CN102846331A - X-ray computed tomography scanning system and method - Google Patents

Abstract

The invention relates to an X-ray computed tomography scanning system and a method. The X-ray computed tomography scanning system comprises a profile scanning parameter determining unit, a control curve determining unit and a scanner, wherein the profile scanning parameter determining unit is used for determining each optimal radiation starting angle alpha<0>opt and each minimum reconstruction angle gamma min which are required for scanning regions of interest in each two-dimensional profile; the control curve determining unit is used for determining control curves which are used for controlling scanning of three-dimensional regions of interest along the direction that a bedstead goes into or out of a gantry according to the obtained optimal radiation starting angles alpha<0>opt and the obtained minimum reconstruction angles gamma min; and the scanner is used for scanning the three-dimensional regions of interest according to the control curves. By means of the X-ray computed tomography scanning system and the method, image reconstruction of the three-dimensional regions of interest can be achieved by using few total radiation doses, energy consumption is saved, temporal resolution of image reconstruction is improved, and service life of X-ray tubes is prolonged.

Description

A kind of X-ray computerized tomography system and method

Technical field

The present invention relates to the medical imaging field, especially a kind of X-ray computerized tomography system and method.

Background technology

Carrying out X ray computer tomoscan (Computed Tomography, CT) in the process, organ or the tissue that usually object to be checked need to be carried out quality image reconstruction are called region-of-interest (region of interest, ROI), and this ROI is the 3 D stereo zone.Based on prior art, be positioned at which position or its size of object to be checked regardless of the ROI of hope scanning and reconstruction, the fixedly reconstruction angle that all will determine according to fixing collimator (phi-collimator) degree of opening, fixing exit dose and certain scan method is carried out the one by one radioscanning of tomography (slide) to patient.

In traditional complete scanning method, will rebuild angle (irradiation duration) γ to each tomography is 360 ° fully scanning.In the part scanning method, adopt certain fixing angle γ of reconstruction (for example 240 °) to come (the Field of Measurement of the measurement territory in this section,, FOM) scanning, FOM has determined directly radiological dose that object to be checked is applied and the size of x-ray irradiation area.And in improved part scanning method (referring to patent documentation 1), in this section, to rebuild angle

Radioscanning, wherein

By the determined angle value of the size of object to be checked.

This shows, according to existing CT scan technology, even three-dimensional ROI only to be an object to be checked very little organ or tissue, total radiological dose can not reduce.

Patent documentation 1: SSME is in December in 2010 application on the 19th, and application number is 201010286350.0, and denomination of invention is the application for a patent for invention of " a kind of X-ray computerized tomography system and method ".

Summary of the invention

In view of this, the present invention proposes a kind of system and method that carries out the X ray computer tomoscan, in order under the prerequisite of the reconstructed image quality that guarantees three-dimensional ROI, reducing significantly the reconstruction angle of each section, thereby effectively reduce total radiological dose of X ray.

According to an aspect of the present invention, provide a kind of X-ray computerized tomography system.This X-ray computerized tomography system comprises: profile scanning parameter determining unit is used for determining that the region-of-interest to each two-dimensional cross-section scans each required optimum radiation initial angle α ₀Opt and each minimum angle γ min that rebuilds; Control curve determining unit is used for according to resulting each optimum radiation initial angle α ₀Opt and each minimum angle γ min that rebuilds pass in and out the orientation determination of frame for the control curve of controlling three-dimensional region-of-interest scanning along bedstead; And scanning device, be used for according to described control curve three-dimensional region-of-interest being scanned.

Preferably, described profile scanning parameter determining unit comprises: the relation curve computing unit, be used for according to the described region-of-interest at two-dimensional cross-section, and calculate radiation initial angle α ₀And the relation curve between the additional angle δ of radiation; Optimum radiation initial angle determining unit is used for according to resulting described relation curve, determines the optimum radiation initial angle α in this two-dimensional cross-section ₀Opt; The additional angle of minimum radiation determining unit is used for according to resulting described relation curve, determines the additional angle δ min of minimum radiation in this two-dimensional cross-section; And the minimum angle calculation unit of rebuilding, rebuild angle γ min for the minimum of calculating this two-dimensional cross-section according to the additional angle δ min of determined minimum radiation.

Preferably, described relation curve computing unit obtains given radiation initial angle α on the described relation curve as follows one by one ₀Corresponding radiation adds angle δ, thereby draws described relation curve: bulb operation circular path upper angle is given radiation initial angle α from this two-dimensional cross-section ₀The described region-of-interest of starting point on the two-dimensional scan plane draw tangent line outside two, and intersect at two intersection points with described bulb operation circular path; After will beginning when described bulb operation circular path clockwise rotates from described starting point through intersection point as end point; Calculate central angle that described starting point turns over to described end point and 180 ° difference, be described given radiation initial angle α ₀The value of the additional angle δ of corresponding radiation.

Preferably, according to the described region-of-interest in this two-dimensional cross-section and given radiation initial angle α ₀, described relation curve computing unit calculates the additional angle δ of radiation according to following formula, thereby draws described relation curve:

$\mathrm{\&delta;}=2\left[\begin{array}{c}\arcsin \left(\frac{\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\sin \left({\mathrm{ROI}\_\mathrm{angle}-\mathrm{\&alpha;}}_0\right)}{\sqrt{{R_{\mathrm{focus}}}^2+{\mathrm{ROI}\_\mathrm{offset}}^2-2R_{\mathrm{focus}}\&CenterDot;\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\cos (\mathrm{ROI}\_\mathrm{angle}-{\mathrm{\&alpha;}}_0)}}\right)-\\ \arcsin \left(\frac{\mathrm{ROI}\_\mathrm{radius}}{\sqrt{{R_{\mathrm{focus}}}^2+{\mathrm{ROI}\_\mathrm{offset}}^2-2R_{\mathrm{focus}}\&CenterDot;\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\cos (\mathrm{ROI}\_\mathrm{angle}-{\mathrm{\&alpha;}}_0)}}\right)\end{array}\right]$

Wherein, ROI_adius is the radius of region-of-interest described in this two-dimensional cross-section, ROI_offset be region-of-interest described in this two-dimensional cross-section with respect to the side-play amount of scanning center, ROI_angle is the position angle of region-of-interest described in this two-dimensional cross-section, R _FocusIt is the radius of described bulb operation circular path.

Preferably, the described minimum angle calculation unit of rebuilding is rebuild angle γ min according to the described minimum that following formula calculates in this two-dimensional cross-section:

γmin＝180°+δmin

Wherein, δ min is the additional angle of described minimum radiation in this two-dimensional cross-section.

Preferably, described X-ray computerized tomography system also comprises three-dimensional region-of-interest determining unit, is used for determining described three-dimensional region-of-interest from checked object.

Preferably, the geometric parameter of the region-of-interest in each two-dimensional cross-section of topological image calculation that described three-dimensional region-of-interest determining unit goes out according to prescan, thus determine described three-dimensional region-of-interest.

According to another aspect of the present invention, provide a kind of X ray computer tomoscan method, comprising: profile scanning parameter determining step is used for determining that the region-of-interest to each two-dimensional cross-section scans each required optimum radiation initial angle α ₀Opt and each minimum angle γ min that rebuilds; Control curve determining step is used for according to resulting each optimum radiation initial angle α ₀Opt and each minimum angle γ min that rebuilds pass in and out the orientation determination of frame for the control curve of controlling three-dimensional region-of-interest scanning along bedstead; And scanning step, be used for according to described control curve three-dimensional region-of-interest being scanned.

Preferably, described profile scanning parameter determining step comprises: the relation curve calculation procedure, be used for according to the described region-of-interest at two-dimensional cross-section, and calculate radiation initial angle α ₀And the relation curve between the additional angle δ of radiation; Optimum radiation initial angle determining step is used for according to resulting described relation curve, determines the optimum radiation initial angle α in this two-dimensional cross-section ₀Opt; The additional angle of minimum radiation determining step is used for according to resulting described relation curve, determines the additional angle δ min of minimum radiation in this two-dimensional cross-section; And the minimum angle calculation step of rebuilding, rebuild angle γ min for the minimum of calculating this two-dimensional cross-section according to the additional angle δ min of determined minimum radiation.

Preferably, in described relation curve calculation procedure, obtain one by one as follows given radiation initial angle α on the described relation curve ₀Corresponding radiation adds angle δ, thereby draws described relation curve: bulb operation circular path upper angle is given radiation initial angle α from this two-dimensional cross-section ₀The described region-of-interest of starting point on the two-dimensional scan plane draw tangent line outside two, and intersect at two intersection points with described bulb operation circular path; After will beginning when described bulb operation circular path clockwise rotates from described starting point through intersection point as end point; Calculate central angle that described starting point turns over to described end point and 180 ° difference, be described given radiation initial angle α ₀The value of the additional angle δ of corresponding radiation.

Preferably, according to the described region-of-interest in this two-dimensional cross-section and given radiation initial angle α ₀, in described relation curve calculation procedure, calculate the additional angle δ of radiation according to following formula, thereby draw described relation curve:

$\mathrm{\&delta;}=2\left[\begin{array}{c}\arcsin \left(\frac{\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\sin \left({\mathrm{ROI}\_\mathrm{angle}-\mathrm{\&alpha;}}_0\right)}{\sqrt{{R_{\mathrm{focus}}}^2+{\mathrm{ROI}\_\mathrm{offset}}^2-2R_{\mathrm{focus}}\&CenterDot;\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\cos (\mathrm{ROI}\_\mathrm{angle}-{\mathrm{\&alpha;}}_0)}}\right)-\\ \arcsin \left(\frac{\mathrm{ROI}\_\mathrm{radius}}{\sqrt{{R_{\mathrm{focus}}}^2+{\mathrm{ROI}\_\mathrm{offset}}^2-2R_{\mathrm{focus}}\&CenterDot;\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\cos (\mathrm{ROI}\_\mathrm{angle}-{\mathrm{\&alpha;}}_0)}}\right)\end{array}\right]$

Wherein, ROI_adius is the radius of region-of-interest described in this two-dimensional cross-section, ROI_offset be region-of-interest described in this two-dimensional cross-section with respect to the side-play amount of scanning center, ROI_angle is the position angle of region-of-interest described in this two-dimensional cross-section, R _FocusIt is the radius of described bulb operation circular path.

Preferably, described minimum the reconstruction in the angle calculation step, rebuild angle γ min according to the described minimum that following formula calculates in this two-dimensional cross-section:

γmin＝180°+δmin

Wherein, δ min is the additional angle of described minimum radiation in this two-dimensional cross-section.

Preferably, described X ray computer tomoscan method also comprises three-dimensional region-of-interest determining step, is used for determining described three-dimensional region-of-interest from checked object.

Preferably, in described three-dimensional region-of-interest determining step, the geometric parameter of the region-of-interest in each two-dimensional cross-section of topological image calculation that goes out according to prescan, thus determine described three-dimensional region-of-interest.

Preferably, described X ray computer tomoscan method also comprises the prescan step, is used for obtaining the topological diagram picture of checked object.

According to technique scheme, the present invention is according to the three-dimensional ROI of difference zone, can adjust the radiation initial angle of the X ray on each x-y plane of scanning motion and rebuild angle, like this in the whole scanning process of frame (gantry), the X ray bulb just is in opening in the less reconstruction angular range in each x-y plane of scanning motion.Therefore, by technical scheme of the present invention, can utilize reconstruction angle less in each section, it is the image reconstruction that less radiological dose is realized three-dimensional region-of-interest, saved energy consumption, improve the temporal resolution (temporal resolution) of image reconstruction, and prolonged the life-span of X ray bulb.

And according to characteristics of the present invention, when carrying out imaging for the more organ or tissue in shifted scanning center, perhaps need to process the special medical of ad-hoc location high-quality imaging for interventional therapy etc., can obtain more significant effect.

Description of drawings

The below will make clearer above-mentioned and other feature and advantage of the present invention of those of ordinary skill in the art by describing the preferred embodiments of the present invention in detail with reference to accompanying drawing, in the accompanying drawing:

Fig. 1 is the system construction drawing of the X-ray computerized tomography system in the specific embodiment of the invention.

Fig. 2 (a) and Fig. 2 (b) show the topological diagram picture that the CT equipment prescan in the specific embodiment of the invention goes out.

Fig. 3 (a) shows the stereoscopic model of three-dimensional region-of-interest in the specific embodiment of the invention.

Fig. 3 (b)-(e) shows the plane of scanning motion figure of four sections in the stereomodel of three-dimensional region-of-interest in the specific embodiment of the invention.

Fig. 4 is the structure chart of the profile scanning parameter determining unit in the specific embodiment of the invention.

Fig. 5 is the radiation initial angle of the x-y plane of scanning motion in the specific embodiment of the invention and the geometrical relationship schematic diagram at the additional angle of radiation.

Fig. 6 shows in the specific embodiment geometric representation of ROI section and radiation initial angle α in the x-y plane of scanning motion ₀Graph of relation with the additional angle δ of radiation.

Fig. 7 shows in the specific embodiment geometric representation of ROI section and radiation initial angle α in the x-y plane of scanning motion ₀Graph of relation with the additional angle δ of radiation.

Fig. 8 is the flow chart of steps of the method for the definite profile scanning parameter in the specific embodiment of the invention.

Fig. 9 calculates radiation initial angle α in the specific embodiment of the invention ₀And the method flow diagram of the relation curve between the additional angle δ of radiation.

Figure 10 is the curve chart that three geometric parameters of each section of three-dimensional region-of-interest change along the z axle.

Figure 11 is that optimum radiation initial angle and the minimum radiation of each section of three-dimensional region-of-interest adds the curve chart that the angle changes along the z axle.

Figure 12 is that optimum radiation initial angle and the minimum of each section of three-dimensional region-of-interest rebuild the curve chart that angle changes along the z axle.

Figure 13 is the method flow diagram of x-ray tomography in the specific embodiment of the invention.

The specific embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, the present invention is described in more detail by the following examples.

Fig. 1 is the system construction drawing of the X-ray computerized tomography system in the specific embodiment of the invention.

As shown in Figure 1, in the specific embodiment of the present invention, X-ray computerized tomography system comprises: profile scanning parameter determining unit 10 is used for determining that the region-of-interest to each two-dimensional cross-section scans each required optimum radiation initial angle α ₀Opt and each minimum angle γ min that rebuilds; Control curve determining unit 20 is used for according to resulting each optimum radiation initial angle α ₀Opt and each minimum angle γ min that rebuilds pass in and out the orientation determination of frame for the control curve of controlling three-dimensional region-of-interest scanning along bedstead; And scanning device 30, be used for according to described control curve three-dimensional region-of-interest being scanned.

In a preferred embodiment, this X-ray computerized tomography system also comprises three-dimensional region-of-interest determining unit 40, is used for determining described three-dimensional region-of-interest from checked object.

Below, we at first introduce the technology contents of the relevant three-dimensional ROI of determining in the specific embodiment of the invention.

Determine three-dimensional ROI

In the present invention, the vertical lifting direction of definition sick bed is the y direction, and the horizontal direction of sick bed turnover frame is the z direction, z direction and y perpendicular direction, with y direction and z direction all the direction of quadrature then be the x direction.

In the specific embodiment of the invention, suppose only need to carry out high-quality image reconstruction for the corresponding organ of three-dimensional ROI or tissue.This ROI zone can comprise part organ or tissue, whole organ or tissue, the set of the several organ or tissues that perhaps pay close attention in the medical examination.

Before CT equipment begins formal scanning, usually need to be to the some width of cloth positioning images of object prescan to be checked, this positioning image is called as topological diagram picture (topography image).Fig. 2 shows the example of employed topological diagram picture in the specific embodiment of the invention.Usually can be to normotopia topological diagram picture and the side position topological diagram picture as Fig. 2 (b) shown in etc. of object scan to be checked shown in Fig. 2 (a).These topological diagram pictures are in order to determining general position and the size of three-dimensional ROI in the object to be checked, thereby obtain rough sweep limits.

Use for certain concrete medical examination, three-dimensional region-of-interest determining unit 40 can be according to the topological diagram picture, use specific image recognition algorithm to automatically identify the three-dimensional ROI zone of a reference, can do manual adjustment according to the medical application of reality to the three-dimensional ROI zone of reference more afterwards, thereby determine the three-dimensional ROI zone of paying close attention to.

For the ease of analyzing and understanding, we can be interpreted as three-dimensional ROI several sections stacking three-dimensional space mesosome that forms on the z direction, and wherein each section consists of an x-y plane of scanning motion, can be described as again two-dimentional x-y plane ROI or ROI section.Thus, the geometric parameter of the ROI in each two-dimensional cross-section of topological image calculation that three-dimensional region-of-interest determining unit 40 also can go out according to prescan, thus determine three-dimensional ROI.

(use variable z for each position on the z axle _iExpression), the object normotopia topological diagram to be checked shown in Fig. 2 (a) looks like can be used to determine three-dimensional ROI size and the position on the x direction, this size and position variables L _x(z _i) and C _x(z _i) expression, wherein L _x(z _i) and C _x(z _i) represent respectively in the normotopia topological diagram picture at z _iLength and the center of position line section; Simultaneously, the image-side to be checked position topological diagram shown in Fig. 2 (b) looks like can be used to determine three-dimensional ROI size and the position on the y direction, this size and position variables L _y(z _i) and C _y(z _i) expression, wherein L _y(z _i) and C _y(z _i) represent respectively in the topological diagram picture of side position at z _iLength and the center of position line section.

In order to make things convenient for analysis and calculation, three-dimensional region-of-interest determining unit 40 can all be appointed as a circle with the section of three-dimensional ROI zone on each x-y plane.Like this, for each z on the z axle _iThe position, several main geometric parameters of the relevant some x-y of ROI plane section just can according to the variable parameter in the topological diagram picture, calculate by following formula (1)-(4):

$\mathrm{ROI}\_\mathrm{radius}|z_i=\max \{\frac{L_x\left(z_i\right)}{2},\frac{L_y\left(z_i\right)}{2}\}...\left(1\right)$

$\mathrm{ROI}\_\mathrm{offset}|z_i=\sqrt{C_x{\left(z_i\right)}^2+C_y{\left(z_i\right)}^2}...\left(2\right)$

$\cos (\mathrm{ROI}\_\mathrm{angle})=\frac{C_x\left(z_i\right)}{\sqrt{C_x{\left(z_i\right)}^2+C_y{\left(z_i\right)}^2}}...\left(3\right)$

$\sin (\mathrm{ROI}\_\mathrm{angle})=\frac{C_y\left(z_i\right)}{\sqrt{C_x{\left(z_i\right)}^2+C_y{\left(z_i\right)}^2}}...\left(4\right)$

Wherein, ROI_adius is the radius of circle of ROI section; ROI_offset is that the ROI section is with respect to the side-play amount of the scanning center (Iso center) on corresponding x-y plane; ROI_angle is the position angle of ROI, and they are value between 0 °-360 °.Those skilled in the art by the result of formula (3) and formula (4), can determine the value of ROI_angle as can be known.

Like this, according to the geometric parameter (ROI_radius, the value of ROI_offset and ROI_angle) of ROI on each x-y section, three-dimensional region-of-interest determining unit 40 can construct the stereomodel of three-dimensional ROI.

Fig. 3 shows the stereoscopic model of three-dimensional ROI in the specific embodiment of the invention and the plane of scanning motion figure of four sections wherein.Wherein, Fig. 3 (a) is the stereoscopic model of the constructed three-dimensional ROI that goes out, and Fig. 3 (b)-(e) is that value is respectively the plane of scanning motion figure on the x-y section of four coordinates on the z axle.

In Fig. 3 (b)-(e), z axial coordinate value is respectively z=0mm, z=47mm, z=96mm and z=150mm.According to the three-dimensional ROI stereomodel shown in Fig. 3 (a), among Fig. 3 (b)-(e) each illustrates size and the position of corresponding ROI section on the plane of scanning motion, wherein central point represents the Iso center of corresponding section, the bulb operation circular path of dashed circle (1) expression X ray bulb in corresponding section, the measurement territory FOM of the corresponding section of dashed circle (2) expression, solid line circle (3) then represents the corresponding section of ROI in this x-y plane.

In this specific embodiment, we at first illustrate the embodiment of the present invention in an x-y plane of scanning motion, and we expand to this embodiment among the three-dimensional ROI afterwards, thereby consist of the system and method in the specific embodiment of the invention.

The x-y plane of scanning motion

In the x-y plane of scanning motion, be different from existing part scanning method, the radiation initial angle α in this specific embodiment ₀To carry out adaptive selection according to size and the position of ROI section, to obtain the additional angle δ of less radiation and to rebuild angle γ.

Fig. 4 is the structure chart of the profile scanning parameter determining unit in the specific embodiment of the invention.

As shown in Figure 4, the profile scanning parameter determining unit 10 in the specific embodiment of the invention comprises: relation curve computing unit 101 is used for calculating radiation initial angle α according at the ROI of two-dimentional x-y plane of scanning motion section ₀And the relation curve between the additional angle δ of radiation; Optimum radiation initial angle determining unit 102 is used for according to resulting relation curve, determines the optimum radiation initial angle α in this x-y scanning section ₀Opt; The additional angle of minimum radiation determining unit 103 is used for according to resulting relation curve, determines the additional angle δ min of minimum radiation in this x-y plane of scanning motion; And the minimum angle calculation unit 104 of rebuilding, rebuild angle γ min for the minimum of calculating this x-y plane of scanning motion according to the additional angle δ min of determined minimum radiation.

For the ROI section of appointment, this specific embodiment can determine to make the optimum radiation initial angle α of required reconstruction angle γ minimum ₀Opt and the corresponding minimum angle γ min that rebuilds.

Study discovery through the inventor, only carrying out at the section on the x-y plane of scanning motion in the situation of high-quality image reconstruction for ROI, from suitable radiation initial angle α ₀The scanning that begins necessarily to rebuild angle can obtain ROI is carried out the required minimum data amount of data reconstruction, rebuilds angle γ and can calculate according to following formula (5):

γ＝180°+δ ……………………(5)

Wherein δ is called the additional angle of radiation in the present invention, and it is by ROI section and radiation initial angle α ₀The common angle value of determining.

By research as can be known, since the additional angle δ of radiation usually less than 60 ° of fan angles that set in the prior art or

Even may be negative angle, therefore compared with prior art, the present invention can reduce to scan the required reconstruction angle γ of each ROI section significantly, thereby reduces total radiological dose.

Fig. 5 is the geometrical relationship schematic diagram that radiates initial angle and the additional angle of radiation in the specific embodiment of the invention in the x-y plane of scanning motion.

As shown in Figure 5, when the X ray bulb moves from bulb that position 1 on the circular path (shown in outer ring dotted line Fig. 5) begins to launch X ray as the radiation starting point and when clockwise rotating along circular path, when setting so that 4 coordinate axess that point to 3 o'clock direction are as 0 ° of coordinate axes position from the Iso center, then this position 1 corresponding corner in the x-y plane is radiation initial angle α ₀Show simultaneously in this x-y plane of scanning motion 40 that determine by the region-of-interest determining unit, as need to carry out the ROI section of quality image reconstruction position among Fig. 5.

In this specific embodiment, relation curve computing unit 101 calculates radiation initial angle α at first according to the ROI section of determining ₀And the relation curve between the additional angle δ of radiation.

At first, relation curve computing unit 101 can be determined certain given radiation initial angle α by following geometric ways ₀The value of the additional angle δ of corresponding radiation.As shown in Figure 5, tangent line outside two of border circular areas of ROI section are drawn in position 1, and intersect at position 2 and position 3 two points with bulb operation circular path.Find through research, the X ray bulb is moved the position of intersecting point that meets after the circular path dextrorotation goes to along bulb, this point as the radiation end point, is the point of position 2 in Fig. 5, can obtains the ROI section is carried out the required minimum data amount of data reconstruction.This shows, the radiation starting point is given radiation initial angle α to radiating central angle that end point turns over and 180 ° difference ₀The value of the additional angle δ of corresponding radiation.

Because the δ angle is negative value in example shown in Figure 5, so the corner dimension between the extended line of the line at position 2 and Iso center 4 and position 1 and Iso center 4 lines is and radiates the order of magnitude that adds angle δ among Fig. 5.As can be seen from Figure 5, the angle that the X ray bulb rotates through to radiation end point (position 2) from radiation starting point (position 1) is rebuilds angle γ, according to formula (5), the additional angle δ of radiation and reconstruction angle γ have 180 ° differential seat angle, thereby can determine to rebuild angle γ by determining the additional angle δ of radiation.Concern as can be known thus, the reconstruction angle γ in this x-y plane of scanning motion is less for the less then X ray of δ-value bulb, and the radiological dose of then implementing for this ROI section is less.

As mentioned above, relation curve computing unit 101 can be determined given radiation initial angle α by geometric ways ₀The value of the additional angle δ of corresponding radiation.Equally, for certain given radiation initial angle α ₀, those skilled in the art also can according to the mathematic parameter of determined ROI section in formula (1)-(4), calculate given radiation initial angle α by mathematical formulae ₀The value of the additional angle δ of corresponding radiation.

For the ROI section of in the x-y plane, determining, can determine by the value of determined ROI_adius, ROI_offset in formula (1)-(4) and three variablees of ROI_angle the accurate location of this ROI.It will be understood by those skilled in the art that according to above-mentioned three variable determined ROI positions and given radiation initial angle α ₀, just can calculate the value that radiation adds angle δ according to following formula (6):

$\mathrm{\&delta;}=2\left[\begin{array}{c}\arcsin \left(\frac{\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\sin \left({\mathrm{ROI}\_\mathrm{angle}-\mathrm{\&alpha;}}_0\right)}{\sqrt{{R_{\mathrm{focus}}}^2+{\mathrm{ROI}\_\mathrm{offset}}^2-2R_{\mathrm{focus}}\&CenterDot;\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\cos (\mathrm{ROI}\_\mathrm{angle}-{\mathrm{\&alpha;}}_0)}}\right)-\\ \arcsin \left(\frac{\mathrm{ROI}\_\mathrm{radius}}{\sqrt{{R_{\mathrm{focus}}}^2+{\mathrm{ROI}\_\mathrm{offset}}^2-2R_{\mathrm{focus}}\&CenterDot;\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\cos (\mathrm{ROI}\_\mathrm{angle}-{\mathrm{\&alpha;}}_0)}}\right)\end{array}\right]...\left(6\right)$

Wherein, R _FocusThe radius of bulb operation circular path, the i.e. radius of outer ring broken circle among Fig. 5.

As mentioned above, those skilled in the art can determine given radiation initial angle α with the geometrograph among Fig. 5 or according to the mathematic parameter of given ROI section ₀Corresponding radiation adds angle δ.When radiating initial angle at α ₀Value one by one in 0 ° of-360 ° of scope, relation curve computing unit 101 just can obtain under the condition of given ROI section, radiation initial angle α ₀With the relation curve of the additional angle δ of radiation, shown in Fig. 6 (a) and Fig. 7 (a).

Fig. 6 shows respectively the geometric representation of ROI section in two different x-y planes of scanning motion and radiates initial angle α with Fig. 7 ₀Graph of relation with the additional angle δ of radiation.In Fig. 6 (b), Fig. 6 (c), Fig. 7 (b), Fig. 7 (c), show respectively the x-y plane geometry schematic diagram for two different ROI sections, wherein the ROI section among Fig. 6 is larger, and covered the Iso center of the x-y plane of scanning motion, and the ROI section among Fig. 7 is less, and away from the Iso center of the x-y plane of scanning motion.Fig. 6 (a) and Fig. 7 (a) show radiation initial angle α respectively for two ROI sections ₀Relation curve with the additional angle δ of radiation.Those skilled in the art can with the geometrograph among Fig. 5 or according to the mathematic parameter of given ROI section, obtain the relation curve shown in Fig. 6 (a) and Fig. 7 (a) by formula (6).

By formula (5) as can be known, the reconstruction angle γ of the additional less then X ray of the angle δ bulb of radiation is less, then less for the required radiological dose of ROI section, thereby those skilled in the art need to determine the optimum radiation initial angle α that makes the additional angle δ of radiation reach minima δ min in the x-y plane of scanning motion ₀Opt.

According to the relation curve that relation curve computing unit 101 calculates, the radiation initial angle α when optimum radiation initial angle determining unit 102 can be minima with the additional angle δ of radiation on the relation curve ₀The optimum radiation initial angle α that is defined as ₀Opt.Simultaneously, according to the relation curve that relation curve computing unit 101 calculates, the additional angle of minimum radiation determining unit 103 also can be determined the value of the additional angle δ min of minimum radiation.And then the minimum angle calculation unit 104 of rebuilding can according to the additional angle δ min of determined minimum radiation, utilize formula (5) to try to achieve the minimum angle γ min that rebuilds.

Determining optimum radiation initial angle α ₀Opt and minimum the reconstruction after the angle γ min, the CT system can together store them, with as the data for the control curve that obtains will illustrating hereinafter.

Below, we are take Fig. 6 and Fig. 7 as example, illustrate that X-ray computerized tomography system in this specific embodiment is when scanning the ROI section in the x-y plane of scanning motion, with respect to the remarkable technique effect of prior art.

As shown in Figure 6, given ROI section is large and cover the Iso center of the x-y plane of scanning motion here, and its location parameter is respectively ROI_radius=150mm, ROI_offset=50mm, ROI_angle=60 °.At this moment, optimum radiation initial angle α ₀Additional angle δ min=19.35 ° of the corresponding minimum radiation of opt, i.e. the minimum of this moment reconstruction angle γ min is 180 °+19.35 °=199.35 °.Contrast traditional complete scanning method, rebuild angle γ and corresponding radiological dose and reduced approximately 44.6%, and contrast part scanning method is rebuild angle γ and corresponding radiological dose and has been reduced about 17%.

As shown in Figure 7, given ROI section is less and away from the Iso center of the x-y plane of scanning motion here, and its location parameter is respectively ROI_radius=50mm, ROI_offset=200mm, ROI_angle=230 °.At this moment, optimum radiation initial angle α ₀Additional angle δ min=-29.2 ° of the corresponding minimum radiation of opt, namely the minimum of this moment rebuild angle γ min be 180 °+(29.2 °)=154.7 °.Contrast traditional complete scanning method, rebuild angle γ and corresponding radiological dose and reduced approximately 57%, and contrast part scanning method is rebuild angle γ and corresponding radiological dose and has been reduced about 37.2%.

Can be found out by different ROI section situation among Fig. 6 and Fig. 7, when the ROI section does not cover the Iso center of the x-y plane of scanning motion, δ min is negative value, rebuild angle γ this moment can be less than 180 °, so the radiological dose that is used for scanning ROI section in the x-y plane of scanning motion can be reduced significantly.Particularly, less and near the FOM edge of the x-y plane of scanning motion time when the scope of ROI section, radiological dose can obtain reducing by a larger margin.

Below, we illustrate for the given x-y plane of scanning motion, determine and store the optimum radiation initial angle α of the ROI section in this plane ₀Opt and minimum method of rebuilding angle γ min.

Fig. 8 is the flow chart of steps of the method for the definite profile scanning parameter in the specific embodiment of the invention.

As shown in Figure 8, step S51 is used for calculating radiation initial angle α according at the ROI of this x-y plane of scanning motion section ₀And the relation curve between the additional angle δ of radiation.As mentioned above, in step S51, those skilled in the art can be with the geometrograph among Fig. 5 or according to the mathematic parameter of given ROI section, determine given radiation initial angle α by formula (6) ₀Corresponding radiation adds angle δ.When radiating initial angle at α ₀Value one by one in 0 ° of-360 ° of scope just can obtain under the condition of given ROI section, radiation initial angle α ₀With the relation curve of the additional angle δ of radiation, for example shown in Fig. 6 (a) and Fig. 7 (a).In this step S51, comprised many steps of step S511-S514, specifically see the method flow diagram shown in Fig. 9.

Fig. 9 calculates radiation initial angle α in this specific embodiment ₀And the flow chart of the relation curve between the additional angle δ of radiation.

As shown in Figure 9, at first in step S511, α is set ₀=0 ° is that 0 ° position begins to calculate from the radiation initial angle namely.Flow process enters step S512.

In step S512, utilize geometric parameter (ROI_radius, ROI_offset, ROI_angle) and the given α of ROI section ₀Value, calculate the value of the additional angle δ of radiation according to formula (6).Flow process enters step S513.

In step S513, judge radiation initial angle α ₀Whether less than 360 °, namely judge whether all radiation initial angle α on the circumference ₀All calculate.If be judged as α ₀Less than 360 °, then flow process enters step S514, if α ₀Be not less than 360 °, then to all radiation initial angle α on the circumference ₀All calculate, namely determined radiation initial angle α in the ROI section ₀And the relation curve between the additional angle δ of radiation, flow process enters step S52 and step S53 simultaneously.

In step S514, α is set ₀=α ₀Flow process is got back to step S512 behind the+Δ α.That is, will radiate initial angle α ₀Value add the value of again calculating the additional angle δ of corresponding radiation behind the increment Delta α.This increment Delta α can be arranged by the operator voluntarily according to the required precision of operator.

Turn back to method flow diagram shown in Figure 8.In step S52, according to resulting relation curve, determine optimum radiation initial angle α ₀Opt.Flow process enters step S55.

In step S53, according to resulting relation curve, determine the additional angle δ min of minimum radiation.Flow process enters step S54.

In step S54, according to the additional angle δ min of determined minimum radiation and formula (5), calculate min=180 °+δ of the minimum angle γ of reconstruction min.Flow process enters step S5.

In step S55, determining the optimum radiation initial angle α of the x-y plane of scanning motion ₀Opt and minimum the reconstruction after the angle γ min are stored them together.

The scan control curve of the three-dimensional ROI of x-y-z

Just as explained above, as long as determined the geometric parameter (ROI_radius, the value of ROI_offset and ROI_angle) of ROI section in certain x-y plane of scanning motion, just can calculate the optimum radiation initial angle α corresponding to this x-y plane of scanning motion ₀Opt and the minimum angle γ min that rebuilds.Z for the z axle _iPosition, the ROI zone on the x-y plane of scanning motion corresponding to whole three-dimensional ROI at z _iLocational section.Below, we expand to above-mentioned analysis and calculation for the x-y plane of scanning motion in the x-y-z three dimensions, thereby obtain in the specific embodiment of the invention whole three-dimensional ROI are scanned required control curve.

Figure 10 to Figure 12 shows the process that is progressively obtained the control curve that the X ray bulb scans three-dimensional ROI by the three-dimensional ROI that determines.Figure 10 is the curve chart that three geometric parameters of three-dimensional each section of ROI model shown in Fig. 3 change along the z axle.Figure 11 is the optimum radiation initial angle α of each ROI section ₀The curve chart that opt and the additional angle δ min of minimum radiation change along the z axle.Figure 12 is the optimum radiation initial angle α of each ROI section ₀Opt and the minimum angle γ min that rebuilds are along the curve chart of z axle variation.

Analyzed as top, for three-dimensional ROI, three geometric parameters along the ROI section of each x-y plane of scanning motion of z axle just can based on the normotopia topological diagram picture shown in Fig. 2 and side position topological diagram picture, be determined by formula (1)-(4).Along with coordinate z _iVariation, we just can obtain respectively the radius (ROI_radius), ROI section of ROI section with respect to the position angle (ROI_angle) of the side-play amount (ROI_offset) at Iso center, ROI section respectively along the formed curve of z axle, as shown in figure 10.

Illustrate as mentioned, for the x-y plane of scanning motion, we can determine the optimum radiation initial angle α of this plane of scanning motion ₀Opt and the additional angle δ min of minimum radiation.Along with coordinate z _iVariation, we can obtain the optimum radiation initial angle α of the plane of scanning motion ₀Opt and the additional angle δ min of minimum radiation are respectively along the formed curve of z axle, as shown in figure 11.And then according to formula (5), we can obtain the optimum radiation initial angle α of the plane of scanning motion ₀Opt and the minimum angle γ min that rebuilds are respectively along the formed curve of z axle, as shown in figure 12.

For three-dimensional ROI, we can be with the optimum radiation initial angle α that obtains ₀Opt and minimum reconstruction angle γ min as controlling the X ray bulb to the control curve that ROI scans, carry out the scan control of CT system along the formed curve of z axle according to this curve.Like this, realize minimizing of radiological dose at each x-y plane of scanning motion, thereby finally reduced total radiological dose of whole 3-D scanning.

With in this specific embodiment, take three-dimensional ROI model shown in Figure 3 as example, the average reconstruction angle of each plane of scanning motion on the z axle is 180.56 °, be 240 ° part scanning method than rebuilding angle, total radiological dose has reduced 24.8%, if compared with traditional reconstruction angle be 360 ° complete scanning method, total radiological dose has reduced 49.8% especially.

Figure 13 is the entire flow figure of x-ray tomography method in the specific embodiment of the invention.Wherein, 0 and Zmax represented respectively two extreme value places of three-dimensional ROI on the z direction of sick bed turnover frame.

In step S1, at first before beginning to scan, CT equipment carries out the prescan of topological diagram picture, can comprise the normotopia topological diagram picture shown in Fig. 2 and side position topological diagram picture.Flow process enters step S2.

In step S2, determine general position and the size of three-dimensional ROI in the object to be checked, thereby obtain rough sweep limits.Particularly, can look like to use specific image recognition algorithm to automatically identify the three-dimensional ROI zone of a reference to topological diagram, according to the medical application of reality manual adjustment be done in the three-dimensional ROI zone of reference afterwards, thereby determined the three-dimensional ROI zone of paying close attention to.

If for accurate calculating, in step S2, can also utilize formula (1)-(4) to calculate the geometric parameter (ROI_radius of ROI section in each x-y plane of scanning motion, the value of ROI_offset and ROI_angle), thereby construct the stereoscopic model of three-dimensional ROI, as shown in Figure 3.Certainly, for the geometric parameter on each ROI section, also can in the step S4 of follow-up introduction, calculate.Flow process enters step S3.

The flow process from step S3 to step S8, we will calculate the optimum radiation initial angle α in each x-y plane of scanning motion ₀Opt and minimum are rebuild angle γ min, and obtain for control X ray bulb three-dimensional ROI being carried out the control curve of radioscanning.

In step S3, z shaft position coordinate z=0 is set, namely begin to calculate from the minimum extreme value place of three-dimensional ROI on the z direction of sick bed turnover frame.Flow process enters step S4.

In step S4, according to given z shaft position, utilize formula (1)-(4) to calculate the geometric parameter ROI_radius of the corresponding ROI section in the x-y plane of scanning motion, the value of ROI_offset and ROI_angle.Flow process enters step S5.

Comprise many steps of step S51-S55 among the step S5, be used for for the given x-y plane of scanning motion, determined and stored the optimum radiation initial angle α of the ROI section in this plane ₀Opt and the minimum angle γ min that rebuilds, as shown in Figure 8.

Step S51 is used for according to the ROI section, calculates the radiation initial angle α in this x-y plane of scanning motion ₀And the relation curve between the additional angle δ of radiation, it has comprised many steps of step S511-S514, as shown in Figure 9.

At first in the step S511 of step S51, α is set ₀=0 ° is that 0 ° position begins to calculate from the radiation initial angle namely.Flow process enters step S512.

In step S512, utilize geometric parameter (ROI_radius, ROI_offset, ROI_angle) and the given α of the ROI section that in step S2 or step S4, calculates ₀Value, calculate the value of the additional angle δ of radiation according to formula (6).Flow process enters step S513.

In step S513, judge radiation initial angle α ₀Whether less than 360 °, namely judge whether all radiation initial angle α on the circumference ₀All calculate.If be judged as α ₀Less than 360 °, then flow process enters step S514, if α ₀Be not less than 360 °, then to all radiation initial angle α on the circumference ₀All calculate, namely determined radiation initial angle α in the ROI section ₀And the relation curve between the additional angle δ of radiation, flow process enters step S52 and step S53.

In step S514, α is set ₀=α ₀Flow process is got back to step S512 behind the+Δ α.That is, will radiate initial angle α ₀Value add the value of again calculating the additional angle δ of corresponding radiation behind the increment Delta α.This increment Delta α can be arranged by the operator voluntarily according to the required precision of operator.

In step S52, according to resulting relation curve, determine the optimum radiation initial angle α in this x-y plane of scanning motion ₀Opt.Flow process enters step S55.

In step S53, according to resulting relation curve, from the additional angle δ of resulting all radiation, determine the additional angle δ min of minimum radiation in this x-y plane of scanning motion.Flow process enters step S54.

In step S54, according to the additional angle δ min of determined minimum radiation and formula (5) in step S53, the minimum of calculating in this x-y plane of scanning motion is rebuild min=180 °+δ of angle γ min.Flow process enters step S55.

In step S55, the optimum radiation initial angle α that will in step S52, determine ₀Opt and the optimum radiation initial angle α that in step S54, determines ₀Opt stores together.

So far, we determine and have stored the optimum radiation initial angle α of the ROI section in this plane for the given x-y plane of scanning motion ₀Opt and the minimum angle γ min that rebuilds.Flow process enters step S6.

In step S6, whether judge the z axial coordinate less than Zmax, namely judge whether all sections of whole three-dimensional ROI are all calculated.If be judged as z less than Zmax, then flow process enters step S7, if z is not less than Zmax, illustrates that then all sections to whole three-dimensional ROI all calculate, and flow process enters step S8.

In step S7, flow process is set after the z=z+ Δ z gets back to step S4.That is, the value of z axial coordinate is added the geometric parameter ROI_radius that again calculates the corresponding ROI section in the x-y plane of scanning motion behind the increment Delta z, the value of ROI_offset and ROI_angle.This increment Delta z can be arranged by the operator voluntarily according to the required precision of operator.

In step S8, according to calculate one by one and store along the z axle, for the result of three-dimensional ROI cross sections to (minimum angle γ min and the optimum radiation initial angle α of rebuilding ₀Opt), control curve determining unit 20 is determined the control curve that carries out three-dimensional ROI scanning for control X ray bulb, as shown in figure 12.Flow process enters step S9.

In step S9, the scanning device 30 in the CT system carries out radioscanning according to determined control curve among the step S8 to three-dimensional ROI.

Show according to analysis and calculation, the present invention can reduce the X bulb significantly for total radiological dose of ROI.In the situation that ROI is less and near the FOM edge, be 240 ° part scanning method than rebuilding angle, total radiological dose can reduce 40% at most, and is 360 ° complete scanning method compared with traditional reconstruction angle, and always radiological dose can reduce 60% at most.

With respect to complete scanning method of the prior art or part scanning method, the present invention has significantly reduced the reconstruction angle of each plane of scanning motion in the situation that guarantee original ROI area image quality, thereby has reduced total radiological dose.Because the minimizing of X ray exit dose, the energy that consumes is corresponding minimizing also, has improved temporal resolution, and has prolonged the life-span of X ray bulb.

And according to characteristics of the present invention, when carrying out imaging for the more organ in shifted scanning center, perhaps need to process the special medical of ad-hoc location high-quality imaging for interventional therapy etc., then can obtain more significant effect.

The above only is preferred embodiment of the present invention, and is in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (12)

1. X-ray computerized tomography system comprises:

Profile scanning parameter determining unit (10) is used for determining that the region-of-interest to each two-dimensional cross-section scans each required optimum radiation initial angle α ₀Opt and each minimum angle γ min that rebuilds;

Control curve determining unit (20) is used for according to resulting each optimum radiation initial angle α ₀Opt and each minimum angle γ min that rebuilds pass in and out the orientation determination of frame for the control curve of controlling three-dimensional region-of-interest scanning along bedstead; And

Scanning device (30) is used for according to described control curve three-dimensional region-of-interest being scanned.

2. X-ray computerized tomography system according to claim 1 is characterized in that, described profile scanning parameter determining unit (10) comprising:

Relation curve computing unit (101) is used for according to the described region-of-interest at two-dimensional cross-section, calculates radiation initial angle α ₀And the relation curve between the additional angle δ of radiation;

Optimum radiation initial angle determining unit (102) is used for according to resulting described relation curve, determines the optimum radiation initial angle α in this two-dimensional cross-section ₀Opt;

The additional angle determining unit (103) of minimum radiation is used for according to resulting described relation curve, determines the additional angle δ min of minimum radiation in this two-dimensional cross-section; And

The minimum angle calculation unit (104) of rebuilding is rebuild angle γ min for the minimum of calculating this two-dimensional cross-section according to the additional angle δ min of determined minimum radiation.

3. X-ray computerized tomography system according to claim 2 is characterized in that, described relation curve computing unit (101) obtains given radiation initial angle α on the described relation curve as follows one by one ₀Corresponding radiation adds angle δ, thereby draws described relation curve:

Bulb operation circular path upper angle is given radiation initial angle α from this two-dimensional cross-section ₀The described region-of-interest of starting point on the two-dimensional scan plane draw tangent line outside two, and intersect at two intersection points with described bulb operation circular path;

After will beginning when described bulb operation circular path clockwise rotates from described starting point through intersection point as end point;

Calculate central angle that described starting point turns over to described end point and 180 ° difference, be described given radiation initial angle α ₀The value of the additional angle δ of corresponding radiation.

4. X-ray computerized tomography system according to claim 2 is characterized in that, according to the described region-of-interest in this two-dimensional cross-section and given radiation initial angle α ₀, described relation curve computing unit (101) calculates the additional angle δ of radiation according to following formula, thereby draws described relation curve:

$\mathrm{\&delta;}=2\left[\begin{array}{c}\arcsin \left(\frac{\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\sin \left({\mathrm{ROI}\_\mathrm{angle}-\mathrm{\&alpha;}}_0\right)}{\sqrt{{R_{\mathrm{focus}}}^2+{\mathrm{ROI}\_\mathrm{offset}}^2-2R_{\mathrm{focus}}\&CenterDot;\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\cos (\mathrm{ROI}\_\mathrm{angle}-{\mathrm{\&alpha;}}_0)}}\right)-\\ \arcsin \left(\frac{\mathrm{ROI}\_\mathrm{radius}}{\sqrt{{R_{\mathrm{focus}}}^2+{\mathrm{ROI}\_\mathrm{offset}}^2-2R_{\mathrm{focus}}\&CenterDot;\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\cos (\mathrm{ROI}\_\mathrm{angle}-{\mathrm{\&alpha;}}_0)}}\right)\end{array}\right]$

Wherein, ROI_adius is the radius of region-of-interest described in this two-dimensional cross-section, ROI_offset be region-of-interest described in this two-dimensional cross-section with respect to the side-play amount of scanning center, ROI_angle is the position angle of region-of-interest described in this two-dimensional cross-section, R _FocusIt is the radius of described bulb operation circular path.

5. X-ray computerized tomography system according to claim 2 is characterized in that, the described minimum angle calculation unit (104) of rebuilding is rebuild angle γ min according to the described minimum that following formula calculates in this two-dimensional cross-section:

γmin＝180°+δmin

Wherein, δ min is the additional angle of described minimum radiation in this two-dimensional cross-section.

6. the described X-ray computerized tomography system of any one is characterized in that according to claim 1-5,

Also comprise three-dimensional region-of-interest determining unit (40), be used for the geometric parameter of the region-of-interest of topological each two-dimensional cross-section of image calculation of going out according to prescan, thereby determine described three-dimensional region-of-interest.

7. X ray computer tomoscan method comprises:

Profile scanning parameter determining step is used for determining that the region-of-interest to each two-dimensional cross-section scans each required optimum radiation initial angle α ₀Opt and each minimum angle γ min that rebuilds;

Control curve determining step is used for according to resulting each optimum radiation initial angle α ₀Opt and each minimum angle γ min that rebuilds pass in and out the orientation determination of frame for the control curve of controlling three-dimensional region-of-interest scanning along bedstead; And

Scanning step is used for according to described control curve three-dimensional region-of-interest being scanned.

8. X ray computer tomoscan method according to claim 7 is characterized in that, described profile scanning parameter determining step comprises:

The relation curve calculation procedure is used for according to the described region-of-interest at two-dimensional cross-section, calculates radiation initial angle α ₀And the relation curve between the additional angle δ of radiation;

Optimum radiation initial angle determining step is used for according to resulting described relation curve, determines the optimum radiation initial angle α in this two-dimensional cross-section ₀Opt;

The additional angle of minimum radiation determining step is used for according to resulting described relation curve, determines the additional angle δ min of minimum radiation in this two-dimensional cross-section; And

The minimum angle calculation step of rebuilding is rebuild angle γ min for the minimum of calculating this two-dimensional cross-section according to the additional angle δ min of determined minimum radiation.

9. X ray computer tomoscan method according to claim 8 is characterized in that, in described relation curve calculation procedure, obtains one by one as follows given radiation initial angle α on the described relation curve ₀Corresponding radiation adds angle δ, thereby draws described relation curve:

Bulb operation circular path upper angle is given radiation initial angle α from this two-dimensional cross-section ₀The described region-of-interest of starting point on the two-dimensional scan plane draw tangent line outside two, and intersect at two intersection points with described bulb operation circular path;

After will beginning when described bulb operation circular path clockwise rotates from described starting point through intersection point as end point;

Calculate central angle that described starting point turns over to described end point and 180 ° difference, be described given radiation initial angle α ₀The value of the additional angle δ of corresponding radiation.

10. X ray computer tomoscan method according to claim 8 is characterized in that, according to the described region-of-interest in this two-dimensional cross-section and given radiation initial angle α ₀, in described relation curve calculation procedure, calculate the additional angle δ of radiation according to following formula, thereby draw described relation curve:

$\mathrm{\&delta;}=2\left[\begin{array}{c}\arcsin \left(\frac{\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\sin \left({\mathrm{ROI}\_\mathrm{angle}-\mathrm{\&alpha;}}_0\right)}{\sqrt{{R_{\mathrm{focus}}}^2+{\mathrm{ROI}\_\mathrm{offset}}^2-2R_{\mathrm{focus}}\&CenterDot;\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\cos (\mathrm{ROI}\_\mathrm{angle}-{\mathrm{\&alpha;}}_0)}}\right)-\\ \arcsin \left(\frac{\mathrm{ROI}\_\mathrm{radius}}{\sqrt{{R_{\mathrm{focus}}}^2+{\mathrm{ROI}\_\mathrm{offset}}^2-2R_{\mathrm{focus}}\&CenterDot;\mathrm{ROI}\_\mathrm{offset}\&CenterDot;\cos (\mathrm{ROI}\_\mathrm{angle}-{\mathrm{\&alpha;}}_0)}}\right)\end{array}\right]$

Wherein, ROI_adius is the radius of region-of-interest described in this two-dimensional cross-section, ROI_offset be region-of-interest described in this two-dimensional cross-section with respect to the side-play amount of scanning center, ROI_angle is the position angle of region-of-interest described in this two-dimensional cross-section, R _FocusIt is the radius of described bulb operation circular path.

11. X ray computer tomoscan method according to claim 8 is characterized in that, described minimum the reconstruction in the angle calculation step, rebuilds angle γ min according to the described minimum that following formula calculates in this two-dimensional cross-section:

γmin＝180°+δmin

Wherein, δ min is the additional angle of described minimum radiation in this two-dimensional cross-section.

12. the described X ray computer tomoscan of any one method is characterized in that according to claim 7-11,

Also comprise three-dimensional region-of-interest determining step, be used for the geometric parameter of the region-of-interest of topological each two-dimensional cross-section of image calculation of going out according to prescan, thereby determine described three-dimensional region-of-interest.

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