[Dose-volume histogram regression analysis of uveal melanomas after single fraction gamma knife radiosurgery]. / Dosis-Volumen-Histogramm-Regressionsanalyse von Aderhautmelanomen nach einzeitiger Leksell-Gamma-Knife-Radiochirurgie.

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.

Long term results of radiosurgery for vestibular schwannomas.

UNLABELLED: Radiosurgery is either a primary or an adjunct management approach used to treat patients with vestibular schwannomas. The goals are long-term tumour growth control, maintenance of cranial nerve function and prevention of new neurologic deficiencies. We sought to determine long-term outcomes measuring the potential benefits against the neurological risks of radiosurgery. METHODS: 278 patients with vestibular schwannomas underwent Gamma Knife radiosurgery as a treatment modality for from April 1992 to November 2001. The long-term results of 60 patients were evaluated who received radiosurgery as primary treatment. 12 cases presented with previously performed subtotal microsurgical resection or recurrence of disease (12-96 months, median 39). The median treatment volume was 3.8 ccm and the median dose to the tumour margin was 12 Gy. The median patient follow-up time was 88 months (range 72-114 months). RESULTS: Four tumours progressed after primary radiosurgery. Tumour control rate was 93%. Useful hearing (Gardner-Robertson I/II) was preserved in 16 patients (55%). Clinical neurological improvement occurred in 36 patients (60%). Adverse effects comprised neurological symptoms (incomplete facial palsy) (House-Brackman II/III) in five cases (three recovered completely), mild trigeminal neuropathy in three cases, and morphological changes displaying rapid enlargement of preexisting macrocysts in two patients and tumour growth in two other ones. Microsurgical resection was performed in three cases (5%) and one patient underwent a shunting procedure because of hydrocephalus formation. In patients who had undergone previous microsurgery, neither new cranial nerve deficit nor any tumour growth was observed. CONCLUSIONS: Radiosurgery performed with current techniques proved to be an effective method for growth control of vestibular schwannomas with both a low mortality rate and a good quality of life. An increasing percentage of patients will undergo radiosurgery as accessibility to this alternative increases, and more data regarding long-term follow-up are available. It is a post-operative complementary treatment for partially removed tumours. Accordingly, radiosurgery is a useful method for the management of properly selected patients.

Radiosurgery of residual and recurrent vestibular schwannomas.

Radiosurgery is either a primary or an adjunctive management approach used to treat patients with vestibular schwannomas. We sought to determine outcomes measuring the potential benefits against the neurological risks in patients who underwent radiosurgery after previous microsurgical subtotal resection or recurrence of the tumour after total resection. Gamma Knife radiosurgery was applied as an adjunctive treatment modality for 86 patients with vestibular schwannomas from April 1992 to August 2001. We evaluated the results of 50 patients who had a follow-up of at least 3.5 years (median 75 months, range 42-114 months). In 16 patients a recurrence of disease was observed after previous total resection. The median treatment volume was 3.4 ccm with a median dose to the tumour margin of 13 Gy. Tumour control rate was 96%. Two tumours progressed after adjunctive radiosurgery. Useful hearing (Gardner-Robertson II) (4 patients (8%)) and residual hearing (Gardner-Roberson III) (10 patients (20%)) remained unchanged in all patients, who presented with it before radiosurgery, respectively. Clinical neurological improvement was observed in 24 patients (46%). Adverse effects comprised transient neurological symptoms and signs (incomplete facial palsy, House-Brackman II/III) in five cases (recovered completely), mild trigeminal neuropathy in four cases, and morphological changes displaying rapid enlargement of a pre-existing macrocyst in one patient and tumour growth in another one. No permanent new cranial nerve deficit was observed. Radiosurgery appears to be an effective adjunctive method for growth control of vestibular schwannomas and is associated with both a low mortality rate and a good quality of life. Accordingly, radiosurgery is a rewarding therapeutic approach for the preservation of cranial nerve function in the management of patients with vestibular schwannoma in whom prior microsurgical resection failed.

High-compared with low-dose radiosurgery for uveal melanomas.

OBJECT: The authors compared the results of gamma knife radiosurgery in patients with uveal melanoma who underwent high-dose (treated from 1992-1995) and low-dose irradiation (treated from 1996-2002). METHODS: Thirty-one patients with uveal melanomas were treated with a mean margin dose of 52.1 Gy (high dose) and 33 with a mean dose of 41.5 Gy (low dose), and results were compared between groups. The technical procedure was the same in each group except for radiation dose. In the low-dose group, complete tumor regression (scar formation) occurred in 12% and in the high-dose group in 26%. Partial regression (reduction of the tumor prominence between 50 and 80%) occurred in 81% of the low-dose group and in 58% of the high-dose group. Neovascular glaucoma as a severe complication developed in 9% of the low-dose group and in 48% of the high-dose group. CONCLUSIONS: Reduction of the margin dose from 52.1 to 41.5 Gy appears to achieve the same rate of tumor regression but is associated with a lower rate of severe side effects such as neovascular glaucoma. The follow-up period in the low-dose group, however, was much shorter.

[Radiosurgery of recurrent acoustic neurinoma or: the elegant solution of a surgical problem?]. / Die Radiochirurgie bei Akustikusneurinom-Rezidiv oder: Die elegante Lösung eines chirurgischen Problems?

BACKGROUND: Stereotactic radiosurgery has proved to be an effective alternative to microsurgical resection in treatment of acoustic neuroma. Still, microsurgery is considered by many to be the therapy of choice. In case of recurrence microsurgical resection is much more difficult because of scarring and has a higher risk of complications. Therefore in cases of recurrence the role of radiosurgery needed to be evaluated. PATIENTS AND METHODS: From April 1992 to July 1997 135 patients suffering from acoustic neuroma were treated at the Neurosurgical Department of the University Medical School of Graz by means of the gamma-Knife. 12 patients had recurrence after a single or several microsurgical resections. The age distribution was between 38 and 71 years with a mean of 57 years. The diameter of the tumors varied between 10.5 and 31.2 mm. RESULTS: In all 12 cases the tumors could be inactivated biologically in a mean follow-up period of 58.8 months by means of stereotactic radiosurgery. Tumor shrinkage was achieved in 3 cases (25%), central necrotic areas were observed in 8 cases (67%). No additional cranial nerve palsies occurred. CONCLUSIONS: Stereotactic radiosurgery has proven to be a safe and effective treatment option instead of repeated microsurgery. Stereotactic radiosurgery should be considered as the therapy of choice in cases of recurrent acoustic neuromas.

The minimally invasive approach to olfactory neuroblastoma: combined endoscopic and stereotactic treatment.

OBJECTIVES: To describe a new treatment modality of olfactory neuroblastoma consisting of endoscopic nasal and paranasal sinus surgery and stereotactic radiosurgery. STUDY DESIGN: Retrospective review of three patients suffering from olfactory neuroblastoma. METHODS: Review of the charts, the computed tomography, and magnetic resonance imaging scans, the operation reports, radiosurgical data, and follow-up. RESULTS: All three patients remained free of disease with excellent quality of life in respective follow-up periods of 71, 50, and 39 months. CONCLUSION: The combination of two minimally invasive therapies, endoscopic sinus surgery and stereotactic radiosurgery, provide a reliable new approach to the treatment of a series of olfactory neuroblastomas that offers excellent quality of life, less injury to the patient, fewer side-effects, and fewer long-term effects than other treatment strategies.

A quality assurance program in stereotactic radiosurgery using the Gamma Knife unit.

Because of the large single-fraction dose in stereotactic radiosurgery it is important to guarantee a high geometric and dosimetric accuracy. The paper represent the quality assurance program for the Gamma Knife unit at the University Clinic of Neurosurgery in Graz. The program includes the following procedures: timer control, mechanical radiation isocenter coincidence, trunnion centricity, helmet microswitches test, radiation output and relative helmet factors, dose profile verification, safety interlocks checks and software quality assurance. In summary, the mechanical accuracy and reproducibility of the Gamma Knife unit are < 1 mm. The geometric failure in stereotactic Gamma Knife treatment is limited by the human error in setting the clinical target volume and the spatial accuracy of dose delivery to the patient is limited by the accuracy of modern target localization procedures.

Cavernous sinus meningiomas--what is the strategy: upfront or adjuvant gamma knife surgery?

43 patients with meningiomas of the cavernous sinus form the basis of this study. Two patients were treated with microsurgery alone, 17 patients were treated by Gamma Knife radiosurgery (GKRS) as a primary treatment modality, and 24 patients underwent a combined treatment of microsurgery followed by GKRS. Therefore, in 17 patients the diagnosis rested on clinical and radiological criteria alone. Cranial nerve disorders (CND) related to open surgical treatment were infrequent in this material (3 of 13 patients) due to deliberate strategies of partial or subtotal resection aimed at sparing cranial nerves from surgical maneuvers. In contrast, 6 of 11 patients, admitted for GKRS from other institutions suffered from considerable CND after open surgery and showed only partial improvement after GKRS. In all GKRS cases, no radiation-related complications were seen after a follow-up of 18-62 months (mean 39 months). Moreover, in all cases tumor control was obtained with a stable tumor volume in 63%, reduction of volume in 34.5% and a disappearance of tumor in 2.5%. GKRS is not only an additional treatment for meningiomas involving the cavernous sinus, but may be offered to the patient as an alternative primary treatment.

Radiosurgery in lesional epilepsy: brain tumors.

The purpose of this study was to examine the effects of different doses of radiation to the brain tissue immediately adjacent to tumors which were associated with epilepsy. From April 1992 to December 1995, 26 patients with medically intractable tumor epilepsy (mean duration 6.9 years, range: 1-27 years) have been treated with Gamma Knife radiosurgery (GKRS). Clinical and imaging controls were available for 24 patients with a mean follow-up of 2.25 years (range: 1-4.4 years). Tumor control had been achieved in all patients. The patients were divided into two groups according to the volume of tissue outside the tumor which had received 10 Gy or more. This volume was assessed by measuring the ratio of the tumor and the ratio of the volume within the isodose containing 10 Gy (10G/Tum ratio). 54 percent of all the 24 patients achieved an excellent result according to the Engel classification (class I or II). The patients were divided into two groups. In group I were 12 patients, and the 10G/Tum ratio was 3 or less. In group II there were 12 patients and the 10G/Tum ratio was more than 3. In group I the mean value for the 10G/Tum ratio was 2 (range 0.86 to 2.9). In group II the mean value of the ratio was 11.1 (range 3.13 to 63.2). In group I only 42% of patients achieved an excellent result compared with 66% in group II. Moreover, the location of the tumor had an effect on the results, in that temporal tumors were associated with excellent results in 64% of cases as opposed to 40% in extratemporal tumors. Finally, if the epilepsy had lasted for 2.5 years or less there were excellent results in 70% of patients, as opposed to 43% excellent results for patients who had suffered epilepsy for more than 2.5 years.

A new UHV angle encoder for high-resolution synchrotron radiation monochromators.

The high precision of 0.1 arcsec required for the positioning of optical elements in new two-axes monochromators at the undulator beamlines at BESSY II has led to the development of UHV-compatible high-precision angle encoders. Mounted directly on the rotation axes, they provide substantial advantages over measuring systems connected outside the vacuum vessel. Making use of a fast closed-loop control system, an accuracy of 0.1 arcsec at a resolution of less than 0.01 arcsec has been experimentally verified.

Stereotactic radiosurgery of skull base meningiomas.

Between April 1992 and February 1996, 97 patients with skull base meningiomas were treated at our department. The age of these patients ranged from 10 to 80 years. The male/female ratio was 1/2. Fifty-three of these patients had primary open surgery for partial removal or recurrent growth and subsequent radiosurgical treatment. Radiosurgery was performed as a primary treatment in 44 patients. The mean tumor volume was 13.7 cm3 (range: 0.8-82 cm3). These tumor volumes could be covered by mean isodose volumes of 45% (range: 20-70%) and were treated by a mean dose of 13.8 Gy (range: 7-25 Gy) at the tumor border. Six patients underwent radiosurgery with a staged treatment protocol with 4.6-6 months interval. In 78 patients, a total of 102 follow-up scans were available. The remaining 19 patients have not been included in the post-radiosurgical evaluation since the observation time was either too short or the patients were lost for follow-up. The mean interval between gamma knife treatment and last follow-up scan was 18.5 months, with a range from 6 to 46 months. Follow-up imaging (CT, MRI or both) revealed a decreased volume of the tumor in 31 cases (40%). In 44 cases (56%), tumor progression was stopped, and in 3 cases (4%) increased tumor volumes could be observed. In 8 cases marked central tumor necrosis was seen. Neurological follow-up examinations in 76 patients showed a stable neurological status in 71%, ameliorated status in 24% and worsening in 5% of the patients.