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Biomedical subjects

G Graschew

Publications and source records attributed to G Graschew.

12 recordsLinked to original sources
PubMed2000

Interactive telemedicine in the operating theatre of the future.

An experimental stereoscopic system has been established in the Robert-Rössle-Klinik, including four operating theatres and the surgical research unit OP 2000. The system allows local three-dimensional image acquisition, local stereoscopic video display, in-house stereoscopic video transmission and stereoscopic links to external partners. The goal is to make high-quality patient data available in a medical centre or over a collaborative network of medical experts. In future the requirements of teleconsultation in terms of image quality and bandwidth will be heterogeneous. A sophisticated medical telecommunication system for second opinions is needed that can take advantage of intelligent compression approaches (e.g. wavelet compression) to archive, to search for image content and to transmit medical data such as images.

Forecasting↗
PubMed1999

Telemedicine: the new must for surgery.

The vision of telesurgery comprises a multitude of new communicative elements influencing the way surgeons will treat their patients in the future. The first prerequisite for effective telecommunication is to digitize surgical data. Many medical imaging modalities provide primarily digital data sets, and digital image communication is already entering clinical practice under the labels of teleradiology and telepathology. However, for any surgical purpose, images must refer to tissues. Three-dimensional image reconstruction is warranted, and if such data shall be useful during surgery, different image sources must be combined into some virtual, multiparametric body model and matched to an intraoperatively distorted organ contour. A multitude of detail problems arise, beginning with image standards, data interfaces, data transport, image fusion, registering, contour matching, and, once the data are integrated, all the aspects of surgery-suitable data display and interaction. We refer here to several demonstration projects illustrating such a complex surgical data set and its interactive telecommunication. In all instances, telecommunication was to enable a concentration of distributed medical intelligence at the site where the patient was treated. With further technological development, such telesurgical applications will have a growing influence on patient management and surgical decision making. In the very near future, computer-aided navigation and robotic assistance, based on the same surgical data sets, will be available to all fields of surgery. How decisive the role these methods will play for specific procedures or diseases needs to be determined.

Computer Simulation↗
PubMed1998

A chemical dosimeter for the determination of the photodynamic activity of photosensitizers.

Uric acid a known singlet oxygen scavenger, was investigated as a chemical dosimeter in physiological aqueous solution for use in photodynamic therapy. The uric acid test takes the decrease in uric acid (UA) absorbance at 293 nm after laser light irradiation of a solution containing UA and a photosensitizer as a rapid evaluation of relative photodynamic activities of the photosensitizer. A uric acid test standard procedure was defined. To compare photodynamic activity of different photosensitizers or irradiation conditions a proposal for a photodynamic activity scale based on the uric acid test is given. Examples of uric acid test operation are given by comparing the changes in UA absorbance decrease with respect to irradiation wavelength and to photosensitizer concentration of Photofrin II with that of two other photosensitizers (5,10,15,20-tetrakis-[4-hydroxyphenyl]-21H,23H-porphyrin (TOP) and 5,10,15,20-tetrakis-[4-carboxyphenyl)-21H, 23H-porphyrin (TCPP), both derivatized with methoxypolyethyleneglycol (TOP-MPV and TCPP-AMP) as a macromolecular carrier). The photodynamic activity of the three photosensitizers using the proposed photodynamic activity scale is given.

Dihematoporphyrin Ether↗
PubMed1998

[Teleconference and telesurgery].

Interchange of information has become possible independent of the user's place or time by modern telemedical services and opens up new dimensions for diagnostic and therapeutic procedures. For teleconferences and teleconsultations in surgery, the intraoperative high-quality transmission of live images is essential without disturbing the sterility and operation routine. The clinical specifications require special systems for broadband, stereoscopic online image transmission both intra- and inter-institutionally. Moreover, a telemedical concept integrates the communication equipment suitable for the different diagnostic and functional facilities of a clinic, a digital multimedia patient record and modules for cooperative working. These implementations are a prerequisite for extensive telesurgical interventions using navigational tools, guided instruments or autonomous roboter systems. The realization of such a comprehensive telesurgical concept (OP 2000) is presented.

Computer Communication Networks↗
PubMed1998

[Virtual operations on real patients].

The tremendous amount of available medical digital data requires media for intuitive information perception. Virtual reality (VR) presents a technique for processing the visual data from various diagnostic modalities. From a synthetic patient model, the required compact information can be generated. The patient model is the basis for planning and processing of surgical procedures. Stereoscopically visualized 3-D reconstructions of, for example, tomographic scans are used for virtual operations. Today, prototypical tools for the virtual training of certain surgical procedures are known. Possible VR applications in surgery range from the combination of virtual and real data (augmented reality) and intraoperative computer assistance (navigation) to remotely performed operations (telerobotics). In particular, the optimization of the man-machine interface to integrate VR applications in operating theaters is required.

Computer Systems↗
PubMed1998

[Telecommunication in routine surgical practice].

In an internal inquiry on the use of telecommunication, 267 operations were documented. In 62 cases an interruption was necessary: 43 of them for a second opinion and 29 for a new orientation resulting from findings, and in 10 cases for both. A purely verbal communication/consultation was sufficient in 8 cases, in 29 questions an on-site demonstration was necessary to come to a decision. In the opinion of the operating surgeon, a picture transmission telecommunication system would have been helpful for solving the problem in 27 (44%) of the interruptions. Looking at the minimal invasive operations, the percentage was specially high (60%). We think that in future telecommunication systems can be used for time saving in operating rooms and on a long-term basis contribute to cost cutting and quality improvement in surgical routine.

Forecasting↗
PubMed1997

[Techniques in teleconsultation].

The aim of the new developments in telemedicine is to optimize medical care by the use of new communication technologies. Teleconsultation is a basic component of telemedicine. Telepresence systems demand high-quality video transmissions and interactive communication. Comparison of the quality of the transmitted pictures demonstrates that an ISDN connection is not suitable for live video transmissions. In contrast to this the SICONET/OP 2000 communication module allows the setup of an interactive telepresence system with 3D visualization in broadcast quality.

Computer Systems↗
PubMed1990

31P NMR studies of cultured human tumor cells. Influence of pH on phospholipid metabolite levels and the detection of cytidine 5'-diphosphate choline.

202 MHz 31P NMR (11.7 T) was used to study the effects of culture medium pH on the levels of phosphate metabolites in three human tumor cell lines (XP29MAmal, a malignant xeroderma pigmentosum; CX-1, a colon carcinoma; KB, a squamous cell carcinoma of the oral cavity). Cells were cultured in Roux flasks in HAM's F-12 medium, and the pH was varied with the final medium change. After harvesting, 1-5 x 10(8) cells were suspended in Ringer/HEPES buffer at pH 7.4 and 4 degrees C for 31P NMR studies. Cell adhesion and growth rate decreased with decreasing pH, but, down to ca pH 6.1, trypan blue exclusion and the observed levels of nucleoside di- and triphosphates (range: 22-37% of total phosphates detected), phosphocreatine (PCr, 2-5%) and Pi (5-11%) did not vary significantly with pH. For XP29MAmal cells in exponential growth phosphocholine levels decreased from 18-28% at pH 7.0 to ca 5% at pH 6.0, while phosphoethanolamine levels increased from 2-7% to 15%. Glycerophosphocholine (GPC) levels increased from ca 7% at pH 7.2 to 13% at pH 6.3. At pH less than 6.3 cytidine 5'-diphosphate (CDP) choline became detectable (8-16%, delta p:P alpha = -8.13 ppm, P beta = 8.93 ppm, for PCr = 0 ppm). However, confluent cells did not accumulate CDP-choline when the pH was lowered. The cell lines CX-1 and KB also showed the pH effects described herein.

Choline↗
PubMed1990

Synthesis of positively charged phthalocyanines and their activity in the photodynamic therapy of cancer cells.

Positively charged zinc containing or metal free phthalocyanines 6a-c and 7a-c were prepared via a three step procedure starting from 4-nitrophthalonitrile. The phthalocyanines contain alkyl chains of different length in order to influence the hydrophilic vs lipophilic character of the compounds. The partition between a hydrophilic (water) and lipophilic (octanol-1) phase was determined, and the photoredox activities were investigated. Initial results on the photodynamic activity of these compounds were compared with those of Dougherty's Photofrin II on different malignant and non-malignant cell lines (XP 29MAmal, CX1, HeLa, S180 and NO17). Positively charged phthalocyanines in vitro showed a higher photodynamic activity than Photofrin II.

Animals↗