Optimizing Intracranial Metastasis Detection for Stereotactic Radiosurgery

Abstract

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 ≤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.

Usefulness of Double Dose Contrast-enhanced Magnetic Resonance Imaging for Clear Delineation of Gross Tumor Volume in Stereotactic Radiotherapy Treatment Planning of Metastatic Brain Tumors: A Dose Comparison Study

“…Accurate delineation of GTV is essential in proper dose planning for successful SRT. Accurate GTV delineation depends on use of higher doses of contrast medium (as demonstrated in this study), as well as thinner image slices through the tumor and accurate positioning of the fixation device attached to the linear accelerator [17][18][19]. Assessment of tumor targeting with accurate delineation of GTV is a very challenging task because the majority of metastatic brain tumors occur by hematogenous spread of cancer cells, which proliferate and extend to the surrounding brain tissue irregularly by a neovascularization process.…”

Use of 3.0-T MRI for Stereotactic Radiosurgery Planning for Treatment of Brain Metastases: A Single-Institution Retrospective Review

“…Donahue et al (11) used triple-dose contrast and a magnetization-prepared rapid gradient echo sequence in 47 patients treated with radiosurgery for brain metastases and reported a 49% improvement in detection rate. By comparison, the radiosurgery treatment planning protocol at the University of Pittsburgh uses double-dose contrast, 1.5-T MRI, 2-mm slices with no spacing, and a fast spoiled GRASS (gradient-recalled acquisition in the steady state) sequence and has reported a 29% improvement in detection rates over conventional diagnostic protocols (12). More recently, focus has shifted to other strategies for optimizing the detection of occult brain metastases, including the use of high relaxivity contrast agents.…”

Outcomes Following Gamma Knife for Metastases

“…First, many patients who appear to have a single visible intracranial lesion on computerized tomography (CT) have subsequently been found to have multiple lesions on Gd-MRI (Bronen & Sze, 1990;Davis, 1991). Further, increased gadolinium dose and increased MRI scan resolution results in the detection of further additional lesions in 30-40% of patients (Engh, 2007;Hanssens, 2011;Patel, 2011b). The finding of multiple lesions may alter plans for potential surgical management.…”