JPH0441019B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention concentrically integrates a plurality of cylindrical phantoms with different X-ray transmission characteristics and fixes them in a cradle, and during calibration, the plurality of cylindrical phantoms are The scan technique (scan conditions) corresponding to the type of calibration specified in advance is automatically selected from among the calibration types, and the cradle is automatically moved in response to the selection operation to move the phantom. The present invention relates to an X-ray tomography apparatus equipped with an automatic calibration function that performs calibration by installing an X-ray tomography device at a predetermined position.

(Prior Art) Conventionally, an X-ray tomography apparatus shown in FIG. 4 has been known. In FIG. 4, the gantry 1 is
An X-ray tube 4 and a detector 5 are arranged opposite to each other with an opening 3 into which the subject 2 is inserted, and the X-ray tube 4 and the detector 5 are configured to integrally go around the subject 2 and collect scan data (projection data). There is. X-rays from the X-ray tube 4 are turned into a thin fan beam 7 by a collimator 6 and irradiated onto the subject 2 . A head filter and a body filter (both not shown) are provided near the X-ray tube 4, and normally one of them is switched to the X-ray irradiation path (fan beam) depending on an external signal. installed in the passageway). The table device 8 has a cradle 1 on the table body 9.
0 is supported so that it can slide freely in the direction of arrow A (the movement itself is controlled from the outside), and the subject 2 placed on the cradle 10 is installed at a predetermined position. In addition to the X-ray tomography equipment shown in Figure 4,
Normally, there is a high-pressure generating section that drives the X-ray tube 4, a memory section that stores scan data, an operator console that generates various control signals, performs image reconstruction processing using the scan data, and displays it, and an operator console that displays the reconstructed image. It is equipped with a multi-format camera that shoots on film. The operator console has
A control unit and a high-speed arithmetic processing unit consisting of a computer, etc., an image display unit consisting of a CRT, etc., an operation board with lamps that display information at the time of image shooting and keys that give various settings and command signals, and a carrier. A calibration operation section consisting of keys and the like for setting and commanding parameters etc. during calibration is provided.

In the above configuration, system calibration is performed as appropriate prior to tomographic imaging of the subject. System calibration creates a file using scan data collected by performing air scan and phantom scan. On the other hand, in system calibration, scanning parameters are set (specified) on the calibration operation section while talking to the display section (CRT).
Although this method involves some operations, the setting operations need to be performed for each scan and are performed many times. For example, when using an air scan, there are two types of filters and three slice thicknesses.
The setting operation is performed 12 times with two types and rotation directions. In addition, the setting operation for phantom scanning was performed 18 times, with three types each for FOV (Field Of View) and slice thickness, and two types for rotation direction. Therefore, setting operations are performed 30 times during one system calibration. In addition, a centering operation (operation for aligning the center axis of the phantom with the center axis of the aperture 3) accompanying phantom exchange during phantom scanning is performed.

System calibration is executed while performing the above operations, collects predetermined scan data, and creates (updates) a calibration file. This makes it possible to maintain good image quality during actual photographing.

(Problems to be solved by the invention) However, in the case of conventional X-ray tomography devices,
During system calibration, when it is necessary to center each time a phantom is replaced or installed, or when only several types of calibration files are to be updated, the operator selects the scan type that corresponds to that calibration. System calibration is not only troublesome but also requires time.

The present invention has been made in view of the above, and an object of the present invention is to provide an X-ray tomography apparatus that allows calibration work to be performed easily and in a short time.

(Means for Solving the Problems) The X-ray tomography apparatus of the present invention that achieves the above object has a plurality of cylindrical phantoms having different X-ray transmission characteristics, which are concentrically fixed to a cradle, and a carrier. At the time of calibration, a scan technique corresponding to the type of calibration specified in advance is automatically selected from among a plurality of calibrations, and the cradle is automatically moved in response to the selection operation. The Phantom is installed in a predetermined position and calibration is performed.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1A is a block diagram showing an embodiment of the present invention. In FIG. 1A, the phantom 11 is composed of a cylindrical water phantom 12 and polyethylene phantoms 13 and 14, which are arranged concentrically and integrated in three axial directions. Phantom holder 15 equipped with a fine adjustment mechanism (in each of the x, y, and z directions in Fig. 1B)
It is fixed to the cradle 10 via. By operating this fine adjustment mechanism, the center axis of Phantom 11 can be adjusted.
Coincidence between O ₁ and the central axis O ₂ of the opening 3 is realized. During system calibration, the cradle 10 places the phantom 11 at a predetermined position determined in the z direction by a signal from a control section, which will be described later. Diameter of each phantom 12, 13 and 14
K ₁ , K ₂ and K ₃ and the thickness L ₀ are Phantom 11
is determined by the performance of the X-ray tomography device installed, and in this example, K ₁ = 25
cm, K ₂ = 35 cm, K ₃ = 42 cm, and L ₀ = 20 mm. The thickness L ₀ =20 mm is a value determined with the minimum necessary margin for the maximum thickness L _nax mm during scanning.

On the other hand, the operator console (not shown) is equipped with a control section (not shown) equipped with a calibration scan control table shown in FIG. ) and performs a predetermined calibration operation to create a calibration file. The calibration scan control table consists of an air scan control table and a phantom scan control table.
By setting the scan mark (setting it to "0" or "1"), various scan techniques (scan time, FOV, filter,
Scanning is performed selectively from among scan conditions (such as tube current, slice thickness, rotation direction, table position, etc.). The control table for the air scan places the Phantom 11 in a predetermined position.
That is, the water phantom 12 is moved from the X-ray irradiation path z ₀ to −L ₀
Set the FOV to 25cm or 35cm (the head filter or body filter will be automatically installed depending on the setting operation), and set the FOV to The air scan is configured to execute the air scan with the thickness and rotation direction set below (the thickness is selected from 10 mm, 5 mm, and 2 mm, and the rotation direction is selected as clockwise or counterclockwise). At this time, the X-ray tube current was 50 mA and the scan time was 8 mS.

The control table for phantom scan installs a water phantom 12, a polyethylene phantom 13, or a polyethylene phantom 14 in the X-ray irradiation path z ₀ , and controls the FOV of 25 cm, 35 cm, or 42 cm depending on the installed phantom. The configuration is such that phantom scan is executed with the thickness and rotation direction set below (the filter is uniquely determined along with the FOV) (the selection of thickness and rotation direction is the same as for air scan). . At this time, the X-ray tube current was 500mA, and the scan time was
It is 8mS.

Further, the control unit directs the water phantom 12 to the X-ray irradiation path.
It is installed at z ₀ and is equipped with a table that adjusts the CT value based on the data collected by scanning with an X-ray tube current of 250 mA.

In the above configuration, the phantom 11 is fixed to the cradle 10 when performing system calibration. When fixing the phantom 11, centering is performed on each phantom 12, 13.
and 14 are concentrically integrated, so 3
are performed simultaneously. After fixing the phantom, calibration is performed according to the flow shown in FIG. The setting (designation) of the update file and the execution or non-execution of CT value adjustment are performed using the calibration operation unit while talking to the display unit (CRT) (21). By setting this update file,
A control table is created in which the scan mark of the scan technique corresponding to the updated file is "1" (22). The control unit searches for scan marks on the control table while determining the scan order to minimize cooling (the X-ray tube generates heat, so it must be cooled) (23). The scan parameter of the control table set to "1" is set, and data is collected by scanning while moving the cradle 10 in the z direction (while changing the phantom) in accordance with the scan parameter (24). Calculate calibration using the collected data and update the file (25).
Operations 23 to 25 are repeated until the search for scan marks in the control table is completed (26).
When not adjusting the CT value, scan all scan marks "1" and end the calibration (27). When CT value adjustment is set, a CT adjustment scan is performed and image reconstruction processing is performed using the collected data.
The operation ends after performing ROI calculation and CT value adjustment.

Although the above embodiment has a CT value adjustment function, the present invention is not limited to this, and may include only a system calibration function.

(Effects of the Invention) As explained above, according to the X-ray tomography apparatus equipped with the automatic calibration function of the present invention, a plurality of cylindrical phantoms having different X-ray transmission characteristics are concentrically integrated and placed in a cradle. When performing calibration, it automatically selects the scan technique that corresponds to the type of calibration specified in advance from among multiple calibrations, and automatically moves the cradle in response to the selection operation. Since the phantom is moved to a predetermined position and calibration is performed, calibration can be performed easily and in a short time.

[Brief explanation of drawings]

FIGS. 1A and 1B are block diagrams of a phantom according to an embodiment of the present invention, FIG. 2 is a block diagram of a calibration scan control table according to an embodiment of the present invention, and FIG. FIG. 4, which is an explanatory diagram of the operation in one embodiment of the present invention, is a configuration diagram of an X-ray tomography apparatus. DESCRIPTION OF SYMBOLS 1... Gantry, 2... Subject, 3... Opening, 4... X-ray tube, 5... Detector, 6... Collimator, 7... Fan beam X-ray, 8... Table device, 9 ... Table body, 10 ... Cradle, 11 ... Phantom, 12 ... Water Phantom, 13 and 14 ... Polyethylene Phantom,
15...Phantom holder.

Claims (1)

[Claims] 1. An X-ray system in which a computer performs image reconstruction processing on data based on transmitted X-rays when the subject is irradiated with X-rays from an X-ray source to obtain a tomographic image of the subject. In a radiation tomography apparatus, a phantom fixed to a cradle on which the subject is placed is a phantom for calibration in which a plurality of cylindrical phantoms each having different X-ray transmission characteristics are arranged concentrically and integrated. a phantom, a means for storing scan conditions corresponding to the type of calibration, and when a calibration command is given, appropriately selecting a prespecified scan condition from among the scan conditions; , means for moving the cradle in response to the selection operation and setting the phantom at a predetermined position for calibration.