E. Piovan

Gamma Knife Stereotactic Radiosurgery for Uveal Melanoma: Clinical Results after 2 Years

We report on 36 cases of uveal melanoma treated at our center between March 1993 and September 1995. There were 16 men and 20 women, aged 57 +/- 11 years. The choroid was affected in 35 patients and the ciliary-body in 1. The same preoperative and follow-up protocol was adopted for all cases. The procedure included fixation and positioning of the eye with a retrobulbar injection of long-lasting anesthetic and two extraocular muscle sutures, application of the frame, computed tomography scan localization, dose planning and treatment with the Gamma Knife. The patients were divided into three groups. Group A: 10 patients with a follow-up of 24 +/- 4 months, treated with a high dose (surface dose 58 +/- 9 Gy, maximum dose 81 +/- 15 Gy, mean dose 66 +/- 11 Gy). Group B: 9 patients with a follow-up of 16 +/- 2 months, treated with a lower dose (surface dose 41 +/- 3 Gy, maximum dose 76 +/- 10 Gy, mean dose 53 +/- 11 Gy). Group C: 17 patients with a follow-up of 6 +/- 3 months, treated with a lower dose (surface dose 42 +/- 3 Gy, maximum dose 72 +/- 16 Gy, mean dose: 54 +/- 6 Gy). In group A, we observed marked tumor regression in 9 cases, tumor recurrence in 1 case and severe complications in 5 cases (neovascular glaucoma and/or radiation retinopathy and/or radiation optic neuropathy). In group B, significant local control of the tumor was obtained with minor complications (cotton wool spots hard exudates, intraretinal hemorrhages). In group C, to date we have observed a regression of the tumor in 7 cases and 1 severe complication (neovascular glaucoma). Our data show that uveal melanomas may be adequately controlled by a high radiosurgical dosage (50-70 Gy), though there are significant side effects. Comparable levels of local tumor control may be obtainable using lower doses (40-45 Gy) which would hopefully reduce the rate of complications. However, a longer follow-up is needed for further validation of these results.

Gamma Knife Radiosurgery in Skull Base Meningiomas

Gamma Knife radiosurgery was performed on 50 patients (10 males and 40 females) with skull base meningiomas (SBMs) between February 1993 and September 1995. The patients ranged in age from 25 to 78 years (mean age 56 years). The location of the tumors was anterior fossa (n = 4), sphenoorbital (n = 2), sellar region (n = 5), cavernous sinus (n = 26), petroclival (n = 12), and occipital foramen (n = 1). The tumor volume ranged from 0.6 to 20 cm3 (mean 8.6 cm3). The mean values for dose planning were edge isodose (EI) 46.7%, edge dose (ED) 18.0 Gy, maximum dose 39.8 Gy, average dose (AD) 25.4 Gy, and average number of isocentres 5.7. The patients were analyzed for five parameters: tumor volume (< 7.5 vs. > or = 7.5 cm3); EI (< 50 vs. > or = 50%); ED (< 18 vs. > or = 18 Gy); AD (< 25 vs. > or = 25 Gy), and primary versus residual or recurrent tumors. The overall frequency of tumor growth control (TGC) was 98%, with 1- and 2-year TGC rates of 97% and 100%, respectively. The most favorable neurological results were obtained with a tumor volume < 7.5 cm3 (p < 0.05), EI > or = 50% (NS), ED > or = 18 Gy (NS) and with primary SBMs (p < 0.01). A favorable TGC was demonstrated at follow-up imaging examinations when the tumor volume was > or = 7.5 cm3 (100% TGC rate), EI < 50% (100%), ED > or = 18 Gy (100%), AD > 25 Gy (100%), in both primary SBMs (100%) and residual or recurrent SBMs (96.5%). To date, only 3 (6%) of the 50 patients have presented signs of neurological worsening related to the Gamma Knife radiosurgery. While no early complications were noted, neuroradiological follow-up did show delayed transient imaging complications (3 edema and 1 radionecrosis; 8% of all patients). In conclusion, our preliminary results seem to confirm that Gamma Knife radiosurgery is an effective and safe adjuvant or a feasible alternative primary treatment in controlling or preventing SBM progression.

Stereotactic Radiosurgery of Uveal Melanomas: Preliminary Results with Gamma Knife Treatment

Twelve cases of uveal melanoma (T3N0M0:11 patients, T4N0M0:1 patient) treated with Gamma Knife stereotactic radiosurgery are reported. Our protocol includes preoperative ocular and systemic assessments with complete ocular examination, ophthalmoscopy, fundus photography, fluorangiography, standardized echography, CT and MRI, chest X-rays, liver echography and blood tests. The follow-up program is mainly based on echographic evaluation of tumor thickness and size. The procedures include fixation of the eye, application of the stereotactic Leksell frame G, CT/MRI localization of the melanoma, dose planning and treatment with the Gamma Knife (B type). A mean surface dose of 55 +/- 10 Gy was administered at the 60-90% isodose curve using 4- to 14-mm collimators and a number of shots ranging from 1 to 6. A significant reduction (10-41%) in echographic thickness of the tumor was shown in 6 cases with a follow-up of 3-12 months. In 4 patients, the tumor size was still unchanged after 1-10 months. The single high-dose radiation delivered to the target and the high spatial accuracy are the main advantages of stereotactic radiosurgery for the treatment of posterior uveal melanomas. A longer followup is needed to further validate this new application of Gamma Knife radiosurgery.

Computerized tomography and magnetic resonance guided stereotactic brain biopsy in nonimmunocompromised and AIDS patients.

BACKGROUND The utility of stereotactic brain biopsy (SBB) in AIDS patients still remains controversial. The authors investigated SBB-related diagnostic accuracy, complications, and postoperative sequelae in nonimmunocompromised (NIC) patients and AIDS patients. The role of bioptic yield in treatment planning was also studied in AIDS patients. METHODS From 1990-95, 200 computerized tomography (CT) or magnetic resonance imaging (MRI)-guided SBBs were performed in our Department; 172 bioptic procedures were performed in NIC patients (169), and 28 SBBs in AIDS patients (27). The statistical significance was evaluated using the Fisher exact t-test. RESULTS SBB accuracy was very high in both NIC (94.8%) and AIDS (92.9%) patients. Statistical analysis indicated nonsignificant (NS) differences between the two study groups (P > 0.05). Diagnostic yield resulted higher in contrast-enhancing (CE) brain lesions (98.6% in NIC and 95.0% in AIDS patients; P > 0.05; NS), than in non-CE lesions (74.1% in NIC and 87.5% in AIDS patients; P > 0.05; NS). The overall complication rate was similar in both groups (17.2% in NIC and 14.8% in AIDS patients, P > 0.05, NS). The most frequent complication was hemorrhage, with statistically negligible differences between the two study groups (P > 0.05). The frequency of complications involving minor/major morbidity or mortality was very low in NIC (5.9%, 0.6%, and 2.4%, respectively), and in AIDS (3.7%, 7.4%, and 0.0%, respectively) patients. Regarding the therapeutic impact of bioptic diagnosis for neuro-AIDS patients, the preoperative treatment attitude was modified in 23/27 cases (85.2%), and the empiric anti-toxoplasmosis regimen was changed or withdrawn in 17/21 patients (81.0%). CONCLUSION Our experience demonstrated SBB to be an accurate, manageable, and reasonably safe diagnostic tool in both NIC and AIDS patients. These results suggest also that timely SBB indication in selected AIDS patients, reaching an early diagnosis, may on one side prevent unnecessary and potentially toxic empiric therapeutic regimens, and on the other address the appropriate treatment, thereby improving length and quality of life in such patients.

Shape recovery and volume calculation from biplane angiography in the stereotactic radiosurgical treatment of arteriovenous malformations

PURPOSE A model for calculating the three-dimensional volume of arteriovenous malformations from biplane angiography. METHODS AND MATERIAL Three-dimensional (3D) volume reconstruction is easily feasible with axial, coronal, or sagittal computer tomography (CT) and nuclear magnetic resonance (NMR) scans. On the other hand, radiosurgical treatment of arteriovenous malformations (AVM) is exclusively based on two orthogonal stereotactic projections, obtained with angiographic procedures. Most commonly, AVM volumes have been calculated by assimilating the nidus volume to a prolate ellipsoid. We present an algorithm dedicated to 3D structure reconstruction starting from two orthogonal stereotactic projections. This has been achieved using a heuristic approach, which has been widely adopted in the artificial intelligence domain. RESULTS Tests on phantom of different complexity have shown excellent results. CONCLUSION The importance of the algorithm is considerable. As a matter of fact: (a) it allows calculations of complex structures far away from regular ellipsoid; (b) it permits shape recovery; (c) it provides AVM visualization on axial planes.

Quality Assessment of Magnetic Resonance Stereotactic Localization for Gamma Knife Radiosurgery

Artifacts in magnetic resonance imaging (MRI) may lead to anatomical distortion and inaccurate stereotactic coordinates. A special phantom for MRI and computed tomography (CT) was built to test the quality and precision of the two neuroradiological procedures. The phantom is fixed with the Leksell frame, and it has 15 orthogonal markers visible by CT and MRI techniques. The coordinates of the markers were calculated first on the CT scans and then on MR images. Two groups of different distortions were analysed: artifacts depending on the frame and its components and artifacts depending on the MR unit and image characteristics. A good target-coordinate correlation was found between CT and MRI in the axial plane, while in the coronal plane there was always a small error. This error is not constant, but changes from test to test, consequently it is hard to reform the image.

Combined Treatment of Brain AVMs: Analysis of Five Years (2000-2004) in the Verona Experience

In recent years the management of brain AVMs has evolved both because of new materials and for the modification of treatment strategies. With regard to materials, newly developed improved microcatheters and microwires have allowed increasingly distal locations to be reached; N-Butyl-2-cyanoacrilate (Glubran 2) has recently substituted Isobutyl-2-cyanoacrilate (IBCA), and a completely new non-adhesive embolic agent (Onyx) is increasingly being used in many centres as a reliable alternative or as first choice agent. Concerning treatment strategies it must be noted that radiosurgery, now available in many centres, is being used with increasing frequency as an alternative to surgery. Furthermore when associated with embolization, radiosurgery has allowed AVMs, which were previously considered untreatable, to be dealt with.

Gamma Knife Stereotactic Radiosurgery of Ocular Metastases: A Case Report

A case of a choroidal metastasis treated with Gamma Knife stereotactic radiosurgery is reported. A 48-year-old Caucasian man afflicted with lung cancer (adenocarcinoma) was referred to the University Hospital of Verona, Italy, for loss of vision in his left eye due to a choroidal mass with exudative retinal detachment. Clinical investigation was conclusive of a well-defined, bilobed choroidal metastasis located in the temporal and inferior portion of the posterior pole of the eye. The lesion was characterized by a maximum thickness of 5.2 mm and a maximum lateral extension of 14 mm. The staging was negative for other metastatic localizations. Using the Gamma Knife technique, a surface dose of 25 Gy was administered at the 50% isodose line using the 8-mm collimator (5 shots) with equally weighted fields. After a 3-month follow-up period, a marked reduction in the lesion size as well as in the exudative retinal detachment was observed. This improvement was unchanged 6 months after the treatment, and the lesion appeared completely controlled. To the best of our knowledge, this is the first case report of an ocular metastasis treated with stereotactic Gamma Knife radiosurgery.

Gamma knife radiosurgery in AIDS-related primary central nervous system lymphoma

The frequency of AIDS-associated primary central nervous system (PCNS) lymphoma is rapidly increasing in adults and children. In AIDS-related PCNS lymphoma, different authors have reported an overall poorer response rate to conventional radiation compared with immunocompetent patients. This poorer response consists of a significantly positive, although transient effect on survival following radiotherapy (XRT), with a poor toleration for prolonged whole-brain RT (WBR) and with radiation-induced changes within the normal CNS tissue on autopsy examinations after a course of XRT. These observations led us to consider highly focused single-session radiosurgical treatments as a potentially useful therapeutic modality for AIDS-associated PCNS lymphomas. A multi-institutional diagnostic and therapeutic protocol for the evaluation and treatment of AIDS patients with high-risk intracerebral space-occupying lesions has been developed at the University Hospital of Verona. Therapy is based on tumor biopsy. Tumors < or = 3.5 cm in diameter are subjected to Gamma Knife radiosurgery, whereas tumors < or = 4.5 cm are treated with stereotactic brachytherapy. At the Department of Neurosurgery, Verona, Italy, Gamma Knife treatment was performed in 2 cases of deep-seated histologically verified malignant non-Hodgkins lymphoma. A short-term cliniconeuroradiological follow-up (2 months later) showed neurologic improvement and virtually complete disappearance of the tumor in both patients. The excellent local control and the well-tolerated single-session treatment and absence of brain toxicity signs on CT scan indicate a putative role for Gamma Knife radiosurgery in the treatment of these patients.

Operative classification of brain arteriovenous malformations.

The first description of brain arteriovenous malformations (AVMs) can be found in the observations of Luschka1 and Virchow2 in the mid 19th century: they were generally categorized as vascular hamartomas. It is believed that the majority of these lesions are congenital in origin, arising between three and eight weeks of gestation3-5. Morphologically, they resemble the normal anastomotic plexuses formed during the early embryogenesis of the brain vascular system. Several recent studies have revealed possible factors involved in the formation and pathogenesis of AVMs. In particular, the gene that results in the production of endothelin-1, the potent vasoconstrictor agent involved in vascular cell growth, has been found to be repressed in cerebral AVMs; this may be the possible cause of the abnormal autoregulation found in AVMs6.