Tc-ECD Single-photon Emission Computed Tomography Research Articles

Concordance between 99mTc‐ECD SPECT and 18F‐FDG PET interpretations in patients with cognitive disorders diagnosed according to NIA‐AA criteria

The purpose of this study was to clarify the concordance of diagnostic abilities and interobserver agreement between 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and brain perfusion single photon-emission computed tomography (SPECT) in patients with Alzheimer's disease (AD) who were diagnosed according to the research criteria of the National Institute of Aging-Alzheimer's Association Workshop. Fifty-five patients with "AD and mild cognitive impairment (MCI)" (n = 40) and "non-AD" (n = 15) were evaluated with 18F-FDG PET and (99m)Tc-ethyl cysteinate dimer (ECD) SPECT during an 8-week period. Three radiologists independently graded the regional uptake in the frontal, temporal, parietal, and occipital lobes as well as the precuneus/posterior cingulate cortex in both images. Kappa values were used to determine the interobserver reliability regarding regional uptake. The regions with better interobserver reliability between 18F-FDG PET and (99m)Tc-ECD SPECT were the frontal, parietal, and temporal lobes. The (99m)Tc-ECD SPECT agreement in the occipital lobes was not significant. The frontal, temporal, and parietal lobes showed good correlations between 18F-FDG PET and (99m)Tc-ECD SPECT in the degree of uptake, but the occipital lobe and precuneus/posterior cingulate cortex did not show good correlations. The diagnostic accuracy rates of "AD and MCI" ranged from 60% to 70% in both of the techniques. The degree of uptake on 18F-FDG PET and (99m)Tc-ECD SPECT showed significant correlations in the frontal, temporal, and parietal lobes. The diagnostic abilities of 18F-FDG PET and (99m)Tc-ECD SPECT for "AD and MCI," when diagnosed according to the National Institute of Aging-Alzheimer's Association Workshop criteria, were nearly identical.

Brain perfusion SPECT in limbic encephalitis associated with autoantibody against the glutamate receptor epsilon 2

The aim of this study was to elucidate the single-photon emission computed tomography (SPECT) pattern at the acute stage of disease in non-herpetic limbic encephalitis (NHLE) patients associated with the N-methyl-D-aspartate-type glutamate receptor epsilon 2 (GluR ϵ2) autoantibody using Z-score imaging system (eZIS) analyses. Brain magnetic resonance imaging (MRI) and brain perfusion SPECT using technetium-99 ethyl cysteinate dimer ((99m)Tc-ECD) were performed in eight patients with NHLE (5 men and 3 women; mean age 48.8±22 years) within 20days after clinical onset. All patients had various clinical limbic-associated symptoms and no evidence of herpes simplex infection or systemic malignancies. Two of eight patients showed abnormally hyperintense lesions on diffusion-weighted images and significant hyperperfusion in ipsilateral cerebral cortex on eZIS analysis, whereas other patients showed normal MRI findings and significant hypoperfusion in one or both sides of the limbic and paralimbic areas. We suggest that (99m)Tc-ECD SPECT study using eZIS analyses may be helpful to detect the neuronal dysfunction, particularly in NHLE patients without abnormal MRI findings.

The influence of the tracer injection–acquisition interval on the distribution of 99mTc-ECD in the brain of laboratory cats

Abstract Single-photon emission computed tomography (SPECT) can be used to study the regional distribution of the cerebral blood flow in the feline brain without interference of anesthetics. When the tracer, 99m technetium-ethyl cysteinate dimer ( 99m Tc-ECD), is injected in the awake animal, the acquisition can be performed afterward under general anesthesia, whereas the tracer distribution still represents the regional cerebral blood flow (rCBF) in the awake animal. The aim of this study was to look at the in vivo stability of 99m Tc-ECD in the feline brain. For this purpose, 6 cats (n = 6) were used, and 3 serial acquisitions were performed starting at 40 (T40), 60 (T60), and 85 (T85) minutes after tracer injection. Total counts and perfusion indices (PIs), normalized to the total brain and to the cerebellum, were calculated. When T85 was compared with T40, total counts decreased, depending on the brain region, with 29% (left thalamus) to 51% (bulbus olfactorius). These regional differences in tracer clearance resulted in significantly altered PIs at T85 as compared with T40. This study shows that 99m Tc-ECD SPECT can be used in cats for studying the rCBF and that the clearance of 99m Tc-ECD in the feline brain is region dependent. As a result, the acquisition should be started between 40 and 60 minutes after tracer injection.

Optimized Data Preprocessing for Multivariate Analysis Applied to 99mTc-ECD SPECT Data Sets of Alzheimer's Patients and Asymptomatic Controls

Multivariate image analysis has shown potential for classification between Alzheimer's disease (AD) patients and healthy controls with a high-diagnostic performance. As image analysis of positron emission tomography (PET) and single photon emission computed tomography (SPECT) data critically depends on appropriate data preprocessing, the focus of this work is to investigate the impact of data preprocessing on the outcome of the analysis, and to identify an optimal data preprocessing method. In this work, technetium-99methylcysteinatedimer ((99m)Tc-ECD) SPECT data sets of 28 AD patients and 28 asymptomatic controls were used for the analysis. For a series of different data preprocessing methods, which includes methods for spatial normalization, smoothing, and intensity normalization, multivariate image analysis based on principal component analysis (PCA) and Fisher discriminant analysis (FDA) was applied. Bootstrap resampling was used to investigate the robustness of the analysis and the classification accuracy, depending on the data preprocessing method. Depending on the combination of preprocessing methods, significant differences regarding the classification accuracy were observed. For (99m)Tc-ECD SPECT data, the optimal data preprocessing method in terms of robustness and classification accuracy is based on affine registration, smoothing with a Gaussian of 12 mm full width half maximum, and intensity normalization based on the 25% brightest voxels within the whole-brain region.

Residual brain viability, evaluated by 99mTc-ECD SPECT, in patients with suspected brain death and with confounding clinical factors

In 1968, the Harvard criteria for brain death diagnosis were introduced in clinical practice. These include no movements or breathing, no reflexes, and flat electroencephalogram in the absence of confounding factors, including hypothermia, drugs, electrolyte, and endocrine disturbances. When confounding factors occur, confirmatory tests documenting the absence of cerebral blood flow, such as cerebral angiogram, transcranial Doppler sonography, computed tomography angiography, and nuclear techniques, are required. The aim of this study was to evaluate the clinical value of single-photon emission computed tomography (SPECT) with technetium-99m (Tc)-ECD in the diagnosis of brain death in a cohort of patients with confounding factors. Fifty-two patients were studied between 1 January 2000 and 23 September 2008. The criteria for the request for Tc-ECD SPECT were sodic thiopental withdrawal after less than 24 h, unreceptivity and unresponsivity of brainstem reflexes, anesthesia in the last 24 h, hypothermia, anamnesis for barbiturate use, electroencephalogram artefacts, toxic state, and pediatric criteria. All patients underwent Tc-ECD SPECT using a dual-headed camera fitted with a high-resolution low-energy collimator. Images were reconstructed and processed according to standard procedures and interpreted qualitatively by two experienced observers. The presence of spots of residual brain viability was observed in 13 patients: 25% of our patient cohort. The patients with residual viability were younger (aged 30.92+/-17.28 years) in comparison with those with no viability (41.91+/-18.77 years, P<0.031). Considering the eligibility for transplantation, there were 12 of 13 patients in the residual viability group and 31 of 39 in the no viability group (P<0.0001). All patients with spots of brain uptake were monitored daily by Tc-ECD SPECT, and all of them reached the condition of empty skull after one or multiple studies. The opposition to organ donation was observed in six of 13 patients with spots of viable brain tissue and in three of 39 with no signs of residual viability (P<0.001). In patients with confounding factors in whom brain death diagnosis is equivocal, Tc-ECD SPECT is a helpful and safe diagnostic approach, allowing a three-dimensional evaluation of cortical and brainstem viability. It guarantees an unequivocal diagnosis of brain death for patients who are potential candidates for organ donation. The persistence of viable spots of brain tissue was found in 25% of our patients and was more frequent in young patients. This affects the opposition to donation.

Thalamic and limbic involvement in the mechanism of action of vagus nerve stimulation, a SPECT study

To unravel the mechanism of action of neurostimulation as a treatment for seizures, functional neuroimaging tools allow minimally invasive research in humans. We performed single-photon emission computed tomography (SPECT) in patients with epilepsy, treated with vagus nerve stimulation (VNS). Changes in regional cerebral blood flow (rCBF) at the time of initial stimulation as well as after chronic treatment were correlated with long-term clinical efficacy. In this pilot study, 27 patients (14 female and 13 male) who were treated with VNS at Ghent University Hospital for refractory epilepsy underwent a (99m)Tc-ECD (ethyl cystein dimer) SPECT activation study at the time the first stimulation train was administered. 12 patients underwent an additional (99m)Tc-ECD SPECT activation study 6 months later. Image acquisition was performed on a high-resolution triple-headed gamma camera. Significant rCBF changes were correlated with prospectively assessed clinical efficacy data. Significant rCBF changes were found in the thalamus, the hippocampus and the parahippocampal gyrus. Acute limbic hyper-perfusion and chronic thalamic hypo-perfusion correlate with positive clinical efficacy. Acute and chronic electrical stimulation of the vagus nerve induces rCBF changes that can be measured by SPECT on a group-basis. The thalamus and the limbic system are thought to play a key role in the mechanism of action of VNS.

Early Dynamic SPECT Imaging in Acute Viral Encephalitis

Several cases have reported that dynamic single-photon emission computed tomography (SPECT) shows increased tracer uptake in acute herpes simplex viral encephalitis (HSVE). The purpose of this study was to evaluate the clinical usefulness of dynamic Tc-ECD SPECT in patients with acute viral encephalitis. We performed the dynamic SPECT in 9 patients with acute viral encephalitis (4 women, 5 men, 49.5 +/- 17.4 years of age at onset). SPECT and magnetic resonance imaging (MRI) were performed within 2 weeks after acute clinical onset and at the time of resolution of acute symptoms. Cranial MRI showed high intensities in all patients (7 medial temporal and 2 lateral temporal lobes, 1 inferior temporal lobe, 2 insula and adjacent regions, 1 thalamus, 1 putamen). The initial dynamic SPECT showed increased accumulation of tracer, corresponding to the lesions on MRI in 3 patients with HSVE. Resolution of acute symptoms was associated with a reduction in increased tracer uptake. Six patients with non-HSVE showed no increased accumulation of tracer. Dynamic SPECT may be a new optional neuroradiologic technique that may help to establish a diagnosis in patients with suspected HSVE.

99mTc-ECD Brain SPECT in Patients with Persistent Post-Concussion Syndrome after Mild Head Injury and Normal Computed Tomography

Background. Post-concussion syndrome (PCS) has been defined as a clinical state where 3 or more symptoms (such as headache, poor memory, insomnia, anxiety or dizziness, etc.) persist for more than 3 months after mild closed head trauma. The purpose of this study was to evaluate the potential usefulness of 99mTc-ECD brain single photon emission computed tomography (SPECT) scan in patients with PCS for more than 3 months and absence of morphological abnormalities on computed tomography (CT) scan after mild closed head injury. Methods. Our study included 48 patients (20 men and 28 women ranging in age from 21 to 75years) who suffered from persistent clinical complaints for more than 3 months after mild closed head trauma. The most common complaints were headache, poor memory, insomnia, anxiety and dizziness. However, brain CT scan was normal in all patients. All patients received 99mTc-ECD brain SPECT imaging. None of these patients had previous traumatic brain injury, CVA, psychiatric disorders or history of drug or alcohol abuse. Results. Sixteen patients had normal and 32 patients had abnormal 99mTc-ECD brain SPECT scans. Conclusions99m. Tc-ECD brain SPECT scanning is a useful imaging modality, as a complement to CT, for evaluating cerebral perfusion changes in morphologically intact brain regions in patients with persistent PCS following mild traumatic brain injury. (Mid Taiwan J Med 2002;7:14-20)