Spatial accuracy of the stereotactic Leksell®Vantage™ head frame in comparison with the standard stereotactic Leksell®G Frame for Gamma-Knife.

Purpose. Since January 2021, the Leksell®Vantage head frame (V-frame) is used for Gamma Knife®treatments in addition to the historical Leksell®G-Frame known as the reference. The aim of this study was to compare the spatial accuracy of treatments with these two frames.Methods. Firstly, the constancy of the geometric accuracy of the system according to the Elekta quality assurance process was carried out during sixteen months with V and G-frames' adaptors. Then, End-to-end test was carried out with both V and G-frame using an anthropomorphic phantom and Gafchromic®films. The overall precision of the radiation center was calculated as the displacement vector for a 4 mm collimator shot. Additionally, the Cone Beam Computed Tomography (CBCT) positioning system was used to assess the precision of the Leksell coordinates system defined by V-frames on 64 patients in comparison to G-frames for 46 patients. To ensure that patient's head movement was not possible during treatment with the V-frame, the High Definition Motion Management (HDMM) system was used and a final CBCT was performed at the end of the irradiation.Results. The QA constructor's tests done with the G-frame and V-frame adaptor gave similar results over sixteen months. End-to-end tests demonstrated that the mean positioning accuracy was 0.54 mm (SD of 0.14 mm) and 0.70 mm (SD of 0.14 mm) with V-frame and G-frame respectively. The displacement vector given by CBCT ranged from 0.02 to 1.05 mm with a mean value of 0.38 mm (SD of 0.18 mm) for the 64 V-framed patients and from 0 to 0.92 mm with a mean value of 0.31 mm (SD of 0.18 mm) for the 46 G-framed patients. The mean translation movement between the beginning and the end of the 64 treatments with V-frame was 0.08 mm (SD of 0.04 mm, maximum value of 0.19 mm).Conclusion. We estimated that V-frames are as precise as G-frames with a targeting accuracy of less than 1 mm.

Stereotactic radiosurgery for post operative brain metastasic surgical cavities: a single institution experience.

BACKGROUND: The standard therapy for brain metastasis was surgery combined with whole brain radiotherapy (WBRT). The latter is however, associated with important neurocognitive toxicity. To reduce this toxicity, postoperative stereotactic radiosurgery (SRS) is a promising technique. We assessed the efficacy and the tolerance to postoperative Gamma Knife radiosurgery (GK) on the tumor bed after resection of brain metastases. METHODS: Between February 2011 and December 2016, following macroscopic complete surgical resection, 64 patients and 65 surgical cavities were treated by GK in our institution. The indication for adjuvant radiosurgery was a multidisciplinary decision. The main assessment criteria considered in this study were local control, intracranial metastasis-free survival (ICMFS), overall survival and toxicity. RESULTS: Median follow-up: 11.1 months. Median time between surgery and radiosurgery: 35 days. Median dose was 20 Gy prescribed to the 50% isodose line, for a median treated volume of 5.6 cc. Four patients (7%) suffered from local recurrence. Local recurrence-free, intracranial recurrence-free and overall survival at 1 year were 97.5%, 57.6% and 62.4% respectively. In total, 23 patients (41%) suffered from intracranial recurrence outside the tumor bed. In univariate analysis: concomitant GK treatment of multiple lesions and the tumor bed was associated with a decrease in ICMFS (HR = 1.16 [1.005-1.34] p = 0.04). In multivariate analysis: a non-lung primary tumor was significantly associated with a decrease in ICMFS (HR = 8.04 [1.82-35.4] p = 0.006). An increase in performance status (PS) and in the initial number of cerebral metastases significantly reduced overall survival (HR = 5.4 [1.11-26.3] p = 0.037, HR = 2.7 [1.004-7.36] p = 0.049, respectively) and One radiation necrosis histologically proven. CONCLUSION: Our study confirmed that postoperative GK after resection of cerebral metastases is an efficient and well-tolerated technique, to treat volumes of all sizes (0.8 to 40 cc). Iterative SRS or salvage WBRT can be performed in cases of intracranial relapse, postponing WBRT with its potential side effects.

Is Real-Time Inverse Planning Optimizing Dose to the Normal Brain? A Prospective Comparative Trial in a Series of Brain Metastases Treated by Stereotactic Radiosurgery.

BACKGROUND: Radiosurgery has demonstrated good safety and efficacy in the treatment of multiple brain metastases (BMs). However, multi-target dose planning can be challenging and time-consuming. A recently developed real-time inverse treatment planning (IP) by convex optimization has been demonstrated to produce high-quality treatment plans with good conformity and selectivity in single-target plans. We intended to test the capacity of this IP to rapidly generate efficient plans while optimizing the preservation of normal tissue in multiple BM. METHODS: Seventy-nine patients (mean age 62.4, age range 22-85) with a total of 272 BMs were treated by Gamma Knife Radiosurgery. All subjects were treated using a forward planning (FP) technique by an expert neurosurgeon. The new Intuitive Plan was applied and able to automatically generate an alternative plan for each patient. All planning variables were collected from the IP to be compared with the corresponding measurements obtained from the FP. A paired sample t test was applied to compare the 2 plans for the following variables: brain volumes receiving 10 Gy (V10) (primary endpoint), and 12 Gy (V12), planning indices (selectivity, coverage, gradient, and Paddick Conformity Index [PCI]), beam-on time (BOT), and integral doses. Additionally, the noninferiority margin for each item was calculated, and the 2 plans were compared for noninferiority using a paired t test. RESULTS: The mean age of patients was 62.4 years old (age range 22-85), with a sex ratio of 1.02. The average number of lesions per patient was 3.4 (range 1-12). The mean prescription dose was 21.46 Gy (range 14-24 Gy). Noninferiority of the IP was concluded for V10, V12, prescription isodose volume, BOT, PCI, and selectivity. The V10 (and V12) was significantly lower with the IP (p < 0.001). These volumes were 8.69 cm3 ± 11.39 and 5.47 cm3 ± 7.03, respectively, for the FP and 7.57 cm3 ± 9.44 and 4.78 cm3 ± 5.86 for the IP. Only the coverage was significantly lower with the IP (-2.3%, p < 0.001), but both selectivity (+17%) and PCI (+15%) were significantly higher with the IP than FP (p < 0.001). CONCLUSION: This IP demonstrated its capacity to generate multi-target plans rapidly, with a dose to the brain (V10) and BOT noninferior to the one of a human expert planner. These results would benefit from confirmation in a larger prospective series.

VNS implantation in a NF1 patient: massive nerve hypertrophy discovered intra-operatively preventing successful electrode placement. Case report.

For the vast majority of surgeons, no specific investigation is necessary before vagal nerve stimulation (VNS) implantation. We report our intraoperative unexpected finding of a massively enlarged vagus nerve in a patient with neurofibromatosis type 1 (NF1). The nerve hypertrophy prevented wrapping the coils of the helical electrode. The patient had no signs of vagus nerve dysfunction preoperatively (no hoarseness or dysphonia). This exceptional mishap is undoubtedly related to NF1-associated peripheral nerve sheath tumors. Even though it is not advisable to routinely perform any imaging prior to VNS, in such specific context, preoperative imaging work-up, especially cervical ultrasound, might be judicious to rule out any asymptomatic enlarged left vagus nerve.