A method for digital signal processing based laser-Doppler flowmetry.

Non-invasive measuring of blood perfusion of tissue is important for establishing the influence of vascular diseases on microcirculation. A signal processing method for laser-Doppler flowmetry is presented in this article. The method is based on the digital filtering. A couple of filters are suggested. One of them is a digital passband filter, second - a digital filter transforming spectrum P(f) of the input signal to fP(f) spectrum. Performance of the suggested method is investigated in comparison with behaviour of the PERIMED instrument as well as with applications based on DFT.

Spectral analysis of laser-Doppler perfusion signal measured during thermal test.

The method of spectral analysis of laser-Doppler perfusion signal measured during thermal test is proposed. During three 20 min phases with 40, 5, and 40 degrees C of thermal test laser-Doppler perfusion signal was recorded. For each signal phase frequency spectra were calculated using the FFT method. Quantitative parameter Spectral Factor for results evaluation was proposed. In total 94 patients were measured: 69 with Raynaud's phenomenon and 25 normal subjects. Additionally in 18 Raynaud's patients the influence of Nifedipine was studied. Results suggest that proposed parameter is able to differentiate between Raynaud's patients and normal subjects and that is useful for evaluation of Nifedipine effectiveness. However, further studies are needed to improve the method to differentiate between primary and secondary Raynaud's patients.

Dynamic characteristics of laser-Doppler flux in normal individuals and patients with Raynaud's phenomenon before and after treatment with nifedipine under different thermal conditions.

The study was aimed at choosing an appropriate characteristic of laser-Doppler flux (LDF) data for (1) distinguishing patients with Raynaud's disease from normal controls and (2) evaluating the effect of nifedipine under different thermal conditions. We checked the reliability of three characteristics of nonlinear dynamics as statistical dimension Ds, correlation dimension D2 and power-law index PLI. Their values depended heavily on the thermal condition. The most reliable characteristics that enabled us to distinguish the patients from normal controls and the effect of nifedipine under definite thermal condition proved to be Ds and PLI. The latter is simple for computation and is thus recommendable for clinical practice. Ds and PLI were higher in patients with Raynaud's compared to normal controls and diminished during the transitions from low to high temperature. However, the characteristics used were unable to distinguish significantly Raynaud's I from Raynaud's II patients.

Processing of laser-Doppler signals from free flaps.

As conventional graphical laser-Doppler flowmetric (LDF) registrations from free flaps are difficult to interpret we explored the use of refined computerized signal processing to enhance the reliability of the blood flow supervision postoperatively. From eleven free flaps LDF data were collected using a software programme and a personal computer for analysis. Findings were compared with the clinical outcome. Nine flaps healed whereas one had wound problems and one suffered a partial necrosis. From the nine uneventful flaps, a peak within the range of frequencies from 0.04 to 0.23 Hz was seen. In the remaining two, such a low frequency peak could hardly be observed. Frequency analysis using computerized processing of LDF signals thus has the capacity to demonstrate the status of the flap perfusion. The slow wave vasomotion component seems to be of particular importance. Other frequency components warrant further investigation. A custom made monitoring device would be of great clinical value.

Studies on an immunologically induced synovitis model in pigs and sheep.

Chronic synovitis was induced in seven sheep and nine pigs to investigate the potential applicability of laser treatment in arthroscopic synovectomy. Systemic sensitization was accomplished using chicken egg or turkey egg albumin antigens with Freund's incomplete adjuvant, enriched with killed and dried Mycobacterium tuberculosis. Ten days after the second immunizing dose, skin sensitization testing was undertaken. After a satisfactory systemic reaction had been observed, the respective antigen was injected once or twice into the left knee of each animal at 2-week intervals. After chicken egg albumin sensitization at varying systemic immunization and joint injection doses, sheep (five of five) showed neither strong morphologic nor continuous synovitis, despite a positive systemic reaction. In pigs (three of three) the inflammatory signs also were unsatisfactory for the manifestation and characterization of a synovitis model. In contrast, the application of turkey egg albumin to pigs (six of six) during the 4-month study provided a persistent, clearly manifested synovitis that developed visible villi formation and an amber to gray synovial fluid and microscopically showed follicular aggregations of lymphocytes and plasma cells. In similarly immunized sheep (two of two), only a light synovitis developed with occasional perivascular inflammatory foci.

[Laser Doppler data analysis during interstitial laser thermotherapy with magnetic resonance control within the scope of an animal experiment study]. / Laser-Doppler-Datenanalyse während interstitieller Laserthermotherapie unter Magnetresonanz-Kontrolle im Rahmen einer tierexperimentellen Studie.

The aim of the present study was to investigate, using laser Doppler (LD) flowmetry, the phases immediately prior to and following experimental, neurosurgical laser therapy in animals. Two statistical models obtained on the basis of discriminant analysis are described. These models should enable the user to classify the sets of parameters calculated from the LD signals. With both models which contain 3 and 5 parameters, respectively. 100% discrimination of the two phases was attained. The usefulness of the models could be validated by results obtained with other models.

Laser doppler flowmetry in the hyperbaric environment.

Continuous monitoring of laser Doppler (LD) flowmetry was performed in eight healthy volunteers (mean age 42.0 + 12.1 yr; range 25-62 yr) before, during and after hyperbaric oxygenation ([HBO at 2.5 and 1.95 ATA (atmosphere absolute)]).Two models of the discrimination analysis are presented which allow classification, resulting from the parameter obtained by the LD flowmetry.The results show that 100% separation of the LD data under HBO at 2.5 and 1.95 ATA including five parameters can be achieved with the first model. The second model for the analysis of four different phases with eight parameters still shows an obvious separation; however, only 75% of the group integration is correct. In addition to transcutaneous P(2) measurements, which are sometimes difficult to obtain perfectly, LD parameters will be of interest to manage HBO treatment, especially when peripheral circulation is reduced.

[Holmium laser versus mechanical cartilage resection. Comparative studies in the rabbit arthrosis model]. / Holmiumlaser versus mechanische Knorpelabtragung. Vergleichende Untersuchungen am Arthrosemodell bei Kaninchen.

The aim of this work was to investigate and evaluate the tissue reactions after sham operation and after mechanical and holmium laser chondral debridement in a rabbit model at different postoperative intervals. In 27 rabbits an arthrosis was induced by implantation of a piece of polyethylene sheeting in one knee joint. After 5 months, distinct arthritic changes had developed. Nine animals each were randomized for sham operation, mechanical debridement, and holmium laser chondral debridement. At 1 day, 1 month, and 3 months postoperatively, three animals in each group were sacrificed and their joints examined grossly and microscopically. At 3 months after mechanical debridement the articular surface was relatively smooth, and tears and defects were filled with fibrous repair tissue. After holmium laser debridement chondral necroses were regularly found, occasionally with damage to the subchondral bone and distinct inflammation in the marrow space. The articular surface remained rough and uneven. These preliminary results suggest that use of the holmium laser is not superior to mechanical methods for remodelling and smoothing of fairly large chondral areas.

[Comparative experimental studies of mechanical and holmium laser synovectomy]. / Vergleichende experimentelle Untersuchungen zur mechanischen und Holmiumlaser-Synovektomie.

The goal of this study was to evaluate tissue reactions in rabbit knees following laser synovectomy using a holmium:YAG laser (wavelength: 2.1 microns) and to compare these results with those found after conventional mechanical abrasion treatment. Chronic arthritis was immunologically induced in one knee joint each of 48 rabbits. Twelve served as controls, 12 were sham-operated, 12 were exposed to laser radiation, and 12 others were treated according to conventional methods. In the laser group, a pulse length of 1 ms at a repetition rate of 3 Hz resulted in a pulse energy of 600 mJ. After periods of 1 day, 1 week and 1 and 3 months, respectively, three animals from each group were sacrificed and the synovialis was examined macroscopically and histologically using light and electron microscopy. Edema, acute inflammation, and coagulation necrosis occurred immediately following laser therapy. After 1 week, the synovial layer showed slight fibrosis, which was comparable to that found in the controls. One month later the surface appeared to be smooth. The mechanical abrasion caused hemorrhage and necrosis. Fibrosis was pronounced in all capsular layers, and after 3 months the surface appeared coarse and villous in this group. Based on these preliminary findings, holmium-laser synovectomy may offer an alternative to existing therapeutic techniques in the treatment of rheumatoid arthritis. The arthroscopic approach could prevent additional capsular fibrosis associated with mechanical irritation.

Temperature controlled angioplasty (preliminary results in heritable hyperlipidemic rabbits).

The purpose of this investigation has been to demonstrate the safety of temperature controlled angioplasty (TCA) with a coaxial heating element, particularly during heat application, and to ascertain the short- and long-term arterial tissue response in 7 month old homozygous Heritable Hyperlipidemic rabbits. In 7 animals, a defined segment of the abdominal aorta was treated with TCA for 40 seconds at 175 degrees C, and 2 animals served as untreated controls. At sacrifice, 1 day, 1 and 2 weeks after TCA, in one animal each a coagulation necrosis with condensation of elastic fibers was found. One year later, 1 of 2 animals revealed irregularly structured elastic fibers combined with only minor atherosclerotic lesions. Treated segments of the second animal and of the 2 remaining animals 2 years after TCA did not appear to differ from the control segments. In conclusion, the TCA never resulted in perforation or carbonization or in adhesion of the heating element to the vascular wall, representing a safe angioplastic technique.

Endothelial denudation in HHL-rabbit aortas.

The purpose of this study has been to develop a rabbit model for the assessment and follow up of angioplastic techniques which would be comparable to human arteriosclerosis. Segments of the abdominal aortas of 10 homozygous Heritable Hyperlipidemic rabbits were treated with 2 endothelial denudation procedures and collected at sacrifice after 1 week, 1 month, 2 or 3 months. Nondenuded segments of the 3 month group were taken as native controls. All sections were stained with hematoxilin/eosin and Elastica van Gieson. Pronounced intimal thickening with fibrosis, sometimes with atheromatosis developed after 1, 2, and 3 months. After 2 months calcium deposits and after 3 months frayed inner elastic membranes were found. The control segments revealed a lesser pathogenic expression with intact inner elastic membranes. In conclusion, a substantial increase in the pathogenic expression or the development of stenoses could not be obtained by 2 endothelial denudation procedures at the age of about 5 months.

Holmium-laser synovectomy of immune synovitis in rabbits.

Holmium-laser synovectomy was carried out to remove allergically inflamed synovial membranes in rabbit knee joints. The healing process was then investigated at different periods. Left knee joints of 12 rabbits were exposed to Ho:YAG-laser radiation at a wavelength of 2.1 microns, pulse energy of 600 mJ, pulse length of 1 ms, and repetition rate of 3 Hz. Twelve others were treated conventionally and 12 served as controls. After 1 day, 1 week, and 1 and 3 months, respectively, 3 animals from each group were sacrificed and the synovialis grossly and microscopically examined. Coagulation necrosis, inflammation, and edema resulted following laser therapy. After 1 week, the synovial layer consisted of a scarlike formation of fibers and within 1 month, its surface appeared smooth. The mechanical abrasion caused hemorrhage and necrosis. Fibrosis developed in the capsular layers, and after 3 months, the surface appeared coarse and villous. Based on these preliminary findings, holmium-laser synovectomy may offer an alternative method to existing therapeutic techniques.

[Expression of induced atherosclerosis in the rabbit model]. / Ausprägung einer induzierten Atherosklerose am Kaninchenmodell.

Atherosclerosis in rabbits was induced by administering a 2% cholesterol diet and additional endothelial denudation of the aorta and iliac artery as a model for vascular surgery. In addition, the serum cholesterol-, serum triglyceride-, and HDL-cholesterol values were examined. After 22 weeks the intima and most often the media showed atheromatosis and fibrosis, in most of the arteries with intimal necroses. All arteries developed marked to pronounced stenoses, calcium deposits were only observed in single cases. The intensity of the arterial lesions was found to be similar to the appearance of human atherosclerosis.

Experimental salvage of the spleen. A combined technique of cryosurgery and tissue sealant.

The goal of this investigation has been to improve the safety of intra- and post-operative haemostasis in splenic lesions by a combined technique of tissue freezing followed by the application of collagen fleece and fibrin glue in an animal study. The progression of healing was observed after different periods of time. Grade II lesions were set on the spleens of 15 pigs. The wounds were frozen for 1 m at -60 degrees C with a cryosurgical probe and afterwards sealed with fibrin glue and collagen fleece. In every case, complete haemostasis was achieved intraoperatively. The spleens of 3 animals each were examined microscopically after 2 days, 1, 2, 5 and 6 weeks, respectively. A visceroperitoneal adhesion was observed in only 1 spleen and u-shaped viscerovisceral adhesions in 5 spleens. Superficial coagulation necroses were observed only in specimens removed after 2 days and 1 week, respectively. Complete and safe haemostasis followed by acceptable subsequent healing was achieved using this combined technique.

[Therapy of splenic injuries by freezing and fibrin gluing. Animal experiment study]. / Therapie von Milzverletzungen durch Vereisung und Fibrinklebung. Tierexperimentelle Untersuchung.

The goal of this investigation was to improve the reliability of intraoperative and postoperative hemostasis and to observe the healing process after using a combined technique of tissue freezing followed by the application of collagen fleece and fibrin glue for the treatment of splenic ruptures. Grade II lesions were inflicted on the spleens of 15 swine. The bleeding wounds were frozen for 1 min at -60 degrees C using a cryosurgical device. Immediately afterwards the frozen lesions were covered with fibrin glue and collagen fleece and kept under slight compression. In every case complete hemostasis was achieved intraoperatively. The spleens of three animals each time were collected for gross and microscopic examination after 2 days and 1, 2, 5, and 6 weeks. A visceroperitoneal adhesion was observed in only one spleen, U-shaped viscerovisceral adhesions in five spleens. Superficial coagulation necroses could be detected microscopically only after 2 days and 1 week. Organization of the wounds, indicated by granulation tissue which contained siderophages, started in the 2nd week. There was distinct formation of collagen fibers after 5 and 6 weeks; only a residue of the collagen fleece was visible and the surplus fibrin glue was encapsulated. With this combined technique complete and safe hemostasis and a good subsequent healing process was achieved.

Long-term investigations of serum cholesterol, serum triglyceride, and HDL cholesterol in heritable hyperlipidemic rabbits.

The purpose of this investigation was to follow the course of the serum cholesterol, serum triglyceride and HDL cholesterol concentrations of heritable hyperlipidemic (HHL) rabbits (34 animals in total) in order to obtain an early prediction of these parameters, which appear to be highly associated with the presence of arteriosclerotic lesions. Measurements were done at 6-week intervals for one year, beginning at the 10th week of age. At week 10 the serum cholesterol concentration of females was 652.80 mg x dl-1 +/- 103.82 (standard deviation) and that of males was 648.84 mg x dl-1 +/- 146.04. The 10-week serum triglyceride concentration of males was 267.90 mg x dl-1 +/- 93.03, which decreased in two marked steps after week 10 and 40, while that of females was 246.70 mg x dl-1 +/- 67.51, which reached a maximum at 7 months and then decreased. Both the serum cholesterol and the serum triglyceride concentrations decreased significantly in males and females during the investigation period. The 10-week HDL cholesterol concentrations (males: 18.08 mg x dl-1 +/- 12.81; females: 14.61 mg x dl-1 +/- 8.56) remained relatively constant in both sexes during the investigation period. We consider one or two samplings, usually at weaning and at the beginning of an investigation, to ensure reliable biochemical parameters for the state of the animals.