Not for emergencies. Call 911 or go to the nearest ER immediately for chest pain, severe shortness of breath, stroke symptoms, major trauma, or any urgent symptom. DOD is not an emergency service.
CT Scan Education Guide
Computed tomography (CT) is a medical imaging technology that uses X-rays taken from multiple angles to create detailed cross-sectional images of internal body structures. CT is widely used for rapid evaluation of many body regions and is generally faster than MRI.
Educational content only. This page is for patient education and does not constitute medical advice. Clinical appropriateness is determined by a licensed provider. DOD does not perform or interpret CT scans.
Quick Answer
A CT scan uses X-rays taken from many angles around the body, which a computer combines to create cross-sectional "slices" and 3D reconstructions of internal structures. CT scans involve ionizing radiation and may use intravenous iodinated contrast agents to highlight blood vessels and certain tissues. A provider order is required at most imaging facilities before a CT scan can be scheduled. DOD can review CT order requests for eligible patients in supported states, but DOD does not perform CT scans or interpret results.
How CT Works
A CT scanner contains an X-ray tube and detectors arranged in a ring (gantry). As the patient moves through the scanner, the X-ray tube rotates rapidly around the body, capturing images from hundreds of different angles simultaneously. A computer processes these data points using reconstruction algorithms to generate cross-sectional images and three-dimensional views of internal anatomy.
CT scans are significantly faster than MRI — many studies are completed in seconds to minutes. This speed makes CT particularly valuable in situations where rapid evaluation is needed. According to RadiologyInfo.org, CT is commonly used for evaluation of the chest, abdomen, pelvis, head, and musculoskeletal structures.
Unlike MRI, CT uses ionizing radiation. Radiation exposure from CT varies by body part and protocol. According to the FDA, CT dose management is an active area of medical imaging safety. Facilities use dose optimization techniques to minimize radiation while maintaining diagnostic quality.
What CT May Be Used to Evaluate
A licensed provider determines whether CT is appropriate for any patient. Depending on symptoms, history, and clinical context, a provider may consider CT for evaluation of:
Head / Brain
Head trauma, acute stroke evaluation (with CTA), sinuses, skull base
Chest
Lung parenchyma, mediastinum, pleura, pulmonary vasculature (CTA-PE), cardiac structures
Abdomen & Pelvis
Solid organs, bowel, appendix, lymph nodes, retroperitoneum, kidneys, urinary tract
Spine
Vertebral fractures, spinal canal, bone density — often after trauma or when MRI is contraindicated
Extremities
Complex fractures, joints, subtle bone pathology
Vascular (CTA)
Aorta, pulmonary arteries, coronary arteries, peripheral vessels
Educational only. Clinical appropriateness is determined by a licensed provider.
CT With and Without Contrast
CT studies may be ordered without contrast, with iodinated IV contrast, or in some cases as a multiphase study with and without contrast. Iodinated contrast agents enhance the visibility of blood vessels and certain tissues. The ordering provider specifies whether contrast is indicated based on the diagnostic question.
Patients with iodine allergies, kidney disease, diabetes, or who take metformin should inform the provider and the imaging facility before contrast CT. An eGFR kidney function test may be required. Patients should discuss contrast risks and alternatives with their ordering provider and the imaging facility.
CT With Contrast — What Patients Should KnowProvider Order Requirement
Most outpatient CT facilities require a valid provider order before scheduling. A CT order typically includes: the specific exam type, body part, contrast instructions, clinical indication, ordering provider name and NPI, and results destination. DOD can review CT order requests for eligible patients in supported states when medically appropriate.
Frequently Asked Questions — CT Scan
Sources and Further Reading
- CT Scan — Patient Information — RadiologyInfo.org (ACR / RSNA)
- CT Scans — Overview — MedlinePlus (U.S. National Library of Medicine / NIH)
- Computed Tomography (CT) — Radiation Dose — U.S. Food and Drug Administration (FDA)
- ACR Appropriateness Criteria — American College of Radiology (ACR)
Related Education and Order Pages
Need a Provider Review Before Scheduling a CT Scan?
$40 virtual provider review. Orders issued only when medically appropriate. Not for emergencies.
Start Virtual Consult — $40Not for emergencies. Orders not guaranteed.
Educational content only. DOD is not an imaging center, laboratory, radiology facility, or emergency service. DOD does not perform or interpret CT scans. All clinical decisions should be made by qualified licensed healthcare providers.