Faculty Bibliography

The effects of radiosurgery on brain tumor tissue remain to be defined. Effects are dose, volume, time, and tumor histology dependent. In this report, we discuss data from resected specimens after radiosurgery, and work to develop a classification method for radiosurgery effects.

The term radiosurgery signifies any kind of application of ionizing radiation energy, in experimental biology or clinical medicine, aiming at the precise and complete destruction of chosen target structures containing healthy and/or pathological cells, without significant concomitant or late radiation damage to adjacent tissues. The goal of this study is to explore the short- and long-term pathophysiological effects of high-dose focused irradiation on neural tissue and its pathologies with histological, electron-microscopical tissue culture and biological-biochemical methods. Radiosurgical pathology focuses its scope and microscope on tissue, cellular, genetic and molecular changes in the human organism and experimental animals, or in cell lines and other in vitro experiments, generated by the ionizing radiation delivered from radiosurgical devices.

BACKGROUND AND PURPOSE: The authors characterize the detection of additional intracranial metastases in cancer patients at the time of stereotactic radiosurgery (SRS) using a specialized high-resolution magnetic resonance imaging (MRI) protocol. METHODS: A retrospective review of 150 consecutive radiosurgical procedures for patients with < or =5 known metastatic intracranial tumors diagnosed using MRI was undertaken at a single center. On the day of SRS, all patients underwent rigid head fixation in a stereotactic frame followed by a specialized MRI using a 3-dimensional fast spoiled-gradient sequence on a 1.5-tesla magnet with double-dose gadolinium. Axial imaging was performed using 2-mm cuts and no gap. RESULTS: Additional metastases were detected in 29.3% of patients. The number of known tumors before SRS was predictive of additional metastases being found (p = 0.014). In multivariate analysis, we more frequently found additional metastases at radiosurgery in patients with 3-5 previously known metastases (p = 0.005), in patients with non-small cell lung cancer (p = 0.012) and in patients with a longer time interval between their diagnostic MRI and their stereotactic MRI (p = 0.030). Age, sex and prior fractionated radiation therapy were not predictive factors. CONCLUSION: Our specialized protocol of high-resolution, double-dose contrast-enhanced MRI is a reliable method to evaluate the extent of intracranial disease in patients with known brain metastasis. Treatment planning for radiosurgery, radiation therapy and open surgical therapy are all impacted by improved metastasis detection.