comparing images

Which product are you using? DICOMReader is just scanning portable media and sends the images to a defined destination e.g. the doctors reading station or a PACS. There is no viewing available in DICOMReader.

There was never a DICOMReader 1.5 so you are probably talking about K-PACS. Therefore this is the wrong forum section. I will move this thread to the right place :).

But to answer your question: select the two studies in the study browser, click "view". The viewer will load the first study. Select the display mode e.g. 1x2 and click on the little green plus sign beside the tab of the 2nd study. You can now drag the appropriate series of the 2nd study into a free viewer field.