Thalamic syndrome and cortical hypoperfusion on technetium-99m HM-PAO brain SPECT

The six patients included in this study had painful dysesthesia, resulting from vascular lesions in or near the thalamus, confirmed by computerized tomography(CT) brain scan. Using hexamethyl propyleneamine oxime(HM-PAO) single photon emission computed tomography(SPECT) brain scanning, regional cerebral perfusion(rCP) was demonstrated. In contrast to three patients with lesions near the thalamus who showed symmetrical cortical radioactivity, the other three patients with thalamic lesions revealed decreased rCP in the ipsilateral cerebral cortex on HM-PAO brain SPECT. We thought that the loss of afferent activating stimuli from the thalamus led to decreased cortical neuronal activity and the following hypoperfusion. In patients with thalamic syndrome resulting from thalamic lesions, the role of the remote effect of the thalamic damage and consequent cortical deregulation in the development of thalamic pain and/or neuropsychological symptoms cannot be excluded completely.     

Single photon emission tomography with 99m Tc-HMPAO in Arab patients with depression

BACKGROUND: This study investigates the rate of cerebral blood flow (rCBF) in Arab patients wth depression. METHODS: Forty-four patients with DSM-III-R major depressive disorders were studied at rest using single photon emission computerized tomography (SPECT) with 99m Tc-HMPAO in comparison with 20 normal controls. All patients were assessed using the Hamilton Rating Scale for Depression (HRSD). RESULTS: The depressed group showed greater rCBF in left and right posterior frontal and parietal cortical regions than normal controls. Within the depressed group, patients with the least severe illness (HRSD < 20) had significantly lower rCBF than normal controls, whilst those with moderately severe (HRSD 20-29) and severe (HRSD > 30) had significantly greater rCBF in most cortical regions than normal controls. Symptom scores, derived from the HRSD were predicted by rCBF principally increased rCBF in the left frontal cortex. CONCLUSIONS: These results suggest a generalized cerebral activation principally in the frontal cortex which is in contrast to the results of most previous studies but more in line with the results of studies of induced affect and some studies of depression subsyndromes.     

Association between major depressive symptoms in heart failure and impaired regional cerebral blood flow in the medial temporal region: a study using 99m Tc-HMPAO single photon emission computerized tomography (SPECT)

BACKGROUND AND PURPOSE: Depressive symptoms are frequently associated with heart failure (HF), but the brain mechanisms underlying such association are unclear. We hypothesized that the presence of major depressive disorder (MDD) emerging after the onset of HF would be associated with regional cerebral blood flow (rCBF) abnormalities in medial temporal regions previously implicated in primary MDD, namely the hippocampus and parahippocampal gyrus. METHOD: Using 99mTc-SPECT, we measured rCBF in 17 elderly MDD-HF patients, 17 non-depressed HF patients, and 18 healthy controls, matched for demographic variables. Group differences were investigated with Statistical Parametric Mapping. RESULTS: Significant rCBF reductions in MDD-HF patients relative to both non-depressed HF patients and healthy controls were detected in the left anterior parahippocampal gyrus and hippocampus (ANOVA, p=0.008 corrected for multiple comparisons) and the right posterior hippocampus and parahippocampal gyrus (p=0.005 corrected). In the overall HF group, there was a negative correlation between the severity of depressive symptoms and rCBF in the right posterior hippocampal/parahippocampal region (p=0.045 corrected). CONCLUSIONS: These findings are consistent with the notion that the medial temporal region is vulnerable to brain perfusion deficits associated with HF, and provide evidence that such functional deficits may be specifically implicated in the pathophysiology of MDD associated with HF.     

Quantification in simultaneous (99m)Tc/(123)I brain SPECT using generalized spectral factor analysis: a Monte Carlo study

In SPECT, simultaneous (99m)Tc/(123)I acquisitions allow comparison of the distribution of two radiotracers in the same physiological state, without any image misregistration, but images can be severely distorted due to cross-talk between the two isotopes. We propose a generalized spectral factor analysis (GSFA) method for solving the cross-talk issue in simultaneous (99m)Tc/(123)I SPECT. In GSFA, the energy spectrum of the photons in any pixel is expressed as a linear combination of five common spectra: (99m)Tc and (123)I photopeaks and three scatter spectra. These basis spectra are estimated from a factor analysis of all spectra using physical priors (e.g. Klein-Nishina distributions). GSFA was evaluated on (99m)Tc/(123)I Monte Carlo simulated data and compared to images obtained using recommended spectral windows (WIN) and to the gold standard (GS) images (scatter-free, cross-talk-free and noise-free). Using GSFA, activity concentration differed by less than 9% compared to GS values against differences from -23% to 110% with WIN in the (123)I and (99m)Tc images respectively. Using GSFA, simultaneous (99m)Tc/(123)I imaging can yield images of similar quantitative accuracy as when using sequential and scatter-free (99m)Tc/(123)I imaging in brain SPECT.     

Tc-99m-ECD SPECT brain imaging in children with Tourette's syndrome

We undertook this study to assess the patterns of regional cerebral perfusion (RCP) with SPECT using Technetium- 99m-ethyl cysteinate dimer (Tc-99m-ECD) in children with Tourette's Syndrome (TS), and to compare these with the patterns in a group of normal controls. The study sample consisted of 38 children (7 to 14 years) who met the ICD-10 and DSM/IV criteria for Tourette's Syndrome, and a control group of 18 children (9 to 14 years). The Children's Depression Inventory and Maudsley Obsessional-Compulsive Questionnaire were used for assessment, and the severity of motor and vocal tics were assessed using the Goetz Rating Scale. The RCP values were significantly lower in the TS group in left caudate, cingulum, right cerebellum, left dorsolateral prefrontal, and the left orbital frontal region. A positive correlation was found between the severity of vocal tics and blood flow of mid-cerebellum, right dorsolateral prefrontal and left dorsolateral prefrontal regions. Although no depressive or obsessive patients were included in the study, the depression and obsession scores were found to be negatively correlated with all RCP values, especially in the temporal regions. Further studies are needed to explore the relationship between the hypoperfusion of certain brain areas and the underlying neurophysiology and neurobiology of patients with TS. Additional disturbances such as obsessive-compulsive symptoms and depressive symptoms should also be assessed     

Technetium-99m HM-PAO SPECT in patients with delayed neurologic sequelae after carbon monoxide poisoning.

We used single photon emission computed tomography (SPECT) with technetium-99m hexamethylpropylene amine oxime (99mTc-HM-PAO) in 14 studies on 6 patients with delayed neurologic sequelae from carbon monoxide (CO) poisoning to determine whether any changes in cerebral blood flow could be correlated with clinical or computed tomographic evidence of delayed deficits. Among the six initial CT brain scans, two showed low density of both basal ganglia and two showed decreased density of the cerebral white matter. There was no correlation between the clinical outcome and the findings of the follow-up CT brain scans. Of the two SPECTS with 99mTc-HM-PAO performed during acute anoxic insult, one showed focal hypoperfusion which appeared 20 days prior to the onset of delayed neurologic sequelae after CO poisoning. Seven SPECTs in the six patients performing the delayed phase showed diffuse patched patterns of hypoperfusion which improved on follow-up images. There was good correlation between the clinical outcome and the findings of the 99mTc-HM-PAO SPECT. In preliminary conclusion, 9Tc-HM-PAO brain SPECT can be used for predicting or evaluating the outcome of delayed neurologic sequelae after CO poisoning. Cerebral vascular changes may be the possible cause of hypoperfusion in patients with CO poisoning.     

Simultaneous technetium-99m/thallium-201 SPECT imaging with model-based compensation for cross-contaminating effects.

Simultaneous acquisition of dual-isotope SPECT data offers a number of advantages over separately acquired data; however, simultaneous acquisition can result in cross-contamination between isotopes. In this work we propose and evaluate two frameworks for iterative model-based compensation of cross-contamination in dual-isotope SPECT. The methods were applied to cardiac imaging with technetium-99m-sestamibi and thallium-201, and they were compared with a subtraction-based compensation method using a cross-talk estimate obtained from an auxiliary energy window. Monte Carlo simulations were performed to carefully study aspects of bias and noise for the methods, and a torso phantom with cardiac insert was used to evaluate the performance of the methods for experimentally acquired data. The cross-talk compensation methods substantially improved lesion contrast and significantly reduced quantitative errors for simultaneously acquired data. Thallium image normalized mean square error (NMSE) was reduced from 0.522 without cross-talk compensation to as low as 0.052 with model-based cross-talk compensation. This is compared with a NMSE of 0.091 for the subtraction-based compensation method. The application of a preliminary model for cross-talk arising from lead fluorescence x-rays and collimator scatter gave promising results, and the future development of a more accurate model for collimator interactions would probably benefit simultaneous Tc/Tl imaging. Model-based compensation methods provide feasible cross-talk compensation in clinically acceptable times, and they may ultimately make simultaneous dual-isotope protocols an effective alternative for many imaging procedures.     

Model-based crosstalk compensation for simultaneous 99mTc/123I dual-isotope brain SPECT imaging

In this work, we developed a model-based method to estimate and compensate for the crosstalk contamination in simultaneous 123I and 99mTc dual isotope brain single photo emission computed tomography imaging. The model-based crosstalk compensation (MBCC) includes detailed modeling of photon interactions inside both the object and the detector system. In the method, scatter in the object is modeled using the effective source scatter estimation technique, including contributions from all the photon emissions. The effects of the collimator-detector response, including the penetration and scatter components due to high-energy 123I photons, are modeled using precalculated tables of Monte Carlo simulated point-source response functions obtained from sources in air at various distances from the face of the collimator. The model-based crosstalk estimation method was combined with iterative reconstruction based compensation to reduce contamination due to crosstalk. The MBCC method was evaluated using Monte Carlo simulated and physical phantom experimentally acquired simultaneous dual-isotope data. Results showed that, for both experimental and simulation studies, the model-based method provided crosstalk estimates that were in good agreement with the true crosstalk. Compensation using MBCC improved image contrast and removed the artifacts for both Monte Carlo simulated and experimentally acquired data. The results were in good agreement with images acquired without any crosstalk contamination.     

A methodology for generating normal and pathological brain perfusion SPECT images for evaluation of MRI/SPECT fusion methods: application in epilepsy

Quantitative evaluation of brain MRI/SPECT fusion methods for normal and in particular pathological datasets is difficult, due to the frequent lack of relevant ground truth. We propose a methodology to generate MRI and SPECT datasets dedicated to the evaluation of MRI/SPECT fusion methods and illustrate the method when dealing with ictal SPECT. The method consists in generating normal or pathological SPECT data perfectly aligned with a high-resolution 3D T1-weighted MRI using realistic Monte Carlo simulations that closely reproduce the response of a SPECT imaging system. Anatomical input data for the SPECT simulations are obtained from this 3D T1-weighted MRI, while functional input data result from an inter-individual analysis of anatomically standardized SPECT data. The method makes it possible to control the 'brain perfusion' function by proposing a theoretical model of brain perfusion from measurements performed on real SPECT images. Our method provides an absolute gold standard for assessing MRI/SPECT registration method accuracy since, by construction, the SPECT data are perfectly registered with the MRI data. The proposed methodology has been applied to create a theoretical model of normal brain perfusion and ictal brain perfusion characteristic of mesial temporal lobe epilepsy. To approach realistic and unbiased perfusion models, real SPECT data were corrected for uniform attenuation, scatter and partial volume effect. An anatomic standardization was used to account for anatomic variability between subjects. Realistic simulations of normal and ictal SPECT deduced from these perfusion models are presented. The comparison of real and simulated SPECT images showed relative differences in regional activity concentration of less than 20% in most anatomical structures, for both normal and ictal data, suggesting realistic models of perfusion distributions for evaluation purposes. Inter-hemispheric asymmetry coefficients measured on simulated data were found within the range of asymmetry coefficients measured on corresponding real data. The features of the proposed approach are compared with those of other methods previously described to obtain datasets appropriate for the assessment of fusion methods.     

99Tcm-MIBI SPECT脑显像与MRI对脑胶质瘤术后残留的与复发的对比研究

目的 探讨99Tcm—MIBI SPECT脑显像与MRI对脑胶质瘤术后残留与复发的影像特征，并客观评价两种检查方法的优缺点及诊断价值。方法 对15例正常对照者，27例脑胶质瘤术后患者（其中术后残留7例，术后复发9例，无复发者11例）行99Tcm-MIBISPECT脑显像并同时行MRI显像．对其影像学特征进行分析比较。结果正常对照者。99Tcm-MIBI SPECT显像脑实质内无核素浓聚，MRI显像未见明显异常。胶质瘤术后组（7倒残留厦9倒复发者）99Tcm-MIBI SPECT脑显像均表现为核素浓聚，其它11例无复发者表现为无核素浓聚，MRI显像表现为真阳性者8例、真阴性者7例。假阳性者4例。假阴性者8例。99Tcm-MIBI SPECT脑显像诊断胶质瘤术后残留与复发的灵敏度、准确性和特异性分别为93，7％、96．3％和100％，MR分别为31.3％、44.4％和63．6％，两者比较灵敏度、准确性有差异（P〈0．05），特异性无差异（P〉0.05）。结论 99Tcm—MIBI SPECT、脑显像对早期发现胶质瘤残留覆术后复发比MRI更优越；对分析确定胶质瘤术后残留与复发的早期诊断与治疗具有重要价值。     

Myocardial reperfusion in thrombolysis A 99Tcm-Sestamibi SPECT study in patients with acute myocardial infarction.

This study presents the outcome of myocardial scintigraphy performed before and after thrombolytic treatment in 16 patients with acute myocardial infarction using 99Tcm-Sestamibi (Cardiolite, Du Pont Scandinavia AB, Kista, Sweden). The patients were given 99Tcm-Sestamibi intravenously as soon as possible after the decision to give thrombolytic treatment. When the patients were in a clinically stable state after the thrombolytic treatment, myocardial perfusion was analysed with the gamma camera using single photon emission computerized tomography (SPECT). A second 99Tcm-Sestamibi tomography was carried out on the second to fourth day after the myocardial infarction. Data reconstruction was done with the 'Bull's eye technique'. Nine patients received thrombolysis < 3 h from the onset of pain. In this group six patients (66%) improved their myocardial perfusion by > 10% after treatment, while all seven patients who received treatment > or = 3 h after the onset of pain improved their myocardial perfusion by < 10%. This study emphasises the importance of early diagnosis and treatment of patients with acute myocardial infarction in order to salvage myocardium.     

Technetium-99m MDP bone scintigraphic findings of hypercalcemia in accelerated phase of chronic myelogenous leukemia

Hypercalcemia in accelerated phase of chronic myelogenous leukemia (CML) is very rare. Its pathogenesis is considered humoral hypercalcemia of malignancies mediated by parathyroid hormone-related protein (PTHrP). In severe hypercalcemia, calcifications in kidneys, skin, vessels, heart, and stomach may occur. Our two cases were admitted because of severe hypercalcemia in accelerated phase of CML. On Tc-99m methylene diphosphonate (MDP) bone scintigraphies, a marked tracer accumulation was seen in the lung, heart, stomach and kidney. We report increased tracer accumulation of multiple organs on Tc-99m MDP bone scintigraphy in two rare hypercalcemic patients with CML.     

Measurements of the distribution of technetium-99m sulfur colloid and technetium-99m HEDP in normal humans

Technetium-99m sulfur colloid and technetium-99m hydroxyethylidene diphosphonate (HEDP) are two radiopharmaceuticals that have been widely used in nuclear medicine. Radiation dose estimates for both materials have been published in the literature and are found in the package inserts of the commercial kits. However, these estimates were made without the benefit of quantitative human organ uptake data. Estimates of absorbed radiation dose to the kidneys differ by nearly a factor of 6 between the two calculations for HEDP. The results of this study are in agreement with the lower previous estimate. Other than that one exception, agreement of the previous estimates with the measurements reported here is surprisingly good.     

Optimal number of pinholes in multi-pinhole SPECT for mouse brain imaging--a simulation study

This study simulates a multi-pinhole single-photon emission computed tomography (SPECT) system using the Monte Carlo method, and investigates different multi-pinhole designs for quantitative mouse brain imaging. Prior approaches investigating multi-pinhole SPECT were not often optimal, as the number and geometrical arrangement of pinholes were usually chosen empirically. The present study seeks to optimize the number of pinholes for a given pinhole arrangement, and also for the specific application of quantitative neuroreceptor binding in the mouse brain. An analytical Monte Carlo simulation based method was used to generate the projection data for various count levels. A three-dimensional ordered-subsets expectation-maximization algorithm was developed and used to reconstruct the images, incorporating a realistic pinhole model for resolution recovery and noise reduction. Although artefacts arising from overlapping projections could be a major problem in multi-pinhole reconstruction, the cold-rod phantom study showed minimal loss of spatial resolution in multi-pinhole systems, compared to a single-pinhole system with the same pinhole diameter. A quantitative study of neuroreceptor binding sites using a mouse brain phantom and low activity (37 MBq) showed that the multi-pinhole system outperformed the single-pinhole system by maintaining the mean and lowering the variance in the measured uptake ratio. Multi-pinhole collimation can be used to reduce the injected dose and thereby reduce the radiation exposure to the animal. Results also suggest that the nine-pinhole configuration shown in this paper is a good choice for mouse brain imaging.     

青少年肌阵挛癫痫的临床、EEG与SPECT的研究

目的：探索青少年肌阵挛癫痫（JME）的临床、脑电图（EEG）和发作间期单光子发射断层扫描（SPECT）的特点.方法：总结40例JME病例的临床、EEG和 SPECT显像等资料.结果：年龄6～32岁.病程2周至19年,平均（4.12±3.95）年.病因：家族史7例.临床表现：有肌阵挛发作性抽动40例（100%）,兼有全面性强直阵挛发作36例（90%）,兼有失神发作12例（30%）.常规EEG检查13例,正常5例,异常8例 长程EEG监测27例（V-EEG 21例,AEEG 6例）均异常,总体异常35例（87%）.异常者中,广泛性31例（89%）,局灶性异常4例（11%） 多棘慢波31例（89%）,高波幅慢波2例（6%）.发作间期SPECT正常11例（28%）,异常29例（72%）.低灌注12例（41%）,高灌注17例（59%）.异常灌注部位41个,额叶占40%.影像学异常5%.结论： 有关JME的诊断,在把握好临床表现的基础上,长程EEG监测显得很重要,SPECT显像的额叶异常灌注灶的证据也具有重要意义.     

Dopamine transporter availability in medication free and in bupropion treated depression: a 99mTc-TRODAT-1 SPECT study

BACKGROUND: Bupropion is thought to exert its antidepressive effect by blocking the dopamine transporter (DAT). The purpose of this study was to evaluate the DAT activity in depressed patients by means of 99mTc-TRODAT-1 SPECT in relation to the efficacy of bupropion treatment. METHODS: In 12 healthy controls and 16 depressed patients the baseline DAT activity was examined. Nine of the 16 patients went through an additional second SPECT investigation, after 4 weeks of bupropion treatment. RESULTS: In the depressed patients, the baseline DAT striatum-occipital ratio (SOR) (1.04+/-.36, mean+/-SD) was not significantly different from that in the control group (1.12+/-.33) (p>.05). Correlation was found between baseline SOR and HAM-D score change (r=-.745, p=.02) of the bupropion treated patients. The average DAT occupancy due to the bupropion treatment was 20.84+/-27.7%. No significant correlation between the therapeutical effectiveness and the occupancy was observed. LIMITATIONS: One of the limiting factors of our study has been the lack of drug monitoring. CONCLUSIONS: In good agreement with other PET studies, we found 20.84% DAT occupancy during bupropion treatment. The lack of correlation between the efficacy of therapy and occupancy of DAT may raise the question as to whether other mechanisms are involved in the effect of bupropion.     

99Tcm-Tetrofosmin SPECT半定量分析诊断肺部肿瘤

目的评价^99Tc^m-Tetrofosmin SPECT半定量分析在判断肺部肿瘤良恶性的临床价值。方法对33例肺部肿块患者，行胸部^99Tc^m-Tetrofosmin显像和CT扫描，并对SPECT图像进行半定量分析。以最终的病理结果为标准，比较各组间结果。结果肺癌组的T／N值明显高于相应时相肺部良性病变组T／N值（P＜0．001）；且肺癌组断层显像的T／N值明显高于平面显像（P＜0．01）。其区分肺部原发性肿瘤良、恶性的灵敏度和准确性均高于CT（P＜0．05，P＜0．01）。肺鳞癌组和肺腺癌组的T／N值均高于小细胞肺癌组（P＜0．05）；而2h RI肺腺癌组要高于肺鳞癌组（P＜0．05）。结论^99Tc^m-Tetrofosmin SPECT半定量分析能准确、有效地探测肺部肿块，还可能为肺癌的组织类型提供更多的信息，在肺癌的诊断中具有重要的临床实用价值。     

Functional neuroimaging in epilepsy: FDG PET and ictal SPECT.

Epileptogenic zones can be localized by F-18 fluorodeoxyglucose positron emission tomography (FDG PET) and ictal single-photon emission computed tomography(SPECT). In medial temporal lobe epilepsy, the diagnostic sensitivity of FDG PET or ictal SPECT is excellent, however, the sensitivity of MRI is so high that the incremental sensitivity by FDG PET or ictal SPECT has yet to be proven. When MRI findings are ambiguous or normal, or discordant with those of ictal EEG, FDG PET and ictal SPECT are helpful for localization without the need for invasive ictal EEG. In neocortical epilepsy, the sensitivities of FDG PET or ictal SPECT are fair. However, because almost a half of the patients are normal on MRI, FDG PET and ictal SPECT are helpful for localization or at least for lateralization in these non-lesional epilepsies in order to guide the subdural insertion of electrodes. Interpretation of FDG PET has been recently advanced by voxel-based analysis and automatic volume of interest analysis based on a population template. Both analytical methods confirmed the performance of previous visual interpretation results. Ictal SPECT was analyzed using subtraction methods(coregistered to MRI) and voxel-based analysis. Rapidity of injection of tracers, HMPAO versus ECD, and repeated ictal SPECT, which remain the technical issues of ictal SPECT, are detailed.