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Biomedical subjects

G Stücklschweiger

Publications and source records attributed to G Stücklschweiger.

15 recordsLinked to original sources
PubMed2004

[Dose-volume histogram regression analysis of uveal melanomas after single fraction gamma knife radiosurgery].

BACKGROUND: To evaluate tumor regression and sequelae in 30 uveal melanomas treated with Gamma Knife radiosurgery between 1992 and 1995 at the Gamma Knife center in Graz. PATIENTS: A total of 30 uveal and ciliary body melanomas were treated with a single fraction of the Gamma Knife. The mean marginal dose was 52.1 Gy, (median 50 Gy). Of the tumors, 15 were large (higher than 8 mm), 14 were medium sized (3-8 mm) and one was a small melanoma (<3 mm). Among them were 6 juxtapapillary, 10 (juxta-) maculary melanomas, 5 tumors located in the midperiphery and 9 ciliary body melanomas. METHOD: Dose-volume histogram analysis. RESULTS: After a maximum follow up of 9 years and 7 months, 8 tumors regressed into a scar, 17 tumors into a residual prominence between 50% and 80% of the initial tumor height, 3 tumors showed no change and in 2 patients recurrence was obvious. Sequelae were classified as mild (in 3 patients), moderate (3), severe (5) and very severe (19). CONCLUSIONS: Significant factors for the development of severe sequelae were the tumor volume and the marginal dose, the mean dose proved to be more important than the marginal dose and the irradiated volume more important than the selective critical dose.

Adult↗
PubMed2003

Palliative treatment of unresectable bile duct tumours.

PURPOSE: Report on outcome of intraluminal high-dose-rate iridium-192 (HDR-Ir192) brachytherapy with or without external radiotherapy in patients with unresectable bile duct tumours suffering from symptoms of malignant obstructive jaundice. MATERIAL AND METHODS: Fourteen patients (mean age: 63 years) who were unsuitable for surgical resection on preoperative evaluation/laparotomy or inoperable due to poor general condition were referred for palliative radiotherapy. After percutaneous transhepatic drainage, HDR-Ir192 brachytherapy was performed with a single dose of 2.5 Gy. Brachytherapy was given twice a day with at least a 6-h interval for 2 days, 2 or 3 days apart, up to a total dose of 10 Gy. Five patients received small-volume external radiotherapy (RT) (45 - 50.4 Gy/1.8 Gy) additionally. RESULTS: Palliation with relief of the aggravating symptoms of obstructive jaundice was achieved in all patients. The actuarial 2-year survival rate of all patients was 11.9 % with a median survival of 6.5 months. Patients treated with brachytherapy alone had a median survival of 4.5 months as compared with 6.5 months after combined internal and external irradiation (log rank, P = 0.95). CONCLUSION: Patients with advanced unresectable bile duct cancer face a dismal prognosis; however, biliary drainage, and intraluminal brachytherapy with or without external RT, seem to be able to improve quality of life in the remaining time span.

Adult↗
PubMed1997

Endocavitary Ir-192 radiation and laser treatment for palliation of obstructive rectal cancer.

Endoscopic laser therapy (ELT) either alone or combined with endocavitary Ir-192 radiation is performed for advanced, inoperable rectal cancer and when patients are ineligible for surgery due to severe concomitant medical illness. During the period from January 1984 to January 1997 we treated 81 patients (51 males, 30 females). Sixty-seven patients had ELT only using a ND-Yag Laser system. Twenty-five patients (average age: 80.5 years) were ineligible for surgery (Group I). Forty-two patients (74.1 years) had an advanced locally inoperable tumour (Group II). Fourteen patients (76.5 years) underwent a combined therapeutic regime with endocavitary Ir-192 afterloading following ELT (Group III). Adequate desobliteration was achieved in 100% (groups I and III) and 97% (group II) of the patients. The average interval to aftertreatment was 8.4 weeks in group I and 9.4 weeks in group II, compared to 11.5 weeks in group III. Serious complications (perianal abscess, rectovaginal fistula) occurred in 3.7%, minor complications (laser-induced bleedings, unclear fever) in 12.3%. All laser-induced bleedings could be dealt with using laser therapy. The frequency of treatment was governed by tumour mass and the patient's survival. The results suggest that additional endocavitary radiation significantly prolongs the maintenance of normal bowel function compared with laser therapy alone.

Aged↗
PubMed1995

[Stereotaxic convergent irradiation with the gamma knife. A study of the possibilities for optimizing the dosage distribution].

PURPOSE: On April 1992, the first stereotactic radiosurgical procedure using the gamma knife was performed at the University Medical School Graz, Department of Neurosurgery. Accurate dose optimization is the foundation of a convenient and responsible utilization of this modality. But there are limits, because the final collimation is only achieved by 1 of the 4 special helm collimators. MATERIAL AND METHODS: The possibilities of dose optimization and its influence on the dose distributions were investigated and partly compared with results of film densitometry measurements. In detail, the technique, which uses the same isocenter, but different sized collimators was studied. The influence of these optimization techniques on the resulting dose distributions and the dose gradient at the edge of the treatment planning volume was analyzed. Also the visions for an effective dose optimization are discussed. RESULTS: With 2 shots of different diameters, located at the same target coordinates and different weighting of time any collimator size between the 4 mm and 18 mm can be achieved. Because of that, a combination of more than 2 collimators is not meaningful. With the combined shots the dose fall gradient was less than that of either of the single shots involved in the combination. CONCLUSIONS: With the available physical and technical possibilities only a limited, very time consuming optimization is practicable. The quality control of isodose distributions requires optimizations in hard- and software, that enable CT- or MRT-based 3-dimensional visualization and dose volume analysis.

Brain Neoplasms↗
PubMed1993

Iridium-192 high dose rate brachytherapy combined with external beam irradiation in non-resectable oesophageal cancer.

Forty-eight patients with non-resectable cancer of the oesophagus and oesophagogastric junction (group A: Stage I/II: n = 32; group B: Stage III/IV: n = 16) underwent intralumenal iridium-192 high dose-rate afterloading brachytherapy (5-7 Gy/session, total dose 5-21 Gy, mean 12.4 Gy) and external beam irradiation (Karnofsky > or = 80%: 50-60 Gy/2 Gy per day; Karnofsky 60%-79%: 30 Gy/3 per day). Prolonged satisfactory palliation (intake of at least semi-solid food) was demonstrated in 96% of patients. The mean survival for group A was 19.1 months and that for group B 6.9 months, with a 12-month survival rate of 66% for group A and 0% for group B (P < 0.001). Local tumour response and complication rate were significantly dose related with a predicted response rate of 70.5% and a complication rate of 50% at extrapolated response dose (ERD) 129.3 GY3 (Gy at alpha/beta = 3).

Adult↗
PubMed1992

Hyperfractionated radiotherapy and polychemotherapy in brain stem tumors in children.

Between October 1989 and January 1991 five children with brain stem tumors were treated with sequential chemo- and radiotherapy. The polychemotherapy consisted of procarbazine, ifosfamide, etoposide, methotrexate, cisplatin and cytosine arabinoside. Locally, hyperfractionated radiotherapy was delivered at a total dose of 63.8 Gy (1.1 Gy twice daily, 10 fractions per week). After a median observation time of 11.8 (range 4-23) months from diagnosis three children are alive and without evidence of tumor progression. Two patients died from tumor progression 11 and 16 months respectively after initiation of therapy.

Adolescent↗
PubMed1992

Reduction of the dose to the lens in prophylactic cranial irradiation: a comparison of three different treatment techniques and two different beam qualities.

Three treatment techniques using two beam qualities have been compared on the basis of dose to the lens in prophylactic cranial irradiation. The dose to the lens and the globe was measured with thermoluminescent crystals in an anthropomorphic phantom and calculated by a computer-assisted planning system. A comparison was made of large field and small field techniques using 60Co and 8 MV photons. Modifications to the basic techniques studied included angulation of the gantry, angulation of the couch, and placement of an additional eye block close to the surface. The dose to the lens could be reduced to four percent of the midplane dose by applying the small-field technique combined with the use of 8 MV energy photons, by placing an additional block close to the surface, and by five degree occipitally angling the gantry, as well as rotating the treatment couch to account for the divergence of the beam. The use of 60Co produced an underdosage of the posterior segment of the globe in angled treatment techniques.

Cataract↗
PubMed1992

[Metallic mesh endoprosthesis and intraluminal high dose rate 192Ir brachytherapy in the palliative treatment of malignant bile duct obstruction. Initial results].

Since December 1989, 9 patients with inoperable malignant biliary tract obstruction were treated palliatively by a combined modality treatment consisting of placement of a permanent biliary endoprosthesis followed by intraluminal high dose-rate 192Ir brachytherapy. A dose of 10 Gy was delivered in a hyperfractionated schedule at the point of reference in a distance of 7.5 mm of centre of the source. External small field radiotherapy (50.4 Gy, 1.8 Gy per day, 5 fractions per week) was also given in six cases (M/O, Karnofsky greater than 60%). In 9/9 cases an unrestrained bile flow and an interruption of pruritus was achieved, in 78% (7/9) of cases the duration of palliation was as long as the survival time (median survival time 7.5 months).

Adenocarcinoma↗
PubMed1991

[Evaluation of irradiation techniques in breast carcinoma using dose-volume histograms. Comparison of the heart and lung exposure].

For irradiation of the internal mammary lymph nodes (IMN), together with irradiation of the breast the commonly used treatment techniques are of three types: 1. two tangential opposed fields, 2. three field plans with a separate "straight on" IMN-field, or 3. with a separate "angled" IMN-field. To determine lung and heart volumes and doses for these techniques, dose-volume-histograms in 30 patients were analyzed. The optimum dose distribution was achieved with the "angled" field technique and an appropriate combination of electrons and 60Co gamma radiation for the IMN-field. (The beam mixture used was 40% 60Co beam and 60% electron beam.) The least possible dose to the lung was obtained with the "straight-on" field technique and the least possible dose to the heart with the separate "angled" IMN-field technique.

Breast Neoplasms↗
PubMed1991

[Interstitial Ir-192 afterloading therapy with sequential warm-water hyperthermia].

For selective heating of superficially located or easily accessible tumors interstitial hyperthermia has become an increasing popular method in combination with interstitial radioactive implants. At our institution the hyperthermia treatment is performed utilizing the warm water system KHS-9, which is adapted to our Ir-192 high-dose-rate afterloading device, so that the same hollow needles for the interstitial radiation can be used for the heating procedure. So far, this technique has been applied for the treatment of primary and carcinomas, gynecological recurrences, and metastases of malignant melanomas after preceding in vitro measurements of temperature distribution. As a result both, in vitro and in vivo investigations showed good homogeneity of the temperature throughout the heated volume. Analysing the temperature data of in vivo measurements the maximum deviation of temperature was found to be 1.5 degrees C. When using a needle spacing of 8 mm, the temperature required for clinical application (42.5 degrees C) could be maintained in all heat treatments with a preselected water temperature of 46 degrees C to 49.5 degrees C.

Anus Neoplasms↗
PubMed1990

[Treatment of primary cancer of the fallopian tube].

33 patients treated since 1970 at the Medical School of the University of Graz, were classified using the FIGO system for ovarian carcinoma, fourteen were in stage I, 8 stage II, 8 stage III and 3 stage IV. In 17 patients, surgery consisted of total abdominal or vaginal hysterectomy with bilateral salpingo-oophorectomy; 12 patients underwent additional pelvic +/- paraaortic lymph node extirpation and in 4 the tumour excision was incomplete. Treatment in 6 patients was surgery alone (2/stage I, 4 with advanced disease) (Group A). Adjuvant radiotherapy was performed in 14 patients (Group B); the remaining patients were treated with single (2/13) or multiple agent chemotherapy (11/13) (Group C). The 3-year survival rate was 55% for stage I, 42% for stage II; 10/11 of the stage III/IV patients died within 26 months. The 4-year actuarial survival rate for group B was 68%, for group C 11%. There was no difference between the short-time results of stage II tumours when comparing radiotherapy against chemotherapy. The tumour progression rate was 60%, indicating the need for radical surgery as well as for more aggressive adjuvant treatment. Surgery alone is recommended for stage I disease confined to the mucosa. More advanced disease (extension to the serosa, stage Ic, stage II) requires whole abdominal irradiation with a boost to the pelvic lymph nodes. For stage III/IV tumours a multi-modality treatment is recommended. Chemotherapy (cis-platinum, cyclophosphamide) for recurrent disease resulted in remission in some cases.

Adenocarcinoma↗
PubMed1990

[A therapeutic concept for the treatment of inoperable esophageal carcinoma].

From 1/87 to 12/88, 20 patients with anatomically or functionally inoperable carcinomas of the esophagus (cT1-3/N0-2/M0-1) were treated by endoluminal Ir-192 HDR brachytherapy (1-3 sessions, each 5-7 Gy) and percutaneous irradiation (50-70 Gy/2 Gy). In 10 cases a bouginage or combined dilatation and retrograde Nd-Yag-laser debulking was done before irradiation. The response of the treatment was documented by endoscopy (degree of stenoses) and symptoms (dysphagia score according to De Meester). In 95% of all cases the degree of stenoses was diminished and an improvement of dysphagia was found in 100%. The mean duration of oral uptake of properly chewed food could be prolonged to 308 days.

Brachytherapy↗