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Biomedical subjects

A Melzer

Publications and source records attributed to A Melzer.

At least 37 records · Page 2Linked to original sources
PubMed1997

Deflectable endoscopic instrument system DENIS.

BACKGROUND: The degrees of intraoperative movement with rigid standard instruments during laparo-endoscopic surgery are limited to translation, rotation, and pivoting within the insertion point. Additional distal angulation and rotation of the instrument jaws are a potential improvement. METHODS: Different types of articulated instruments have been developed and tested in phantom and animal experiments. The final prototype was used on 30 patients during laparoscopic surgery following a standardized test protocol. RESULTS: The final design incorporates elastically linked tubular segments, 0-120 degrees variable curvature, and +/- 360 degrees rotation of the jaws element. All functions can be operated with one hand. Testing on phantom and in laparoscopic surgery showed improved handling of organs and tissue with no complications. CONCLUSION: We were able to demonstrate the feasibility of the technical design and the clinical applicability of a deflectable endoscopic instrument system. Although our initial results indicate an improvement in laparoscopic tissue manipulation, the current deflection and jaw rotation require further technical refinement.

Animals↗
PubMed1997

Computed Tomography- and Magnetic Resonance Imaging: Guided Microtherapy.

This report describes techniques of computed tomography (CT) and magnetic resonance imaging (MRI) image-guided diagnosis and therapy. Fine-needle biopsy, interstitial tumor therapy, and chemical sympathectomy, as well as the treatment of chronic spinal diseases, including periradicular infiltration at irritated spinal nerve roots, percutaneous laser decompression of intervertebral disks, and intraspinal microendoscopic scar dissection after failed back surgery are described. To overcome specific drawbacks of CT application, we have evaluated technological prerequisites and feasibility of MRI guidance of interventional procedures, such as biopsy, aspiration of neoplasm, and local interstitial drug instillation. New MR-compatible needles, trocars/cannulae, endoscopes, and ancillary equipment were developed and evaluated in collaboration with industry. Sequences, study protocols, and the strategies of performing the procedure within the environment of an interventional MRI suite have been formulated. In 168 patients, 204 interventions such as aspiration biopsy, peridural corticoid injection at spinal nerve roots, intratumoral ethanol instillation, chemical sympathectomy, and percutaneous laser decompression of herniated intervertebral disks were performed successfully. CT and MRI guidance of percutaneous and microendoscopic interventions provides a reproducible and precise means of instrument control. Aside from preoperative planning of the access trajectory, instruments can be placed under CT or MRI control and the therapeutic process can be monitored. Although MRI avoids the need for ionizing radiation and provides multiplanar multislice images with excellent soft tissue contrast, the representation of instruments and the resolution is currently inferior to that achieved by CT imaging.

Journal Article↗
PubMed1997

DNA-Protein Crosslinks and Sister Chromatid Exchanges as Biomarkers of Exposure to Formaldehyde.

Formaldehyde is classified as a probable human carcinogen. DNA-protein crosslinks (DPCs) and sister chromatid exchanges (SCEs) may represent early lesions in the carcinogenic process. The authors examined the DPCs and SCEs in peripheral-blood lymphocytes of 12 and 13 workers exposed to formaldehyde and eight and 20 unexposed workers, respectively. The amounts of DPCs and SCEs in the exposed and the unexposed differed significantly after adjustment for smoking. There was a linear relationship between years of exposure and the amounts of DPC and SCE. The authors conclude that the data indicate a possible mechanism of carcinogenicity of formaldehyde, and that formaldehyde is mutagenic to humans. These results support the use of DPCs as a biomarker of occupational exposure to formaldehyde and to detect high-risk populations for secondary prevention.

Journal Article↗
PubMed1996

[Occupation and bladder cancer].

The proportion of all cancers attributed to occupational environment has been estimated at only 4% (range 2-8%), although 20% of bladder carcinoma is occupationally related. In Israel, 7 substances have been established as bladder carcinogens and another 2 are suspected. The linkage between bladder cancer and occupation was examined according to occupational history and work-place exposure; smoking habits were also noted. The study population consisted of 1230 patients diagnosed as suffering from bladder cancer in 1988-1993 in 5 central hospitals; 80% were men, mean age 68.9 +/- 10.8 years. Only 41% of the files (mean 45%, range 13-69%) had information about last job, but no information on exposure. The information in 226 files out of 500 (45%) about previous occupations indicated potential association with bladder cancer in 68%. These occupational fields were: medicine (doctors, nurses), building and agriculture, and comprised 27.6% of all jobs reported. Other occupations connected with bladder cancer reported with lesser frequency were in the paint, rubber, textile and leather industries. There was information about smoking, a known carcinogen for bladder cancer, in only 59% of the files. Our findings indicate that the overall situation in Israel is similar to that in other countries. There is a connection between bladder cancer and exposure to carcinogens at work, but the medical files were not a good source of information regarding the precise extent of this problem. Recording occupational history is important for proper medical surveillance of high risk populations, for early detection of bladder cancer, and for prevention of further exposure.

Aged↗
PubMed1996

Equipment configuration and procedures: preferences for interventional microtherapy.

Magnetic resonance imaging (MRI), computed tomography, and electron beam tomography scanners are built for radiologic diagnosis. With increasing frequency they are being used in the field of interventional Microtherapy to permit transparent visualization of the therapeutic field. Each of these scanners can be combined with endoscopy, fluoroscopy/digital subtraction angiography, and ultrasound units for hybrid imaging techniques as well as with therapeutic systems like lasers or radiofrequency. MRI affords 3D localization without x-ray exposure. Open access and keyhole imaging allow nearly real time guidance of instruments. Minimally invasive techniques using endoscopes and hybrid tomographic guidance result in improved tip tracking of microinstruments and reduced complications. This safer access into the body will lead to interdisciplinary cooperation with the potential for large cost reductions. This report summarizes our experience regarding which of the hybrid imaging suites is best suited for procedures including among others drug instillations, prosthesis (stent) implantation, or microoperations (endoscopic diskectomy/sequestrectomy), and physiological measurements simultaneously.

Diagnostic Imaging↗
PubMed1996

Two- and three-dimensional imaging for interventional MRI and CT guidance.

Minimally invasive techniques using endoscopes for image guided therapy are common in the surgical field and in internal medicine. Interventional procedures in the past were performed with either fluoroscopic, sonographic or CT-guidance, but now MRI-guided interventional procedures are being developed. Combining these technologies will improve surgical access and reduce complications. Today, tomographic 2 D and 3 D imaging (CT, EBT, MRI) can be used for precise and transparent guidance of endoscopes and surgical instruments inside the body for the field of minimally invasive therapy. 3 D imaging is helpful for anatomical, but not for morphological understanding. It has to be used interactively with actual cross sectional imaging for instrument guidance. This will offer a safe and effective access into the body, especially in high risk areas and lead to the new field of "Surgical Tomography".

Endoscopes↗
PubMed1996

Experimental telemanipulation in endoscopic surgery.

Today's rigid endoscopic instruments limit the intracorporeal mobility of the surgical tool and are a severe impediment for the further spread of endoscopic techniques in operative medicine. Since 1992 flexible, steerable instruments with additional links for pivoting and rotating the tip have been developed and experimentally evaluated. The latest versions of this series of instruments are equipped with electromotors for better handling. The next aim in this development is a fully mobile telemanipulator with six motion axes dedicated to use in endoscopic surgery. Its first tests are planned for 1995. For successful operation of an electric telemanipulator, the man-machine interface (MMI) is of cardinal importance. For the definition of surgical requirements for the MMI, a conventional master-slave manipulator designed for technical application was modified for use in guiding a laparoscopic instrument. Master and slave sites of the system were 1.3 km apart and linked by means of a fiber-optic cable. Using this modified telepresence system, remote laparoscopic cholecystectomy was feasible in a phantom model. In a standardized test series using a test parcours, different parameters of the control system were modified, and their influence on the execution time of the parcours tasks was recorded. Well-suited parameter configurations were found and allowed experimental verification and completion of the important aspects of our concepts for development of an endoscopic manipulator MMI.

Cholecystectomy, Laparoscopic↗
PubMed1995

Effect of increased protein intake and nutritional status on whole-body protein metabolism of AIDS patients with weight loss.

The aim of this study was to investigate nutritional status and protein metabolism during total parenteral nutrition (TPN) in AIDS patients with weight loss. Six patients on treatment for AIDS-associated complications were investigated and reviewed TPN that supplied energy equivalent to 1.5 times the resting energy expenditure (REE). Amino acid (AA) supply increased from 0.6 g/kg body weight (BW)/d on days 1 to 3 and 1.2 on days 4 to 6 to 1.8 on days 7 to 9. Nonprotein energy was given as equicaloric amounts of glucose and fat emulsion. There were repeated measurements of nitrogen balance and whole-body protein turnover (WBPT) using a bolus 15N-glycine method on the morning of days 3, 6, and 9. Principal findings were as follows: (1) increasing the supply of AAs significantly improves nitrogen balance in AIDS patients; (2) there is no simple linear effect of increasing amounts of AAs on WBPT in AIDS patients; (3) WBPT is high and variable in these patients; and (4) mean WBPT of each patient is significantly correlated with body cell mass (BCM) as a proportion of BW (P < .001, r = .92). We conclude that poor nutritional status in AIDS patients with weight loss is associated with high WBPT. However, these patients can attain at least transiently positive nitrogen balance with sufficient protein intake, predominantly through an increase in whole-body protein synthesis (WBPS).

Acquired Immunodeficiency Syndrome↗
PubMed1995

Ports, Trocars/Cannulae, and Access Techniques.

One of the keys to safe laparo-endoscopic surgery is an expeditious, reliable, and safe access to the operative field. Aside from appropriate surgical technique, the technology of trocars, cannulae, and other endoscopically guided insertion techniques plays a decisive role for safe identification of and access to the peritoneal cavity. This report takes a close look at critical features of trocar and cannula design for blind insertion with the focus on the biomechanical principles involved in traversing the abdominal wall. Particular attention has been paid to techniques minimizing the risk of accidental injury to major vessels, intestine, and other important structures. The principle of controlled visualized access led to several developments in the field of trocars, cannulae, and puncture techniques. Aside from blind and open access with the Veress needle, conventional trocars and cannulae, a selected variety of endoscopically assisted ports such as the optical Veress needle, optical trocars and optical scalpel, and a vacuum-supported access system are described in detail.

Journal Article↗
PubMed1995

Using shape-memory alloys.

Design considerations and material selection play important roles in the development of surgical instruments for minimally-invasive procedures. Substituting shape-memory or superelastic metals or alloys for conventional materials can lead to a significant improvement in the overall performance of those instruments. In addition, simplicity of design, a reduced number of parts, and ease of assembly and disassembly result in cost reductions.

Alloys↗
PubMed1995

Endoscopically controlled trocar and cannula insertion.

One of the keys to safe laparoscopic or thoracoscopic surgery is an expeditious and reliable access to the region of interest. To minimise the risk of accidental injury to major vessels, lung, intestine and other important structures the principle of controlled visualised access has been advocated. This has led to several developments in the field of trocars, cannulae and puncture techniques. Examples are the insertion of a needle scope into a Veress needle, complex access cannulae and our new principle of using an "optical scalpel". The direct visualisation of an active, controllable penetration of the abdominal wall is expected to become indispensable. A selected variety of endoscopically assisted trocar and cannula systems such as the "windowed trocar", the "optical trocar", the "Visiport" and the "optical scalpel" are described.

Catheterization↗
PubMed1995

Image-guided access techniques.

For increasing safety in access and guidance of endoscopes and instruments, fast real-time radiologic imaging should be integrated. Open designed Magnetic Resonance Imaging (MRI), Computer Tomography (CT), and Electron Beam Tomography (EBT) scanners permit adequate transparency of the operative field. CT and EBT as hybrid scanners can be combined with fluoroscopy. MRI avoids X-ray exposure and entails the possibility of 3D localisation, while open access and keyhole imaging allows nearly real-time guidance of instruments. EBT has the largest gantry (90 cm) for using long instruments, and the image acquisition requires only 50 msec (34 images/sec at 8 levels). However, computed reconstruction of the data takes about 3 times longer than conventional CT. Until EBT can be accelerated, CT will be the golden standard of guidance-techniques in high risk areas, because the tips of the instruments can be precisely visualised within +/- 0.5 mm (MRI: 3.5 mm). MRI-guidance can be used for low risk access techniques. This safe interactive transparent guidance technique has the potential to reduce complications, and it adds significant advantages to micro-invasive operative procedures such as percutaneous diskectomies, pain and cancer therapy with ethanol, or gene-technology implants in the new field of "surgical tomography".

Diagnostic Imaging↗
PubMed1994

Future trends in endoscopic suturing.

This paper deals with future aspects and developments in endoscopic sutures, needles, needle drivers, and sewing devices. Shape memory alloys such as superelastic nickel-titanium can be used for surgical needles and hingeless needle drivers. A sewing device consists of a T-Needle which can be shuttled between the jaws of specially designed instruments. The jaws possess small elements that grip the needle tips. The "Needle Rotor" facilitates intracorporeal swivelling and positioning of the needle because one jaw can be moved longitudinally over the other. A new "cutting knot pusher" permits immediate cutting of a slip knot subsequent to tightening.

Anastomosis, Surgical↗