Biomedical subjects

G Hüttmann

Publications and source records attributed to G Hüttmann.

14 recordsLinked to original sources

PubMed2006

Real-time imaging of transscleral diode laser cyclophotocoagulation by optical coherence tomography.

PURPOSE: To present optical coherence tomography (OCT) for real-time imaging of cyclophotocoagulation effects. METHODS: In a pilot study, real-time transscleral OCT images were generated during diode laser cyclophotocoagulation in four eyes of four patients suffering from uncontrolled glaucoma using a specially designed contact applicator containing the OCT fiber, a focussing fiber optic and the fiber of the diode laser. RESULTS: When the contact system was used, two layers could be differentiated: a superficial thick hyperreflective complex representing conjunctiva, Tenon's capsule, episclera and sclera, and a thinner hyporeflective layer representing the ciliary body. During cyclophotocoagulation, real-time OCT showed a clear and sudden thickening of the ciliary body in the treated area. CONCLUSION: This new OCT device represents a first step towards visual, real-time imaging of cyclophotocoagulation. After further adaptation of the delivery system, further trials are needed to correlate OCT findings with aqueous production and intraocular pressure.

Ciliary Body↗

PubMed2006

Auto fluorescence of intervertebral disc tissue: a new diagnostic tool.

The paper reports on auto fluorescence phenomena of inter-vertebral human discs. It systematically investigates the auto fluorescence effects of ex vivo disc specimen and reports on surgical cases to demonstrate the potential value of the new method. The paper offers biologic explanations of the phenomenon and discusses the potential value of the UV auto fluorescence technique as a diagnostic tool. Intra- and postoperative observations are made by a surgical microscope with an integrated UV light source. Quantitative measurements were carried out using a photon counter and a spectrometer ex vivo. The auto fluorescence phenomenon allows the differentiation of traumatized and degenerated disc tissue intraoperatively in some cases, it allows the differentiation of bony and collagen endplate in cervical disc surgery. The source of the auto fluorescent light emission are amino acids of the collagen molecules. The proteoglycan components and the liquid components of the disc do not show relevant auto fluorescence. Emission wavelength of disc material is equivalent to color perception. It differs due to different collagen composition of the intervertebral disc components from yellow-green to blue-green and can be visualized in situ by naked eye.UV-auto fluorescence of inter-vertebral discs is a new clinical tool that has the potential to differentiate disc material from the anatomical surrounding, to distinguish between different fractions of the disc and to give information on the quality and status of the disc material. Since the technology has just emerged, it needs further investigations to quantify the clinical observations reported in this paper.

Amino Acids↗

PubMed2006

Time-domain and spectral-domain optical coherence tomography in the analysis of brain tumor tissue.

INTRODUCTION: Detection of residual tumor during resection of glial brain tumors remains a challenge because of a low inherent contrast of adjacent edematous brain, the surrounding infiltration zone, and the solid tumor. Therefore, new technologies that may facilitate an intraoperative analysis of the tissue at the resection edge are of great interest to neurosurgeons. MATERIALS AND METHODS: For ex vivo imaging of gliomas in a mouse model and human biopsy specimens of brain tumors and nervous system tissue we have used a time-domain Sirius 713 Tomograph with a central wavelength of 1,310 nm and a coherence length of 15 microm equipped with a mono mode fiber and a modified optical coherence tomography (OCT) adapter containing a lens system for imaging at a working distance of 2.5 cm. A spectral-domain tomograph using 840 nm and 930 nm superluminescence diodes (SLD) with a central wavelength of 900 nm was used as a second imaging modelity. RESULTS: Both time-domain and spectral-domain coherence tomography delineated normal brain, the infiltration zone and solid tumor in murine intracerebral gliomas. Histological evaluation of H&E sections parallel to the optical plain demonstrated that tumor areas of less than a millimeter could be detected and that not only solid tumor, but also brain invaded by a low-density single tumor cells produced an OCT signal different from normal brain. Spectral-domain OCT (SD-OCT) demonstrated a significantly more detailed microstructure of tumor and normal brain up to a tissue depth of 1.5-2.0 mm, whereas the interpretation of time-domain OCT (TD-OCT) was difficult at a tissue depth >1.0 mm. Because of rapid scanning times SD-OCT data could be acquired as 3D data maps, which allowed a multi-planar analysis of the tumor to brain interface. Similar to our findings in experimental gliomas, images of human nervous system tissue acquired using SD-OCT showed a characteristic signal of normal brain tissue and a detailed microstructure of tumor parenchyma. CONCLUSION: Spectral-domain OCT of experimental gliomas and human brain tumor specimens differentiates solid tumor, diffusely invaded brain tissue, and adjacent normal brain based on microstructure and B-scan signal characteristics. In conjunction with the rapid image acquisition rates of SD-OCT, this technology carries the potential of a novel intraoperative imaging tool for the detection of residual tumor and guidance of neurosurgical tumor resections.

Animals↗

PubMed2006

[Fluorescence diagnosis and photodynamic therapy with 5-aminolevulinic acid induced protoporphyrin IX in gynecology: an overview].

Fluorescence diagnosis and photodynamic therapy with 5-aminolevulinic acid induced protoporphyrin IX are promising new options in the diagnosis and therapy of diseases in a wide spectrum of medical disciplines such as urology, dermatology, gastroenterology, surgery, neurosurgery and gynecology. The techniques are based on the application of the heme biomolecule precursor 5-aminolevulinic acid which induces the endogenous accumulation of the photosensitizer protoporphyrin IX in designated tissues. After external excitation with blue light a strong red fluorescence can be initiated particularly in tumorous tissues. In gynecology many studies have been performed evaluating the usefulness of fluorescence based detection of cervical dysplasias, breast cancer, endometrial diseases, ovarian cancer and endometriosis. This work aims on the principles of fluorescence detection as an important tool in biomedical optical imaging and its current status in gynecology.

Aminolevulinic Acid↗

PubMed2006

Optical coherence tomography for experimental neuroendoscopy.

Optical coherence tomography (OCT) is a non-invasive and non-contact imaging technology that has been applied to several biomedical applications. We have recently demonstrated that OCT allows discrimination of tumor adjacent brain, diffuse and solid tumor tissue and that this technology may be used to detect residual tumor within the resection cavity during resection of intrinsic brain tumors. Here we show that an OCT integrated endoscope can image the endoventricular anatomy and other endoscopically accessible structures in a human brain specimen. A Sirius 713 optical coherence tomography device was mounted to a modified rigid endoscope. A formalin-fixed human brain specimen was used to simulate endoscopic visualization of brain anatomy and two specimens of fixed malignant tumors with endoventricular growth patterns. Simultaneous OCT imaging and endoscopic video imaging of the visible spectrum was possible using a graded index rod endoscope. OCT imaging of a human brain specimen in water allowed an in-depth view into structures like the walls of the ventricular system, the choroid plexus or the thalamostriatal vein. OCT further allowed imaging of structures beyond tissue barriers or opaque media. In this fixed specimen OCT allowed discrimination of vascular structures down to a diameter of 50 mum. In vessels larger that 100 mum the lumen could be discriminated and within larger blood vessels a layered structure of the vascular wall as well as endovascular plaques could be visualized. This in vitro pilot study has demonstrated that OCT integrated into neuroendoscopes may add information that cannot be obtained by the video imaging alone. This technology may provide an extra margin of safety by providing cross-sectional images of tissue barriers within optically opaque conditions.

Brain↗

PubMed2000

Origin of retinal pigment epithelium cell damage by pulsed laser irradiance in the nanosecond to microsecond time regimen.

BACKGROUND AND OBJECTIVE: Selective photodamage of the retinal pigment epithelium (RPE) is a new technique to treat a variety of retinal diseases without causing adverse effects to surrounding tissues such as the neural retina including the photoreceptors and the choroid. In this study, the mechanism of cell damage after laser irradiation was investigated. STUDY DESIGN/MATERIALS AND METHODS: Single porcine RPE-melanosomes and RPE cells were irradiated with a Nd:YLF laser (wavelength lambda = 527 nm, adjustable pulse duration tau = 250 nsec-3 microsec) and a Nd:YAG laser (lambda = 532 nm, tau = 8 nsec). Fast flash photography was applied to observe vaporization at melanosomes in suspension. A fluorescence viability assay was used to probe the cells vitality. RESULTS: The threshold radiant exposures for vaporization around individual melanosomes and for ED50 cell damage are similar at 8-nsec pulse duration. Both thresholds increase with pulse duration; however, the ED50 cell damage radiant exposure is 40% lower at 3 microsec. Temperature calculations to model the onset of vaporization around the melanosomes are in good agreement with the experimental results when assuming a surface temperature of 150 degrees C to initiate vaporization and a homogeneous melanosome absorption coefficient of 8,000 cm(-1). Increasing the number of pulses delivered to RPE cells at a repetition rate of 500 Hz, the ED50 value decreases for all pulse durations. However, the behavior does not obey scaling laws such as the N 1/4 equation. CONCLUSION: The origin of RPE cell damage for single pulse irradiation up to pulse durations of 3 microsec can be described by a damage mechanism in which microbubbles around the melanosomes cause a rupture of the cell structure. The threshold radiant exposure for RPE damage decreases with increasing number of pulses applied.

Animals↗

PubMed2000

Experimental photodynamic laser therapy for rheumatoid arthritis with a second generation photosensitizer.

Photodynamic laser therapy has been shown to be a new method for the treatment of synovitis in various animal models. Its principle is the accumulation of a photosensitizing drug in the inflamed synovium which is destroyed by photoactivation of the drug. In the present animal study we demonstrate the effect of a second-generation photosensitizer and suggest a concept for light dosimetry within the joint. We used 38 inbred rabbits for the IgG-induced arthritis model; 2 mg/kg of the benzoporphyrin derivative monoacid ring-A (BPD-MA) Verteporfin were administered 3 h before irradiation, which was performed using a 690-nm diode laser coupled to quartz glass fiber with a cylinder diffusor tip at a total light energy of either 180 or 470 J. During irradiation specific fluorescence of BPD-MA was monitored using a spectroscopy unit. The effect of the photodynamic laser therapy was documented grossly and histologically after 1 week. Within the 470 J-group a complete necrosis of the inflamed synovium was observed. The bradytrophic structures of the joint, however, remained unchanged. Throughout the 180 J-group the extent of necrosis was minor. During irradiation the tissue fluorescence of BPD-MA showed a dose-dependent decrease. Using BPD-MA as a photosensitizer a highly selective and minimal invasive synoviorthesis can be performed. At a dose of 2 mg/kg the histological effect depends on the light dose. For optimum efficacy a total energy of 470 J seems favorable. Online fluorescence detection can be used to monitor the effect of light administration. For dosimetry therefore an online tissue fluorescence detection may represent a technical solution.

Animals↗

PubMed1997

Photodynamic laser therapy for rheumatoid arthritis. Cell culture studies and animal experiments.

The introduction of arthroscopic techniques has improved the surgical therapy of rheumatoid arthritis. The additional application of the holmium:yttrium aluminum garnet (Ho:YAG) laser likewise holds great promise by providing complete hemorrhagic control. Unfortunately, a minimally invasive solution for use in smaller joints has not yet emerged. The present study describes the possible treatment of these joints by means of photodynamic laser therapy. Cell culture studies with human synovial fibroblasts obtained from patients with rheumatoid arthritis have demonstrated a cytotoxic effect after administration of Photosan-3 as a photosensitizer and subsequent laser irradiation at 630 nm. for the in vivo studies, IgG-induced arthritis in rabbits, which is histologically consistent with the proliferative phase of rheumatoid arthritis, was used as the animal model. The histologic picture following photodynamic laser therapy with Photosan-3 revealed complete synovial destruction which also extended to the border of the subjacent joint capsule. In contrast, bradytrophic structures, e.g. cartilage. menisci, and ligaments, remained unchanged at both the macroscopic and microscopic levels. Therefore, photodynamic laser therapy can be considered a new method in the surgical treatment of inflammatory disease of the synovial membrane. It has the advantage of being minimally invasive, while offering a high degree of efficacy and selectivity.

Animals↗

PubMed1996

Chemical instability of 5-aminolevulinic acid used in the fluorescence diagnosis of bladder tumours.

Aqueous solutions of 5-aminolevulinic acid (ALA) prepared for intravesical instillation in the framework of a clinical study on the fluorescence diagnosis of urothelial bladder cancer were found to be unstable. This chemical instability of ALA was studied in aqueous solution of 37 degrees C as a function of concentration, pH and reaction time. Our investigations showed that the reaction of ALA is an irreversible process, which yields at least two reaction products in the pH range studied (pH lower than 8): the 2,5-(beta-carboxyethyl)dihydropyrazine and the 2,5-(beta-carboxyethyl)pyrazine. As a result of these studies, the conditions for the preparation of ALA solutions to be used for intravesical instillation were optimized: solution of ALA in phosphate-buffered saline at a concentration of 0.18 M (3 g of ALA in 100 ml) neutralized to pH 5, were prepared and stored on ice until use. Solutions prepared under these conditions were stable and were used for fluorescence diagnosis of bladder tumours with successful results. The effect of the pH and the composition of the urine on the extent of the reaction of ALA and on the nature of its reaction products formed during instillation was investigated by comparing the urine of patients before and immediately after instillation of ALA.

Aminolevulinic Acid↗

PubMed1996

[Experimental bases for photodynamic laser therapy in chronic polyarthritis].

The principle of photodynamic laser therapy (PDT) for chronic polyarthritis consists in specifically concentrating a drug (photosensitizer) in the synovium. Subsequent activation of the photosensitizer by means of laser leads to a cytotoxic effect. The practicability of PDT was first shown in cell cultures of human synovial fibroblasts. For further tests an animal model consisting of IgG-induced arthritis in rabbits was used. In this model, concentration of the photosensitizer in the synovial lining cells, in the media of arteries and in the lymphoid infiltrate was seen. After laser irradiation there was total selective demarcation of the synovium. In contrast, bradytrophic tissues such as cartilage, meniscus and ligament structures were changed neither macroscopically nor microscopically. In the animal model PDT combines high selectivity with minimal invasiveness and can be used in small joints. PDT thus offers ideal preconditions for future minimal invasive treatment of chronic inflammatory joint diseases.

Animals↗

PubMed1994

[Photodynamic therapy of eyelid basalioma after topical administration of delta-aminolevulinic acid].

Delta-aminolevulinic acid (ALA) induced Protoporphyring IX photodynamic therapy (PDT) is a new method in the therapy of cutaneous malignancies. Topical application prevents photosensibilization of normal skin. Promising results in the treatment of superficial basal cell carcinomas have been reported. To evaluate the efficiency of this method in the therapy of basal cell carcinomas of the lid, 10 patients were treated by PDT 5 h after application of ALA. The lesions were irradiated by an argon-ion-laser-pumped dye laser at a wavelength of 630 or 635 nm and at cumulative radiant exposures of 50 and 100 J/cm2. After 5-8 weeks follow-up, the basal cell carcinomas were excised to assess histologic changes. In the first few days after PDT the lesions seemed clinically to regress, due to erythematous swelling, but after a few weeks all tumours showed the same configuration they had before irradiation. Histological examination revealed small areas of necrotic cells in all irradiated basal cell carcinomas, surrounded by residual tumour formations. The reason for the poor results may be limited penetration of ALA or light. Although ALA-induced Protoporphyrin-IX PDT is a promising approach in the therapy of dermal lesions, it is not yet an acceptable alternative method in the treatment of basal cell carcinomas of the lid.

Administration, Topical↗

PubMed1989

[Caries and gingivitis prevention in handicapped children and youth. Part 3. Five-year results].

In schools for handicapped children in Göttingen 104 mentally and physically handicapped and 150 learning disabled pupils participated in an intensive care preventive program. Their teeth were examined before beginning the prevention, after 6 months, and subsequently at annual intervals. The examinations consisted of caries diagnosis and assessment of periodontal health. Five years after the onset of the prevention program the incidence of caries in the various age groups and institutions was 23% to 64% lower than 1982. Results were best in mentally and physically handicapped children aged 9 to 11 years (mean DMF-S 1987: 2.4 versus 1982: 6.6). In the same period of observation the degree of oral health in mentally and physically handicapped children improved from 43% to 73%, in learning disabled from 32% to 63%. Mean SBI values were reduced by 60%.

Adolescent↗

PubMed1989

[A selective, need-oriented prevention program for primary schoolchildren - results after two years].

427 first grade pupils from primary schools in Göttingen participated in a selective, need-oriented preventive program. Following a clinical examination and an additional saliva test the children were assigned to three risk groups, according to the severity of the initial findings. Each group received preventive care of varying intensity. Two years later the children of risk group 1 ("minor caries risk") showed a mean 0.5 and those of risk group 2 ("medium caries risk") a mean 1.0 new DF surfaces. In the children of the high caries risk group the average caries increment was 1.8 DF surfaces. The degree of sanation of the deciduous teeth could be improved from 10% to 47% within the two years' test period. The saliva tests revealed that the number of cariogenic organisms was markedly reduced in the course of the preventive program.

Child↗

PubMed1989

[Caries incidence and oral hygiene level in young school children in Gottingen].

669 school beginners and 739 fourth-year pupils in Göttingen were examined for caries prevalence and dental hygienic measures. 28% of first-year pupils examined had naturally healthy primary teeth; the average DFS was 6.8. Only 12% of the carious primary tooth surfaces had intact fillings. Carious defects in permanent teeth were restricted to sixth-year molars. Among the fourth-year pupils 26.8% had no caries on their permanent teeth; the average DMFS was 3.9. In this age group 60% of the carious tooth surfaces had been treated and the M components observed were minimal. A total of only 16 sixth-year molars were missing because of caries in all the children examined. A comparison of prevalence rates among different schools revealed considerable differences: Average DMFS values at the various schools ranged from 2.0 to 5.5.

Child↗