Independent component analysis of noninvasively recorded cortical magnetic DC-fields in humans.

We apply a recently developed multivariate statistical data analysis technique--so called blind source separation (BSS) by independent component analysis--to process magnetoencephalogram recordings of near-dc fields. The extraction of near-dc fields from MEG recordings has great relevance for medical applications since slowly varying dc-phenomena have been found, e.g., in cerebral anoxia and spreading depression in animals. Comparing several BSS approaches, it turns out that an algorithm based on temporal decorrelation successfully extracted a dc-component which was induced in the auditory cortex by presentation of music. The task is challenging because of the limited amount of available data and the corruption by outliers, which makes it an interesting real-world testbed for studying the robustness of ICA methods.

Artifact reduction in magnetoneurography based on time-delayed second-order correlations.

Artifacts in magnetoneurography data due to endogenous biological noise sources, like the cardiac signal, can be four orders of magnitude higher than the signal of interest. Therefore, it is important to establish effective artifact reduction methods. We propose a blind source separation algorithm using only second-order temporal correlations for cleaning biomagnetic measurements of evoked responses in the peripheral nervous system. The algorithm showed its efficiency by eliminating disturbances originating from biological and technical noise sources and successfully extracting the signal of interest. This yields a significant improvement of the neuro-magnetic source analysis.

Noise robust estimates of correlation dimension and K2 entropy.

Using Gaussian kernels to define the correlation sum we derive simple formulas that correct the noise bias in estimates of the correlation dimension and K2 entropy of chaotic time series. The corrections are only based on the difference of correlation dimensions for adjacent embedding dimensions and hence preserve the full functional dependencies on both the scale parameter and embedding dimension. It is shown theoretically that the estimates, which are derived for additive white Gaussian noise, are also robust for moderately colored noise. Simulations underline the usefulness of the proposed correction schemes. It is demonstrated that the method gives satisfactory results also for non-Gaussian and dynamical noise.

Carcinoma of the uterine cervix associated with schistosomiasis and induced by human papillomaviruses.

OBJECTIVES: To determine the presence of human papillomaviruses (HPVs) in cervical cancer among patients in Tanzania and to ascertain their prevalence in cases associated with schistosomiasis. METHODS: In situ hybridization was applied to 31 carcinomas of the uterine cervix including 10 in which schistosomiasis co-occurred. Twenty-six cases in this series also exhibited koilocytic dysplasia. RESULTS: Twenty-six out of 31 cases revealed a specific hybridization for HPVs with varying density and distribution. A slightly higher labeling of HPV-16 than -18 was demonstrated. All schistosomiasis-associated cancers encoded the papillomaviruses. The 31 patients were predominantly young adults, a fact that reflects sexual activity at a very young age in the ethnic communities of Africa. CONCLUSION: These findings shed new light on the presumed etiologic implication of schistosomiasis in the genesis of cervical cancer. In the absence of HPV, schistosomiasis is not the oncogenic causative agent for carcinoma of the uterine cervix.

Comparison of different DIAGNOdent cut-off limits for in vivo detection of occlusal caries.

This study tested recently recommended cut-off limits for the laser fluorescence based device DIAGNOdent (KaVo) for detection of occlusal caries. Two hundred and forty-eight permanent molars from 94 patients (mean age 19.2 years) of a general dental practice were included. After professional tooth cleaning, the teeth were examined visually and by the laser fluorescence method. The extent of occlusal lesions (gold standard) was determined after minimal operative intervention. Upon fissure opening, 24 teeth had enamel caries and 224 teeth revealed dentin caries, of which 58 and 166, respectively, were up to or beyond half the dentin. The optimal cut-off limits based on the highest kappa-values (0.51 and 0.54) were > 18 for superficial dentinal caries (D3) and > 37 for deep dentinal caries (D4). The comparison with DIAGNOdent cut-offs given by the manufacturer (n = 4) and those based on clinical trials with in vivo validation (n = 4) and in vitro studies with histological validation (n = 3) revealed a considerable variation in performance. Recommended cut-offs between 17 and 21 for superficial dentin lesions were in the same order of magnitude (0.48-0.51). On the D4 level, only the manufacturer's cut-off of > 34 achieved the best performance (0.51). According to the highest kappa-values and the area under the ROC curves (D3: A(z) = 0.903; D4: A(z) = 0.830), the agreement between the extent of validated caries and laser fluorescence value is still unsatisfactory.

An in vitro study of the reliability of DIAGNOdent measurements.

Aim of this in vitro study was to assess the reliability of measurements by a laser fluorescence technique for occlusal caries detection. Four dentists using four DIAGNOdent devices (Dds) according to manufacturer's instructions examined 80 carefully cleaned extracted molars with non-cavitated occlusal lesions. Inter- and intra-examiner reproducibility were calculated using Lin's intra-class correlation coefficient (ICCLin) and the limits of agreement by Bland and Altman (Comp Biol Med 1990;20:337). An excellent intra-examiner reproducibility was found for all dentists (ICCLin 0.93-0.98). The inter-examiner reliability was proved to be good and excellent (ICCLin 0.74-0.98). By reason of the registered lower mean fluorescence values of dentist 3 compared with his/her colleagues all these measurements were excluded from further calculations. Differences between Dd instruments were not evident. When the values of the Dd were categorized according to the treatment related cut-off limits a substantial reproducibility was found in the range of 0-14 (ICCLin 0.66; DIFF 4.0/-3.5) and >30 (ICC(Lin) 0.6% of all Dd measurements were reproduced in the range 15-30 (ICC(Lin) 0.16; DIFF 8.1/-7.3). The results suggest that dentists should be trained before using Dd. The low reliability in the interval of 15-30 could indicate a limited use for a longitudinal caries monitoring on pits and fissures; further research should be focused on this clinically important interval.