Irene Gulka

Identification of Penumbra and Infarct in Acute Ischemic Stroke Using Computed Tomography Perfusion–Derived Blood Flow and Blood Volume Measurements

Background and Purpose— We investigated whether computed tomography (CT) perfusion–derived cerebral blood flow (CBF) and cerebral blood volume (CBV) could be used to differentiate between penumbra and infarcted gray matter in a limited, exploratory sample of acute stroke patients. Methods— Thirty patients underwent a noncontrast CT (NCCT), CT angiography (CTA), and CT perfusion (CTP) scan within 7 hours of stroke onset, NCCT and CTA at 24 hours, and NCCT at 5 to 7 days. Twenty-five patients met the criteria for inclusion and were subsequently divided into 2 groups: those with recanalization at 24 hours (n=16) and those without (n=9). Penumbra was operationally defined as tissue with an admission CBF <25 mL · 100 g−1 · min−1 that was not infarcted on the 5- to 7-day NCCT. Logistic regression was applied to differentiate between infarct and penumbra data points. Results— For recanalized patients, CBF was significantly lower (P<0.05) for infarct (13.3±3.75 mL · 100 g−1 · min−1) than penumbra (25.0±3.82 mL · 100 g−1 · min−1). CBV in the penumbra (2.15±0.43 mL · 100 g−1) was significantly higher than contralateral (1.78±0.30 mL · 100 g−1) and infarcted tissue (1.12±0.37 mL · 100 g−1). Logistic regression using an interaction term (CBF×CBV) resulted in sensitivity, specificity, and accuracy of 97.0%, 97.2%, and 97.1%, respectively. The interaction term resulted in a significantly better (P<0.05) fit than CBF or CBV alone, suggesting that the CBV threshold for infarction varies with CBF. For patients without recanalization, CBF and CBV for infarcted regions were 15.1±5.67 mL · 100 g−1 · min−1 and 1.17±0.41 mL · 100 g−1, respectively. Conclusions— We have shown in a limited sample of patients that CBF and CBV obtained from CTP can be sensitive and specific for infarction and should be investigated further in a prospective trial to assess their utility for differentiating between infarct and penumbra.

White Matter Thresholds for Ischemic Penumbra and Infarct Core in Patients with Acute Stroke: CT Perfusion Study

PURPOSE To prospectively determine the parameters derived at admission computed tomographic (CT) perfusion imaging admission that best differentiate ischemic white matter that recovers from that which infarcts, with the latter retrospectively defined at a CT examination performed without contrast material (unenhanced CT) 5-7 days after the event. MATERIALS AND METHODS Ethics committee approval and informed consent were obtained. Thirty patients with stroke underwent unenhanced CT, CT angiography, and CT perfusion studies at admission. Additionally, CT angiography was performed 24 hours after the stroke, and an unenhanced CT study was performed 5-7 days after the stroke. Five patients were excluded; the remaining patients (10 men, 15 women; mean age, 70 years +/- 13 [standard deviation]) were separated into those with recanalization (n = 16) and those without recanalization (n = 9) at 24 hours. For patients with recanalization, the final infarct was outlined on unenhanced CT images obtained 5-7 days after the event and was superimposed on coregistered maps from the CT perfusion study performed at admission. Ischemic white matter tissue (cerebral blood flow [CBF] < 14 mL/min/100 g) was identified at the admission CT perfusion study, and the penumbra was defined as the difference between the ischemic region and the infarct region. RESULTS Infarct regions showed a matched decrease in CBF and cerebral blood volume (CBV) at admission, whereas penumbra regions showed a significant (P < .05) decrease in CBF but no change in CBV (P > .05) from contralateral values. A threshold CBF . CBV value of 8.14 was the most sensitive (95%, 20 of 21 regions) and specific (94%, 32 of 34 regions) parameter for differentiating between regions of ischemic white matter that recovered and regions of ischemic white matter that infarcted. CONCLUSION The product of CBF and CBV derived from CT perfusion data provided the best differentiation between regions of ischemic white matter that infarcted and regions of ischemic white matter that recovered 5-7 days after a stroke.

Hemodynamic instability during carotid artery stenting: the relative contribution of stent deployment versus balloon dilation.

OBJECT Hemodynamic instability may complicate carotid angioplasty and stenting in up to 40% of patients. The authors have previously demonstrated that primary self-expanding stent placement alone can gradually dilate severely stenosed carotid arteries without the use of balloons. The authors hypothesized that eliminating the balloon would reduce carotid baroreceptor stimulation, thereby decreasing the incidence of hemodynamic instability. METHODS Ninety-seven high surgical risk patients with symptomatic, severely stenosed carotid arteries were treated with the intention of using a self-expanding stent alone. Seventy-seven arteries (79%) were treated with stenting alone, and 20 required angioplasty (21%). RESULTS Intraprocedural bradycardia (heart rate < 60 bpm) developed in 29 patients (38%) and hypotension (systolic blood pressure < 90 mm Hg) occurred in 1 patient (1%) treated with stenting alone. Fourteen patients (70%) who underwent angioplasty and stenting had bradycardia, and hypotension developed in 4 (20%). Atropine, glycopyrrolate, or vasopressors were required in 8% of patients who received stenting alone, compared to 30% of patients who underwent angioplasty. In the first 24 hours after treatment, hypotension or bradycardia developed in 25 patients (32%) who had undergone stent placement alone, and in 15 patients (75%) after stent placement and balloon angioplasty. There was no difference in the occurrence of intra- or postprocedural hypertension (systolic blood pressure > 160 mm Hg) between patients treated with stenting alone or stenting and balloons. Factors independently associated with hemodynamic depression included baseline heart rate and balloon use. CONCLUSIONS Hemodynamic instability during and after carotid artery stenting was observed more frequently when balloon angioplasty was required than when stent placement was performed without concurrent balloon angioplasty.

Internal Carotid Artery Stenosis Measurement Comparison of 3D Computed Rotational Angiography and Conventional Digital Subtraction Angiography

Background and Purpose— Clinical trials have shown that carotid endarterectomy reduces stroke risk in symptomatic individuals with severe internal carotid artery (ICA) stenosis. As a result of these trials, digital subtraction angiography (DSA) became a standard of reference for ICA stenosis diagnosis. Newer 3D techniques provide a larger number of views than DSA, which may influence the estimated degree of stenosis. We evaluate this possibility by directly comparing stenosis grades from 3D computed rotational angiography (CRA) and DSA. Methods— As a prospective diagnostic study, we performed CRA and DSA on 26 consecutive symptomatic patients. Only 1 angiographic procedure was performed on normal asymptomatic arteries, yielding 42 arteries for comparison. Four neuroradiologists graded the CRA maximum intensity projections (MIPs) and DSA images, according to the North American Symptomatic Carotid Endarterectomy Trial guidelines. CRA studies included a search for the narrowest view by evaluating 60 MIPs generated at 3° intervals and measurement of actual artery diameters. Artery diameters and stenosis grades were analyzed graphically; statistical significance was determined using a paired t test. Results— The mean difference of 1.2% (CI, −18%, 21%) between CRA and DSA stenosis grades was not statistically significant (P=0.55). Agreement of the optimal CRA viewing angle was limited, with an interobserver variability of 24±13°. The interobserver variability of DSA and CRA stenosis grades, 9.1% (CI, 0%, 21%) and 9.4% (CI, 0%, 22%), respectively, was not significantly different (P=0.79). Conclusion— CRA provides stenosis grades equivalent to DSA, as well as absolute measurements, providing a comparison for newer 3D techniques.

Congenital Intercostal Arteriovenous Malformation

WEB This is a Web exclusive article. ntercostal arteriovenous malformations (AVMs) and fistulas (AVFs) are rare lesions, and few case reports have been published [1–7]. Most have been secondary to trauma or iatrogenic therapeutic procedures [1–6], and one case was presumably congenital in origin. All have had single arterial feeders and draining veins. We present a case of congenital intercostal AVM in a young patient initially diagnosed on the basis of MRI findings and treated by a combination of transarterial and transvenous endovascular therapy and direct surgery.

Idiopathic free-floating thrombus of the common carotid artery.

BACKGROUND The observation of an intraluminal common carotid artery thrombus overlying a wall defect at ultrasonography or angiography is unusual. To our knowledge, there are no previous reports of a free-floating thrombus in the common carotid artery. CASE REPORT A 45-year-old woman who was previously healthy and on no medications presented with acute hemiparesis and aphasia. Following testing that included carotid duplex and transcranial Doppler ultrasonography, diffusion-weighted magnetic resonance imaging, and digital subtraction angiography, the patient underwent emergency open embolectomy. No underlying wall defect was seen at the time of imaging or surgery. No obvious hypercoagulable state could be identified. Her NIH Stroke Scale score improved from 26 at admission to 2 at three months and 1 at one year. CONCLUSIONS Multimodal imaging may have improved diagnosis and management in this patient with a unique finding. The source of the thrombus remains obscure.

Comparison of maximum intensity projection and digitally reconstructed radiographic projection for carotid artery stenosis measurement.

Digital subtraction angiography is being supplanted by three-dimensional imaging techniques in many clinical applications, leading to extensive use of maximum intensity projection (MIP) images to depict volumetric vascular data. The MIP algorithm produces intensity profiles that are different than conventional angiograms, and can also increase the vessel-to-tissue contrast-to-noise ratio. We evaluated the effect of the MIP algorithm in a clinical application where quantitative vessel measurement is important: internal carotid artery stenosis grading. Three-dimensional computed rotational angiography (CRA) was performed on 26 consecutive symptomatic patients to verify an internal carotid artery stenosis originally found using duplex ultrasound. These volumes of data were visualized using two different postprocessing projection techniques: MIP and digitally reconstructed radiographic (DRR) projection. A DRR is a radiographic image simulating a conventional digitally subtracted angiogram, but it is derived computationally from the same CRA dataset as the MIP. By visualizing a single volume with two different projection techniques, the postprocessing effect of the MIP algorithm is isolated. Vessel measurements were made, according to the NASCET guidelines, and percentage stenosis grades were calculated. The paired t-test was used to determine if the measurement difference between the two techniques was statistically significant. The CRA technique provided an isotropic voxel spacing of 0.38 mm. The MIPs and DRRs had a mean signal-difference-to-noise-ratio of 30:1 and 26:1, respectively. Vessel measurements from MIPs were, on average, 0.17 mm larger than those from DRRs (P < 0.0001). The NASCET-type stenosis grades tended to be underestimated on average by 2.4% with the MIP algorithm, although this was not statistically significant (P=0.09). The mean interobserver variability (standard deviation) of both the MIP and DRR images was 0.35 mm. It was concluded that the MIP algorithm slightly increased the apparent dimensions of the arteries, when applied to these intra-arterial CRA images. This subpixel increase was smaller than both the voxel size and interobserver variability, and was therefore not clinically relevant.

Simple partial seizures in a 70-year- old female.

History A 70 year-old female presented with a history of recurrent stereotyped “spells” over the past six years. She described involuntary horizontal saccadic eye movements as the initial event. This was followed by tonic deviation of her head to the left. There was intermittent jerking of her head to the left and quivering of her lower lip and jaw. There was no loss of awareness but it was difficult for her to speak during the spells which typically lasted three to four minutes. Her speech was slurred for a further five to ten minutes. The spells had recurred approximately twice a year until a recent increase in their frequency (four episodes in three months), prompting the patient to seek medical attention. She had a history of migraines, chronic obstructive lung disease, a 50 pack-year smoking history, and several remote minor surgeries including ureteral stenting, appendectomy, hemorrhoidectomy, and hysterectomy. She had been involved in two motor vehicle accidents, 28 years and 6 years earlier, with no recognized craniocerebral injury on either occasion. Her family history was not contributory.

Sci‐PM Thurs ‐ 03: 3‐D angiography: Effect of the maximum intensity projection on the measurement of artery diameters

Our goal was to determine the impact of the maximum intensity projection (MIP) algorithm on quantitative analysis used for diagnosis and treatment planning of extracranial arterial disease. We performed 3‐D computed rotational angiography (CRA) on 26 consecutive symptomatic patients to verify an internal carotid artery (ICA) stenosis originally found using duplex ultrasound. These volumes of data were visualized using two different post‐processing projection techniques: MIP and digitally reconstructed radiographic(DRR) projection. A DRR is a radiographicimage simulating a conventional digitally subtracted angiogram (DSA), but it is derived computationally from the same CRA dataset as the MIP. By visualizing a single volume with two different projection techniques, the post‐processing effect of the MIP algorithm is isolated. Vessel measurements were made, according to the NASCET guidelines, and percentage stenosis grades were calculated. The NASCET‐type stenosis grades tended to be underestimated on average by 2.4% with the MIP algorithm, although this was not statistically significant (P=0.09). Moreover, the vessel measurements from the MIPs were consistently 0.17 mm larger than those from DRRs (P<0.0001). Thus, when applied to high‐contrast, high‐resolution CRA images, the MIP algorithm slightly increased the apparent dimensions of the arteries. This difference is not clinically relevant, due to the fact that it is only a fraction of the 0.38 mm voxel spacing. Moreover, the MIP dimensions could actually represent the truth, and that it is the sharp decrease near the edge of the intensity profile of the radiographicimages that causes an underestimation of the absolute dimensions.

Quantitative CT perfusion measurement: normal values and reproducibility in man

P32 Purpose To establish normal values of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) as measured by dynamic contrast enhanced computed tomography (CT Perfusion) and to determine their short-term variabilities in healthy volunteers. Method and Materials The studies involved ten healthy volunteers, 6 females and 4 males, between 39 and 49 years old. For each subject two single-slice contrast enhanced dynamic CT studies separated by an interval of 30 min were performed at the level of the basal ganglia. Arterial oxygen saturation (SaO 2 ), end-tidal CO 2 tension (ETCO 2 ), and blood pressure(BP) were continuously monitored to ensure the same basal conditions were maintained throughout the studies and the waiting period between them. Each study began with intravenous injection of 40 ml of contrast at 4 ml/s and at 5 s into the injection, 60 1 s CT scans were acquired continuously. Functional images of absolute CBF, CBV, and MTT were calculated by deconvolution of an intracranial artery’s contrast enhancement curve with tissue curves. Normal CBF, CBV and MTT values of the entire slice as well as those of frontal and insular grey matter, basal ganglia, frontal white matter, and the cerebellum were analyzed. Short-term variability was calculated using a standardized set of 24 regions of interest (ROI). The size of each ROI was about 4% of the entire brain slice. Results There were no significant differences in SaO 2 , ETCO 2 and BP between the two studies for each subject. CBF was the highest in insular grey matter (67.8 ml/100g/min), intermediate in frontal grey matter, basal ganglia, and cerebellum (42–48 ml/100g/min), and the lowest in frontal white matter (14.5 ml/100g/min). The values of CBV followed the same trend as CBF. Short-term variability was 13.3%, 12.4% and 8.8% for CBF, CBV and MTT respectively without significant differences among the parameters. Conclusion CT imaging of absolute CBF, CBV, and MTT in healthy volunteers provides results similar to those known from the literature. The short-term variabilities of these quantitative functional images are acceptable for clinical applications.