The role of the translation table in cardiac image display

Abstract

No translation table is perfect. Some tables can assist in the identification of defects by highlighting contrast in the image, with either different color scales or gammas. However, this runs the risk of decreasing specificity and increasing the number of false-positive findings. Tables like this will tend to emphasize defects at certain points on the table, usually where there is a color change, and will create the perception of a change at that point, whereas changes of similar magnitude at other points will be much less apparent. A purist would make the argument that the reader, not the image display parameters, should be what determines whether a study is normal or abnormal and would argue for the use of a linear gray scale, the translation table that most faithfully reflects the uptake on different parts of the image. However, there is no one correct table to use; rather, it is more a matter of preference and familiarity. The reader must be aware that the image will appear differently on different translation tables and with color scales and should proceed cautiously when viewing an image on an unfamiliar translation table or with unfamiliar medium. These differences strongly support the case for using image quantitation, because it is the actual numbers, representing counts of radiotracer distribution, that constitute the image and are the most objective determinant as to whether a defect is real or not. If the reader is aware of this and is able to incorporate quantitation in the final interpretation, then he or she is more likely to make the correct interpretation.