This is the link to Commision on Accreditation of Allied Health Education Programs. It is important to check with this association to ensure a viable education. These are the colleges and cities within Illinois that offer this in Diagnostic Medical Sonography:
College of DuPage - Glen Ellyn, IL
Harper College - Palentine, IL
John A. Logan College - Carterville, IL
Northwestern Memorial Hospital - Chicago, IL
Rush University - Chicago, IL
Southern Illinois University-Carbondale - Carbondale, IL
Once you have determined which, if any, school is in your area, check their website for prerequisites in General Education, grades required for classes, and if you are up to the challenge. There will be a lot of time invested just to get to the point of applying for the sonography course, Cardiac, Vascular, or General. This is an additional 30 - 40 credit hours.
Once you get your 40 or so General Education credits finished, you will then complete with many for the few opportunities for the internship. High GPA, hospital experience, job shadowing, and other factors are considered before the interview with the school's Admission Committee. I live in Michigan and there are 25 positions available each year. In Florida, where I was in an internship, there are only 12 positions statewide.
As luvtoscan points out, you can get a certificate in sonogrpahy IF you already have a medical degree but if not, you must first get an Associates Degree.
Check the Bureau of Labor Statistics, Occupational Handbook (www.bls.gov/oco/) to see if the money you would make in this field is up to your expectations.
Best of luck to you!