JP2010240305A - Radiation computed tomography scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the flexibility in setting the difference in time between the start of main scan and execution of guidance. <P>SOLUTION: A scanning means including an X-ray tube device 11, an X-ray detector 12, a cradle rotational driving part 13, a high-voltage generating part 14 and a data collecting part 16, etc. can execute the main scan and prep scan for repeatedly measuring a CT value CTmain in a region of interest (ROI) for the main scan within a subject and a CT value CTvoice in an ROI for voice guidance respectively. A main control part 21 starts the prep scan without starting the main scan, but starts the main scan if the CT value CTmain measured in the prep scan exceeds a threshold THmain. The main control part 21 and a speaker 18 output voice guidance on the main scan. The main control part 21 outputs the voice guidance on the main scan by using the speaker 18 if the CT value CTvoice measured in the prep scan exceeds a threshold THvoice. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radiation computed tomography apparatus having a real prep function.

  A computed tomography apparatus (CT apparatus) having a real prep function is known from Japanese Patent Application Laid-Open No. 2004-151867.

  In real prep photography, a prep scan is performed prior to the main scan. The main scan is a scan for collecting CT values necessary for reconstructing a tomographic image of the subject. The prep scan is a scan for measuring a CT value (average value or the like) in an ROI (region of interest) set at an appropriate location. Then, the main scan is started when the CT value measured by the prep scan exceeds the threshold value.

  On the other hand, in the CT apparatus, breath-hold photographing is performed. Therefore, the CT apparatus has a function for guiding a subject to hold a breath by voice or the like.

  Now, in the case of using both real-prep photography and breath-hold photography, it is desirable that the breath-hold is completed when the main scan is started. A certain amount of time is required until the subject's breath holding is completed after the breath holding is guided. For this reason, if the guidance is started after the CT value measured by the prep scan exceeds the threshold value, the start of the main scan is delayed from the optimum timing. Therefore, a threshold value for guidance smaller than the threshold value for main scanning for determining the start timing of main scanning is set, and the CT value measured by the prep scan exceeds the threshold value for guidance. Start breath holding in response to the event, and start the main scan in response to exceeding the threshold value for the actual scan, to provide breath holding guidance during the prep scan. Can be considered.

JP 2003-245275 A

  When the voice guidance “Please hold your breath and stop” is performed, and the time until the subject completes the breath holding after that, about 6 seconds are required.

  On the other hand, the ROI is usually set so that the CT value related to the artery can be measured. For this reason, since the CT value rises rapidly, the time from when the CT value exceeds the threshold value for guidance until it exceeds the threshold value for the main scan is short. The start timing of the main scan may be delayed in order to wait for the voice guidance to be performed and the breath holding to be completed.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a radiation computed tomography apparatus capable of reducing the time from the end of the prep scan to the start of the main scan. There is.

  The radiation computed tomography apparatus according to the first aspect of the present invention includes a main scan for reconstructing a tomographic image relating to an imaging target region in a subject and measuring a large number of CT values, and a first scan in the subject. Scanning means capable of respectively executing a prep scan for repeatedly measuring a first CT value in one region and a second CT value in a second region different from the first region, and the prep scan And the main scan is performed in response to the first CT value measured by the prep scan or the contrast agent concentration determined from the first CT value reaching or exceeding a first threshold value. A scanning control means for controlling the scanning means to start, and a guidance operation for guidance related to the main scanning. And the guidance operation in response to the second CT value measured by the prep scan or the contrast agent concentration determined from the second CT value reaching or exceeding a second threshold value. Guidance control means for controlling the guidance means to perform.

  According to the present invention, by reducing the time from the end of the prep scan to the start of execution of the main scan, it is possible to eliminate the uncertainty of the timing of the main scan and perform the main scan at a more appropriate timing.

The figure which shows the structure of the principal part of CT apparatus which concerns on one Embodiment of this invention. The perspective view of the external appearance of the scan gantry in FIG. The user interface displayed on the display part 24 in FIG. The figure which shows the example of a setting of ROI for voice guidance and ROI for main scans in the positioning image in FIG. The figure which shows the example of a setting of ROI for voice guidance and ROI for main scans in the positioning image in FIG. The flowchart which shows the process sequence in the case of the real prep imaging | photography of the main-control part in FIG. FIG. 5 is a diagram showing an example of changes in CT values CTvoice and CTmain when a main scan ROI and a voice guide ROI are placed as shown in FIG. 4. FIG. 6 is a diagram showing an example of changes in CT values CTvoice and CTmain when the main scan ROI and the voice guide ROI are placed as shown in FIG. 5.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of main parts of a CT apparatus 100 according to the present embodiment. This CT apparatus includes a scan gantry 1 and a computer apparatus 2. The scan gantry 1 is a component for collecting projection data related to a subject. The projection data collected by the scan gantry 1 is used for processing such as image reconstruction in the computer device 2.

  The scan gantry 1 includes a bed 10, an X-ray tube device 11, an X-ray detector 12, a gantry rotation drive unit 13, a high voltage generation unit 14, a bed drive unit 15, a data collection unit 16, a liquid crystal panel 17, and a speaker 18. .

  In the scan gantry 1, the X-ray tube device 11 and the X-ray detector 12 are mounted on an annular rotary mount (not shown) in an opposing relationship. The rotating gantry is driven to rotate by the gantry rotation driving unit 13. At this time, the X-ray tube device 11 and the X-ray detector 12 rotate around the same rotation axis RA. The scan gantry 1 forms a cavity (imaging port) inside the rotation trajectory of the X-ray tube device 11 and the X-ray detector 12.

  The X-ray tube device 11 includes an X-ray tube 11a and an X-ray filter 11b. The X-ray tube 11 a receives power supply from the high voltage generator 14 and emits X-rays toward the X-ray detector 12. The X-ray filter 11b removes low energy components to reduce exposure. The high voltage generator 14 includes a high voltage transformer, a filament current generator, and a rectifier. In addition to this, the high voltage generator 14 includes a tube voltage switch, a filament current switch, and the like in order to adjust the tube voltage and the filament current arbitrarily or stepwise.

  The X-ray detector 12 is configured by arranging a plurality of X-ray detection element arrays in a direction along the rotation axis RA. The X-ray detector 12 detects incident X-rays and outputs an electrical signal corresponding to the intensity.

  The subject is placed on the top 10 a of the bed 10. The bed 10 is driven by the bed driving unit 15 to move the top plate 10a in the longitudinal direction (left and right direction in FIG. 1). Usually, the bed 10 is installed such that the longitudinal direction thereof is parallel to the rotation axis RA. Usually, the subject is placed on the top board 10a so that the body axis is along the rotation axis RA. Thus, the subject is inserted into the cavity of the scan gantry 1 as the top plate 10a moves.

  The data collection unit 16 collects the output of the X-ray detector 12 and supplies it to the computer apparatus 2. Note that an interface using slip ring, optical communication, or the like is interposed between the X-ray detector 12 and the data collection unit 16. As a result, the data collection unit 16 can collect the output of the X-ray detector 12 while continuously rotating the rotary mount.

  The liquid crystal panel 17 displays visual guidance (such as text messages and marks) regarding breath holding and body movement control under the control of the computer device 2.

  The speaker 18 outputs auditory guidance (such as a voice message or a melody) regarding breath holding and body movement suppression based on a voice signal supplied from the computer device 2.

  The computer apparatus 2 includes a main control unit 21, a preprocessing unit 22, an image reconstruction unit 23, a display unit 24, and a console 25. The main control unit 21, pre-processing unit 22, image reconstruction unit 23, display unit 24, console 25 and guidance data storage unit 26 are connected to each other via a data / control bus 27.

  The main control unit 21 controls the operation of the scan gantry 1 so that a main scan is performed so that projection data necessary for diagnosis is obtained. The main control unit 21 controls the operation of the scan gantry 1 so that a prep scan, which will be described later, is performed prior to the start of the main scan during the real prep shooting. The main control unit 21 also controls operations of the liquid crystal panel 17, the speaker 18, and the display unit 24.

  Data supplied from the scan gantry 1 to the computer apparatus 2 is supplied as projection data to the image reconstruction unit 23 via the preprocessing unit 22. The image reconstruction unit 23 reconstructs tomographic image data based on the projection data. The tomographic image data is displayed on the display unit 24 and also supplied to the main control unit 21, and is used for processing for determining the timing of starting the main scan.

  The console 25 is provided for the operator to input various information such as scanning conditions and various instructions. The console 25 includes an operation screen.

  The guidance data storage unit 26 stores data for displaying visual guidance on the liquid crystal panel 17 (for example, image data) and data for outputting auditory guidance from the speaker 18 (for example, audio data).

  FIG. 2 is a perspective view of the appearance of the scan gantry 1.

  As shown in FIG. 2, the liquid crystal panel 17 is provided so as to be visible from a subject placed on the top 10a. The speaker 18 is provided so that sound can be output toward the subject placed on the top 10a.

  Next, the operation of the CT apparatus 100 configured as described above will be described.

  The CT apparatus 100 can operate in various modes provided in known CT apparatuses. Since the operation in this type of mode may be the same as that of a known CT apparatus, the description thereof is omitted here. Here, an operation for real prep photography using breath holding will be described.

  First, the main control unit 21 sets conditions for real prep shooting. The setting of the conditions is performed according to a user instruction on the user interface 30 as shown in FIG. 3 displayed on the display unit 24, for example.

  In the user interface 30 shown in FIG. 3, six input fields 31 to 36, a positioning image 37, and a graph display area 38 are arranged. The main control unit 21 sets the numerical value input by the user in the input field 31 as the voice guidance threshold value THvoice. The voice guide ROI is an area for measuring a CT value to be monitored for detection of voice guide start timing. The main control unit 21 sets a numerical value input by the user in the input field 32 as a delay time described later. The main control unit 21 sets a numerical value input by the user in the input field 33 as a waiting time to be described later. The main control unit 21 sets a numerical value input by the user in the input field 34 as the main scan threshold THmain. The main control unit 21 sets the character strings input in the input fields 35 and 36 as identifiers for identifying the voice guide ROI and the main scan ROI in the positioning image 37, respectively. The positioning image 37 is an image reconstructed by scanning a subject in advance. The main control unit 21 sets the voice guide ROI and the main scan ROI according to the user designation on the positioning image 37. The main control unit 21 shows the set voice guide ROI and the main scan ROI on the positioning image 37. Note that the user can input an arbitrary numerical value or character string in the input fields 31 to 36 by operating a keyboard included in the console 25, for example. Further, the user can arbitrarily designate the positions of the voice guide ROI and the main scan ROI on the positioning image by operating a mouse included in the console 25, for example.

  FIG. 4 is a view showing an example of the positioning image 37 after the voice guide ROI and the main scan ROI are set. In the example of FIG. 4, the axial image of the heart is set as the positioning image 37, and the voice guide ROI is set to the right ventricle and the main scan ROI is set to the descending aorta. In order to indicate that the ROI set in the right ventricle is the voice guide ROI, the main control unit 21 displays “voice”, which is a character string input in the input field 35, next to the voice guide ROI. To express. Further, the main control unit 21 indicates that the ROI set for the descending aorta is the main scan ROI, and is “main” which is a character string input in the input field 36 next to the main scan ROI. Represents.

  FIG. 5 is a diagram showing another example of the positioning image 37 after the voice guide ROI and the main scan ROI are set. In the example of FIG. 5, the voice guide ROI is set to the left ventricle and the main scan ROI is set to the descending aorta.

  FIG. 6 is a flowchart showing a processing procedure of the main control unit 21 at the time of real prep shooting.

  Before or after the main control unit 21 starts the process shown in FIG. 6, a contrast medium is injected into the subject. The injection of the contrast agent is usually performed from the hand of the subject to the vein. The injection of the contrast agent may be performed manually by a doctor, a technician, a nurse, or the like, or may be performed by an automatic injection device. When using an automatic injection apparatus, the control may be performed by the main control unit 21 or may be performed independently of the operation of the CT apparatus 100.

  In step Sa1, the main control unit 21 operates each unit of the scan gantry 1 so as to perform a real prep scan. The real prep scan is typically performed under a scan condition of at least a lower dose and a lower resolution (may be bundled with adjacent channels) than the main scan. In step Sa2, the main control unit 21 operates the image reconstruction unit 23 to reconstruct tomographic image data representing the spatial distribution of CT values based on the projection data obtained by the real prep scan. In step Sa3, the main control unit 21 calculates the CT value CTvoice for the voice guide ROI based on the tomographic image data. Furthermore, in step Sa4, the main control unit calculates a CT value CTmain for the main scan ROI based on the tomographic image data. In step Sa5, the main control unit 21 controls the display unit 24 to display graphs representing changes in the CT values CTvoice and CTmain in the graph display area 38 of the user interface 30 shown in FIG. The main control unit 21 also displays threshold values THvoice and THmain in the graph display area 38.

  In step Sa6, the main control unit 21 confirms whether or not the CT value CTvoice exceeds the threshold value THvoice. While the CT value CTvoice is equal to or less than the threshold value THvoice, the main control unit 21 repeatedly executes the processing from step Sa1 to step Sa6. Note that the repetition of the processing from step Sa1 to step Sa6 is, for example, at intervals of 0.1 second.

  If the main control unit 21 confirms in step Sa6 that the CT value CTvoice exceeds the threshold value THvoice, the main control unit 21 proceeds to step Sa7. In step Sa7, the main control unit 21 stands by until the delay time elapses after the CT value CTvoice exceeds the threshold value THvoice. If the delay time has elapsed, the main control unit 21 proceeds from step Sa7 to step Sa8. In step Sa8, the main control unit 21 reads the voice data from the guidance data storage unit 26, and drives the speaker 18 so as to output a voice guide corresponding to the voice data. The content of the voice guide to be output here is arbitrary, but is typically “Please inhale and stop”.

  In step Sa9, the main control unit 21 operates each unit of the scan gantry 1 so as to perform a real prep scan. In step Sa10, the main control unit 21 operates the image reconstruction unit 23 to reconstruct tomographic image data representing the spatial distribution of CT values based on the projection data obtained by the real prep scan. In step Sa11, the main control unit 21 calculates the CT value CTmain based on the tomographic image data. In step Sa12, the main control unit 21 controls the display unit 24 to display a graph representing a change in the CT value CTmain in the graph display area 38 of the user interface 30 shown in FIG. The main control unit 21 also displays the threshold value THmain in the graph display area 38.

  In step Sa13, the main control unit 21 confirms whether or not the CT value CTmain exceeds the threshold value THmain. Then, while the CT value CTmain is equal to or less than the threshold value THmain, the main control unit 21 repeatedly executes the processing from step Sa9 to step Sa13. In addition, the repetition of the process of step Sa9 thru | or step Sa13 shall be an interval for 0.1 second, for example.

  If it is confirmed in step Sa13 that the CT value CTmain exceeds the threshold value THmain, the main control unit 21 proceeds to step Sa14. In step Sa14, the main control unit 21 stops the real prep scan. In step Sa15, the main control unit 21 confirms whether or not the waiting time has elapsed since the voice guide was output in step Sa8.

  If it is confirmed in step Sa15 that the waiting time has not yet elapsed, the main control unit 21 proceeds to step Sa16. In step Sa16, the main control unit 21 waits until the waiting time elapses.

  If it is confirmed in step Sa15 that the waiting time has already passed, or if the waiting time has elapsed during the waiting in step Sa16, the main control unit 21 proceeds to step Sa17. In step Sa17, the main control unit 21 performs the main scan. In this scan, the scheduled duration, scheduled rotation speed, contrast agent concentration (CT average value) drops to the planned value, or if it is a helical scan, the end condition is that data collection for the planned helical scan range is completed Continue until it meets.

  Now, after passing through the left ventricle, blood and contrast medium flow to the descending aorta via the ascending aorta. For this reason, the arrival time of the contrast agent is delayed in the descending aorta than in the left ventricle. As a result, when the main scan ROI is placed in the descending aorta and the voice guide ROI is placed in the left ventricle as shown in FIG. 4, the CT values CTvoice and CTmain are CT values as shown in FIG. The change in CT value CTmain is delayed compared to the change in CTvoice. Therefore, when the threshold value is set so that THmain ≧ THvoice, the CT value CTvoice exceeds the threshold value THvoice from the timing t2 when the CT value CTmain exceeds the threshold value THmain as shown in FIG. Timing t2 always comes first. Further, the time interval from timing t1 to timing t2 is adjusted by adjusting the difference between THmain and THvoice. Specifically, the difference between the threshold THmain and the threshold THvoice is that the time interval from timing t1 to timing t2 is that the subject completes breath holding according to the time required to output the voice guide and the voice guide. It is desirable that the time is set to be a time corresponding to the sum of the waiting time required for the above or a time obtained by adding a slight margin time.

  Thus, according to the CT apparatus 100, it is possible to ensure a sufficient time for the subject to hold his / her breath according to the voice guide as the time from the output of the voice guide to the start of the main scan. The main scan can be started in the state.

  For example, a case where this function is applied to a cardiac scan will be described as an example. Blood and contrast agent flow from the right ventricle through the lungs to the left ventricle. Therefore, when the voice guide ROI is placed in the right ventricle as shown in FIG. 5, the timing from the timing t1 to the timing t2 is longer than when the voice guide ROI is placed as shown in FIG. As shown in FIG. 8, the time interval is increased by approximately the amount of pulmonary circulation. Therefore, the time interval from the output of the voice guide to the start of the main scan can also be adjusted depending on the position where the voice guide ROI is placed. If the voice guide ROI is set so that the time interval from the timing t1 to the timing t2 is sufficiently long, the threshold THvoice can be set larger than the threshold THmain. If the threshold THvoice is set to a large value, the timing at which the contrast agent sufficiently reaches the voice guide ROI can be set as the timing t1, so that the risk of erroneous voice guide output timing due to noise or the like can be reduced. .

  However, if the time from when the contrast agent reaches the voice guide ROI until it reaches the main scan ROI is too long, the time from the completion of breath holding of the subject to the start of the main scan becomes long. May be too much. However, since the CT apparatus 100 gives a delay time until the voice guide is output after the CT value CTvoice exceeds the threshold value THvoice, the delay time is set appropriately as shown in FIG. A voice guide can be output at an appropriate timing.

  This embodiment can be variously modified as follows.

  (1) Guidance includes auditory guidance other than voice by ringing a melody, visual guidance by displaying a text message or mark on the liquid crystal panel 17 or lighting of a lamp, or vibrating a handle held by the subject. Any of tactile guidance may be used, or a plurality of types of guidance may be used in combination.

  (2) For identification of the voice guide ROI and the main scan ROI in the user interface, identifiers other than character strings such as marks may be used, or the colors may be different. A plurality of methods may be used in combination.

  (3) Real prep imaging to which the present invention is applied can also be used in the same way when imaging a region other than the heart, such as an abdominal organ such as the liver.

  (4) The guidance may be arbitrary, such as “exhale and stop” or “please breathe small”. Further, the guidance is not limited to breath holding, and guidance on other operations may be performed.

  (5) As in the above-described embodiment, a mode for outputting guidance during execution of real prep scan and a mode for outputting guidance after completion of real prep scan may be selectively enabled according to a user instruction.

  (6) The present invention can be applied to any type of CT apparatus such as a single slice type, a multi-slice type, or a type equipped with a surface detector.

  (7) The main control unit 21 may automatically set at least one of the delay time and the waiting time according to a predetermined condition. For example, the delay time may be set shorter as the heart rate of the subject increases, or the waiting time may be set longer as the subject age increases.

  (8) At least one of the delay time and the waiting time may be a fixed value.

  (9) The voice guide ROI and the main scan ROI may be set on different slices. In this case, the user interface 30 shown in FIG. 3 may be changed to include a plurality of positioning images so that the voice guide ROI and the main scan ROI can be set on different slices. In the real prep scan, each of the two slices in which the voice guide ROI and the main scan ROI are set may be scanned simultaneously or sequentially. In the case where two slices are scanned simultaneously, an X-ray diaphragm that can form two openings independently is provided to prevent X-ray irradiation to an area other than the area corresponding to the two slices. It is desirable not to perform unnecessary exposure.

  (10) The contrast agent concentration may be obtained based on the CT value, and at least one of the guidance output timing and the main scan start timing may be detected by comparing the contrast agent concentration with a threshold value.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Scan gantry, 2 ... Computer apparatus, 10 ... Bed, 11 ... X-ray tube apparatus, 11a ... X-ray tube, 11b ... X-ray filter, 12 ... X-ray detector, 13 ... Mount rotation drive part, 14 ... High Voltage generating unit, 15 ... bed driving unit, 16 ... data collecting unit, 17 ... liquid crystal panel, 18 ... speaker, 21 ... main control unit, 22 ... preprocessing unit, 23 ... image reconstruction unit, 24 ... display unit, 25 ... console, 26 ... guidance data storage unit, 27 ... control bus, 100 ... CT device.

Claims (7)

A main scan for reconstructing a tomographic image relating to a region to be imaged in a subject and measuring a large number of CT values, and a first CT value and a first region in a first region in the subject Scanning means capable of respectively executing a prep scan for repeatedly measuring the second CT values in the second region different from
The prep scan is started, and the first CT value measured by the prep scan or the contrast agent concentration determined from the first CT value reaches or exceeds a first threshold value. Scan control means for controlling the scanning means to start a main scan;
Guidance means for performing a guidance operation for guidance related to the main scan;
The guidance operation is performed in response to the second CT value measured by the prep scan or the contrast agent concentration determined from the second CT value reaching or exceeding a second threshold value. A radiation computed tomography apparatus comprising guidance control means for controlling guidance means.   The radiation computed tomography apparatus according to claim 1, further comprising region setting means for setting the second region in accordance with a user instruction. It further comprises display means for displaying a positioning image,
The area setting means sets the second area on the positioning image,
Furthermore, the said display means represents the said 1st and said 2nd area | region on the said positioning image so that the said user can identify, The radiation computed tomography apparatus of Claim 2 characterized by the above-mentioned.   The display means displays at least one of an identifier represented with each of the first and second regions on the positioning image or a color representing the first and second regions on the positioning image. The radiation computed tomography apparatus according to claim 3, wherein the first and second regions are different from each other. Further comprising setting means for setting the respective identifiers represented together with the first and second regions or the respective colors representing the first and second regions in accordance with a user instruction,
The radiation computed tomography apparatus according to claim 4, wherein the display unit uses the identifier or the color set by the setting unit.   The guidance control means performs the guidance operation from the time when a delay time has elapsed from the time when the contrast value determined from the second CT value or the second CT value reaches or exceeds a second threshold value. The radiation computed tomography apparatus according to claim 1, wherein the guidance means is controlled to start. A delay time setting means for setting the delay time according to a user instruction;
The guidance control unit is configured to delay the delay time set by the delay time setting unit from the time when the second CT value or the contrast agent concentration determined from the second CT value reaches or exceeds a second threshold value. The radiation computed tomography apparatus according to claim 6, wherein the guidance unit is controlled so that the guidance operation is started from the time when elapses.

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