Computed tomography (CT) scans are a common medical imaging tool that effectively detects blood clots throughout the body. These scans use specialized X-ray technology and computer processing to create detailed cross-sectional images of internal structures, including blood vessels, making them valuable for diagnosing obstructions.
How CT Scans Visualize Blood Clots
A CT scan operates by using a rotating X-ray source and multiple detectors to capture images from various angles around the body. These X-ray beams pass through the body, and different tissues absorb the radiation to varying degrees. The detectors measure the attenuated X-rays, and a computer then processes this information to construct detailed cross-sectional “slices” of the body. These images can then be stacked to create a three-dimensional view.
To visualize blood clots, a contrast material is administered. This contrast agent travels through the bloodstream, making blood vessels appear bright on the CT images. A blood clot, being a blockage, prevents the contrast material from flowing freely into that area. This creates a “filling defect,” where the clot appears as a darker area against the bright, contrast-filled vessel.
Computed Tomography Angiography (CTA) focuses on arteries, while Computed Tomography Venography (CTV) targets veins. These specialized techniques enhance the visibility of blood vessels and any clots they may contain.
Key Areas Where CT Scans Detect Clots
CT scans detect blood clots in several areas of the body.
In the lungs, Computed Tomography Pulmonary Angiography (CTPA) is a primary method for identifying pulmonary embolisms (PEs), which are blood clots that have traveled to the lungs. This specialized CT scan visualizes the pulmonary arteries, and a clot appears as a filling defect within these vessels. PEs can be life-threatening, making rapid and accurate detection by CTPA important.
For blood clots in the legs and pelvis, known as deep vein thrombosis (DVT), CT venography (CTV) is employed. While ultrasound is often a first-line test, CTV offers advantages for visualizing clots in larger veins, including those in the pelvis and abdomen, especially when ultrasound results are inconclusive.
CT scans also diagnose blood clots in the brain, which can cause ischemic strokes. While a non-contrast CT scan is often the initial imaging to rule out bleeding, a CTA of the head and neck can then identify large vessel occlusions due to blood clots. This helps pinpoint the location of the blockage to guide appropriate treatment.
Beyond these common locations, CT scans can identify clots in other major vessels throughout the body. For instance, CT angiography with contrast can reveal clots in vessels supplying the intestines, a condition known as mesenteric ischemia. Similarly, clots in the renal veins, which can affect kidney function, can also be detected using CT venography.
Understanding Your CT Scan Results
After a CT scan, a radiologist, a physician specializing in medical imaging interpretation, reviews the images. The radiologist analyzes any filling defects or other abnormalities that might indicate a blood clot. This interpretation is then compiled into a report, which is sent to the doctor who ordered the scan.
A “positive” result indicates that a blood clot was identified on the scan. This finding then guides the referring physician in determining the next steps, which may involve prescribing medication to dissolve the clot or prevent its growth, or considering other interventions. Conversely, a “negative” result suggests that no blood clot was detected in the imaged area.
While CT scans are accurate for detecting blood clots, no medical test offers absolute certainty. The clinical context, including a patient’s symptoms and medical history, is always considered alongside imaging results. The patient’s doctor will discuss the CT findings, explain their implications, and outline the appropriate course of action based on the complete clinical picture.