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PubMed1986

Automatic analysis of static charge sensitive bed (SCSB) recordings in the evaluation of sleep-related apneas.

An automatic analysis of Static Charge Sensitive Bed (SCSB) recordings was evaluated in the detecting periodic apneas during sleep. The results of over-night SCSB recordings, on body movements and respiratory movements, were compared with the visually evaluated polygraphic recordings during daytime sleep. Twenty-one patients with obstructive sleep apnea syndrome and 18 controls were studied. The periodic breathing pattern seen in all daytime recordings, was also seen in all output graphs of the over-night SCSB analyses. The automatic analyses revealed periodic breathing in 2 control subjects. The amount was, however, small (less than 4% of the recording time) compared with the high amount observed in the patients with obstructive sleep apneas (mean 42.9% of the recording time). The high sensitivity, easy use, and low cost of the automatic SCSB method make it suitable for the quantification of the periodic breathing during night and for the screening of sleep apneas.

Adult↗
PubMed1985

Repeated automatic visual field screening in a cohort study.

During 1977 and 1978 automatic visual field screening was performed in 1511 persons born 1907-1921 and taking part in a population study. Three years later automatic visual field screening was repeated in 2565 eyes of 1293 persons. "Irrelevant" defects were common and had a limited repeatability. "Relevant" defects were easily detected at the first and reproduced at the second survey. From a clinical point of view, the yield of the visual field screening at the second survey was restricted. We concluded that repeated visual field screening by automatic perimetry is quite feasible but has little reward.

Diagnostic Errors↗
PubMed1990

Halothane, isoflurane and enflurane potentiate the effect of noradrenaline on ventricular automaticity in the rat heart: evidence of the involvement of both alpha- and beta-adrenoceptors.

Direct evidence has been sought as to what extent the sensitization of heart to the arrhythmogenic action of sympathomimetic drugs in the presence of the inhalatory anaesthetics, halothane, isoflurane and enflurane, is mediated by either alpha- or beta-adrenoceptors. For this purpose, the effects of isoprenaline, noradrenaline and phenylephrine on ventricular automaticity induced by local injury have been studied in the isolated right ventricle of the rat. Isoprenaline was more potent in increasing ventricular automaticity than either phenylephrine or noradrenaline. The anaesthetic potentiated the effects of noradrenaline, as well as that of higher concentrations of phenylephrine, but not those of isoprenaline. These results support the contention that increases in ventricular automaticity induced by sympathomimetic drugs are mainly mediated by adrenoceptors of the beta-type. However, the simultaneous activation of both alpha- and beta-adrenoceptors seems to be necessary for the effect of the anaesthetics in sensitizing the heart to sympathomimetic drugs.

Anesthetics↗
PubMed1992

How specific are negative automatic thoughts to a depressed population? An exploratory study.

This paper is concerned with the relationship between negative or dysfunctional automatic thoughts and dysphoric mood in a non-clinical population. It addresses the question of how specific are these automatic thoughts to a depressed population. Negative automatic thoughts were obtained from 27 normal subjects via a thought-sampling method using the Daily Record of Dysfunctional Thoughts Form (Beck, Rush, Shaw & Emery, 1979) over a two-week period. A thought-content analysis was conducted. The resultant data were compared using X2 with Blackburn & Eunson's (1989) data from depressed patients. The results presented in this paper indicate that basic cognitive distortions occur in a normal population, but differ qualitatively and quantitatively from those found in depressed patients.

Adult↗
PubMed1995

Automatic magnetic resonance tissue characterization for three-dimensional magnetic resonance imaging of the brain.

Computer-assisted diagnostic systems enhance the information available from magnetic resonance imaging. Segmentations are the basis on which three-dimensional volume renderings are made. The application of a raw data-based, operator-independent (automatic), magnetic resonance segmentation technique for tissue differentiation is demonstrated. Segmentation images of vasogenic edema with gross and histopathological correlation are presented for demonstration of the technique. A pixel was classified into a tissue class based on a feature vector using unsupervised fuzzy clustering techniques as the pattern recognition method. Correlation of fuzzy segmentations and gross and histopathology were successfully performed. Based on the results of neuropathological correlation, the application of fuzzy magnetic resonance image segmentation to a patient with a brain tumor and extensive edema represents a viable technique for automatically displaying clinically important tissue differentiation. With this pattern recognition technique, it is possible to generate automatic segmentation images that display diagnostically relevant neuroanatomical and neuropathological tissue contrast information from raw magnetic resonance data for use in three-dimensional volume reconstructions.

Adult↗
PubMed2004

A deformable-model approach to semi-automatic segmentation of CT images demonstrated by application to the spinal canal.

Because of the importance of accurately defining the target in radiation treatment planning, we have developed a deformable-template algorithm for the semi-automatic delineation of normal tissue structures on computed tomography (CT) images. We illustrate the method by applying it to the spinal canal. Segmentation is performed in three steps: (a) partial delineation of the anatomic structure is obtained by wavelet-based edge detection; (b) a deformable-model template is fitted to the edge set by chamfer matching; and (c) the template is relaxed away from its original shape into its final position. Appropriately chosen ranges for the model parameters limit the deformations of the template, accounting for interpatient variability. Our approach differs from those used in other deformable models in that it does not inherently require the modeling of forces. Instead, the spinal canal was modeled using Fourier descriptors derived from four sets of manually drawn contours. Segmentation was carried out, without manual intervention, on five CT data sets and the algorithm's performance was judged subjectively by two radiation oncologists. Two assessments were considered: in the first, segmentation on a random selection of 100 axial CT images was compared with the corresponding contours drawn manually by one of six dosimetrists, also chosen randomly; in the second assessment, the segmentation of each image in the five evaluable CT sets (a total of 557 axial images) was rated as either successful, unsuccessful, or requiring further editing. Contours generated by the algorithm were more likely than manually drawn contours to be considered acceptable by the oncologists. The mean proportions of acceptable contours were 93% (automatic) and 69% (manual). Automatic delineation of the spinal canal was deemed to be successful on 91% of the images, unsuccessful on 2% of the images, and requiring further editing on 7% of the images. Our deformable template algorithm thus gives a robust segmentation of the spinal canal on CT images. The method can be extended to other structures, although it remains to be shown that chamfer matching is sufficiently robust for the delineation of soft-tissue structures surrounded by soft tissue.

Algorithms↗
PubMed2004

An automatic seed finder for brachytherapy CT postplans based on the Hough transform.

PURPOSE: The purpose of the work is to describe a new algorithm for the automatic detection of implanted radioactive seeds within the prostate. The algorithm is based on the traditional Hough transform. A method of quality assurance is described as well as a quantitative phantom study to determine the accuracy of the algorithm. METHODS AND MATERIALS: An algorithm is described which is based on the Hough transform. The Hough transform is a well known transform traditionally used to automatically segment lines and other well defined geometric objects from images. The traditional Hough transform is extended to three-dimensions and applied to CT images of seed implanted prostate glands. A method based on digitally reconstructed radiographs is described to quality assure the determined three-dimensional positions of the detected seeds. Two phantom studies utilizing eight seeds and nine seeds are described. All eight seeds form a contiguous a square while the nine seed phantom describes seeds which are placed side-by-side in groups of two and three. The algorithm is applied to the CT scans of both phantoms and the seed positions determined. RESULTS: The algorithm has been commercially developed and used to perform postsurgical dosimetric assessment on approximately 1000 patients. Using the described quality assurance tool it was determined that the algorithm accurately determined the seed positions in all 1000 patients. The algorithm was also applied to the eight seed phantom. The algorithm successfully found all eight seeds as well as their seed coordinates. The average radial error was determined to be 0.9 mm. For the nine seed phantom, the algorithm correctly identified all nine seeds, with an average radial error of 3 mm. CONCLUSIONS: The described algorithm is a robust, accurate, automatic, three-dimensional application for CT based seed determination.

Algorithms↗
PubMed2006

A semi-automatic method for peak and valley detection in free-breathing respiratory waveforms.

The existing commercial software often inadequately determines respiratory peaks for patients in respiration correlated computed tomography. A semi-automatic method was developed for peak and valley detection in free-breathing respiratory waveforms. First the waveform is separated into breath cycles by identifying intercepts of a moving average curve with the inspiration and expiration branches of the waveform. Peaks and valleys were then defined, respectively, as the maximum and minimum between pairs of alternating inspiration and expiration intercepts. Finally, automatic corrections and manual user interventions were employed. On average for each of the 20 patients, 99% of 307 peaks and valleys were automatically detected in 2.8 s. This method was robust for bellows waveforms with large variations.

Algorithms↗
PubMed1994

Automatic three-dimensional correlation of CT-CT, CT-MRI, and CT-SPECT using chamfer matching.

Image correlation is often required to utilize the complementary information in CT, MRI, and SPECT. A practical method for automatic image correlation in three-dimensions (3D) based on chamfer matching is described. The method starts with automatic extraction of contour points in one modality and automatic segmentation of the corresponding feature in the other modality. A distance transform is applied to the segmented volume and a cost function is defined that operates between the contour points and the distance transform. Matching is performed by iteratively optimizing the cost function for 3D translation, rotation, and scaling of the contour points. The complete matching process including segmentation requires no user interaction and takes about 100 s on an HP715/50 workstation. Perturbation tests on clinical data with cost functions based on mean, rms, and maximum distances in combination with two general purpose optimization procedures have been performed. The performance of the methods has been quantified in terms of accuracy, capture range, and reliability. The best results on clinical data are obtained with the cost function based on the mean distance and the simplex optimization method. The accuracy is 0.3 mm for CT-CT, 1.0 mm for CT-MRI, and 0.7 mm for CT-SPECT correlation of the head. The accuracy is usually at subpixel level but is limited by global geometric distortions, e.g., for CT-MRI correlation. Both for CT-CT and CT-MRI correlation the capture range is about 6 cm, which is higher than normal differences in patient setup found on the scanners (less than 4 cm). This means that the correlation procedure seldom fails (better than 98% reliability) and user interaction is unnecessary. For CT-SPECT matching the capture range is about 3 cm (80% reliability), and must be further improved. The method has already been introduced in clinical practice.

Biophysical Phenomena↗
PubMed1996

Automatic three-dimensional inspection of patient setup in radiation therapy using portal images, simulator images, and computed tomography data.

In external beam radiotherapy, conventional analysis of portal images in two dimensions (2D) is limited to verification of in-plane rotations and translations of the patient. We developed and clinically tested a new method for automatic quantification of the patient setup in three dimensions (3D) using one set of computed tomography (CT) data and two transmission images. These transmission images can be either a pair of simulator images or a pair of portal images. Our procedure adjusts the position and orientation of the CT data in order to maximize the distance through bone in the CT data along lines between the focus of the irradiation unit and bony structures in the transmission images. For this purpose, bony features are either automatically detected or manually delineated in the transmission images. The performance of the method was quantified by aligning randomly displaced CT data with transmission images simulated from digitally reconstructed radiographs. In addition, the clinical performance were assessed in a limited number of images of prostate cancer and parotid gland tumor treatments. The complete procedure takes less than 2 min on a 90-MHz Pentium PC. The alignment time is 50 s for portal images and 80 s for simulator images. The accuracy is about 1 mm and 1 degrees. Application to clinical cases demonstrated that the procedure provides essential information for the correction of setup errors in case of large rotations (typically larger than 2 degrees) in the setup. The 3D procedure was found to be robust for imperfections in the delineation of bony structures in the transmission images. Visual verification of the results remains, however, necessary. It can be concluded that our strategy for automatic analysis of patient setup in 3D is accurate and robust. The procedure is relatively fast and reduces the human workload compared with existing techniques for the quantification of patient setup in 3D. In addition, the procedure improves the accuracy of treatment verification in 2D in some cases where rotational deviations in the setup occur.

Biophysical Phenomena↗
PubMed1999

Automatic extraction of corresponding points for the registration of medical images.

In this paper we address the problem of finding corresponding points in a reference and its subsequent image with the aim of registering the images. A whole-image-content-based automatic algorithm for extracting point pairs from 2-D monomodal medical images has been developed. The properties of point distinctiveness, point pair similarity, and point pair consistency have been incorporated into the steps which lead to the automatic extraction and weighting of point pairs. The selection of the most distinctive points of the reference image, and the search for their corresponding points in the subsequent image, have two things in common. First, the local operator by which the distinctive points are selected mimics the template matching used to find the corresponding points. Second, the same similarity measure is used for both tasks. We have applied the algorithm to a variety of computer-generated and real medical images, and have both qualitatively and quantitatively evaluated its performance. The results show that the proposed automatic algorithm for point extraction is accurate and robust and that it may significantly improve on the accuracy, reproducibility, and speed of the manual extraction of corresponding points.

Algorithms↗
PubMed2002

An investigation of the reproducibility and usefulness of automatic couch motion in complex radiation therapy techniques.

Radiation therapy techniques that incorporate multiple couch motions are becoming more common, and they often involve an increasing level of complexity along with a need for automatic motion. The reproducibility of automatic couch motion is thus a growing concern. In this work we carried out various tests to assess the automatic motion of a commercial treatment couch, including tests to evaluate the digital readout reproducibility, as well as an independent verification of the reproducibility of the couch positions on repeated motions, using phantoms as well as a volunteer subject. It was shown that the couch motion is highly reproducible, with no discomfort to the patient, and can greatly improve treatment times as well as reduce errors in couch positioning.

Humans↗
PubMed2004

Evaluation of formant-like features on an automatic vowel classification task.

Numerous attempts have been made to find low-dimensional, formant-related representations of speech signals that are suitable for automatic speech recognition. However, it is often not known how these features behave in comparison with true formants. The purpose of this study was to compare two sets of automatically extracted formant-like features, i.e., robust formants and HMM2 features, to hand-labeled formants. The robust formant features were derived by means of the split Levinson algorithm while the HMM2 features correspond to the frequency segmentation of speech signals obtained by two-dimensional hidden Markov models. Mel-frequency cepstral coefficients (MFCCs) were also included in the investigation as an example of state-of-the-art automatic speech recognition features. The feature sets were compared in terms of their performance on a vowel classification task. The speech data and hand-labeled formants that were used in this study are a subset of the American English vowels database presented in Hillenbrand et al. [J. Acoust. Soc. Am. 97, 3099-3111 (1995)]. Classification performance was measured on the original, clean data and in noisy acoustic conditions. When using clean data, the classification performance of the formant-like features compared very well to the performance of the hand-labeled formants in a gender-dependent experiment, but was inferior to the hand-labeled formants in a gender-independent experiment. The results that were obtained in noisy acoustic conditions indicated that the formant-like features used in this study are not inherently noise robust. For clean and noisy data as well as for the gender-dependent and gender-independent experiments the MFCCs achieved the same or superior results as the formant features, but at the price of a much higher feature dimensionality.

Algorithms↗
PubMed2000

Quantitative assessment of second language learners' fluency by means of automatic speech recognition technology.

To determine whether expert fluency ratings of read speech can be predicted on the basis of automatically calculated temporal measures of speech quality, an experiment was conducted with read speech of 20 native and 60 non-native speakers of Dutch. The speech material was scored for fluency by nine experts and was then analyzed by means of an automatic speech recognizer in terms of quantitative measures such as speech rate, articulation rate, number and length of pauses, number of dysfluencies, mean length of runs, and phonation/time ratio. The results show that expert ratings of fluency in read speech are reliable (Cronbach's alpha varies between 0.90 and 0.96) and that these ratings can be predicted on the basis of quantitative measures: for six automatic measures the magnitude of the correlations with the fluency scores varies between 0.81 and 0.93. Rate of speech appears to be the best predictor: correlations vary between 0.90 and 0.93. Two other important determinants of reading fluency are the rate at which speakers articulate the sounds and the number of pauses they make. Apparently, rate of speech is such a good predictor of perceived fluency because it incorporates these two aspects.

Electronic Data Processing↗
PubMed1995

Fully automatic determination of soil bacterium numbers, cell volumes, and frequencies of dividing cells by confocal laser scanning microscopy and image analysis.

We describe a fully automatic image analysis system capable of measuring cell numbers, volumes, lengths, and widths of bacteria in soil smears. The system also determines the number of cells in agglomerates and thus provides the frequency of dividing cells (FDC). Images are acquired from a confocal laser scanning microscope. The grey images are smoothed by convolution and by morphological erosion and dilation to remove noise. The background is equalized by flooding holes in the image and is then subtracted by two top hat transforms. Finally, the grey image is sharpened by delineation, and all particles above a fixed threshold are detected. The number of cells in each detected particle is determined by counting the number of local grey-level maxima in the particle. Thus, up to 1,500 cells in 10 fields of view in a soil smear are analyzed in 30 min without human intervention. Automatic counts of cell numbers and FDC were similar to visual counts in field samples. In microcosms, automatic measurements showed significant increases in cell numbers, FDC, mean cell volume, and length-to-width ratio after amendment of the soil. Volumes of fluorescent microspheres were measured with good approximation, but the absolute values obtained were strongly affected by the settings of the detector sensitivity. Independent measurements of bacterial cell numbers and volumes by image analysis and of cell carbon by a total organic carbon analyzer yielded an average specific carbon content of 200 fg of C (mu)m(sup-3), which indicates that our volume estimates are reasonable.

Journal Article↗
PubMed1983

Evaluation of screening for hypertension in general practice with an automatic machine.

An automatic device for measuring blood pressure was used to screen all patients aged 30 to 65 years registered at a health centre. Of those who were eligible, 55% attended. Patients with previously recognised hypertension were more common among the attenders than among the non-attenders. High readings obtained on the automatic device possibly deterred some patients from reattending for follow up measurements of blood pressure. Although the device is quick and easy to use, the logistic challenge of formal blood pressure screening is considerable. Hypertension was discovered in 52 patients (mean diastolic pressure greater than 100 mm Hg). Retrospective analysis of their medical records showed that a third had had an abnormal blood pressure reading noted during the past 10 years and no further action had been taken, and almost three quarters had attended their practitioner during the previous year without having a blood pressure measurement recorded. One year after the screening procedure two fifths of the newly discovered hypertensive patients had defaulted from follow up and treatment. Automatic devices are not a short cut to the discovery of occult hypertension. Case finding by routine measurement of blood pressure at surgery visits is more efficient.

Adult↗
PubMed1991

Moderate hypothermia in the management of resistant automatic tachycardias in children.

BACKGROUND: Automatic focus tachycardias are often resistant to electrical and pharmacological treatment. Moderate systemic hypothermia (32-34 degrees C) may reduce the tachycardia rate in children with His bundle tachycardia after cardiac surgery. METHODS: The case notes of seven children with automatic focus tachycardias treated with hypothermia were reviewed. Six had His bundle tachycardia after cardiac surgery and one had ectopic atrial tachycardia; all had signs of low cardiac output. RESULTS: Hypothermia led to a reduction in heart rate in all patients (from 211 (28) (mean (SD] to 146 (5) beats/minute, p less than 0.001), with rises in systolic blood pressure (from 74 (14) mm Hg to 97 (10) mm Hg, p less than 0.01) and hourly urine output (from 0.5 (0.4) ml/kg to 4.6 (2.8) ml/kg, p less than 0.02). No direct adverse effects were noted. The arrhythmia did not resolve in three children, who died (two with His bundle tachycardia after Fontan procedures and one with ectopic atrial tachycardia); the other four regained sinus rhythm which was maintained at follow up of 3-13 (mean 9) months. CONCLUSIONS: Moderate systemic hypothermia led to slowing of the arrhythmia rate and an improvement in cardiac output in patients with resistant automatic focus tachycardias. It can be used to improve the haemodynamic condition while other measures of arrhythmia control are being pursued or until spontaneous recovery of normal rhythm.

Anti-Arrhythmia Agents↗
PubMed2007

High hopes and automatic escalators: a critique of some new arguments in bioethics.

Two protechnology arguments, the "hopeful principle" and the "automatic escalator", often used in bioethics, are identified and critically analysed in this paper. It is shown that the hopeful principle is closely related to the problematic precautionary principle, and the automatic escalator argument has close affinities to the often criticised empirical slippery slope argument. The hopeful principle is shown to be really hopeless as an argument, and automatic escalator arguments often lead nowhere when critically analysed. These arguments should therefore only be used with great caution.

Bioethics↗