Biomedical subjects
Publications and source records attributed to A Melzer.
Ultrasound imaging is a process involving the real-time interaction of the physician with both the imaging equipment and the tissue. A good understanding of the physical principles involved in creating the image will ensure optimal handling of the equipment and proper interpretation of the resulting image.
A combination of laparoscopic and rectoscopic procedures has enabled complete resection of the sigmoid colon and eliminated the need for minilaparotomy when constructing the anastomosis or withdrawing the specimen. This combined procedure was performed in different ways in a series of animal models until the definitive technique had been standardized. These techniques were then successfully used in 15 consecutive medium-sized pigs. Histological evaluation of the specimens, including the anastomosis (examined 2-3 weeks after operation) confirmed the efficacy and safety of the method.
Explore the source record for details and available documents.
A one year research programme on endoscopic colorectal resections was carried out at the University of Tübingen. Two research lines were planned: the development of the required technologies and the development of the surgical procedure. During the research programme on technologies a new device provided with an air proof system for transanal insertion of the anvil of a divisible stapler and a new technique for closure of the colonic and rectal stumps (cable binding technique) were developed. Such technological innovations enabled the authors to accomplish a new combined laparoscopic-rectoscopic procedure which was performed according to four different variants in a series of 32 animals. The last 15 consecutive successful cases, performed according to the definitive procedure, represented a standardized animal trial before starting the clinical investigation.
Three-dimensional visualisation of the operative field is an important requisite for precise and fast handling of open surgical operations. Up to now it has only been possible to display a two-dimensional image on the monitor during endoscopic procedures. The increasing complexity of minimal invasive interventions requires endoscopic suturing and ligatures of larger vessels which are difficult to perform without the impression of space. Three-dimensional vision therefore may decrease the operative risk, accelerate interventions and widen the operative spectrum. In April 1992 a 3-D video system developed at the Nuclear Research Center Karlsruhe, Germany (IAI Institute) was applied in various animal experimental procedures and clinically in laparoscopic cholecystectomy. The system works with a single monitor and active high-speed shutter glasses. Our first trials with this new 3-D imaging system clearly showed a facilitation of complex surgical manoeuvres like mobilisation of organs, preparation in the deep space and suture techniques. The 3-D-system introduced in this article will enter the market in 1993 (Opticon Co., Karlsruhe, Germany.
The importance of a safer approach to the abdominal cavity 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". In our view, direct optical visualization and actively controllable penetration of the abdominal wall are mandatory. First experimental and clinical applications indicate the newly developed "optical scalpel" (Olympus Winter & Ibe, Hamburg, Germany) as a reliable and useful instrument for a safe approach to the endoscopic operative field. This instrument was successfully used in 10 endoscopic operations and is currently undergoing further clinical testing.
Throughout history "medicus" and "technicus" worked closely in the design of surgical instruments. The early tools were relatively primitive in modern terms but most of them achieved the purpose for which they were designed. In recent centuries numerous surgical instruments were pioneered to execute a variety of tasks. As surgical and technical skills developed some instruments were modified while others were abandoned. Many instruments used in conventional open surgery have obviously stood the test of time, though they have been continuously adapted to the current requirements, the available surgical skills and preference. More recently instrument design and manufacture has been taken over by industry. There are a variety of reasons as to why this may have been an important and advantageous step but the main disadvantage lies in the reduction in the cooperation between "medicus" and "technicus".
The recent progress in endoscopic surgery, which is highlighted by the complexity of fundoplication, stomach surgery and colorectal surgery, has revealed major restrictions with difficult surgical manipulations. Mobilisation, dissection and suturing techniques are hampered mainly by the limited degrees of freedom of the conventional rigid instruments (translation along and rotation around the longitudinal axis and the limited play in the access channel). The frequent interchange of instruments such as coagulation forceps, scissors and suction-irrigation probe is time-consuming. We have established an interdisciplinary development model with the aim of improving surgical technology, instrument systems, the operation theatre and its environment. Concepts of electronic instrument control and sensoric feedback, and the features of the surgical man-machine-interface are described. The first prototypes of an intelligent steerable instrument system, ISIS, and its optional effectors, e.g. semiautomatic sewing device and multifunctional coagulation instrument, were tested in phantom and animal experiments. System analysis will lead to specially designed operating theatres (minimal invasive surgical operating system MINOS).
The laparoscopic cholecystotomy was developed to remove calculi while preserving a functioning gallbladder. 120 phantom tests on pig's gallbladders were performed. No major complications were observed in 20 animal experiments with pigs. Compared with competing conservative and interventional methods the laparoscopic cholecystotomy provides immediate removal of stones and a definite closure of the gallbladder by a clip. Calcified stones are no contraindication for the procedure. After introduction into the clinical routine, an outpatient treatment in local anaesthesia seems to be possible. Patients with a high operative risk should be treated by this method. The laparoscopic cholecystotomy represents an alternative to the percutaneous transhepatic litholysis and the ESWL.
This instrument set for a single puncture technique of laparoscopic cholecystotomy was developed in 100 phantom tests with pig gallbladders and was later evaluated in 12 animal experiments. No complications were observed. After clinical development, treatment on an outpatient basis under local anaesthesia seems possible. For the patient this would mean avoiding general anaesthesia, shorter hospitalization, pain reduction and good cosmetic results, while reducing expenditure for the public health authorities at the same time. To avoid recurrent stones, diet and low-dose drug therapy should be considered. Because the procedure is minimally invasive, repetition of the laparoscopic procedure seems justified if stones recur.
A new endoscopic microsurgical technique for dissection of the esophagus has been developed and tried out in animals. With this technique the esophagus is dissected and removed via a cervical approach by means of a new operating endoscope. In a randomized animal study we compared endoscopic versus blunt dissection and versus abdominothoracic resection. During endoscopic dissection we saw significantly lower bleeding and no laceration of the pleural cavity or damage to the recurrent laryngeal or to the vagus nerve. Significant changes of hemodynamics or gas exchange were observed in the blunt dissection group: increase of heart frequency, decrease of arterial pressure and decrease of paO2. In contrast these parameters did not change in the endoscopic group.
Explore the source record for details and available documents.
Blunt dissection of the esophagus is considered the least invasive technique in the treatment of either benign or malignant diseases of the esophagus. Its disadvantage is that it has to be carried out blindly. The results may be uncontrollable hemorrhage, unrecognized injuries to the trachea, and damage to the recurrent laryngeal nerve. In order to reduce the degree of invasiveness a new endoscopic microsurgical technique for the dissection of the esophagus has been developed and tried out in animals. This paper presents the operative technique. Our new endoscopic microsurgical technique obviates a thoracotomy, while direct endoscopic vision results in improved dissection. The magnified endoscopic view permits selective exposure of blood vessels and prevents injury to the adjacent organs.
Nutriflex 48 (48 g amino acids and 1250 nonprotein kcal/l), containing 20% branched chain amino acids, was infused in a dose of 2000 ml per day over a period of 14 days to 8 surgical intensive care patients with sepsis and concomitant liver dysfunction. Cumulative nitrogen balance was negative on each day of investigation, as aspected in those patients. The amino acid patterns in plasma showed increased concentrations of methionin, while the concentration of branched chain amino acids remained in the normal range until the end of the study. The concentration of plasma ammonium was always normal. These results seem to indicate that in septic patients a total parenteral nutrition with conventional amino acid solutions containing normal concentrations of branched chain amino acids, is possible. The results of the present study show that the necessity of parenteral nutrition in septic patients with highly branched chain amino acids can not be supported.
Steadfast progress has been made from biopsy to surgery with interventional MRI (iMRI). Such image-guided interventions require specialized instrumentation due to the unusual elements of the MR environment. Suppliers/manufacturers of MR-compatible instrumentation were few in 1994, but now there are more than 50. We present fundamental issues of MR compatibility and a list of known suppliers/manufacturers.
The tools and devices used for patient treatment during interventional procedures must be accurately and safely localized. Recently, procedure guidance has been performed increasingly with MRI, but tool localization has been performed primarily by analyzing the lack of signal caused by displaced excited tissue and/or susceptibility artifacts. In this investigation, a new technique was developed to actively detect and visualize interventional tools using receive coils mounted on the tip of the interventional devices. Unlike earlier methods, in which images from small device-mounted coils are super-imposed on a previously acquired image data set, our localization method uses similar tip-mounted tools in combination with a radiofrequency (RF) switching circuit, standard imaging coils, and specially modified sequences to toggle between the standard and tip-mounted receive coil within a single fluoroscopic mode sequence. With this technique, the misregistration between the reported anatomic location and true location of interventional devices is minimized.
Explore the source record for details and available documents.