Biomedical subjects

U Bick

Publications and source records attributed to U Bick.

At least 19 recordsLinked to original sources

PubMed2001

International investigation of breast MRI: results of a multicentre study (11 sites) concerning diagnostic parameters for contrast-enhanced MRI based on 519 histopathologically correlated lesions.

A multicentre study was undertaken to provide fundamentals for improved standardization and optimized interpretation guidelines of dynamic contrast-enhanced MRI. Only patients scheduled for biopsy of a clinical or imaging abnormality were included. They underwent standardized dynamic MRI on Siemens 1.0 (163 valid lesions > or = 5 mm) or 1.5 T (395 valid lesions > or = 5 mm) using 3D fast low-angle shot (FLASH; 87 s) before and five times after standardized bolus of 0.2 mmol Gd-DTPA/kg. One-Tesla and 1.5 T data were analysed separately using a discriminant analysis. Only histologically correlated lesions entered the statistical evaluation. Histopathology and imaging were correlated in retrospect and in open. The best results were achieved by combining up to five wash-in or wash-out parameters. Different weighting of false-negative vs false-positive calls allowed formulation of a statistically based interpretation scheme yielding optimized rules for the highest possible sensitivity (specificity 30%), for moderate (50%) or high (64-71%) specificity. The sensitivities obtained at the above specificity levels were better at 1.0 T (98, 97, or 96%) than at 1.5 T (96, 93, 86%). Using a widely available standardized MR technique definition of statistically founded interpretation rules is possible. Choice of an optimum interpretation rule may vary with the clinical question. Prospective testing remains necessary. Differences of 1.0 and 1.5 T are not statistically significant but may be due to pulse sequences.

Adult↗

PubMed2001

Differentiation between benign and malignant findings on MR-mammography: usefulness of morphological criteria.

The purpose of this study was to evaluate the usefulness of morphological criteria in differentiating between benign and malignant lesions on MR-mammography. Fifty-three women (18-82 years) with 62 lesions scheduled for excisional biopsy underwent dynamic contrast-enhanced MR-mammography using fast 3D Gradient-Echo sequences in coronal orientation (axial orientation in seven patients). Histology revealed 44 malignant and 18 benign lesions. For each lesion, five radiologists evaluated four morphological features: lesion shape, irregularity of contour, homogeneity of contrast enhancement and presence of ring enhancement. For each feature a receiver operating characteristic (ROC) curve was generated with calculation of the area under the curve (AUC). Interobserver variability was evaluated by the kappa-coefficient. The most reliable morphological feature indicating malignancy was an irregular lesion contour with a sensitivity/specificity/AUC of 83%/76%/0.9 followed by inhomogeneous contrast enhancement (85%/42%/0.7) and the presence of ring enhancement (71%/53%/0.64). The average interobserver agreement for the different features ranged between 0.35 and 0.4. Morphological criteria are useful features in MR-mammography for differentiating between benign and malignant lesions. However, due to the relatively high interobserver variability, standardization of terminology is important.

Adolescent↗

PubMed2001

[Improved diagnosis through digital mammography with the assistance of computer algorithms].

OBJECTIVE: The aim of this survey was to determine improved diagnostics through digital mammography with assistance of computer algorithms and new investigation techniques. MATERIAL AND METHODS: In general, the presented procedures are practicable with all digital mammography procedures. In our clinic the largest clinical experience exists with the only FDA certified full field mammography device Senograph 2000D (GE Medical Systems). RESULTS: First results from initial studies are shown, which are to evaluate the new procedures. The so-called post processing with visualization of microcalcifications, computer-assisted diagnosis, tomosynthesis, energy subtraction, contrast media in mammography and teleradiology are considered in particular. CONCLUSION: Digital mammography represents a promising procedure, opening new possibilities for improved diagnostic in mammography.

Algorithms↗

PubMed2000

Tissue transition projection (TTP) of the intestines.

Tissue transition projection (TTP) represents a three-dimensional reconstruction technique for volumetric image data sets. To demonstrate the principle characteristics of TTP, a simple phantom consisting of two pipes with a simulated, wall-adherent polyp was scanned with spiral CT, and images were reconstructed by means of volume rendering for both opaque surface reconstructions and TTP. Tissue transition projection was used in 7 patients for reconstruction of the small intestine or the colon. Unlike three-dimensional reconstructions with opaque surfaces, TTP enhances surface transitions while suppressing homogeneous areas, allowing delineation of the bowel wall similar to conventional double-contrast studies.

Adenocarcinoma↗

PubMed2000

[Initial clinical experiences with digital full-field mammography].

OBJECTIVE: Digital full-field mammography has been used at the Department of Radiology of Charité Medical Center in Berlin since June 1999. This study compares the new digital technique with conventional mammography including a survey of its value in breast imaging and an outline of future prospects. MATERIAL AND METHODS: More than 1,000 of a total of over 5,000 mammographies performed between June 1999 and April 2000 have been obtained using the digital full-field mammography system Senographe 2000D (GE Medical Systems). The digital mammograms were compared with previous conventional films and conventional mammographies performed during the same period (Philips UC Diagnost, Senographe DMRplus). RESULTS: Digital mammographies were equal to conventional ones in all cases and seemed to be superior in detecting microcalcifications in dense glandular tissue. Adequate assessment was possible despite the lower spatial resolution compared to conventional mammography. Additional magnified images were obtained with both techniques for differentiating microcalcifications. CONCLUSIONS: Digital full-field mammography appears to be at least equal to the conventional technique and even superior in some respects. In our experience, the lower spatial resolution of digital mammography has no major disadvantages. The digital system provides new options for electronic storage of mammograms, telemammography, and computer-aided diagnosis.

Breast Neoplasms↗

PubMed2000

[Typical and unusual findings in MR mammography].

In recent years, MR mammography has gained increasing importance in breast diagnostics. The main advantage of this technique is its high sensitivity for invasive breast cancer. The two main indications for MR mammography are preoperative staging of breast cancer and the differentiation between postoperative changes and recurrent tumor. In addition, MR mammography is increasingly used for problem solving in cases of questionable clinical, mammographic or sonographic findings. At this it is important to know not only the different manifestations of breast cancer, but also important benign and malignant diagnostic alternatives. Furthermore, it is necessary to be familiar with therapy-related changes. The most important criterion to differentiate between benign and malignant lesions in MR mammography is the extent and temporal course of contrast enhancement. In addition, the lesion morphology and the signal intensity on T2-weighted images can be used to distinguish between different disease entities. The following review article will discuss typical and unusual findings in breast MRI, including rare entities as well as changes after breast conserving therapy and chemotherapy.

Breast↗

PubMed2000

[Full-field digital mammography].

Due to the extremely high image quality requirements in mammography, there has for a long time been no adequate digital alternative to conventional film-screen mammography. The longest experience so far exists with digital mammography on the basis of storage phosphor (CR) systems. However, at normal dose this technique has a relatively poor signal-to-noise ratio and has not found general acceptance. Recently three novel systems for digital mammography by the companies Fischer (slot-scan detector), Trex (CCD-array), and GE (amorphous silicon detector) have been introduced and are currently under clinical investigation. The main advantage of digital mammography is the linear relationship between dose and detector signal with the possibility of a tailored optimization of image contrast. Other advantages include digital image storage, telemammography, and computer-assisted diagnosis.

Breast Neoplasms↗

PubMed2000

[Intraoperative digital radiography for diagnosis of nonpalpable breast lesions].

PURPOSE: A procedure for performing intraoperative digital radiography of diagnostic breast specimens directly in the operating suite with teleradiologic assessment by a radiologist is presented. The efficiency of this procedure is compared with that of conventional magnification mammography performed in the radiology department. MATERIAL AND METHODS: Thirty-six specimen radiographs obtained by conventional magnification mammography were compared with 38 intraoperative digital magnification radiographs (DIMA Soft P42 prototype, Feinfocus Inc., Garbsen). The radiographs were assessed for lesion conspicuity and time savings for the surgeon, anesthesiologist, and radiologist. RESULTS: The new procedure identified all 38 labeled pathological lesions, and the conventional technique likewise had a detection rate of 100% (36/36). The new technique resulted in considerable time savings for the surgeon and the radiologist. The duration of surgery was shorter and the time interval from removal of the specimen to reporting of the results was reduced from about 23 min to about 13 min. A single radiograph was sufficient for complete visualization of the specimen in all cases. CONCLUSION: Digital intraoperative specimen radiography considerably reduces the time of surgery depending on the local conditions and is highly accurate in locating a suspicious area within the tissue.

Breast Neoplasms↗

PubMed1999

PACS: the silent revolution.

More than 15 years ago the idea of a Picture Archiving and Communication System (PACS) and a filmless hospital was created. In a PACS environment images are acquired, read, communicated and stored digitally. After many years of unsuccessful attempts and prototype installations, the necessary hardware components for a successful PACS installation are now readily available. However, software development is still lagging behind. Only very recently, software developers have realized that it is not sufficient for PACS software to store, communicate and display images, but that PACS software should effectively support the radiologist in the task of interpreting and communicating imaging findings through context-dependent default display arrangements, work-flow management, radiological and hospital information systems integration, and computer-assisted diagnosis. This review examines hard- and software requirements for efficient PACS operation, analyses costs and benefits, and discusses future developments.

Cost-Benefit Analysis↗

PubMed1999

Experimental study of X-ray mammography in a fluid bath: reduced radiation dose and improved detail resolution.

OBJECTIVE: To determine the effects on x-ray mammography of embedding the breast in a fluid bath. METHODS: A plexiglass phantom in the shape of a compressed breast was x-rayed in air and water with a mammography unit, and the radiation dose was measured by 20 thermoluminescence dosimeters placed in 20 representative positions on the surface of the phantom. Udders from slaughtered sheep as an animal model and phantoms were examined by mammography in identical positions surrounded by air and different fluids. The images were evaluated for detail resolution subjectively (animal model) and objectively (phantom containing quantifiable structures) by 6 and 15 blinded readers, respectively. The readers' results were analyzed and compared for visualization of the objects in air versus fluid. RESULTS: Mammographic examination in the fluid bath reduced the radiation dose and improved detail resolution in the rounded margin of the breast. Also, viewing conditions in the central region were improved as a result of the uniform optical density across the entire film area. CONCLUSIONS: Performing x-ray mammography in a fluid bath has advantages that make the technical realization of this method desirable.

Air↗

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↗