technetium-tc-99m-exametazime and Carotid-Stenosis

There is still controversy concerning which patients with asymptomatic carotid stenosis or symptomatic moderate stenosis are likely to benefit from carotid endarterectomy. The surgical candidates for carotid endarterectomy should have a high risk for stroke, but a low risk for operative complications. Therefore, new effective patient selection strategies, including haemodynamic testing, schemes of risk stratification and pre-operative cardiac testing, are under investigation. To improve haemodynamic assessment of patients with carotid artery stenosis, we evaluated a novel global cerebral blood flow (CBF) heterogeneity index at rest and after acetazolamide injection in patients undergoing carotid endarterectomy. CBF heterogeneity index was measured in 15 patients by using basal and acetazolamide enhanced 99mTc-HMPAO SPET both before and 1 month after surgery. CBF heterogeneity index was calculated as the coefficient of variation of a total of 44 cerebral regions representing mainly both ipsi- and contralateral grey matter. A high linear correlation was observed between CBF heterogeneity index and ipsilateral carotid stenosis degree (r=0.74, P=0.003). Before surgery, CBF heterogeneity index increased significantly after acetazolamide injection when compared to the basal condition (from 7.0+/-1.5 to 8.3+/-1.7%, P=0.008). This response disappeared after carotid endarterectomy. When compared to pure asymmetry of CBF (ipsi/contralateral CBF ratio), the CBF heterogeneity index seemed to reflect, more sensitively, the haemodynamic effects of carotid endarterectomy. The CBF heterogeneity index after acetazolamide injection is a sensitive marker of the haemodynamic consequences of carotid artery stenosis and its operative treatment.

Topics: Acetazolamide; Adolescent; Adult; Aged; Brain; Carotid Stenosis; Cerebrovascular Circulation; Child; Endarterectomy, Carotid; Female; Humans; Male; Middle Aged; Patient Selection; Prognosis; Radiopharmaceuticals; Reproducibility of Results; Risk Assessment; Sensitivity and Specificity; Severity of Illness Index; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Treatment Outcome

Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) were studied in 75 patients with cerebral infarction. All patients were alert with the symptoms of hemiparesis and/or aphasia, and were divided into two groups: 42 patients had occlusion or stenosis of >75% at the internal carotid artery or main trunk of middle cerebral artery; and 33 patients did not. Hemispheric mean CBF was measured by performing first-pass radionuclide angiography using 99mTc-hexamethylpropylene amine oxime. CVR was measured as the percentage change from the baseline mean CBF value after the administration of 500 mg acetazolamide. The CVR in both groups was significantly impaired (5.2+/-6.3%, P<0.001 and 7.7+/-6.1%, P<0.01, respectively) compared with normal controls (14.7+/-3.3%), although the mean CBF was not significantly reduced compared with age-matched controls. In the 12 patients with unilateral carotid occlusion, five patients with good collateral flow via the anterior communicating artery showed preserved CVR (11.0+/-7.8%), but those without did not (1.6+/-7.0%). CVR is impaired in alert patients with cerebral infarction, although the mean CBF is not reduced, and good collateral flow via the anterior communicating artery in patients with carotid occlusion may be a sign of well-preserved haemodynamic status.

Topics: Acetazolamide; Adult; Aged; Aged, 80 and over; Carbonic Anhydrase Inhibitors; Carotid Stenosis; Cerebral Infarction; Cerebrovascular Circulation; Chronic Disease; Female; Humans; Male; Middle Aged; Radiopharmaceuticals; Stroke; Technetium Tc 99m Exametazime; Ventriculography, First-Pass

Focal cerebral hypoperfusion is a common finding in uncomplicated hypertensives even in the absence of large vessel atherosclerosis, and neuropsychological deficits correlate with cerebral hypoperfusion in hypertensive patients with cerebral microangiopathy. We investigated the effects on cerebral perfusion of the dihydropiridine calcium antagonist lacidipine and of hydrochlorothiazide (HCTZ) in asymptomatic hypertensive patients with concomitant atherosclerosis of the carotid arteries. Fifteen essential hypertensives (including 13 males, aged 55-75 years) with at least one 30-60% stenosis of the internal carotid artery at echo-color Doppler examination were treated in a double-blind, randomized, parallel study with lacidipine (4-6 mg od) or HCTZ (25-50 mg od) for 3 months after a 4-week single-blind placebo period. Regional cerebral perfusion was assessed at baseline and at the end of the treatment period with HMPAO-SPECT. Relative perfusion of cortical and subcortical areas was calculated as the ratio between their tracer activity and that of the cerebellum. At baseline, mean relative perfusion (MRP) of the cortical and subcortical areas was similar in the stenotic and the contralateral side. Despite the fall in pressure, lacidipine increased MRP both in the cortical and in the subcortical areas, whereas HCTZ increased MRP only in the cortical areas. The mean change in local vascular resistance, adjusted for initial perfusion value, was -20 A.U. (arbitrary unit) with lacidipine and -12 A.U. with HCTZ (p < 0.001). These differential effects of antihypertensive drugs on subcortical perfusion may be of benefit in the long-term prevention of vascular dementia in hypertensive patients.

Topics: Aged; Antihypertensive Agents; Blood Pressure; Carotid Stenosis; Cerebrovascular Circulation; Dihydropyridines; Diuretics; Double-Blind Method; Female; Humans; Hydrochlorothiazide; Hypertension; Intracranial Arteriosclerosis; Male; Middle Aged; Sodium Chloride Symporter Inhibitors; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Vascular Resistance

Previous studies have shown areas of cerebral hypoperfusion in the frontal and parietal lobes of asymptomatic hypertensives, in the absence of extracranial carotid artery stenosis. The aims of the present study were: (a) to correlate the presence of focal cortical hypoperfusion with the presence of white matter lesions (WML), lacunae and extracranial carotid artery stenosis; and (b) to compare the effects on cerebral perfusion of the dihydropyridine calcium entry blocker lacidipine and of hydrochlorothiazide (HCTZ) in hypertensive patients with carotid artery stenosis. Forty-one patients (30 males, aged 40-75) with mild to moderate essential hypertension and with negative history for cerebrovascular diseases were investigated. Twenty-four had normal extracranial carotid arteries at echo-colourDoppler examination, while 17 had at least one 50-70% stenosis of the internal carotid artery (ICA). At computed tomography (CT) scan, five patients had one or more lacunar infarctions, four WML, three lacunar infarctions and WML, and 26 a normal CT scan. Three, with old cortical infarctions, were excluded from further analysis. The prevalence of lesions was significantly higher among the patients with carotid artery stenosis (44% vs. 29%; p < 0.05). Distribution of mean relative cortical perfusion (MRCP) of regions of interest [hexamethyl-propileneamine oxime-single photon emission tomography (SPET)] was not normal, with a negative skewness in patients with lacunae. MRCP was slightly but significantly reduced in patients with lacunae in comparison with hypertensives with normal CT scan and with WML. The asymmetry index of tracer distribution was significantly greater in the patients with lacunar infarctions and WML than in the hypertensive patients with normal CT scan, irrespective of the presence of internal carotid artery stenosis. Fifteen hypertensives (13 males, aged 55-75 years) with at least one moderate stenosis of ICA at duplex scanning were treated in a double-blind, randomised, parallel study with lacidipine (4-6 mg o.d.) or HCTZ (25-50 mg o.d.) for 3 months after a 4-week single-blind placebo period. At baseline, perfusion of the cortical and basal areas was similar in the stenotic and the contralateral side. Despite the fall in pressure, both treatments increased MRCP in the stenotic side and in the contralateral side. The lower the baseline perfusion, the larger its increase with treatment. The decrease of local cerebral vascular resistance was signific

Topics: Adult; Aged; Antihypertensive Agents; Carotid Stenosis; Cerebrovascular Circulation; Dihydropyridines; Diuretics; Double-Blind Method; Echoencephalography; Female; Humans; Hydrochlorothiazide; Hypertension; Male; Middle Aged; Radiopharmaceuticals; Sodium Chloride Symporter Inhibitors; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed

A patient with hepatic encephalopathy is described. An initial SPECT using Tc-99m HMPAO was performed to evaluate relative brain perfusion. The initial brain SPECT images revealed decreased perfusion in the left frontal temporal lobe region. A subsequent carotid Doppler study revealed left-sided carotid artery stenosis. After appropriate medical treatment for elevated NH3 levels and reversal of the patient's symptoms, repeat SPECT brain images showed a normal pattern of activity. The possible causes and significance for these image findings are discussed.

Topics: Adult; Brain; Carotid Stenosis; Female; Hepatic Encephalopathy; Humans; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Hyperperfusion (HP) is a rare but potentially devastating complication after carotid revascularization. This report describes the clinical efficacy of staged angioplasty (SAP) for carotid artery stenosis to prevent HP after carotid revascularization.. Eighteen of 143 patients with high-grade internal carotid artery stenosis scheduled for angioplasty were considered at high risk of postprocedure HP based on their severely impaired cerebral blood flow (CBF) and cerebral vasoreactivity, which were determined using single-photon emission computed tomography with acetazolamide. Nine of the high-risk patients were treated with carotid artery stenting and the other 9 were treated with SAP, which consisted of balloon angioplasty with undersized balloon catheters (Stage 1) followed by carotid artery stenting 1 to 2 months later (Stage 2).. In the regular carotid artery stenting group, 5 of 9 patients (56%) showed HP phenomenon on single-photon emission computed tomography just after stenting, and 1 patient (11%) developed status epilepticus owing to HP. In the SAP group, none of the 8 patients treated by SAP or the 1 patient who required stent placement during the first stage owing to a wall dissection developed postprocedure HP phenomenon or HP syndrome.. SAP decreased the HP phenomenon on single-photon emission computed tomography after performing these procedures in selected patients. Although additional intervention is needed, SAP is considered a relatively simple and effective method to avoid HP in patients at high risk of HP after carotid revascularization.

Topics: Acetazolamide; Aged; Angioplasty, Balloon; Blood Pressure; Carotid Stenosis; Cerebrovascular Disorders; Diuretics; Female; Humans; Intraoperative Care; Iofetamine; Magnetic Resonance Imaging; Male; Middle Aged; Platelet Aggregation Inhibitors; Postoperative Complications; Radiopharmaceuticals; Stents; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Treatment Outcome

To estimate possibilities for studies of cerebral perfusion with brain scintigraphy for revealing and an estimation of features of change brain perfusion at patients with a cardio-cerebral vascular pathology before and after carotid stenting (CAS).. 11 patients with established (after carotid angiography) stenosis of internal carotid artery and coronary artery disease have been studied with SPECT with analogue HMPAO teoxim--Tc99M after intravenous introduction 700 MBk up to and in 5 days and in the remote period after stenting. For analysis of results the program "Neurogam" have been used. Standartized perfusion maps have been created.. Before performing CAS various variants of the image cerebral perfusion maps have been obtained: from diffuse insignificant reduction in both hemispheres of a brain up to the regions hypoperfusion, characteristic for ischemic changes. Regions of hypoperfusion on the side opposite to a stenosis or occasion were revealed. SPECT, performed after cas on 5th day or after 2-3 months found increase of general brain perfusion, disappearance of symmetric both asymmetric regions hypoperfusion and reduction of a degree local hypoperfusion on the side of stenting.. Maps of brain perfusion before and after CAS adequately reflect microcirculation of a brain with local changes of perfusion. Use of perfusion parameters gives possibility to estimate changes of brain perfusion before and after CAS in patients with combined carotid and coronary pathology.

Topics: Brain; Brain Mapping; Carotid Artery, Internal; Carotid Stenosis; Coronary Disease; Female; Follow-Up Studies; Humans; Male; Middle Aged; Oximes; Perfusion Imaging; Radionuclide Imaging; Radiopharmaceuticals; Stents; Technetium Tc 99m Exametazime; Time Factors; Tomography, Emission-Computed, Single-Photon; Treatment Outcome

The aim of the present study was to assess the regional variation in cerebral perfusion, vasomotor reactivity (VMR) and the role of cerebral collaterals in patients with symptomatic internal carotid artery (ICA).. Seventeen functionally independent patients (60+/-9 years, mean+/-SD) with a unilateral symptomatic internal carotid artery occlusion and a <30% contralateral ICA stenosis were investigated. (99 m) Tc-hexamethyl propyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) was performed to study cerebral blood flow in rest and during a CO(2) challenge in the cerebellum, temporal lobe, occipital lobe, basal ganglia, frontal lobe and parietal lobe. Time of flight and phase contrast MRA were used to study collateral flow via circle of Willis.. In rest, cerebral perfusion on the side ipsilateral to the ICA occlusion was decreased compared with the contralateral side in the basal ganglia (p<0.05), frontal lobe (p<0.01) and parietal lobe (p<0.01). During a CO(2) challenge only the ipsilateral frontal lobe demonstrated a perfusion decrease compared with the contralateral frontal lobe (p<0.05). Furthermore, in patients without collateral flow via the anterior circle of Willis the perfusion of the ipsilateral frontal lobe was significantly decreased (p<0.01) during the CO(2) challenge and crossed cerebellar diaschisis with a decreased perfusion on the contralateral cerebellar hemisphere was detected (p<0.05). No cerebral blood flow (CBF) differences were found for present/absent collateral flow via the posterior communicating artery.. Regional assessment of cerebral perfusion and VMR with SPECT demonstrated the heterogeneity of cerebral hemodynamics and the importance of collateral flow via the anterior circle of Willis.

Topics: Aged; Carbon Dioxide; Carotid Artery, Internal; Carotid Stenosis; Cerebrovascular Circulation; Circle of Willis; Collateral Circulation; Data Interpretation, Statistical; Female; Functional Laterality; Humans; Magnetic Resonance Angiography; Male; Middle Aged; Radiopharmaceuticals; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

To assess the effect of unilateral carotid angioplasty and stenting (CAS) on cerebral perfusion asymmetry in patients with severe extracranial carotid stenosis by means of technetium Tc 99m hexamethyl-propyleneamine oxime brain single photon emission computed tomography ((99m)Tc-HMPAO SPECT).. Twenty-nine consecutive patients (22 men; median age 68 years, range 58-80; 13 symptomatic) undergoing unilateral CAS were included in the study. Brain perfusion was assessed by (99m)Tc-HMPAO brain SPECT prior to the procedure and postoperatively at 8 hours and at 2 to 4 months. The asymmetry index (AI), a measure of the interhemispheric asymmetry in perfusion, was calculated as [(counts in "healthy" hemisphere-counts in hemisphere with carotid stenosis)/counts in "healthy" hemisphere]x100.. The preoperative AI demonstrated a wide variation (mean -0.5%+/-8.4%, range -19.5% to 14.1%). There was no significant correlation between the degree of carotid stenosis and preoperative AI. The mean preoperative AI in the asymptomatic patients was lower than in the symptomatic group [-4.0%+/-8.5% (range -19.5% to 8.2%) versus 3.8%+/-6.4% (range -5.2% to 14.1%), p=0.01], suggesting reduced perfusion of the ipsilateral cerebral hemisphere compared to the contralateral side in symptomatic patients. AI variation did not improve after CAS; there was no difference in AI among the 3 SPECT studies (p=0.75). Preoperative AI correlated significantly with late AI (r=0.74, p<0.0001); however, there was no statistically significant correlation between immediate postoperative AI and either preoperative (r=0.24, p=0.217) or late (r=0.24, p=0.249) AI.. Asymmetry in cerebral perfusion in patients with severe extracranial carotid atherosclerosis does not correlate with the degree of carotid stenosis. Symptomatic patients demonstrate compromised perfusion of the ipsilateral hemisphere compared to asymptomatic patients. As judged by (99m)Tc-HMPAO SPECT scanning, cerebral perfusion patterns do not significantly change after CAS.

Topics: Aged; Aged, 80 and over; Amaurosis Fugax; Angiography, Digital Subtraction; Angioplasty, Balloon; Blood Vessel Prosthesis Implantation; Brain Ischemia; Carotid Stenosis; Cerebrovascular Circulation; Female; Follow-Up Studies; Humans; Ischemic Attack, Transient; Linear Models; Magnetic Resonance Imaging; Male; Middle Aged; Radiopharmaceuticals; Severity of Illness Index; Stents; Stroke; Technetium Tc 99m Exametazime; Time Factors; Tomography, Emission-Computed, Single-Photon; Treatment Outcome

Cerebral hyperperfusion syndrome has been increasingly reported as a complication of carotid angioplasty and stent placement. The aim of the present study was to determine significant predictors of hyperperfusion phenomenon after carotid angioplasty and stent placement.. We retrospectively reviewed 30 consecutive patients with unilateral severe carotid stenosis who underwent angioplasty and stent placement. Resting cerebral blood flow (CBF) and cerebral vasoreactivity (CVR) to acetazolamide challenge were quantitatively measured to evaluate cerebral hemodynamic reserve. Split-dose [(123)I] iodoamphetamine single photon emission CT (SPECT) was performed before and 7 days after carotid angioplasty and stent placement. Technetium-99m hexamethylpropyleneamine oxime (HMPAO) SPECT was performed immediately after the procedure.. Three patients had cerebral hyperperfusion phenomenon immediately after angioplasty and stent placement, as shown by HMPAO SPECT: One developed status epilepticus 2 weeks after the procedure. Significant predictors of hyperperfusion included patient age, pretreatment CVR, and pretreatment asymmetry index ([ipsilateral resting CBF/contralateral resting CBF] x 100). Variables determined not to be significant risk factors included pretreatment resting CBF value, degree of carotid stenosis, and interval from the onset of ischemic symptoms.. Significant predictors of hyperperfusion phenomenon after carotid angioplasty and stent placement included patient age, pretreatment CVR, and pretreatment asymmetry index. Pretreatment CBF measurements, including those obtained by quantifying CVR and performing SPECT immediately after the procedure may aid in identifying patients at risk and in initiating careful monitoring and control of blood pressure to prevent hyperperfusion syndrome.

Topics: Acetazolamide; Aged; Aged, 80 and over; Amphetamines; Angioplasty, Balloon; Carotid Stenosis; Cerebrovascular Circulation; Cerebrovascular Disorders; Female; Hemodynamics; Humans; Hyperemia; Iodine Radioisotopes; Male; Middle Aged; Predictive Value of Tests; Radiopharmaceuticals; Retrospective Studies; Stents; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Vasomotor System

Brain single photon emission computed tomographic (SPECT) images acquired after injecting Tc-99m-HMPAO into the internal carotid artery (ICA) during an intracarotid amobarbital procedure (IAP SPECT) provide anatomical information on the blood flow distribution from the ICA. In this study, probabilistic maps of the distribution of blood supply from the ICA were developed using the IAP SPECT images. Twenty-two sets of basal and IAP SPECT were collected from an existing database. IAP SPECT images were coregistered to basal SPECT images, and spatial normalization parameters used for basal SPECT images were reapplied to IAP SPECT for anatomical standardization. Pixel counts of IAP SPECT images were then normalized, and the probabilistic map of cerebral perfusion distribution (perfusion probabilistic map) for each hemisphere was determined by averaging the spatial/count-normalized IAP SPECT images. Population-based probabilistic maps representing the extent of ICA territory (extent probabilistic map) were also composed by averaging the binary images obtained by thresholding the spatially normalized IAP SPECT images. The probabilistic maps were used to quantify cerebral perfusion and reserve change after arterial bypass surgery in 10 patients with ICA stenosis. In the probabilistic maps, blood supply from the ICA was found to be most likely in the dorsolateral frontal lobe, the anterosuperior portion of the temporal lobe, and in the frontoparietal area. Of the subcortical regions, the striatum was found to be most likely to derive its blood supply from ICA. In patients with cerebral occlusive disease, improvements in basal perfusion and perfusion reserve in the bypass-grafted ICA territory were well identified and were increased by 6.2% and 4.6%, respectively, on average. The probabilistic maps developed in this study illustrate the perfusion distribution and extent of vascular territory for ICA and would be useful for objective evaluations of perfusion status in cerebrovascular disease.

Topics: Adolescent; Adult; Algorithms; Amobarbital; Anterior Temporal Lobectomy; Brain; Carotid Artery, Internal; Carotid Stenosis; Dominance, Cerebral; Epilepsy, Temporal Lobe; Female; Humans; Image Processing, Computer-Assisted; Imaging, Three-Dimensional; Magnetic Resonance Imaging; Male; Models, Statistical; Postoperative Complications; Reference Values; Regional Blood Flow; Retrospective Studies; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Dynamic imaging of the inflow of technetium-99m hexamethylpropylene amine oxime (HMPAO) to the brain has been proved to allow estimation of the hemispherical cerebral blood flow (CBF) using the Patlak plot. In this study, we compared the hemispherical CBF (in ml/min/100 g) of different patient groups. A total of 25 patients (comprising 13 with migraine and 12 scheduled for endarterectomy owing to angiographically confirmed severe stenosis of the internal carotid artery on at least one side) underwent baseline and acetazolamide 99mTc-HMPAO brain perfusion studies. In addition, acetazolamide 99mTc-HMPAO studies were performed in 12 healthy subjects (no baseline study was performed for ethical reasons.) Dynamic studies were acquired by means of a dual-detector gamma camera with a large field of view (HELIX, Elscint). Special difference images were created to make definition of the aortic arch and hemispherical brain regions easier and more reproducible. A semi-automatic method was developed to determine the transit time from the aorta to the brain, making the generation of the Patlak plot even more robust. The baseline CBF values did not significantly depend on the disease (P>0.1), whereas the CBF values obtained after acetazolamide provocation did do so (ANOVA, P<0.001). Patients suffering from migraine showed a significant increase in global CBF values after acetazolamide provocation (paired t test, P<0.05), but we could not find any effect of the provocation in patients awaiting carotid endarterectomy, indicating a lack of cerebrovascular reserve capacity. Comparison of the results of the acetazolamide study in patients and the control group revealed the CBF values to be significantly lower in patients with carotid stenosis (two-sample t-test, P<0.001), but not in those with migraine (P>0.1). In summary, using quantitative analysis of 99mTc-HMPAO brain studies we could objectively compare the CBF of patients suffering from different diseases. Especially the CBF values obtained after acetazolamide provocation permitted effective differentiation of disease states. The quantitative results may be of assistance in therapy planning, e.g. in selection of the correct operative technique.

Topics: Acetazolamide; Adult; Aged; Carotid Stenosis; Case-Control Studies; Cerebrovascular Circulation; Female; Humans; Male; Middle Aged; Migraine Disorders; Radiopharmaceuticals; Regional Blood Flow; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Quantitative, multislice dynamic susceptibility contrast-enhanced MRI perfusion measurements were used to determine the patterns of cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and normalized first moment of the tissue deltaR2-time curve (N) in 11 subjects with carotid artery occlusion or stenosis. MTT correlated with degree of carotid stenosis, whereas a range of alterations in CBF and CBV were found presumably reflecting variables degrees of collateral flow. There was no significant correlation between MRI and SPET flow perfusion measurements, with increasing disparity between the two techniques at higher inter-hemispheric flow ratios. The effect of obtaining the arterial input function (AIF) from the middle cerebral artery (MCA) ipsilateral or contralateral to the stenosis was determined. Despite the use of an AIF from the MCA, which is distal to the circle of Willis, and hence the major sources of collateral supply, there was still some extra dispersion of the contrast agent bolus due to differences in arrival time.

Topics: Aged; Blood Flow Velocity; Brain; Carotid Stenosis; Cerebrovascular Circulation; Contrast Media; Female; Gadolinium DTPA; Humans; Injections, Intravenous; Magnetic Resonance Imaging; Male; Radiopharmaceuticals; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

To increase the reliability of 99mTc-hexamethyl propyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) study in the evaluation of hemodynamic change with balloon test occlusion (BTO) of the internal carotid artery, we attempted to clarify the usefulness of additional monitoring of regional oxygen saturation of the brain (rSO2).. During BTO, rSO2 monitoring with transcranial near infrared spectroscopy was performed 17 times on 16 patients. Asymmetrical distribution of the tracer was classified visually as follows: group 1, little or no asymmetry, and group 2, moderate or severe asymmetry. Seven regions of interest (ROI) were defined in the middle cerebral artery area of each hemisphere, and the asymmetry index (AI)=200x(Cnon-Coccl)/(Cnon+Coccl)), where Cnon=mean counts on the nonoccluded side, and Coccl=mean counts on the occluded side were also calculated. Then, mean AI (MAI) was obtained from AI of 7 ROIs for each study.. Of the 17 procedures, 10 BTOs were in group 1 and 5 BTOs were in group 2. Two patients did not undergo SPECT study because of the immediate appearance of a neurological deficit with BTO; they were defined as group 3. The MAI in group 1 was 2. 6+/-3.3%, which was significantly smaller than the MAI in group 2 (25.6+/-5.0%, P<0.02). The DeltarSO2 (baseline rSO2-rSO2 during ICA occlusion) with BTO in group 1 was 1.5+/-1.4% (n=10), which was statistically smaller than that in group 2 (5.5+/-1.3%, n=4, P<0.05). The DeltarSO2 in group 3 was 9.0+/-0.0% (n=2). In group 1, however, rSO2 began to decline when the stump pressure fell to 45 mm Hg and always declined when the stump pressure fell below 40 mm Hg. Furthermore, in group 1, a significant correlation was observed between the DeltarSO2 and stump pressure (r=0.85, P<0.0001).. This preliminary study reveals that an obvious asymmetrical SPECT pattern always accompanies a profound decrease in rSO2 and that rSO2 parallels a severe reduction in stump pressure in cases exhibiting a symmetrical SPECT pattern. Thus, the cerebral oximetry sensitively reflects the cerebral oxygenation, and simultaneous measurements of rSO2 and stump pressure with 99mTc-HMPAO SPECT study apparently are useful in evaluating hemodynamic integrity with BTO.

Topics: Adolescent; Adult; Aged; Brain; Carotid Artery, Internal; Carotid Stenosis; Catheterization; Cerebrovascular Circulation; Female; Humans; Male; Middle Aged; Oxygen Consumption; Radiopharmaceuticals; Sensitivity and Specificity; Spectroscopy, Near-Infrared; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Quantitative studies of cerebral blood flow (CBF) combined with a vasodilatory challenge have defined a subgroup of patients with symptomatic carotid occlusion who have an increased risk for stroke. These are patients whose CBF paradoxically decreases in response to a vasodilatory challenge. Recent reports suggest that qualitative CBF techniques, such as single photon emission tomography with 99m-hexamethylpropyleneamine oxime, can also define the same high-risk subgroup. To determine whether qualitative measures of CBF are sufficient for predicting the risk of stroke, we converted our quantitative CBF data, obtained with xenon-enhanced computed tomography (Xe/CT), to qualitative ratios in a manner similar to that used with single photon emission tomography data.. We analyzed CBF values within the territory of the middle cerebral artery for 94 patients with symptomatic carotid occlusion. Values obtained using Xe/CT before and after the intravenous administration of 1 g of acetazolamide were used to derive an asymmetry index: (Coccl - Cnon)/Cavg x 100. The difference between the postacetazolamide asymmetry index and the baseline asymmetry index was used to classify the patients into groups according to CBF values. The threshold for abnormal qualitative CBF reactivity was defined as a percent change in the asymmetry index of less than -10%. Quantitative (Xe/CT) CBF was considered abnormal ("steal" response) when the response to acetazolamide (percent change) on the occluded side was a decrease of 5% or greater.. Of 34 patients whose cerebrovascular reserves were considered compromised based on qualitative criteria, 17 (50%) did not have a steal response as defined by quantitative Xe/CT CBF (i.e., false positive). Eleven of 62 (18%) who were not considered compromised by qualitative criteria had a steal response (i.e., false negative). Our data indicate that a qualitative approach has a 61% sensitivity and a 75% specificity for detecting patients with compromised reserves. Further, the positive predictive value of this method is only 50%. Therefore, the two methodologies do not predict the same patients as having compromised reserves.. Previous studies have shown that patients at high risk for stroke can be identified with quantitative CBF methods. This study shows that the important subgroup cannot be accurately defined with qualitative methodology. The implications of using the more reliable methodology are important for individual patient management and for designing clinical trials.

Topics: Acetazolamide; Carotid Stenosis; Cerebrovascular Circulation; Cerebrovascular Disorders; Collateral Circulation; False Negative Reactions; False Positive Reactions; Humans; Risk; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed; Vasodilation; Xenon

To determine whether the absolute value for the stump pressure might be a useful index of symmetrical cerebral blood flow (CBF), and to examine correlations with the stump pressure ratio (initial mean stump pressure/preocclusion mean arterial pressure), fifty candidates for ICA injury or permanent occlusion were evaluated preoperatively. Each was continuously monitored for mean stump pressure and arterial pressure before, during (for a total of 20 min), and after balloon test occlusion. During the occlusion, CBF was measured by 99 m Tc-hexamethyl-propyleneamine oxime (99 m Tc-HMPAO) single photon emission computed tomography (SPECT). The stump pressure and the stump pressure ratio were then compared with the results of 99 m Tc-HMPAO SPECT. Patients who failed to tolerate even brief periods of carotid occlusion and showed asymmetric decreases in CBF on SPECT were divided into high and moderate risk groups. Those with no significant changes in CBF on the occluded site formed the minimum risk group. Mean stump pressure was over 50 mmHg in 10 of a total of 25 patients in the high and moderate risk groups, and below 50 mmHg in 5 of the 25 patients in the minimum risk group. The stump pressure ratio did not exceed 56% in any but two patients in the high and moderate risk groups, and values were at least 60% in all patients of the minimum risk group. Decrease of CBF in two moderate risk group cases was localized in the posterior circulation. Difference in symmetrical CBF between the stump pressure ratio vs. the absolute value of mean stump pressure were statistically significant (p < 0.01, Fisher's Exact Test). Maintenance of a stump pressure ratio of 60% or more during test occlusion may be a more useful index for a good collateral circulation than any absolute value for mean stump pressure.

Topics: Blood Pressure; Brain Neoplasms; Carotid Artery, Internal; Carotid Stenosis; Catheterization; Cerebrovascular Circulation; Electroencephalography; Granuloma; Humans; Intracranial Aneurysm; Meningioma; Paraganglioma; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Treatment Outcome; Vascular Surgical Procedures

The importance of MR imaging in carotid artery disease is unclear. We evaluated the sensitivity and specificity of the high signal intensity changes on MR images for diagnosis of hemodynamically compromised unilateral internal carotid artery disease.. We evaluated the association of high signal intensities on T2-weighted MR images with changes in cerebral perfusion reserve measured using 99mTc-hexamethylpropyleneamine oxime single-photon emission CT and acetazolamide in 23 patients.. Eleven patients had a type I response (normal flow and normal perfusion reserve), 8 patients had a type II response (normal flow and decreased perfusion reserve), and 4 patients had a type III response (decreased flow and decreased perfusion reserve). High signal intensities in the centrum semiovale (11/12) and/or posterior periventricular white matter (6/12) were frequently seen in the hemodynamically compromised groups. Extensive high signal intensities were associated with severely impaired cerebral circulation. MR imaging had high sensitivity (0.92) and specificity (1.0) in predicting hemodynamically compromised patients when we used the presence of T2 high intensity in the centrum semiovale as a criterion.. The centrum semiovale T2 hyperintensities lateralized to the side of carotid occlusion are specific and sensitive for the presence and severity of hemodynamic compromise from carotid occlusive disease.

Topics: Acetazolamide; Aged; Brain Ischemia; Carotid Stenosis; Cerebrovascular Circulation; Female; Humans; Intracranial Embolism and Thrombosis; Ischemic Attack, Transient; Magnetic Resonance Imaging; Male; Middle Aged; Organotechnetium Compounds; Oximes; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

The aim of our work was to study the state of regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) in patients with different degree of carotid stenosis after CE. Thirty six patients with carotid stenosis aged 46-65 years (mean age 55 years) were studied. In all the patients before and one month after carotid endarterectomy (CE) single photon emission computed tomography (SPECT) with 99mTc-hexamethylpropylene amine oxime (99mTc-HMPAO, Ceretec, Amersham) and SPECT with labelled in vivo 99mTc-red blood cells (99mTc-RBC) were carried out. According to the results of scintigraphic studies the regional cerebral blood flow (rCBF, ml/min/100g), the volume of hypoperfusion (Vhypoperf., sm3), the stroke volume (SV, sm3), the interhemispheric ratio of rCBF (IRrCBF) and the regional cerebral blood volume (rCBV, ml/100g) were calculated. CE leads to the bilateral increase of cerebral perfusion especially at the side of more expressed damage putting away interhemisphere asymmetry of rCBF. After CE the regression of SV and Vhypoperf were revealed. In asymptomatic disease patients with monolateral stenosis of carotid arteries rCBF reaches normal values and regions of hypoperfusion are not revealed. Surgical recanalization of carotid arteries causes expressed changes of scintigraphic parameters of rCBV: normalization of initially increased values of rCBV in patients with asymptomatic development of stenosed atherosclerosis of carotid arteries and subsequent increase of rCBV in comparison with preoperative level in patients who underwent acute stroke with neurological deficit and patients with poor clinical signs and multiple damage of both internal carotid arteries.

Topics: Acute Disease; Aged; Arteriosclerosis; Blood Volume; Brain; Brain Ischemia; Carotid Artery, Internal; Carotid Stenosis; Cerebrovascular Circulation; Cerebrovascular Disorders; Endarterectomy, Carotid; Erythrocytes; Female; Follow-Up Studies; Humans; Male; Middle Aged; Organotechnetium Compounds; Oximes; Radiopharmaceuticals; Stroke Volume; Technetium; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

The purpose of this study was to determine if one could objectively and preoperatively predict the safety of permanent occlusion of an internal carotid artery with 99mTc-HMPAO brain SPECT.. Twenty-four patients underwent balloon test occlusion of the internal carotid arteries because of neck and skull base tumors. We assessed the uptake of both middle cerebral artery territories before and during balloon test occlusion with 99mTc-HMPAO brain SPECT using the semiquantitative analysis. The results were compared with other factors, including neurologic examination, arterial stump pressure and electroencephalogram.. Nineteen patients experienced no neurological deterioration or any problem during balloon test occlusion. The comparative uptake of their middle cerebral artery territories was 95%-101% of the pre-balloon test occlusion state. The remaining five patients showed severe neurologic symptoms, such as transient hemiplegia and unconsciousness. The comparative uptake of their middle cerebral artery territories was 77%-85% of the pre-balloon test occlusion state and was well matched with other factors.. Technetium-99m-HMPAO brain SPECT before and during balloon test occlusion seems to be a simple and objective method for predicting permanent neurologic deficits when the comparative uptake of middle cerebral artery territories during balloon test occlusion is less than 85% of that before balloon test occlusion.

Topics: Adolescent; Adult; Brain; Carotid Artery, Internal; Carotid Stenosis; Catheterization; Central Nervous System Diseases; Cerebrovascular Circulation; Collateral Circulation; Feasibility Studies; Female; Head and Neck Neoplasms; Humans; Male; Organotechnetium Compounds; Oximes; Predictive Value of Tests; Risk Factors; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

We evaluated the posterior circulation in patients with moyamoya disease by SPECT and MRI.. Six patients with idiopathic moyamoya disease were studied by SPECT, MRI and angiography. Patients received an injection of 555-740 MBq of 99mTc-HMPAO, after which SPECT images were taken. The cerebral-to-cerebellar activity ratio in five cerebral regions was calculated to assess the regional cerebral blood flow (rCBF). The SPECT and MRI findings were then compared with angiographic.. Of the 12 posterior cerebral arteries (PCAs) in the six patients studied, seven PCAs (58%) in five patients had a stenotic or occluded lesion. Furthermore, rCBF in all five regions significantly decreased as the degree of steno-occlusive lesions of the PCA progressed. No significant correlation, however, was found between the steno-occlusive lesions of the internal carotid artery bifurcation and the rCBF. The rCBF significantly decreased in the absence of leptomeningeal collateral vessels from the PCA to the anterior circulation. On the basis of the MR images, the frequency of cerebral infractions significantly increased in patients with steno-occulasive PCA lesions.. The rCBF in moyamoya disease decreases proportionally with the degree of steno-occlusive lesions of the PCA. The steno-occlusive PCA lesions decrease the number of leptomeningeal collateral vessels to the anterior circulation, thereby causing severe cerebral ischemia that is likely to result in infractions.

Topics: Adolescent; Adult; Carotid Artery, Internal; Carotid Stenosis; Cerebral Angiography; Cerebral Infarction; Cerebrovascular Circulation; Child; Collateral Circulation; Constriction, Pathologic; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Moyamoya Disease; Organotechnetium Compounds; Oximes; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Acetazolamide is commonly used with single-photon CT to assess the cerebrovascular reserve in patients with internal carotid artery stenosis or occlusion. In this study we wanted to evaluate the effects of adenosine, a well-known vasodilatatory compound with a short biological half-life, on brain circulation in humans and compare the results with those of acetazolamide.. Acetazolamide (1 g) and adenosine (140 micrograms/kg per minute) were injected intravenously on different days in 6 normal subjects and 6 patients: 4 with unilateral stenosis, 1 with bilateral stenosis, and 1 with complete occlusion of the internal carotid artery. Changes in regional cerebral blood flow relative to that of the cerebellum (cortico/cerebellar ratios) from resting conditions were evaluated by 99mTc-hexamethylpropyleneamine oxime and single-photon emission CT.. The measured blood flow ratios increased significantly in the normal group 20 minutes after acetazolamide injection in several cortical and subcortical regions, as well as at the 4th minute of a 6-minute adenosine infusion. Regional cerebral blood flow ratio values were higher after adenosine than after acetazolamide in both cortical (frontal and parietal) and subcortical (thalamus and basal ganglia) regions. In 4 of the 6 patients the side-to-side asymmetry increased from the basal resting condition after the injection of acetazolamide and even more so after the injection of adenosine.. Adenosine infusion causes vasodilation of cerebral arteries and can be used for the investigation of cerebrovascular perfusion capacity in patients with carotid occlusive disease. One advantage in the use of adenosine over acetazolamide is the possibility of interrupting the test with reversal of clinical symptoms or patient discomfort within a few minutes.

Topics: Acetazolamide; Adenosine; Aged; Arterial Occlusive Diseases; Basal Ganglia; Carotid Artery, Internal; Carotid Stenosis; Cerebellum; Cerebral Arteries; Cerebral Cortex; Cerebrovascular Circulation; Female; Frontal Lobe; Humans; Injections, Intravenous; Male; Middle Aged; Organotechnetium Compounds; Oximes; Parietal Lobe; Technetium Tc 99m Exametazime; Thalamus; Tomography, Emission-Computed, Single-Photon; Vasodilation

For semiquantification of SPECT studies we tried to calculate cerebral 99mTc-HMPAO uptake related to injected dose and estimated brain volume. The method was applied to SPECT investigations of 27 patients who had at least one ischaemic attack and a confirmed 80-100% stenosis of the corresponding internal carotid artery (ICA). Vascular reactivity was tested by parenteral administration of acetazolamide (AZ). Increase in HMPAO uptake after AZ was evident in both hemispheres, although the increase (AZ effect) was significantly lower in the affected hemisphere (+24% versus +28%). No interhemispheric uptake differences were seen in patients with largely normal SPECT studies, although local asymmetries in HMPAO deposition were visible. Patients with low density lesions on CT and with a well-demarcated lesion in the same location on SPECT revealed interhemispheric uptake differences, with lower uptake on the affected side. This was not due solely to alterations in the lesion, but also to reduced HMPAO uptake and AZ effect in the surrounding area. The AZ effect showed no correlation with angiographic findings, indicating no major haemodynamic influence of the ICA stenosis on cerebral hemisphere perfusion. Calculated cerebral HMPAO uptake changes after AZ administration were in good accordance with absolute cerebral blood flow measurements, and made interindividual comparisons possible. However, as changes in the area around an infarct or local reduction in vascular reserve may not be reproduced adequately by uptake calculations, visual inspection is still necessary.

Topics: Acetazolamide; Adult; Aged; Brain; Brain Mapping; Carotid Artery, Internal; Carotid Stenosis; Cerebral Cortex; Cerebral Infarction; Dominance, Cerebral; Female; Humans; Ischemic Attack, Transient; Male; Middle Aged; Organotechnetium Compounds; Oximes; Regional Blood Flow; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

In this study we aimed to work out a quantitative prognostic index for preoperative assessment of brain technetium-99m hexamethylpropylene amine oxime (HMPAO) single-photon emission tomography (SPET) in patients referred for urgent carotid endarterectomy due to acute obstructive disease of the internal carotid artery (ICA) and neurological deficit. To this end we compared data from preoperative SPET studies with the postinterventional changes in neurological status in 20 patients (17 males, three females; mean age 53 years, SD 4 years) with acute ischaemic cerebral disorders induced by obstruction of the ICA. Carotid obstruction was diagnosed by ultrasound B-mode study. All patients underwent urgent carotid endarterectomy from the ICA. Patients were divided into two groups in accordance with the results of postoperative follow-up: group A comprised patients with significant (more than 3 points) postoperative improvement in neurological condition as quantified by the Canadian Neurological Scale (11 patients); group B consisted of patients with minimal improvement or deterioration (nine, three of whom died). All patients were studied preoperatively by 99mTc-HMPAO SPET. The volume of nonperfused tissue (VS, cm3) was quantified using the Mountz technique. Hypoperfused volume (Vhypoperf, cm3) in the affected hemisphere was calculated as the total volume of voxels with 99mTc-HMPAO uptake < 90% of the contralateral symmetric voxels. Discriminant prognostic function was calculated by discriminant analysis as: PF = 0.072 x VS + 29.46x(VS/Vhypoperf). Patients with preoperative PF values < 8.20 demonstrated postoperative improvement in neurological status, while the group with PF > 8.90 comprised patients who demonstrated minimal improvement or deterioration. PF values in the range 8.20-8.90 carried an indefinite prognosis. We conclude that the preoperative 99mTc-HMPAO SPET can be used for the selection of patients in whom improvement in neurological status may be expected after urgent surgical correction of acute extracranial obstruction of the ICA.

Topics: Brain; Brain Ischemia; Carotid Artery, Internal; Carotid Stenosis; Emergencies; Endarterectomy, Carotid; Female; Humans; Male; Middle Aged; Organotechnetium Compounds; Oximes; Prognosis; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Ultrasonography

The aim of the study was to depict regional cerebral blood flow (rCBF) during carotid cross clamping using 99mTechnetium-hexamethylpropylene amine oxime (TcHMPAO). This tracer rapidly passes the blood-brain barrier and is retained for hours in the brain tissue. Injecting TcHMPAO during surgery and performing single photon emission computer tomography (SPECT) scanning shortly after the operation thereby pictures rCBF at the time of injection.. Ongoing prospective study.. Departments of Vascular Surgery, Neurology and Anaesthesiology, University Hospital, Rigshospitalet, Copenhagen, Denmark.. 15 patients who during a period of 4 months underwent carotid endarterectomy.. Prior to surgery rCBF was determined using 133Xe and SPECT. Intraoperatively stump pressure was measured and a bolus of TcHMPAO was injected for later SPECT measurement.. We found a significant correlation between stump pressure and enhancement of side-to-side asymmetry in rCBF due to carotid cross clamping. Pronounced variations were seen in which regions were deprived of perfusion during clamping.. TcHMPAO allows tomographic assessment of CBF during carotid surgery. This method may serve as a reference tool in future research on intraoperative cerebral haemodynamics.

Topics: Aged; Brain; Brain Ischemia; Carotid Stenosis; Endarterectomy, Carotid; Female; Hemodynamics; Humans; Intraoperative Complications; Male; Middle Aged; Organotechnetium Compounds; Oximes; Prospective Studies; Regional Blood Flow; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Fifteen patients with symptoms of cerebral ischaemia and angiographically confirmed unilateral stenoses or occlusions of the extracranial internal carotid artery (ICA) and 20 controls were studied by a 2 MHz transcranial Doppler (TCD) at rest and after stimulation with 1 g acetazolamide i.v., a cerebral vasodilator. In addition, the patients underwent 99mTc-HM-PAO-Spect measurement of regional cerebral blood flow (rCBF) at rest and after stimulation with 1 g acetazolamide. In 10 patients with ICA stenoses greater than 80% or occlusions, time-mean velocity (Vmean) increase and pulsatility index (PI) decrease in the postobstructive middle cerebral artery (MCA) as well as the increase of the ipsilateral rCBF were reduced in comparison with the contralateral side. The remaining 5 patients showed a normal Vmean increase and PI decrease in TCD.

Topics: Acetazolamide; Brain Ischemia; Carotid Artery, Internal; Carotid Stenosis; Echoencephalography; Humans; Organotechnetium Compounds; Oximes; Reference Values; Technetium Tc 99m Exametazime; Tomography, Emission-Computed