JP2015033442A - X-ray ct apparatus and method for upsampling projection data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus and a method for upsampling projection data capable of acquiring upsampled projection data closer to the measured values.SOLUTION: An X-ray CT apparatus 1 acquires the projection data for one rotation (2π rotation) and uses opposite data, in which the X-ray transmission path in the acquired projection data is substantially coincide, to perform upsampling, for example, in a view direction. That is, a virtual channel is inserted between each channel in a real view, the value of the virtual channel is determined by interpolation calculation or the like, and the determined value of the virtual channel is added to the corresponding point at the virtual view position of the opposite data in which the X-ray transmission path is substantially coincide. This process is repeated to generate a virtual view between real views. The data of each channel in the virtual view is determined by interpolation calculation or the like using the value of each corresponding point in the virtual view.

Description

  The present invention relates to an X-ray CT apparatus and an upsampling method of projection data, and more specifically, generation of upsampled projection data in which the number of views or the number of channels of object projection data measured by the X-ray CT apparatus is increased by calculation. About.

  The X-ray CT apparatus circulates around the subject with the X-ray tube apparatus and the X-ray detector facing each other, and irradiates X-rays from a plurality of rotation angle directions (views) for each view. An apparatus that detects X-rays transmitted through a specimen and generates a tomographic image of the subject based on the detected projection data. In such an X-ray CT apparatus, in order to improve the spatial resolution of an image, for example, a method of imaging by increasing the number of views per rotation has been proposed. However, the sampling rate of the data collection device is limited due to hardware limitations.

  On the other hand, Patent Document 1 describes a method for increasing the number of views of acquired projection data by calculation. In the method of Patent Document 1, projection data is interpolated within a selected view range to create an interpolated view. In general, interpolation is to obtain the value of a target point using the values of a plurality of points around the target point.

JP 2001-286462 A

  However, in the X-ray CT apparatus, if the view is different, the data passes through different X-ray transmission paths. Therefore, when an interpolated view value is obtained using adjacent view values, information different from actual subject information is included. Therefore, when an image is reconstructed by using the projection data upsampled by the method of Patent Document 1, the image contains a built-in information, which is a clinical problem.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an X-ray CT apparatus capable of obtaining upsampling projection data closer to an actual measurement value and a projection data upsampling method. Is to provide.

  In order to achieve the above-described object, the first invention is an X-ray source that irradiates X-rays, and an X-ray that is disposed opposite to the X-ray source and detects transmitted X-rays that are transmitted through the subject. An X-ray detector, the X-ray source and the X-ray detector are mounted, a rotating disk rotating around the subject, and transmission X-ray data detected by the X-ray detector are collected, and A projection data generating unit that generates the projection data necessary for image reconstruction by performing the data processing; a projection data acquiring unit that acquires the projection data for at least 2π rotations by rotating the rotating disk; and the projection data An up-sampling unit that up-samples the projection data using facing data whose X-ray transmission paths substantially match, and an image is reconstructed using the projection data up-sampled by the up-sampling unit A reconstruction operation unit, the X-ray CT apparatus characterized by comprising: a display unit for displaying the reconstructed image, the by reconstruction operation unit.

  A second invention is a method for up-sampling projection data acquired by an X-ray CT apparatus, wherein an image arithmetic unit acquires the projection data for 2π rotations, and an actual view of the acquired projection data. A step of inserting a virtual channel inside, a step of assigning a value of the virtual channel as a value of a corresponding point at a virtual view position on opposing data whose X-ray transmission paths substantially match, and a value of the corresponding point And calculating the value of each channel in the virtual view to generate view direction upsampling projection data, and a projection data upsampling method.

  According to the present invention, it is possible to provide an X-ray CT apparatus and a projection data up-sampling method capable of obtaining up-sampled projection data closer to actual measurement values.

Overall configuration diagram of X-ray CT apparatus 1 (A) And (b) The figure explaining the upsampling method using opposite data, (c) The interpolation by 2 points | pieces, (d) The interpolation by 4 points | pieces, (e) The figure which shows the interpolation by TV method A flowchart for explaining the overall flow of processing executed by the X-ray CT apparatus 1 The flowchart which shows the procedure of the upsampling process which the upsampling part 126 of the image arithmetic unit 122 performs. The figure which shows the positional relationship at the time of measurement of adjacent view Va, Vb and virtual view Vc. The figure explaining the difference between (a) upsampling in simple view interpolation and (b) upsampling according to the present invention Diagram explaining upsampling in the channel direction

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, the overall configuration of the X-ray CT apparatus 1 will be described with reference to FIG.
As shown in FIG. 1, the X-ray CT apparatus 1 includes a scan gantry unit 100 and an operation console 120.

  The scan gantry unit 100 is an apparatus that irradiates a subject with X-rays and detects X-rays transmitted through the subject, and includes an X-ray tube device 101, a rotating disk 102, a collimator 103, an X-ray detector 106, A data collection device 107, a gantry control device 108, a bed control device 109, and an X-ray control device 110 are provided.

  The turntable 102 is provided with an opening 104, and the X-ray tube apparatus 101 and the X-ray detector 105 are arranged to face each other through the opening 104. The subject placed on the bed 105 is inserted into the opening 104. The turntable 102 rotates around the subject by a driving force transmitted through a drive transmission system from a turntable drive device controlled by the gantry control device 108.

  The console 120 is a device that controls each part of the scan gantry unit 100 and acquires projection data measured by the scan gantry unit 100 to generate and display an image. The console 120 includes an input device 121, an image calculation device 122, a storage device 123, a system control device 124, and a display device 125.

  The X-ray tube device 101 is an X-ray source, and is controlled by the X-ray control device 110 to irradiate X-rays having a predetermined intensity continuously or intermittently. The X-ray control apparatus 110 applies the X-ray tube voltage and the X-ray tube current applied or supplied to the X-ray tube apparatus 101 according to the X-ray tube voltage and the X-ray tube current determined by the system control apparatus 124 of the console 120. Control.

  A collimator 103 is provided at the X-ray irradiation port of the X-ray tube apparatus 101. The collimator 103 limits the irradiation range of the X-rays emitted from the X-ray tube device 101. For example, it is formed into a cone beam (conical or pyramidal beam). The opening width of the collimator 103 is controlled by the system controller 124.

  The transmitted X-rays that are irradiated from the X-ray tube apparatus 101, pass through the collimator 103, and pass through the subject enter the X-ray detector 106.

  The X-ray detector 106 includes, for example, about 1000 X-ray detection element groups configured by a combination of a scintillator and a photodiode in the channel direction (circumferential direction), for example, about 1-320 in the column direction (body axis direction). It is an arrangement. The X-ray detector 106 is disposed so as to face the X-ray tube apparatus 101 through the subject. The X-ray detector 106 detects the X-ray dose irradiated from the X-ray tube apparatus 101 and transmitted through the subject, and outputs it to the data collection apparatus 107.

  The data collection device 107 collects the X-ray dose detected by each X-ray detection element of the X-ray detector 106 for each view, converts it into digital data, and transmits it as transmitted X-ray data to the image calculation device 122 of the console 120. Are output sequentially.

  The image arithmetic device 122 acquires the transmission X-ray data input from the data collection device 107 and performs preprocessing such as logarithmic conversion and sensitivity correction to create projection data necessary for reconstruction.

  The image calculation device 122 includes an upsampling unit 126 and a reconstruction calculation unit 127.

  The upsampling unit 126 acquires projection data for one rotation (2π rotation) of the turntable, and inserts (upsamples) a virtual view using facing data whose X-ray transmission paths in the acquired projection data substantially match. . The facing data in which the X-ray transmission paths substantially coincide with each other is projection data obtained by Rays that are closest to the transmission path in the measured Rays (X-rays) and are incident from the opposite direction. A virtual view is a view that is inserted between real views that actually have measurements. When upsampling the number of views twice, one virtual view is inserted between real views.

  An example (view direction upsampling) in which the upsampling unit 126 doubles the number of views of projection data will be described with reference to FIG.

  In the projection data for one rotation shown in FIG. 2A, Ray 31 and Ray 32 are opposing data in which the X-ray transmission paths substantially coincide. That is, the opposing data of the points A1 and A2 in the Ray 31 are the points B1 and B2 in the Ray 32, respectively. Point B1 and point B2 are data of adjacent channels on the same real view View (2γm + π) as shown in FIG.

  The relationship between the points A1 and B1 on the projection data can be expressed by the following equation (1) using a function R (γ, θ) using parameters where the channel direction is γ and the view direction is θ. .

  Further, the relationship between the channel and the view at the points A1 and B1 can be expressed by the following equations (2) and (3).

  Thereby, it can be seen that the point A1A2 in the virtual view 41 between the point A1 and the point A2 corresponds to the point B1B2 which is a virtual channel inserted between the point B1 and the point B2 on the real view View (2γm + π). . The value of the corresponding point A1A2 on the facing data (Ray31) for the virtual channel (point B1B2) in Ray32 (actual view View (2γm + π)) can be calculated by the following equations (4) and (5).

  In the same procedure, as shown in FIG. 2B, a point C1C2 adjacent to one pixel in the virtual view 41 is calculated from the facing data of the virtual view 41. Then, the value of the point V41b at the channel position of the virtual view 41 is obtained by interpolation between the point A1A2 and the point C1C2. This operation is repeatedly executed to calculate the value of each channel of the virtual view 41 (points indicated by double circles in FIG. 2B). For the other virtual views 42, 43,..., Each channel data can be similarly calculated using facing data whose X-ray transmission paths substantially match.

When this operation is repeated, virtual views 41, 42, 43,... Are inserted between real views. The projection data upsampled by the upsampling unit 126 is referred to as upsampling projection data. In particular, projection data upsampled in the view direction is referred to as view direction upsampled projection data.
The upsampling unit 126 outputs the upsampled projection data to the reconstruction calculation unit 127.

  The reconstruction calculation unit 127 reconstructs an image such as a tomographic image of the subject using the upsampling projection data. For the image reconstruction processing, any method such as an analytical method such as a filtered back projection method or a successive approximation method may be used.

  The image data reconstructed by the image computation device 122 (reconstruction computation unit 127) is input to the system control device 124, stored in the storage device 123, and displayed on the display device 125.

  The system control device 124 is a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The storage device 123 is a data recording device such as a hard disk, and stores programs, data, and the like for realizing the functions of the X-ray CT apparatus 1 in advance.

  The system control device 124 performs photographing processing according to the processing procedure shown in FIG. In the imaging processing, the system control device 124 sends a control signal corresponding to the imaging conditions set by the operator to the X-ray control device 110, the bed control device 109, and the gantry control device 108 of the scan gantry unit 100, and Control each part. Details of each process will be described later.

  The display device 125 includes a display device such as a liquid crystal panel and a CRT monitor, and a logic circuit for executing display processing in cooperation with the display device, and is connected to the system control device 124. The display device 125 displays the reconstructed image output from the image calculation device 122 and various information handled by the system control device 124.

  The input device 121 includes, for example, a keyboard, a pointing device such as a mouse, a numeric keypad, various switch buttons, and the like, and outputs various instructions and information input by an operator to the system control device 124. The operator operates the X-ray CT apparatus 1 interactively using the display device 125 and the input device 121. The input device 121 may be a touch panel type input device configured integrally with the display screen of the display device 125.

Next, the operation of the X-ray CT apparatus 1 will be described with reference to FIGS.
FIG. 3 is a flowchart for explaining the overall flow of the imaging process executed by the X-ray CT apparatus 1 according to the present invention.

  In the shooting process, first, the system control device 124 receives input of shooting conditions and reconstruction conditions. The imaging conditions include X-ray conditions such as X-ray tube voltage and X-ray tube current, imaging range, gantry rotation speed, bed speed, and the like. The reconstruction condition includes a reconstruction FOV, a reconstruction slice thickness, and the like.

  When shooting conditions and reconstruction conditions are input via the input device 121 or the like (step S101), the system control device 124 collects projection data based on the shooting conditions (step S102). That is, the system control device 124 sends control signals to the X-ray control device 110, the gantry control device 108, and the bed control device 109 based on the imaging conditions. The X-ray control device 110 controls power input to the X-ray tube device 101 based on a control signal input from the system control device 124. The gantry control device 108 controls the drive system of the turntable 102 according to the photographing conditions such as the rotation speed, and rotates the turntable 102. The bed control device 109 aligns the bed to a predetermined shooting start position based on the shooting range.

  X-ray irradiation from the X-ray tube apparatus 101 and measurement of transmitted X-ray data by the X-ray detector 106 are repeated with the rotation of the turntable 102. The data acquisition device 107 acquires transmission X-ray data measured by the X-ray detector 106 at various angles (views) around the subject and sends the acquired data to the image calculation device 122. The image calculation device 122 acquires the transmission X-ray data input from the data collection device 107, and performs preprocessing such as logarithmic conversion and sensitivity correction to create projection data.

  The image arithmetic device 122 (upsampling unit 126) acquires the projection data created in step S102 and performs upsampling processing (step S103; see FIG. 4).

  In the upsampling process, the upsampling unit 126 inserts (upsamples) a virtual view into the actual data so as to obtain a preset number of views, and creates view direction upsampled projection data. The number of views may be a value set in advance according to the specifications of the device, or may be a value set by the operator. Further, it may be a value determined by an image quality index (particularly spatial resolution) set by the operator or other parameters. The upsampling process will be described later (see FIGS. 4 to 6).

  When the up-sampled view direction up-sampled projection data is generated by the process of step S103, the reconstruction calculation unit 127 of the image calculation device 122 next reproduces the image based on the reconstruction condition input in step S101. A configuration process is performed (step S104). Any kind of image reconstruction algorithm may be used in the image reconstruction process. For example, back projection processing such as the Feldkamp method may be performed, or a successive approximation method or the like may be used.

  When the image is reconstructed in step S104, the system control device 124 displays the reconstructed image on the display device 125 (step S105), and ends a series of photographing processing.

Next, the upsampling process in step S103 will be described with reference to FIG.
FIG. 4 is a flowchart for explaining the flow of the upsampling process.

  The upsampling unit 126 first acquires projection data measured by photographing at least one rotation (2π rotation) (step S201). The projection data acquired in step S201 may be collected by the data collection device 107 during shooting, or may be measured in advance and stored in the storage device 123 or the like.

  Next, the upsampling unit 126 upsamples the actual view of the acquired projection data for 2π rotations in the channel direction (step S202). That is, the upsampling unit 126 inserts a virtual channel by interpolation or the like between each channel in the actual view that is the actually measured view.

  Next, the upsampling unit 126 assigns the value of the virtual channel generated in step S202 to the corresponding point at the virtual view position of the opposing data whose X-ray transmission paths substantially match (step S203). In the process of step S203, the upsampling unit 126 obtains a ray (for example, data having the relationship between Ray31 and Ray32 in FIG. 2A) facing the actual view from the projection data for 2π rotation. The opposite data of the real view (2γm + π) shown in FIG. 2A is data that crosses a plurality of real views and real channels as indicated by Ray31. The upsampling unit 126 obtains a point (corresponding point A1A2) corresponding to the virtual channel data (point B1B2) on the opposing data Ray32. The corresponding point is a point located between the real view and the real channel. The upsampling unit 126 assigns the value of the point B1B2 to the virtual channel data (the value of the point A1A2).

  When this operation is repeated, a virtual view is inserted between real views. For example, as shown in FIG. 2B, a virtual view 41 is inserted between the real views 31a and 32a. The virtual view 41 is a set of the corresponding points described above. The upsampling unit 126 obtains each channel data in the virtual view by interpolation calculation or the like using the value of each corresponding point in the virtual view 41 (step S204). For example, the value of the point V41b at the channel position of the virtual view 41 is obtained by interpolation using the values of the corresponding point A1A2 and the corresponding point C1C2 shown in FIG.

  The interpolation calculation in step S202 or step S204 may be simple two-point interpolation that interpolates between adjacent views, for example, as shown in FIG. 2 (c), or is adjacent as shown in FIG. 2 (d). Four-point interpolation may be performed by using view and channel data, or a TV method (Total Variation) or the like may be used as shown in FIG. Further, in 2-point interpolation or 4-point interpolation, linear interpolation or non-linear interpolation may be used.

  The projection data upsampled by the upsampling unit 126 is referred to as upsampling projection data. The upsampling unit 126 outputs the upsampling projection data to the reconstruction calculation unit 127 (step S205). The reconstruction calculation unit 127 reconstructs the subject image using the upsampling projection data.

  As described above, the X-ray CT apparatus 1 according to the present embodiment has the upsampling unit 126 that upsamples projection data. The upsampling unit 126 acquires projection data for one rotation (2π rotation) of the turntable, and inserts a virtual view using facing data whose X-ray transmission paths in the acquired projection data substantially match (up in the view direction). Sampling). Since the channel data of the virtual view is obtained by using the facing data whose X-ray transmission paths substantially match, the channel data of the virtual view can be obtained from the actual projection data having the closest subject information. Thereby, the upsampling projection data becomes closer to the actual measurement value, and a reliable image can be created. In addition, compared with the case where upsampling (simple view interpolation) is performed using the values of adjacent points on the projection data, there is also an effect that the boundary portion is not easily obscured.

The effect of using the upsampling method described in the above embodiment will be described with reference to FIGS.
Points Va and Vb indicated by black circles in FIG. 5 indicate adjacent views. The view position of the view Va is θn, and the view position of the view Vb is θn + 1. A virtual view Vc indicated by a dotted circle is created between these views Va and Vb, and the upsampling by simple view interpolation and the upsampling according to the present invention are compared by taking as an example a case where the number of views is doubled. The view position of the virtual view Vc is θ _{n + 1/2} .

  FIG. 6A shows simple view interpolation. In simple view interpolation, data of the virtual view Vc is interpolated using data of adjacent views Va and Vb. As shown in the right diagram of FIG. 6A, this corresponds to interpolation using data of adjacent points on the projection data. For example, when the number of views is 1500, interpolation data is calculated from data separated by 0.24 (= 360/1500) degrees.

  FIG. 6B shows a case where upsampling is performed by the method of the present invention. In the present invention, the value of the virtual channel (point B1B2) inserted by interpolation or the like between adjacent real channels (point B1, point B2) is set to the virtual view position on the opposing data where the X-ray transmission paths substantially coincide. By assigning to a certain corresponding point, the value of the corresponding point A1A2 close to the virtual view Vc is obtained. Similarly, the value of another corresponding point C1C2 close to the virtual view Vc is obtained from another actual data, and the channel data of the virtual view is obtained using the values of the points A1A2 and C1C2.

Therefore, compared with the simple view interpolation shown in FIG. 6A, the value of each channel of the virtual view using interpolation data at a narrower angle (data indicated by “x” in FIG. 6B). Can be calculated. That is, it is possible to interpolate with data having a narrow beam width (close distance between channels) compared to the case of simple view interpolation, and an image having high spatial resolution can be obtained. For example, when the distance between the X-ray tube device 101 and the X-ray detection element is 1000 mm and the distance between the X-ray detection elements in the channel direction of the X-ray detector 106 is 1 mm, the distance between the channels is 0.057 (= 2 · Each channel data in the virtual view can be obtained from the data separated by tan ⁻¹ ((½) / 1000) degrees.

  The view direction upsampling according to the present invention has an effect of improving the spatial resolution when the inter-view distance Δθ is larger than the inter-channel distance Δch (when Δθ> Δch). Therefore, the upsampling unit 126 determines whether to use simple view interpolation or the method according to the present invention (upsampling method based on opposite data) based on the relationship between the inter-view distance Δθ and the inter-channel distance Δch. It is desirable. It should be noted that since most of the X-ray CT apparatuses that are widely used at present are limited in view rate, the relationship Δθ> Δch is established.

  Or, depending on the relationship between Δθ and Δch, create up-projection data using both the up-sampled projection data by simple view interpolation and the up-sampled projection data using the opposite data of the present invention with appropriate weights. May be.

  Furthermore, in the above-described embodiment, an example in which the number of views is up-sampled twice has been described. However, it is possible to extend the up-sampling to N-times.

  In the above-described embodiment, an example in which upsampling in the view direction is performed using the facing data has been described. However, upsampling in the channel direction can be performed in the same manner.

  When up-sampling in the channel direction, the up-sampling unit 126 inserts virtual view data between real channels using the acquired projection data, and the opposite data in which the values of the virtual view data substantially match the X-ray transmission paths. It is given to the value of the corresponding point at the virtual channel position, which is the upper point. Each view data in the virtual channel is calculated using the value of the corresponding point to generate channel direction upsampled projection data.

  An example of upsampling in the channel direction will be described with reference to FIG. FIG. 7 shows projection data partially cut out as in FIGS. 2C to 2E. Points C1 and C2 are actual projection data, and points V1 and V2 are obtained by interpolation processing or the like. It is the calculated virtual projection data. Using the values of the points C1, C2, V1, and V2, the value of the point C1C2 is obtained.

In order to obtain the value of the point C1C2, for example, an interpolation calculation of Expression (6) may be performed using a weighting coefficient obtained from the inter-view distance Δθ and the inter-channel distance Δch.

Here, W _C1 , W _C2 , W _V1 , and W _V2 are weighting coefficients that satisfy Equation (7).

Note that the weighting factors W _C1 , W _C2 , W _V1 , and W _V2 are obtained by Expressions (8) and (9) according to the relationship between the inter-view distance Δθ and the inter-channel distance Δch.

  Although the upsampling in the channel direction has been described here, the interpolation calculation using the equations (6) to (9) may be performed for the upsampling in the view direction.

  The upsampling method according to the present invention described above can be applied to projection data obtained by any photographing method. For example, the present invention may be applied to FFS (Flying Focus Spot) projection data and quarter offset projection data. FFS (Flying Focus Spot) projection data is projection data obtained by imaging while moving the focal position of the X-ray tube to a plurality of locations. Quarter offset projection data refers to data acquired in the opposite view by disposing the X-ray detector 106 by ¼ element in the rotation direction (channel direction) of the turntable 102 from the X-ray irradiation center. The projection data is a combination of which the channel interval is ½ (the number of channels is doubled).

  The preferred embodiment of the X-ray CT apparatus according to the present invention has been described above, but the present invention is not limited to the above-described embodiment. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

1 .... X-ray CT apparatus 100 ... Scan gantry 101 ... X-ray tube device 102 ... Rotary disc 103 ... ..... collimator 106 ... X-ray detector 110 ... X-ray controller 120 ... console 121 ... input device 122... Image calculation device 123... Storage device 124... System control device 125. Upsampling unit 127... Reconstruction calculation unit

Claims (6)

An X-ray source that emits X-rays;
An X-ray detector that is arranged opposite to the X-ray source and detects transmitted X-rays that are X-rays transmitted through the subject;
A rotary disk that is mounted with the X-ray source and the X-ray detector and rotates around the subject;
A projection data generation unit that collects transmission X-ray data detected by the X-ray detector, performs predetermined data processing, and generates projection data necessary for image reconstruction;
A projection data acquisition unit that rotates the rotating disk to acquire the projection data for at least 2π rotations;
An upsampling unit for upsampling the projection data using facing data in which the X-ray transmission paths in the projection data substantially match;
A reconstruction calculation unit that reconstructs an image using projection data upsampled by the upsampling unit;
A display unit for displaying the image reconstructed by the reconstruction computation unit;
An X-ray CT apparatus comprising: The upsampling unit includes:
Insert a virtual channel in the actual view of the projection data acquired by the projection data acquisition unit,
Giving the value of the virtual channel as the value of the corresponding point at the virtual view position on the opposing data;
The X-ray CT apparatus according to claim 1, wherein the value of each channel in the virtual view is calculated using the value of the corresponding point to generate view direction upsampled projection data. The upsampling unit includes:
Inserting a virtual view into the actual channel of the projection data acquired by the projection data acquisition unit,
Giving the value of the virtual view as the value of the corresponding point at the virtual channel position on the opposing data;
The X-ray CT apparatus according to claim 1, wherein the value of each view in the virtual channel is calculated using the value of the corresponding point to generate channel direction upsampled projection data.   The X-ray CT apparatus according to claim 2, wherein when the distance between views is larger than the distance between channels, the upsampling unit performs upsampling of projection data.   2. The X-ray according to claim 1, wherein the up-sampling unit up-samples the projection data by performing an interpolation operation using a weighting coefficient obtained using a distance between views and a distance between channels. CT device. A method for upsampling projection data acquired by an X-ray CT apparatus,
Image arithmetic unit
Obtaining the projection data for 2π rotations;
Inserting a virtual channel into the actual view of the acquired projection data;
Assigning the value of the virtual channel as the value of the corresponding point at the virtual view position on the opposing data where the X-ray transmission paths substantially match;
Calculating the value of each channel in the virtual view using the value of the corresponding point to generate view direction upsampled projection data;
A projection data upsampling method characterized by comprising:

Images