Fast medical imaging tests are critical for accurate stroke diagnosis and treatment. Armed with the results of computed tomographic (CT) scans, radiologists support medical response teams to help determine whether a patient has suffered a stroke or has another condition mimicking the symptoms.
Radiologists can also detect whether the patient has significant brain bleeding and other issues affecting treatment options, explained Edward C. Hwang, MD, MBA, a board-certified, fellowship-trained neuroradiologist with Radiologic Associates of Fredericksburg (RAF). Dr. Hwang is one of the RAF radiologists who works closely with the stroke team at Mary Washington Hospital.
Radiologists also use magnetic resonance imaging (MRI) tests to estimate the time that the stroke began if a patient awakened with symptoms – vital information that allows the medical team to provide the right treatments, when they are needed.
For example, a blood clot–busting enzyme called tissue plasminogen activator (tPA) can improve the chances of recovering from a stroke if administered within three to four and a half hours after the onset of symptoms, added Dr. Hwang.
“The use of radiology and expertise of our radiologists have allowed us to determine which stroke patients will benefit from the treatments we have available to us today,” said Arun Chhabra, MD, stroke director for Mary Washington Hospital.
The most common type of stroke, occurring in an estimated 87% of cases, is an ischemic stroke, which happens when an artery supplying blood to the brain becomes blocked, usually by a blood clot. The second type of stroke is a hemorrhagic stroke, when an artery in the brain leaks or bursts.
Mary Washington Hospital has been designated a Primary Stroke Center by the Joint Commission. When a patient arrives at the hospital with a suspected stroke – a “Code Neuro” – the medical team orders a non-contrast CT scan of the head, Dr. Hwang said. The scan combines X-ray and computer capabilities to produce cross-section images of the brain, which can reveal damage from a stroke or other conditions.
RAF physicians provide on-site radiology services to the hospital 24/7. In a suspected stroke case, the technologist performing the scan informs radiologists of the case so a radiologist can quickly evaluate test results and alert the stroke team of preliminary findings.
One of the quality metrics for a stroke center is the goal of obtaining a head CT interpretation in 45 minutes or less after a Code Neuro patient arrives at the emergency department, Dr. Hwang noted. In 2016, RAF achieved this goal 99.25% of the time, better than the national benchmark of 90%.
In one case reported by the hospital, a 43-year-old who was rushed by ambulance with a suspected stroke was administered tPA after the results of her CT scan came back. “Within thirty minutes, thanks to the rapid reactions of everyone involved and the Mary Washington Hospital Stroke Team, [she] went from not being able to move at all on her right side or to speak, to being able to move her hands, feet, and legs. She bears no side effects from the stroke,” according to the hospital’s report.
“Non-contrast head CT is the most widely used imaging study in patients with acute stroke due to its speed and availability. CT can show signs of early infarction, and CT can detect intracranial hemorrhage, which is a contraindication for tPA,” Dr. Hwang added. “The scan may also indicate stroke mimics, such as a brain tumor.”
Right after the head CT scan, a CT angiogram (CTA) test focusing on the blood vessels of the head and neck is often performed to evaluate for a blood clot. During a CTA, contrast is injected intravenously into the patient to highlight the blood vessels. The radiologist interprets the results and alerts the stroke team to findings, including any that suggest that the patient might benefit from procedures such as clot retrieval surgery.
A different medical imaging test comes into play when patients awaken with symptoms or are unsure when their stroke began: an MRI evaluating for diffusion-weighted imaging – fluid-attenuated inversion-recovery mismatch, or DWI-FLAIR mismatch for short. MRIs use a magnetic field and radio waves to create detailed images of the organs and tissues.
“The importance of radiology in stroke response is particularly evident if the patient was sleeping when symptoms started or is unable to communicate with us,” noted Dr. Chhabra. “MRI enables us to estimate the time someone had their stroke, which is of utmost importance for tailoring treatments accordingly.”
With this MRI protocol, the DWI sequence of the test looks for shifts in water molecules in the brain that can occur after a stroke. he FLAIR sequence evaluates stroke damage (lesions). By comparing DWI and FLAIR results, radiologists can estimate the time frame when the stroke began, Dr. Hwang said. Research studies have shown that in cases where DWI shows the telltale water molecule shift but FLAIR does not reveal stroke damage, for example, the likelihood is strong that the stroke is less than four and a half hours old. Another test, an MRI angiogram (MRA), is also added in these cases to look for blood clots.
Other tests and treatments may also be needed, depending on the patient’s condition. For more information, visit the following resources.
Speed is Key in Stroke Recovery
If you or someone you know experiences these stroke symptoms, immediately call 911 for emergency medical help. Fast treatment can improve the chances of survival and reduce long-term disabilities.
Source: American Stroke Association