Patent Number: 062597671
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The X-ray device shown in FIG. 1 includes an X-ray source 1 which is controlled by an X-ray generator 2. The X-ray source is mounted on a stand (not shown) so as to be displaceable at least in the vertical direction. The X-ray device also includes a patient table which is symbolically represented by a table top 3; underneath the table there is arranged a digital image detector 4 with a matrix-like array of detector elements. In addition to the patient table, or instead of the table, there may be provided a grid or Bucky wall stand with such an image detector. The size of the exposure field formed on the image detector 4 by the X-ray source 1 is adjusted by means of a diaphragm unit 5. The diaphragm aperture, i.e. the angle of aperture of the radiation beam denoted by dashed lines in the plane of drawing, is determined by a first set of collimators 51 which are made of, for example lead and whose edges extend perpendicularly to the plane of drawing of FIG. 1. There is also provided a second set of collimators which, however, is not shown in FIG. 1; these collimators have edges which extend parallel to the plane of drawing and determine the angle of aperture of the radiation beam 10 in the direction perpendicular to the plane of drawing. The diaphragm aperture can be adjusted by means of a motor 52 which is accommodated in the diaphragm unit 5 (unlike the situation shown in the drawing). The motor 52 is controlled by means of a diaphragm controller 53 which co-operates with a workstation 6. The diaphragm aperture can also be adjusted manually by the examiner while using an adjusting member 54. The actuation of the adjusting member 54 is detected by the diaphragm controller 53. The examiner can check the size of the adjusted exposure field prior to an exposure by using a light localizer (not shown) which is included in the diaphragm unit 5 and produces a light beam which is bounded by the collimators 51 etc. in the same way as the X-ray beam 10 during the exposure. The distance between the X-ray source and the image detector is measured by a measuring device 55 and the measured value is applied to the diaphragm controller 53. The workstation 6 controls inter alia the diaphragm controller 53 and the X-ray generator 2. To this end it can access a storage device 61 with a data base in which a respective data set is stored for each of a plurality of organs. Each data set contains the optimum exposure parameters for the relevant organ in the normal case; it also includes a value concerning the size of the exposure field to be adjusted. This adjustment value can be applied to the diaphragm controller 53 in order to adjust the exposure field while taking into account the measured distance between the X-ray source and the image detector. Moreover, the workstation can reconstruct an X-ray image from the signals of the X-ray image detector 4 for display on a monitor 62. On the other hand, the workstation can also reproduce a patient and exposure list on the monitor, which list contains not only the name of the patient but also the organs or parts of the body to be radiographed. This list can be applied to the workstation 6, for example via a so-called RIS (Radiology Information System) link. There is also provided an input unit 63, for example a keyboard and/or a touch screen unit, for communication with the workstation 6. The patient table 3 (and possibly also the above-mentioned grid wall stand) with the X-ray source 1 and the diaphragm unit 5 are present in a room other than that in which the components 6, 61, 62 and 63 are installed. The examiner is active in both rooms for each X-ray exposure: during the adjustment of the exposure parameters by selection of the organ as well as during the initiation of an X-ray exposure the examiner will be present in one room while he or she will be present in the other room during the positioning of the patient and also during manual adjustment of the diaphragm unit, if any. The FIGS. 2A to 2E show parts of flow charts which govern the adjustment of the exposure field. In conformity with FIG. 2A, after the selection of an organ or the fetching of APR data, in the step 101 it is checked whether a given flag has been set (M-flag=1) or not (step 102). When the flag has not been set, in the step 103 the workstation generates an instruction for the diaphragm controller 53 so as to adjust the size of the exposure field while taking into account the distance between the X-ray source 1 and the image detector 4 in conformity with the adjustment value stored for the relevant organ to be imaged. However, if the flag has been set, the adjustment remains the same. As is shown in the FIGS. 2B . . . 2E, the flag can be set and reset in dependence on four different events. In conformity with FIG. 2B, in the case of manual adjustment of the diaphragm aperture by means of the adjusting member 54 (block 110) the flag is set in the step 111 (M-flag=1). However, in the case of a change of patient (block 120), the flag is reset in the step 121 (M-flag=0, FIG. 2C). The same takes place in the step 131 as shown in FIG. 2D after the initialization of an X-ray exposure (block 130) or in the step 141 upon a (new) start of the system 140. The operation of the X-ray unit during the execution of a patient and exposure list, reproduced on the monitor 62 by the examiner, will be described in detail hereinafter. It is assumed that the list successively specifies a first exposure in the form of an exposure of the organ 1 (for example, a lateral chest exposure) of the patient A and a second exposure of a second organ of the patient A, for example lung p.a.(even though the lung is to be imaged in both cases, the p.a. and the lateral exposure of this organ are treated as different organs with a different set of exposure parameters). It is assumed that the patient and exposure list specifies as the third exposure an exposure of the same organ (lung p.a.) of a further patient B. For the first exposure the examiner positions the patient A on the patient table (or in front of said wall stand) and adjusts the size of the exposure field on the diaphragm unit by means of the adjusting member 54, thus setting the flag as shown in FIG. 2B. The examiner subsequently enters the room in which the workstation is located and adjusts the X-ray device for the first exposure, i.e. the exposure of the patient A with the organ 1 is selected, so that an adjustment value for the exposure field is fetched. However, because the flag is set, in conformity with the flow chart shown in FIG. 2A the exposure field is not adjusted to the fetched adjustment value. The examiner then triggers the first X-ray exposure, with the result that (in conformity with FIG. 2D) the flag is reset in conformity with the step 131. If desired, the patient table may be constructed so that the X-ray source 1 and the image detector 4 are simultaneously displaceable in opposite directions so that slice images can be formed. In such a slice imaging mode usually a series of images of slices in different positions is formed, so that in this mode a (slice) image may not give rise to the described resetting of the flag. Therefore, when the examiner selects the second exposure on the workstation, in conformity with FIG. 2A the adjustment value for the second organ (lung p.a.) is fetched and adjustment is performed by the diaphragm controller 53 and the motor 52 so that the manual adjustment concerning the previous exposure is overwritten. The examiner then positions the patient A in such a manner that the second exposure can be made. When the adjusting member 54 is then actuated, the preset of the diaphragm unit is changed accordingly by the adjustment value fetched for lung p.a. from the memory 61, so that the flag is set again. When after this second exposure the third exposure (patient B) in the list is selected in the workstation 3, the flag is reset because of the change of patient (step 121), even if the same organ as during the preceding exposure is to be imaged. The manual adjustments carried out for the second exposure are, therefore, overwritten in conformity with the adjustment value preset for the third organ to be imaged (lung p.a.). If necessary, the examiner can change this preset again by means of the adjusting member 54. The described routine illustrates that the X-ray device offers the examiner very good economics in combination with high flexibility in respect of adjustment. All references cited herein are incorporated herein by reference in their entirety and for all purposes to the same extent as if each individual publication or patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety for all purposes.