From the ISOBuster FAQ:
"Q29. Can I edit Image-Files with IsoBuster
-------------------------------------------
Nope, you cannot. The reason is complex as re-creating an image file sometimes is. Reasons are ... If a file changes size, it might very well be that the complete image has to be re-calculated. Depending of the type of image file and depending on the app that's going to be used to write the image-file, EDC and ECC code needs to be changed/added per block. The Iso and File-system might need complete re-doing ... and what about the possible UDF file system then ? Or what about changing one session and pointers to the files form other session ... And I can think of a few more issues that would occur. Therefore I haven't even started considering editing Image files."
Thorin