This 62 year-old male patient arrived at the emergency department with symptoms of an acute left middle cerebral artery (MCA) stroke, or "brain attack." Initial imaging workup consisted of a non-contrast CT scan of the brain on the Brilliance CT 16-slice system, followed immediately by a CT brain perfusion study (CTP) and a CT angiogram (CTA) of the neck and brain according to the institutions Brain Attack protocol.
Perfusion scan parameters
- 8 x 3 mm
- 0.75 second
- 90 kV
- 100 mAs/slice
- 2 mm thickness
- 5 cc/second for a total of 40 cc's
CTA scan parameters
- 16 x 0.75 mm
- 0.5 second
- 120 kV
- 275 mAs/slice
- 1 mm thickness
- 0.5 mm increment
- 19.1 second scan time
- 324 mm scan length
- 4 cc/second for a total of 90 cc's
The initial non-contrast images of the brain demonstrate no evidence of acute intracranial hemorrhage, mass effect or midline shift. There is a vague area of hypodensity in the left basal ganglia, suspicious for underlying ischemia.
CTP reveals a small area of infarction in the left basal ganglia and corona radiate, with a large surrounding penumbra of reversible ischemia. Circle of Willis and cervicocerbral CTA was acquired, demonstrating 95% stenosis of the left internal carotid artery (ICA) just distal to the common carotid bifurcation. An intraluminal filling defect representing thrombus was identified in the proximal aspect of the left MCA.
After stenting the left ICA, thrombectomy of the left MCA was attempted using a Merci Retriever device (Concentric Medical, Mountain View, CA). Although two passes with the Retriever device resulted in extraction of only a very small amount of thromboembolic material, flow into the posterior cerebral, anterior choroidal and anterior cerebral arteries were noticeably improved.
Cerebral infarction affects more than 750,000 each year in the U.S., with an annual estimated cost of 45 billion dollars. Early aggressive imaging has become crucial in the management of these patients. Intracranial hemorrhage or nonvascular causes of stroke symptoms need to be ruled out for intravenous or intraarterial thrombolytic therapy with tissue plasminogen activator (t-PA) to be considered within 3-6 hours of the onset of symptoms, respectively. As the use of intravenous t-PA to treat ischemic cerebral infarction is associated with a 10-fold increased risk of intracranial hemorrhage, determining which patients are most likely to benefit from thrombolytic therapy is of the utmost importance. Perfusion imaging provides the information needed to analyze the characteristics of blood flow to the brain, demonstrating areas of reduced cerebral parenchymal perfusion, or "ischemic penumbra." This area of the brain is considered viable but at risk for infarction if blood flow is not rapidly improved. CTP provides the information needed to differentiate the ischemic penumbra from areas of completed infarction. Patients with considerable ischemic penumbra relative to infarction are the ones most likely to benefit from thombolytic therapy.
The Philips Brilliance CT 16-slice system using 16 x 0.75 mm collimation obtained the high resolution dataset needed for exquisite Volume Rendered and MPR analysis. Using the two-click vessel isolation tool, the left carotid easily isolated and displayed in the stent planning package. The measurements obtained provided the sizing information that was helpful for proper stent selection and placement.
The user friendly Brain Perfusion Package not only provides crucial information concerning the infarct and area of penumbra, but also automatically supplies other important parameters. Time to Peak (TTP), Mean Transit Time (MTT), Cerebral Blood Volume (CBV), and Cerebral Blood Flow (CBF) are measured and displayed, helping to better characterize an evolving ischemic event.
The information obtained using the Philips Brilliance 16-slice system and the Philips Brilliance Workspace was crucial in this patient's management. A follow-up CT scan of the brain performed two days later demonstrated no extension of the original infarcted territory, suggesting that the surrounding ischemic penumbra had been salvaged.