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Touchstone Medical Imaging, LLC or any of their affiliates, parents, subsidiaries, Notice Of Non-Discrimination Accessibility Statement Doctors and other healthcare professionals have years of training in their field, but there are still many things they can’t diagnose simply by looking at or listening to your body. Certain medical conditions require a deeper look, usually at the tissues, blood vessels, and bones inside your body. X-rays and ultrasounds can provide some information, but when a more detailed view is required, a computed tomography (CT) scan is usually the next step. In this article, we take a closer look at how a CT scan works, what it’s typically used for, and what the procedure is like. A CT scan uses computers and rotating X-ray machines to create cross-sectional images of the body. These images provide more detailed information than typical X-ray images. They can show the soft tissues, blood vessels, and bones in various parts of the body. A CT scan may be used to visualize the:
During a CT scan, you lie in a tunnel-like machine while the inside of the machine rotates and takes a series of X-rays from different angles. These pictures are then sent to a computer, where they’re combined to create images of slices, or cross-sections, of the body. They may also be combined to produce a 3-D image of a particular area of the body. CT scans can provide detailed images of bones, tissues, and even blood vessels inside your body. However, the images that are produced by these scans appear in shades of blacks and grays. It can be difficult at times even for a trained eye to differentiate one tissue type from another in certain situations. Contrast dyes contain barium or iodine and can be given in a number of ways, including orally and intravenously (in your vein). These dyes increase the contrast level and resolution of the final images produced with the CT scan for a more exact diagnosis. However, there are a few risks associated with using contrast dyes. For example, there’s a higher chance of allergic reactions to the dyes, and they’re also not good for your kidneys. Still, every CT scan exposes you to a certain level of radiation, and a CT scan with contrast may produce better results than one without. It may also prevent the need for a repeated scan. Below is a comparison of when CT scans may be used with or without a contrast dye. A CT scan has many uses, but it’s particularly well-suited for diagnosing diseases and evaluating injuries. The imaging technique can help your doctor:
The test is minimally invasive and can be conducted quickly. A CT scan is painless, but it does take a few steps to get successful images. How to prepare for a CT scanCT scans don’t require much preparation. If needed, you can do a CT scan with or without contrast very quickly. In fact, this happens in most cases where a CT scan is needed to diagnose traumatic injuries or a stroke. If you’re scheduled for a CT scan with contrast dye, it may help to refrain from eating solid foods for up to 4 hours before your test. This is especially true if your CT scan is being done to get images of your abdomen. If your doctor is using oral contrast for your CT scan, you’ll probably be given the contrast before the day of your scan and instructed on how to prepare and drink it. Generally, you will want to start drinking the solution within an hour or two of your scan, drinking a portion of the solution every 15 minutes. Your doctor or radiologist will give you specific instructions. If you’re having intravenous (IV) contrast, a catheter will be inserted into your vein when you arrive at the testing facility. Otherwise, the only preparations you need to take before a CT scan are to remove metallic objects and medication devices from your body. This includes:
What to expect during a CT scanWhen you arrive for your CT scan, you’ll be asked to change into a hospital gown. The technician doing your scan may insert an IV catheter in your arm or leg and ask whether you have removed any metal devices or medication patches prior to your arrival. They may also review why you’re having the scan, any allergies you may have, and other special instructions. When it’s time to begin the scan, you’ll be positioned on a long narrow table, and you may be secured in place with velcro straps or other safety devices. The table will slide in and out of the circular scanner depending on which parts of your body need to be visualized. The technician will leave the room before operating the scanner and may give you instructions over an intercom. As the table moves in and out of the scanner, the machine will rotate around you making a loud noise. You may be asked to hold your breath or maintain certain positions. Otherwise, you should hold as still as possible to prevent the scanner from capturing blurry images. The entire process should take between 20 minutes and 1 hour. After your CT scanOnce the CT scan is over, the images are sent to a radiologist for examination. A radiologist is a doctor who specializes in diagnosing and treating conditions using imaging techniques, such as CT scans and X-rays. Your doctor will follow up with you to explain the results. There are very few risks associated with a CT scan. These include:
If you have an allergy to contrast dye, your doctor may choose to do the scan without contrast. If using contrast is absolutely necessary, your doctor may treat you with steroids or other medications to help prevent an allergic reaction. After the scan, the contrast dye you were given will be eliminated naturally from your body through your urine and stool. Contrast dye can cause some strain to the kidneys, so you may be instructed to drink a lot of water after your exam. CT scan results are considered typical if the radiologist didn’t see any of the following in the images:
If any atypical characteristics are detected during the CT scan, you may need further tests or treatments depending on the type of atypicality found. CT scans are an excellent tool for diagnosing problems with soft tissues, blood vessels, and other body parts that can’t be seen with X-ray or ultrasound imaging. These painless scans don’t require much preparation and can be done quickly in emergency situations. A CT scan takes less than an hour to do, but you may not get results right away depending on who is interpreting the results. Your doctor will let you know if a contrast dye is necessary for your scan and what action you need to take after the images are evaluated. A CT scan is a test that uses x-rays and a computer to create detailed pictures of the inside of your body. It takes pictures from different angles. The computer puts them together to make a 3 dimensional (3D) image. CT (or CAT) stands for computed (axial) tomography. You usually have a CT scan in the x-ray (radiology) department as an outpatient You might have a CT scan combined with another test such as a PET scan (PET-CT scan). Or you might have a different type of CT scan depending on what information your doctor wants to know. For example, a CT urogram is a different type of CT scan. This type looks at the urinary system. Why do I need a CT scan?You might have a CT scan:
Preparation for a CT scanSome CT scans need special preparation beforehand. For most scans, you have a drink or an injection of contrast medium, or both. This is a dye that shows up body tissues more clearly on the scan. You have the injection through a small thin tube (cannula) into your arm. The cannula stays in place until after your scan. This is in case you have any problems such as an allergic reaction after having the injection. CT scans of the tummy (abdomen)If you are having a CT scan of your abdomen, you might need to:
You usually have the contrast medium by injection and also as a drink. This helps to show up the gut (digestive system CT scans of the headFor some brain scans, you might have an injection of the contrast medium dye beforehand. This is to make the scan clearer. CT scans of the chestYou might have an injection of the contrast medium during the scan. This is to help show up the tissues close to the area containing cancer. For example, if your doctor wants to know if the cancer is affecting your blood vessels. It may help to show whether cancer can be removed with surgery or not. Pelvic CT scansThe pelvis is the lower cavity of the body in the area between the hip bones. It contains the pelvic organs, including the bladder, lower bowel and reproductive organs. If you are having a CT scan of the pelvis, you might need to:
Occasionally, for a rectal scan, you need to have an enema of contrast medium. This shows up on the x-ray and makes the outline of the bowel show up more on the scan. It might make you constipated. Your first couple of bowel motions will be white, but there are no other side effects. CT colonographyYou might have a very detailed scan of the bowel called a CT colonography (or virtual colonoscopy). For this test you need an empty bowel. You'll have strong laxatives and follow a special diet about 2 days before the test. You might also have a special liquid to drink called gastrorgrafin. It's a type of dye but also acts like a laxative. Your doctor or nurse will tell you about this. You might also have a medicine to slow down the normal movement of your bowel. This movement (called peristalsis) can change the scan and make it more difficult to read. What happens?When you arrive you usually fill out a checklist or questionnaire with the radiographer. They also explain about what to expect during the CT scan. Once your happy to proceed they usually give you a hospital gown to change into. It’s a good idea to take a dressing gown with you if you have one. You can then wear this on top of the hospital gown whilst waiting for your scan. Before the scan you remove any jewellery and other metal objects, bra, hair clips around the area being scanned. Metal interferes with the images produced by the scanner. When it’s time, your radiographer or an assistant takes you into the scanning room. In the scanning roomA CT scanning machine is large and shaped like a doughnut. You might have an injection of contrast medium through the cannula. You may:
Tell your radiographer if you feel anxious or claustrophobic about having a scan. Having the CT scanYou usually lie down on the machine couch on your back. Once you’re in the right position, your radiographer leaves the room. They can see you on a TV screen or through a window from the control room. You can talk to each other through an intercom. The couch slowly slides backwards and forwards through the hole of the scanner. The machine takes pictures as you move through it. The scan is painless, but it can be uncomfortable because you have to stay still. Tell your radiographer if you’re getting stiff and need to move. During the scanYou’ll hear a whirring noise from the scanner. Your radiographer might ask you to hold your breath at times. The scan usually lasts between 20 and 30 minutes. When the scan is over, your radiographer comes back into the room and lowers the couch so you can get up. This 2 minute video shows what happens when you have a CT scan. After your CT scanYou stay in the department for about 15 to 30 minutes if you had an injection of the dye. This is in case it makes you feel unwell, which is rare. Your radiographer removes the cannula from your arm before you go home. You should be able to go home, back to work or the ward soon afterwards. You can eat and drink normally. Possible risksA CT scan is a safe test for most people but like all medical tests it has some possible risks. Your doctor and radiographer make sure the benefits of having the test outweigh these risks. Some of the possible risks include: An allergic reactionRarely, people have an allergic reaction to the dye (contrast medium). This most often starts with weakness, sweating and difficulty breathing. Your radiographer will ask if you have any allergies before you have the contrast medium. Tell them immediately if you feel unwell after having it. Bruising and swellingYou might get a small bruise around the area where they put the needle in for the cannula. There's a risk that the contrast medium will leak outside the vein. This can cause swelling and pain in your hand or arm but it’s rare. Kidney problemsThere is a small risk that the contrast medium can affect your kidneys. Your radiographer checks your most recent blood test results before your scan. This is to make sure your kidneys are working well. RadiationExposure to radiation during a CT scan can slightly increase your risk of developing cancer in the future. Talk to your doctor if this worries you. PregnancyPregnant women should only have CT scans in emergencies. Contact the department as soon as you can before the scan if you are pregnant or think that you might be. Getting your resultsYou should get your results within 1 or 2 weeks. Waiting for results can make you anxious. Ask your doctor or nurse how long it will take to get them. Contact the doctor who arranged the test if you haven’t heard anything after a couple of weeks. You might have contact details for a specialist nurse who you can contact for information if you need to. It may help to talk to a close friend or relative about how you feel. For information and support, you can call the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9am to 5pm, Monday to Friday. More informationWe have more information on tests, treatment and support if you have been diagnosed with cancer. 05 Aug 2022
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