orientation projection <NUM>' acquired in the first imaging position (α1; β1) for reconstructing a three-dimensional representation of the target volume.

Said first set of second operational orientation settings (α2; β2) is being calculated and represented in the operational work field <NUM> of <FIG> and in more detail in <FIG>.

The first set of second operational orientation settings (α2; β2) is represented with reference numeral <NUM> in <FIG>. Said first set <NUM> represents all possible orientations of the imaging device <NUM> in terms of an angular orientation α2 and a rotational orientation β2 relative to the target volume <NUM>' as shown in <FIG> and <FIG>. The angular orientation α2 can be set between CAU <NUM> and CRA <NUM> represented by -<NUM>° respectively +<NUM>°. The rotational orientation β2 can be set between the right anterior oblique view and left anterior oblique view represented by -<NUM>° respectively +<NUM>°.

In particular, according to a further aspect of the method according to the invention, the first set <NUM> of possible second operational orientation settings (α2; β2) is being defined in a first subset <NUM> and a second subset <NUM> of second operational orientation settings. The first subset of second operational settings <NUM> represents an optimum subset of second operational orientation settings (α2; β2) which are clearly distinct from the first operational orientation setting (α1; β1).

Likewise, the second subset of second operational orientation settings <NUM> represent a subset of second operational orientation settings which are more or less conformal to the first operational orientation setting (α1; β1). The method and the apparatus according to the invention determines and displays both the first subset <NUM> and the second subset <NUM> of second operational orientation settings of the imaging device <NUM>.

The method and the apparatus operate such that it is decided to rule out the second subset <NUM> of second operational orientation settings as possible choices for a second imaging position for the imaging device <NUM>. In particular the method and apparatus according to the invention defines the first subset <NUM> of second operational orientation settings (α2; β2) as the preferred subset from which one specific distinct second operational orientation setting (α2; β2) is being selected.

The preferred first subset <NUM> of second operational orientation settings (α2; β2) limit an angle between a first plane in which said first imaging position corresponding to said first operational orientation setting is defined and a second plane in which said second imaging positions corresponding to said second operational orientation settings are defined between a range of <NUM>°-<NUM>°. This is shown in the operational work field <NUM> as a wide curved band.

In <FIG> and <FIG> the white star indicated with reference numeral <NUM> represents the orientation of the imaging means <NUM> in its second imaging position here represented with ANG orientation α2 = <NUM>° and ROT orientation β2 = <NUM>° (CRA <NUM> and LAO <NUM>, see <FIG>). This means that in the second imaging position the imaging device <NUM> would be located approximately at the axis Z (see <FIG>, <FIG> and <FIG>) above the patient <NUM> and the target volume <NUM>'.

This second imaging position is a suggested imaging position and is depicted in an imaginary manner in the first image projection <NUM>' (α1; β1) as displayed in work environment field <NUM> as the oblique white line <NUM>. This line <NUM> defines a plane across the target volume <NUM>' in which the imaging device <NUM> is positioned relative to the patient's body. The white line <NUM> provides a first indication whether the second image projection <NUM>" (α2; β2) being taken in said proposed second imaging position is sufficiently suitable in combination with the first image projection <NUM>' such that after transformation of both image projections the three-dimensional target volume thus reconstructed is usable for analysis and diagnosis purposes.

The method and apparatus according to the invention are capable of selecting the second operational orientation setting from the first subset <NUM> such that said second operational orientation setting corresponds to a second imaging position of the imaging means <NUM>, which second imaging position is clearly distinct from the first imaging position. The second operational orientation setting being selected from the first subset <NUM> is depicted in <FIG> in the work environment field <NUM> as a white star which is shifted within the first subset <NUM> compared to the orientation of the white star <NUM> as shown in <FIG>. In <FIG> and in particular in the work environment field <NUM> the white star is indicated with the reference numeral <NUM>' (α2; β2).

The second image projection being acquired with the imaging means <NUM> positioned in the second imaging position corresponding with the second operational orientation setting <NUM>' (α2; β2) is stored in the storage unit <NUM> via the data communication link 13a and processed by the processing unit <NUM> towards the display unit <NUM> for display in the work environment field <NUM> as depicted in <FIG>. Both the first and the second image projections <NUM>' (α1; β1) and <NUM>" (α2; β2) are depicted next to each other for the user and the transformation means <NUM> process both image projections <NUM>' and <NUM>" in order to acquire the outer contours <NUM>' of the target volume <NUM>'.

In this example the target volume <NUM>' is an artery of the coronary artery system.

The transformation means process both images <NUM>' and <NUM>" for reconstructing a three-dimensional contour image of the target volume <NUM>' which is displayed in work environment field <NUM> in <FIG> and <FIG>. By manipulating the reconstructed three-dimensional contour image of the target volume <NUM>', here an artery, the user or diagnostician is allowed to view the target volume <NUM>' (artery <NUM>') from all sides in order to observe any ailments or affects such as an occlusion <NUM> in the artery.

Thus with the method and apparatus according to the invention it is obviated that two more or less identical (or better less distinct) image projections are acquired and transformed for reconstructing a far less accurate three-dimensional contour image. With such less accurate three-dimensional contour image an incorrect or incomplete analysis and diagnosis would be performed as certain ailments would be become visible in the inaccurate three-dimensional contour image even when the three-dimensional contour image is manipulated and rotated on the display means by the user.

As a further support for selecting the correct second operational orientation setting <NUM>' the method and apparatus according to the invention are arranged in determining a longitudinal orientation of the target volume <NUM>' in said first two-dimensional image projection <NUM>' as depicted in work environment field <NUM> of the display unit <NUM>.

The determination and display of the longitudinal orientation of the target volume <NUM>' is represented with reference numeral <NUM> in <FIG>. In particular in this embodiment the target volume <NUM>' represents an artery of the coronary artery system to be examined. In order to properly define and determine the longitudinal orientation of said artery <NUM>' the method and the apparatus are arranged in defining in said first image projection <NUM>' a first point of interest <NUM> and a second point of interest <NUM>. Both said first and second points of interest are inside the target volume <NUM>' to be examined.

The method and apparatus according to the invention, in particular the display unit <NUM>, are arranged in determining said longitudinal orientation <NUM> of the target volume <NUM>' by interconnecting said first and second point of interest <NUM> and <NUM> respectively.

The method and apparatus according to the invention are assisted in selecting the optimal second operational orientation setting <NUM>' by using the longitudinal orientation <NUM> being determined inside the first image projection <NUM>' of the target volume <NUM>' to be examined. In particular the second operational orientation setting <NUM>' is selected from the first subset <NUM> under the additional condition that the second imaging position corresponding to said second operational orientation setting <NUM>' being selected, is being defined in a plane perpendicular or nearly perpendicular to the longitudinal orientation <NUM> as determined in the target volume <NUM>' under examination.

This additional perpendicular condition is depicted in <FIG> in the work environment field <NUM> as the oblique white line <NUM> defines a plane perpendicular to the longitudinal orientation <NUM> as defined across the target volume <NUM>' (being the longitudinal orientation of the artery under examination). The second operational orientation setting <NUM>' as being selected from the first subset <NUM> corresponds to the second imaging position of the imaging means <NUM>.

As such it can be assured by the method and apparatus according to the invention that the first and second imaging position of the imaging means <NUM> are sufficiently distinct from each other and that therefore no overlapping two-dimensional image projections <NUM>'and <NUM>" are acquired which would render the reconstructed three-dimensional contour image of the target volume <NUM>' as unusable for a proper examination and diagnosis by a user (physician or diagnostician).

In addition, the user can input additional instructions using a pointing or inputting device such as a computer mouse to the display unit <NUM> by selecting and relocating the white star within the work environment field <NUM> and in particular within the set <NUM> of possible second operational orientation setting (within the first and/or second subset <NUM> and <NUM>). Based on said input the apparatus and method according to the invention will provide immediate feedback to the user as to the possible orientation <NUM>' of the imaging means <NUM> relative to the target volume <NUM>'.

As such it can be decided whether said manually relocated second imaging position <NUM>' can be used in real time for acquiring the second image projection to be displayed in work environment field <NUM>. The manual operation of the display unit/means <NUM> by the user is in <FIG> depicted with the reference numeral <NUM>.

With the method and apparatus according to the disclosure J the diagnostician is capable of performing a more accurate diagnosis and subsequent treatment of the patient as the correct second imaging position of the imaging means <NUM> can be determined in advance thereby reducing the imaging treatment session for the patient which is beneficial in terms of reduced radiation exposure time, limited discomfort, etc..

Apart from the length of the image treatment session being reduced also incorrect or unsuitable (meaning overlapping or less distinct) two-dimensional image projections are not acquired and as such an unsuitable three-dimensional contour image is not reconstructed. Also herewith an incorrect analysis and diagnosis of the target volume of the patient by the user is avoided.

Claim 1:
A computer-implemented method for reconstructing a three-dimensional representation of a target volume (<NUM>') inside an animal or human body (<NUM>), said method comprising the steps of:
i) acquiring a first two-dimensional image projection (<NUM>') of said target volume (<NUM>') using imaging means (<NUM>) being positioned in a first imaging position,
ii) acquiring a second two-dimensional image projection (<NUM>") of said target volume (<NUM>') using said imaging means (<NUM>) being positioned in a second imaging position,
iii) reconstructing from said two-dimensional image projections (<NUM>', <NUM>") a three-dimensional contour image of said target volume (<NUM>') using transformation means (<NUM>),
iv) displaying said three-dimensional contour image of said target volume (<NUM>') for a user using displaying means (<NUM>), wherein step ii) is preceded by the additional steps of:
a1) displaying said first two-dimensional image projection (<NUM>') being obtained in step i) for a user using said displaying means (<NUM>), a2) acquiring a first operational orientation setting (α1, β1) of said imaging means (<NUM>) corresponding with said first imaging position;
a3) defining based on said first operational orientation setting (α<NUM>, β<NUM>) a first set (<NUM>) of second operational orientation settings of said imaging means (<NUM>) for orientations in the second imaging position;
a4) determining a longitudinal orientation (<NUM>) of said target volume (<NUM>') in said first two-dimensional image projection (<NUM>');
selecting from said set (<NUM>) one (α<NUM>, β<NUM>) of said second operational orientation settings such that the selected second operational orientation settings (α<NUM>, β<NUM>) corresponds to a second imaging position being defined in a plane perpendicular to said longitudinal orientation (<NUM>) of said target volume (<NUM>');
a5) using said second operational orientation setting (α<NUM>, β<NUM>) being selected for acquiring said second two-dimensional image projection (<NUM>") of said target volume using (<NUM>') said imaging means (<NUM>) being positioned in the second imaging position corresponding to said second operational orientation setting (α<NUM>, β<NUM>).