Patent Number: 055880363
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a block diagram showing an X-ray CT apparatus according to the embodiment of the present invention. Referring to FIG. 1, a subject, i.e. a patient, 1 lies on a bed 2 which is movable horizontally and vertically by a known drive means. The X-ray CT apparatus comprises an X-ray tube 3, which irradiates an X-ray to the patient 1 and an X-ray detector 4, which detects the irradiated X-ray. The X-ray tube 3 and the X-ray detector 4 are mounted on a gantry or frame 5 which can be turned around a predetermined axis of rotation. The X-ray CT apparatus of the embodiment is also equipped with a high-voltage generator 6 for generating high voltage to be applied to the X-ray tube 3, a high-voltage controller 7 for controlling the high-voltage generator 6, a bed drive unit 8 for driving the bed 2 and a bed controller 9 for controlling the bed drive unit 8. The X-ray CT apparatus of this embodiment is further equipped with a gantry drive unit 10 for rotating the gantry 5 around a predetermined axis of rotation and a gantry controller 11 for controlling the gantry drive unit 10. The X-ray CT apparatus of the embodiment still further comprises a main controller 12, which controls the high-voltage controller 7, the bed controller 9, and the gantry controller 11. A monitor 13 for displaying a desired image and a sub-monitor 13a for displaying the radiographing conditions are also equipped, and these monitors 13 and 13a are also operatively connected to the main controller 12. The main controller 12 indirectly controls the X-ray tube 3, the bed 2, and the gantry 5 so that the X-ray tube 3 irradiates a predetermined X-ray. The bed 2 moves to a predetermined position or at a predetermined speed, and the gantry 5 rotates at a predetermined rotational speed or at a predetermined tilt angle. The X-ray CT apparatus of this embodiment further comprises an exposure information file 14, in which exposure information data is stored as a disk or the like, and the main controller 12 is designed to set radiographing conditions according to past exposure information data stored in the exposure information file 14 and controls the bed 2, the X-ray tube 3, and the gantry 5 in accordance with the set radiographing conditions. The exposure information data may be directly inputted into the controller 12 through an on-line system. In the above meanings, the main controller 12 comprises the following elements as shown in FIG. 2. The main controller 12 comprises a central processing unit (CPU) 112a, a scan control element 112b giving instructions to the high voltage control 7, the bed drive controller 9 and the gantry controller 11, a display control element 112c giving instructions to the monitor 13 and the sub-monitor 13a, and an input/output control element 112d for the exposure information file 14. These elements 112b, 112c and 112d are operatively connected to the CPU 112a. An input control element 112e may be disposed between the CPU 112a and the display control element 112c. The functions of the controller 12 including these elements will be made more clear hereinafter with reference to the flowchart of FIG. 3. The exposure information file 14 stores exposure information, including the ID of a patient, the name of the patient, the date of exposure, scan mode, the number of the scans, a radiographed area, a scan speed, a tube voltage, a tube current, a slicing width, a reconstruction function, a posture of the patient, a direction of inserting the patient, a direction of observation, a use of a contrast medium, a type of voice, a relative table position, a tilt angle, a pause time between scans, and a scan pitch. The tilt angle refers herein to the angle of the tilt of the gantry 5 from a predetermined reference axis (the vertical direction when the X-ray CT apparatus is normally disposed). A zero tilt angle, for example, indicates that the slice plane is set in a direction perpendicular to the body axis of a patient. The scan pitch refers to the distance between adjoining slices. The main controller 12 is capable of converting, out of the exposure information, the data showing the slice-related information, that is, the number of slices, the tilt angle and the scan pitch (hereinafter referred to totally as "slice information data"), into graphic data (hereinafter referred to as "slice information image data"), which can be displayed on a scanographic image in a superimposed manner, and the desired slice information image data is inversely converted to the slice information data. The operation of the X-ray CT apparatus of the present invention will be described hereunder. FIGS. 3A and 3B are flowcharts showing the procedure for setting radiographing conditions by using the X-ray CT apparatus, in which the flowchart of FIG. 3A represents the case requiring no scanographing operation and FIG. 3B represents the case requiring the scanographing operation. First, with reference to FIG. 3A, identification (ID) number and name of a subject such as patient are entered at a step S1, and past exposure information data corresponding to the ID No. and the name of the patient is indexed by the main controller 12 from an exposure information file stored in the information exposure file 14 at step S2. In the next step S3, it is confirmed whether the past exposure information is indexed or not. In the case of "YES", the indexed information is displayed on the display sub-monitor 13a (step S4) as numerical data, and in the case of "NO", the radiographing conditions are manually set (step S5). In a step S6, it is confirmed whether the radiographing conditions are set by utilizing the displayed exposure information or not. In the case of "YES", the set radiographing conditions are set and stored in the file 14 in a step S9, and in this operation, when it is required to modify the numerical data of the radiographing conditions, such modification or correction will be done in a step S7 before the step S9. In the step S6, in the case of "NO", it is confirmed whether the indexing is to be carried out continuously or not (step S8), and in the case of "NO", the radiographing conditions are manually set as referred to in the step S5. In the case of "YES", the step returns to the step S2 to again carry out the indexing of the another past exposure information of the same patient from the stored exposure information file and continue the same operations as those described above. In the final step S10, the scanning operation is carried out under the set and stored radiographing conditions under the controlling of the main controller 12 through the high voltage controller 7, the bed controller 9 and the gantry controller 11 for controlling the setting conditions of the high voltage generator 6 for the X-ray tube 3, the patient bed 2 and the gantry 4. On the other hand, in the case where a previous scanographing is required for setting radiographing position and range of the patient, the operation will be performed in accordance with the flowchart of FIG. 3B. With reference to FIG. 3B, identification (ID) number and name of a subject such as patient are entered at a step S101 and a scanographing is preliminarily performed for setting the position and the region of the patient to be radiographed in the next step S102. The thus obtained scanographic image is displayed on the monitor 13 at a step S103. In parallel to these steps S102 and S103, other steps S202 and S203, which corresponding to the step S2 and S3 are performed, that is, the past exposure information data corresponding to the ID No. and the name of the patient are indexed by the main controller 12 from an exposure information file stored in the information exposure file 14 at the step S202. In the next step S203, it is confirmed whether the past exposure information is indexed or not. In the case of "YES", the information from the Step S103 is combined, and a slice information from the indexed exposure data is converted to a slice information image data in a step S104 by the main controller 12 and the indexed information is displayed (step S105) as numerical data on the sub-monitor 13a and slice information image data on the monitor 13 by superimposing it on the scanographic image. In connection with this step, FIG. 4A shows the slice information image data 22, which is displayed in a superimposed manner on the scanographic image 23 on the monitor 13. At this point, no relationship of relative position has been established between the slice information image and the scanographic image on the monitor. FIG. 4C shows the numerical data 21 displayed on the sub-monitor 13a. In the step S203, in the case of "NO", the radiographing conditions are manually set (step S106). In a step S107, it is confirmed whether the radiographing conditions are set by utilizing the displayed exposure information on the sub-monitor 13a or not. In the case of "YES", the radiographing conditions are set and stored in a step S111. However, this step S111 will be done through the following steps S108 to S110 in a case where it is required to modify or correct the numerical data of the radiographing conditions of the displayed exposure information regarding such as the tube current, tube voltage, scanning speed, etc., the modification is performed in a step S108. In this modification, if, for example, a touch-panel type EL display is used as the sub-monitor 13a, a switch 24 may be installed beside the section where the numerical data 21 to be modified is displayed, and the new numerical data can be set by pressing the switch 24. Furthermore, in a case of requiring the modification or correction of the slice information image data, the radiographing operation is performed with a desired tilt angle. This is performed in a step S109, and the modified or corrected slice information image data is inversely converted into the slice information (step S110). This step S110 will be performed in the case of no modification for inversely converting the data to the slice information. In the step S109, reference is to be made to FIG. 4B showing one mode of modifying the slice information image data. As is apparent from the comparison with FIG. 4A, the whole slice information image has been moved on the monitor with respect to the scanographic image, and next, the modified data is inversely converted as mentioned above. In the step S107, in the case of "NO", it is confirmed whether the indexing is to be carried out continuously or not (step S113), and in the case of "NO", the radiographing conditions are manually set as referred to in the step S106. In the case of "YES", the step returns to the step S202 to again carry out the indexing of the past exposure information of the same patient from the stored exposure information file and continue the same operations as those described above. In the final step S112, the scanning operation is carried out under the set and stored radiographing conditions under the controlling of the main controller 12 through the high voltage controller 7, the bed drive controller 9 and the gantry controller 11 for controlling the setting conditions of the high voltage of the X-ray tube 3, the patient bed 2 and the gantry 4. In the above operation steps, in a preferred embodiment of the present invention, a plurality of past exposure information data of one patient are stored in the file with respect to the respective portions to be exposed in a predetermined file position in a manner such that when a new information is stored, the oldest information is automatically vanished, and accordingly, the same numbers of the past exposure information data are stored in accordance with the passing of time. As described above, the X-ray CT apparatus of the present invention is designed to automatically set the radiographing conditions in accordance with the past exposure information. This achieves higher examination efficiency and reduced burden on the operator. Further, in the above embodiment, the whole slice information image data are moved as one mode of modifying the slice information image data, but it is needless to say that there is no need to move the slice information image data if the slice happens to be set at the desired radiographing point. Furthermore, only the tilt angle of a particular slice may be modified or the scan pitch of a particular section may be modified. In the embodiment described above, the exposure information file is provided separately from the main controller, but it may alternatively be provided in a disk inside the main controller. Moreover, a single exposure information file may be configured so that it may be shared by a plurality of X-ray CT apparatuses through, for example, a network.