This shouldn't be an issue if you only rank the prelim on your supplemental rank list and not your main rank list. If I remember correctly you make a supplemental rank list attached to each advanced program on your main rank list. It will only match you into the prelim if you match an advanced program. The system will attempt to match you at the highest rank on your main rank list; if you end up matching an advanced program, then the same process will happen for your supplemental rank list. Say your top 2 ranks are advanced programs (with the prelim attached in your supplemental rank lists) and then your 3rd rank is a categorical program. If you don't match the advanced programs, you won't match the prelim and the system will go down your list and attempt to place you at the categorical program.
If you place the prelim on your main rank list you could end up matching there without a radiology match. No reason to do that as there are plenty of prelims in the SOAP every year. Keep in mind if you only have 1 prelim on your supplemental list you run a high chance of having to SOAP into a prelim if you match an advanced radiology program.
