Acute stroke evaluated by time-to-peak mapping during initial and early follow-up perfusion CT studies

BACKGROUND AND PURPOSE: Early diagnosis of perfusion deficits in patients with acute stroke could guide treatment decisions and improve prognosis. We investigated the sensitivity of perfusion CT studies using parametric time-to-peak maps to assess ischemic brain tissue with respect to early infarct signs on native CT scans. METHODS: First-pass, single-section perfusion CT was performed in 20 patients who presented with symptoms of acute stroke within 6 hours of onset. Initial CT perfusion studies were compared with follow-up studies within 30 hours in 10 patients. A manual, region of interest (ROI)-based, local evaluation procedure was performed to determine delayed time-to-peak values and diminished peak amplitudes. In addition, time-to-peak parameter maps were processed off-line from the dynamic CT data sets to identify areas of perfusion deficits, which were expressed as hemispheric lesion areas (HLAs). Evolution of the ischemic regions was assessed by comparing the HLA on the initial and follow-up studies as well as on the native CT scan of the follow-up studies. RESULTS: Diagnostic time-to-peak maps were generated in 19 of 20 initial and in nine of 10 follow-up perfusion CT studies. The initial time-to-peak map showed perfusion deficits in 14 of 20 patients. Hemispheric territorial infarcts were diagnosed with a sensitivity of 93%. Perfusion deficits in two patients with brain stem infarctions and three patients with lacunar strokes were missed. Follow-up time-to-peak maps showed the extent of reperfusion after various therapeutic strategies. CONCLUSION: Perfusion CT is potentially useful for detecting cerebral perfusion deficits in acute ischemic stroke before morphologic changes are observable on native CT scans. Compared with a locally restricted ROI-based evaluation, time-to-peak maps provide sensitive, global indications of malperfused brain areas, facilitate lesion localization, and allow assessment of the evolution of the infarction during follow-up.     

Improvement of sensitivity and interrater reliability to detect acute stroke by dynamic perfusion computed tomography and computed tomography angiography

OBJECTIVE: To assess the benefits of additional computed tomography perfusion (CTP) and computed tomography angiography (CTA) on the detection of early stroke, vessel occlusion, estimated infarct size, and interrater reliability. METHODS: Sixty-seven consecutive patients underwent nonenhanced computed tomography (CT) imaging, CTA, and CTP. The final diagnosis of stroke was made from follow-up neuroimaging. A first diagnosis was made on-site by the physician on duty. Three experienced neuroradiologists blinded to follow-up findings analyzed the data set off-line, evaluated CT for signs of acute stroke, and subsequently evaluated CTP and CTA for infarction-related perfusion deficits and vessel abnormalities. RESULTS: Computed tomography perfusion and CTA increased the time from CT start to diagnosis from 2 minutes to 10 minutes. Sensitivity to detect acute stroke increased significantly in all investigators from 0.46-0.58 to 0.79-0.90 compared with CT (<0.005). The interrater weighted kappa value increased from 0.35 to 0.64. Estimation of infarct size was not improved. CONCLUSION: Computed tomography perfusion and CTA provide an effective add-on to standard CT in acute stroke imaging by significantly increasing the sensitivity and reliability of infarct detection.     

Multiphasic perfusion computed tomography in hyperacute ischemic stroke: comparison with diffusion and perfusion magnetic resonance imaging

PURPOSE: The purpose of this study was to compare multiphasic perfusion computed tomography (CT) with diffusion and perfusion magnetic resonance imaging (MRI) in predicting final infarct volume, infarct growth, and clinical severity in patients with hyperacute ischemia untreated by thrombolytic therapy. METHOD: Multiphasic perfusion CT was performed in 19 patients with ischemic stroke within 6 hours of symptom onset. Two CT maps of peak and total perfusion were generated from CT data. Diffusion-weighted imaging (DWI) and perfusion MRI were obtained within 150 minutes after CT. Lesion volumes on CT and MRI were compared with final infarct volume and clinical scores, and mismatch on CT or MRI was compared with infarct growth. RESULTS: The lesion volume on the CT total perfusion map strongly correlated with MRI relative cerebral blood volume (rCBV), and that on the CT peak perfusion map strongly correlated with MRI relative cerebral blood flow (rCBF) and rCBV (P < 0.001). The lesion volume on unenhanced CT or DWI moderately correlated with final infarct volume, but only lesion volume on unenhanced CT weakly correlated with baseline clinical scores (P = 0.024). The lesion volumes on the CT peak perfusion map and MRI rCBF similarly correlated with final infarct volume and clinical scores and more strongly than those on mean transit time (MTT) or time to peak (TTP). DWI-rCBF or CT mismatch was more predictive of infarct growth than DWI-MTT or DWI-TTP mismatch. CONCLUSION: Multiphasic perfusion CT is useful and of comparable utility to diffusion and perfusion MRI for predicting final infarct volume, infarct growth, and clinical severity in acute ischemic stroke.     

Intracranial arterial dissection

We review the angiographic and CT findings, precipitating factors and clinical features in nine patients with ten intracranial arterial dissections. The internal carotid artery was involved in five cases, the vertebral artery in four and the posterior inferior cerebellar artery in one. Angiography revealed irregular stenosis in four cases, irregular stenosis and a pseudoaneurysm in two, irregular stenosis and irregular dilatation in one, arterial occlusion in two and a pseudoaneurysm in one. CT demonstrated an infarct in four cases, a dense middle cerebral artery in two and subarachnoid haemorrhage in one. A possible precipitating factor was identified in five cases. Six patients recovered well, while three had persisting neurological deficits. Received: 30 August 1997 Accepted: 31 October 1997     

Serial CT and MRI of ischaemic cerebral infarcts: frequency and clinical impact of haemorrhagic transformation

The frequency, predisposing factors and clinical consequences of haemorrhagic infarcts and damaged blood-brain barrier as shown by contrast enhancement (CE) in ischaemic cerebral infarcts are controversial. We prospectively compared the sensitivity of CT and MRI to haemorrhagic transformation (HT) and CE. We also wished to investigate the clinical significance of HT and factors possibly associated with it. We studied 36 patients with acute ischaemic infarcts in the middle cerebral artery territory during the first 2 weeks after the ictus. After CT and rating of the neurological deficit on admission, serial examinations with clinical neuromonitoring, contrast-enhanced CT and MRI were done on the same day. The occurrence and severity of HT were correlated with CE, stroke mechanism, infarct size, development of neurological deficits and antithrombotic treatment. The frequency of HT detected by MRI was 80 %. CE usually preceded HT or was seen simultaneously. MRI had a higher sensitivity than CT to HT and CE. Severity of HT was positively correlated with infarct size (P < 0.01). HT had no influence on patient's neurological status. Neither the type of antithrombotic treatment nor the stroke mechanism was associated with the severity of HT. No parenchymal haemorrhage occurred. Received: 10 November 1998 Accepted: 29 July 1999     

Multiphasic Perfusion CT in Acute Middle Cerebral Artery Ischemic Stroke: Prediction of Final Infarct Volume and Correlation with Clinical Outcome

Objective

To assess the utility of multiphasic perfusion CT in the prediction of final infarct volume, and the relationship between lesion volume revealed by CT imaging and clinical outcome in acute ischemic stroke patients who have not undergone thrombolytic therapy.

Materials and Methods

Thirty-five patients underwent multiphasic perfusion CT within six hours of stroke onset. After baseline unenhanced helical CT scanning, contrast-enhanced CT scans were obtained 20, 34, 48, and 62 secs after the injection of 90 mL contrast medium at a rate of 3 mL/sec. CT peak and total perfusion maps were obtained from serial CT images, and the initial lesion volumes revealed by CT were compared with final infarct volumes and clinical scores.

Results

Overall, the lesion volumes seen on CT peak perfusion maps correlated most strongly with final infarct volumes (R²=0.819, p<0.001, slope of regression line=1.016), but individual data showed that they were less than final infarct volume in 31.4% of patients. In those who showed early clinical improvement (n=6), final infarct volume tended to be overestimated by CT peak perfusion mapping and only on total perfusion maps was there significant correlation between lesion volume and final infarct volume (R²=0.854, p=0.008). The lesion volumes depicted by CT maps showed moderate correlation with baseline clinical scores and clinical outcomes (R=0.445-0.706, p≤0.007).

Conclusion

CT peak perfusion maps demonstrate strong correlation between lesion volume and final infarct volume, and accurately predict final infarct volume in about two-thirds of the 35 patients. The lesion volume seen on CT maps shows moderate correlation with clinical outcome.     

骨梗死的影像学改变及病理表现

目的 探讨骨梗死的病理演变及其影像学表现。方法6例骨梗死中5例行平片检查，4例行CT检查，3例行MR检查。结果 6例骨梗死共累及10个部位，股骨下段4个，胫骨上段4个，胫骨下段1个，股骨颈及粗隆部1个。其中2个部位经手术病理证实，平片均显示髓腔内不均匀性骨化。CT显示髓腔内呈地图样改变，周围环以硬化边。MRI显示病变的组成分为3部分，中心是完全坏死的骨髓和骨组织，外围是部分坏死的骨髓和骨组织，再外边是充血区及正常骨组织。1例于骺早闭的上方发现骨梗死，根据骨折愈合动物实验研究，认为是静脉窦栓塞所致。结论 MRI是检查诊断早期骨梗死最为有效的方法，可以发现早期病变。X线平片对于中晚期病变有帮助，CT较平片敏感，骨梗死的诊断最好采用MRI、CT以及平片相结合。     

The validity and reliability of signs of early infarction on CT in acute ischaemic stroke

It has been suggested that subtle signs of early cerebral infarction on CT are important indicators of outcome and of the effect of thrombolytic treatment in acute ischaemic stroke. We studied these signs prospectively, in 260 patients with an anterior circulation stroke from a European-Australian randomised trial of lubeluzole in acute ischaemic stroke. Interobserver reliability was assessed by means of the ϰ statistic. The validity of the early signs was assessed by comparing the assessments of the first CT with another CT at 1 week after the onset of stroke, and with stroke outcome at 12 weeks. Each initial CT study was assessed by two of a group of five reviewers, who were blinded to each other's assessments and to the findings on the follow-up CT. The images were assessed twice, once without clinical information and again after disclosure of the side (left or right hemisphere) of the lesion. All reviewers were experienced clinicians with a special interest and training in vascular neurology and CT. The median time between stroke onset and the first CT was 3.2 h; 59 % of the patients were imaged within 3 h and 77 % within 6 h. More than half of the patients (52 %) had a large middle cerebral artery territory (MCA) infarct on follow-up CT. Chance-adjusted interobserver agreement (ϰ) for any early infarct was 0.27 (95 % confidence interval (CI): 0.15 to 0.39). Agreement (ϰ) on the extent of a middle cerebral artery (MCA) infarct and on the indication for treatment with recombinant tissue plasminogen activator (rt-PA) was fair: 0.37 and 0.35, respectively. Patients with early signs of an infarct of more than 1/3 of the MCA territory were more likely to have a large MCA infarct on follow-up CT (odds ratio 5.7, 95 % confidence interval 2.8–11.5); the positive and negative predictive value of these signs was 81 % and 57 %, respectively. Chance-adjusted interobserver agreement on early, subtle signs of a large MCA territory infarct on CT by neurologists was thus no more than fair, and the accuracy of prediction of actual infarct size on the basis of these signs only moderate, under circumstances which resemble everyday clinical practice. Received: 11 October 1999/Accepted: 20 December 1999     

Does Preinterventional Flat-Panel Computer Tomography Pooled Blood Volume Mapping Predict Final Infarct Volume After Mechanical Thrombectomy in Acute Cerebral Artery Occlusion?

Purpose

Decreased cerebral blood volume is known to be a predictor for final infarct volume in acute cerebral artery occlusion. To evaluate the predictability of final infarct volume in patients with acute occlusion of the middle cerebral artery (MCA) or the distal internal carotid artery (ICA) and successful endovascular recanalization, pooled blood volume (PBV) was measured using flat-panel detector computed tomography (FPD CT).

Materials and Methods

Twenty patients with acute unilateral occlusion of the MCA or distal ACI without demarcated infarction, as proven by CT at admission, and successful Thrombolysis in cerebral infarction score (TICI 2b or 3) endovascular thrombectomy were included. Cerebral PBV maps were acquired from each patient immediately before endovascular thrombectomy. Twenty-four hours after recanalization, each patient underwent multislice CT to visualize final infarct volume. Extent of the areas of decreased PBV was compared with the final infarct volume proven by follow-up CT the next day.

Results

In 15 of 20 patients, areas of distinct PBV decrease corresponded to final infarct volume. In 5 patients, areas of decreased PBV overestimated final extension of ischemia probably due to inappropriate timing of data acquisition and misery perfusion.

Conclusion

PBV mapping using FPD CT is a promising tool to predict areas of irrecoverable brain parenchyma in acute thromboembolic stroke. Further validation is necessary before routine use for decision making for interventional thrombectomy.     

Comparison of perfusion computed tomography with diffusion-weighted magnetic resonance imaging in hyperacute ischemic stroke

OBJECTIVE: In this study, perfusion CT and diffusion-weighted magnetic resonance imaging (DWI) were compared as means of assessing the ischemic brain in hyperacute stroke. METHODS: Twenty patients with ischemic stroke underwent perfusion computed tomography (CT) and magnetic resonance imaging (MRI) studies <3 hours after stroke onset. Cerebral blood flow thresholds were used to delineate the ischemic lesion, penumbra, and infarct. Correlations between the volume of the hypoperfused areas, the abnormality volume in admission DWI and follow-up CT/MRI studies, and the clinical National Institutes of Health Stroke Scale (NIHSS) scores were performed. RESULTS: The volume of the ischemic (core and penumbra) lesion on admission perfusion CT was correlated with the volume of admission DWI abnormalities (r=0.89, P=0.001). The infarcted core tissue volume (on admission CT) correlated more strongly (r=0.77, P=0.0001) than the admission DWI abnormality volume (r=0.69, P=0.002) with the follow-up infarct volume on fluid-attenuated inversion recovery images. A correlation was demonstrated between infarct volume in perfusion CT and follow-up DWI abnormality volume (r=0.89, r=0.77, P=0.002). Significant correlations were found between ischemic and infarct region volumes in perfusion CT and NIHSS admission and follow-up scores (P < or = 0.01). CONCLUSIONS: Both imaging modalities provide a sufficient assessment of the hyperacute brain infarct, with significant correlation between them and the clinical condition at admission. Perfusion CT allows differentiation of the penumbra and infarct core region with significant predictive value of follow-up infarct volume and clinical outcome.     

Gd-DTPA-enhanced MR imaging of the brain in patients with meningitis: comparison with CT

Plain and Gd-DTPA-enhanced MR images of the brain were obtained in 18 consecutive patients with meningitis (eight with tuberculous, five with bacterial, three with viral, and two with fungal infections); the MR images were compared with CT scans. MR images were obtained on a 2.0-T superconducting unit with both T1- and T2-weighted pulse sequences before injection and with a T1-weighted sequence after injection of Gd-DTPA (0.1 mmol/kg) in all patients. In tuberculous meningitis, MR imaging depicted ischemia/infarct, hemorrhagic infarct of basal ganglia, meningeal enhancement at either basal cistern or convexity surface of brain, and associated small granulomas in a few more patients than CT did. In bacterial meningitis, primary foci of extracranial inflammation (i.e., mastoid, paranasal sinuses) and adjacent intracranial lesions including localized dural inflammation, subdural fluid collection, and/or brain parenchymal lesions were demonstrated much better on MR than on CT. Otherwise, MR images generally matched the CT scan. Although the plain MR images, both T1- and T2-weighted, were the most sensitive in delineating ischemia/infarct, hemorrhage, and edema, they were not as specific as Gd-DTPA-enhanced T1-weighted images and postcontrast CT scans in defining the active inflammatory process of the meninges and focal lesions precisely. We conclude that if Gd-DTPA is used, MR imaging appears to be superior to CT in the evaluation of patients with suspected meningitis. Precontrast MR is needed to delineate ischemia/infarct, edema, and subacute hemorrhage.     

Gd-DTPA-enhanced MR imaging of the brain in patients with meningitis: comparison with CT

Plain and Gd-DTPA-enhanced MR images of the brain were obtained in 18 consecutive patients with meningitis (eight with tuberculous, five with bacterial, three with viral, and two with fungal infections); the MR images were compared with CT scans. MR images were obtained on a 2.0-T superconducting unit with both T1- and T2-weighted pulse sequences before injection and with a T1-weighted sequence after injection of Gd-DTPA (0.1 mmol/kg) in all patients. In tuberculous meningitis, MR imaging depicted ischemia/infarct, hemorrhagic infarct of basal ganglia, meningeal enhancement at either basal cistern or convexity surface of brain, and associated small granulomas in a few more patients than CT did. In bacterial meningitis, primary foci of extracranial inflammation (i.e., mastoid, paranasal sinuses) and adjacent intracranial lesions including localized dural inflammation, subdural fluid collection, and/or brain parenchymal lesions were demonstrated much better on MR than on CT. Otherwise, MR images generally matched the CT scan. Although the plain MR images, both T1- and T2-weighted, were the most sensitive in delineating ischemia/infarct, hemorrhage, and edema, they were not as specific as Gd-DTPA-enhanced T1-weighted images and postcontrast CT scans in defining the active inflammatory process of the meninges and focal lesions precisely. We conclude that if Gd-DTPA is used, MR imaging appears to be superior to CT in the evaluation of patients with suspected meningitis. Precontrast MR is needed to delineate ischemia/infarct, edema, and subacute hemorrhage.     

Repeated computed tomography in lacunar infarcts of the brain

This prospective and consecutive study of 74 patients with completed stroke elucidates occurrence, localization and evolution of lacunar infarcts on repeated CT examinations. Twenty patients had large infarcts (diameter greater than 3 cm), 25 medium-sized infarcts (diameter greater than or equal to 1.5 cm - less than or equal to 3 cm), and 16 had lacunar infarcts (diameter less than 1.5 cm). In 13 patients no infarct was seen. The lacunar infarcts were characterized by delayed appearance on CT, low incidence of fog effect, and infrequent presence of contrast enhancement. In 9 of the 16 patients (56%) the lacunar infarct could be identified on the first CT, performed approximately 3 days after the stroke. In 2 patients the infarct was first revealed on the second (2 weeks post stroke) and in 5 on the third CT (6 months post stroke). The delayed appearance might be due to a partial volume effect. Early development of fog effect may also be considered. As contrast enhancement was observed in only 8 per cent of the patients with lacunar infarcts on CT, and in 70 per cent of the entire group of patients in our series with ischemic infarcts, contrast enhancement seemed to be a function of lesion size.     

Xe/CT cerebral blood flow evaluation of delayed symptomatic cerebral ischemia after subarachnoid hemorrhage.

PURPOSE: We examined the xenon/CT method of measuring cerebral blood flow in assessing the location, pattern of onset, and severity of delayed cerebral ischemia. PATIENTS AND METHODS: Fourteen patients with delayed neurologic deficits due to ischemia were selected from a group of 66 patients with subarachnoid hemorrhage. All blood flow studies were performed within 12 hours of deterioration and at regular intervals during medical management. RESULTS: In 10 of the 14 patients, noncontrast CT did not identify a cause for deterioration, whereas the blood flow study revealed diminished flow values. Location of blood flow reduction was variable. In five of the 14 patients, blood flow reduction was closely related anatomically to the vessel of aneurysm origin. In another three, blood flow reduction was anatomically remote to the vessel of origin. The remaining six experienced local and remote cerebral blood flow reduction. Six of 14 patients suffered sudden, devastating deterioration, refractory to therapy and associated with blood flow of 15 cc/100 g.min or less, resulting in local or widespread infarction. The remaining eight had less severe blood flow reduction and did not infarct those territories. CONCLUSIONS: Vasospasm can affect remote vessels as severely as local vessels and can affect remote vessels alone. Diminished cerebral blood flow correlated closely with clinical vasospasm in this group of patients. Xenon/CT cerebral blood flow studies can identify tissue at risk of infarction when CT is normal.     

Carotid artery occlusion and computed tomography

Summary Computed tomography (CT scanning) was carried out on 35 patients with proven occlusion of the carotid artery. There was a clear correlation of the clinical picture with the CT demonstration of cerebral infarct; 14 patients had no identifiable infarct. The findings were also correlated with angiographic data. The degree of cross or collateral filling of the middle cerebral artery on the affected side correlated better with the clinical features than with the CT data. Radioisotope studies were positive in only 50% of cases in which CT had shown infarction; this was related to the time interval between the onset of symptoms and scanning.The significance of these findings and their relationship to previous clinical necropsy data are discussed.     

Computed tomographic findings in fresh (2nd to 4th week) myocardial infarction

Thirty-seven patients, 2-4 weeks after transmural myocardial infarction, were investigated with ungated CT over a period of 120 min. after an i.v. contrast medium infusion + bolus injection of 0.6-0.9 iodine/kg body mass. Perfusion defect was found in 23/33 (70%) of technically adequate studies, delayed washout in 6/33 (18%) and local deformity of LV in 8/33 (24%). The mass of the perfusion defect assumed to represent the CT infarct size had a mean value of 10.2 g (3.5-25.8), infarct size estimated with CK-MB enzyme release method had a mean value of 14.1 g eq. (2.4-28.2). There was a r = 0.95 rectilinear correlation coefficient (p less than 0.001) between the CT and CK-MB method of infarct size estimation. Infarcts of size less than 6.0 g eq could not have been demonstrated with CT as a perfusion defect. Contrast enhancement of the infarct area was not a reliable feature of infarction.     

Acute myocardial infarction: contrast-enhanced multi-detector row CT in a porcine model

PURPOSE: To assess the role of contrast material-enhanced retrospectively electrocardiographically (ECG) gated multi-detector row computed tomography (CT) in the detection of acute myocardial infarction in a porcine model of total coronary occlusion. MATERIALS AND METHODS: Seven Yorkshire farm pigs were studied with contrast-enhanced retrospectively ECG-gated multi-detector row CT 3 hours after total occlusion of the distal left anterior descending artery (n = 5) or the second diagonal branch (n = 2). Reformatted short-axis end-systolic and end-diastolic CT data sets were assessed for myocardial perfusion deficits, coronary occlusion, and abnormal myocardial wall motion. Perfusion deficits were compared with microsphere-determined blood flow and triphenyltetrazolium chloride (TTC)-stained tissue samples for infarct assessment by using Bland-Altman analysis and analysis of variance. RESULTS: Myocardial perfusion deficits, occlusion of the left anterior descending artery or second diagonal branch, and akinesis of the infarcted segment were identified in all five animals that completed the study. One animal died, and one data set had nondiagnostic image quality. The CT end-diastolic (mean, 16.1% +/- 4.8 [SD]; range, 8.6%-22.2%) and end-systolic (mean, 17.0% +/- 6.4; range, 8.7%-26.8%) volume of perfusion deficit was similar to that of infarcted tissue at TTC staining (mean, 13.6% +/- 6.0; range, 7.8%-30.9%). Infarcted myocardium at CT demonstrated a 76.1% reduction in microsphere-determined blood flow and a significant reduction of myocardial CT attenuation compared with normal myocardium (P <.01). Myocardial wall motion analysis demonstrated absence of systolic wall thickening in infarcted myocardium. CONCLUSION: Multi-detector row CT with retrospective ECG gating permits the detection and further characterization of acute myocardial infarction in a porcine model of complete coronary occlusion.     

Technetium-99m-HMPAO SPECT in the evaluation of patients with a remote history of traumatic brain injury: a comparison with x-ray computed tomography.

The functional imaging modality has potential for demonstrating parenchymal abnormalities not detectable by traditional morphological imaging. Fifty-three patients with a remote history of traumatic brain injury (TBI) were studied with SPECT using 99mTc-hexamethylpropyleneamineoxime (HMPAO) and x-ray computed tomography (CT). Overall, 42 patients (80%) showed regional cerebral blood flow (rCBF) deficits by HMPAO SPECT, whereas 29 patients (55%) showed morphological abnormalities by CT. Out of 20 patients with minor head injury, 12 patients (60%) showed rCBF deficits and 5 patients (25%) showed CT abnormalities. Of 33 patients with major head injury, 30 patients (90%) showed rCBF deficits and 24 patients (72%) showed CT abnormalities. Thus, HMPAO SPECT was more sensitive than CT in detecting abnormalities in patients with a history of TBI, particularly in the minor head injury group. In the major head injury group, three patients showed localized cortical atrophy by CT and normal rCBF by HMPAO SPECT. In the evaluation of TBI patients, HMPAO SPECT is a useful technique to demonstrate regional brain dysfunction in the presence of morphological integrity as assessed by CT.     

A comparative study of magnetic resonance imaging and computed tomography in the evaluation of migraine

Seventy-four patients with classic migraine were examined by magnetic resonance imaging (MRI) and contrast enhanced head CT scanning. Patients chosen for the study ranged in age from 9 to 39 years with a mean age of 28 years. All had documented symptoms of classic migraine for over two years. Nineteen of the seventy-four patients (26%) had multiple foci of bright signal in the brain on T2 weighted MRI. None of these parenchymal abnormalities were detected on CT scans. Twenty-six patients (35%) had both MRI and CT demonstration of focal or generalized ventricular enlargement or sulcal prominence. These atrophic findings were shown equally well by both modalities. Ten patients (14%) with atrophic changes showed concomitant small bright foci of T2 signal abnormality. An additional migraine patient with homonymous hemianopsia had a large occipital lobe infarct which was seen as a region of bright T2 signal abnormality on MRI. Typical CT characteristics of an acute infarct were demonstrated.     

Improvement in visibility and detectability of early sign of acute stroke in nonenhanced CT images by using an adaptive partial smoothing filter

Detection of early infarct signs on nonenhanced CT is mandatory in patients with acute ischemic stroke. Loss of the gray-white matter interface at the lentiform nucleus or the insular ribbon has been an important early infarct sign, which affects decisions on thrombolytic therapy. However, its detection is difficult, since early infarct sign is of subtle hypoattenuation. To improve the detectability of early infarct sign, image processing that could reduce local noise while preserving edges is desirable. To examine this issue, we devised an adaptive partial smoothing filter (APSF). Since the APSF markedly improves visibility of the normal gray-white matter interface, loss of the gray-white matter interface due to hypoattenuation could be more easily detected. The APSF was applied to clinical CT images in hyperacute stroke patients. Our preliminary results showed that the visibility and detectability of early infarct signs was much improved. To validate the usefulness of the proposed method, two commonly used smoothing filters were also employed for comparison. The results demonstrated the superiority of the APSF. Our proposed APSF can improve the visibility of the gray-white matter interface, thereby enhancing the detectability of early infarct signs.