Control of brain metastases using frameless image-guided radiosurgery

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Radiosurgery is an important and well-accepted method in the management of brain metastases. Using conventional frame-based techniques, high lesional control rates are expected. The introduction of image-guided techniques allows for improved patient comfort and workflow. Some controversy exists as to the accuracy of imageguided techniques and consequently the impact they might have on control of brain metastases (as opposed to the level of control achieved with frame-based methods). The authors describe their initial 15-month experience with image-guided radiosurgery (IGRS) using Novalis with ExacTrac for management of brain metastases.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The authors reviewed the cases of brain metastasis treated by means of IGRS in their tertiary regional radiation oncology service over a 15-month period. During the study period 54 patients (median age 57.9 years) harboring 108 metastases were treated with IGRS. The median time from cancer diagnosis to development of brain metastasis was 12 months (range 0–144 months). The median tumor volume was 0.98 cm<jats:sup>3</jats:sup> (range 0.03–19.07 cm<jats:sup>3</jats:sup>). The median prescribed dose was 18 Gy to the 80% isodose line (range 14–20 Gy). Lesions were followed with postradiosurgery MR imaging every 2–3 months following treatment.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>The median follow-up period was 9 months (range 0–20 months). Median actuarial survival was 8.6 months following IGRS. Eight patients with 18 lesions died within the first 2 months after the procedure, before scheduled follow-up imaging. Thus 90 lesions (in 46 patients) were followed up with imaging studies. Lesions that were unchanged or reduced in size were considered to be under control. The 6-month actuarial lesion control rate was 88%. Smaller lesions (&lt; 1 cm<jats:sup>3</jats:sup>) had a statistically improved likelihood of complete imaging response (loss of all contrast-enhancement p = 0.01).</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Image-guided radiosurgical treatment of brain metastases resulted in high rates of tumor control comparable to control rates reported for frame-based methods. High control rates were seen for small lesions in which spatial precision in dose delivery is critical. These data suggests that in regard to lesion control, IGRS using Novalis with ExacTrac is equivalent to frame-based radiosurgery methods.</jats:p></jats:sec>

Dosimetric comparison of 2.5 mm vs. 3.0 mm leaf width micro-multileaf collimator-based treatment systems for intracranial stereotactic radiosurgery using dynamic conformal arcs: implications for treatment planning

“…18,19 Therefore, the use of IDS indicating the specifi c target coverage (e.g., D95) is recommended as an objective metric for evaluation and comparison of "marginal dose" when the treatment results are compared among the m3 add-on, "classic" Novalis, and Novalis Tx systems.…”

“…18,19 Stereotactically localized computed tomography (CT) scans were obtained with contiguous 2-mm slices. T1-weighted postcontrast magnetic resonance (MR) images were acquired with 2-mm slices without fi ducial markers and were co-registered with the CT scans using a mutual information-based algorithm implemented in both TPSs.…”

Accurate Reading with Sequential Presentation of Single Letters

“…Worldwide, over a dozen teams are developing visual prostheses, which aim to return some visual sensitivity to blind people by electrically stimulating the retina (Argus II Retinal Prosthesis System, Second Sight Medical Products Inc “Argus II”; Dowling, 2009; Zrenner et al, 2011), lateral geniculate nucleus in the thalamus (Pezaris and Reid, 2007; Pezaris and Eskandar, 2009), or primary visual cortex (Brindley and Lewin, 1968; Dobelle and Mladejovsky, 1974; Dobelle et al, 1974; Schmidt et al, 1996; Bradley et al, 2005; Tehovnik and Slocum, 2007). Localized stimulation in any of these regions along the early visual pathway can produce the percept of a small patch of light, referred to as a phosphene.…”

Characterisation of dose distribution in linear accelerator-based intracranial stereotactic radiosurgery with the dynamic conformal arc technique: consideration of the optimal method for dose prescription and evaluation

“…The dose prescription has been commonly defined at the specific percentage isodose surface (IDS) (e.g. 80% or 90%) normalised to 100% at the isocentre in many institutions [5][6][7][8][9][10][11][12]. Because the planning methods and the selection of the prescription IDS have been left to the discretion of each institution, a substantial variability has been observed in the method of dose prescription and/or in the assessment of a ''marginal dose'' [1,[5][6][7][8][9][10][11][12].…”