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Biomedical subjects

R Guthoff

Publications and source records attributed to R Guthoff.

At least 91 records · Page 5Linked to original sources

Possible effects of radiobiological parameters on metastatic spread of uveal melanomas treated with 106Ru plaques.

We reviewed 184 cases of uveal melanoma treated with 106Ru eye plaques. The influences of the dose rate, the total dose and the initial tumour size on the incidence of metastases were of major interest in this retrospective analysis. It is widely accepted that the risk of metastatic spread increases with increasing tumour volume. However, for tumours measuring < 10 mm in basal diameter the dose rate in brachytherapy with 106Ru eye plaques might be important, since we observed a better prognosis for patients treated with plaques of relatively low activity.

Adult↗

Radiotherapy of the R1H-tumor: dose-rate effect on tumor response in brachytherapy with 106-ruthenium eye applicators.

PURPOSE: The influence of the dose-rate on tumor response in radiotherapy with 106-Ruthenium eye plaques has been investigated in an experimental tumor system. MATERIALS AND METHODS: The identical total dose was applied within three different overall treatment times (42 hr, 192 hr and 312 hr), corresponding to dose-rates of 6.0 Gy/hr, 1.3 Gy/hr and 0.8 Gy/hr. RESULTS: The therapeutic outcome of brachytherapy varied significantly between the three groups of animals treated with different dose-rates. At a dose-rate of 1.3 Gy/hr all tumors were locally controlled, but no local control was observed when a dose-rate of 6.0 Gy/hr was delivered. 0.8 Gy/hr was less effective than 1.3 Gy/hr but more effective than 6.0 Gy/hr. CONCLUSION: These results were unexpected but they might be explained by an incomplete reoxygenation if the overall treatment time is too short (42 hr, dose-rate 6.0 Gy/hr) and by proliferation of tumor cells under treatment if the overall treatment time is too long (312 hr, 0.8 Gy/hr).

Animals↗

Rates of local control, metastasis, and overall survival in patients with posterior uveal melanomas treated with ruthenium-106 plaques.

The prognostic importance of clinically assessed tumor variables, patient variables, and treatment variables of 184 patients treated with ruthenium-106 eye plaques for uveal melanoma was studied using crude survival, metastatic disease and local tumor control as the endpoints. Using the multivariate Cox proportional hazards model, tumor diameter, age and sex were identified as the strongest variables predicting survival. Risk of metastasis was found to be dependent on tumor size (diameter) only and the metastasis was generally observed within 6 years after the end of treatment (96%). Clinically diagnosed local tumor control was predicted by tumor T-stage, treatment time, and total dose to the sclera. No correlation between metastatic disease and local failure was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

[Resorbable implant materials in retinal detachment surgery. Initial animal experiment studies].

In detachment surgery after a mechanically stabile chorioretinal scar is at present full scleral indentation no longer mandatory. Following these considerations absorbable scleral implants have been developed and tested in an animal model. Cylindrical pieces of absorbable composite-material with a diameter of 5 mm were sutured as radial scleral explants in 18 rabbits. The composite material consisted of a polyglactin-polydioxanon ratio 7:1. The absorption time for polyglactin is 60 days, for polydioxanon 180 days. The explants produced initially in ultrasonographically measured buckle height between 3.2 and 4.0 mm. The clinical and ultrasonographical follow up study demonstrated a continuous decrease of buckle height. Two weeks after implantation there was a medium height of 2.0 mm after five weeks a medium elevation of 0.5 mm was found. Histopathological examinations showed incidence of a slight resorptive inflammation in the area of the buckle which was not evident after 12 weeks. No scleral infiltration or scleral thinning was found. The promising results have justified controlled clinical trials with the absorbable material which might allow to combine the advantages of silicone sponge explants (precise localization) with those of scleral buckles by inflatible balloons (reversibility).

Absorption↗

Neurofibromatosis 2 in the pediatric age group.

Bilateral acoustic neurofibromatosis or neurofibromatosis 2 (NF2) is an autosomal dominant disease predisposing to the formation of multiple tumors in the central and peripheral nervous system. Vestibular schwannomas (VSs) are considered to be the hallmark of the disease, but other tumors and ocular findings occur as well. In patients that do not carry the NF2 mutation, VSs usually occur in the fifth or sixth decade of life. VSs in patients with NF2 are often bilateral and become symptomatic in the third or fourth decade of life. In order to define the early manifestations of NF2, we examined nine children who either had one parent with NF2 or had multiple skin or spinal tumors suggestive of NF2. In addition to neurological, dermatological, and ocular examinations, all patients were studied by gadolinium-enhanced magnetic resonance imaging of the brain and spine. None of the children exhibited symptoms or signs due to VSs. However, VSs were detected during the neuroradiological work-up in six children. Seven children developed symptoms or signs due to skin or spinal tumors. Slit lamp examination detected cataracts in four patients as young as 10 years of age. The diagnosis of NF2 in the pediatric age group requires a high degree of suspicion and should be considered in children with multiple central nervous system or skin tumors without cafe-au-lait spots or Lisch nodules. Because VSs are unlikely to produce the signs seen at the time of admission, careful examination of the skin and eyes is necessary and should be followed by gadolinium-enhanced magnetic resonance imaging of the brain and spine. First-degree relatives need to be examined as well.

Adolescent↗

[Ophthalmologic differentiation of various forms of neurofibromatosis].

Neurofibromatosis (NF) is one of the most frequent autosomal-dominant hereditary disorders. The molecular-genetic differentiation of NF 1 and NF 2 has important implications for the ophthalmologist. Among 80 patients with NF 1, Lisch nodules were diagnosed in 83% as typical criteria for the disease. In 6 patients who did not meet the NIH criteria for NF 1 and NF 2, the ophthalmological investigation showed no cataracts or Lisch nodules; thus, the ophthalmological examination can help to confirm a subtype of NF. In 8 out of 22 NF 2 patients a juvenile posterior subcapsular cataract was diagnosed. Our examination demonstrates that the diagnostic value of lens opacities in NF 2 patients--especially for early detection of the disease--must be clarified, especially with regard to the fact that there were no patients with incipient cataract and no neuroradiological criteria for the disease.

Adolescent↗

[Meningioma of the optic nerve sheath. Diagnostic problems despite use of modern imaging procedures].

In spite of modern optical examination techniques such as sonography, nuclear magnetic resonance tomography (NMR) and x-ray computer tomography up to now the meningioma of the optic nerve sheath still poses a problem in respect of differential diagnosis. This problem is illustrated by two case reports. In both patients a meningioma of the optic nerve sheath could be diagnosed only after various attempts using all the imaging techniques mentioned above. NMR in combination with Gadolinium injection gave most important information.

Cranial Nerve Neoplasms↗

[Choroid melanoma. A retrospective randomized comparative study of ruthenium irradiation vs enucleation].

A randomized retrospective study concerning survival of Ruthenium treatment and enucleation in melanoma patients has been performed. For 112 patients from Hamburg who underwent Ruthenium therapy individual match partners were selected in Copenhagen where during the same period of time enucleation was the standard procedure. Selection took place concerning patient's age and sex at the time of treatment, initial tumor volume and the time of treatment. The present status of the patients was not known during the selection process. During the observation time of 12 years there was a survival rate after irradiation of 77.9% and after enucleation of 78.6%. Cox' regression disclosed a coefficient of 0.049 with a standard aviation of 0.293 and a P-value of 0.867. All parameters were showing no statistical difference between Ruthenium treated and enucleated patients. The survival rate in males was 69.2%, female patients 87.2%. For male patients there was a 2,4-fold higher risk to develop metastasis compared with female patients. Patient's age at the time of treatment correlated significantly with the prognosis. There was an increase in mortality risk by factor 1.4 per decade.

Aged↗

[Orbital teratoma--microsurgical therapy possibilities].

Microsurgical removal of a large congenital orbital teratoma is reported with successful preservation of visual function. The importance of interdisciplinary work-up including neuroradiology, ophthalmology, maxillo-facial surgery and histopathology is demonstrated. During the postoperative period closed follow-up to control refraction and to treat amblyopia is mandatory to gain optimal results.

Biopsy↗

[Endogenous candida endophthalmitis in a drug dependent patient: intravenous therapy with liposome encapsulated amphotericin B].

We report this exemplary case of a drug addict with candida endophthalmitis where we used the new form of amphotericin B, encapsulated in liposomes. We were able to reconfirm the reduced number of side effects and the minimized nephrotoxicity reported by authors of other specialties. In our patient, a reduction or elimination of the yeast was probably achieved, nevertheless, he developed a traction retinal detachment. In future cases of fungal endophthalmitis, we recommend liposomal amphotericin B in higher doses.

Adult↗

Diagnosis and treatment control of choroidal melanomas--the role of B-scan and Doppler-technique.

B-scan guided pulsed Doppler ultrasonography was applied in 62 patients with unilateral malignant melanoma. Prior to radiotherapy Doppler frequency shifts were detected in all but one neoplasm. The average systolic tumour blood flow velocity was recorded as 18.8 +/- 7.6 cm/s. Frequency shifts after radiotherapy are described. Probably the methods will find a place in the evaluation of indeterminate fundus lesions and in the follow-up of irradiated ocular melanomas.

Blood Flow Velocity↗

[Endothelial cell protective effect of high viscosity substances in cataract surgery].

An experimental setting is presented to evaluate the endothelial protection offered by various viscoelastic materials applied in cataract surgery. The substances used were: hydroxypropylmethylcellulosis, a hyaluronic acid preparation (molecular weight 5.10(6), concentration 10 mg/ml), a hyaluronic acid preparation (molecular weight 800 000, concentration: 35 mg/ml), and balanced salt solution as control. The endothelial surface of pig corneas were covered by test substances and spread with a loop of prolene 4.0 suture material in a mechanically standard way. A total of 40 corneas were examined and the amount of endothelial damage evaluated by photometry using Janus-green wash-out, a substance, which selectively binds to damaged endothelial cells or descement membrane. The damaged surfaces differed significantly in all groups of viscoelastic substances and in the control group. Examination showed that the least damage was in group 3, followed by group 1 and the most damage in group 2. Endothelial protection during cataract surgery can be improved by modifications of the substances presently applied.

Animals↗

[Comparative studies of the use of viscoelastic substances in cataract surgery. A randomized study].

In three prospectively randomized groups of patients viscoelastic materials during IOL-implantation have been compared concerning 1. intraocular pressure, 2. endothelial cell count, 3. corneal thickness. Examinations were performed preoperatively, the first, second and fifth postoperative day. There was no statistical difference between hydroxypropylmethylcellulose (2%), hyaluronic acid (1%) and air. Examinations were performed preoperatively the first, the second and the fifth postoperative day. There was no statistically significant difference between all groups of patients, Advantages and disadvantages for routine use of viscoelastic substances are discussed.

Corneal Stroma↗

[Osteoma of the bulbus pole. Manifestations in relation to site and extent].

The authors followed the clinical course of two patients with osteoma of the posterior pole for a period of two years. A 60 year old male patient whose bone formation was confined to the episclera remained asymptomatic during the follow-up period. In contrast, the visual acuity of a 9 year old female patient with an osteoma of the choroid fell from 1.0 (20/20, 6/6) initially to 0.2 (20/100, 6/30) during the same two year follow-up interval. After reviewing the literature, the authors consider the pathophysiological prerequisites for ocular bone formation and discuss the differential diagnostic possibilities.

Child↗

[Effect of dose rate of ruthenium 106 plaques on tumor regression in the animal model].

The influence of the dose-rate of 106Ru-plaques on tumor response was investigated in an experimental tumor-host system (rhabdomyosarcome R1H of the rat). A highly significant difference in tumor response was observed between tumors treated with the identical total dose (25 Gy) but varying dose rates (1.3 Gy/h vs 6.0 Gy/h). All tumors treated with the low-dose irradiation were locally controlled, whereas only one local tumor was controlled by higher dose irradiation. These unexpected results may be explained by the short overall treatment time with high dose rates, which does not allow sufficient reoxygenation of hypoxic tumor cells. In addition to the total dose, the dose rate should be included in treatment planning for choroidal melanoma brachytherapy, and analysis of the clinical data on this topic seems to be necessary in order to develop new therapy concepts.

Animals↗

[Color-coded Doppler sonography of orbital blood vessels with special reference to the central retinal artery and vein].

When certain conditions are met, parameters correlating with orbital and retinal perfusion can be investigated non-invasively with the use of Doppler ultrasonography. Color coding allows more rapid vessel localization and more precise definition of sample volume localization. Flow direction and blood velocity in the central retinal artery and vein, as well as in the ophthalmic artery, were evaluated under normal and pathological conditions using current B-scan Doppler instruments with color coding. Fourteen patients with central artery occlusion, 9 with central vein occlusion, and 9 with orbital arteriovenous fistulas were compared with a control group. In the patients with retinal venous prethrombosis and thrombosis, the blood velocities were not significantly decreased. Patients with retinal arterial occlusion had contradictory findings, presumably since recanalization had already taken place. Echographic flow imaging might be most useful when, particularly after treatment, flow velocity patterns in the orbital vessels are evaluated, and when angiographic procedures can be avoided. Illustrative cases such as spontaneous dura-cavernous sinus fistulas versus cavernous sinus thrombosis show that difficult diagnostic decisions can be made easier.

Adult↗

[Possibilities of magnetic resonance imaging of lesions in demyelinating diseases of the orbital optic nerve].

By employing the so-called inversion recovery technique, one has a nuclear magnetic resonance method at hand that allow discrete imaging of lesion in the intraorbital portion of the optic nerve in patients with optic neuritis. In our series, signal rich areas were visible in affected optic nerves in 15 of 18 patients. The areas of increased signal intensity involved the middle or the proximal third of the nerve and were still demonstrable following recovery of visual function. On the other hand, inversion recovery studies of the affected optic nerves following long inflammation free periods after an attack were within normal limits. Inflammatory edema or alterations in glial tissue may be considered as the causes of the increased signals.

Adult↗

Forces on intraocular lens haptics induced by capsular fibrosis. An experimental study.

Electronic dynamometry measurements, performed upon intraocular lens (IOL) haptics of prototype one-piece three-loop silicone lenses, accurately defined the relationships between elastic force and haptic displacement. Lens implantations in the capsular bag of dogs (loop span equal to capsular bag diameter, loops underformed immediately after the operation) were evaluated macrophotographically 5-8 months postoperatively. The highly constant elastic property of silicon rubber permitted quantitative correlation of subsequent in vivo haptic displacement with the resultant force vectors responsible for tissue contraction. The lens optics were well centered in 17 (85%) and slightly offcenter in 3 (15%) of 20 implanted eyes. Of the 60 supporting loops, 28 could be visualized sufficiently well to permit reliable haptic measurement. Of these 28, 20 (71%) were clearly displaced, ranging from 0.45 mm away from to 1.4 mm towards the lens' optic center. These extremes represented resultant vector forces of 0.20 and 1.23 mN respectively. Quantitative vector analysis permits better understanding of IOL-capsular interactions.

Animals↗