practice the gain is nominally unity in the heart and in other relatively darker anatomical regions where clinically relevant information exists the contrast gain must smoothly transition to values less than unity in the relatively bright lung region to suppress the detail which is not clinically relevant and may constitute a possible source of distraction and to minimize clipping as the mean component of the resulting image approaches the maximum intensity of 255 in other words the available contrast afforded by the maximum intensity of 255 must be carefully allocated to clinically relevant data the c drm data flow diagrams in fig3 may be optimized for real time processing in accordance with the further alternative embodiments of fig4 and 5 fig4 illustrates a second embodiment of the invention partially optimized for real time processing relative to the embodiment of fig3 specifically the fig3 division function 31 and the multiply function 35 are performed within the lut component 42 of fig4 thereby reducing the fig3 computation functions by one division function and one multiply function in fig4 input intensity x is processed by boxcar function 40 as in boxcar 30 of fig3 and the resulting local mean estimate m x is then directed to adder 41 for subtractive combination with x and which produces x u2212 m x as an output m x is also supplied to 1 m contrast mean lut function 42 the output of which is supplied to multiplier 43 and the product output of which c y m y representing a combined modified contrast and mean result is then directed to a second adder 45 m x furthermore is supplied to the mean lut function 44 which outputs as does mean lut 36 in fig3 the modified local mean m y m y is.