technetium-tc-99m-exametazime and Stroke

Trapeziometacarpal osteoarthritis is associated with more pain and restrictions than other hand osteoarthritis due to the functional importance of the thumb. While the effectiveness of surgical and pharmacological interventions has been widely examined, there is a lack of specific evidence about conservative non-pharmacological trapeziometacarpal osteoarthritis therapies. The objective of this systematic review was to provide evidence-based knowledge on the effectiveness of physiotherapy and occupational therapy on pain, function and quality of life.. A literature search of Medline, CINAHL, PEDro, OTseeker, EMB Dare Cochrane Database of Systematic Reviews and Cochrane CENTRAL was performed. Randomized and quasi-randomized controlled trials and corresponding systematic reviews, observational studies, pragmatic studies and case-control studies were included. The risk of bias was assessed.. Physical and occupational therapy-related interventions, especially multimodal interventions, seem to be effective to treat pain in patients with trapeziometacarpal osteoarthritis. Pre-fabricated neoprene splints and custom-made thermoplastic splints may reduce pain equally. Single interventions seem not to be effective. Significant evidence for effectiveness on function and quality of life could not be found.. The sole Na. The SUV. Genetic variants of

Topics: AC133 Antigen; Acenaphthenes; Acer; Acrosome Reaction; Adult; Agaricales; Aged; Aged, 80 and over; Animals; Animals, Zoo; Anti-Bacterial Agents; Anticoagulants; Antifungal Agents; Antimanic Agents; Antioxidants; Aortic Valve; Area Under Curve; ATP Binding Cassette Transporter, Subfamily G, Member 2; Bacillus; Bacterial Toxins; Bacterial Typing Techniques; Base Composition; Beauveria; Binge Drinking; Biomarkers; Bipolar Disorder; Blood Coagulation; Blotting, Western; Brachytherapy; Calcium Channels, L-Type; Carcinoma, Non-Small-Cell Lung; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cell Transformation, Neoplastic; Cell Wall; Cells, Cultured; Ceramics; Chi-Square Distribution; China; Chlorophyll; Chlorophyta; Chloroplasts; Cholesterol, HDL; Chromatography, High Pressure Liquid; Chromobacterium; Clostridium perfringens; Clozapine; Constriction, Pathologic; Coronary Artery Bypass; Corticotropin-Releasing Hormone; Cross-Sectional Studies; Cytochrome P-450 CYP2C9; Dental Porcelain; Dental Restoration Failure; Dental Stress Analysis; Designer Drugs; Diaminopimelic Acid; DNA Fingerprinting; DNA, Bacterial; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Drug Dosage Calculations; Drug Evaluation, Preclinical; Drug Resistance, Bacterial; Elasticity Imaging Techniques; Epsilonproteobacteria; Equipment Design; Ericaceae; Excitatory Amino Acid Antagonists; False Negative Reactions; Fatty Acids; Female; Food Analysis; Fresh Water; Gene Expression Regulation, Neoplastic; Glutathione; Graft Occlusion, Vascular; Heart Valve Prosthesis Implantation; Heart Ventricles; HEK293 Cells; Hemolymph; Humans; Hyaluronan Receptors; Hydrogen Peroxide; Hydrothermal Vents; Indoles; Inflammation Mediators; Inhibitory Concentration 50; Insecta; International Normalized Ratio; Isotope Labeling; Itraconazole; Kidney; Kinetics; Kruppel-Like Factor 4; Kruppel-Like Transcription Factors; Lamotrigine; Lanthanoid Series Elements; Limit of Detection; Linear Models; Lipid Peroxidation; Liver; Liver Cirrhosis; Logistic Models; Lung Neoplasms; Lymph Node Excision; Lymphatic Metastasis; Male; Malondialdehyde; Mediastinum; Metronidazole; Mice; Mice, Nude; Mice, Transgenic; Microbial Sensitivity Tests; Microscopy, Fluorescence; Middle Aged; Monocytes; Monomeric GTP-Binding Proteins; Multivariate Analysis; Myocytes, Cardiac; Neoplasm Staging; Neoplastic Stem Cells; Neural Pathways; Nitrates; Nucleic Acid Hybridization; Octamer Transcription Factor-3; Odds Ratio; Oxidation-Reduction; Oxidative Stress; Peptidoglycan; Phantoms, Imaging; Pharmacogenetics; Pharmacogenomic Variants; Phenotype; Phospholipids; Photolysis; Photosynthesis; Phylogeny; Plant Extracts; Polychaeta; Polymerase Chain Reaction; Polymorphism, Single Nucleotide; Positron Emission Tomography Computed Tomography; Predictive Value of Tests; Preoperative Care; Prostatic Neoplasms; Pseudomonas aeruginosa; Pyrimidines; Pyrroles; Quorum Sensing; Radiology, Interventional; Radiopharmaceuticals; Radiotherapy Dosage; Rats; Rats, Sprague-Dawley; Receptors, Corticotropin-Releasing Hormone; Reference Values; Regression Analysis; Retrospective Studies; Reverse Transcriptase Polymerase Chain Reaction; Rhizosphere; Risk Factors; RNA, Ribosomal, 16S; ROC Curve; Rutin; Saphenous Vein; Seawater; Selenium; Semen Preservation; Sensitivity and Specificity; Septal Nuclei; Sequence Analysis, DNA; Serum Albumin; Serum Albumin, Human; Shear Strength; Sodium Pertechnetate Tc 99m; Sodium-Hydrogen Exchangers; Soil Microbiology; SOXB1 Transcription Factors; Spain; Species Specificity; Sperm Motility; Spermatozoa; Spheroids, Cellular; Spores, Fungal; Stroke; Superoxide Dismutase; Swine; Tandem Mass Spectrometry; Technetium Compounds; Technetium Tc 99m Exametazime; Technetium Tc 99m Sestamibi; Temperature; Thiosulfates; Thrombosis; Thyroid Neoplasms; Transducers; Transfection; Transplantation, Heterologous; Treatment Outcome; Triazines; Tumor Burden; Urocortins; Uterine Cervical Neoplasms; Vacuoles; Valproic Acid; Ventral Tegmental Area; Vitamin K 2; Vitamin K Epoxide Reductases; Warfarin; Water Microbiology; Young Adult

Topics: Adult; Aged; Atrophy; Brain; Cerebral Hemorrhage; Electroencephalography; Epilepsy; Humans; Magnetic Resonance Imaging; Middle Aged; Prospective Studies; Radiography; Radiopharmaceuticals; Retrospective Studies; Severity of Illness Index; Stroke; Technetium Tc 99m Exametazime; Time Factors

Tadalafil is a potent and selective phosphodiesterase type 5 inhibitor that provides effective treatment for erectile dysfunction (ED). The purpose of this study was to explore the effect of a single on-demand dose of tadalafil compared to low-dose continuous administration on regional cerebral blood flow (rCBF), in patients after stroke.. Thirty consecutive male patients (mean age 58.3 ± 7.9 years) with ED and a history of stroke were included in the study. The baseline single-photon emission computed tomography (SPECT) study was performed 15 min after iv injection of 740 MBq Tc-99m-HMPAO (Ceretec; GE Healthcare Ltd. Chalfont St. Giles, UK). Fifteen randomized patients received a single dose of 20 mg tadalafil in the morning, and a second SPECT study was performed 6 h later. Fifteen other patients received 5 mg of tadalafil each morning for seven consecutive days, and the second SPECT study was performed 6 h after the last dose. The imaging data were evaluated using SPM software (Wellcome Department of Cognitive Neurology, University College, London).. Associations between any of the risk factors/comorbidities and the perfusion changes were not detected. All patients showed areas of reduced relative rCBF in the affected hemisphere after tadalafil administration compared to baseline (P < 0.001). No significant difference was found between patients on 5 mg tadalafil and 20 mg dose.. Tadalafil administration after cerebral stroke may be associated with diminished blood flow to areas adjacent to the stroke. The alterations in perfusion suggest a need for caution in prescribing tadalafil to patients with a history of stroke, especially with continuous administration that may impose constant stress on the cerebral circulation.

Topics: Adult; Aged; Carbolines; Cerebrovascular Circulation; Erectile Dysfunction; Female; Humans; Male; Middle Aged; Radiopharmaceuticals; Stroke; Tadalafil; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Vasodilator Agents

This study evaluated blood flow and metabolite changes in cerebral diaschisis from internal capsule region infarction using regional cerebral blood flow (rCBF) single-photon emission computed tomography (SPECT) and 1H magnetic resonance spectroscopic imaging (MRSI). We hypothesized that complementary measures of diaschisis effects in white matter (characterized by 1H MRSI) and gray matter (characterized by changes in rCBF) can be measured and exhibit parallel changes.. Five stroke patients and 16 normal controls underwent Tc-99m hexamethylpropyleneamine-oxime brain SPECT and 1H MRSI at 4.1 T. The metabolites N-acetyl aspartate (NAA) and creatine (Cr) were measured using 1H MRSI. The tissue content was expressed as the percent of gray or white matter in each MRSI voxel to allow comparison of the differential effects of diaschisis in gray and white matter tissue types. The blood flow and metabolite changes were evaluated at superior cerebral regions distant from the stroke to allow a measure of diaschisis relatively unconfounded by their expected changes in the infarction region.. The rCBF SPECT data in stroke patients showed a perfusion defect, with size ranging from 1.23 cc to 10.23 cc, in the region of cortical diaschisis. 1H MRSI showed increased Cr/NAA ratios in regions of white matter diaschisis. There was a tendency for larger rCBF defect size to be associated with greater increases in Cr/NAA values in the same diaschitic cerebral hemisphere, ipsilateral to the infarction.. Diaschisis ipsilateral to stroke in white matter can be characterized by 1H MRSI, and diaschisis ipsilateral to stroke in cortical gray matter regions can be characterized by changes in rCBF. The tendency for greater reductions in cortical rCBF values to be associated with increased Cr/NAA values in the same diaschitic cerebral hemisphere implies that a relationship exists between rCBF reductions in gray matter and abnormal changes in white matter subservient to it.

Topics: Adult; Aged; Aspartic Acid; Blood Flow Velocity; Brain; Cerebral Infarction; Cerebrovascular Circulation; Creatine; Female; Humans; Internal Capsule; Magnetic Resonance Spectroscopy; Male; Middle Aged; Paresis; Predictive Value of Tests; Reference Values; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

The purpose of this study was to investigate the differences between technetium-99m ethyl cysteinate dimer (99mTc-ECD) and technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) uptake in the same brains by means of statistical parametric mapping (SPM) analysis. We examined 20 patients (9 male, 11 female, mean age 62+/-12 years) using 99mTc-ECD and 99mTc-HMPAO single-photon emission tomography (SPET) and magnetic resonance imaging (MRI) of the brain less than 7 days after onset of stroke. MRI showed no cortical infarctions. Infarctions in the pons (6 patients) and medulla (1), ischaemic periventricular white matter lesions (13) and lacunar infarction (7) were found on MRI. Split-dose and sequential SPET techniques were used for 99mTc-ECD and 99mTc-HMPAO brain SPET, without repositioning of the patient. All of the SPET images were spatially transformed to standard space, smoothed and globally normalized. The differences between the 99mTc-ECD and 99mTc-HMPAO SPET images were statistically analysed using statistical parametric mapping (SPM) 96 software. The difference between two groups was considered significant at a threshold of uncorrected P values less than 0.01. Visual analysis showed no hypoperfused areas on either 99mTc-ECD or 99mTc-HMPAO SPET images. SPM analysis revealed significantly different uptake of 99mTc-ECD and 99mTc-HMPAO in the same brains. On the 99mTc-ECD SPET images, relatively higher uptake was observed in the frontal, parietal and occipital lobes, in the left superior temporal lobe and in the superior region of the cerebellum. On the 99mTc-HMPAO SPET images, relatively higher uptake was observed in the medial temporal lobes, thalami, periventricular white matter and brain stem. These differences in uptake of the two tracers in the same brains on SPM analysis suggest that interpretation of cerebral perfusion is possible using SPET with 99mTc-ECD and 99mTc-HMPAO.

Topics: Adult; Aged; Brain; Brain Mapping; Cysteine; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Organotechnetium Compounds; Radionuclide Imaging; Radiopharmaceuticals; Stroke; Technetium Tc 99m Exametazime

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

Stroke, as the second most common cause of death, imposes a great financial burden on both the individual and society. Mesenchymal stem cells from rodents have demonstrated efficacy in experimental animal models of stroke due to enhanced neurological recovery. Since FGF1 (fibroblast growth factor 1) displays neuroprotective properties, for the first time, we investigated the effect of acute intravenous administration of FGF1 gene transfected adipose-derived mesenchymal stem cell (AD-MSC

Topics: Adipocytes; Adipose Tissue; Animals; Cell Differentiation; Cerebrum; Disease Models, Animal; Fibroblast Growth Factor 1; Gene Expression; Humans; Infarction, Middle Cerebral Artery; Infusions, Intravenous; Male; Mesenchymal Stem Cell Transplantation; Mesenchymal Stem Cells; Radiopharmaceuticals; Rats; Rats, Wistar; Recovery of Function; Rotarod Performance Test; Stroke; Technetium Tc 99m Exametazime; Transgenes

Strategies to promote angiogenesis can benefit cerebral ischemia. We determined whether liposomal delivery of angiogenic peptides with a known biologic activity of vascular endothelial growth factor benefitted cerebral ischemia. Also, the study examined the potential of (18)F-FDG PET imaging in ischemic stroke treatment.. Male Sprague-Dawley rats (n = 40) underwent 40 min of middle cerebral artery occlusion. After 15 min of reperfusion, the rats (n = 10) received angiogenic peptides incorporated into liposomes. Animals receiving phosphate-buffered solution or liposomes without peptides served as controls. One week later, (18)F-FDG PET imaging was performed to examine regional changes in glucose utilization in response to the angiogenic therapy. The following day, (99m)Tc-hexamethylpropyleneamine oxime autoradiography was performed to determine changes in cerebral perfusion after angiogenic therapy. Corresponding changes in angiogenic markers, including von Willebrand factor and angiopoietin-1 and -2, were determined by immunostaining and polymerase chain reaction analysis, respectively.. A 40-min period of middle cerebral artery occlusion decreased blood perfusion in the ipsilateral ischemic cortex of the brain, compared with that in the contralateral cortex, as measured by (99m)Tc-hexamethylpropyleneamine oxime autoradiography. Liposomal delivery of angiogenic peptides to the ischemic hemisphere of the brain attenuated the cerebral perfusion defect compared with controls. Similarly, vascular density evidenced by von Willebrand factor-positive staining was increased in response to angiogenic therapy, compared with that of controls. This increase was accompanied by an early increase in angiopoietin-2 expression, a gene participating in angiogenesis. (18)F-FDG PET imaging measured at 7 d after treatment revealed that liposomal delivery of angiogenic peptides facilitated glucose utilization in the ipsilateral ischemic cortex of the brain, compared with that in the controls. Furthermore, the change in regional glucose utilization was correlated with the extent of improvement in cerebral perfusion (r = 0.742, P = 0.035).. Liposomal delivery of angiogenic peptides benefits cerebral ischemia. (18)F-FDG PET imaging holds promise as an indicator of the effectiveness of angiogenic therapy in cerebral ischemia.

Topics: Animals; Brain; Brain Ischemia; Cerebrovascular Circulation; Drug Delivery Systems; Fluorodeoxyglucose F18; Glucose; Ischemia; Liposomes; Male; Multimodal Imaging; Neovascularization, Pathologic; Peptides; Perfusion; Positron-Emission Tomography; Rats; Rats, Sprague-Dawley; Stroke; Technetium; Technetium Tc 99m Exametazime; Tomography, X-Ray Computed

Stroke is the most common cause of death and disability from neurologic disease in humans. Activation of microglia and matrix metalloproteinases (MMPs) is involved in positively and negatively affecting stroke outcome. Novel, noninvasive, multimodal imaging methods visualizing microglial and MMP alterations were employed. The spatio-temporal dynamics of these parameters were studied in relation to blood flow changes. Micro positron emission tomography (μPET) using [(18)F]BR-351 showed MMP activity within the first days after transient middle cerebral artery occlusion (tMCAo), followed by increased [(18)F]DPA-714 uptake as a marker for microglia activation with a maximum at 14 days after tMCAo. The inflammatory response was spatially located in the infarct core and in adjacent (penumbral) tissue. For the first time, multimodal imaging based on PET, single photon emission computed tomography, and magnetic resonance imaging revealed insight into the spatio-temporal distribution of critical parameters of poststroke inflammation. This allows further evaluation of novel treatment paradigms targeting the postischemic inflammation.

Topics: Animals; Immunohistochemistry; Infarction, Middle Cerebral Artery; Magnetic Resonance Imaging; Matrix Metalloproteinases; Mice; Mice, Inbred C57BL; Microglia; Multimodal Imaging; Neuroimaging; Positron-Emission Tomography; Pyrazoles; Pyrimidines; Radiopharmaceuticals; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

To determine whether severe cerebral perfusion defects measured by SPECT prior to rt-PA therapy attribute to severe intracerebral hemorrhage (SICH).. We measured baseline cerebral blood flow (CBF) using technetium-99m-labeled hexamethylpropyleneamine oxime (99mTc-HMPAO) SPECT qualitatively prior to rt-PA therapy, in 52 consecutive patients (range 38-93 years). The degree and extent of the asymmetry of local CBF were analyzed semi-quantitatively. We did not administrate rt-PA in patients with severe perfusion defects. Clinical outcome and the incidence of SICH were studied.. Three (5.8%) patients had severe perfusion defects that were undetected by CT and/or DWI. The other 49 (94.2%) patients had mild perfusion defects. The asymmetry of local CBF was 0.08±0.08 (n=3) and 0.3±0.15 (n=49) in the two groups, respectively. The percentages of the ipsilateral hemisphere in which perfusion was impaired severely were 17.5±9.5% (n=3) and 0.43±0.87% (n=49). Two patients were found petechial hemorrhage, but there was no patient who developed SICH in the former group following conventional antithrombotic therapy. In the latter group, SICH occurred in 1/49 (2.0%) patient following rt-PA therapy.. These results suggest that rt-PA therapy for patients with severe cerebral perfusion defects may cause SICH and baseline CBF may contribute to identify patients at high risk for SICH after intravenous rt-PA therapy.

Topics: Aged; Aged, 80 and over; Antifibrinolytic Agents; Brain; Brain Ischemia; Cerebrovascular Circulation; Female; Functional Laterality; Humans; Injections, Intravenous; Male; Middle Aged; Neurologic Examination; Radiopharmaceuticals; Stroke; Technetium Tc 99m Exametazime; Tissue Plasminogen Activator; Tomography, Emission-Computed, Single-Photon; Treatment Outcome

Hypoperfusion on single-photon emission computed tomography (SPECT) of the stroke-like lesion (SLL) at the hyperacute stage of mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) is considered to be a supportive evidence of the mitochondrial angiopathy theory. Our objectives were to examine whether other neuroimages, especially transcranial color-coded sonography (TCCS), done at the hyperacute stage of stroke-like episode (SLE) is consistent with hypoperfusion of the SLL. We reviewed the magnetic resonance imaging (MRI), SPECT, cerebral angiography, and TCCS of a patient with MELAS syndrome, all of which were performed at the hyperacute stage of one SLE. MRI on the 1st day post SLE showed right temporoparietal lesion with vasogenic edema. SPECT on the 2nd day showed focal decreased uptake of technetium-99m hexamethylpropyleneamine oxime ((99m)Tc-HMPAO) in the same region, but cerebral angiography and TCCS on the 3rd day showed increased regional cerebral blood flow (rCBF) and distal arteriole dilation in the same region. TCCS can delineate increased rCBF of the SLL at the hyperacute stage of SLE. We propose that the discrepancy between the decreased (99m)Tc-HMPAO uptake and increased rCBF might be caused by mitochondrial dysfunction. The phenomenon of "hypoperfusion" on SPECT might be caused by cell dysfunction but not decreased rCBF. We suggest that SPECT can be complemented by angiography and TCCS in future studies to delineate the perfusion status of SLLs.

Topics: Adult; Brain Edema; Cerebral Angiography; Cerebrovascular Circulation; Humans; Hyperemia; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Male; MELAS Syndrome; Middle Cerebral Artery; Perfusion; Radiopharmaceuticals; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed; Ultrasonography, Doppler, Transcranial

Arterial spin labelling (ASL) is increasingly available for noninvasive cerebral blood flow (CBF) measurement in stroke research. Here, a pseudo-continuous ASL technique (pCASL) was evaluated against (99m)Tc-D, L-hexamethylpropyleneamine oxime ((99m)Tc-HMPAO) autoradiography in a rat stroke model. The (99m)Tc-HMPAO was injected (intravenously, 225 MBq) during pCASL acquisition. The pCASL and (99m)Tc-HMPAO autoradiography CBF measures, relative to the contralateral hemisphere, were in good agreement across the spectrum of flow values in normal and ischemic tissues. The pCASL-derived quantitative regional CBF values (contralateral: 157 to 177 mL/100 g per minute; ipsilateral: 9 to 104 mL/100 g per minute) were consistent with the literature values. The data show the potential utility of pCASL for CBF assessment in a rat stroke model.

Topics: Animals; Brain Ischemia; Cerebrovascular Circulation; Disease Models, Animal; Magnetic Resonance Angiography; Radiography; Radiopharmaceuticals; Rats; Rats, Sprague-Dawley; Spin Labels; Stroke; Technetium Tc 99m Exametazime

Blood flow interruption in a cerebral artery causes brain ischemia and induces dramatic changes of perfusion and metabolism in the corresponding territory. We performed in parallel positron emission tomography (PET) with [(15)O]H(2)O, single photon emission computed tomography (SPECT) with [(99m)Tc]hexamethylpropylene-amino-oxime ([(99m)Tc]HMPAO) and ultrasonic ultrafast shear wave imaging (SWI) during, immediately after, and 1, 2, 4, and 7 days after middle cerebral artery occlusion (MCAO) in rats. Positron emission tomography and SPECT showed initial hypoperfusion followed by recovery at immediate reperfusion, hypoperfusion at day 1, and hyperperfusion at days 4 to 7. Hyperperfusion interested the whole brain, including nonischemic areas. Immunohistochemical analysis indicated active angiogenesis at days 2 to 7, strongly suggestive that hyperperfusion was supported by an increase in microvessel density in both brain hemispheres after ischemia. The SWI detected elastic changes of cerebral tissue in the ischemic area as early as day 1 after MCAO appearing as a softening of cerebral tissue whose local internal elasticity decreased continuously from day 1 to 7. Taken together, these results suggest that hyperperfusion after cerebral ischemia is due to formation of neovessels, and indicate that brain softening is an early and continuous process. The SWI is a promising novel imaging method for monitoring the evolution of cerebral ischemia over time in animals.

Topics: Animals; Cerebrovascular Circulation; Disease Models, Animal; Elasticity; Elasticity Imaging Techniques; Male; Neovascularization, Physiologic; Perfusion; Positron-Emission Tomography; Rats; Rats, Sprague-Dawley; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Human mesenchymal stem cells (hMSC) are a promising source for cell therapy after stroke. To deliver these cells, an IV injection appears safer than a local graft. We aimed to assess the whole-body biodistribution of IV-injected (99m)Tc-HMPAO-labeled hMSC in normal rats (n = 9) and following a right middle cerebral artery occlusion (MCAo, n = 9). Whole-body nuclear imaging, isolated organ counting (at 2 and 20 h after injection) and histology were performed. A higher activity was observed in the right damaged hemisphere of the MCAo group [6.5 +/- 0.9 x 10(-3) % of injected dose (ID)/g] than in the control group (3.6 +/- 1.2 x 10(-3) %ID/g), 20 h after injection. In MCAo rats, right hemisphere activity was higher than that observed in the contralateral hemisphere at 2 h after injection (11.6 +/- 2.8 vs. 9.8 +/- 1.7 x 10(-3) %ID/g). Following an initial hMSC lung accumulation, there was a decrease in pulmonary activity from 2 to 20 h after injection in both groups. The spleen was the only organ in which activity increased between 2 and 20 h. The presence of hMSC was documented in the spleen, liver, lung, and brain following histology. IV-injected hMSC are transiently trapped in the lungs, can be sequestered in the spleen, and are predominantly eliminated by kidneys. After 20 h, more hMSC are found in the ischemic lesion than into the undamaged cerebral tissue. IV delivery of hMSC could be the initial route for a clinical trial of tolerance.

Topics: Animals; Humans; Injections, Intravenous; Magnetic Resonance Imaging; Mesenchymal Stem Cell Transplantation; Mesenchymal Stem Cells; Radiopharmaceuticals; Rats; Rats, Sprague-Dawley; Stroke; Technetium Tc 99m Exametazime; Tissue Distribution; Whole-Body Counting

Hyperthermia can be the result of many causes such as environmental conditions, brain tumors and infectious diseases. Since hyperthermia is very common, its role in causing stroke through a decrease in cerebral blood flow needed further emphasis. The aim of this study was to record cerebral blood flow in vitro by using isolated rabbit carotid artery strips and in-vivo using radioactive isotope scanning during temperature elevation. The recording of isometric tension in rabbit carotid artery strips in organ baths, and the scintigraphic cerebral imaging of technetium-99m-hexamethyl-propyleneamineoxime (99mTc-HMPAO) using Gamma camera, were acquired at control and higher body temperature by 4 degrees C. Blood pressure was measured through femoral artery and cerebral blood flow was measured through carotid artery. Elevating temperature by 4 degrees C induced reproducible contraction. During hyperthermia, the carotid artery contraction leads to a decrease in cerebral blood flow although the blood pressure did not decrease. The uptake of 99mTc-HMPAO in the brain was significantly reduced. This decrease in cerebral perfusion is regionally dependent, which is more in the frontal area, the cerebral hemispheres than the cerebellum. The decrease was 36+/-3, 37+/-2, 22+/-2%, respectively. Hyperthermia causes carotid artery contraction leading to decrease in cerebral blood flow, which was confirmed by 99mTc-HMPAO images. The decrease is regionally dependent. Since the blood pressure did not decrease by heating, the reduction in cerebral perfusion is mainly due to carotid contraction. The applied neck cooling may be considered as a promising therapeutic strategy for the hyperthermic patient to avoid brain damage. This can be achieved by external application of an ice-water-perfused neck collar.

Topics: Animals; Blood Pressure; Brain; Carotid Arteries; Cerebrovascular Circulation; Fever; Hypothermia, Induced; Male; Neck; Rabbits; Radionuclide Imaging; Radiopharmaceuticals; Regional Blood Flow; Stroke; Technetium Tc 99m Exametazime; Vasoconstriction

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 blood flow tests have increasingly been advocated for the confirmation of brain death (BD). Four-vessel angiography has been considered the most reliable investigation in the diagnosis of BD for >30 yrs, but it is invasive. (99m)Tc-HMPAO SPECT provides noninvasive, multiplanar imaging of brain tissue perfusion. The aim of this study was to check the reliability of SPECT compared with contrast angiography.. Prospective, blind study.. Neurointensive care unit of a university hospital.. Consecutive clinically brain dead patients with flat electroencephalogram.. BD was diagnosed according to Italian law. (99m)Tc-HMPAO SPECT and four-vessel angiography were performed in the same session; the rater of each investigation ignored the results of the other. Blood pressure, Sp(O2), and P(ECO2) were monitored throughout the study: any episode of hypoxia or hypotension caused exclusion of the patient from the study.. Twenty brain dead patients were enrolled. The cause of BD was head injury in seven cases (35%), subarachnoid hemorrhage in seven (30%), spontaneous hemorrhage in one (10%), brain tumors in two (10%), stroke in two (10%), and thrombosis of the sagittal sinus in one (5%). Both angiography and SPECT confirmed BD in 19 of 20 patients: angiography showed the absence of filling of intracranial arteries, while SPECT showed a picture of "empty skull." For the remaining patient, angiography showed slight and late filling of left vertebral, basilar, and posterior cerebral arteries, while SPECT showed faint traces of uptake in the posterior fossa on the right side and on the midline. For this patient, the tests were repeated 48 hrs later, and both showed the arrest of intracranial circulation, thus confirming BD.. Our results confirm the reliability of SPECT in the diagnosis of BD; because SPECT is noninvasive, it is a good candidate for the "gold standard" of diagnosis.

Topics: Adult; Aged; Aged, 80 and over; Brain Death; Brain Neoplasms; Cerebral Angiography; Cerebral Hemorrhage; Female; Humans; Intracranial Thrombosis; Male; Middle Aged; Prospective Studies; Radiopharmaceuticals; Stroke; Subarachnoid Hemorrhage; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

The study investigates the effect of zolpidem (CAS 82626-48-0) on brain injuries and cerebellar diaschisis. Four patients with varied brain injuries, three of them with cerebellar diaschisis, were imaged by 99mTc HMPAO Brain SPECT before and after application of zolpidem. The baseline SPECT before zolpidem showed poor tracer uptake in brain injury areas and cerebellar diaschisis. After zolpidem, cerebral perfusion through brain injury areas improved substantially in three patients and the cerebellar diaschisis was reversed. Observations point to a GABA based phenomenon that occurs in brain injury and diaschisis that is reversible by zolpidem.

Topics: Adult; Brain Injuries; Cerebellar Diseases; Cerebrovascular Circulation; Child, Preschool; Diabetes Mellitus; Humans; Hypnotics and Sedatives; Male; Near Drowning; Persistent Vegetative State; Pyridines; Radiopharmaceuticals; Spinocerebellar Ataxias; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Zolpidem

Intraarterial thrombolytic therapy has been used recently for treatment of acute ischemic stroke within 6 h after onset. Although hypoactivity of 99mTc-hexamethylpropyleneamine oxime (HMPAO) in stroke has been well documented, hyperactivity of HMPAO has not been evaluated in sufficient detail. The purpose of this study was to evaluate the incidence and clinical importance of hyperactivity of HMPAO in management of patients with acute ischemic stroke.. We retrospectively investigated HMPAO SPECT in 90 patients with acute ischemic stroke within 6 h after onset. The lesion-to-contralateral radioactivity ratios (L/Cs) were calculated on the SPECT images before treatment and were compared with the imaging results of CT or MRI (or both).. Hyperactivity of HMPAO, accompanied by surrounding hypoactivity, was observed in 6 of 90 patients (7%) within 6 h after onset. The L/Cs ranged from 1.17 to 2.95. Two patients showed hyperactivity in the cortex and the other 4 patients showed hyperactivity in the basal ganglia. Angiography confirmed spontaneous recanalization of occluded vessels in accordance with the area of hyperactivity. In both patients with cortical hyperactivity, cerebral infarctions were revealed on follow-up CT; in 1 patient, hemorrhagic transformation developed after intraarterial thrombolytic therapy. In 3 of the 4 patients with hyperactivity in the basal ganglia, follow-up CT showed no infarction in the surrounding hypoperfused cortex (selective intraarterial thrombolytic therapy was performed on 2 patients), although various degrees of infarction were observed in the basal ganglia. Obvious infarctions developed in the basal ganglia and the cortex of the other patient.. Hyperactivity of HMPAO could be seen in the basal ganglia and the cortex within 6 h after onset, reflecting spontaneous recanalization. The areas of hyperactivity may develop infarctions, whereas the accompanying areas of hypoactivity could be rescued by selective intraarterial thrombolytic therapy.

Topics: Acute Disease; Adult; Aged; Aged, 80 and over; Brain Ischemia; Cerebral Angiography; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Radiopharmaceuticals; Retrospective Studies; Stroke; Technetium Tc 99m Exametazime; Thrombolytic Therapy; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed

We investigated the effect of nonlinear alignment on SPECT images with lesions. Linear alignment produces reliable results but the introduction of nonlinear methods can improve matching by accounting for global brain shape. We examined the hypothesis that nonlinear alignment can introduce unwanted image distortions when lesions are present. We set out to quantify possible distortions by constructing artificial lesions in order to obtain images with controllable characteristics. We examined the use of basis functions (in SPM96 and SPM99) and other nonlinear models (in AIR3.08) designed to achieve optimum alignment between image and template. We found that the use of models with high degrees of nonlinearity will result in unwanted deformations and that the safest way to align images with lesions is to use 12-point linear affine transformations. Masking was examined as a remedy to distortions caused by nonlinear methodologies and produced significantly improved results.

Topics: Artifacts; Brain Injuries; Contrast Media; Humans; Image Processing, Computer-Assisted; Nonlinear Dynamics; Reference Values; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

We describe a patient with seizures following a stroke in whom on ictal 99mTc-HMPAO single-photon emission computed tomography demonstrated cerebral blood flow "schistotaxis", i.e., focal hyperaemia corresponding to an epileptogenic focus together with an extensive hypoperfused area in the same hemisphere. This phenomenon may have been caused by haemodynamic alternation and a remote transneural effect during the seizures.

Topics: Aged; Cerebrovascular Circulation; Female; Humans; Radiopharmaceuticals; Regional Blood Flow; Seizures; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

The detection of subclinical abnormalities in cerebral blood flow could be of great value in identifying diabetic patients at risk of stroke. The aim of this study was to assess the contribution of semiquantified post-acetazolamide technetium-99m hexamethylpropylene amine oxime single-photon emission tomography (99mTc-HMPAO SPET) in 15 diabetic patients with no clinical history of central neurological disease. After baseline 99mTc-HMPAO SPET, a second SPET scan was acquired after activation of the cerebrovascular reserve (CVR) with an injection of 1 g of acetazolamide (post-ACZ SPET). Semiquantitative analysis was made in 16 regions of interest (ROIs) drawn for each of the three supratentorial slices selected, and in two ROIs in the infratentorial slice. The CVR was calculated in each ROI by subtracting the decay-corrected baseline images from those obtained in the post-ACZ SPET and expressed as the percent increase in the average counts between the two scans. Baseline perfusion and CVR values in the study group were compared with the corresponding values in a control group. Of 750 cortical ROIs studied, 332 showed a decreased CVR (44.3%). The baseline perfusion SPET study showed hypoperfusion in 65 ROIs (8.6%) and hyperperfusion in 56 (7.4%). Of the 65 hypoperfused regions, 66.2% had a normal CVR and 33.8% had a decreased CVR, whereas of the 56 hyperperfused regions, 51.8% had a CVR within normal limits and 48.2% showed a decreased CVR. In conclusion, in comparison with baseline 99mTc-HMPAO SPET, the ACZ activation test provided additional information in the study of cerebrovascular impairment, and allowed characterisation of the subclinical abnormalities in the population studied. The technique may therefore prove useful in evaluating future preventive strategies for stroke in diabetic patients.

Topics: Acetazolamide; Adult; Carbonic Anhydrase Inhibitors; Cerebrovascular Circulation; Diabetes Mellitus, Type 1; Diabetic Angiopathies; Female; Humans; Male; Middle Aged; Radiopharmaceuticals; Risk Factors; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

We report cerebral SPECT studies on two siblings with the syndrome of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS). Tc-99m HMPAO brain SPECT was performed 8, 19 and 30 days after a stroke-like episode in one case and 10 days after a stroke-like episode, 6 h after a partial seizure and as a follow-up study in the other. Increased blood flow was seen in both these patients with stroke-like episodes due to MELAS. The cause of the increased blood flow is uncertain, but it may be related to the decreased pH created by local increase in lactic acid.

Topics: Adult; Brain; Cerebral Cortex; Cerebrovascular Circulation; Female; Humans; Hydrogen-Ion Concentration; Male; MELAS Syndrome; Radiopharmaceuticals; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Crossed cerebellar diaschisis (CCD) tends to persist or even worsen after supratentorial infarction. Several studies have shown impairment of cerebral vasomotor responsiveness in the hemispheric area of diaschisis in patients with hemispheric infarction. This finding has led to the concern that the lack of CCD reversibility might be associated with chronic circulatory abnormalities. We therefore assessed the vasoreactivity in the cerebellar hemisphere in which diaschisis is manifested using acetazolamide (ACZ) and SPECT.. Eight stroke patients with CCD (5 with unilateral hemispheric infarcts and 3 with unilateral intracerebral hemorrhage) had 99mTc-HMPAO SPECT scanning at rest and 20 min after intravenous injection of 1.0 g ACZ. The time interval after stroke ranged from 25 to 904 d. From the total counts obtained from each cerebellar hemisphere, the asymmetry index (AI) was calculated as (unaffected - affected cerebellar hemisphere)/unaffected cerebellar hemisphere x100.. After ACZ, the mean AI (8.7+/-6.6) was significantly decreased (P<0.05) compared with that at rest (17.7+/-5.8). Seven of the 8 patients showed decrease in the AI after ACZ. In 1 patient, the direction of the asymmetry was reversed after ACZ so that the AI was negative. The ACZ-induced change in the AI did not show a significant correlation with the time interval after stroke, whether calculated in absolute terms or as a percentage change.. This study shows that normal vascular supply is maintained in the CCD-affected cerebellar hemisphere over long periods of time after a stroke. Thus, the lack of CCD reversibility may not be attributed to a chronic circulatory insufficiency. The results lend support to the concept of functional deactivation and subsequent transneuronal degeneration as a likely explanation for CCD. It is unclear whether decreased AI after ACZ indicates a higher vascular response of the affected cerebellar hemisphere than that of the normal side.

Topics: Acetazolamide; Cerebrovascular Circulation; Female; Humans; Male; Middle Aged; Radiopharmaceuticals; Stroke; Technetium Tc 99m Exametazime; Time Factors; Tomography, Emission-Computed, Single-Photon

Loss of psychic self-activation has been described after bilateral lesions to the globus pallidus, striatum, and white matter of the frontal lobes, but it is a very rare sign of bithalamic lesions. The exact functional-anatomic mechanism underlying loss of psychic self-activation following bithalamic lesions remains to be elucidated.. We present clinical, neuropsychological, structural, and functional neuroimaging data of an 18-month follow-up period of a man with prominent loss of psychic self-activation after coronary arteriography. Except for memory decline, accompanying symptoms remained restricted to the acute phase. The neurobehavioral syndrome consisted mainly of apathy, indifference, poor motivation, and flattened affect, and this remained unchanged during the entire follow-up period. MRI showed a bithalamic infarction involving the nucleus medialis thalami bilaterally. Single-photon emission CT revealed a severe relative hypoperfusion of both thalami, a relative hypoperfusion of both nuclei caudati, and a relative hypoperfusion mesiofrontally.. Single-photon emission CT data support the hypothesis that the neurobehavioral manifestations after bithalamic paramedian infarction are caused by disruption of the striatal-ventral pallidal-thalamic-frontomesial limbic loop. Probably, bilateral disruption at different levels of the striatal-ventral pallidal-thalamic-frontomesial loop may lead to a similar clinical picture consisting of loss of psychic self-activation.

Topics: Affect; Amnesia; Arousal; Awareness; Cerebral Infarction; Functional Laterality; Humans; Intelligence Tests; Male; Middle Aged; Motivation; Radiopharmaceuticals; Self Concept; Stroke; Technetium Tc 99m Exametazime; Thalamus; Tomography, Emission-Computed, Single-Photon

By means of positron emission tomography (PET), we investigated the hemodynamic and metabolic state of the hyperfixation identified as the increased accumulation with 99mTc-d,l-hexamethylpropyleneamine oxime (HMPAO) by single photon emission computed tomography (SPECT) in patients with subacute stroke. We studied four patients with subacute stroke having hyperfixed areas evaluated with CBF, CMRO2, OEF and CBV by PET. The hyperfixation rate with 99mTc-HMPAO was obtained by comparing the surplus rate with standardized CBF. The OEF and CMRO2 values in the hyperfixed areas of 4 patients were significantly lower than those in normal 5 controls (p < 0.01), but CBF and CBV were almost the same in patients and normal controls, but the hyperfixation rate of 0.30 +/- 0.15 in 4 patients correlated well with CBV (r = 0.97, y = 11.75x + 0.42; p < 0.05). Hyperfixation with 99mTc-HMPAO in the infarct area revealing a mismatch between CMRO2 and CBF meant relative luxury perfusion. The hyperfixation rate determined by 99mTc-HMPAO brain SPECT correlated with CBV in the PET study. We can conclude that one of the main factors which caused hyperfixation was vasodilatation as well as the blood brain barrier disruption and the neovascularization.

Topics: Adult; Aged; Aphasia; Brain; Cerebrovascular Circulation; Female; Hemodynamics; Humans; Male; Middle Aged; Oxygen Consumption; Paresis; Radiopharmaceuticals; Reference Values; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed; Tomography, Emission-Computed, Single-Photon

Early recanalisation by thrombolysis is a conclusive therapy for acute ischaemic stroke. But this therapy may increase the risk of intracerebral haemorrhage or severe brain oedema. The purpose was to evaluate usefulness of quantitative measurement of cerebral blood flow by single photon emission computed tomography (SPECT) in predicting the risk of haemorrhage or oedema, and determining the therapeutic options in acute hemispheric ischaemic stroke.. The relation was studied retrospectively between initial regional cerebral blood flow (rCBF) quantitatively measured by technetium-99m-labelled hexamethylpropyleneamine oxime ((99m)Tc-HMPAO) SPECT and final clinical and radiological outcome in 20 patients who presented hemispheric ischaemic stroke and were treated conservatively or received early recanalisation by local intra-arterial thrombolysis. The non-invasive Patlak plot method was used for quantitative measurement of rCBF by SPECT.. Regions where residual rCBF was preserved over 35 ml/100 g/min had a low possibility of infarction without recanalisation and regions where residual rCBF was preserved over 25 ml/100 g/min could be recovered by early recanalisation. However, regions where residual rCBF was severely decreased (< 20 ml/100 g/min) had a risk of intracerebral haemorrhage and severe oedema.. A quantitative assessment of residual rCBF by (99m)Tc-HMPAO SPECT is useful in predicting the risk of haemorrhage or severe oedema in acute ischaemic stroke. Therapeutic options should be determined based on the results of rCBF measurement.

Topics: Acute Disease; Aged; Aged, 80 and over; Brain Ischemia; Cerebrovascular Circulation; Female; Humans; Male; Middle Aged; Organotechnetium Compounds; Oximes; Prognosis; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Patients undergoing long-term renal replacement therapy (such as dialysis) have an increased risk for significant cognitive impairment, which may result in memory problems and subsequently missed attendance at dialysis. The aim of this study was to try to identify any abnormalities of cerebral perfusion that could explain a patient's cognitive impairment and to determine if the pattern of these abnormalities would suggest a cause.. 17 patients (13 men; mean age, 60 years; age range, 29-74 years) in end-stage renal failure or on dialysis had SPECT imaging 10 minutes after injection of 550 MBq (15 mCi) Tc-99m HMPAO. Two of the patients had a history of previous stroke. Other risk factors for stroke were noted in most of the patients (hypertension in 10 patients, smoking or former smoking in 10 patients, and cardiac atherosclerosis in 7 patients). In all patients, attenuation correction was applied and the images were reconstructed into three sets of orthogonal slices. Activity in the frontal and temporal lobes was compared by quantification against the ipsilateral and contralateral cerebellum.. Discrete cortical defects consistent with infarcts were seen in 14 patients. The mean right and left frontal-to-cerebellar ratio was 0.837 (SD, 0.09) and 0.837 (SD, 0.08), respectively. This was not significantly different from the right and left temporal-to-cerebellar ratios of 0.843 (SD, 0.07) and 0.848 (SD, 0.07), respectively. Both were within normally accepted ranges.. Patients in end-stage renal failure who also had cognitive impairment appear to have a high number of cortical defects consistent with infarcts (suggesting a multiple-infarct type of dementia). There was no evidence of Alzheimer-type dementia.

Topics: Adult; Aged; Brain; Cerebrovascular Circulation; Cognition Disorders; Dementia, Multi-Infarct; Female; Humans; Kidney Failure, Chronic; Male; Middle Aged; Prospective Studies; Renal Replacement Therapy; Risk Factors; Stroke; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon