Stroke Imaging: Why Every Minute Counts

When a stroke happens, every minute counts. For each minute without treatment, the brain loses approximately 1.9 million neurons, according to the American Stroke Association. Imaging is the critical first step that determines what type of stroke is occurring and how to treat it.

What Is a Stroke?

A stroke occurs when blood flow to part of the brain is interrupted. There are two main types:

• Ischemic stroke (87% of cases) — A blood clot blocks an artery supplying the brain
• Hemorrhagic stroke (13% of cases) — A blood vessel bursts and bleeds into the brain

Treatment is completely different for each type. Imaging is the only way to tell them apart.

The Role of CT in Stroke

A non-contrast CT scan of the brain is usually the first imaging test performed when a stroke is suspected. It can be completed in seconds and is available in every emergency room.

What CT Shows in Stroke

• Hemorrhagic stroke — Blood appears bright white on CT, making bleeds immediately visible
• Ischemic stroke — Early ischemic changes may be subtle on CT, but the scan rules out bleeding so clot-busting medication can be given safely

CT Angiography (CTA)

If ischemic stroke is suspected, doctors often add CT angiography — a contrast-enhanced scan that maps the blood vessels in the neck and brain. CTA can:

• Identify the exact location of a blood clot
• Show which arteries are blocked
• Help determine if the patient is a candidate for mechanical thrombectomy (clot retrieval)

The Role of MRI in Stroke

While CT is faster, MRI provides more detailed information about brain tissue:

Diffusion-Weighted Imaging (DWI) This specialized MRI sequence can detect an ischemic stroke within minutes of onset — far earlier than standard CT. It shows exactly which brain tissue has been damaged and which is still at risk.

MRI Advantages in Stroke

• Detects very small strokes that CT may miss
• Shows how much brain tissue can still be saved (the ischemia penumbra)
• Identifies old strokes and other brain conditions
• No radiation exposure

When MRI Is Used

MRI is often performed after the initial CT, especially when:

• The CT scan is normal but stroke is still suspected
• Doctors need to determine the exact extent of damage
• Treatment decisions require more detailed information

Time Is Brain: The Treatment Window

The phrase "time is brain" captures the urgency of stroke treatment:

• tPA (clot-busting drug) must be given within 4.5 hours of symptom onset
• Mechanical thrombectomy can be performed up to 24 hours after onset in select patients (based on imaging)
• Every 15-minute delay in treatment reduces the chance of a good outcome

According to the National Institute of Neurological Disorders and Stroke, advanced imaging has expanded the treatment window for many patients by showing which brain tissue is still salvageable.

Recognizing Stroke Symptoms: BE FAST

If you or someone near you experiences these symptoms, call 911 immediately:

• B — Balance loss
• E — Eye vision changes
• F — Face drooping
• A — Arm weakness
• S — Speech difficulty
• T — Time to call 911

Do not drive yourself to the hospital. Emergency medical services can begin evaluation and alert the stroke team before you arrive.

Imaging After Treatment

After stroke treatment, follow-up imaging monitors recovery:

• CT at 24 hours — Checks for bleeding after clot-busting medication
• MRI at 3 to 7 days — Maps the final extent of brain damage
• Carotid ultrasound — Checks neck arteries for plaque that could cause future strokes
• Echocardiogram — Looks for heart conditions that may have caused the clot

Prevention and Screening

While emergency stroke imaging is performed at hospitals, ongoing monitoring and prevention often involve outpatient imaging. At AMI, we provide MRI, CT scans, ultrasound, and echocardiograms that support long-term stroke prevention.

Schedule Your Imaging

If your doctor has ordered brain imaging or vascular screening, call Advanced Medical Imaging at (727) 398-5999 or schedule online. Fast results help your care team make timely decisions.

Sources: - American Stroke Association - NINDS — Stroke Information - RadiologyInfo.org — Stroke Imaging