What to expect during a CT scan

St. Joseph’s Hospital technologists answer six questions about CTs

When you are sick or injured, your healthcare team will use many tools to find out what’s wrong to get you better. Sometimes that includes imaging diagnostic machines to get an inside look of your anatomy. One such device is a CT scan.  

CT stands for Computed Tomography. Essentially, it’s a sophisticated X-ray machine. The imaging system takes multiple axial images as opposed to one-dimensional images a traditional X-ray produces, explains Marsha Cobb, R.T.(R)(CT)(BD), technologist at St. Joseph’s Hospital. Using a computer, all the images taken are combined to produce a detailed look at the body’s anatomy.

St. Joseph’s/Candler offers the latest imaging technology to help patients feel more comfortable and get them in and out as quickly as possible. Our CT scanners reduce radiation exposure to the patient and operator while providing faster, more detailed results to the radiologists.

At St. Joseph’s Hospital, we offer the GE Revolution CT Scanner, one of the quickest imaging machines available. It has the capability to scan the entire heart in one heartbeat, Cobb says. A scan of the entire brain just takes one rotation of the CT tube, which is about one second.

“That’s very good when you have trauma patients, patients that want to move and can’t be still or patients that are on a ventilator and need to get back to the unit quickly,” Cobb says.

St. Joseph’s/Candler has eight CT scanners at four imaging locations:

• St. Joseph’s Hospital (two in imaging and a third in the emergency department)
• Candler Hospital (three between inpatient and outpatient imaging)
• SJ/C Imaging Center - Pooler
• SJ/C Imaging Center – Bluffton

With more and more people needing CT scans, it’s important to have a good understanding of the machine and not fear it. Here are six things you should know about CTs:

1. Who needs a CT scan?

   A physician will request a CT scan to view the inside anatomy of a patient. Lots of times, insurance will require an X-ray before a CT scan, Cobb says. When physicians need more detailed images, a CT scan is ordered. CT scans also are often the first imaging diagnostic tool used in trauma situations, such as stroke or heart attack.
   

2. What does it look for?

   CT is a useful imaging tool for almost every part of the body, says Seleta Lee, R.T.(R)(CT)(BD), technologist at St. Joseph’s Hospital. It is most commonly used in imaging the heart, brain, abdomen and bowel (gallbladder and appendix, for example), spine and other organs of the body. CT images can show blood clots, aneurysms, lung nodules and calcium scoring around the heart. Additionally, CT can be used for procedures and biopsies, Lee adds. For example, cardiologists can use CT images of the pulmonary veins like a map to help guide them during an ablation procedure.
   

3. How long does it take?

   Thanks to advances in technology, CT machines are faster than ever. How long a scan lasts depends on the area of the body being scanned. The longest CT scan is about 10 minutes, and the majority of that time is used for hooking the patient up to the machine, Lee says. Outpatients will first meet with a registrar and nurse to ensure everything is in order before the imaging test.  
   

4. Is it safe?

   CT scans do use radiation, but with advancements in technology, patients are exposed to less radiation than previous versions of CT scanners. St. Joseph’s/Candler also uses radiation dose reduction software, Cobb says.
   

   The majority of CT scans also use contrast. Contrast is an agent that improves the visibility of the anatomy for clearer images. Contrast is safe for most patients. The imaging team of nurses and technologists ensure the patient has no iodine allergy and proper renal function, as contrast could have an impact on weakened kidneys. Some patients experience a warm sensation following a contrast IV, but that feeling typically lasts less than a minute, Lee says. A few patients may also experience nausea.
   

   Patients are encouraged to drink a lot of fluids following a CT scan to help flush everything out of the kidneys and bladder, Cobb says.
   

   The majority of outpatients can drive following a CT scan. A driver is required when a CT machine is being used for a procedure or biopsy that requires a level of sedation.
   

5. What is the difference between a CT and MRI?

   Lee and Cobb find many patients confuse CT and MRI. Both are effective and safe imaging diagnostic tools, but they do have differences. The main difference is CT uses radiation while MRI does not. MRI uses a magnetic field, radio waves and a computer to create images.

   Related Article: What to expect during MRI
   
   Another difference is the sound. CT scans sound like a small plane getting ready for takeoff, Lee describes.  MRI machines are noisy, making a knocking sound; however, patients have several options to reduce the noise they hear.
   

   The feeling of claustrophobia is also a difference. Not all, but some patients may experience claustrophobia during an MRI. A CT machine differs from an MRI in that a CT’s depth is shorter, which Cobb and Lee compare to a doughnut, in which the bed glides in and out. An MRI machine has a longer opening in which the bed remains during the scan. CT scans also typically are faster than an MRI.
   

   A lot of times it’s the physician’s preference as to whether a patient has a CT, MRI or other imaging tool. Some patients may have an implant or hardware in the body that makes them not a candidate for MRI. If a physician is looking at an ankle or foot, for example, an MRI shows tendons better than a CT.
   

6. When do I get my results?
   Following a CT scan, the images are sent to a radiologist, which is a physician trained to read imaging and diagnose and/or recommend treatment. The radiologist’s findings are sent to the ordering physician and available to patients within 24 hours, Lee says. Patients – most commonly stroke victims – who have a CT scan in the St. Joseph’s Hospital emergency department have their results faster, typically while they are still in the ED, Cobb adds.

For more information about all of St. Joseph’s/Candler imaging services, visit our website.

Coming Thursday: Learn how CT Lung Cancer Screening is finding cancer early and saving lives