FI106346B - Digital imaging method and devices for digital imaging - Google Patents

Description

106346

Digital imaging method and equipment for digital imaging

The present invention relates to a digital imaging method 5, wherein the object to be imaged is irradiated and the radiation is detected by semiconductor sensors having an area substantially smaller than the imaging surface.

The invention further relates to devices for digital imaging, where imaging employs a radiation source to irradiate a subject to be imaged and semiconductor sensors to detect radiation, wherein the area covered by the semiconductor sensors is substantially smaller than the imaging surface. In particular, the invention relates to a mammography device employing such techniques.

Different imaging methods are used in a variety of applications. In medical and biotechnology imaging applications, for example, it is typical to pass X-ray, gamma or beta radiation through the object being imaged 20 and further to the imaging surface. In recent years, digital imaging methods have been developed alongside traditional film-based, icy imaging methods, which use semiconductor sensors such as CCD sensors • · *. 25 (Charge-Coupled Device) or CMOS sensors (Complementary • «·) as image acquisition surface. * · * · Metal-Oxide Semiconductor).

V Mammography is a typical medical imaging digital imaging application that requires a wide imaging surface, typically at least 18 x 24 cm, and high resolution. Mom. the graphic also sets strict limits for acceptable exposure to * ·· '·'. Mammography imaging also requires an imaging surface with an active area extending from three · · · 35 sides as close to the outer edge of the imaging area as possible to position the chest and both armpits for 2,106,646 imaging to maximize tissue appearance.

Semiconductor sensors are typically made of silicon. One disadvantage of such sensors is the high cost, because as the size of the sensor increases, its manufacturing cost per area exponentially increases. The manufacture of a single semiconductor sensor is thus very expensive in applications requiring a large imaging surface.

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Attempts have been made to circumvent the above problem by mosaically forming an imaging surface from a plurality of smaller semiconductor sensors, such as those described in, for example, GB Patent 2,305,096. Thus, not all edges of the sensors can be connected to the active area of the other sensor, but there is always a small gap between them. Various solutions based on lenses or fiber optics can be used to compensate for the disadvantages of gaps, but the disadvantages of lenses, r, are poor and the use of fiber optics entails high additional costs. In some applications, attempts have been made to solve the problem by manufacturing a wide area sensor using amorphous silicon based semiconductor technology, but the resolution achievable is not sufficient for high precision medical applications such as mammography.

: Y: 30 • ·: * · *; One known solution for a large imaging surface-. *. is obtained by arranging semiconductor sensors into rows and columns similar to a chessboard pattern such that substantially every other chessboard pattern *: * 35 comprises a semiconductor sensor such that, in one direction, for example, the sensors have a crossing of 3 106346 with respect to the chessboard pattern box and the orthogonal direction, i.e., the columns, in the direction of the sensors: a gap is left. The semiconductor sensor assembly is then arranged to be movable such that the assembly is movable twice in a direction with a gap between the sensors, and the sensor assembly is irradiated in the initial position and after both displacements. In this case, the entire area covered by the sensor assembly, except for the panes on the edges of the imaging surface, can be captured by three illuminations.

The problem with the above arrangement is that the sensor assembly has to be moved and stopped for as many as three different exposures. This makes the mechanical structure of the imaging device 15 difficult to implement, multiple exposures load the radiation source and the imaging time becomes long.

In medical applications, in order to avoid excessive radiation exposure, it is often necessary to arrange collimation 20, i.e. to limit radiation by shading only to the area currently covered by the sensors.

, The implementation of collimation then constitutes its own problem area. For example, when a typical X-ray source «· is not pointy but has a finite dimension, • · Ί 25 for example in the order of 0.3 x 0.3 mm, depending on the structure of the equipment, • · * · forms a few millimeters wide an area of semi-shadow where radiation is not complete. As a result, the collimation must be designed so that there are either 30 crossings or undercuts on the edge regions, ie that the areas to be imaged are either

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: * · *; overlap or that overlap. *. congestion does not occur. However, when using the state of the art chessboard pattern, the overshoot will result in a doubling of the radiation dose in the grid-shaped area, • i * 35 points up to three-fold in the normal target * * »·; ·· image, and 4 106346 shaped area with less or no image information elsewhere.

A further problem is the edge regions of the imaging surface which cannot be completely irradiated. Blank frames remain on the edges of the imaging surface, i.e., only one region of the other screen provides image information, whereby the edges of the imaging surface form a kind of linewall pattern.

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It is an object of the invention to provide an imaging method and apparatus implementing the method so that the above-mentioned problems can be solved or at least their drawbacks reduced. These objects are achieved by a method and apparatus, the characteristic features of which are defined in the appended claims, in particular in the characterizing parts of the independent claims.

In particular, the objects of the invention are achieved by providing semiconductor sensors 20 such that the entire imaging surface can be imaged by two irradiations by moving the semiconductor sensors only once between the irradiations.

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According to a preferred embodiment of the invention, the semiconductor transducers are arranged in a substantially rectangular beam such that the beam comprises a plurality of transverse transducers, one or two of the columns.

; * ί "ϊ Preferably, the control of the semiconductor sensors and other necessary connections are then placed on one side of the sensor. *. * · 30.

In accordance with a further preferred embodiment of the invention, the &quot; said beams being arranged at a distance from each other · '· to form a sensor matrix such that the beams: j. 35 is at most equal to the bars mentioned

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half the width of the active area of the wire sensors.

• · 5 106346

The invention is based on arranging semiconductor sensors in a preferably rectangular shape such that by moving and irradiating the semiconductor sensors from the first position to the second position in both positions, the entire imaging surface is covered, thereby combining the two images to form a coherent image of the entire imaging surface. With the blind matrix, it is possible to limit the radiation in both positions 10 only to the area covered by the semiconductor sensors.

The method and device according to the invention have the advantage of a readily achievable mechanical structure in terms of both the sensor system and collimation. The Sensor and Blind Gun-15 system also provides a clearly targeted and sturdy structure. As the number of exposures decreases, the thermal load of the radiation source is also reduced, so that the cooling of the radiation source does not become a significant problem, and there is no need to wait for the radiation source to slow down the imaging work. Also, the time taken to photograph a single object is reduced when the entire imaging surface can already be covered by two imaging i '·· *'. Further, blank edges of the imaging surface edge i a: * 'are obtained, i.e., the direct edges of the imaging surface are obtained, and the disadvantages of collimation described above are also smaller than in prior art solutions.

The invention will now be described in more detail with reference to its preferred embodiments and with reference to the accompanying drawings, in which: FIG. 1 illustrates an exemplary embodiment of the invention in connection with mammography imaging; Figure 2a shows one preferred sensor beam structure, 6 106346 Figure 2b shows another preferred sensor beam structure, Figure 3 shows one preferred sensor matrix structure, and Figure 4 shows one preferred sensor beam construction.

Figure 1 illustrates an embodiment of the invention in connection with an exemplary mammography imaging, but of course the invention can be used in any other corresponding digital imaging. Referring to Figure 1, semiconductor sensors 1 are arranged in substantially rectangular sensor beams 2, from which sensor beams 2 form a movable sensor matrix 3. Sensor beams 2 are arranged integrally with sensor sensor 3 so that a narrow area of sensor beams 2 remains between sensor beams 2. Collimation is accomplished by substantially rectangular blinds 4 which in turn form a movable blind matrix 5 in which the blinds 4 are fixed relative to one another. The blind matrix 5 is positioned for imaging so that the blinds 4, when viewed from the radiation source 6, overshadow the empty areas between the sensor matrix 3 and f *: "the beam 2, so that these areas are not exposed to radiation. such as in the immediate vicinity of, or at a distance from, the object to be depicted in Figure 1. The subject to be imaged 7, typically in the mammography, is placed between the • · 30 dynamometer 5 and the sensor matrix 3 and irradiated from the radiation source 6. Semi-· · ·. *: The transducer transducers 1 express their received radiation, which is used to generate digital image information by means of a sampling and holding circuit 8 and an analogue: ": ....: 35 digital converter 9. The image information can be · · edited if necessary. adds, for example, the dark stream and the 7106346 living things The image information is then forwarded either to the processing means 10 or to the memory means 11. The sensor matrix 3 is then moved laterally with the object 7 to be imaged 7 so that the sensor beams 2 cover substantially the same positions as the sensor beams 2 prior to transfer. Typically, in mammography, the subject 7, i.e., the breast, is held in place by means of compression means (not shown). Correspondingly, the blind matrix 5 10 is displaced such that the blinds 4 now shade the blank areas between the sensor beams 2 according to the new position of the sensor matrix 3. The object to be imaged 7 is irradiated for a second time with new settings of the sensor matrix 3 and the blind matrix 5, and the image information generated by the first irradiation 15 is combined with the image information generated by the second irradiation in processing means 10. This two irradiations produce an image of the entire image.

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The solution described above provides significant advantages over the prior art. The mechanical structure according to the invention is easier to implement both in terms of collimation of the sensor matrix et. The sensor matrix of rectangular transducer bars r '· / · 25 is clearly perpendicular to: Y: and is robust in structure. Blind Matrix • *: * · *: Also easy to build and alignable with the sensor matrix. Further, when the subject to be imaged is only irradiated twice, the load * * 30 of the radiation source is reduced, which extends its life and speeds up imaging work as the radiation requirement of the radiation source decreases, and also the time required for imaging a single object.

Compared to a uniform imaging surface, the system according to the invention requires only »half of the active surface area of the semiconductor probes. On the other hand, when using CMOS sensors, for example, the invention can be implemented, if desired, without the need for any arrangement based on lenses or fiber optics to compensate for gaps between semiconductor sensors 5.

When transmitting the sensor and blind matrix only once, you only have to ensure the accuracy of one-way transfer. In this way, it is possible to perform the delivery and alignment of the blind matrix mi-10 so that the overshoot in the areas to be irradiated is significantly reduced and thus the disadvantages of collimation compared to known solutions are reduced.

The final generation of the digital image can be accomplished by connecting the imaging equipment to the computer, thereby utilizing the computer memory and processing means. The processing means 10 according to Figure 1 may also be implemented, for example, by a dedicated ACID (Application Specific Integrated Circuit) circuit 20, to which memory means 11, for example FLASH memory, is connected.

; As such, the generation of final image information is a technique known to those skilled in the art, and it is not necessary to explain it in detail for the practice of the invention.

According to a preferred embodiment of the invention, the sensor beams 2 to be inserted into the sensor matrix 3 are formed of semiconductor sensors 1 substantially smaller than the sensor beams 2. Figures 2a and 2b illustrate two preferred methods. 30 arranges the semiconductor sensors 1 as a sensor beam 2. In both figures, the sensor beam 2 comprises semiconductor sensors 1a,:. '* I Ib,. . . A typical semiconductor sensor In comprises an active region A used for detecting received radiation 35 and a switching area K through which the control signals and the discharge of the sensor In are transmitted, i.e. here 9 106346 the collection of image information. The semiconductor sensor In typically has at least one edge reserved for the switching area K, so that the semiconductor sensor In can advantageously be connected to the second semiconductor sensor In from three edges 5 as shown in Figure 2b, if the active areas of the sensors are desired. The transducer beam 2 can thus be formed from either one (1 x N) or two (2 x N) columns of semiconductor sensors In. The distance between the sensor beams 2 in the sensor matrix 3 is determined by the active area A width #A of the semiconductor sensors 1 used, i.e., the maximum distance between the sensor beams 2 in the case of single column sensor beams 2 is A # width #A (Fig. 3) the connection is 2 x A wide, or 2 x #A.

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When the sensor beam 2 is formed from semiconductor sensors In, substantially smaller than the sensor beam 2, there is no need for large and thus expensive semiconductor sensors. A further cost saving is that if a single semiconductor sensor-20 is defective, it can be replaced without having to replace the entire sensor beam 2.

Figure 3 illustrates a method according to the invention for arranging the sensor beams 2 preferably so that the imaging surface is maximized and the edges of the imaging surface are uniform. The sensor beams 2 consist of a single column (1 x N) of semiconductor sensors In, whereby the outermost sensor beams 2 are positioned such that half of the coupling region K of the conductor sensors In is positioned inside the sensor matrix 3. In this case, the imaging surface • · * covers the entire area covered by the sensor matrix 3 and not the so-called.

• · \ '* i castle wall pattern is formed at the edges of the imaging surface. The positioning of the switching regions of the inner sensor beams 2 of the sensor matrix 3 can be selected freely, provided that the empty spaces between the an-35 sensor beams are properly dimensioned. Of course, the transducer beams 2 can also be formed from two columns (2 x N) of semiconductor transducers In, but if the transverse transducer beams 2 are also formed in this way, the active area of the transducer matrix 3 cannot be laterally extended as far as the imaging surface.

Naturally, the invention can also be considered to be applicable by constructing a sensor matrix having different, e.g., different width active areas, both single and double column, opposite side connection areas and / or even different technology based sensor beams. However, and especially if such sensor matrices are used in applications where radiation must be confined to the sensor matrix region, some of the benefits of the invention may be lost.

According to a preferred embodiment of the invention, the movements of the blind matrix and the sensor matrix are not coupled to each other, but each matrix is moved separately. Preferably, this is done by first moving the sensor matrix to its new position and then aligning the blind matrix with the sensor matrix. Of course, j '·. however, the invention may also be carried out in such a way that the movements of the blind matrix and the sensor matrix are synchronized.

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The motion of the sensors and / or blinds can be effected, for example, by solenoids or by separate servomotors.

• · · l.m.m 30 In particular, the use of a solenoid is recommended because it is a cheap, accurate and reliable component. The invention, known as • ·!. * ·, Permits the use of solenoids, whereby it is only necessary to move the sensors and / or blinds between two positions.

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According to a preferred embodiment of the invention, semiconductor sensors are CMOS sensors based on direct radiation detection and have certain advantages over conventional semiconductor sensors. CMOS sensors achieve a better resolution than conventional semiconductor sensors, and the parallel bus type, due to its data transmission, allows for faster transfer of image information. CMOS technology is the most widely used semiconductor technology, which results in high availability of CMOS circuits and lower manufacturing costs as technology advances.

Figure 4 illustrates a preferred way of forming a sensor beam according to the invention from CMOS sensors. CMOS Sensors 15 13, 14,. . . preferably connected to a radiation detector 12 having a rectangular shape substantially comprising the outer dimensions of the beam. The detector 12 is preferably made of doped silicon (Si) or a cadmium zinc telluride compound (CdZnTe). Between the upper and lower surfaces of the detector, a bias voltage Ur is applied to the current generated by the radiation at the nearest pixel. The resulting current is applied to the CMOS sensors 13, 14,. . ., which are connected to the detector 12, preferably microscopically; ten ball guides, or so-called. bump bonding

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·. '·· 25. The connector pins at the end of the CMOS sensors allow the sensors to both supply control signals and read the detected radiation to generate image information. The detection of radiation by CMOS sensors is well known to those skilled in the art.

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Of course, semiconductor sensors based on the use of lenses or fiber optics, known per se, can also be used according to the invention, whereby switching areas are possible> <it; 35 in the three-dimensional structure of the sensor also places it on a surface such that the entire width of the sensor is utilized as a radius-detecting active region. However, at the same time, some of the advantages achieved by the invention are lost.

Although the invention has been described above by way of example in connection with mammography, it can, of course, also be used in connection with any other corresponding imaging application. Any detectable radiation from semiconductor sensors can be used according to the invention.

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A particularly useful invention is in medical technology imaging applications, which typically use X-ray or gamma radiation, and in biotechnology applications, which typically use beta radiation. Further, the invention is applicable to industrial testing and quality control methods utilizing X-rays.

It will be apparent to a person skilled in the art that as the technology evolves, the basic idea of the invention may be implemented in many ways, so that its various embodiments are not limited to the examples described above, but may vary within the scope defined by the appended claims; '1 in you.

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Claims (30)

Digital imaging method, wherein the object to be imaged is irradiated and the radiation is detected with semiconductor encryption, which comprises an active area and in its three-dimensional structure an area or areas for control connections, the area covered by the semiconductor sensors being substantially smaller than the imaging surface of the object to be imaged, characterized in that the object 10 to be imaged is irradiated two times and the semiconductor sensors are moved to a new position between the irradiations, the sensors being arranged to cover the imaging surface in such a manner that the entire imaging surface is imaged. 2. Imaging method according to claim 1, characterized in that the coupling area of the semiconductor is arranged in i: III 'on one of its sides. (c Imaging method according to claim 1 or 2, characterized in that the semiconductor sensors are arranged to form a substantially rectangular beam. Imaging method according to claim 3, characterized by X! thereof, said beam being arranged to form a column (1 x N) semiconductor transducer. • «• Imaging method according to claim 4, characterized in that the semiconductor transducers are arranged in the beam in such a way that their couplings are located substantially on one side of the beam. Imaging method according to any of claims 3-5, characterized in that a sensor matrix is formed by the beams, the beams being arranged at a distance from each other in such a manner that said distance is at most equal to the width of the beam. the semiconductor sensors in the beams formed the active region. Imaging method according to claim 6, characterized in that the outermost beams of the sensor matrix are arranged in such a way that their active surface comprises the outer edges of the imaging surface. 8. Imaging method according to claim 3, characterized in that said beam is arranged to comprise two columns (2 x M) semiconductor sensors. Imaging method according to claim 8, characterized in that the semiconductor transducers are arranged in the beam in such a way that their coupling areas are located substantially on two sides of the beam. Imaging method according to claim 8 or 9, characterized in that a sensor matrix is formed by the beams, the beams being arranged at a distance from each other in such a manner that said distance is at most equal to large as the width of the active area formed by the semiconductor in the beams. <i l ii !! i Imaging method according to any one of claims 1-10, c, characterized in that the radiation is defined essentially to the area covered by the sensors, whereby the aperture advantageously suitable aperture construction is used. · · · · · · · · 12. Imaging method according to claim 11, characterized in that the aperture structure and sensors are moved separately. Imaging method according to any of claims 1-12, characterized in that the movement of the aperture structure 106 and / or the sensors is realized by means of solenoid. The imaging method according to any of claims 1-13, characterized in that CMOS sensors are used as semiconductor sensors. Imaging method according to any of claims 1-14, characterized in that the method is used in connection with mammography imaging. A digital imaging device using a radiation source to irradiate the object to be imaged and a semiconductor sensor to detect the radiation, the semiconductor sensor (1) comprising an active area (A) and in its three-dimensional structure a area or areas' ·· '' for control couplings (K), and wherein the area covered by the semiconductors (1) is substantially smaller than the imaging surface, characterized in that the device includes tools::, 20 for moving the semiconductor sensors (1) to a new position between two irradiations, wherein the semiconductor sensors (1) and the tools for their displacement have been arranged in such a way that the area covered by the semiconductors (1) in its initial position combined with the area covered by the semiconductor sensors (1) the displaced position covers the entire • t V .: imaging surface. · · · · · · · · · Device according to claim 16, characterized in that the coupling area (K) of the semiconductor sensor has been arranged on one side thereof. Apparatus according to claim 16 or 17, characterized in that several semiconductor transducers (In) are arranged to form a substantially rectangular beam (2). 35 21 106346 19. Apparatus according to claim 18, characterized in that said beam (2) comprises a column (1 x N) semiconductor transducer (In). 20. Device according to claim 19, characterized in that the semiconductor transducers (In) are arranged in the beam (2) in such a way that their coupling areas (K) are located substantially on one side of the beam (2). 21. Device according to any one of claims 18-20, characterized in that the beams (2) form a transducer tris (3), the beams (2) being spaced apart (A #) in such a manner that said distance (A #) is at most equal to the width of the active region (A) formed by the semiconductors (In) in said beams (2). Apparatus according to claim 21, characterized in that the active area (A) of the outer beams (2) i, '; the sensor matrix (3) comprises the outer edges of the imaging surface. : '' 20 Device according to claim 18, characterized in that said beam (2) comprises two columns (2 x, N) semiconductor transducers (In). t 24. Device according to claim 23, characterized in that the semiconductor transducers (In) are arranged in the beam in such a way that their coupling areas (K) are located substantially on two sides of the beam. the beams (2). • · • t Device according to claim 23 or 24, characterized in that a sensor matrix (3) is formed by the beams (2), the beams (2) being spaced apart (A #) in such a manner that said distance (A # ) is at most equal to the width of the active region (A) formed by the semiconductor sensors (In) in the beams (2). 22 106346 Device according to any one of claims 16-25, characterized in that it comprises tools for defining the radiation substantially to the area covered by the sensors (1), which tools advantageously comprise suitable aperture construction (4, 5). Device according to claim 26, characterized in that it includes separate tools for moving on one side of the aperture structure (4, 5) and on the other side of the sensors (1). Apparatus according to any of claims 16-27, characterized in that said means for moving the apertures (4, 5) and / or the sensors (1) comprise a solenoid; noid. Device according to any one of claims 16-28, characterized in that the semiconductor sensors (1) are CMOS givers. Mammography equipment, which includes which kind of device according to claims 16-29 for digital imaging of the tissue to be imaged. 25 • · • · · • • • • • • • • • m 9% 9 9 9 9 9 9 9 9 9 9