Computed Tomography (CT)

"CT" is an acronym for computerized tomography, which is a process that uses multiple X-ray detectors to create images in multiple area of your organs, bones, blood vessels and soft tissues. A CT scan is a commonly used, noninvasive test that helps physicians diagnose a large number of medical conditions. The CT scanner itself is a large doughnut-shaped machine equipped with X-ray detectors, which are contained in a central ring. During the scan, you will lie on a table that slides in and out of this ring. All of Overlake's CT scanners are state-of-the-art, multi-detector scanners.

All CT scans performed at Overlake are completed by a CT technologist, who is licensed in the state of Washington and holds an advanced certification with this exam. All of Overlake's technologists practice low-dose techniques to keep the radiation exposure to the patient at a minimum. At times, contrast dye is injected through an intravenous line (IV) during the scan. You may also be asked to to drink oral contrast prior to the CT scan, which is given to you at the time of your arrival. Please contact us with any exam-specific preparation questions.

One of our primary goals is to keep your radiation exposure as low as possible during your exam while maintaining the highest level of quality.  Different exams have different amounts of radiation involved. As a reference, an individual is exposed to approximately 100 milligray of background radiation a year from sources such as the sun's ultraviolet rays, and small traces of radioactive isotopes in the soil.

Exam Preparation

• Prior to your scheduled imaging appointment, Overlake Medical Imaging will call you to discuss exam-specific instructions, review your health and insurance information, and answer any questions that you may have.
• Follow the specific preparation instructions listed for your specific type of CT exam. These may include dietary restrictions and/or instructions on drinking fluids. Take your medication as usual, unless your physician has given you other instructions.
• If you’ve had an allergic reaction to a contrast agent in any prior imaging exam, please notify our staff before your appointment.
• Leave your valuables at home. All jewelry and any metal objects in the area being scanned must be removed prior to the exam.
• Wear comfortable clothing without zippers, snaps or metal buttons. You may also change into a hospital gown or scrubs after arriving.
• Please notify the technologist if you are pregnant or could be pregnant.
• Please bring all relevant prior examination films or studies (CT, MRI, ultrasound, X-ray) with you on the day of your exam.
• We typically request that you arrive 15 minutes prior to your exam. However, we may ask you to arrive earlier if your exam requires that you drink oral contrast.

During Your CT Scan

• The technologist will help position you comfortably on a cushioned table. The tabletop will move through a gantry (a circle, shaped like a big doughnut) that has an X-ray tube on one side and an arc-shaped detector mounted on the opposite side.
• During each full rotation, a fan-shaped X-ray beam is passed through your body and an image of a very thin section is acquired. The detector records about 1,000 images—or slices—of the expanded X-ray beam per rotation.
• A computer reconstructs the slices into two-dimensional (cross-sectional) and/or three-dimensional images of your internal anatomy. Most often, an entire scan can be done with a single breath hold.
• Some CT studies require an IV contrast material to enhance the visibility of certain tissues or blood vessels. The contrast is injected through an IV in your hand or arm. You may feel a warm, flushed sensation and experience a metallic taste in your mouth that lasts for a few minutes.
• Depending on the type of exam, your CT scan can take between 10-30 minutes.  

After Your CT Scan

When the scan is finished, the CT technologist will process the image data and will transfer the images digitally to a workstation where a board-certified radiologist (physician) interprets the scan. They will send a written report directly to your referring physician. Typically, your physician will have this report within hours of the exam's completion.

• You may leave as soon as the exam is completed and resume normal activities.
• Your normal diet may be resumed.
• If you were given a contrast agent orally or by IV, drinking plenty of water after the exam will help flush your system.
• Your imaging study will be interpreted by a board-certified radiologist who specializes in the area of the body being scanned.
• Your referring physician will receive a report and pictures detailing the findings of your exam within 24-48 hours. Plan to contact your doctor to discuss the results and any follow-up necessary.

Abdomen/Pelvis CT

Evaluates the liver, spleen, pancreas, kidneys and lower GI tract, including the colon and rectum.

Exam preparation:

• Continue to take your routine medications.
• You will be asked to drink one 500ml bottle of oral contrast 30-90 minutes prior to your exam while sitting in our department.

If you are diabetic or have renal insufficiency and will be receiving IV contrast as part of your CT exam, we will take blood and run a Creatinine level if no recent lab results are available within 30 days of your exam date.

• Please notify the technologist if you have had a barium study within the last three days.
• Please notify the technologist if you are pregnant or could be pregnant.
• Allow 15-30 minutes for the exam.
• Consult the CT Exam Guidelines below for more information.  

Angiogram CT

Evaluates arteries inside the body, excluding heart vessels.

Exam preparation:

• Continue to take your routine medications.
• No food for three hours prior to your exam.

If you are diabetic or have renal insufficiency and will be receiving IV contrast as part of your CT, we will run a Creatinine if no recent lab results are available within 30 days of your exam.

• Please notify the technologist if you have had a barium exam within the last three days.
• Please notify the technologist if you are pregnant or could be pregnant.
• Allow 15-30 minutes for the exam.
• Consult the CT Exam Guidelines below for more information.  

Brain CT

Assesses head injuries, stroke, brain tumors and other brain diseases.

Exam preparation:

• Continue to take your routine medications.
• No food for four hours prior to your exam if receiving IV contrast.
• Please notify the technologist if you are pregnant or could be pregnant.
• Allow 10-15 minutes for the exam.
• Consult the CT Exam Guidelines below for more information.

Chest CT

Assesses for lung cancer and other lung diseases.

Exam preparation:

• Continue to take your routine medications.
• No food four hours prior to your exam if receiving IV contrast.
• If you are diabetic or have renal insufficiency and will be receiving IV contrast as part of your CT exam, you must have a creatinine drawn if no recent lab results are available within 30 days of your exam.
• Please notify the technologist if you are pregnant or could be pregnant.
• Allow 15-30 minutes for the exam.
• Consult the CT Exam Guidelines below for more information.

Colonography CT

Evaluates entire colon for polyps and early signs of cancer. A virtual colonography requires no sedation, is minimally invasive, more comfortable, safer and faster than a traditional colonoscopy.

It is based on a CT scan of the abdomen and pelvis while the colon has been gently inflated with CO2 from a small enema tip inserted into the rectum.

Exam preparation:

• A 24-hour bowel cleansing prep is required, just as in a conventional optical colonoscopy. This includes a liquid diet and the drinking of a bowel prep kit liquid.
• Follow the directions closely as bowel residue may interfere with polyp detection.
• Continue to take your routine medications.
• Please notify the technologist if you are pregnant or could be pregnant.
• Allow 30-60 minutes for the exam.
• Consult the CT Exam Guidelines below for more information.

Coronary Artery Calcium Score CT

Assesses the location and extent of calcified plaque in the coronary arteries. The findings are expressed as a calcium score that is an early-stage indicator of potential coronary artery disease and allows for interventional treatment and life-style modification. Subtle early warning signs of heart disease can be detected using CACS.

Exam preparation:

• Continue to take your routine medications.
• Avoid caffeine and other stimulants for 12 hours prior to the scan.
• Please notify the technologist if you are pregnant or could be pregnant.
• Allow 5 minutes for the exam.
• Consult the CT Exam Guidelines below for more information.

Coronary CT Angiography

• Coronary CT Angiography is the use of computed tomography angiography to assess the coronary arteries of the heart.  Provides high resolution images of blood vessels that supply the heart to look for blockages and/or structural abnormalities.
• Exam preparation
  • Continue to take your routine medications.  Your physician may prescribe additional medications. If so, please take as prescribed.
  • Avoid caffeine and other stimulants for 12-hours prior to the scan.
  • Nothing to eat 4-hours prior to the exam.
  • Please notify the technologist if you are pregnant or could be pregnant.
  • A nurse will prep you for your procedure by placing an IV and delivering any necessary medications. Your nurse will accompany you throughout the entirety of your procedure.

Low-Dose CT Lung Screening

Detects small lung nodules that may be the earliest sign of lung cancer in patients of high risk of developing the disease. This exam uses a very low radiation dose and no IV contrast. Overlake is proud to be one of the Designated Lung Cancer Screening Centers by the American College of Radiology and works with Overlake Clinics Pulmonary Medicine to ensure appropriate follow-up.

Exam preparation:

• Continue to take your routine medications.
• No preparation is necessary.
• Please notify the technologist if you are pregnant or could be pregnant.
• Allow 5-10 minutes for the exam.
• Consult the CT Exam Guidelines below for more information.

Sinus CT

Evaluates sinus and nasal structures and abnormalities.

Exam preparation:

• No appointment is necessary.
• Continue to take your routine medications.
• No preparation is necessary.
• Please notify the technologist if you are pregnant or could be pregnant.
• Allow 5 minutes for the exam.
• Consult the CT Exam Guidelines below for more information.

Spine CT

Evaluates spinal column damage due to injury, detects tumors and fractures.

Preparation:

• Continue to take your routine medications.
• No preparation is necessary.
• Please notify the technologist if you are pregnant or could be pregnant.
• Allow 10-15 minutes for the exam.
• Consult the MDCT Exam Guidelines below for more information.