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U Bick

Publications and source records attributed to U Bick.

At least 37 records · Page 2Linked to original sources
PubMed1998

Is image selection a useful strategy to decrease the transmission time in teleradiology? A study using 100 emergency cranial CTs.

This study examines the suitability of working with a selection of images in a teleradiology consulting system in neurological or neurosurgical emergency situations. The teleradiology system was based on IBM-compatible personal computers, video digitization for data acquisition, and data transmission by Integrated System Digital Network. Forty normal and 60 abnormal emergency cranial computed tomograms were shown to a radiologist on call who presented all cases he regarded as pathologic to a neuroradiologic expert by teleradiology. To reduce transmission time, only a selection of images from the CT study was presented (up to four images per case). For each case the on-call radiologist's diagnosis (D(on-call)), the expert's diagnosis on the teleradiology screen (D(monitor)), and the expert's diagnosis on the original film (D(original)) was documented, together with an estimation of the agreement between those diagnoses. There was clinically relevant disagreement between the on-call radiologist's diagnosis and the neuroradiologist's diagnosis based on the image selection on the teleradiology monitor in 23% of cases. A clinically important discrepancy between the neuroradiologist's diagnosis based on the image selection and his diagnosis using the original films was found in 30% of cases. This was due to the presence of clinically relevant information on images not transferred by the on-call radiologist. Image quality of the transferred images was sufficient in all cases. Drastic selection of images from a complete CT study leads to a high rate of incorrect diagnoses and is not appropriate to reduce transmission time in teleradiology.

Humans↗
PubMed1998

Computerized analysis of breast lesions in three dimensions using dynamic magnetic-resonance imaging.

Contrast-enhanced magnetic resonance imaging (MRI) of the breast is known to reveal breast cancer with higher sensitivity than mammography alone. The specificity is, however, compromised by the observation that several benign masses take up contrast agent in addition to malignant lesions. The aim of this study is to increase the objectivity of breast cancer diagnosis in contrast-enhanced MRI by developing automated methods for computer-aided diagnosis. Our database consists of 27 MR studies from 27 patients. In each study, at least four MR series of both breasts are obtained using FLASH three-dimensional (3D) acquisition at 90 s time intervals after injection of Gadopentetate dimeglumine (Gd-DTPA) contrast agent. Each series consists of 64 coronal slices with a typical thickness of 2 mm, and a pixel size of 1.25 mm. The study contains 13 benign and 15 malignant lesions from which features are automatically extracted in 3D. These features include margin descriptors and radial gradient analysis as a function of time and space. Stepwise multiple regression is employed to obtain an effective subset of combined features. A final estimate of likelihood of malignancy is determined by linear discriminant analysis, and the performance of classification by round-robin testing and receiver operating characteristics (ROC) analysis. To assess the efficacy of 3D analysis, the study is repeated in two-dimensions (2D) using a representative slice through the middle of the lesion. In 2D and in 3D, radial gradient analysis and analysis of margin sharpness were found to be an effective combination to distinguish between benign and malignant masses (resulting area under the ROC curve: 0.96). Feature analysis in 3D was found to result in higher performance of lesion characterization than 2D feature analysis for the majority of single and combined features. In conclusion, automated feature extraction and classification has the potential to complement the interpretation of radiologists in an objective, consistent, and accurate way.

Biophysical Phenomena↗
PubMed1998

[Possibilities and limits of diagnostic frozen section in breast carcinoma].

A short overview is given demonstrating the possibilities and limits of the frozen section technique in mammary carcinoma. The accuracy of this method in diagnostic pathology of the mammary gland is up to 97% when applied by experienced pathologists. In case of breast cancer it may be difficult to determine the maximum of tumor size and the minimum tumor-free distance to the resection margin which are significant for a breast-conserving operation. There are further limits when an atypical ductal hyperplasia (ADH) should be differentiated from a ductal carcinoma in situ (DCIS) and when in case of DCIS microinvasion is to be proven. Nevertheless, intraoperative frozen section technique is unrenunciable for breast cancer surgery. Mistakes can be avoided in most of the cases, if surgeon and pathologist will closely cooperate and if both are fully aware of the limitations of the method.

Breast↗
PubMed1998

[The ABBI system as a possibility for evaluating non-palpable lesions].

For non-palpable lesions detected radiographically alone, lumpectomy after needle-localization is currently performed. Specimen radiography provides an indirect proof of complete excision of the mammographic abnormality. Up to now, intraoperative mammography of the operated breast has not been possible. Digital intraoperative mammography is now possible with the ABBI-system, which will be introduced in this article. In a pilot study, we have investigated, whether it is possible to excise small carcinomas with the ABBI stereotactic biopsy device (maximum diameter 20 mm) without compromising breast conserving therapy. In a prospective study, 69 patients were diagnosed or treated using the ABBI-system. In all 60 patients with a primary lesion, a cylindrical excision was performed. Of these, 11 invasive and 5 intraductal carcinomas were diagnosed. 7 of the invasive and 2 of the intraductal cancers were treated with breast conserving surgery. In 9 cases, an in-breast recurrence was suspected. In 7 of these a cylindrical excision was performed. One invasive and 3 intraductal carcinomas were found and mastectomy was performed in these four patients. In two patients with the suspicion of an in-breast recurrence, the ABBI-system was used to perform a core-needle biopsy. In one patient, the biopsy finding was positive and mastectomy was performed. Patients with lesions close to the chest wall are not suited for the ABBI-system. The postoperative course was uneventful in all cases, the cosmetic result after breast-conserving therapy was very good. The advantages of this new method consist in the reliable stereotactic localization of suspicious lesions and in the fast intraoperative imaging.

Biopsy, Needle↗
PubMed1997

Kinetics of phenylalanine transport at the human blood-brain barrier investigated in vivo.

In vivo proton magnetic resonance spectroscopy was used to investigate intracerebral phenylalanine (Phe) concentrations in nine patients with classical phenylketonuria (PKU). The study included serial examinations (n = 31; plasma Phe levels: 0.47-2.24 mmol/l) of patients either receiving a Phe-restricted diet (200 mg Phe per day; four patients) or a diet rich in Phe (1000 mg Phe per day; three patients). No spectrum showed metabolic abnormalities besides elevated Phe. Difference spectroscopy yielded intracerebral Phe concentrations between 0.20 and 0.76 mmol/l. Regional variations between parieto-occipital periventricular brain, frontal brain, and cerebellum were not statistically significant. Data could be fitted assuming saturable Phe transport into the brain, based on a symmetric Michaelis-Menten model (characterized by an apparent Michaelis transport constant, K(t,app), and a maximum transport velocity, Tmax) and constant Phe consumption in the brain cells (described by a velocity Vmax). Non-linear least-squares fitting of the combined data from all patients yielded K(t,app) = 0.16 +/- 0.11 mmol/l and (Tmax / Vmax) = 9.0 +/- 4.1. Carrier saturation and competitive inhibition of the influx of other large neutral amino acids can be expected at plasma Phe levels usually found in PKU patients.

Adolescent↗
PubMed1997

[Telemedicine. Possibilities and perspectives].

The discussion about the implementation of telemedicine and teleresourcing and its consequences has been under way for some time now. The rate at which telemedical applications are being developed, leaves little time for consideration of the economic, scientific and social aspects. There is a need for integration of all the existing fragments into one coherent telemedical concept. Different aspects of telemedical concepts are discussed.

Computer Communication Networks↗
PubMed1997

[Commercial teleradiology systems in Germany].

Teleradiologysystems can differ considerably in their features. The most important differences lie in the mode of image data acquisition, data transfer, data safety aspects and the possibilities of interaction between separate teleradiology units. A selection of commercially available teleradiologysystems is presented and compared.

Computer Systems↗
PubMed1997

[An integrated early detection concept in women with a genetic predisposition for breast cancer].

Breast cancer is in 5% of cases due to a genetic disposition. BRCA1 and BRCA2 are by far the most common breast cancer susceptibility genes. For a woman with a genetic predisposition, the individual risk of developing breast cancer sometime in her life is between 70 and 90%. Compared to the spontaneous forms of breast cancer, woman with a genetic predisposition often develop breast cancer at a much younger age. This is why conventional screening programs on the basis of mammography alone cannot be applied without modification to this high-risk group. In this article, an integrated screening concept for women with genetic predisposition for breast cancer using breast self-examination, clinical examination, ultrasound, mammography and magnetic resonance imaging is introduced.

BRCA1 Protein↗
PubMed1997

Evaluation of myelination and myelination disorders with turbo inversion recovery magnetic resonance imaging.

The aim of our work was to determine the efficacy of turbo inversion recovery spin echo (TIRSE) pulse sequences in differentiating patients with normal and abnormal myelination. Twenty neurological normal children (aged 5 months to 12 years) as well as 65 children presenting clinically with neurologic developmental deficits (aged 2 months to 10 years) were examined using TIRSE, T1-weighted SE, and T2-weighted turbo SE pulse sequences. Contrast-to-noise-ratio (CNR) between myelinated white and gray matter was compared for the different pulse sequences. In addition, two readers analyzed all images qualitatively by consensus. The CNR values were significantly higher on TIRSE images as compared with conventional images (p < 0. 05). Forty-two neurologically abnormal patients displayed a normal myelination on all sequences, whereas 23 showed an abnormal myelination. The TIRSE sequence provided a sensitive and specific depiction of an abnormal myelination in all of these patients. The TIRSE sequence provided additional information to conventional pulse sequences in determining myelination disorders in children, especially in children older than 2 years.

Adolescent↗
PubMed1997

Progression of cerebral white matter abnormalities in early treated patients with phenylketonuria during adolescence.

In this study of cranial MRI a group of 15 adolescents with classical phenylketonuria and permanent blood phenylalanine (phe) checks from infancy was investigated twice with an interval of three years in between. Cranial MRI revealed a progression of white matter abnormalities in patients with moderate and poor control of blood phe levels, however not in well controlled patients. Nevertheless results indicate an individual vulnerability of the brain against elevated phenylalanine levels in phenylketonurics.

Adolescent↗
PubMed1996

[Computer-assisted diagnosis in screening mammography].

Computer-aided diagnosis schemes in mammography aim at improving the mammographic detection of breast cancer. Through special computer algorithms, it is possible to automatically detect suspicious areas in mammographic images. Typical examples are schemes for automatic detection of microcalcifications and masses in mammography. The computer results may be presented to the reporting radiologist, with the computer acting as a diagnostic aid. Various computer-aided diagnosis schemes in mammography are introduced and possible clinical applications are discussed.

Algorithms↗
PubMed1996

[Product of the month: the Schering Atlas. Sectional anatomy of CT and MRI images].

The Schering Atlas is a teaching file in CT and MRI anatomy designed for physicians and students. It is available on CD-ROM, shows good image quality, and is easy to use in medium-price-range personal computer systems. Because of the amount and quality of image material, the Schering Atlas's price is appropriate for institutions, but not for private users.

Anatomy, Artistic↗
PubMed1996

Density correction of peripheral breast tissue on digital mammograms.

When digital mammograms are viewed on video displays, evaluation of the skin and subcutaneous tissue is often difficult and may require special window settings. An algorithm has been developed for selective enhancement (ie, density correction) of the dark peripheral portions of the breast on mammograms. After an automated segmentation of the digital mammogram and identification of the skin line, a fitted enhancement curve is generated to selectively enhance all pixels within a certain distance from the skin to match the density of the center part of the breast. After enhancement, skin and breast parenchyma can be evaluated simultaneously without the need for different window settings. When tested on a set of 400 digitized mammograms, the density correction algorithm significantly (P < .0001) increased the maximum area of breast tissue visualized simultaneously at window width settings of 0.5-2.0 delta OD (optical density). Artifacts interfering with interpretation were observed in less than 1%. The algorithm for correcting the density of peripheral breast tissue substantially facilitates and improves the display of digital mammograms and thus will be a valuable component of an integrated workstation for computer-aided diagnosis in mammography.

Algorithms↗
PubMed1995

Automated segmentation of digitized mammograms.

RATIONALE AND OBJECTIVES: Fast and reliable segmentation of digital mammograms into breast and nonbreast regions is an important prerequisite for further image analysis. We are developing a segmentation algorithm that is fully automated and can operate independent of type of digitizing system, image orientation, and image projection. METHODS: The algorithm identifies unexposed and direct-exposure image regions and generates a border surrounding the valid breast region, which can then be used as input for further image analysis. The program was tested on 740 digitized mammograms; the segmentation results were evaluated by two expert mammographers and two medical physicists. RESULTS: In 97% of the mammograms, the segmentation results were rated as acceptable for use in computer-aided diagnostic schemes. Segmentation problems encountered in the remaining 22 images (2.9%) were most often caused by digitization artifacts or poor mammographic technique. CONCLUSION: The developed algorithm can serve as a component of an "intelligent" workstation for computer-aided diagnosis in mammography.

Algorithms↗
PubMed1995

Molybdenum-cofactor deficiency: CT and MR findings.

We describe the CT and MR findings in molybdenum-cofactor deficiency, a rare metabolic disorder which is caused by the defect of a molybdenum-containing enzyme cofactor. The CT (3 patients) and/or MR studies (3 patients) of 4 children, which became symptomatic with intractable seizures within the first days after birth and finally turned out to have molybdenum cofactor deficiency, were reviewed. All patients showed multicystic leukencephalopathy and a normal newborn pattern of myelination of the brainstem. A striking finding in some studies was an abnormal shape of the frontal horns of the dilated ventricles caused by severe volume loss of the basal ganglia, especially of the caudate nucleus, and of the corpus callosum. MRI was superior to CT in the demonstration of these lesions. In molybdenum-cofactor deficiency, which can be diagnosed by a typical laboratory pattern, CT and MR show the findings of severe perinatal brain damage. The abnormal shape of the frontal horns, although possibly not specific, may even suggest molybdenum-cofactor deficiency in newborns with intractable seizures.

Brain↗
PubMed1995

Analysis of spiculation in the computerized classification of mammographic masses.

Spiculation is a primary sign of malignancy for masses detected by mammography. In this study, we developed a technique that analyzes patterns and quantifies the degree of spiculation present. Our current approach involves (1) automatic lesion extraction using region growing and (2) feature extraction using radial edge-gradient analysis. Two spiculation measures are obtained from an analysis of radial edge gradients. These measures are evaluated in four different neighborhoods about the extracted mammographic mass. The performance of each of the two measures of spiculation was tested on a database of 95 mammographic masses using ROC analysis that evaluates their individual ability to determine the likelihood of malignancy of a mass. The dependence of the performance of these measures on the choice of neighborhood was analyzed. We have found that it is only necessary to accurately extract an approximate outline of a mass lesion for the purposes of this analysis since the choice of a neighborhood that accommodates the thin spicules at the margin allows for the assessment of margin spiculation with the radial edge-gradient analysis technique. The two measures performed at their highest level when the surrounding periphery of the extracted region is used for feature extraction, yielding Az values of 0.83 and 0.85, respectively, for the determination of malignancy. These are similar to that achieved when a radiologist's ratings of spiculation (Az = 0.85) are used alone. The maximum value of one of the two spiculation measures (FWHM) from the four neighborhoods yielded an Az of 0.88 in the classification of mammographic mass lesions.

Automation↗
PubMed1994

White matter abnormalities in phenylketonuria: results of magnetic resonance measurements.

In adolescents and adults with PKU, blood phenylalanine levels above 10 mg/dl are generally associated with white matter changes in MRI. The grade of these changes is correlated to most recent blood phenylalanine levels. Based on studies using T2 relaxometry the MRI changes seem to be the consequence of a reversible dysmyelination. The clinical relevance of these white matter changes remains unclear as the extent of MRI alterations did not correlate with IQ, neurological and electrophysiological deficits of the patients. The intracerebral phenylalanine concentration as measured by protonspectroscopy amounts to about 50% of blood phenylalanine concentrations. Preliminary data indicate that brain phenylalanine levels remain constant if blood concentrations exceed 20 mg/dl. This might be of clinical relevance for the treatment of adolescent and adult PKU patients.

Brain Chemistry↗