Acute Ischemic Stroke – Cerebral Perfusion prior to and after Treatment

Jie Zhu, MD, Prof. Bei Zhang, MD, Xi Zhao*, MD
Department of Radiology, Minhang Central Hospital, Shanghai, P. R. China
*Siemens Healthineers, P. R. China
 |  07-10-2019

History

A 74-year-old female patient, having had a sudden onset of unconsciousness 5 hours ago, was presented to the emergency department. The patient had a history of uncontrolled hypertension and cerebral ischemic stroke. An ECG revealed a paroxysmal atrial fibrillation. A non-contrast CT showed a slightly hypodense area in the right frontal and parietal lobes, suggesting an ischemic change. Volume perfusion CT was requested to further investigate the cause of the ischemia and the viability of the ischemic cerebrum.

Diagnosis

Non-contrast CT images showed a slightly hypodense area in the territory of the right middle cerebral artery (RMCA), with disappearance of the local sulci and the lateral sulcus, suggesting an ischemic stroke. Volume perfusion CT images showed a mismatch between the extent of reduced cerebral blood flow (CBF) and cerebral blood volume (CBV) suggesting the existence of a penumbra. Time to drain (TTD) and mean transit time (MTT) were increased, indicating delayed blood supply. CT angiography (CTA) images reconstructed from the thin slice perfusion data using syngo. CT Dynamic Angio (tMIP) showed an occlusion in the middle segment of the RMCA.
The patient was treated by intravenous thrombolysis. A follow-up Perfusion CT, performed 8 days later, showed a recanalized RMCA and significantly restored perfusion in the corresponding territory. The patient recovered with left-sided weakened muscle strength of 5, at discharge.

Fig. 1:
Non-contrast CT image (Fig. 1a) shows a slight hypodense area in the territory of the RMCA, with disappearance of the local sulci and the lateral sulcus, suggesting an ischemic stroke. CBF (Fig. 1b) and CBV (Fig. 1c) images show a mismatch suggesting an existence of a penumbra. TTD (Fig. 1e) and MTT (Fig. 1f) are increased indicating a delayed blood supply. CTA image (Fig. 1d) shows an occlusion of the RMCA.

Fig. 2:
A follow-up Perfusion CT (8 days) shows a recanalized RMCA and significantly restored perfusion in the corresponding territory.

Comments

Acute ischemic stroke is a leading cause of adult disability worldwide. A non-contrast CT is usually performed to exclude intracranial hemorrhage and to check for early signs of ischemia. This is however not sensitive enough for the detection of still viable tissue at risk. Volume Perfusion CT, using the Adaptive 4D spiral mode after a single bolus of contrast, is performed to acquire images tracking the temporal course of iodinated contrast material passing through the cerebral circulation. Perfusion parameters, such as cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), etc. are calculated from the voxel time-attenuation curves. The results may help physicians identify and differentiate still salvageable tissue at risk from tissue that is already infarcted and at risk of hemorrhage with reperfusion. This is important for the patient’s treatment planning and follow-up. In this case, despite the fact that the hypodense area shown on the non-contrast CT was relatively large and the time since symptom onset was already 5 hours, intravenous thrombolysis treatment was performed, since the CT perfusion images showed a small core and a large penumbra. Follow-up imaging and the clinical course both indicate that this diagnosis was correct, and that the patient benefited from the treatment.

Examination Protocol

ScannerSOMATOM AS+ 
Scan areaHeadHead
Scan modeSequentialAdaptive 4D Spiral
Scan length136.8 mm96 mm
Scan directionCaudal-cranialShuttle
Scan time12 s36 s
Tube voltage120 kV70 kV
mAs per image294 mAs100 mAs
Dose modulationCARE Dose4DNA
CTDIvol41.82 mGy57.7 mGy
DLP602 mGy cm657 mGy cm
Rotation time1.0 s0.3 s
Slice collimation60 x 0.6 mm32 x 1.2 mm
Slice width7.2 mm1.5 mm
Reconstruction increment7.2 mm1.0 mm
Reconstruction kernelH40sH10f
Contrast 370 mg / mL
VolumeNA40 mL + 40 mL Saline
Flow rateNA6 ml/s
Start delayNA5 s