Can I set Zbrush to always render one type of file extension

Hi when I do a BPR render, and then press the composite thumbnail to save the file, I then have to set the file type I want to save as ( JPEG , PDS , PNG, ect.) in the windows file save window. Is there any way I can automatically set this to always save as a PNG for example? The default is JPEG, so every time I have to change it.