Diagnostic imaging

St. Mary’s provides comprehensive diagnostic imaging on an in-patient and out-patient basis. Over 70,000 examinations are performed each year. Our staff is committed to providing patients with a compassionate, caring environment with the latest in technology and innovation in medical imaging.

For your convenience, the Diagnostic Imaging department is located on the first floor of the hospital.

The department offers the following services:


Ultrasound examinations produce images of soft tissues and are traditionally associated with gynecologists and obstetricians providing examinations of pregnancies, with no danger to the unborn child. However, the majority of ultrasounds performed at St. Mary’s General Hospital are of the abdomen and pelvis. While Ultrasound is a powerful diagnostic tool, it also serves as a guidance system, to pinpoint the exact location of an organ for treatment or surgery.

Mammography and OBSP (Ontario Breast Screening Program)

mammography technician is shown positioning a patient at the mammography unitAccredited by the Canadian Association of Radiologists, St. Mary’s offers digital mammography to women in Waterloo Region, based upon physician referral. A mammogram is a low dose x-ray of the breast tissue.

This test can be done safely on patients at any age where there is a clinical breast concern or a strong family history of breast cancer. However, a physician may order this test on women in their 40s, as a baseline exam, then more frequently beginning at 50 years of age as a routine screening. If there is a chance you may be pregnant, please consult with your doctor before having a mammogram.

Our full field digital mammography equipment is state-of-the-art and produces the highest quality images with precise detail. Patients find this new digital technology to be more comfortable. Our specialized technologists are trained to make the whole experience as pleasant as possible.


  • Do not wear deodorant, body powder or lotion on breasts or underarm area on the day of the test.
  • Wear a two-piece outfit for your comfort.
  • If you have had a mammogram before in another institution, please bring those previous images with you.

Routine screening mammogram

This exam has to be ordered by a doctor and a requisition is required.

You will be asked to undress from the waist up and be given a gown. The breast is placed onto the mammography unit and a compression paddle will come in contact with the breast gently spreading the tissue out. The pressure lasts for a few seconds while the x-ray is taken and then releases automatically. Although the pressure can be a bit uncomfortable, it does not harm the breast and helps produce a better image for the radiologist. Usually four pictures (two of each breast) are taken 


Allow 15 to 20 minutes.

Ontario Breast Screening Program (OBSP)

St. Mary’s is an OBSP site where patients 50 years and older can self refer at no cost. They can also be referred by their family physician. It is recommended that women between 50-74years of age have a screening mammogram every two years.

This exam includes a basic mammogram as described above.


Allow 15-20 minutes.

To book an appointment at St Mary’s Breast Screening Centre, call 519-749-6456.

Learn more about the Ontario Breast Screening Program.

Diagnostic mammogram

This incorporates a screening mammogram with extra views of any areas of concern. There is the potential for an ultrasound as well.

Please allow about one hour.

Breast Needle Localization

This is done on the same day of the surgery (before surgery) and is used to locate a breast lesion (area of concern) seen on a previous mammogram or ultrasound.

Using mammography or ultrasound guidance, we will place a needle and a small wire into your breast. Once we are sure the area of concern is localized, the needle is removed and the guide wire remains in place for your breast surgery.

You will receive instructions from your surgeon and the radiology nurse before the procedure. It is important not to eat or drink a certain numbers of hours before the surgery, and this will all be explained to you beforehand. This is usually done as a day surgery case.

Any questions regarding mammography can be answered by contacting 519-749-6635.

CT Scan

A CT Scan (Computerized Tomography), uses x-rays to provide two- or three dimensional images of your body. This is different from routine x-ray examinations which produce a flat planar image. Some scans require the administration of an intravenous contract medium called a “dye”.


Elective X-ray at St. Mary’s operates from 8:00 a.m. to 5:00 p.m. Monday to Friday. Outside of these hours, x-ray services at St. Mary’s are for emergency cases only.

For more information contact

Central Booking

*Please note: Urgent matter should not be communicated over email. Please call the Central Booking line.

Referring physicians can find patient referral information here.