Overview 

Computed Tomography (CT)

CT scan, is a commonly used noninvasive test that helps physicians diagnose a large number of medical conditions.

CT stands for Computerized Tomography, which is a process using multiple X-ray detectors to create images in multiple planes of the patient's organs, bones, blood vessels and soft tissues. The CT scanner itself is a large doughnut-shaped machine with X-ray detectors contained in a central ring. During the scan, you will lie on a table which slides in and out of this ring. All of Overlake's CT scanners are state-of-the-art multi-detector scanners.

All CT scans at Overlake are performed by a CT technologist who is licensed in the state of Washington and holds an advanced certification in CT. All of Overlake's technologists practice low dose techniques to keep the radiation exposure to the patient as low as possible. Sometimes contrast is injected through an intravenous line (IV) during the scan. In addition, you may also need to drink oral contrast prior to the CT scan, which is given to you at the time of your arrival.

At Overlake, one of our primary goals is to keep your radiation exposure as low as possible during your exam while maintaining diagnostic quality.  Different exams have different amounts of radiation involved, but as a reference, an individual is exposed to approximately 100 milligray of background radiation a year from sources like ultraviolet rays of the sun and small traces of radioactive isotopes in the soil.

For additional information regarding radiology procedures, please visit radiologyinfo.org.

When the scan is finished, the CT technologist processes the data and sends images digitally to a workstation where a board certified radiologist physician interprets the scan and sends a written report to your physician. Typically, your physician will have this report within hours of the exam's completion.

Abdomen/Pelvis CT

Abdomen/Pelvis CT

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

Preparation:

  • Continue to take your routine medications.
  • You will be asked to drink one 900 ml bottle of water mixed with contrast 3 hours prior to your exam while sitting in our department.
  • If you are over the age of 60 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 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 MDCT Exam Guidelines below for more information.  

Angiogram MDCT

Angiogram MDCT

Evaluates arteries inside the body, excluding heart vessels.

Preparation:

  • Continue to take your routine medications.
  • Take nothing by mouth 3 hours prior to your exam.
  • If you are over the age of 60 or have renal insufficiency and will be receiving IV contrast as part of your MDCT 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 have had a barium exam within the last 3 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 MDCT

Brain MDCT

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

Preparation:

  • Continue to take your routine medications.
  • Take nothing by mouth 2 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

Chest CT

Assesses for lung cancer and other lung diseases.

Preparation:

  • Continue to take your routine medications.
  • Take nothing by mouth 2 hours prior to your exam if receiving IV contrast.
  • If you are over the age of 60 or have renal insufficiency and will be receiving IV contrast as part of your CT exam, you must have a BUN/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

Colonography CT (also known as Virtual Colonoscopy)

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.

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. (You may pick up the kit at the Overlake Walgreens pharmacy, located in the Overlake Medical Tower. 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, or if you are breastfeeding.
  • Allow 30 minutes for the exam.
  • Consult the CT Exam Guidelines below for more information.

Coronary Artery CT

Coronary Artery CT (also known as Coronary Artery Calcium Scoring or CACS)

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.

Prepration:

  • 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 15 minutes for the exam.
  • Consult the CT Exam Guidelines below for more information.

Low-dose Lung Screening CT

Low-dose Lung Screening CT

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 intravenous contrast. Overlake is proud to be one of the Designated  Lung Cancer Screening Centers by the American College of Radiology and works with Overlake Medical Clinics Pulmonary Medicine to ensure appropriate follow up.

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

Sinus CT

Evaluates sinus and nasal structures and abnormalities.

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

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.

CT Exam Guidelines: Preparation

CT Exam Guidelines: Preparation 

    • Prior to your scheduled appointment, Overlake Medical Imaging will call you to discuss specific instructions, review your health and insurance information and answer any questions.
    • Follow the specific preparation instructions listed for your particular 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 must be removed prior to the exam.
    • Wear comfortable clothing without zippers, snaps or metal buttons. Or, you may 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-rays, etc.) with you on the day of your exam.
    • Normally we would like you to arrive 15 minutes prior to your exam, but this may be changed if you are required to drink contrast.

    CT Exam Guidelines: During Exam

    CT Exam Guidelines: During Exam

      • The technologist will help position you comfortably on a cushioned table. The table top will move through a gantry (shaped like a big donut) 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 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. Normally 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.  

      CT Exam Guidelines: After Exam

      CT Exam Guidelines: After Exam 

      • 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 hours. You should contact your doctor to discuss the results.
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