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Neuro Volume Perfusion CT

as a Reliable Tool for Analysis of Ischemic Stroke within Posterior Circulation

Author: Philipp Gölitz, MD Department of Neuroradiology, University of Erlangen-Nuremberg, Erlangen, Germany

History
A 90-year old male patient was brought to our hospital with a right-sided hemiparesis and aphasia existing for two and a half hours. Physical examination showed an NIHSS (National Institute of Health stroke score) of 18. No history of neurological disorders or absolute arrhythmia was known. From the clinical appearance it was suspected that the symptoms could be caused by an infarction within the left middle cerebral artery territory.
 

Diagnosis
The neuroradiologic examination started with a cranial, non-enhanced CT (NECT) scan for ruling out intracranial hemorrhage or tumor. A short segment of the proximal part of the left posterior cerebral artery (P1-segment of PCA) was found to be hyperdense as a sign of thrombembolic occlusion. The grey and white matter distinction was not altered. Next a volume perfusion CT (VPCT) was performed. It revealed a delayed time to peak (TTP) of the whole left PCA-territory including the thalamus and the left cerebral peduncle. Also the mean transit time (MTT) was prolongated. On the other hand there was no definable reduction of the cerebral blood volume (CBV) and the cerebral blood flow within the PCA-territory. Additionally, measurement of the permeability was performed, which was slightly increased only in a few cortical parts. This could be interpreted as a predictor of a reduced risk of developing a hemorrhagic stroke transformation. In correlation to the early stroke sign of the NECT the CT-angiography (CTA) detected the P1-segement occlusion on the left side. The P2- and P3-segment of the PCA were regularly contrasted, presumably via the (also in the CTA visible) left posterior communicating branch from the anterior circulation. The parameter constellation of the VPCT indicated a large penumbra volume and so it was decided to start an intravenous lysis therapy. The therapy was successful and the patient recovered remarkably. The follow-up NECT on next day showed no delineation of any infarction.
 

Comments
This case illustrates, that VPCT allows a reliable analysis concerning ischemic stroke changes also within the posterior circulation territory including thalamus and midbrain. Moreover, the VPCT can be used as a quick, feasible tool for the assessment of the tissue at risk and thereby the patient management could be influenced.
 

Fig 1: Delayed Time to peak (TTP) and prolonged MTT show a delay of blood flow in the whole left PCA-territory including the thalamus and the left cerebral peduncle whereas CBV and CBF were unchanged.
Fig 2: CT-angiography (CTA) detected the P1-segement occlusion (arrow) on the left side
Fig 3: Fusion of CTA and TTP delay indicate the occlusion (arrow) and the corresponding perfusion delay in the PCA-territory (arrowhead).

Examination Protocol

Scanner SOMATOM Definition AS+
Scan mode Adaptive 4D Spiral
Scan area Head
Scan length 96 mm
Scan direction Caudo-cranial
and cranio-caudal
Scan time 46 s
Tube voltage 80 KV
Tube current 200 mAs
CTDIvol 218 mGy
Rotation time 0.3 s
Slice collimation 128 x 0.6 mm
Slice width 3 mm
Spatial Resolution 0.33 mm
Reconstruction increment 1 mm
Reconstruction kernel H20f
Contrast  
Volume 30 ml
Flow rate 5 ml/s

Date: Sep 08, 2011


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