RESUMO
PURPOSE: To explain the principles and indications of gamma knife radiosurgery and to illustrate the correlated neuroimaging features. METHODS AND MATERIAL: Between December 1999 and July 2007, 1620 patients were treated by GK for a large variety of indications (metastasis 26%, vascular malformations 7%, trigeminal neuralgia 14%, pituitary adenoma 3%, primary CNS tumour 8%, other tumours 6%, vestibular schwannoma 19%, meningioma 17%, functional disorders <1%). The patients benefited from MRI follow-ups. RESULTS: MRI is the imaging technique of choice for Gamma knife radiosurgery (GKRS) in almost all indications. Computed Tomography, Digital Subtraction Angiography and Positron Emission Tomography have an additional role in some indications. Significant MRI data is illustrated in most indications. Evaluation of the treatment is mainly performed using MRI follow-up studies. The main features of these MRI follow-ups are described. Stabilisation or shrinking of the lesions volumes was generally observed. T2 relaxation times were also modified in and around the treated target areas, in patients responding to treatment and without any symptomatic complications. Modifications in contrast uptake were also observed in those patients. A few patients presented symptomatic complications associated with T2 signal anomalies. The interpretation of those modifications is discussed. CONCLUSION: MRI is the method of choice for GKRS planning in most indications. Imaging changes after radiosurgery provide the best quality control available to assess the response to radiosurgical treatment and to identify and monitor potential complications.
