That is NOT correct about 'if something is wrong they won't let you leave'. I've left with a liver tumor and the techs were all smiles and back patting. The people doing the CT scan check for unfuzzy images, etc. and cannot dx lumps, bumps, etc.
I was told a few weeks ago that many radiologist now work from home on their computers. Depending on how many film they get it a day, it usually takes two days for them to compare to old scans, check new scans, write reports and send them by email to the doctor.