Artificial neural network classifier for the diagnosis of Parkinson's disease using [99mTc]TRODAT-1 and SPECT

Imaging the dopaminergic neurotransmitter system with positron emission tomography (PET) or single photon emission tomography (SPECT) is a powerful tool for the diagnosis of Parkinson's disease (PD). Previous studies have indicated that human observers have a diagnostic accuracy similar to conventional ROI analysis of SPECT imaging data. Consequently, it has been hypothesized that an artificial neural network (ANN), which can mimic the pattern recognition skills of human observers, may provide similar results. A set of patients with PD, and normal healthy control subjects, were studied using the dopamine transporter tracer [(99m)Tc]TRODAT-1 and SPECT. The sample was comprised of 81 patients (mean age +/- SD: 63.4 +/- 10.4 years; age range: 39.0-84.2 years) and 94 healthy controls (mean age +/- SD: 61.8 +/- 11.0 years; age range: 40.9-83.3 years). The images were processed to extract the striatum and the striatal pixel values were used as inputs to a three-layer ANN. The same set of data was used to both train and test the ANN, in a 'leave one out' procedure. The diagnostic accuracy of the ANN was higher than any previous analysis method applied to the same data (94.4% total accuracy, 97.5% specificity and 91.4% sensitivity). However, it should be stressed that, as with all applications of an ANN, it was difficult to interpret precisely what triggers in the images were being detected by the network.     

Temporal lobe asymmetry with iofetamine (IMP) SPECT imaging in patients with major depression.

Single photon emission computed tomography (SPECT) brain imaging with 123I labeled iofetamine (IMP) has been used to study several neuropsychiatric disorders. However, little attention has been given to patients with major depression. In the present study IMP SPECT images were obtained on 19 depressed patients and 12 medical comparison subjects who had no focal abnormalities on MRI or CT scans. 5 mCi of 123I IMP was administered intravenously and SPECT images were obtained using a GE Starcamm 2000 SPECT system. After standard reconstruction of the images, an automated region of interest (ROI) computer program was applied to each tomographic brain image. Coronal images were then used to analyze lateralized differences in IMP activity. Measurements were made of the mean IMP activity per pixel, the maximum activity per pixel, and the ratio of the mean activity per pixel in the ROI to that of the cerebellum. On visual inspection, 12 out of 19 depressed patients (63%) and only of 12 medical comparison patients (8%) appeared to have substantially increased IMP activity in the right temporal lobe (P less than 0.005). But semi-quantitative analysis showed that while IMP activity was greater in the right than the left temporal lobe of depressed patients (P less than 0.0001), it was also present in medical comparison patients (P less than 0.01). Although there was no difference in the frequency of asymmetry between groups, it was more pronounced in depressed patients. These data suggest that asymmetric temporal lobe activity on IMP SPECT images may be of potential diagnostic utility in some patients with affective disorders.     

Reproducibility of dynamic contrast-enhanced MRI in human muscle and tumours: comparison of quantitative and semi-quantitative analysis

The purpose of this study was to determine the reproducibility of dynamic contrast-enhanced (DCE)-MRI and compare quantitative kinetic parameters with semi-quantitative methods, and whole region-of-interest (ROI) with pixel analysis. Twenty-one patients with a range of tumour types underwent paired MRI examinations within a week, of which 16 pairs were evaluable. A proton density-weighted image was obtained prior to a dynamic series of 30 T(1)-weighted spoiled gradient echo images every 11.9 s with an intravenous bolus of gadopentetate dimeglumine given after the third baseline data point. Identical ROIs around the whole tumour and in skeletal muscle were drawn by the same observer on each pair of examinations and used for the reproducibility analysis. Semi-quantitative parameters, gradient, enhancement and AUC (area under the curve) were derived from tissue enhancement curves. Quantitative parameters (K(trans), k(ep), v(e)) were obtained by the application of the Tofts' model. Analysis was performed on data averaged across the whole ROI and on the median value from individual pixels within the ROI. No parameter showed a significant change between examinations. For all parameters except K(trans), the variability was not dependent on the parameter value, so the absolute values for the size of changes needed for significance should be used for future reference rather than percentages. The size of change needed for significance in a group of 16 in tumours for K(trans), k(ep) and v(e) was -14 to +16%, -0.20 ml/ml/min (15%) and -1.9[?]ml/ml (6%), respectively (pixel analysis), and -16 to +19%, -0.23 ml/ml/min (16%) and +/- 1.9[?]ml/ml (6%) (whole ROI analysis). For a single tumour, changes greater than -45 to +83%, +/- 0.78 ml/ml/min (60%) and +/- 7.6 ml/ml (24%), respectively, would be significant (pixel analysis). For gradient, enhancement and AUC the size of change needed for significance in tumours was -0.24 (17%), -0.05 (6%) and -0.06 (8%), respectively for a group of 16 (pixel analysis), and +/- 0.96 (68%), +/- 0.20 (25%) and +/- 0.22 (32%) for individuals. In muscle, the size of change needed for significance in a group of 16 for K(trans), k(ep) and v(e) was -30 to +44%, +/- 0.81 ml/ml/min (61%) and +/- 1.7 ml/ml (13%). For gradient, enhancement and AUC it was +/- 0.09 (20%), +/- 0.02 (8%) and +/- 0.03 (12%). v(e), enhancement and AUC are highly reproducible DCE-MRI parameters. K(trans), k(ep) and gradient have greater variability, with larger changes in individuals required to be statistically significant, but are nevertheless sufficiently reproducible to detect changes greater than 14-17% in a cohort of 16 patients. Pixel analyses slightly improve reproducibility estimates and retain information about spatial heterogeneity. Reproducibility studies are recommended when treatment effects are being monitored.     

Rapid calculation of detectability in Bayesian single photon emission computed tomography

We consider the calculation of lesion detectability using a mathematical model observer, the channelized Hotelling observer (CHO), in a signal-known-exactly/background-known-exactly detection task for single photon emission computed tomography (SPECT). We focus on SPECT images reconstructed with Bayesian maximum a posteriori methods. While model observers are designed to replace time-consuming studies using human observers, the calculation of CHO detectability is usually accomplished using a large number of sample images, which is still time consuming. We develop theoretical expressions for a measure of detectability, the signal-to-noise-ratio (SNR) of a CHO observer, that can be very rapidly evaluated. Key to our expressions are approximations to the reconstructed image covariance. In these approximations, we use methods developed in the PET literature, but modify them to reflect the different nature of attenuation and distance-dependent blur in SPECT. We validate our expressions with Monte Carlo methods. We show that reasonably accurate estimates of the SNR can be obtained at a computational expense equivalent to approximately two projection operations, and that evaluating SNR for subsequent lesion locations requires negligible additional computation.     

Increased muscle activity during rapid eye movement sleep correlates with decrease of striatal presynaptic dopamine transporters. IPT and IBZM SPECT imaging in subclinical and clinically manifest idiopathic REM sleep behavior disorder,Parkinson's disease,and controls

STUDY OBJECTIVES: Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by complex behavior during REM sleep. The etiology of this disorder is still unknown, but a recent study showed that RBD precedes symptoms of Parkinson disease (PD) by several years, and in a previous study, we found reduced striatal dopamine transporters in idiopathic clinically manifest RBD. DESIGN: Hypothesizing that subclinical RBD shows a less severe reduction of striatal dopamine transporters than clinically manifest RBD, we studied striatal postsynaptic dopamine D2-receptors with (S)-2hydroxy-3iodo-6-methoxy-([1-ethyl-2-pyrrolidinyl]methyl) benzamide labeled with iodine 123 (IBZM) and the striatal presynaptic dopamine transporters with (N)-(3-iodopropene-2-yl)-2beta-carbomethoxy-3beta-(4-chlorophenyl) tropane labeled with iodine 123 (IPT) using single-photon emission computed tomography (SPECT) in the following groups: 8 patients with idiopathic subclinical RBD, 8 patients with idiopathic clinically manifest RBD, 11 controls, and 8 patients with PD stage Hoehn & Yahr I. RESULTS: The IPT uptake was highest in controls. There was a significant decrease in IPT uptake from controls to patients with subclinical RBD, from patients with subclinical RBD to clinically manifest RBD, and from patients with clinically manifest RBD to patients with PD (controls: right = 4.07 +/- 0.29, left = 4.07 +/- 0.30; subclinical RBD: right = 3.56 +/- 0.21, left = 3.55 +/- 0.25; clinically manifest RBD: right = 3.18 +/- 0.43, left = 3.2 +/- 0.43; PD: ipsilateral to the clinically affected body side = 3.25 +/- 0.35, contralateral to the clinically affected body side = 2.51 +/- 0.28). Muscle activity during REM sleep lasting persistently longer than 0.5 seconds was independently associated with reduction of striatal dopamine transporters (P = 0.001). The IBZM uptake was not significantly different between the groups. CONCLUSIONS: This study suggests that there is a continuum of reduced striatal dopamine transporters involved in the pathophysiologic mechanisms causing increased muscle activity during REM sleep in patients with subclinical RBD.     

Sequential and simultaneous dual-isotope brain SPECT: comparison with PET for estimation and discrimination tasks in early Parkinson disease

Parkinson disease (PD) is the second most frequently occurring cerebral degenerative disease, after Alzheimer disease. Treatments are available, but their efficacy is diminished unless they are administered in the early stages. Therefore, early identification of PD is crucial. In addition to providing perfectly registered studies, simultaneous 99mTc/123I imaging makes possible the assessment of pre- and postsynaptic neurotransmission functions under identical physiological conditions, while doubling the number of counts for the same total imaging time. These advantages are limited, however, by cross talk between the two radionuclides due to the close emission energies of 99mTc (140 keV) and 123I (159 keV). PET, on the other hand, provides good temporal and spatial resolution and sensitivity but usually requires the use of a single radionuclide. In the present work, the authors compared brain PET with sequential and simultaneous dual-isotope SPECT for the task of estimating striatal activity concentration and striatal size for a normal brain and two stages of early PD. Realistic Monte Carlo simulations of a time-of-flight PET scanner and gamma cameras were performed while modeling all interactions in the brain, collimator (gamma camera) and crystal (detector block in PET), as well as population biological variability of pre- and postsynaptic uptake. For SPECT imaging, we considered two values of system energy resolution and scanners with two and three camera heads. The authors used the Cramer-Rao bound, as a surrogate for the best theoretical performance, to optimize the SPECT acquisition energy windows and objectively compare PET and SPECT. The authors determined the discrimination performance between 500 simulated subjects in every disease stage as measured by the area under the ROC curve (AUC). The discrimination accuracy between a normal subject and a subject in the prodromal disease stage was AUC = 0.924 with PET, compared to 0.863 and 0.831 with simultaneous and sequential SPECT, respectively. The significant improvement in performance obtained with simultaneous dual-isotope SPECT compared to sequential imaging (p = 0.019) was due primarily to the increased number of counts detected and resulted in comparable performance when performing simultaneous SPECT on a two-head camera with 9.2% energy resolution to that obtained with sequential SPECT on a three-head camera with 6.2% energy resolution.     

Non-invasive measurement of brain viscoelasticity using magnetic resonance elastography

The purpose of this work was to develop magnetic resonance elastography (MRE) for the fast and reproducible measurement of spatially averaged viscoelastic constants of living human brain. The technique was based on a phase-sensitive echo planar imaging acquisition. Motion encoding was orthogonal to the image plane and synchronized to intracranial shear vibrations at driving frequencies of 25 and 50 Hz induced by a head-rocker actuator. Ten time-resolved phase-difference wave images were recorded within 60 s and analyzed for shear stiffness and shear viscosity. Six healthy volunteers (six men; mean age 34.5 years; age range 25-44 years) underwent 23-39 follow-up MRE studies over a period of 6 months. Interindividual mean +/- SD shear moduli and shear viscosities were found to be 1.17 +/- 0.03 kPa and 3.1 +/- 0.4 Pas for 25 Hz and 1.56 +/- 0.07 kPa and 3.4 +/- 0.2 Pas for 50 Hz, respectively (P < or = 0.01). The intraindividual range of shear modulus data was 1.01-1.31 kPa (25 Hz) and 1.33-1.77 kPa (50 Hz). The observed modulus dispersion indicates a limited applicability of Voigt's model to explain viscoelastic behavior of brain parenchyma within the applied frequency range. The narrow distribution of data within small confidence intervals demonstrates excellent reproducibility of the experimental protocol. The results are necessary as reference data for future comparisons between healthy and pathological human brain viscoelastic data.     

Computer aided detection of masses in mammography using subregion Hotelling observers

We propose to investigate the use of the subregion Hotelling observer for the basis of a computer aided detection scheme for masses in mammography. A database of 1320 regions of interest (ROIs) was selected from the DDSM database collected by the University of South Florida using the Lumisys scanner cases. The breakdown of the cases was as follows: 656 normal ROIs, 307 benign ROIs, and 357 cancer ROIs. Each ROI was extracted at a size of 1024 x 1024 pixels and sub-sampled to 128 x 128 pixels. For the detection task, cancer and benign cases were considered positive and normal was considered negative. All positive cases had the lesion centered in the ROI. We chose to investigate the subregion Hotelling observer as a classifier to detect masses. The Hotelling observer incorporates information about the signal, the background, and the noise correlation for prediction of positive and negative and is the optimal detector when these are known. For our study, 225 subregion Hotelling observers were set up in a 15 x 15 grid across the center of the ROIs. Each separate observer was designed to "observe," or discriminate, an 8 x 8 pixel area of the image. A leave one out training and testing methodology was used to generate 225 "features," where each feature is the output of the individual observers. The 225 features derived from separate Hotelling observers were then narrowed down by using forward searching linear discriminants (LDs). The reduced set of features was then analyzed using an additional LD with receiver operating characteristic (ROC) analysis. The 225 Hotelling observer features were searched by the forward searching LD, which selected a subset of 37 features. This subset of 37 features was then analyzed using an additional LD, which gave a ROC area under the curve of 0.9412 +/- 0.006 and a partial area of 0.6728. Additionally, at 98% sensitivity the overall classifier had a specificity of 55.9% and a positive predictive value of 69.3%. Preliminary results suggest that using subregion Hotelling observers in combination with LDs can provide a strong backbone for a CAD scheme to help radiologists with detection. Such a system could be used in conjunction with CAD systems for false positive reduction.     

Receiver operating characteristic and location analysis of simulated near-infrared tomography images

Receiver operating characteristic (ROC) analysis was performed on simulated near-infrared tomography images, using both human observer and contrast-to-noise ratio (CNR) computational assessment, for application in breast cancer imaging. In the analysis, a nonparametric approach was applied for estimating the ROC curves. Human observer detection of objects had superior capability to localize the presence of heterogeneities when the objects were small with high contrast, with a minimum detectable threshold of CNR near 3.0 to 3.3 in the images. Human observers were able to detect heterogeneities in the images below a size limit of 4 mm, yet could not accurately find the location of these objects when they were below 10 mm diameter. For large objects, the lower limit of a detectable contrast limit was near 10% increase relative to the background. The results also indicate that iterations of the nonlinear reconstruction algorithm beyond 4 did not significantly improve the human detection ability, and degraded the overall localization ability for the objects in the image, predominantly by increasing the noise in the background. Interobserver variance performance in detecting objects in these images was low, suggesting that because of the low spatial resolution, detection tasks with NIR tomography is likely consistent between human observers.     

Reduced cerebral blood flow during wakefulness in obstructive sleep apnea-hypopnea syndrome

STUDY OBJECTIVES: To investigate changes in regional cerebral blood flow (rCBF) in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). DESIGN: We compared the 99mTc-ethylcysteinate dimer (ECD) single photon emission computed tomography (SPECT) images of patients with OSAHS with those of age- and sex-matched healthy volunteers. SETTING: University hospital. PATIENTS AND PARTICIPANTS: Twenty-seven patients with severe OSAHS and 27 healthy volunteers underwent 99mTc-ECD brain SPECT studies. INTERVENTION: For statistical parametric mapping analysis, all SPECT images were spatially normalized to the standard SPECT template and then smoothed using a 14-mm full-width at half-maximum Gaussian kernel. The Student t test was used for the statistical analysis. MEASUREMENTS AND RESULTS: The mean age of patients and subjects was 44.3 years (range 31-58). All patients underwent overnight polysomnography. The mean apnea-hypopnea index of patients was 60.4 +/- 17.6 per hour (range 33 -104), indicating severe OSAHS. All patients snored heavily and had daytime sleepiness (mean Epworth Sleepiness Scale score, 10.7 +/- 3.7, range 6-12). Statistical parametric mapping analysis showed that rCBF in patients with OSAHS was significantly reduced in bilateral parahippocampal gyri and in the right lingual gyrus, as compared with that of healthy volunteers (P < 0.05 with false discovery rate correction). Moreover, apnea-hypopnea indexes of patients were negatively correlated with rCBF in the right pericentral gyrus and right cuneus at uncorrected P < 0.001. CONCLUSIONS: Our results show the altered rCBF pattern in bilateral parahippocampal gyri, right lingual gyrus, pericentral gyrus, and cuneus in patients with severe OSAHS. These findings may partly explain the deficit in memory, spatial learning, executive function, and attention, which are frequently found in patients with OSAHS.     

Different patterns of nigrostriatal degeneration in tremor type versus the akinetic-rigid and mixed types of Parkinson's disease at the early stages: molecular imaging with 123I-FP-CIT SPECT

The various associations of motor and non-motor symptoms, the onset of motor complications, the cognitive disorder's appearance and other factors make Parkinson's disease (PD) a heterogeneous syndrome with multiple phenotypes. The necessity of discriminating between different forms of PD could have a role in understanding the pathophysiology of extrapyramidal signs with clinical implications. The aim of this study was to evaluate if there is a relationship between the clinical motor phenotypes of PD and the scintigraphic pattern of 123I-FP-CIT single photon emission computed tomography (SPECT). We examined 47 patients with early idiopathic PD (25 males; 22 females; mean age 58±2 years) and subdivided them in different clinical forms on the basis of dominance of resting tremor (n=20), bradykinesia plus rigidity (n=20) and the presence of both clinical signs [mixed type (MT, n=7)]. We correlated this status with the semi-quantitative analysis of SPECT with 123I-FP-CIT. Tremor type patients showed a lower reduction of 123I-FP-CIT uptake compared to akinetic-rigid type patients in contralateral caudate (P=0.0139) and putamen (P=0.0028) nuclei. 123I-FP-CIT uptake was higher in the ipsilateral caudate (P=0.0050) and putamen (P=0.0012) of tremor type patients compared to akinetic-rigid type patients. Comparisons of the striatal uptake in the tremor type and akinetic-rigid type patients with the MT patients revealed significant differences only in the ipsilateral and contralateral caudate. Our data indicate that in akinetic-rigid patients the dopaminergic system is more involved compared to that in the tremor type patients and that this difference is present from the initial stage of the disease. Moreover, our results suggest that PD phenotypes could be related not only to the dopaminergic involvement but also to other systems.     

Breathing and locomotion in patients with Parkinson's disease

The phase relationship between respiration and locomotion was examined in ten patients with Parkinson's disease (PD, mean age 65, range 51-79 years) and in six healthy subjects (mean age 63, range 58-68 years). Locomotion was measured by means of pressure sensors attached below the subjects' feet. Respiration was measured using respiratory inductive plethysmography. The data were recorded with a battery-driven portable device. We determined the coordination degree as the portion of steps which occurred within 12/50 bins of the respiratory cycle. The mean degree of coordination of PD patients was 45.0%+/-11.9%, for the healthy subjects 85.1%+/-10.8% (P<0.001). Three healthy subjects showed a 2:1 ratio between step and breathing rate, three a 3:2 ratio. Two PD patients showed a coordination of 4:1 and 3:1, respectively, with a larger scatter than in controls. In the other eight patients steps were almost equally distributed over the entire respiratory cycle. We conclude that in patients with PD the coordination between locomotion and breathing is reduced.     

Low brain-derived neurotrophic factor (BDNF) levels in serum of Huntington's disease patients.

Huntington's disease (HD) is a neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms and by a progressive degeneration of neurons in basal ganglia and in brain cortex. Brain-derived neurotrophic factor (BDNF) is a pro-survival factor for striatal neurons. Some evidence implicates a brain BDNF deficiency, related to mutated huntingtin expression, in the selective vulnerability of striatal neurons in HD. We compared BDNF serum levels in 42 patients with HD (range 28-72 years, mean age 51.9 +/- 11.5), and 42 age-matched healthy subjects (range 25-68 years, mean age 48.2 +/- 12.5). We evaluated the potential relationship between BDNF serum levels, CAG repeat number (range 40-54, mean 44.8 +/- 3.4) and duration of illness (range 6-228 months, mean 103.6 +/- 62.1). Serum BDNF levels were significantly lower in patients than in age-matched healthy subjects. Lower BDNF levels were associated with a longer CAG repeat length and a longer duration of illness. Severity of the illness, as assessed by the Unified Huntington's Disease Rating Scale (UHDRS) motor and cognitive scores, was negatively related to serum BDNF levels. These results in vivo confirm that the huntingtin mutation causes BDNF production to decline and show that the BDNF deficiency is detectable in HD patients' sera. Further studies on a larger sample size should confirm whether BDNF concentrations in patients' serum could be a useful clinical marker related to the patients' disease phenotype.     

Acute effect of intranasal estrogen on cerebral and cerebellar perfusion in postmenopausal women

OBJECTIVES: Estrogen action in the brain influences many neurochemical processes. The aim of the study was to evaluate the acute effect of intranasal 17beta-estradiol on cerebral and cerebellar perfusion in postmenopausal women. METHODS: The study group included 24 healthy postmenopausal women who had been in natural menopause for at least 1 year (mean age: 47.38+/-5.9 years). We conducted an experimental, randomized, placebo-controlled, cross-over, double-blind study. Cerebral and cerebellar perfusion was measured after placebo (saline serum physiologic) or intranasal 17beta-estradiol administration by Single Photon Emission Computed Tomography (SPECT) using technetium-99m-hexamethylpropylene amine oxime (Tc99m-HMPAO). Regions of interest (ROIs) were drawn manually. Cerebral and cerebellar perfusions were calculated for each ROI using average number of counts per pixel. Semiquantitative analysis was performed in bilateral frontal, temporal, parietal and occipital lobes, thalamus, putamen, hippocampus, amygdala, caudate nuclei, cerebellar region, anterior/posterior of cingulate gyrus and pons. RESULTS: After intranasal 17beta-estradiol administration, SPECT study revealed significant increases in cerebral and cerebellar perfusion compared to placebo measurements in all studied slices (p<0.05). There was a positive correlation between serum estrogen levels after 17beta-estradiol and cerebral and cerebellar perfusion. CONCLUSIONS: Administration of single dose intranasal 17beta-estradiol increases cerebral and cerebellar perfusions in healthy postmenopausal women.     

Glutathione S-transferase polymorphisms and onset age in alpha-synuclein A53T mutant Parkinson's disease.

Monogenic forms of Parkinson's disease (PD) provide an opportunity to examine mechanisms underlying phenotypic variation. Glutathione S-transferase (GST) has detoxification and antioxidative functions. To screen genetic variations in GST for an effect on the onset age (OA) of PD, we typed seven common genetic polymorphisms in five GST isoenzymes, M1, M3, P1, T1, and Z1, in 36 affected individuals of Italian or Greek origin with the alpha-synuclein A53T (PARK1) mutation. Mean OA was 45.2 years with a wide SD of 11.03 years, similar to that of idiopathic PD. Our allelic analysis showed that the subjects homozygous for the GSTP1 G-for-A nucleotide substitution at position 313 had a mean OA acceleration of 15.2 years (31.3 +/- 7.09 years, n = 3 vs. 46.5 +/- 10.50 years, n = 33, P = 0.020). The GSTP1 C341T substitution was associated with a 9.7-year acceleration of OA, but the significance was borderline (36.4 +/- 8.35 years vs. 46.7 +/- 10.85 years, P = 0.0519). After correction for the five genes examined, both results lose statistical significance. Nevertheless, our results suggest that further investigation in GSTP1 variants and PD pathogenesis is warranted in sporadic PD and that a search for toxins that accelerate PD OA should pay particular attention to GST-P1 substrates.     

联合图像专家组2000图像压缩方法的核医学应用研究

为研究联合图像专家组2000(Jo in t Photograph ic Expert G roup 2000,JPEG 2000)图像压缩方法在核医学中的应用,将无病变和有病变核医学静态图像用JPEG 2000软件压缩。对无损压缩图像,测量其压缩比。对有损压缩图像,由医生阅片,根据其结论作接收器操作特性(R ece iver operating characteristic,ROC)分析,获得各种图像压缩比的ROC曲线下的面积(A rea under curve,AUC),以其大小评价图像诊断质量;并将原始图像组AUC与各有损压缩图像组的AUC作配对t检验。实验发现,无损压缩的图像压缩比为(1.34±0.05)∶1。而有损压缩比越大,AUC越小。原始图像与压缩图像比较,压缩比为10∶1时没有显著性差异,压缩比更大时则有显著性差异。实验结果表明,无损压缩方法压缩比低,实用意义不大。有损压缩比不大于10∶1时,核医学静态图像的诊断质量得以保留。对核医学中的其它图像形式,可根据的图像性质,特别是固有统计噪声的大小,适当增减压缩比。     

A rapid ELISA-based serum assay for myelin basic protein in multiple sclerosis

We have developed a sensitive, ELISA-based assay to detect autoantibodies to myelin basic protein (MBP) in human serum. Autoantibody levels were measured in 98 normal healthy adults (age range 20-66) and 94 clinically definite multiple sclerosis (MS) cases (age range 18-63). Of the MS patients, 77% had elevated levels of MBP autoantibodies (IgG) whereas only five normal individuals had antibody levels increased over normal. From the receiver-operator curve (ROC), the mean+/-2SD as clinical decision limit offers high sensitivity (77%) and specificity (95%). No change in assay performance was observed when hemoglobin, triglycerides or bilirubin were added to serum samples. The success of the assay is dependent on the use of heparin, an anionic molecule, which neutralizes the positive charge on the highly cationic MBP.     

Experimental determination of subjective similarity for pairs of clustered microcalcifications on mammograms: observer study results

Presentation of images of lesions similar to that of an unknown lesion might be useful to radiologists in distinguishing between benign and malignant clustered microcalcifications on mammograms. Investigators have been developing computerized schemes to select similar images from large databases. However, whether selected images are really similar in appearance is not examined for most of the schemes. In order to retrieve images that are useful to radiologists, the selected images must be similar from radiologists' diagnostic points of view. Therefore, in this study, the data of radiologists' subjective similarity for pairs of clustered microcalcification images were obtained from a number of observers, and the intra- and inter-observer variations and the intergroup correlations were determined to investigate whether reliable similarity ratings by human observers can be determined. Nineteen images of clustered microcalcifications, each of which was paired with six other images, were selected for the observer study. Thus, subjective similarity ratings for 114 pairs of clustered microcalcifications were determined by each observer. Thirteen breast, ten general, and ten nonradiologists participated in the observer study; some of them completed the study multiple times. Although the intraobserver variations for the individual readings and the interobserver variations for pairs of observers were not small, the interobserver agreements were improved by taking the average of readings by the same observers. When the similarity ratings by a number of observers were averaged among the groups of breast, general, and nonradiologists, the mean differences of the ratings between the groups decreased, and good concordance correlations (0.846, 0.817, and 0.785) between the groups were obtained. The result indicates that reliable similarity ratings can be determined by use of this method, and the average similarity ratings by breast radiologists can be considered meaningful and useful for the development and evaluation of a computerized scheme for selection of similar images.     

Association between salivary levels of chromogranin A and periodontitis in older Japanese

The relationship between periodontitis and stress-related hormones is poorly understood. In this cross-sectional study we investigated the associations between the stress-related hormone, chromogranin A (CgA) and periodontitis in healthy community-dwelling elderly subjects aged 60 years old and older. A total of 171 subjects (85 males, 86 females; mean age of 68.4 +/- 4.46 (SD) years old) participated, all of whom were living independently. Stimulated whole saliva samples were collected and CgA levels were determined, while a medical questionnaire regarding medical conditions and lifestyle was also administered. Clinical examinations included probing depth (PD), bleeding on probing (BOP), and clinical attachment loss (CAL). When the subjects were divided into two groups based on periodontitis severity, the salivary CgA levels were significantly higher in subjects with severe PD or CAL. Multiple regression analysis showed that higher CgA level was significantly associated with greater numbers of teeth with severe PD or CAL, after adjusting for confounding variables. In this first known report of the association between CgA level and periodontitis, our results suggest a close relationship between the extent and severity of periodontitis and salivary level of CgA in healthy elderly subjects.     

Dopamine transporter availability in symptomatic depressed patients with seasonal affective disorder and healthy controls.

BACKGROUND: During recent years hypotheses about the pathophysiology of seasonal affective disorder/winter type (SAD) have focused monoaminergic mechanisms. There is substantial evidence that serotonergic systems play an important role. The potential role of catecholaminergic pathways has not been fully explored. METHODS: Eleven drug-free, symptomatic depressed patients with SAD and 11 healthy age- and gender-matched healthy controls were invited to participate in a 123Ibeta-CIT single photon emission computed tomography (SPECT) study to assess striatal density of dopamine transporters (DATs). The cerebellum was used as reference region. Ratios were calculated between mean counts in left and right striatum and cerebellum. These ratios minus I represent specific/non-displaceable binding and are assumed to be directly related to DAT availability at the time of binding equilibrium. RESULTS: Displaceable 153Ibeta-CIT binding in the area corresponding to the left striatum was significantly reduced in SAD patients compared to healthy controls (10.49+/-0.91 v. 1195+/-1.54, respectively; 2-tailed P = 0.017, Mann-Whitney U test). CONCLUSIONS: These data suggest reductions in the availability of striatal DAT binding sites in untreated symptomatic depressed SAD patients. It remains unclear whether these reductions represent a primary defect or an attempt to overcome a state of possible lowered dopamine availability in the synaptic cleft during a depressive episode of SAD. However, these findings provide evidence that brain dopaminergic systems may be involved in the pathophysiology of SAD.