A combined reconstruction-classification method for diffuse optical tomography.

We present a combined classification and reconstruction algorithm for diffuse optical tomography (DOT). DOT is a nonlinear ill-posed inverse problem. Therefore, some regularization is needed. We present a mixture of Gaussians prior, which regularizes the DOT reconstruction step. During each iteration, the parameters of a mixture model are estimated. These associate each reconstructed pixel with one of several classes based on the current estimate of the optical parameters. This classification is exploited to form a new prior distribution to regularize the reconstruction step and update the optical parameters. The algorithm can be described as an iteration between an optimization scheme with zeroth-order variable mean and variance Tikhonov regularization and an expectation-maximization scheme for estimation of the model parameters. We describe the algorithm in a general Bayesian framework. Results from simulated test cases and phantom measurements show that the algorithm enhances the contrast of the reconstructed images with good spatial accuracy. The probabilistic classifications of each image contain only a few misclassified pixels.

Significance of background optical properties, time-resolved information and optode arrangement in diffuse optical imaging of term neonates.

The significance of accurate knowledge of background optical properties and time-resolved information in reconstructing images of hemodynamic changes in the neonatal brain from diffuse optical imaging data was studied using Monte Carlo (MC) simulation. A segmented anatomical magnetic resonance (MR) image and literature-derived optical properties for each tissue type were used to create a voxel-based anatomical model. Small absorbing perturbations were introduced into the anatomical model to simulate localized hemodynamic responses related to brain activation. Perturbation MC (pMC) was used as the primary method of image reconstruction. For comparison, reconstructions were also performed using the finite element method (FEM) to solve the diffusion approximation (DA) to the radiative transfer equation (RTE). The effect of optode layout was investigated using three different grids. Of the factors studied, the density of the optode grid was found to have the greatest effect on image quality. The use of time-resolved information significantly improved the spatial accuracy with all optode grids. Adequate knowledge and modeling of the optical properties of the background was found to significantly improve the spatial accuracy of the reconstructed images and make the recovery of contrast of absorption changes more consistent over simplified modeling. Localization accuracy of small perturbations was found to be 2-3 mm with accurate a priori knowledge of the background optical properties, when a grid with high optode density (>1 optode cm(-2)) was used.

An adaptive smoothness regularization algorithm for optical tomography.

In diffuse optical tomography (DOT), the object with unknown optical properties is illuminated with near infrared light and the absorption and diffusion coefficient distributions of a body are estimated from the scattering and transmission data. The problem is notoriously ill-posed and complementary information concerning the optical properties needs to be used to counter-effect the ill-posedness. In this article, we propose an adaptive inhomogenous anisotropic smoothness regularization scheme that corresponds to the prior information that the unknown object has a blocky structure. The algorithm updates alternatingly the current estimate and the smoothness penalty functional, and it is demonstrated with simulated data that the algorithm is capable of locating well blocky inclusions. The dynamical range of the reconstruction is improved, compared to traditional smoothness regularization schemes, and the crosstalk between the diffusion and absorption images is clearly less. The algorithm is tested also with a three-dimensional phantom data.

Prevalence of disability in three birth cohorts at old age over time spans of 10 and 20 years.

The prevalence of disability at the age of 75+ measured by the Katz Index of Activities of Daily Living (ADL) was compared among three birth cohorts: those born < or = 1903 (n = 348), those born < or = 1913 (n = 586), and those born < or = 1923 (n = 758). Significant risk factors for disability were female sex and age; the cohort effect was not significant. The prevalence rates of disability were 29.0% (95% CI 24.2-33.8), 34.8% (30.9-38.7), and 28.8% (25.5-32.0) for the first, second, and third cohorts. In the age group 75-79 years the rates were 20.1% (95% CI 13.8-26.4), 25.5% (20.2-30.7), and 14.4% (10.6-18.1). The change was due to the declining disability of women. The distributions in the three cohorts based on the numbers of ADL limitations did not differ. As far as the whole aged populations were concerned, longer life was not accompanied by improving health.

Domains and determinants of quality of life after stroke caused by brain infarction.

OBJECTIVE: To evaluate the domain-specific quality of life (QOL), including physical, social and role functioning, mental health, vitality, bodily pain, and general health domains, and to assess QOL's clinical and sociodemographic correlates in patients who were disabled by ischemic stroke. DESIGN: One-year prospective study of an inception cohort of patients with first-ever brain infarction. SETTING: Stroke unit of a neurologic department of a university hospital. PATIENTS: Eighty-five consecutive patients (36 women, 49 men; mean age +/- SD, 65+/-12.5 yr) with first-ever stroke of a mild to moderate nature caused by brain infarction. MAIN OUTCOME MEASURES: Patients were examined at 3 and 12 months poststroke. QOL was measured using the RAND 36-Item Health Survey. The variables studied were lateralization of cerebral lesion, neurologic and functional status, depression, age, gender, marital status, and living conditions. Depression was evaluated according to the criteria of Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition. Neurologic impairment was assessed by Scandinavian Stroke Scale, performance in activities of daily living by the Barthel index, and the intellectual deterioration by the Mini-Mental State Examination. RESULTS: QOL was poorer for the patients with mild to moderate stroke impairments at 3 months poststroke. The test domains most prone to being affected were physical functioning, physical role limitations, vitality, and general health. Only the domains of physical functioning and physical role limitations improved during the follow-up at 1 year. Depression, although mostly minor, was the most important reason for impaired QOL. Depression, being married, and age emerged as significant independent contributors to the low score value of vitality. Depression and being married were related to the low score value of physical role limitations. CONCLUSIONS: Stroke affects QOL, impairing its physical and psychosocial domains. The most important determinants of low QOL seem to be depression and being married. These findings provide new challenges for stroke rehabilitation, calling for identification of patients and spouses in need of supportive services.

Aphasia, depression, and non-verbal cognitive impairment in ischaemic stroke.

Aphasia, depression, and cognitive dysfunction are common consequences of stroke, but knowledge of their interrelationship is limited. This 1-year prospective study was designed to evaluate prevalence and course of post-stroke aphasia and to study its psychiatric, neurological, and cognitive correlates. We studied a series of 106 consecutive patients (46 women and 60 men, mean age 65. 8 years) with first-ever ischaemic brain infarction. The patients were clinically examined, and presence and type of aphasia were evaluated during the 1st week after stroke and 3 and 12 months later. Psychiatric and neuropsychological evaluations were performed 3 and 12 months after stroke. Aphasia was diagnosed in 34% of the patients during the acute phase, and two thirds of them remained so 12 months later. Seventy percent of the aphasic patients fulfilled the DSM-III-R criteria of depression 3 months and 62% 12 months after stroke. The prevalence of major depression increased from 11 to 33% during the 12-month follow-up period. The non-verbal neuropsychological test performance in the aphasic patients was significantly inferior to that of the patients with dominant hemisphere lesion without aphasia. One third of the patients with ischaemic stroke suffer from communicative disorders which seem to increase the risk of depression and non-verbal cognitive deficits. Although the prevalence of depression in aphasic patients decreases in the long term, the proportion of patients suffering from major depression seems to increase. We emphasize the importance of the multidimensional evaluation of aphasic stroke patients.

Auditory P300 event related potential in minor ischemic stroke.

OBJECTIVE: Various degenerative cerebral diseases and even depression may cause abnormalities of the cognitive event related potentials (ERPs). We conducted the present study to elucidate the effects of ischemic stroke on the P300 ERP component. MATERIAL AND METHODS: We recorded the P300 wave using an auditory oddball paradigm in 38 consecutive brain infarct patients with mild neurological deficits at 3 and 12 months post-stroke, and in 29 healthy control subjects. RESULTS: Brain infarction slightly prolonged the P300 latency, and the observed delay was related to the presence and degree of post-stroke depression evaluated with the Zung Depression Scale and the DSM-III criteria. Infarction did not affect the P300 amplitude or its distribution on the scalp. The results of the patients with hemispheric brain infarction and those of the patients with brainstem infarction were similar, and also the values of the patients with the left- and right-sided lesions. The normal physiological correlation between subject age and the P300 latency was absent at 3 months post-stroke, but was present at 12 months post-stroke. CONCLUSION: Brain infarction delays the P300 ERP and temporarily distorts its age-related physiology. The increase of the P300 latency seems to be associated with the post-stroke depression.

Poststroke depression correlates with cognitive impairment and neurological deficits.

BACKGROUND AND PURPOSE: The prevalence of poststroke depression is known to be high, but the knowledge of its neuropsychological correlates is limited. This 12-month prospective study was designed to evaluate the natural history of poststroke depression and to study its neuropsychological, clinical, and functional associates. METHODS: We studied a series of 106 consecutive patients (46 women and 60 men, mean age 65.8 years) with acute first-ever ischemic stroke. The patients underwent a neurological, psychiatric, and neuropsychological examination at 3 and 12 months after the stroke. The psychiatric diagnosis of depression was based on DSM-III-R-criteria. RESULTS: Depression was diagnosed in 53% of the patients at 3 months and in 42% of the patients at 12 months after the stroke. The prevalence of major depression was 9% at 3 months and 16% at 12 months. There was an association between poststroke depression and cognitive impairment; the domains most likely to be defective in stroke-related depression were memory (P=0.022), nonverbal problem solving (P=0.039), and attention and psychomotor speed (P=0.020). The presence of dysphasia increased the risk of major depression. The depressive patients were more dependent in ADL and had more severe impairment and handicap than the nondepressive patients. CONCLUSIONS: More than half of the patients suffer from depression after stroke, and the frequency of major depression seems to increase during the first year. In addition to dysphasia, poststroke depression is correlated with other cognitive deficits. We emphasize the importance of psychiatric evaluation of stroke patients.

Moclobemide-induced hypersexuality in patients with stroke and Parkinson's disease.

Decline in sexual activities caused by diseases or by medication affecting the functions of the central nervous system has often been described, but there are few reports on diseases or medications causing hypersexuality. Bilateral lesions of the temporal lobes may result in the Klüver-Bucy syndrome, symptoms of which include hypersexuality, excessive eating, and mood changes. In this article, the authors describe moclobemide-induced reversible hypersexuality, without other features of the Klüver-Bucy syndrome, in two patients with stroke and one patient with Parkinson's disease.

Factors predictive of referral to psychiatric hospital among general hospital psychiatric consultations.

The aim of this paper was to explore the factors necessitating psychiatric hospital care in a Finnish multi-centre study of general hospital in-patients referred for psychiatric consultation. The study group consisted of 1251 patients referred to psychiatric hospital (n = 181) and a comparison group (n = 1070) consisting of subjects who were not referred. Differences between groups were studied by univariate analysis. Logistic regression analysis was used both to assess the factors contributing to referral to psychiatric hospital and to create predictive models. The validity of the models was analysed by means of receiver operating characteristic (ROC) curves in an independent sample. Psychiatric hospital care during the previous 5 years was associated with a 3.7-fold (odds ratio) increased risk of hospitalization. A diagnosis of psychosis was associated with a 2.9-fold increased risk, and attempted suicide as a reason for consultation was associated with a 2.1-fold increased risk. Not being married doubled the risk, and the odds ratio was also high in cases of poor psychosocial functioning (as assessed by Global Assessment of Functioning (GAF) score). The predictive model differentiated reasonably well between those patients who were hospitalized and the other patients. In conclusion, this multi-centre study of factors predictive of referral to psychiatric hospital among general hospital patients revealed that the most important determinants were previous psychiatric care, diagnosis of psychosis or severe depression, attempted suicide, being unmarried, and poor psychosocial functioning as assessed by GAF score.

A short DSM-III-R-based diagnostic instrument for screening mental disorders in geriatric institutions.

A screening instrument based on the DSM-III-R was developed in order to differentiate aged persons with or without a DSM-III-R mental disorder. The usefulness of this instrument was investigated in six geriatric institutions with 171 residents aged 65 to 93 years in Finland. The nursing staff independently rated the mental status of residents; researchers (a psychiatrist and general practitioner) made a diagnosis based on DSM-III-R criteria. The majority of the residents (mean 69%, varying from 33% to 84% in different institutions) had a DSM-III-R mental disorder. This screening instrument functioned well in differentiating residents without a mental disorder from those with DSM-III-R mental disorder: The nursing staff's agreement was 90%, kappa.71, sensitivity .90, and specificity .88. However, only half the cases of depression were diagnosed correctly: Sensitivity was .50 and specificity .95. With a more specific 9-class diagnostic instrument based mainly on DSM-III-R categories, agreement was only moderate (68%) and kappa .59. The instrument developed in this study seemed to be a useful screening method when applied by the staff, but accurate diagnostics require psychiatric knowledge, especially of depression.