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Biomedical subjects

J Pensel

Publications and source records attributed to J Pensel.

At least 19 recordsLinked to original sources

[Antibiotic prophylaxis with enoxacin in extracorporeal shockwave lithotripsy].

According to literature, 16 to 35% of operatively removed renal stones harbour bacteria. The efficacy of antibiotic prophylaxis with enoxacin in reducing the rate of bacteriuria after extracorporeal shock wave lithotripsy (ESWL) was investigated in a prospective randomized study. Twenty-five patients received a single 400 mg dose of enoxacin one hour before ESWL, 25 patients did not receive an antibiotic. It was found that a single 400 mg dose of enoxacin one hour before ESWL can reduce the rate of bacteriuria significantly.

Bacteriuria↗

The pulsed dye laser versus the Q-switched Nd:YAG laser in laser-induced shock-wave lithotripsy.

To date, there are two fairly well-established alternatives for laser-induced shock-wave lithotripsy in clinical practice. The Q-switched Nd:YAG laser is distinguished by the high-stone selectivity of its coupler systems. The necessity of a coupler system and its fairly small conversion rate of light energy into mechanical energy present serious drawbacks. Furthermore, the minimal outer diameter of the transmission system is 1.8 mm. The pulsed-dye laser can be used with a highly flexible and uncomplicated 200-micron fiber. However, the laser system itself is more complicated than the Q-switched Nd:YAG laser and requires a great deal of maintenance. Biological evaluation of damage caused by direct irradiation shows that both laser systems produce minor damage of different degrees. YAG laser lithotripsy with the optomechanical coupler was assessed in 31 patients with ureteral calculi. The instability and limited effectiveness of the fiber application system necessitated auxiliary lithotripsy methods in 14 cases. Dye-laser lithotripsy is currently being tested in clinical application. Further development, such as systems for blind application or electronic feedback mechanisms to limit adverse tissue effects, have yet to be optimized. Nevertheless, laser-induced shock-wave lithotripsy has the potential to become a standard procedure in the endourologic management of stone disease.

Animals↗

Functional and histological restitution in the urinary tract after Nd:YAG laser coagulation.

Current development in endourologic equipment has made possible the endoscopic application of the Nd:YAG laser in the treatment of urothelial tumors of the whole urinary tract. The clinical results are rather promising. We controlled with various methods the healing processes of 14 rabbit ureters after Nd:YAG laser treatment as to morphological repair and physiological function. The ureters were irradiated transrenally with an energy of 60 J coagulating all wall layers. Healing of the laser lesions nearly to normal in all animals was observed 4 to 6 weeks after treatment. The prevailing histological and physiological changes in the ureter are extremely slight and do not disturb the normal ureteral function. The results show the complete healing process of the ureter after laser coagulation and make the application of Nd:YAG laser in the upper urinary tract much more predictable.

Animals↗

Regulated high frequency diathermy for bipolar electrocoagulation--a new method for the treatment of carcinoma of the bladder.

In the endoscopic treatment of bladder cancer, especially for stages beyond T2, transurethral resection does not seem to be sufficient. The risk of bladder wall perforation, the possibility of incomplete resection, seeding of tumor cells and high recurrence rates support the former statement [6]. Results of a multicentre prospective randomised study have exemplified that irradiation with the Neodymium-YAG Laser has been a reasonable alternative in the therapeutic approach to bladder cancer [2]. Diathermy coagulation must produce a sufficiently deep, homogeneous and well demarcated tissue necrosis. The coagulation depth has to be adjustable and heat production during coagulation should not lead to bladder wall perforation and consequent damage to the bowel. These criteria were investigated using regulated bipolar high frequency diathermy. The innovation in this method is, that thermal side effects on the tissue, e.g. vaporisation and carbonisation are prevented by a protective relay with constant current flow. Animal experimental studies have shown that this method meets all postulated requirements and therefore clinical trials can proceed.

Animals↗

Dosimetry of the neodymium-YAG laser in urological applications.

Animal experiments were carried out to optimize laser parameters for the treatment of superficial bladder tumors. The most important parameter affecting laser therapy is temperature. During intravesical irradiation of rabbit bladders, spatial and temporal temperature profiles on the bladder serosa were displayed. With these results adequate and safe treatment of bladder tumors is possible. We were unable to find any reduction in the hydrostatic capacity within the physiological range of bladder filling after laser irradiation of even 30% of the wall. Large diverticula developed within the first days after treatment, but had almost disappeared after 40 days.

Animals↗

Transurethral laser coagulation for treatment of urinary bladder tumors.

Owing to the biophysical properties involved, the Nd:YAG laser is most suited for coagulation of even inhomogeneous tissue. We determined the optimal laser parameters for therapy of urinary bladder tumors. Deep homogeneous necroses can be obtained without perforation risk of the bladder wall, and the procedure does not cause dangerous damage to the intestinal loops. We have studied animal experiments by close examination and systematic inquiry, and thus we were able to determine sufficient laser parameters in dependence on tissue thickness. Clinical studies verified these results for living human tissue. After some years of clinical use of the Nd:YAG laser we can make the first statistical statements.

Fiber Optic Technology↗

Controlled bipolar high-frequency coagulation for transurethral application: a new method for the destruction of urinary bladder tumors.

The coagulation of small bladder papillomas or of the resection base after transurethral resection by unipolar high-frequency current has turned out not to be sufficiently radical so far. There is no definite and reproducible correlation between the achieved biological effect. Bipolar high-frequency current produces the desired necrosis in the deeper layers of tissue. When providing the high-frequency generator with a new experimental automatic control equipment, reproducible deep and homogeneous necrosis of the tissue can be achieved without taking a great deal of time. Moreover, adherence of the probe and carbonization are prevented. First, the experiments had been carried out in vitro on livers of cattle and secondly, in vivo on canine livers. By the conventional unipolar high-frequency coagulation a reproducible and homogeneous necrosis cannot be achieved. With the regulated high-frequency coagulation, however, we are able to produce homogeneous tissue necroses up to a depth of 7 mm, the extension of which can definitely be assigned to the adjusted technical parameters. The electrodes do not adhere, since carbonization does not occur because of the automatic control. Premature interruption of the coagulation process, even if the generator is adjusted too high by mistake, can be considered a further advantage of this protective switch. A first clinical experience is reported.

Adult↗

Various effects of the CO2-, the neodymium-YAG-, and the argon-laser irradiation on bladder tissue.

Application of lasers as cutting or coagulation instruments is based on the conversion of light energy into heat in the irradiated tissue. The extent and degree of the thermal action depends on the beam geometry and the energy of the incident light, as well as on the optic and thermal properties of this tissue. The extinction behavior in the tissue differs for the various laser systems employed in medicine. A comparison of the effects on bladder tissue of rats and rabbits is made with Neodymium-YAG laser and the argon and CO2 lasers to demonstrate the advantages of the Neodymium-YAG laser, especially for the therapeutic irradiation of bladder tumors.

Animals↗

[Dosimetry of the neodymium-YAG laser endovesical irradiation of bladder tumors. Animal experiments (author's transl)].

Therapy of urinary bladder tumors with the aid of the Neodymium-YAG-laser is improved by two following demands. A homogeneous, deep necrosis must be obtained for the tumor cells to be devitalised completely, and neighbouring organs must be protected adequately. Both depth and shape of the necrosis were determined on liver tissue at different conditions, e.g. laser application with air, water and various time/power ratios. Measurements of temperature profiles at the bladder back wall reveal that the parameters necessary for sufficient transmural destruction of bladder tumors do not affect neighbouring organs. In clinical application it is not necessary to control temperatures occurring at the bladder wall during irradiation by means of temperature probes. It is sufficient to adjust the dosis of laser on the basis of superficial, visual discoloration. Carbonisation should be avoided by all means. Comparable effects were obtained by clinical application of data obtained during animal experimentation.

Animals↗

[Lymphatic metastasis in prostatic carcinoma. Diagnostic value of staging and transcutaneous needle biopsy].

Methods of diagnosis in metastatic disease of patients with prostatic cancer are reported. There is a high rate of inaccuracy in lymphography. In 23 patients the technique of transperitoneal fine needle aspiration biopsy of retroperitoneal lymph nodes after lymphography was used. In 8 patients malignant cells were found while lymphography showed metastases only in 4 cases. In these 8 cases a staging-operation was not indicated.

Adenocarcinoma↗

[Improvement in transcutaneous needle biopsy technics].

Transcutaneous fine needle biopsy of retroperitoneal lymph nodes after lymphography minor is connected with only discomfort for the patient. It is used for clarification of a possible infestation of metastases by malignant growth, the lymphatic drainage of which is situated retroperitoneally. A new instrument for puncture is presented, the use of which permits increase in accuracy of impact and reduction of radiation exposure for both patient and examiner. These advantages are of great importance, especially in serial puncture of several lymph nodes along the lymphogenous pathway of metastases. The quality of the fluoroscopic picture is even improved by the instrument for puncture.

Biopsy, Needle↗