Hello I am new to the forum, but I really went thru a lot of sh... i mean "reserch" to burn saturn .cue/iso files on mac correctly.
Of course you can simply use Toast to open the image file but IT WOUNT BURN THE AUDIO FILES, in other words you will get the game to run with no music, because theres no way to burn MIXED/CUSTOM CDS or ENHANCED CDROMS on toast 10.
What you need to do is get LIQUIDCD here
http://www.macupdate.com/app/mac/19994/liquidcd (its freeware) , run the application and select 'OTHERS' from the tool menu, drag and drop the .cue file .... and burn in 8x speed (or slowest possible) -> as simple as that, you dont need to move the .mp3 tracks to wav or anything else.

NOTE: I could not find any other burning application to read .cue files on Mac. I tried-> Burn, Firestarter, Simpleburn, Burnbabyburn, NTI Dragon burn, Image Burn, BurnXfree, Shadowburner and Toast....

If you have a region issue, you can change the region with "SATHEATHER"
http://www.rysley.com/pages_html/satheader.htm or "SSaturnRegion10b" (google it) wich are simple PC applications, you need to run them either with "CrossOver Games" utility or "Wine" utility in order to change the region of the image file, works perfectly!!!!.

If the .cue file is wrong, corrupt or missing, you can run "SATHEATHER" with "CrossOver Games" utility, in the "extra" menu option of SATHEATHER you can find a "cue file maker" that runs perfectly!!!. Note: the audio files have to be .mp3 format.

If you have a .mdf file (disc images made with pc program Alcohol 120%, I believe) there are several ways to handle it:
You can open it with LIQUIDCD.
You can remane it to .iso and open it with TOAST10
You can use MISO-J utility
http://mac.softpedia.com/get/Utilities/MISO-J.shtml to convert the .mdf file to .iso file

(sick!!! it also works for psx images)
Hope to be usefull, as I said before I went thru a lot of problems and burned over 50 useless cds to come to this conclusion, LIQUIDCD is the Alcohol 120% mac equivalent when it comes to burn saturn, dreamcast, psx and ps2 games!