Diagnosing Stroke: Imaging Essential for Good Outcomes
By Debra Wood, RN, contributor
As stroke outcomes have become increasingly reliant on fast, accurate diagnoses and treatment, CT techs and MRI techs have an increasingly important role in ensuring the scans are promptly initiated and carried out.
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Speed of CT scans is of the essence
The American Heart Association (AHA)/American College of Cardiology (ACC) guidelines call for a non-contrast head CT scan within 25 minutes of the patient presenting to the emergency department with stroke symptoms, and the scan should be interpreted within 45 minutes.
The CT scan is used when diagnosing stroke to determine if the patient has had an intracranial hemorrhage. The guidelines indicate that “timely brain imaging and interpretation remains critical to the rapid evaluation and diagnosis of patients with potential ischemic strokes.”
Imaging of acute stroke must take place to rule out contraindications to fibrinolysis, such as hemorrhage or widespread hypoattenuation, before the administration of IV recombinant tissue-type plasminogen activator (rtPA) alteplase, which increases the chances of a complete or nearly complete neurological recovery.
A CT scan also will identify other causes of neurological symptoms, including a brain tumor.
“CT is still the immediate imaging modality for patients with symptoms that are suspect for a stroke,” said Joy A. Cook, MS, RT (R)(CT)(MR) ARRT, clinical associate professor and clinical coordinator in the Radiologic and Imaging Sciences Program at the University of Southern Indiana in Evansville and a member of the American Society of Radiologic Technologists.
“CT is also the best choice as it is more important for patient management to know if there is blood present or if other causes of the symptoms exist, which CT can demonstrate,” Cook added.
MRIs also used in diagnosing stroke
Stroke imaging by MRI also may be used for diagnosing stroke and ruling out an intracranial hemorrhage, according to the AHA/ACC guidelines.
“MRI examinations of the brain using a neurovascular or multichannel head coil with diffusion-weighted imaging (DWI) is the most commonly used for diagnosis of acute stroke,” Cook said.
“In an acute stroke, the water molecules present due to the edema that occurs move slower than water molecules present in normal tissue. This makes the area of stroke appear as areas of bright signal on DWI sequences.”
However, CT is more available for stroke imaging in an emergency, Cook added. MRI also is more expensive than CT.
“As CT is the imaging modality of choice, some departments will follow up with a complete MRI brain, including T1, T2, flair, and diffusion weighting imaging in various planes,” Cook said.
“Some departments may have shorter or quick imaging protocols to solely look for or identify the stroke: Axial diffusion weighted imaging, Axial T2 or Axial Flair. Some imaging departments include a contrast portion for a perfusion sequence. Perfusion imaging is done to evaluate for tissue viability,” she added.
Other tests and imaging following initial CTs or MRIs
Depending on the results of the CT or MRI, a noninvasive intracranial vascular study is strongly recommended by the guidelines, but it should not delay treatment with IV rtPA.
During the initial emergency evaluation, the guidelines recommend a limited number of coagulation, hematologic and biochemistry tests, but only blood glucose must be completed before starting IV rtPA.
An electrocardiogram (EKG or ECG) and troponin assessment should be done, but again, it should not delay the start of IV rtPA.
As for patients whose symptoms resolve, the AHA/ACC guidelines recommend noninvasive imaging of the cervical vessels, by intracranial CT or MR angiography, and neuroimaging within 24 hours of symptom onset. MRI is preferred.
Cook added that carotid ultrasounds and echocardiograms also are helpful.
“If patients with this pathology can be identified earlier, then their conditions can be watched and managed to help in prevention,” she said.
Demand for CT tech and MRI tech jobs
All of these imaging tests require technicians and radiologists. CT tech jobs and MRI tech jobs remain in demand, not only for imaging of acute stroke. The Bureau of Labor Statistics estimates radiologic and MRI technologist jobs will increase 9 percent by 2024.
CT tech jobs and other radiologic tech jobs paid an average of $57,450 annually in 2016 and MRI tech jobs $68,420, according to the BLS. Salaries for traveling image techs will vary by location and contract.