What is a CT scan? How do CT scans work? When are CT scans ordered with contrast? How do you prepare for a CT scan? Get all the answers to your questions about this important diagnostic imaging procedure.

What is a Computed Tomography (CT) Scan?

A Computed Tomography (CT) scan, also known as a CT scan or CAT scan, is a diagnostic imaging procedure that uses X-ray technology and computer software to create detailed, cross-sectional images of the inside of the body. These images can show the structure and details of various organs, tissues, and body systems, including the bones, muscles, fat, organs, and blood vessels.

Unlike standard X-rays, which provide a single, two-dimensional image, CT scans use a series of X-ray beams that move in a circular pattern around the body, capturing multiple views. The X-ray data is then processed by a computer and displayed as a two-dimensional image on a monitor, or can be used to create three-dimensional images.

How Do CT Scans Work?

During a CT scan, the patient lies on a table that slides into the circular opening of the CT scanner. The scanner rotates around the patient, taking multiple X-ray images from different angles. These images are then processed by a computer, which assembles them into detailed, cross-sectional images of the body.

The CT scanner uses a narrow X-ray beam that moves in a circular pattern around the patient. As the X-ray beam passes through the body, it is attenuated (reduced in intensity) by the tissues it encounters. The degree of attenuation depends on the density of the tissue, with denser tissues like bone attenuating the X-ray beam more than less dense tissues like fat or muscle.

The X-ray data is collected by detectors in the scanner and sent to a computer, which processes the information and creates detailed, two-dimensional images of the scanned area. These images can be further manipulated and viewed from different angles to provide a comprehensive picture of the patient’s internal structures.

When Are CT Scans Ordered with Contrast?

CT scans can be performed with or without the use of a contrast agent, depending on the specific diagnostic needs. Contrast agents are substances that are taken orally or injected intravenously (into a vein) to enhance the visibility of certain organs or structures on the CT images.

Contrast agents can help the radiologist better identify abnormalities, such as tumors, internal bleeding, or other issues. They can also improve the visualization of blood vessels, organs, and other structures that might not be as easily seen without the contrast.

Patients may be required to fast for a certain period of time before a CT scan with contrast, and they should inform their doctor if they have any allergies or kidney problems, as these can impact the use of contrast agents.

How Do You Prepare for a CT Scan?

Preparing for a CT scan can vary depending on the specific type of scan and whether contrast is being used. In general, patients may be instructed to:

• Change into a patient gown and remove any jewelry or piercings
• Inform the healthcare team of any allergies, medical conditions, or recent illnesses
• Fast for a certain period of time before the scan, if contrast is being used
• Drink a contrast agent before the scan, if a double-contrast study is being performed
• Refrain from taking certain medications, if instructed to do so

Patients who are pregnant or think they may be pregnant should inform their doctor before scheduling a CT scan, as the procedure involves the use of ionizing radiation.

What Can CT Scans Be Used For?

CT scans are a versatile diagnostic tool that can be used to examine a wide range of body parts and systems. Some of the common uses of CT scans include:

1. Diagnosing and monitoring tumors or other abnormalities in the body
2. Investigating internal bleeding or other injuries, particularly in the case of trauma
3. Guiding biopsies or other medical procedures, such as the placement of catheters or stents
4. Evaluating the chest, abdomen, and pelvis for a variety of conditions, including cancer, infection, and organ damage
5. Assessing the brain and spinal cord for conditions like stroke, head injury, or spinal cord compression
6. Analyzing bone structures and joints for fractures, arthritis, or other musculoskeletal problems
7. Monitoring the progression of chronic conditions or the effectiveness of treatment

What are the Advantages of CT Scans?

CT scans offer several advantages over other imaging techniques, such as standard X-rays or magnetic resonance imaging (MRI) scans. These advantages include:

• Faster scan times, often just a few minutes
• Ability to visualize a wider range of tissues and structures, including bone, muscle, and organs
• Higher resolution and more detailed images, particularly of the soft tissues and internal organs
• Ability to create three-dimensional images and models of the body’s structures
• Accessibility and availability in many healthcare settings

While CT scans do involve the use of ionizing radiation, the benefits of the procedure often outweigh the risks, particularly when used judiciously and with appropriate safety precautions.