Okee in Medical Imaging

Contrasts and tracers

  • What are contrasts and tracers?

    Contrasts and tracers are special liquids that go into your body and change the way your pictures look. There are lots of different types of contrast, some you drink and others that need to go into a vein with a little straw called a ‘cannula’.

    Will I need them?

    It depends on what type of pictures you’re having taken:

    Ultrasound and X-ray: You won’t need contrast for any pictures here, including OPG/CEPH pictures.

    CT and MRI: It depends on the pictures needed. If your parents aren’t sure, they can contact Medical Imaging to find out. Sometimes it is decided while you are having your pictures taken.

    Fluoroscopy: You will probably need contrast for these pictures. It might be a drink called barium, or sometimes another type of contrast which your nurse can explain to you.

    Nuclear Medicine: You will need a tracer for all pictures. Most of these are given via a cannula into a vein, but there are a few types of pictures that use a drink instead.

    What you need to know

    Contrasts and tracers come in different forms – some you drink, and others need to go into your body in other ways. Ask your mum or dad to tell you what you need.

    Oral contrast (drink)


    CT: The oral contrast is almost tasteless, but you can mix it with cordial if you like. You’ll need to drink between 1 to 2 cups of it over the hour before you can have your pictures taken.

    Nuclear Medicine: The oral tracer goes into a small amount of normal milk, and you can’t taste it either.

    Fluoroscopy: the oral contrast is called 'barium'. This is a thick milkshake that your nurse can flavour with either strawberry or chocolate.

    IV contrasts/tracers


    CT, MRI and Nuclear Medicine all use contrast or tracers that go into a vein (intravenous) - IV). For this you need a tiny straw called a ‘cannula’. Before this happens, your skin will be numbed – which means you can’t feel things as much. This means that the straw going in should not bother you.

    The straw is soft and bendy, and once it’s in place, you shouldn’t be able to feel it. It can be a good idea to look at a book or an iPad while the cannula goes in, and remember to stay still, this makes it much easier and quicker.

    CT contrast might make you feel a bit strange – you might feel warm, get a funny taste in your mouth or feel like you need to go to the toilet. This feeling will go away about a minute after it starts, so you just need to stay relaxed and still until it stops.

    Other contrasts:

    Fluoroscopy: you may need contrast inserted into another body part, depending on what kinds of pictures you need. This is usually done with a small tube called a catheter.

    What parents need to know

    How do I know if my child is going to have contrast?

    If your child is having contrast, in general, it will be noted on their appointment letter. In some cases, it may not be known that contrast is required until the first image is taken. For this reason, we recommend you avoid promising your child won’t need a needle if they are having imaging done in MRI, CT or Nuclear Medicine.

    What if I don’t think my child will cope with having contrast?

    The RCH Medical Imaging staff are experienced with children of all ages, and employ a variety of strategies to make having contrast easier. Given that, there are still a number of reasons why your child may not cope with having contrast. This can be due to anxiety, age, or developmental delay. If you feel that your child will require additional preparation, support, or sedation for their appointment and this has not been booked, please contact Medical Imaging reception on 03 9345 5255 to discuss appropriate options.

    What do I need to do before the appointment?

    If your child requires IV contrast, they will be offered a numbing solution, which will be applied prior to having their IV inserted. This can be up to 45-60 minutes before their images are taken. It is a good idea to bring some quiet activities that don’t take up too much space to keep your child busy while waiting for their appointment. Some contrasts require fasting, please check your appointment letter or contact Medical Imaging reception.

    What should I tell my child?

    It is important to be honest but considerate of your child’s developmental level. It is a good idea to start by explaining to your child why they need the scan. Explain that having contrast will allow the people at the hospital to get the best pictures. Children over the age of 5 generally cope best when they are informed of their procedure the week prior, and are given the opportunity to process the information and ask questions. Children under 5 are best told about their appointment the day before. You are encouraged to explore the Okee app games and to discuss the content with your child before their appointment.

    How long does having contrast take?

    Please check your appointment letter, however you will generally be required to be at the hospital for around 1 hour prior to imaging. This allows staff time for preparation and the numbing application before inserting the cannula prior to imaging. If your child requires oral contrast in CT, this will consist of between 100-1000ml, taken over the hour prior to imaging.

    Are there any risks to having contrast?

    There is a very small chance your child may be allergic to the contrast and require medical support however this is extremely rare. Please inform the medical imaging staff if your child has experienced a reaction previously. For more information about the risks of contrast, please contact Medical Imaging reception on 03 9345 5255 and ask to speak to the Duty Radiologist.