Increase In Mean Transit Time Research Articles

Assessment of CT perfusion indices of the clinicoradiological response to anti-tubercular therapy in patients with intestinal tuberculosis

To explore the possibility of using a novel technique, CT perfusion imaging, to monitor the response to anti-tubercular therapy (ATT) in patients with intestinal tuberculosis. A prospective observational study was performed in adults with treatment naive-intestinal tuberculosis. Clinical, endoscopic, and conventional radiological findings of patients were compared at baseline and post-ATT. CT perfusion imaging was performed with recording of six perfusion parameters (blood flow, blood volume, mean transit time, time to peak, maximum peak intensity, and permeability/blood flow extraction). Twenty-two patients (13 women, 59%) with a median age of 25 years were recruited. The terminal ileum and ileocaecal junction were the most frequent sites of involvement (59%), with multiple segments of the intestine being involved in 16 patients (73%). Median duration of ATT was 6 months (range 6-10 months). Complete clinical response was observed in 22/22 (100%) patients, endoscopic response in 12/12 (100%) patients, and radiological response in 10/13 (76%) patients. There was a significant decrease in mean blood flow, blood volume, maximum peak intensity, and an increase in mean transit time and time to peak on follow-up CT perfusion imaging performed after 6 months of ATT. Significant alterations in CT perfusion parameters were demonstrated following treatment, consistent with a decline in inflammation and vascularity. CT perfusion imaging of the bowel is a novel means to assess the radiological response to ATT in intestinal tuberculosis, although at the cost of a higher dose of radiation exposure.

Evaluation of MTT Heterogeneity of Perfusion CT Imaging in the Early Brain Injury Phase: An Insight into aSAH Pathopysiology.

The concept of early brain injury (EBI) is based on the assumption of a global reduction in brain perfusion following aneurysmal subarachnoid hemorrhage (aSAH). However, the heterogeneity of computed tomography perfusion (CTP) imaging in EBI has not yet been investigated. In contrast, increased mean transit time (MTT) heterogeneity, a possible marker of microvascular perfusion heterogeneity, in the delayed cerebral ischemia (DCI) phase has recently been associated with a poor neurological outcome after aSAH. Therefore, in this study, we investigated whether the heterogeneity of early CTP imaging in the EBI phase is an independent predictor of the neurological outcome after aSAH. We retrospectively analyzed the heterogeneity of the MTT using the coefficient of variation (cvMTT) in early CTP scans (within 24 h after ictus) of 124 aSAH patients. Both linear and logistic regression were used to model the mRS outcome, which were treated as numerical and dichotomized values, respectively. Linear regression was used to investigate the linear dependency between the variables. No significant difference in cvMTT between the patients with and those without EVD could be observed (p = 0.69). We found no correlation between cvMTT in early CTP imaging and initial modified Fisher (p = 0.07) and WFNS grades (p = 0.23). The cvMTT in early perfusion imaging did not correlate significantly with the 6-month mRS for the entire study population (p = 0.15) or for any of the subgroups (without EVD: p = 0.21; with EVD: p = 0.3). In conclusion, microvascular perfusion heterogeneity, assessed by the heterogeneity of MTT in early CTP imaging, does not appear to be an independent predictor of the neurological outcome 6 months after aSAH.

Abstract WP53: The Assessment Of Brain Water Content At Posttraumatic Ischemia: Ct Perfusion Study

Background: The influence of cerebral edema and secondary insults on the clinical outcome of traumatic brain injury (TBI) is well known. The studies of the brain water homeostasis dynamics at TBI remain rare, which determines the relevance of our work. The purpose is to study the changes in brain water homeostasis after TBI of varying severity compared to the cerebral microcirculation parameters. Materials: This non-randomized retrospective single-center study complies with the Helsinki Declaration. One hundred twenty-eight patients with posttraumatic ischemia (PCI) after moderate-to-severe TBI in the middle cerebral artery territory who presented between July 2015 and February 2022 to our hospital were included. PCI was determined using perfusion computed tomography (CT), and brain edema was determined using net water uptake (NWU) on baseline CT images. The patients were divided according to Marshall’s classification. Multivariate linear regression models were performed to analyze data. Results: NWU in PCI zones was significantly higher than in non-ischemic zones (8.1% versus 4.2%; P <0.001). In the multivariable regression analysis, the mean transit time increase was significantly and independently associated with higher NWU ( R 2 = 0,089, P <0.01). In the PCI zone, cerebral blood flow (CBF), volume (CBV), and time to peak (TTP) were not significantly associated with NWU values ( P >0.05). No significant differences existed between the NWU values in PCI foci in different Marshall groups ( P =0.308). Conclusion: The Marshall classification does not seem to be able to predict the progression of posttraumatic ischemia. The blood passage delay through the cerebral microvascular bed was significantly accompanied by brain tissue water uptake increase in the PCI focus.

On Net Water Uptake in Posttraumatic Ischemia Foci.

The influence of cerebral edema and resultant secondary complications on the clinical outcome of traumatic brain injury (TBI) is well known. Clinical studies of brain water homeostasis dynamics in TBI are limited, which determines the relevance of our work. The purpose is to study changes in brain water homeostasis after TBI of varying severity compared to corresponding cerebral microcirculation parameters. This non-randomized retrospective single-center study complies with the Helsinki Declaration for patient's studies. The study included 128 patients with posttraumatic ischemia (PCI) after moderate-to-severe TBI in the middle cerebral artery territory who were admitted to the hospital between July 2015 and February 2022. PCI was evaluated by perfusion computed tomography (CT), and brain edema was determined using net water uptake (NWU) on baseline CT images. The patients were allocated according to Marshall's classification. Multivariate linear regression models were performed to analyze data. NWU in PCI areas were significantly higher than in patients with its absence (8.1% vs. 4.2%, accordingly; p<0.001). In the multivariable regression analysis, the mean transit time increase was significantly and independently associated with higher NWU (R2=0.089, p<0.01). In the PCI zone, cerebral blood flow, cerebral blood volume, and time to peak were not significantly associated with NWU values (p>0.05). No significant differences were observed between the NWU values in PCI foci in different Marshall groups (p=0.308). Marshall's classification does not predict the progression of posttraumatic ischemia. The blood passage delays through the cerebral microvascular bed is associated with brain tissue water content increase in the PCI focus.

Advanced imaging to assess longitudinal vascular changes in brain metastases treated with checkpoint inhibition.

3059 Background: Immune checkpoint inhibitors (ICI) have recently been shown to be effective for brain metastases (BM) in melanoma and lung cancer. Several studies demonstrate that 20-50% of BM patients respond to ICI. The reasons behind this wide variability in treatment response is not clear. Therefore, using physiologic imaging, we seek to identify the longitudinal biological changes exerted on BM as a result of ICI administration. Methods: Given the importance of aberrant tumor vasculature in cancer proliferation, we have focused on assessing changes in vascular physiology. We analyzed standard post-contrast and dynamic susceptibility contrast (DSC) MRI to identify characteristic vascular signatures as part of an ongoing Phase 2 study of pembrolizumab for patients with untreated or progressive, previously treated BM from any histology. Tumor volume measurements were calculated by summating all enhancing voxels. As per modified RECIST and RANO criteria for immunotherapy, volumetric increase of &gt; 40% was defined as progressive disease (PD), a decrease of &gt; 60% as partial response (PR), and stable disease (SD) as between -60% and +40%. Results: 35 patients, out of the total cohort of 60, have undergone DSC-MRI analysis. Histologies include 15 with breast cancer, 6 with non-small cell lung cancer, 4 with melanoma, and 10 with other cancers. At baseline, the total number of BM was 1-50+ per patient. Based on summing the entire enhancing intracranial disease burden, best volumetric responses for the 35 evaluable patients include 4 PR, 12 SD, and 19 PD. Thus far, we found that ICI-resistant BM had a 50% increase in cerebral blood flow (CBF), 105% increase in cerebral blood volume (CBV), a 15% increase in mean transit time (MTT), and an 80% increase in vessel caliber at 6 weeks post-treatment. On the other hand, ICI-responsive BM had no change in CBF, a 33% increase in CBV, a 10% decrease in MTT, and no change in vessel caliber. Ongoing analysis to uncover additional vascular changes (e.g. tumor oxygenation, vessel size index) within BM to ICI are pending. Conclusions: Our data provides evidence that effective ICI for BM is associated with unique intra-tumoral vascular physiology. With final analysis, we will uncover other facets of vascular physiology that correlate with ICI response, and may reveal mechanisms of response/resistance within tumors to ICI.

Abstract 37: Increased Mean Transit Time and Blood Brain Permeability in Asymptomatic White Matter Lesions of Ischemic Origin

Introduction: White matter lesions of presumed ischemic origin (WMH) have been associated with increased risk of stroke, cognitive and motor decline, and are a subject of public health research. Engineering new MRI pipelines allowing for determination of mean transit time (MTT), and blood brain barrier permeability (BBBP), within WMH lesions is required for long-term population-based studies of lesion progression in patients with dementia and vascular cognitive impairment. Methods: WMH lesion volumes in 24 asymptomatic individuals was determined using an automated segmentation methodology, S3DL, with manual correction to remove false positives. A double contrast injection scheme was used to measure both K trans using dynamic contrast enhanced (DCE) imaging and K 2 using dynamic susceptibility contrast (DSC) imaging which also provided perfusion-related measures. BBBP was measured as k 2 within segmented WMH lesions and compared with normal white and gray matter. Results: The mean transit time (MTT) was found to be significantly prolonged (8.11, p&lt;0.001Wilcoxon Signed-Rank Test) in WMH lesions when compared to normal appearing white and gray matter. There was no significant difference in DCE-K trans (0.018, p=0.351) between the lesions and the white/gray matter. Permeability measured in the WMH lesions using the DSC-K 2 method was increased and was correlated withincreasing total WMH lesion volume (spearman correlation 0.44; p&lt; 0.046). Conclusion: In this first study using an advanced WMH lesion automated segmentation pipeline, we measured DCE and DSC perfusion and permeability variables within WMH lesions and compared them to normal white and grey matter in healthy people. We observed increasing MTT, within WMH lesions as compared to unaffected white and gray matter. Using the DSC-K 2 method, BBBP was higher within WMH lesions in these asymptomatic people, and correlated with increasing total lesion volume.

Normalization of reduced functional connectivity after revascularization of asymptomatic carotid stenosis

Internal carotid artery stenosis is a risk factor for ischemic stroke. Even in the absence of visible structural brain changes, patients with asymptomatic stenosis are prone to cognitive impairment. On a neuronal level, it was suggested that stenosis may lead to disturbed functional brain connectivity. If so, carotid revascularization should have an effect on hypothesized brain network disturbances. We studied functional connectivity in a motor network by resting-state electroencephalography in 12 patients with high grade asymptomatic carotid stenosis before and after interventional or surgical revascularization as compared to 23 controls. In patients with stenosis, functional connectivity of neural oscillations was significantly decreased prior and improved returning to normal connectivity after revascularization. In a subgroup of patients, also studied by contrast perfusion magnetic resonance imaging, reduced connectivity was associated with decreased regional brain perfusion reflected by increased mean transit time in the middle cerebral artery borderzone. Cognitive testing revealed only minor differences between patients and controls. In summary, we identified oscillatory connectivity changes in patients with asymptomatic carotid stenosis correlating with regional hypoperfusion, which both normalized after revascularization. Hence, electrophysiological changes might be a reversible precursor preceding macroscopic structural brain damage and behavioral impairment in patients with asymptomatic carotid stenosis.

Perceptions of Perioperative Stroke Among Chinese Anesthesiologists: Starting a Long March to Eliminate This Underappreciated Complication.

Perceptions of Perioperative Stroke Among Chinese Anesthesiologists: Starting a Long March to Eliminate This Underappreciated Complication.

Stuttering lacunar infarction captured on serial MRIs

A 61-year-old man with a history of untreated hyperlipidemia presented with acute onset of dysarthria and right-sided weakness. His symptoms had improved but not resolved upon arrival at the hospital (NIH Stroke Scale [NIHSS] score was 4). Brain MRI showed a hyperintense lesion in the medial left pons on diffusion-weighted imaging (DWI) with a matching area of hypointensity on apparent diffusion coefficient map. The fluid-attenuated inversion recovery (FLAIR) sequence showed no changes in this area, suggesting a hyperacute lesion. There was no evidence of focal stenosis of the large intracranial vessels (figure 1) or intracranial hemorrhage. Perfusion-weighted imaging demonstrated an area of increased mean transit time (MTT) within the ischemic lesion (figure 2A). The patient's symptoms had completely resolved after the imaging (NIHSS score = 0). His symptoms recurred 30 minutes later for only 5 minutes. Brain MRI repeated 2 hours later, while asymptomatic, showed complete resolution of the abovementioned lesions (figure 2B). Therefore, IV thrombolysis was not indicated. The patient was admitted to the hospital with a diagnosis of TIA for further workup. He was started on aspirin 81 mg and atorvastatin 80 mg daily. Systolic blood pressure values ranged from 103 to 154 mm Hg, with most values between 110 and 140 mm Hg. No clear association between blood pressure and neurologic symptoms was noted during hospital admission. On the third day of hospitalization, the patient was discharged home while he remained asymptomatic and repeat brain MRI was intact (figure 2C).

How far is arterial spin labeling MRI from a clinical reality? Insights from arterial spin labeling comparative studies in Alzheimer's disease and other neurological disorders.

How far is arterial spin labeling MRI from a clinical reality? Insights from arterial spin labeling comparative studies in Alzheimer's disease and other neurological disorders.

Bilateral thalamic infarction due to artery of percheron occlusion with corresponding CT perfusion abnormalities

Background: The Artery of Percheron (AOP) is a rare anatomic variant that supplies the bilateral medial thalami from a common origin; occlusion results in a characteristic pattern of bilateral thalamic infarction seen on neuroimaging. To date, we have not identified any cases in the literature describing corresponding ischemic changes seen on hyperacute CT Perfusion imaging. We aimed to characterize perfusion abnormalities seen in AOP occlusion by describing a case presentation, highlighting the importance of recognizing this syndrome clinically, and radiologically, in an acute stroke presentation. Methods: Description of a case, and literature search on PubMed. Results: A 74-year-old man was seen in the ER as a Code Stroke protocol with acute alteration of level of consciousness (LOC). ER assessment showed no focal abnormalities and was significant only for disorientation. CT/CTA/CTP initially appeared unremarkable for acute abnormalities. His LOC deteriorated requiring intubation, and subsequent MRI showed bilateral thalamic infarction. Further CT Perfusion review demonstrated increased Mean Transit Time and decreased Blood Flow without Volume abnormalities in the bilateral paramedian thalami. Conclusion: AOP infarction is an uncommon cause of bilateral thalamic infarction. We have demonstrated a case highlighting perfusion abnormalities not previously reported in AOP occlusion, illustrating the importance and utility of advanced CT perfusion imaging whilst considering less common stroke syndromes.

Perfusion computed tomography as functional biomarker in randomized run-in study of bevacizumab and everolimus in well-differentiated neuroendocrine tumors.

This study aimed to assess the antitumor activity of everolimus and bevacizumab among patients with advanced neuroendocrine tumors and to assess perfusion computed tomography (CT) as a potential functional biomarker. Patients with low- to intermediate-grade neuroendocrine tumors received one 3-week cycle of 15 mg/kg of bevacizumab on day 1 or 10 mg of everolimus daily. Subsequent cycles consisted of the combination of both drugs. Perfusion CTs were performed at baseline and at the end of cycles 1 and 3. Therapy decreased blood flow (BF) proportional to baseline measurements. Bevacizumab was associated with a 44% decrease in BF (P < 0.0001). After the addition of everolimus, a further 29% decrease (P = 0.02) in BF was observed. Everolimus alone was associated with 13% increase in mean transit time (P = 0.02). Clinical activity was demonstrated, with a confirmed response rate of 21% and a median progression-free survival of 14.6 (95% confidence interval, 13.0-16.1) months. Pretreatment tumor permeability surface (P = 0.009), posttreatment mean transit time (P = 0.003), percent reduction in BF (P = 0.03), and percent reduction in blood volume (P = 0.002) were associated with best percent reduction in tumor diameters. Bevacizumab and everolimus demonstrated antitumor activity. Perfusion CT is a promising tool for the development of antiangiogenic strategies and for the selection of patients who are likely to benefit from therapy.

Abstract T P203: Areas of Cerebral Ischemia Have Increased Propensity to Convert to Infarct Among Diabetics

Diabetes influences ischemic stroke outcome. While several theories are proposed, the mechanism for worse outcomes is unclear. Perfusion computed tomography (PCT) helps identify stroke patients who would benefit from endovascular therapy. Our hypothesis was that PCT could potentially be used to elucidate the biological basis of poor outcomes among diabetics with stroke Methods: Patients with ischemic stroke that underwent PCT at admission from August 2011 to March 2012 were reviewed. PCT protocol included 4 supratentorial slices, 8mm thick. Areas of increased mean transit time(MTT) were traced and marked as ischemic area. Area of preserved cerebral blood volume(CBV) was penumbra. CBV and MTT were compared among diabetics and non-diabetics. Results: The study included 44 patients: 15 diabetic and 29 non-diabetics. The age, sex, race distributions and NIH stroke scale in both groups were similar. There were no differences in risk factors such as hypertension, atrial fibrillation and smoking. The average MTT was similar for both groups in the ischemic area (8.1ml/100g in diabetics and 8.7ml/100g in non diabetics, p=0.43) and within penumbra (8.4ml/100g in diabetics and 9.2 in non diabetics, p=0.32). The CBV was significantly lower among diabetics within the ischemic area (2.8sec vs.3.5sec among nondiabetics, p=0.04) as well as penumbra (2.8sec vs. 3.6sec in nondiabetics, p=0.03). This suggests an increased propensity for penumbra to convert to infarct among diabetics. In conclusion, PCT evaluation suggests that a lower CBV could explain worse outcomes among diabetics with stroke. Microvascular disease and endothelial dysfunction should be investigated as potential mechanisms for lower CBV and worse outcomes among diabetics.

Magnetic Resonance and Computed Tomography Imaging of the Structural and Functional Changes of Pulmonary Arterial Hypertension

The current Dana Point Classification system (2009) distinguishes elevation of pulmonary arterial pressure into pulmonary arterial hypertension (PAH) and pulmonary hypertension. Fortunately, PAH is not a common disease. However, with the aging of the First World's population, heart failure has become an important outcome of pulmonary hypertension, with up to 9% of the population involved. PAH is usually asymptomatic until late in the disease process. Although features that are indirectly related to PAH are found on noninvasive imaging studies, its diagnosis and management still require right heart catheterization. Imaging features of PAH include the following: (1) enlargement of the pulmonary trunk and main pulmonary arteries; (2) decreased pulmonary arterial compliance; (3) tapering of the peripheral pulmonary arteries; (4) enlargement of the inferior vena cava; and (5) increased mean transit time. The chronic requirement to generate high pulmonary arterial pressure measurably affects the right heart and main pulmonary artery. This change in physiology causes the following structural and functional alterations that have been shown to have prognostic significance: relative area change (RAC) of the pulmonary trunk, right ventricular stroke volume index, right ventricular stroke volume, right ventricular end-diastolic volume index, left ventricular end-diastolic volume index, and baseline right ventricular ejection fraction <35%. All of these variables can be quantified noninvasively and followed up longitudinally in each patient using magnetic resonance imaging to modify the treatment regimen. Untreated PAH frequently results in rapid clinical decline and death within 3 years of diagnosis. Unfortunately, even with treatment, fewer than half of these patients are alive at 4 years.

Assessment of response to sorafenib in advanced hepatocellular carcinoma using perfusion computed tomography: Results of a pilot study

This prospective pilot study investigated the feasibility of perfusion computed tomography parameters as surrogate markers of angiogenesis and early response following sorafenib administration in patients with advanced hepatocellular carcinoma. Ten patients were evaluated with perfusion computed tomography before starting sorafenib and after 3 months. Blood flow, blood volume, mean transit time, hepatic arterial fraction, and permeability surface-product were compared in tumour lesions and in hepatic parenchyma at baseline and at follow-up. Correlation between these parameters and changes in alpha-fetoprotein levels was calculated. At baseline, blood volume, blood flow, hepatic arterial fraction and permeability surface values were higher in lesions compared to those in hepatic parenchyma, while mean transit time was lower (p<0.05). After sorafenib treatment, only mean transit time was significantly increased versus baseline (p<0.05). At follow-up, plasma alpha-fetoprotein levels decreased in all patients. At follow-up, an inverse correlation was observed between baseline mean transit time and changes in alpha-fetoprotein (r=-0.6685, p=0.0125), as well as a correlation between baseline blood flow and alpha-fetoprotein (r=0.6476, p=0.0167). This pilot study suggests that after sorafenib treatment an increase in mean transit time observed in tumour lesions is inversely correlated with alpha-fetoprotein reductions after therapy. Mean transit time may represent a possible marker of response irrespectively of alpha-fetoprotein values.

Perfusion computed tomography relative threshold values in definition of acute stroke lesions

BackgroundPerfusion computed tomography (CT) is a relatively new technique that allows fast evaluation of cerebral hemodynamics by providing perfusion maps and gives confirmation of perfusion deficits in ischemic areas. Some controversies exist regarding accuracy of quantitative detection of tissue viability: penumbra (tissue at risk) or core (necrosis).PurposeTo define brain tissue viability grade on the basis of the perfusion CT parameters in acute stroke patients.Material and MethodsA multimodal CT imaging protocol; unenhanced CT of the brain, CT angiography of head and neck blood vessels, followed by brain perfusion CT and 24 h follow-up brain CT was performed. Perfusion deficits were detected first visually, with subsequent manual quantitative and relative measurements in affected and contra-lateral hemisphere in 87 acute stroke patients.ResultsVisual perfusion deficit on perfusion CT images was found in 78 cases (38 women, 40 men; mean age, 30–84 years). Penumbra lesions (n = 49) and core lesions (n = 42) were detected by increased mean transit time (MTT) on perfusion CT maps in comparison to contra-lateral hemispheres. Cerebral blood volume (CBV) mean values in the penumbra group were increased in the penumbra group and decreased in the core group. Cerebral blood flow (CBF) values were decreased in penumbra and markedly decreased in core lesion.ConclusionPerfusion CT measurements are reliable in estimation of penumbra and core lesions in acute stroke patients, if relative threshold values are used. The most accurate parameter of hypoperfusion is increased MTT above 190%. Relative threshold values for irreversible lesion are CBF <30–40% and CBV <40% in comparison to contra-lateral hemisphere. Penumbra lesion is characterized by MTT increase and CBF decrease, while CBV shows variable values.

Abstract WP427: Day Eight CT Perfusion Imaging for Evaluation of Delayed Cerebral Ischemia Risk and Decreased Length of Stay Following Aneurysmal Subarachnoid Hemorrhage

Objective: Hospital stay alone accounts for 2/3 the cost of aneurysmal subarachnoid hemorrhage (aSAH) management. Our objective was to assess the ability of CT perfusion (CTP) imaging to predict delayed cerebral ischemia (DCI) risk in those who are neurologically intact in order to safely decrease the length of hospital stay for low risk aSAH patients. Methods: A retrospective analysis of all aSAH admitted to our neurological intensive care unit (NICU) from 3/2011-3/2012. Per our protocol all patients were admitted to the NICU for 10 days followed by a 4 day ward admission. Additionally, all patients underwent a CTP study on post-bleed day 8 to screen for evidence of radiographic vasospasm. DCI was defined as the presence of neurological deficit not attributable to other etiologies. All CTP images were interpreted by a Neuroradiologist. CTP was considered positive if there was evidence of match or mismatch. Mismatch was defined as decreased cerebral blood flow or increased mean transit time with associated blood volume loss of &lt;20%. Results: A total of 58 aSAH were admitted. Day 8 CTPs were performed on 42 (72%) with 71% female, mean age 52.21 (±13.25), mean Fisher 3.38 (2-4) and mean Hunt/Hess 2.39 (1-5). Eighteen (43%) patients had negative CTPs with baseline neurological exams. None of these 18 patients went on to develop DCI during their 14 day admission. Conclusion: Our data shows that aSAH patients who are neurologically intact and have a negative post-bleed day 8 CTP are not at risk for DCI. We conclude that an 8 day NICU admission with an additional 2 day in-patient stay is sufficient to safely manage this patient population. Our data is limited by a small sample size and retrospective analysis. Future directions of research include additional prospective studies for reproducibility.

Abstract WP444: Older Age, Hypertension and Diabetes Influence the Proportion of Salvageable Ischemic Tissue Following Stroke

Objective: Increasing age, hypertension (HTN), diabetes (DM), hyperlipidemia, smoking and chronic kidney disease are implicated in endothelial dysfunction. Our hypothesis was that endothelial dysfunction would decrease the amount of salvageable ischemic tissue (penumbra) in patients with acute ischemic stroke. Methods: Patients with ischemic stroke that underwent perfusion computed tomography (PCT) at admission from August 2011 to March 2012 were reviewed. Demographics and risk factors were abstracted. PCT protocol included 4 supratentorial slices, 8 mm thick. Areas of increased mean transit time were traced and marked as ischemic area. Corresponding area of preserved cerebral blood volume was labeled as penumbra area. The ischemic and penumbra areas in four slices were added and multiplied by the slice thickness (0.8 cm) to give ischemic volume (IV) and penumbra volume (PV) respectively. The proportion of penumbra (penumbra/ischemia volume) was calculated and compared across the different risk factors. Results: Of the 47 patients that underwent PCT, 43 (22 males; mean age 61.6 ±12.6 years) had perfusion abnormalities. Subjects younger than 45 years had significantly higher median IV (118.8 cm 3 vs. 58.4 cm 3 ; p=0.01) and median PV (97.9 cm 3 vs. 38.7 cm 3 ; p&lt;0.01). The median proportion of penumbra, was significantly lower in subjects older than 45 years (72.2% vs. 82.0%; p=0.04). Other factors that demonstrated trends toward a decrease in proportion of penumbra, but did not reach statistical significance due to small numbers: HTN (72.8% vs. 80.0% ; p=0.20) and DM (67.5% vs. 75.7%; p=0.56). In our subset, smoking, hyperlipidemia and kidney disease did not affect the penumbra proportion. Conclusion: Older patients and those with HTN or DM are less likely to have a large proportion of salvageable penumbra. While endothelial dysfunction may be a common denominator to these risk factors, the biological mechanisms underlying this phenomenon need to be elucidated.

Recognizing False Ischemic Penumbras in CT Brain Perfusion Studies

Computed tomography (CT) plays a pivotal role in the diagnosis of acute stroke and in treatment decision making. CT perfusion imaging performed with intravenous iodinated contrast material allows calculation of the time to peak enhancement, mean transit time, and cerebral blood volume, important parameters for differentiating between an ischemic penumbra, which might benefit from intravascular therapy with thrombolytic agents, and infarcted tissue, which would not benefit from such therapy. Differentiation between the two entities is important because thrombolytic therapy is associated with an increased risk for intracranial hemorrhage. A finding of delay in peak enhancement or increased mean transit time in a region with normal or only slightly abnormal cerebral blood volume is suggestive of an ischemic penumbra; however, accurate interpretation of the CT perfusion parameters may be difficult in the presence of a cerebrovascular anatomic variant or physiologic condition that produces benign oligemia leading to a false appearance of penumbra. For this reason, CT perfusion parameters must be correlated with the clinical history and findings at unenhanced head CT, angiography or CT angiography, and diffusion-weighted magnetic resonance imaging. The authors identify five possible causes of false penumbras, each of which produces a different pattern at imaging: upstream flow restriction, evolution of ischemic change, vascular dysregulation, positioning of the patient's head at an angle during image acquisition, and variant anatomy in the circle of Willis. Familiarity with the imaging patterns and causes of false penumbras may increase the radiologist's confidence in diagnosis and help avoid costly errors in treatment.

P-015 Novel use of the pipeline embolization device for reperfusion of the middle cerebral artery post aneurysm clipping

IntroductionSurgical clipping of intracranial aneurysm can be complicated by clip encroachment of the parent artery. We present a case where symptomatic MCA stenosis occurring after clipping of a left carotid...