FIELD OF THE INVENTION

The invention is related to the field of x-ray imaging and more particularly to the field of controlling x-ray radiation amount during multiple frames imaging.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims priority from and is related to U.S. Provisional Patent Application Serial Number 61/914,405, filed 1 1 December 2013, and to U.S. Provisional Patent Application Serial Number 61/927,504, filed 15 January 2014, these U.S. Provisional Patent Applications incorporated by reference in its entirety herein.

BACKGROUND OF THE INVENTION

In a typical multiple frames imaging (MFI) system the x-ray tube generates x-ray radiation over a relatively wide solid angle. To avoid unnecessary exposure to both the patient and the medical team, collimators of x-ray absorbing materials such as lead are used to block the redundant radiation. This way only the necessary solid angle of useful radiation exits the x-ray tube to expose only the necessary elements.

Such collimators are used typically in a static mode but may assume a variety of designs and x-ray radiation geometries. Collimators can be set up manually or automatically using as input, for example, the dimensions of the organ

environment that is involved in the procedure.

In multiple frames imaging, where typically a series of images are taken automatically one after the other, the situation is more dynamic than in a single exposure x-ray.

For such cases collimators with materials partially-transparent to x-ray may be used to manipulate the x-ray energy distribution.

It is desired to change the distribution of the x-ray energy during the MFI session so that for at least 2 different frames of the MFI session the distribution of the x- ray beam will be different.

In MFI the x-ray radiation is active for a relatively long period and the treating physician typically has to stand near the patient, therefore near the x-ray radiation. As a result, it is desired to provide methods to minimize exposure to the medical team. Methods for reducing x-ray radiation intensity have been

suggested where the resultant reduced signal to noise ratio (S/N) of the x-ray image is compensated by digital image enhancement. Other methods suggest a collimator limiting the solid angle of the x-ray radiation to a fraction of the image intensifier area and periodically moving the collimator to expose the entire input area of the image intensifier so that the Region of Interest (ROI) is exposed more than the rest of the area. This way, the ROI receives high enough x-ray radiation to generate a good S/N image while the rest of the image is exposed with low x- ray intensity, providing a relatively low S/N image or reduced real-time imaging, as per the collimator and method used. The ROI size and position can be determined in a plurality of methods. For example, it can be a fixed area in the center of the image or it can be centered automatically about the most active area in the image, this activity is determined by temporal image analysis of sequence of cine images received from the video camera of the multiple frames imaging system.

It is desired to provide collimator solutions to enable reduction of dose during MFI.

It is also desired to provide a method to move the collimator elements so as to support best imaging results.

It is desired to provide a method to handle the effects of this motion on image quality.

A SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a multiple frame imaging system comprising: an x-ray source; a detector having an input area; a monitor configured to display detected images; means for determining the location of at least one Region of Interest (ROI) of a patient on the displayed image; and a collimator comprising means for projecting the at least one region of interest (ROI) on at least one selected fraction of the input area exposed by the x- ray source, the collimator comprising at least three essentially non-overlapping plates mounted in a plane generally parallel to the detector input surface plane, wherein each plate comprises a first edge in contact with an edge of a first neighboring plate and a second edge adjacent to the first edge in contact with an edge of a second neighboring plate; and means for moving each one of the plates in the plane.

One of the plates may be opaque or partially transparent to x-ray radiation and the positioning of the plates may be configured to create a fully transparent area in a gap formed by the essentially non- overlapping plates, for projecting the at least one region of interest (ROI) and a second opaque or partially transparent areas covered by the plates.

The plates may be movable in perpendicular directions.

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Each one of said plates may be connected to a carriage movable by at least one motor and a transmission system along a track.

The at least one motor may comprise a single motor and each one of the plates may be connected to an adjacent plate by a coupler.

Each one of the plates may be movable by an adjacent plate via the coupler. The at least one motor may comprise two motors configured to move the plate in perpendicular directions.

The plates' edges may have a profile selected from the group consisting of:

straight, V-shaped and tapered.

The system may further comprise: an image processing unit connected between the detector and the monitor, the image processing unit configured to optimize the detected image displayed on the monitor according to at least one image parts in the at least one ROI.

The image optimization may comprise determining a tone reproduction function for the image.

The tone reproduction function may be implemented as one of a brightness function, a contrast function, a gamma function, an offset function, an n-degree linear function and a non-linear function.

The image optimization may comprise controlling the x-ray source parameters. The x-ray source parameters may be selected from the group consisting of:

current mode, Peak Kilo Voltage (PKV), pulse length and Automatic Gain Control (AGC).

The collimator may be configured to move in accordance to the zoom setting of the detector and the determined ROI. According to another aspect of the present invention there is provided a collimator comprising: means for projecting at least one region of interest (ROI) on at least one selected fraction of an input area exposed by an x-ray source, a collimator comprising at least three essentially non-overlapping plates mounted in a plane generally parallel to a detector input surface plane, wherein each plate comprises a first edge in contact with an edge of a first neighboring plate and a second edge adjacent to the first edge in contact with an edge of a second neighboring plate; and means for moving each one of the plates in the plane. Each one of the plates may be opaque or partially transparent to x-ray radiation and the positioning of the plates may be configured to create a fully transparent area in a gap formed by the essentially non- overlapping plates, for projecting the at least one region of interest (ROI) and a second opaque or partially transparent area covered by the plates.

The plates may be movable in perpendicular directions.

Each one of the plates may be connected to a carriage movable by at least one motor and a transmission system along a track.

The at least one motor may comprise a single motor and wherein each one of the plates may be connected to an adjacent plate by a coupler.

Each one of the plates may be movable by an adjacent plate via the coupler. The at least one motor may comprise two motors configured to move the plate in perpendicular directions.

The plates' edges may have a profile selected from the group consisting of:

straight, V-shaped and tapered.

According to another aspect of the present invention there is provided a method of controlling a display size of a ROI in an image of an x-ray irradiated area, comprising: providing a multiple frame imaging system comprising: an x-ray source; a detector having an input area; and a collimator comprising means for projecting at least one region of interest (ROI) on a selected fraction of the input area exposed by the x-ray source; the collimator comprising at least three essentially non-overlapping plates mounted in a plane generally parallel to the detector input surface plane, wherein each plate comprises a first edge in contact with an edge of a first neighboring plate and a second edge adjacent to the first edge in contact with an edge of a second neighboring plate; and determining location and size of an exposed area image on the detector input area by moving at least one of the plates in the plane to form a fully transparent gap between the plates.

Each one of the plates may be opaque or partially transparent to x-ray radiation and the positioning of the plates may be configured to create a fully transparent area in a gap formed by the essentially non- overlapping plates, for projecting the at least one region of interest (ROI) and a second opaque or partially transparent areas covered by the plates.

The plates may be movable in perpendicular directions.

Each one of the plates may be connected to a carriage movable by at least one motor and a transmission system along a track.

The at least one motor may comprise a single motor and wherein each one of the plates may be connected to an adjacent plate by a coupler.

Each one of the plates may be movable by an adjacent plate via the coupler. The at least one motor my comprise two motors configured to move the plate in perpendicular directions.

The plates' edges may have a profile selected from the group consisting of:

straight, V-shaped and tapered.

According to another aspect of the present invention there is provided a system for determining the shape and location of at least one Region of Interest (ROI) comprise GUI (Graphical User Interface) means.

The GUI means may comprise means for displaying the detected images and means for determining the at least one ROI size, location and orientation.

The means for determining the at least one ROI size and location may comprise sliders.

The GUI means may comprise means for displaying the detected images and means for determining the at least one ROI size, shape and location.

The means for determining may comprise drawing tools configured to mark an enclosing shape around the at least one ROI.

According to another aspect of the present invention there is provided a method comprising using GUI means for determining the shape and location of at least one Region of Interest (ROI). The GUI means may comprises displaying the detected images and determining the at least one ROI size, location and orientation.

Determining the at least one ROI size and location may comprise moving sliders. The GUI means may comprise displaying the detected images and determining the at least one ROI size, shape and location.

Determining may comprise drawing enclosing shape around the at least one ROI. According to another aspect of the present invention there is provided a multiple frame imaging system comprising: a radiation source; a detector having an input area; a monitor configured to display detected images; means for determining at least one Region of Interest (ROI) of an object on a displayed image; a first collimator; a second collimator mounted between said first collimator and said object ; a radiation controller configured to control said radiation source; and a second collimator controller.

The radiation source may comprise an x-ray source.

The monitor may be configured to display detected images obtained through at least one of said first and second collimators.

The system may further comprise connection means configured to connect said first collimator with said second collimator.

The connection means may comprise a mechanical connector connected to one of the c-arm, the original collimator cover, the radiation tube cover, the c-arm cabinet and a plate with wheels mounted on the floor .

The system may further comprise a robotic arm configured to drive said second collimator.

The robotic arm may be directed by sensors configure to ensure that said second collimator is mounted in coordination with said first collimator.

The system may further comprise a first collimator controller and a robotic arm controller.

The first collimator controller may be connected with said robotic arm controller and is configured to direct said robotic arm.

The means for determining may comprise one of a joy stick, a keyboard and a touch screen.

The system may further comprise a rotary motor configured to enable the plate to rotate in a plane generally parallel to the detector input surface plane. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood in reference to the following Figures:

Figure 1 A is a simplified schematic illustration of an exemplary layout of a multiple frames imaging clinical environment and system;

Figure 1 B is an illustration of an exemplary layout of the system of Figure 1 A showing additional details of components of the system example of the invention; Figure 2 is a schematic illustration of an exemplary image displayed on a monitor of a multiple frames imaging system;

Figure 3 is a simplified schematic illustration of an exemplary layout of a multiple frames imaging clinical environment and system with the addition of an input device;

Figure 4 is a top view of a collimator constructed of four partially x-ray transparent essentially non-overlapping plates with the ROI at the center;

Figure 4.1 shows an example of possible arrangement of nut 4501 E;

Figure 4A is a top view of the collimator of Figure 4 with the ROI at an off-center location;

Figure 5 illustrates the x-ray intensity distribution in different areas of the image when the ROI is at the center;

Figure 6 is a top view of another example of a collimator constructed of four partially x-ray transparent essentially non-overlapping plates with the ROI at the center;

Figure 6A is a top view of the collimator of Figure 6 with the ROI at an off-center location;

Figure 7 is a top view of another example of a collimator constructed of four x-ray partially transparent essentially non-overlapping plates with the ROI at the center; Figure 7A is a top view of the collimator of Figure 7 with the ROI at an off-center location;

Figure 8 is a top view of another example of a collimator constructed of three x- ray partially transparent essentially non-overlapping plates with the ROI at the center; Figure 8A is a top view of the collimator of Figure 8 with the ROI at an off-center location;

Figure 9 is a top view of another example of a collimator constructed of five x-ray partially transparent essentially non-overlapping plates with the ROI at the center; Figure 9A is a top view of the collimator of Figure 9 with the ROI at an off-center location;

Figure 9B is a top view of the collimator of Figure 9 with a different ROI at the center;

Figure 9C is a top view of the collimator of Figure 9 with a different ROI at the center;

Figure 10 is a top view of another example of a collimator constructed of twelve x-ray partially transparent essentially non-overlapping plates with the ROI at the center;

Figure 10A is a top view of an enlargement of the components of the motorizing elements of the collimator of Figure 10;

Figure 10B is a top view of the collimator of Figure 10 with the ROI at an off- center location;

Figure 10C is a top view of the collimator of Figure 10 with the ROI at the center; Figure 1 1 is a top view of a collimator constructed of four x-ray partially

transparent essentially non-overlapping plates with the ROI at an off-center location;

Figure 1 1 A is a top view of the collimator of Figure 1 1 with the ROI at the center; Figure 12A demonstrates the use of "straight edge" plates and the resulting image with the x-ray radiation penetration;

Figure 12B demonstrates the use of "V shaped edge" plates and the resulting image;

Figure 12C demonstrates the use of "tapered edge" plates and the resulting image;

Figure 12D demonstrates coupling when two filters are not at the same distance from the radiation source;

Figure 12E also demonstrates coupling when two filters are not at the same distance from the radiation source; Figure 13 shows an exemplary user interface which may be implemented as part of a control application;

Figure 13A is another example of a user interface and automatic ROI setup; Figure 13B is another example of possible shape drawing and automatic ROI setup using the user interface of Figure 13A;

Figure 13C is another example of possible shapes drawing and automatic ROI setup using the user interface of Figure 13A;

Figure 13D is another example of possible shapes drawing and automatic ROI setup using the user interface of Figure 13A;

Figure 13E is another example of possible shapes drawing and automatic ROI setup using the user interface of Figure 13A;

Figure 13F is another example of possible shapes drawing and automatic ROI setup using the user interface of Figure 13A;

Figure 13G is another example of possible shapes drawing and automatic ROI setup using the user interface of Figure 13A;

Figure 14 depicts schematically an existing system with the additional collimator that is mechanically connected;

Figure 15 depicts schematically an existing system with the additional collimator that is driven by a robotic arm;

Figure 16 is an example of a mechanical connection;

Figure 16A is a top view of the system of figure 16;

Figure 17 is another example of a mechanical connection;

Figure 17A is a side view of the system of figure 17;

Figure 17B is another side view of the system of figure 17;

Figure 18 is another example of a mechanical connection;

Figure 18A is an example of a rotated collimator of the system of figure 17;

Figure 19 is another example of a mechanical connection; and

Figure 19A is a side view of the system of figure 19.

DETAILED DESCRIPTION OF THE INVENTION

Throughout the following description reference is made to various collimators having plates or filters. Both terms are used in the same sense, to describe filters intended to change the intensity of the radiation in a non-uniform manner over the Field of View (FOV), as opposed to filters intended for changing the spectrum of the radiation throughout the FOV.

Reference is made now to Figure 1 A which presents a typical layout of a multiple frames imaging clinical environment.

X-ray tube 100 generates x-ray radiation 102 directed upward occupying a relatively large solid angle towards a collimator 104. Collimator 104 blocks a part of the radiation allowing a smaller solid angle of radiation to continue in the upward direction, go through bed 108 that is typically made of material that is relatively transparent to x-ray radiation and through patient 1 10 who is lying on bed 108. Part of the radiation is absorbed and scattered by the patient and the remaining radiation arrives at the typically round input area 1 12 of image intensifier 1 14. The input area of the image intensifier is typically in the order of 300mm in diameter but may vary per the model and technology. The image generated by image intensifier 1 14 is captured by camera 1 16, processed by image processor 1 17 and then displayed on monitor 1 18 as image 120.

Although the invention is described mainly in reference to the combination of image intensifier 1 14 and camera 1 16 it would be appreciated that both these elements can be replaced by a digital radiography sensor of any technology such as CCD or CMOS flat panels or other technologies such as Amorphous Silicon with scintillators located at plane 1 12. One such example is CXDI-50RF Available from Canon U.S.A., Inc., Lake Success, NY. The term "detector" is used to include any of these technologies, including the combination of any image intensifier with any camera and including any type of a flat panel sensor or any other device converting x-ray to electronic signal.

The terms "area" and "region" are used alternatively in the detailed description of the invention and they mean the same and are used as synonyms.

The term "x-ray source" is used to provide a wide interpretation for a device having x-ray point source that does not necessarily have the shape of a tube. Although the term x-ray tube is used in the examples of the invention in convention with common terminology in the art, it is represented here that the examples of the invention are not limited to a narrow interpretation of x-ray tube and that any x-ray source can be used in these examples (for example even radioactive material configured to function as a point source). Operator 122 is standing by the patient to perform the medical procedure while watching image 120.

The operator has a foot-switch 124. When pressing the switch, continuous x-ray radiation (or relatively high frequency pulsed x-ray as explained below) is emitted to provide a cine imaging 120. The intensity of x-ray radiation is typically optimized in a tradeoff of low intensity that is desired to reduce exposure to the patient and the operator and high intensity radiation that is desired to enable a high quality image 120 (high S/N). With low intensity x-ray radiation and thus low exposure of the image intensifier input area, the S/N of image 120 might be so low that image 120 becomes useless.

Coordinate system 126 is a reference Cartesian coordinate system with Y axis pointing into the page and X-Y is a plane parallel to planes such as that of collimator 104 and image intensifier input plane 1 12.

It is a purpose of the present invention to provide high exposure at the input area of the image intensifier in the desired one or more ROIs that provide therefore a high S/N image there while reducing the exposure of other sections of the image intensifier area, at the cost of lower image quality (lower S/N). With this

arrangement the operator can see a clear image in the one or more ROIs and get a good enough image for general orientation in the rest of the image area. It is also a purpose of this invention to provide more complex map of segments in the image where each segment results from a different level of x-ray radiation as desired by the specific application.

According to some embodiments, the x-ray system may include multiple filament elements to generate multiple and simultaneous X Ray beams, a subset of which may be selected and may be configured to modify the x-ray radiation in order to aim at the desired ROIs in the field of view according to the location of the operator's focus of attention.

According to some embodiments, the x-ray system may include a matrix/array of x ray tubes/sources to generate multiple and simultaneous X Ray beams, a subset of which may be selected and may be configured to modify the x-ray radiation in order to aim at the desired ROIs in the field of view according to the location of the operator's focus of attention. According to some embodiments, the x-ray system may further include rotatable and translatable cathodes and/or anodes to generate multiple and simultaneous X Ray beams, a subset of which may be selected and may be configured to modify the x-ray radiation in order to aim at the desired ROIs in the field of view according to the location of the operator's focus of attention.

An example of a more detailed layout of a multiple frames imaging clinical environment according to the present invention is described in Figure 1 B.

Operator 122 presses foot switch 124 to activate the x-ray. Input device 128 provides indication of one or more ROIs. This information is typically provided relative to monitor 1 18. This information, the at least one desired center of ROI, may be provided for example in terms of (X,Z) coordinates, in the plane of monitor 1 18, using coordinate system 126. It would be appreciated that in this example the plane of monitor 1 18 and therefore also image 120 are parallel to the (X,Z) plane of coordinate system 126. Other coordinate systems are possible, including coordinate systems that are bundled to monitor 1 18 and rotate with monitor 1 18 when it is rotated relative to coordinate system 126.

The data from input 128 is provided to controller 127 which is basically a computer, such as any PC computer.

Box 150 in Figure 1 B represents a collimator according to the present invention, for example, the collimator of Figures 4 through 1 1 .

Box 150 can be located under collimator 104, above collimator 104 as shown by numerical reference 150A or instead of collimator 104 (not shown in Figure 1 B). The collimators represented by boxes 150 and 150A are controlled by controller 127. X-ray emission is also controlled by controller 127, typically through x-ray controller 130. The collimator partially blocks radiation, depending on the determined at least one desired center of ROI (step 2720). Part of the x-rays are absorbed by the patient 1 10 (step 2730) and the remaining radiation arrives at the image intensifier 1 14 (step 2740). In step 2750 the image is intensified and captured by a camera 1 16 and in step 2760 the captured image is transferred to the image processor 1 17 and in step 2770 the processed image is displayed on monitor 120. Image processor 1 17 may assume many forms and may be incorporated in the current invention in different ways. In the example of Figure 1 B, image processor 1 17 includes two main sub units: 1 17A provides basic image correction such as pixel non-uniformity (dark offset, sensitivity, reconstruction of dead pixels etc), 1 17C provides image enhancement processing (such as noise reduction, un- sharp masking, gamma correction etc). In conventional systems, the image from sub-unit 1 17A is transferred for further processing in sub-unit 1 17C. The sub- units of image processor 1 17 can be supported each by a dedicated hardware but they can also be logical sub-units that are supported by any hardware.

In the example of Figure 1 B the image from camera 1 16 is corrected by image processing sub-unit 1 17A and then transferred to controller 127. Controller 127 processes the image as required from using any of the collimators represented by box 150 and returns the processed image to sub-unit 1 17C for image enhancement.

It would be appreciated that the image processing of controller 127 does not have to take place in controller 127 and it can be executed by a third sub-unit 1 17B (not shown in Figure 1 B) located between 1 17A and 1 17C. Sub-unit 1 17B can also be only a logical process performed anywhere in image processor 1 17. It would also be appreciated that x-ray controller 130 is presented here in the broad sense of system controller. As such it may also communicate with image processor 1 17 to determine its operating parameters and receive information as shown by communication line 132, It may control image intensifier 1 14, for example for zoom parameters (communication line not shown), it may control camera 1 16 parameters (communication line not shown), it may control the c-arm and bed position (communication line not shown) and it may control x-ray tube 100 and collimator 104 operation parameters (communication line not shown). There may be a user interface for operator 122 or other staff members to input requests or any other needs to x-ray controller 130 (not shown).

Physically, part or all of image processor 1 17, controller 127 and x-ray generator (the electrical unit that drives x-ray tube 100) may all be included in x-ray controller 130. X-ray controller 130 may contain one or more computers and suitable software to support the required functionality. An example for such a system with an x-ray controller is mobile c-arm OEC 9900 Elite available from GE OEC Medical Systems, Inc., Salt Lake City, UT USA. It would be appreciated that the exemplary system is not identical to the system of Figure 1 B and is only provided as a general example. Some of these features are shown in Figure 3. Reference is made now to Figure 2 illustrating an example of an image 120 displayed on monitor 1 18. In this example dashed circle line 204 indicates the border between segment 200 of the image and segment 202 of the image, both segments constitute the entire image 120. In this example it is desired to get a good image quality in segment 200, meaning higher x-ray DPP for segment 200 and it is acceptable to have a lower image quality in segment 202, meaning lower DPP for segment 202.

It would be appreciated that the two segments 200 and 202 are provided here only as one example of an embodiment of the invention that is not limited to this example and that image 120 can be divided to any set of segments by controlling the shape of the apertures in the collimators and mode of motion of the

collimators. Such examples are provided below.

It would be appreciated that DPP should be interpreted as the x-ray dose delivered towards a segment representing one pixel of image 120 to generate the pixel readout value used to construct image 120 (excluding absorption by the patient or other elements which are not a part of the system, such as the hands and tools of the operator).

As explained above, pixels with different DPP per the collimator design and use are normalized to provide a proper display-frame. Normalization scheme is made in accordance with the x-ray exposure scheme (i.e., collimator shape, speed and position). Such normalization can be done on the basis of theoretical parameters.

Collimators according to this invention can be mounted on an x-ray system as stand-alone or together with another collimator, for example, such that is designed to limit the x-ray to a part of input area 1 12 of the image intensifier. Collimators of the invention and other collimators may be placed in any order along the x-ray path. The exposed part of area 1 12 is the remaining of the superposition of the area of all the collimators in the path of the x-ray block. In the design of such successive arrangement, the distances of each of the collimators from the x-ray source and distance to area 1 12 needs to be considered with the geometry of the collimators, as described above, to get the desired functionality.

In the present example, the at least one ROI becomes the area used for image optimization. The input device, provides the ROI coordinates of the at least one user on the screen. The ROIs are moved to these coordinates, with a

complementary adjustment of the collimator and the optimization is made for the image included in the ROIs .

The image may be optimized per the ROIs' content using any of the above mentioned parameters or any other parameter that modifies the displayed value of a pixel in the image.

Attention is drawn now to Figure 3 which presents an exemplary system for carrying out the invention.

Typically in x-ray systems, an ROI that is centered in image 120 (such as ROI 200 of Figure 2) and has a fixed position is used for image analysis and for generating parameters to drive x-ray tube 100 and modify image 120.

Parameters such as average value, maximum value and contrast may be calculated for this area. Such parameters are typically used to optimize the x-ray tube operation (such as mA, mAs and KVp).

In this example an input device 127 is used to provide x-ray controller 130 with the ROI coordinates of one or more users 122.

The input device can be any input device that affects the position and/or the shape of the ROI. For example, an eye tracker, a joy-stick, a keyboard, an interactive display, a gesture reading device, a voice interpreter or any other suitable device can be used to determine coordinates relative to image 120, and the ROI position and/or shape changes according to such input.

According to embodiments of the invention, some of the input devices may need a user interface 129.

The user interface can have any display, operated by any computer or tablet, use mouse, trackball or touch-screen, joystick or hand gesture to control the selection of the ROI. The following examples, demonstrated in Figs. 4 through 1 1 , present collimators for collimating x-ray radiation in x-ray systems comprising a displayed image of the irradiated area. The systems share the following characteristics:

- A first part of the image represents the ROI: unfiltered radiation section (100% of the radiation arriving at the collimator plates)

- A second part of the image is background, where radiation is filtered by the collimator plates (100%>radiation>0 of the radiation arriving at the collimator plates)

- The background filter comprises at least three separate filters

- The background image area comprises at least one point at one filter area of the image and at least one point at a second filter area of the image;

- There is at least one contour, connecting these two points,

wherein, the radiation along the contour encounters essentially the same filtering characteristics (same total filtering thickness for example, of filters of a uniform material composition).

For simplicity, a straight line connecting these two points can be considered for the description, but it should be appreciated that changing filtration

characterization along this line due to changing angle of incidence of the radiation (and therefore the effective thickness) is particularly considered, in the scope of this invention, as essentially the same filtering characterization. Same is for any of the contour or the straight line, in regard to non-uniformity of the filter thickness, material homogeneity etc., typically present as a result of

manufacturing accuracy limitations, they are all included in "essentially the same" terminology..

This includes also filters that are not at the same height or without touching edges etc. They are still coupled but the distance between the edges may change according to the position (incidence angle). This will be explained in more details in conjunction with Figures 12D and 12E.

Also, when using the term "uniform" in reference to filtering, the scope of uniform includes such tolerances as described above.

Essentially non-overlapping filters means a design that is intended to support the above system characteristics in at least most of the image area. A small overlapping that, for example results in extra filtering along overlapping edges of two adjacent filters would still be included in "essentially non-overlapping"

Reference is made now to Figure 4 providing an exemplary collimator 4500 according to the present invention.

Collimator 4500 comprises four plates 4501 , 4502, 4503 and 4504 that are opaque or partially transparent to x-ray. In this example we shall assume that each such plate transmits 10% of beam 106 but it would be appreciated that other transmission levels may be contemplated. Plates 4501 , 4502, 4503 and 4504 can be made from any suitable material, considering the desired effect of the spectral distribution of the transmitted x-ray beam. For example, copper or aluminum plates can be used.

Dashed circle 106A (Figure 4A) represents x-ray cone 106 cross section at generally the plane of collimator 4500. Except for a rectangular shaped x-ray beam portion 3510 (Figure 4A), the rest of the beam intensity is reduced due to plates 4501 , 4502, 4503 and 4504.

Eight motors can move plates 4501 , 4502, 4503 and 4504 as explained below. The components of the motorizing elements are detailed in reference to plate 4501 . The other 3 plates' mechanisms are analogous.

Motor 4501 A drives screw 4501 C that moves nut 4501 E. Nut 4501 E is connected to plate 4501 , therefore enables plate 4501 to move in the directions of arrow 4501 F.

Motor 4501 B drives screw 4501 D that moves nut 4501 E. Nut 4501 E is connected to plate 4501 therefore enables plate 4501 to move in directions of arrow 4501 G. Hence, each plate can move as indicated by dual-head arrows for each plate, independently of the other plates. An example of possible arrangement of nut 4501 E is shown in Fig. 4.1 . Rails 4505A may be used to support the plates and enable motion. Motors 4501 A and 4501 B slide freely on the rails 4505A according to the mentioned directions.

It would be appreciated that the specific motion mechanism described herein is provided to explain the invention and that the scope of the invention is not limited to this motion mechanism. To create a rectangular ROI each one of two adjacent edges of a filter (plate) is parallel and in contact with the edge of a neighboring filter as demonstrated in Fig. 4.

The collimator 4500 is based on "active coupling", meaning the controller of the motors has to ensure coupling of the plates where coupling of two plates means they are in contact along at least a part of an edge.

As mentioned above, each plate is able to move independently but in order to prevent radiation penetration between the plates the controller ensures that when a plate moves in direction perpendicular to a coupling line, the adjacent plate coupled along this line moves with it and thus coupling is maintained. Namely, when one motor needs to be moved, the controller may move other motors as well, to maintain plates coupling.

It would be appreciated that coupling is not required at all times and it is typically preferred to have the coupling at least when radiation is turned on.

It is appreciated that a circular image / circular cone shape x-ray beam is only an example. The x-ray beam and the image may be rectangular or any other shape, depending on the c-arm and collimator setup.

In the example of Figure 4A aperture 3512 is in the region of beam 106 (as shown by the beam cross section 106A) and has a certain size dictated by the required ROI. Figure 4A demonstrates an adjustment of plates 4501 , 4502, 4503 and 4504 in order to create the required aperture for providing radiation to the ROI that is different from the ROI example shape of Figure 4.

With this example of collimator 4500 therefore ROI 3602 of image 120 (Figure 5) cannot only be moved across the area of image 120 to the desired location but also the size and aspect ratio of the ROI can be changed as desired, to compensate for zoom in image intensifier 1 14 (Figure 1A) or for other reasons.

Reference is made now to Figure 5, illustrating the x-ray intensity distribution in different areas of image 120 when the image ROI 3602 is in the position resulting from mechanical ROI 3512 presented in Figure 4A. In this example there is no object (patient) between collimator 4500 and input area 1 12 so, ideally, without additional conventional collimator blocking radiation, the x-ray radiation over input area 1 12, outside of the ROI, would be uniform (up to specific system inherent uniformity limitations). In this example, as a result of collimator 4500 the area of image 120 is divided into two intensity areas: 3602, the ROI, where the original 100% intensity is and 3604A where the intensity is 10% of that at the ROI.

The above described methods to correct background are fully applicable to correct the background 3604A of the present example.

It would be appreciated therefore that the current example can be used together with the above described correction methods.

Reference is made now to Figure 6 providing an example of collimator 4700 according to the present invention.

Collimator 4700 uses four motors instead of the eight motors used in the configuration of Fig. 4.

The components of the motorizing elements are detailed in reference to plate 4701 . The other 3 plates' mechanisms are analogous.

Motor 4701 A drives screw 4701 B that moves nut 4701 C. Nut 4701 C is connected to plate 4701 , therefore enables plate 4701 to move in the directions of arrow 4701 D.

An "L" shaped coupler 4705 connects plates 4701 and 4704 wherein nut 4701 C slides on the coupler side 4705A and plate 4704 is fixedly connected to the other side 4705B of the coupler via a connector 4706.

Therefore, as plate 4701 moves in the directions of arrow 4701 D, plate 4704 moves with it in the same direction but in order to move in the directions of arrow 4701 E, plate 4702 moves and moves plate 4701 with it.

Hence, according to this configuration, a single plate cannot move without causing movement of another plate.

The collimator 4700 is based on "passive coupling" meaning the "L" shaped couplers ensure coupling of the plates by forcing two adjacent edges of neighboring plates to maintain their relative positions by sliding along each other. The four motors slide freely on the rails 4505B according to the mentioned directions. It would be appreciated that some of the plates may be movable by one motor and a coupler and some plates may be movable by two motors.

In that case an "active coupling" is needed in addition to the "passive coupling".

It would be appreciated that the specific motion mechanism described herein is provided to explain the invention and that the scope of the invention is not limited to this motion mechanism.

To create a rectangular ROI each of two adjacent edges of a filter (plate) is parallel and in contact with the edge of a neighboring filter.

Reference is made now to Figure 6A.

Figure 6A demonstrates an adjustment of plates 4701 , 4702, 4703 and 4704 in order to create the aperture for providing radiation to the ROI.

With this example of collimator 4700 therefore the ROI of image 120 can not only be moved across the area of image 120 to the desired location but also the size and aspect ratio of the ROI can be changed as desired, to compensate for zoom in image intensifier 1 14 or for other reasons.

Reference is made now to Figure 7 providing an example of collimator 4800 of the present invention.

Collimator 4800 also uses four motors instead of eight.

The components of the motorizing elements are detailed in reference to plate

4801 . The other 3 plates' mechanisms are analogous.

Motor 4801 A drives screw 4801 B that moves nut 4801 C. Nut 4801 C is connected to plate 4801 therefore enables plate 4801 to move in the directions of arrow 4801 D.

A "U" shaped coupler 4805 connects plates 4801 and 4804 wherein nut 4801 C slides on the coupler side 4805A and nut 4804A slides on the coupler side 4805B. The connector 4806 is fixedly connected to the rail 4505C and allows the coupler to slide through it.

The "U" shaped coupler dictates the motion limitations and ensures plates' coupling. Therefore, as plate 4801 moves in the directions of arrow 4801 D, plate 4804 moves with it in the same direction but in order to move in the directions of arrow 4801 E, plate 4802 moves and moves plate 4801 with it.

Hence, according to this configuration, a single plate cannot move without causing movement of another plate.

The collimator 4800 is based on "passive coupling" meaning the "U" shaped coupler ensures coupling of the plates by forcing two adjacent edges of neighboring plates to maintain their relative positions by sliding along each other. The motors slide freely on the rails 4505C according to the mentioned directions. It would be appreciated that some of the plates may be movable by one motor and a coupler and some plates may be movable by two motors.

In that case an "active coupling" is needed in addition to the "passive coupling". It would be appreciated that the specific motion mechanism described herein is provided to explain the invention and that the scope of the invention is not limited to this motion mechanism.

To create a rectangular ROI each of two adjacent edges of a filter (plate) is parallel and in contact with the edge of a neighboring filter.

Reference is made now to Figure 7A.

In the example of Figure 7 A aperture 3512 is at the region of beam 106 (as shown by the beam cross section 106A) and it has a certain size.

Figure 7 A demonstrates an adjustment of plates 4801 , 4802, 4803 and 4804 in order to create the aperture for providing radiation to the ROI.

With this example of collimator 4800 therefore the ROI of image 120 can not only be moved across the area of image 120 to the desired location but also the size and aspect ratio of the ROI can be changed as desired, to compensate for zoom in image intensifier 1 14 or for other reasons.

Reference is made now to Figure 1 1 providing an example of collimator 5400 of the present invention.

Collimator 5400 also uses four motors instead of eight.

The components of the motorizing elements are detailed in reference to plate

5401 . The other 3 plates' mechanisms are analogous. Motor 5401 A moves on rail 4505G and connects plates 5401 and 5402 via couplers 5402A and 5402B and nuts 5401 B and 5401 C respectively, thereby enabling plate 5401 to move in the directions of arrow 5401 D.

The nuts 5401 B and 5401 C slide freely on the couplers 5402A and 5402B respectively. The couplers 5402A and 5402B dictate the motion limitations and ensure plates' coupling.

Therefore, as plate 5401 moves in the directions of arrow 5401 D, plate 5402 moves with it in the same direction but in order to move in directions of arrow 5401 E, plate 5404 moves and moves plate 5401 with it.

Hence, according to this configuration, a single plate cannot move without causing movement of another plate.

The collimator 5400 is based on "passive coupling" meaning the couplers 5402A and 5402B ensure coupling of the plates by forcing two adjacent edges of neighbor filters to maintain the distance between them by sliding along each other.

The motors slide on the rails 4505G according to the mentioned directions.

It would be appreciated that the specific motion mechanism described herein is provided to explain the invention and that the scope of the invention is not limited to this motion mechanism.

To create a rectangular ROI each of two adjacent edges of a filter (plate) is parallel and in contact with the edge of a neighboring filter.

Reference is made now to Figure 1 1 A.

In the example of Figure 1 1A aperture 3512 is at the region of beam 106 (as shown by the beam cross section 106A) and it has a certain size.

Figure 1 1 A demonstrates an adjustment of plates 5401 , 5402, 5403 and 5404 in order to create the aperture for providing radiation to the ROI.

With this example of collimator 5400 therefore the ROI of image 120 can not only be moved across the area of image 120 to the desired location but also the size and aspect ratio of the ROI can be changed as desired, to compensate for zoom in image intensifier 1 14 or for other reasons.

Reference is made now to Figure 8 providing an example of collimator 4900 of the present invention. Collimator 4900 has three filters (plates) and uses three motors.

The components of the motorizing elements are detailed in reference to plate

4901 . The other two plates' mechanisms are analogous.

Motor 4901 A drives screw 4901 B that moves nut 4901 C. Nut 4901 C is connected to plate 4901 therefore enables plate 4901 to move in the directions of arrow 4901 F.

A "U" shaped coupler 4905 connects plates 4901 and 4902 wherein nut 4901 E slides on the coupler side 4905A and nut 4902A slides on the coupler side 4905B.

The "U" shaped coupler dictates the motion limitations and ensure plates' coupling.

Therefore, as plate 4901 moves in directions of arrow 4901 F, plate 4903 moves with it in the directions of arrow 4903A but in order to move in the directions of arrow 4901 D, plate 4902 moves in the directions of arrow 4903A and moves plate 4901 with it.

Hence, according to this configuration, a single plate cannot move without causing movement of another plate. Therefore, when the controller moves one motor, other motors may need to move.

The collimator 4900 is based on "passive coupling" meaning the couplers 5402A and 5402B ensure coupling of the plates by forcing two adjacent edges of neighbor filters to maintain the distance between them by sliding along each other.

The motors slide freely on the rails 4505D according to the mentioned directions. It would be appreciated that some of the plates may be movable by one motor and a coupler and some plates may be movable by two motors.

In that case an "active coupling" is needed in addition to the "passive coupling". It would be appreciated that the specific motion mechanism described herein is provided to explain the invention and that the scope of the invention is not limited to this motion mechanism.

Reference is made now to Figure 8A. Figure 8A demonstrates an adjustment of plates 4901 , 4902 and 4903 in order to create the aperture for providing radiation to the ROI.

With this example of collimator 4900 therefore the ROI of image 120 can not only be moved across the area of image 120 to the desired location but also the size and aspect ratio of the ROI can be changed as desired, to compensate for zoom in image intensifier 1 14 or for other reasons.

Reference is made now to Figure 9 providing an example of collimator 5000 of the present invention.

Collimator 5000 has five plates (filters) and uses five motors.

The components of the motorizing elements are detailed in reference to plate

5001 . The other four plates' mechanisms are analogous.

Motor 5001 A drives screw 5001 B that moves nut 5001 C. Nut 5001 C is connected to plate 5001 thus enabling plate 5001 to move in the directions of arrow 5001 D. A "U" shaped coupler 5006 connects plates 5001 and 5002 wherein nut 5001 E slides on the coupler side 5006A and nut 5002A slides on the coupler side 5006B.

The "U" shaped coupler dictates the motion limitations and ensure plates' coupling.

Therefore, as plate 5001 moves in directions of arrow 5001 D, plate 5002 moves with it in the directions of arrow 5002B but in order to move in the directions of arrow 5001 F, plate 5005 moves and moves plate 5001 with it.

Hence, according to this configuration, a single plate cannot move without causing movement of another plate. Therefore, when the controller moves one motor, other motors may need to move.

The collimator 5000 is based on "passive coupling" meaning the "U" shaped couplers ensure coupling of the plates by forcing two adjacent edges of neighbor filters to maintain the distance between them by sliding along each other.

The motors slide freely on the rails 4505E according to the mentioned directions.

It would be appreciated that some of the plates may be movable by one motor and a coupler and some plates may be movable by two motors.

In that case an "active coupling" is needed in addition to the "passive coupling". It would be appreciated that the specific motion mechanism described herein is provided to explain the invention and that the scope of the invention is not limited to this motion mechanism.

Reference is made now to Figure 9A through 9C.

In the examples of Figures 9A, 9B and 9C aperture 3512 is at the region of beam

106 (as shown by the beam cross section 106A) and it has a certain size.

Figure 9A demonstrates an adjustment of plates 5001 , 5002, 5003, 5004 and

5005 in order to create a specific needed pentagonal ROI.

Figure 9B demonstrates an adjustment of plates 5001 , 5002, 5003, 5004 and

5005 in order to create a specific needed quadrangular ROI.

Figure 9C demonstrates an adjustment of plates 5001 , 5002, 5003, 5004 and

5005 in order to create a specific needed triangular ROI.

Reference is made now to Figure 10 providing an example of collimator 5100 of the present invention.

Collimator 5100 has twelve plates (filters) and uses twelve motors.

Figure 10A shows an enlargement of the components of the motorizing elements that are detailed in reference to plate 5101 . The other eleven plates' mechanisms are analogous.

Motor 5101 A drives screw 5101 B that moves nut 5101 C. Nut 5101 C is connected to plate 5101 thus enabling plate 5101 to move in the directions of arrow 5101 D. A "U" shaped coupler 5106 connects plates 5101 and 5102 wherein nut 5101 E slides on the coupler side 5106A and nut 5102A slides on the coupler side 5106B.

The "U" shaped coupler dictates the motion limitations and ensures plates' coupling.

Therefore, as plate 5101 moves in the directions of arrow 5101 D, plate 5102 moves with it in the same direction but in order to move in directions of arrow 5101 F, plate 51 12 moves and moves plate 5101 with it.

Hence, according to this configuration, a single plate cannot move without causing movement of another plate. Therefore, when the controller moves one motor, other motors may need to move. The collimator 5100 is based on "passive coupling" meaning the "U" shaped couplers ensure coupling of the plates by forcing two adjacent edges of neighbor filters to maintain the distance between them by sliding along each other.

The motors slide freely on the rails 4505F according to the mentioned directions. It would be appreciated that some of the plates may be movable by one motor and a coupler and some plates may be movable by two motors.

In that case an "active coupling" is needed in addition to the "passive coupling". It would be appreciated that the specific motion mechanism described herein is provided to explain the invention and that the scope of the invention is not limited to this motion mechanism.

Reference is made now to Figures 10B and 10C

Figures 10B and 10C demonstrate an adjustment of plates 5101 through 51 12 in order to create a specific ROI such as 3512B and 3512C.

The concept is expandable to any number of plates > 2.

All the examples shown can also be placed on a rotatable and/or displaceable mechanism in x-y plane. Rotation is particularly useful for solutions with relatively small number of plates (such as 3, 4 and 5). 12 plates virtually eliminate the need for rotation.

A problem that may occur while using the "essentially non-overlapping filters" collimators aforementioned is a penetration of X-Ray radiation between the collimator plates.

Figure 12A demonstrates the use of "straight edge" plates with radiation beam

5320 penetrating the filtering layer through a small gap between plates 5322 and

5324. This makes the line along which the two plates meet visible on the image as illustrated on resulting image 5326.

Figures 12B and 12C offer two solutions to the problem.

Figure 12B demonstrates the use of "V shaped edge" plate with a negative or reversed V edge plate fitting each other so that ray 5320A cannot pass through the line of plates contact without being filtered. The resulting image 5326A without the effect of radiation un-intended penetration is shown. Figure 12C demonstrates the use of "tapered edge" plates and the resulting image.

Other edge shapes are considered, such as arcuate, concave, convex, contoured, or stepped, or any complementary, mating edge shape that effectively prevent line-of sight through the abutting plates along the primary direction of beam travel.

Figures 12D and 12E provide another example for the coupling concept of the present invention. For this example, plates 5302 and 5304 of Figure 12C are used. Unlike Figure 12C where plates 5302 and 5304 are at the same plane, in Figures 12D and 12E plates 5302 and 5304 are not in the same plane. Plate 5304 is further away from radiation source 5306, in direction perpendicular to the planes of plates 5302 and 5304.

In Figure 12D plates 5302 and 5304 are shown to the right of radiation source 5306. The horizontal distance between plates 5302 and 5304 is set so that radiation rays passing through each of the filters and in the zone including both filters experience essentially the same filtering. In this example ray 531 1 is passing through plate 5302 only, ray 5313 is passing through plate 5304 only and ray 5312 passes through both plates 5302 and 5304. The horizontal distance between plates 5302 and 5304 is set so that all 3 rays experience essentially the same thickness of filtering.

In Figure 12E plates 5302 and 5304 are shownto the left of radiation source 5306. Ray 531 1 A passes through plate 5302 only, ray 5313A passes through plate 5304 only and ray 5312A passes through both plates 5302 and 5304. The horizontal distance between plates 5302 and 5304 is set so that all 3 rays experience essentially the same thickness of filtering. Note that the horizontal distance between plates 5302 and 5304 in Figure 12E is smaller than in Figure 12D. This is because the change in the angle of incidence of the radiation rays. This demonstrates the concept of plates that are "coupled" in this invention. They are coupled in the sense of a constraint, requiring that the distance between the plates serves the purpose of essentially uniform filtering on a transition from one plate to another and not, for example, mechanical fixed distance (although mechanical fixed distance can serve as the desired coupling implementation for certain mechanical designs). It would be appreciated that the specific examples described here are provided to explain the invention and that the scope of the invention is not limited to these specific solutions.

It would be appreciated that although the above was described in reference to an image intensifier it is applicable to any detector, including a flat panel detector. The geometry of the detector, the zoom area and the ROI can be of a mixed nature and do not need to be of the same nature (i.e. circular or rectangular or another geometry).

It would be appreciated that throughout the description when, for example, the term aperture is used in the context of elongated aperture, the intention is to an elongated aperture.

It would be appreciated that "partially transparent" and "attenuating" are equivalent and the role of such a term is dependent on the amount of

transparency or attenuation. In the above description the role of such terms is provided by the context of the description with specific value examples where needed. The structure examples provided in this disclosure can be implemented with different degrees of transparency to x-ray (or, equivalently, with different degrees of attenuation of x-ray), as preferred for specific implementations. As such they can be highly transitive to x-ray (low attenuation) or poorly transmisive to x-ray (high attenuation). High attenuation also refers to "x-ray blocking" terms since x-ray cannot be 100% blocked and "blocking" is used in the field of the invention to indicate high attenuation.

Figure 13 shows an exemplary user interface which may be implemented as part of a control application running on an electronic device having an interactive display, such as a tablet, a monitor or a smartphone. The application

communicates with the controller 132 and displays the captured and corrected x- ray image.

The user uses four sliders 10201 to determine ROI 10210 size and location according to the area encodes by border lines 10201 A, a rotation button 10202 to determine a rotation direction of the selected ROI (clockwise or anticlockwise) and initiates a rotation of the ROI accordingly until released, a displacement button 10203 for moving the selected ROI without changing its size and orientation and an optional "GO" button 10204 for implementing the actual motion of the collimator plates according to the indicated location, orientation and aperture size.

In the absence of a "GO" button, the plates' motion could starts each time the buttons are released or, in another example, after a predetermined time period with no changes in the interface setup.

Figure 13A is another example of a user interface. In order to select the wanted ROI the user marks any enclosing shape such as shape 10205 on the screen and the collimator plates are arranged in a position where they form an aperture that best encloses the shape. "GO" button 10204 is optional.

In the absence of a "GO" button, the plates' motion could starts each time the user stops drawing, or in another example, after the user removes his finger or drawing pen from a touch screen, or, in another example, after a predetermined time period with no changes in the interface setup.

Figure 13B is another example that is implemented on the same user interface as in Fig. 13A. In order to select the wanted ROI the user marks any shape such as line 10206 on the screen and the collimator plates are arranged in a position where they form an aperture that best encloses the shape.

"GO" button 10204 is optional.

In the absence of a "GO" button, the plates' motion could starts each time the user stops drawing, or in another example, after the user removes his finger or drawing pen from a touch screen, or, in another example, after a predetermined time period with no changes in the interface setup.

Figure 13C is another example that is implemented on the same user interface as in Fig. 13A. In order to select the wanted ROI the user marks more than one shape such as lines 10207A and 10207B on the screen and the collimator plates are arranged in a position where they form an aperture that best encloses the shapes.

"GO" button 10204 is optional. In the absence of a "GO" button, the plates' motion could start each time the user stops drawing a shape segment. Alternatively, the plates' motion could start after a predetermined time period with no changes in the interface setup.

If time < time period - shape is not completed (wait for the user to add new segment to the existing segments).

If time > time period - the drawing is finished and motion of ROI is engaged.

Figure 13D is another example that is implemented on the same user interface as in Fig. 13A. In order to select the wanted ROI the user marks more than one shape such as lines 10207A and 10207B on the screen and the collimator plates are arranged and rotated in a position where they form the smallest aperture that encloses the shapes. In this example the aperture shape is fixed.

Figure 13E is another example that is implemented on the same user interface as in Fig. 13A. In order to select the wanted ROI the user marks more than one shape such as lines 10207A and 10207B on the screen and the collimator plates are arranged and rotated in a position where they form the smallest aperture that best encloses the shapes. In this example the aperture shape may be changed. Figure 13F is another example that is implemented on the same user interface as in Fig. 13A. In order to select the wanted ROI the user marks any shape such as line 10206 on the screen and the collimator plates are arranged in a position where they form an aperture that encloses the shape.

When an additional point 10220 is added outside the ROI, the nearest edge to that point could move in parallel to its direction to that point so that calculated ROI 10212 changes to ROI 10222. In this example the aperture shape is fixed.

Figure 13G is another example, if the of the point 10220A to two nearest edges of the ROI is below some determined value, the corner where these two lines meet could move to the marked point so that calculated ROI 10212 changes to ROI 10222A . In this example the aperture shape may be changed.

ROI 10212 borders could be automatically calculated and set in a variety of methods including: Closing on the enclosed area 10214 so that two of the ROI edges are horizontal and located at maximum Y and minimum Y of area 10214 (in reference to coordinate system 10216 in Figure 13A-13C) at the top and at the bottom of area 10214 and two of the ROI edges are vertical and located at maximum X and minimum X of the border of area 10214 at the left and at right of area 10214.

Same method as (1 ) but including the marking lines that are outside of enclosed area 10214.

The method of either (1 ) or (2) and also rotating the rectangular ROI to an angle that encloses a smaller area. This is demonstrated in Figure 13D where ROI 10214 is rotated and each of the edges of the ROI is set, relative to coordinate system 10216A that is now rotated, for reference, at the same angle ROI 10214 is rotated. Also here the edges parallel to the Y direction enclose on the combined shape of 10207A and 10207B in a position of maximum X and minimum X of the combined shape and the edges parallel to the X axis direction enclose on the combined shape of

10207A and 10207B in a position of maximum Y and minimum Y of the combined shape so that ROI 10214 has smaller area than ROI 10212 of Figure 13C for the same shape. Different criteria may be involved in determining the ROI shape, size and angle. For example:

a. Minimal area could be one criterion for setting the ROI angle and borders as described above.

b. Aspect ratio could be another criterion to set the ROI angle and borders as described above.

c. Minimal ROI dimension could also be used as a criterion for

calculating the desired ROI.

d. An area or dimension factor criterion could also be used to calculate the desired ROI. For example, the calculated area to enclose with the ROI can be a certain percentage of the minimal area. In another example at least one calculated dimensions of the ROI can be changed by a certain percentage. Such changes could also be done using an additive value (positive or negative) instead or with a percentage value. e. A criterion using a percentage of the entire field of view could be used to calculate the desired ROI. For example, such a criterion could require that the ROI area would be 15% of the area of the field of view. In another example the area of the ROI could include a certain amount of pixels of the image.

f. A constraint input by the user could be used also. For example, after setting ROI according to any of the above methods, the user could mark a point outside the ROI (10220 in Figure 13F) and the nearest edge to that point could move in parallel to its direction to that point so that calculated ROI 10212 changes to ROI 10222 (Figure 13F). In another example, if the difference of the point distances to two nearest edges of the ROI is below some

determined value (10220A in Figure 13G), the corner where these two lines meet could move to the marked point so that calculated ROI 10212 changes to ROI 10222A (Figure 13G).

g. The constraints of section (f) above could also be introduced by any of touching at least one of the line images of the ROI and dragging it perpendicularly to its direction and touching at least one of the corner images of the ROI and dragging it in any direction. Such touching and dragging could be done using any input device such as a finger on a touch screen or a mouse of a computer.

h. A combination of any of the above criteria could be used to

calculate the desired ROI. For example, An ROI with a minimal area could be calculated, then the aspect ratio criterion could be employed to increase the smaller size of the ROI until the aspect ratio limitation is satisfied. Then, if the resulting area is still below any area criterion, the ROI could be increased (maintaining the aspect ratio, angle and center) until the area criterion is satisfied. Following that the user can mark a point near an edge, inside the ROI, and the edge moves to that point (overriding the aspect ratio and area criteria. 4. The method of either (1 ), (2) or (3) and also changing from rectangle to any 4-edges shape enclosing the minimal area, as per the example of ROI 10218 of Figure 13E.

5. Closing on the drawn area 10206 so that two of the ROI edges are

horizontal and tangent to the border of 10206 area at the top and at the bottom of area 10206 and two of the ROI edges are vertical and tangent to the border of 10206 area at the left and at right of area 10206.

6. Closing on the drawn area comprising more than one drawing 10207A and 10207B so that two of the ROI edges are horizontal and tangent to the border of 10207A and 10207B area at the top and at the bottom of drawings 10207A and 10207B and two of the ROI edges are vertical and tangent to the border of 10207A and 10207B area at the left and at right of drawings 10207A and 10207B.

7. The method of either (5) or (6) and also rotating the rectangular ROI to an angle that encloses the minimal area.

8. The method of either (5), (6) or (7) and also changing from rectangle to any 4-edge shape so as to enclose the minimal area.

In the example of Figures 13A-13D and 13F an enclosing rectangle is shown, which corresponds to a rectangular aperture such as shown in conjunction with the collimator of Figs. 4 - 7, as will be explained below. In the example of Figures 13E and 13G an enclosing quadrilateral is shown, which corresponds to a quadrilateral aperture such as shown in conjunction with an embodiment of the collimator of Fig. 8-10

The user interface can be operated using touch screen or any other input device such as a computer mouse.

Both user interface options (Figures 13 and 13A) may be active at the same time and the user may select the most appropriate one. According to another embodiment of the present invention, any collimator described herein and any other existing or future collimator may be added to an existing multiple frame imaging system as a retrofit, mechanically connected with the C-Arm and mounted between the existing collimator and the patient. Fig. 14 depicts schematically such a system 5500 comprising an X-ray source 5510, an original collimator 5515, an additional collimator 5520 according to the present invention, a patient 5530, a C-Arm 5535, a detector 5540, an X-Ray controller 5550, an X-Ray operating pedal 5560, an exemplary user interface device joy stick 5570 and a display 5580.

The new system controller 5565 is connected with the detector 5540 to receiver therefrom detected images, image process them as described above in conjunction with the various embodiments, displays the corrected image on the display 5580 and controls the collimator 5520 according to inputs from the joy stick (or tablet or any other user interface device capable of indicating a required ROI relative to a displayed image).

Display 5580 may display the image obtained through both collimators without image correction, the image obtained through both collimators with image correction and the image obtained through the original collimator only.

According to embodiments of the invention, the user interface device may provide selection between the two collimators to determine which collimator is currently addressed. Furthermore, when the original collimator is selected for

operation/activation the newly inserted collimator would translate in parallel with the X-Ray detector plane and move out of the X Ray beam pathway so that not to effect the beam.

The additional collimator 5520 according to the present invention may be connected to the original collimator 5515, or to the radiation tube or to the c-arm by mechanical or other connection means as will be explained bellow in figures 16-19A.

Figure 15 is another embodiment of the system of figure 14 according to the present invention. The additional collimator 5520 may also be driven by a robotic arm 5610 such as for example

in coordination with the original collimator 5515, such that the new collimator moves and functions while being mechanically supported on its own base without necessarily being mechanically attached to any moving section of the original X- ray system. Such robotic arm will use electronic sensors and controllers to provide accurate tracking motion as needed to perform the collimation function of the new collimator which is attached to the end effector/gripper/hand of the robot.

The "robotic arm" may be controlled by use of:

1 . Multiple sensors such as optical, magnetic or others that ensure tracking and coordination with the original collimator and X Ray system.

2. The robot controller 5620 communicates directly with (or in some cases may be embedded within) the C-ARM motion controller 5630.

As mentioned above the additional collimator 5520 according to the present invention may be connected to the original collimator 5515, or to the radiation tube or to the c-arm by mechanical or other connection means. Figure 16 is an example of such mechanical connection. Collimator 5520 is steadily mounted via adapter 5700 to the c-arm 5710 by screws, glue, welding, etc. 5720 that ensure coupling of the adapter and the collimator.

Figure 16A is a top view of the system of figure 16.

Figure 17 is another example of a mechanical connection. Collimator 5520 is steadily mounted via adapter 5810 to the original collimator cover or to the radiation tube cover 5820 by screws, glue, welding, etc. 5830 that ensure coupling of the collimator.

Figures 17A and 17B are side views of the system of figure 17.

Figure 18 is another example of a mechanical connection. Collimator 5520 is steadily mounted via adapter 5910 to the original collimator cover or to the radiation tube cover 5920 by screws, glue, welding, etc. 5930 that ensure coupling of the collimator. The adapter additionally comprises a rotation unit comprising a motor 5940 and a slew bearing 5950. After the collimator 5520 is mounted, it can be rotated using this rotation unit. Sensors 5960 may be placed in each corner of the collimator 5520 (two not shown) in order to prevent collision, for example, with the c-arm. Figure 18A is an example of the system of figure 18 when collimator 5520 is rotated.

Figure 19 is another example of a mechanical connection. Collimator 5520 is steadily mounted via adapter 6010 to the c-arm cabinet 6020.The adapter may be connected anywhere on the c-arm cabinet or rest on wheels on the floor, typically next to cabinet 6020 or the cabinet wheels (not shown).

If it is coupled to the cabinet, it travels with it. The motions of adaptor 6010 components are the same as the c-arm analog components in directions of dual head arrows 6030-6060 (shown in figure 19A).

Figure 19A is a side view of the system of figure 19 with direction dual head arrows 6030-6050.

For example, component 6031 adaptor 6010 is coupled to c-arm component 6032 and whenever c-arm part 6032 moves, adaptor component 6031 follows it and maintains its' position relative to c-arm component 6032. In the same way, each component of the c-arm "arm" that holds collimator 5920 has the analog component in adaptor 6010 that is coupled to it, and moves with it maintaining the relative position.

It would be appreciated by those skilled in the art that the above described methods and technologies are not limited to the configurations and methods mentioned herein above as examples. These are provided as examples and other configurations and methods can be used to optimize final result, depending on the specific design and the set of technologies implemented in the production of the design, including combinations of various embodiments described separately.

The herein above embodiments are described in a way of example only and do not specify a limited scope of the invention.

The scope of the invention is defined solely by the claims provided herein below.