I can only create an cdr image, but not iso. Is it possible to create an iso image using mac standard software (disk utility)?
The 'cdr' files match the ISO spec. So once you create the image you can safely rename the file to .iso and it will work fine.
Create a folder of the stuff you want to put in the image. Launch Disk Utility and choose File -> New -> Disk Image From Folder. In the Select Folder to Image dialog box that appears, select your folder and click Image. In the resulting New Image From Folder dialog box choose DVD/CD Master and None from the Encryption pop-up menu. Save the image to the Desktop.
Open Terminal and type:
cd ~/Desktop hdiutil makehybrid -iso -joliet -o Test.iso Test.cdr