in one embodiment , as shown in fig1 , an imaging apparatus 2 includes an imaging device 4 with a radiation source 6 , a radiation detector 8 , and a collimator 10 . the imaging device 4 may be an x - ray machine . the apparatus 2 may be controlled by a control unit 12 that includes a processing unit 14 . a patient 18 positioned on a patient positioning table 16 may be moved into a beam path 20 emitted by a radiation source 6 . a series of recordings of a region under examination of the patient 18 may be made using the imaging device 4 . an image sequence may be recorded during a medical intervention with continuous irradiation of the patient 18 . a method for capturing an image sequence is shown in the block diagram of fig2 a . a reference image b r with high image sharpness is taken with a high radiation dose d h ( see fig2 c ). the reference image b r may be stored and / or displayed on a display 22 . the display 22 provides the treating physician with visual assistance during the medical intervention . a series of current images b a of the entire region under examination may be taken . the current images b a may correspond to the reference image b r with respect to their size and position relative to the patient . a lower radiation dose d n is used . for example , the current images b a are less sharp . the processing unit 14 may automatically compare each of the current images b a with the reference image b r in respect of a visualization parameter , for example , the grayscale value of each image pixel . a predefined adjustable threshold value may be used for the comparison . if the two images coincide , for example , if the changes in the current image b a are below the threshold value , a further current image b a is taken . if changes exceeding the threshold value are detected in the current image b a compared to the reference image b r , depending on the position of these changes , an image detail 24 is captured using a high radiation dose . in the current image b a according to fig2 a , the changes are in a first quadrant i of the image b a . the control unit 12 accordingly controls the collimator 10 to mask out part of the beam path 20 . only the first quadrant i is captured as an image detail 24 . the size of an aperture 26 of the collimator 10 may be adjusted so that only a quarter of the total image , such as the first quadrant i , is captured . the image detail 24 is then automatically inserted into the reference image b r , for example , at the position where the change was detected . for example , the image detail 24 is inserted in the first quadrant i of the reference image b r . an updated reference image b r may be obtained , stored , and simultaneously displayed on the display 22 . the updated reference image b r may be used as the basis for comparison with the subsequent current images b a . fig2 c shows a radiation dose d and a dose - area product p . fig2 c shows radiation dose per irradiated area over time t . the item instants t 0 to t 6 specify the times where the acts of the method are carried out . when the reference image b r is taken , a high radiation dose is used . the high radiation may be about 100 % of the radiation dose d . the beam path 20 may remain unrestricted when the reference image b r and the current image b a are taken , so as to produce a maximally large - area complete image , as shown in fig2 b . as the reference image b r has a size which is defined as maximally large , the dose - area product p may remain 100 %. when the current image b a is taken , a much lower radiation dose d is used . the lower radiation dose d may be about 25 % of the maximum possible radiation dose d h . the radiation dose d is regulated via an x - ray generator ( not shown in greater detail here ) of the x - ray device 4 . the generator may be controlled via the control unit 12 . the current image b a may be as large as the reference image b r . the dose - area product p may be only about 25 % based on the low radiation dose d n . in one embodiment , the collimator 10 is not used to screen off the beam path 20 , apart from the first quadrant i in which a change was detected , until capture of the image detail 24 at time t 4 . to capture the image detail 24 , a maximum radiation dose d h is used . as the image area is restricted to a quarter of the total image area in this case , the dose - area product is only 25 %. as shown in fig2 c , this method is particularly non - damaging for the patient , while at the same time the images displayed to assist the medical personnel have optimum image quality . while the invention has been described above by reference to various embodiments , it should be understood that many changes and modifications can be made without departing from the scope of the invention . it is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting , and that it be understood that it is the following claims , including all equivalents , that are intended to define the spirit and scope of this invention .
a medical imaging system is provided . the medical imaging system includes an imaging device with a radiation source and a detector , a control unit ; and a processing unit . the processing unit is operable to compare a stored reference image taken using a high radiation dose with a current image taken using a lower radiation dose . the control unit is operable to trigger the imaging device to take a further image using a high radiation dose based on the comparison .