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Biomedical subjects

S Pieper

Publications and source records attributed to S Pieper.

14 recordsLinked to original sources
PubMed2006

Robot-assisted needle placement in open-MRI: system architecture, integration and validation.

This work describes an integrated system for planning and performing percutaneous procedures-such as prostate biopsy-with robotic assistance under MRI-guidance. The physician interacts with a planning interface in order to specify the set of desired needle trajectories, based on anatomical structures and lesions observed in the patient's MR images. All image-space coordinates are automatically computed, and used to position a needle guide by means of an MRI-compatible robotic manipulator, thus avoiding the limitations of the traditional fixed needle template. Direct control of real-time imaging aids visualization of the needle as it is manually inserted through the guide. Results from in-scanner phantom experiments are provided.

Biopsy, Needle↗
PubMed2001

An enabling system for echocardiography providing adaptive support through behavioral analysis.

Echocardiography requires the integrated application of a broad spectrum of cognitive and practical skills, e.g. diagnostic knowledge (symbolic), image interpretation (visual perception) and handling of the ultrasound probe (sensorimotor). This complex expertise is acquired through extensive practical training guided by a skilled cardiologist that is often incompatible with clinical reality. Especially for beginners, the most critical point during an echocardiographic examination is the steering of the ultrasound probe to navigate between different cardiological standard planes (sensorimotor skill) without loosing orientation. These transitions or "standard trajectories" can roughly be described by specific movement patterns. We propose an enabling system based on an Augmented Reality simulator for two-dimensional echocardiography imitating this apprenticeship [1]-[3]. During a simulated ultrasound examination the system monitors the activities of the trainee and analyzes the motion pattern of the ultrasound probe. The simulator reacts by mapping the motion patterns onto cognitive orientation demands and providing adaptive feedback in the form of context sensitive help (animations). It partly takes the role of the critical teacher.

Computer-Assisted Instruction↗
PubMed2000

Augmented reality simulator for training in two-dimensional echocardiography.

In two-dimensional echocardiography the sonographer must synthesize multiple tomographic slices into a mental three-dimensional (3D) model of the heart. Computer graphics and virtual reality environments are ideal to visualize complex 3D spatial relationships. In augmented reality (AR) applications, real and virtual image data are linked, to increase the information content. In the presented AR simulator a 3D surface model of the human heart is linked with echocardiographic volume data sets. The 3D echocardiographic data sets are registered with the heart model to establish spatial and temporal congruence. The heart model, together with an animated ultrasound sector represents a reference scenario, which displays the currently selected two-dimensional echocardiographic cutting plane calculated from the volume data set. Modifications of the cutting plane within the echocardiographic data are transferred and visualized simultaneously and in real time within the reference scenario. The trainee can interactively explore the 3D heart model and the registered 3D echocardiographic data sets by an animated ultrasound probe, whose position is controlled by an electromagnetic tracking system. The tracking system is attached to a dummy transducer and placed on a plastic puppet to give a realistic impression of a two-dimensional echocardiographic examination.

Computer Graphics↗
PubMed2000

Thoracoscopically assisted ligamentous release of the thoracic spine: a cadaver study.

The surgical treatment of thoracic kyphosis frequently requires an anterior release, which can be carried out by an open or endoscopic technique. This study concerns the reference points which are essential from the anatomic view for minimizing the operative risks. Furthermore we wanted to find the most convenient video-assisted thoracoscopic surgery (VATS) technique for transection of the anterior longitudinal ligament (ALL). Transection of the ALL, as well as discectomy, was performed using this technique. The extensive anatomic dissection of 12 fresh cadavers was performed to define possible technical errors and surgical complications. The development of new instruments has made the VATS approach to the ALL a viable alternative to open procedures. With the help of a standardized technique, the isolated thoracoscopic ligamentous transection required less time than the comparable open procedure. The anatomic study showed, that in no case was a ligation of the intercostal or segmental vessels necessary as part of the approach to the spine, once an adequate mobilization of the esophagus and azygos vein had been carried out. The risk of an ischemic lesion of the spinal cord was thereby reduced. The thoracoscopic, limited anterior release consisting of a multilevel transection of the ALL proved to be a rapid and reliable procedure. Our anatomic studies provides suitable the reference points.

Adult↗
PubMed2000

[Augmented reality in echocardiography. A new method of computer-assisted training and image processing using virtual and real three-dimensional data sets].

Augmented reality (AR) applications link real with virtual image data, in order to increase their information content. In medicine they are especially useful for education and for supporting the interpretation of three-dimensional (3D) image data. Simulators are used to train risky or expensive procedures. In the AR application EchoCom2 a 3D surface model of the human heart is linked with echocardiographic volume data sets. The 3D echocardiographic data sets are registered with the heart model to synchronize it's temporal and spatial orientation. The heart model together with an animated ultrasound sector represents a reference scenario, which displays the currently selected cutting plane within the echocardiographic volume data set. Modifications of the cutting plane within the echocardiographic data are transferred simultaneously and in real time to the reference scenario. The AR application is used as a simulator to train two-dimensional echocardiographic examinations and as an orientation and navigation aid for the exploration of 3D echocardiographic data sets. Beginners in echocardiography have only a rudimentary conception of the spatial relationship between the actual ultrasound image and the 3D anatomy of the heart. They are unable to translate multiple two-dimensional slices into a coherent 3D mental image of the heart. In EchoCom2 the trainee can interactively explore the 3D heart model and the registered 3D echocardiographic data sets by the animated ultrasound sector, whose position is controlled by an electromagnetic orientation and position system (EPOS). The data from the EPOS are used to calculate the echocardiographic images that are analogue to the position of the animated ultrasound sector. EchoCom2 is also used to support the interpretation of 3D echocardiographic data sets. The analysis of 3D echocardiographic data has to be done during a post processing. Defining the exact position of a cutting plane within the volume is difficult due to the lack of a standardized representation, the independence of the cutting plane of any transducer position and the possibility to calculate an indefinite number of views. The simultaneous representation of the current cutting plane both in the volume data, and in the heart model enables the examiner ad hoc to recognize it's position and the visualized structures.

Computer Simulation↗
PubMed1996

Screening of selected basidiomycetes for inhibitory activity on neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE).

Aqueous extracts of 27 basidiomycetes were investigated for their ability to inhibit the activity of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). The extracts of 5 fungi inhibited both, ACE and NEP activity, another 18 extracts showed inhibition of the NEP activity whereas only 1 basidiomycete inhibited the ACE activity exclusively. The IC50 values for the ACE inhibition are rather high (between 200 and 1500 micrograms/ml) in comparison to the IC50 of the NEP inhibition (between 40 and 2000 micrograms/ml). These results indicate that the basidiomycetes investigated seem to have a higher potential for the inhibition of the activity of NEP than of ACE. In general, basidiomycetes are a new source for inhibitors of metalloendopeptidases. Resulting from the isolation and characterization of these compounds new leading structures are expectable.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1988

Increased ornithine decarboxylase activity in cultured cells exposed to low energy modulated microwave fields and phorbol ester tumor promoters.

Ornithine decarboxylase (ODC) is present in all nucleated cells and is the rate-limiting enzyme for synthesis of polyamines. In turn, the polyamines are required for DNA synthesis and cell growth. In Reuber H35 hepatoma cells, we show that ODC activity is increased by about 50% during exposure to a 1-h "athermal" (less than 0.1 degree C temperature rise) (450 MHz, 1.0 mW/cm2 peak-envelope-power) microwave field sinusoidally amplitude-modulated at 16 Hz. The increased activity of ODC persisted for several hours following the 1-h exposure to the field. A similar field amplitude-modulated at 60 and 100 Hz did not alter the hepatoma cell ODC activity. The stimulated ODC activity in the cultured cells that followed treatment with a phorbol ester tumor promoter (12-O-tetradecanoylphorbol-13-acetate) was further potentiated by prior exposure to the same low energy electromagnetic field. This field did not alter either basal or 12-O-tetradecanoylphorbol-13-acetate-stimulated DNA synthesis. We observed a similar increase in the basal ODC activity of cultures of two additional cell lines (Chinese hamster ovary; and 294T melanoma) exposed for 1 h to the amplitude-modulated field. Chinese hamster ovary cells exposed to the radio frequency field for 1 h also responded to subsequent treatment with 12-O-tetradecanoylphorbol-13-acetate by exhibiting a further increase in ODC activity. We have observed previously that the activity of this enzyme is increased in cultured cells following a transient exposure to a 60-Hz electric field. Altered ODC activity may serve as a sensitive and specific molecular marker of the transductive coupling of weak pericellular electromagnetic fields to biological systems.

Animals↗
PubMed1988

In vivo effects of nifedipine and BAY 1 8201 on ceruletide induced gallbladder contraction.

Studies in animals suggest that calcium channel blockers may influence gallbladder contraction. In order to study possible actions in man we examined by ultrasonography the effects of two dihydropyridine derivatives, i.e. nifedipine (20 mg p. o.) and BAY 1 8201 (100 mg p.o.) on ceruletide induced human gallbladder contraction in 9 healthy male volunteers in a randomized, double-blind, three fold crossover study (latin square design). Blood samples for the measurement of plasma drug concentrations were drawn before and at regular intervals up to 8 h after drug ingestion. Ceruletide decreased gallbladder volumes by 52.1 +/- 8.2% (mean +/- 1 SEM) after nifedipine, 53.1 +/- 8.1% after BAY 1 8201 and by 59.3 +/- 10.1% after placebo (NS). Peak plasma concentrations of 53.7 x/: 2.3 ng/ml (geometric mean x/: geometric standard deviation) and of 35.5 x/: 1.5 ng/ml were reached after oral application of nifedipine and BAY 1 8201, respectively. We conclude that human gallbladder contraction in response to ceruletide is not markedly influenced by dihydropyridine derivates in the dosages used in this study. The results reported here stress the importance of calcium released from intracellular stores for the contractility of smooth muscle in the human gallbladder.

Adult↗
PubMed1968

Basic psychiatric literature. I. Books.

Widely varying recommended reading lists for psychiatry residents were obtained from 140 AMA-approved training programs. Approximately 4,000 articles, 2,800 books, and 200 serials were listed. The number of recommendations for each book was counted, and a rank-order determined. A second rank-order was determined from the lists of those eighty-seven programs which indicated that their material covered the "basic" literature; a third rank-order was determined from the number of residents using the lists. All rank-orders agreed on the "most recommended" book and the first eighteen books; there was a 92 percent correlation through the first 453 books. One-third of the "basic" recommendations were for the first 104 books; one-third for the next 349 books, and one-third for the remaining 1,994 books. The subject matter of the first 104 books indicated that the currently most popular subjects in psychiatry are psychoanalytic theories of personality, schizophrenia, psychotherapy, and child psychiatry. A list of the 104 most recommended books is appended.

Bibliographies as Topic↗
PubMed1968

Basic psychiatric literature. II. Articles and article sources.

Widely varying reading lists for general psychiatry residents were obtained from 140 three-year approved training programs. The material recommended for reading was listed on index cards, and the number of programs recommending each item was posted on the cards. Approximately 4,000 articles, 2,800 books, and 200 serials were recommended. A statistical evaluation of the book list appeared in a previous paper (3).(*) Part II is a similar evaluation of the article list and the limited editions and serials in which the articles appear.

Bibliographies as Topic↗