AUTOMATIC SETTING OF THE CONTRAST RANGE O F WHOLEBODY SCINTIGRAMS WITH A HISTOGRAM METHOD

Aim: To get standardised results on the display of whole body scintigr ams regarding an optimal contrast setting (using linear scaling), an a lgorithm was developed, which can be used for an automatic setting of an upper intensity truncation value. Methods: From the integral of the gray level histogram of 30 randomly selected whole body images upper threshold values L-A were defined, where a certain area percentage A ( 80% less than or equal to A less than or equal to 99.5%) of all pixels with intensity > 0 are contained in the intensity range. independentl y an interactive upper level L-vis of the contrast range was determine d by two observers to get an optimal visual appearance of the image. R esults: For the threshold levels with an area percentage A of 92%...98 % (L-92...L-98) a very close linear correlation (r >0.9) was found to the visual levels. Levels resulting to area percentages A <92% or A >9 8% correlated worse to the interactive values, Based on our results we propose as a good definition for an upper threshold on whole body sci ntigrams with dual intensity ranges: Range 1 (high activities): Upper threshold = min (2.5 x L-95, 100%), Range 2 (low activities): Upper th reshold = min (1.25 x L-95 100%). Conclusion: The procedure is well su ited for an automatic definition of the contrast settings of whole bod y scintigrams. It can be implemented easily; its use gives a substanti al contribution to the standardisation of the documentation of scintig rams.