Low Dose CT

A CT scan is a test performed with a specialised machine that uses low dose radiation, in the xray spectrum, and a large powerful computer, to produce multiple images of the part of your body that your doctor is concerned about. The multiple images (often hundreds or thousands of images) are used by the specialist radiologist to see great detail of the various organs, bones, blood vessels and tissues of the parts of the body.

CT technology can also be used for interventional procedures. The interventional procedures that are available at Shire Medical Imaging, Miranda, include perineural exit foraminal (nerve root) steroid injections, facet joint injections, hip joint injections, sacroiliac joint injections and epidural steroid injections.

Contrast – this can be a drink or an injection (often called intravenous or IV). It is not radioactive but can make certain parts or organs of your body show up in a lot more detail on the CT scan. Most contrast agents contain iodine. Contrast is often given with certain examinations. Other types of examinations do not need any type of contrast agent. (see below for which examinations need a contrast agent injection and/or drink).

The actual CT scan test will usually take only a few minutes to perform. But there can be some preparation to do before the CT test and there will be a lot of work to process the information obtained by the CT test (both by the radiographer/technician and the radiologist doctor) before a report can be issued. This may take one to a few hours. The information in the report will then be used by your doctor to either help determine what the diagnosis is (what disease or problem you, the patient, has), or what to do next (eg further testing, what treatment to prescribe, etc). Sometimes these tests are performed to show how well a certain treatment is going or to look out for any recurrence of a previous illness, so further treatment can be given as early as possible.

1. The request form – The first step in the process is for us to find out what is on the request form that your doctor gave you for this test. This may involve you coming into our rooms here at Shire Medical Imaging, Miranda and showing the form to our front desk staff. Or you can fax or email the form to us (see contact us – Shire Medical Imaging, Miranda). Or maybe you can read out what is on the form over the phone to one of our front desk staff. We need to know what kind of test is requested, what part of the body the test is requested for and what the problems/suspected diseases/symptoms are.
2. Patient Questionnaire – to make the CT scan as safe as possible, and to minimise any side effects or complications, we need to know a few things about your medical history. This may include if you have any kidney disease, thyroid disease, blood diseases, cancers, allergies or diabetes. It would also be beneficial for us to know if you have had any CTs before, to get previous examination results for comparison and if you have had any bad reactions to previous CT contrast agents (eg IV iodine).
3. Fasting – Sometimes the examinations can give you a nauseous feeling. Most people do not vomit, but to be on the safe side, we advise that you refrain from eating or drinking anything for 4 hours before a CT examination, just in case. If you have a medical disorder that makes this difficult, for instance diabetes, please speak to the booking staff who will advise on the best way to proceed.
4. Blood tests – patients with kidney disease or anyone with reduced kidney function (even if you do not have any symptoms associated with it) are at increased risk with some of the CT examinations. So we believe that it is important to check on the kidney function before the test so that we can adjust the procedures to minimise the risk of kidney trouble. So we will advise you and your doctor to obtain a blood test for the kidneys if need be.
5. Adjusting medications – Some medications can, in combination with the CT contrast agents, cause medical problems after a CT examination. That is why we will ask you which medications you are taking. We can advise you and your doctor how to best manage the medications around the time (before and after) the CT examination. These medications include
   • Metformin
   • Blood thinners
6. Please see information about your specific examination for details on pre examination preparation.

Some CT examinations require administration of iodine contrast (either orally or intravenously or both). Iodine is a chemical that is naturally occurring in the human body. But it has been discovered that extra Iodine can make certain organs (like the liver, spleen, lymph nodes and blood vessels with intravenous contrast and bowel, stomach and oesophagus with oral contrast) a lot easier to see (and more accurately assessed) on the CT scan images, and can make diseases easier to see (and more accurately assessed). Iodine is not radioactive, but is easy to see on xray images. If the Iodine is required to be taken orally for the CT examination, it is usually drunk over 45 minutes before the examination. If the Iodine is required to be injected, a cannula (plastic needle) will be inserted just before the CT examination and the IV contrast will be given over several seconds during the examination.

1. Some people get a hot feeling all over the body after IV injection of Iodine. This does not last long and it is not dangerous. Some people get a feeling of wetting themselves (although it is very rare to actually be incontinent during a CT examination). But this also is not dangerous and passes quickly. Some people get a slight nauseous feeling, but this also passes relatively quickly. (this can occur with both intravenous or oral Iodine). It is rare to actually vomit during or after a CT examination.
2. A few people have an allergy to intravenous Iodine injections. This is different and unrelated to an allergy to antiseptic iodine that is put onto the skin. However, this allergy can be dangerous. So it is important for the technical staff and the radiologist doctor to be told about any allergies you have.
3. Mild reactions include flushing, nausea, pruritus, vomiting, headache and mild urticaria. They are usually self limited and resolve without specific treatment. Mild reactions may be seen in up to 3% of patients after non-ionic low-osmolality contrast agent administration.
4. Moderate contrast reactions include severe vomiting, marked urticaria, bronchospasm, facial/laryngeal oedema and vasovagal attacks.
5. Severe contrast reactions include hypovolaemic shock, respiratory arrest, cardiac arrest, pulmonary oedema and convulsions. Severe reactions are uncommon, occurring in 0.04% to 0.004% of non-ionic low osmolar iodinated contrast injections (i.e. 1 in 2,500 to 1 in 25,000 contrast injections). The risk of death is rare (1 in 170,000).
6. Other possible, although rare, complications and side effects of an intravenous injection of iodine include extravasation (where the iodine comes out of the vein into the tissues in the arm), infection or bleeding from the puncture site, which may require treatment.

1. If oral contrast is required for the examination, a technician will come to the waiting room and give you a drink to drink before you are called into the examination room. You will be given time to drink the drink.
2. A technician will come to the waiting room and call you into the examination room. You will be asked to get changed into an examination gown, to avoid any metal parts of clothing or other objects from interfering with the CT examination. The technician will then take you into the examination room and show you where to lie down, usually on your back on the table of the CT machine.
3. After some machine preparation, the table with you lying on it will move through the CT ring and a scan will be taken. This may happen a few times.
4. If an injection of contrast is required, an intravenous cannula will be placed in an arm vein, in preparation for the injection during the scan.

If you have been given an IV injection of iodine contrast agent during your examination, we advise you wait in our department waiting room for at least 15 -30 minutes after the examination just to make sure you are OK after the examination.