Abstract:
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Purpose: The goal of this study is to determine using CT Perfusion the critical thresholds of cerebral blood flow and blood volume causing infarction in an embolic model of cerebral ischemia.
Methods and Materials: Five New Zealand White rabbits underwent surgical preparation for the introduction of an autologous blood clot by transection of the external carotid and insertion of a catheter into the internal carotid artery (ICA). All CT scans were performed with a General Electric Medical Systems (GEMS) LightSpeed Plus CT scanner and consisted of a continuous scan for 25.5 seconds with a bolus injection of 4mL of iodinated contrast agent (Omnipaque 300) at a rate of 1 mL/s at the start of the scan. Following the baseline scan, a 10 mm long embolus (aged 2 hr in thrombin) was delivered in a 3 mL bolus of saline to the middle cerebral artery via the catheter previously placed in the ICA. Further CT scans were performed at 10 min, 30 min and then every 30 min up to 3 hr after the embolus was delivered, including an additional scan at 4 hr post. Cerebral blood flow (CBF) and blood volume (CBV) were determined with CT Perfusion (GEMS) at each of the time points. The animals were sacrificed immediately following the 4 hr scan. The brain was removed, sliced at 5mm intervals corresponding to the position of the four CT slices, and incubated at 38°C in 2% 2,3,5-triphenyltetrazolium chloride (TTC) to identify the infarcted region.
Results: A total of 11 regions of interest were drawn on CBF and CBV maps created using CT Perfusion (GEMS) corresponding to the locations on the tissue slices where TTC staining was absent. For all these regions: (i) CBF was 7.3±1.4 ml/min/100g and did not exceed 10 ml/min/100g; and (ii) CBV was 0.52±0.17 ml/100g and was always less than 1.0 ml/100g of tissue at 4 hr post embolization. In the penumbral region surrounding the infarct, CBV and CBF did not simultaneously fall below the respective thresholds mentioned above.
Conclusion: All regions identified with TTC staining had CBF less than 10ml/min/100g and CBV less than 1ml/100g tissue at 4 hr post embolization indicating that these values identify regions of tissue that are no longer viable.
(T. L. : General Electric Medical Systems, Consultant (Self), Grant (Self))
Questions about this event email: tlee@imaging.robarts.ca
Murphy, B,
Blood Flow and Volume Threshold for Infarction in an Embolic Model of Cerebral Ischemia. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3103865.html
