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Stereotactic ablative radiotherapy (SABR) aims to deliver high doses of radiation to kill cancer cells and shrink tumors in less than or equal to 6 fractions. However, organ motion during treatment is a challenging issue for this kind of technique. We develop a control system via Bluetooth technology to simulate and correct body motion during SABR., Methods: Radiation doses were analyzed, and the radiation damage protection capability was checked by external beam therapy 3 (EBT3) films irradiated by a linear accelerator. A wireless signal test was also performed. A validation was performed with 8 previously treated patient respiratory pattern records and 8 healthy volunteers., Results: The homemade simulation system consisted of 2 linear actuators, one movable stage with a maximal moving distance of 6.5 cm × 12.5 cm × 5 cm to simulate the respiratory pattern of 8 patients precisely with a median error of 0.36 mm and a maximal motion difference of 1.17 mm, and 3.17 and chipset transited signals to display them as a waveform. From the test with 8 volunteers, the chip could detect deep respiratory movement up to 3 cm. The effect of the chip on a radiation dose of 400 monitor units (MUs) by 6 MV photons and 200 MUs by 10 MV photons showed high penetration rates of 98.8% and 98.6%, respectively., Conclusions: We invented a tubeless and wireless respiratory gating detection chip. The chip has minimal interference with the treatment angles, good noise immunity and the capability to easily penetrate a variety of materials. The simulation system consisting of linear actuators also successfully simulates the respiratory pattern of real patients., (Copyright © 2021 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.)

Background: The effectiveness of Gamma Knife radiosurgery (GKR) for cerebral arteriovenous malformations (AVMs) is predicated on inclusion of the entire nidus while excluding normal tissue. As such, GKR may be limited by the resolution and accuracy of the imaging modality used in targeting., Objective: We present the first case series to demonstrate the feasibility of using ultrahigh-resolution C-arm cone-beam computed tomography angiography (CBCT-A) in AVM targeting., Methods: From June 2009 to June 2013, CBCT-A was used for targeting of all patients with AVMs treated with GKR at our institution. Patients underwent Leksell stereotactic head frame placement followed by catheter-based biplane 2-dimensional digital subtraction angiography, 3-dimensional rotational angiography, as well as CBCT-A. The CBCT-A dataset was used for stereotactic planning for GKR. Patients were followed at 1, 3, 6, and 12 months and then annually thereafter., Results: CBCT-A-based targeting was used in 22 consecutive patients. CBCT-A provided detailed spatial resolution and sensitivity of nidal angioarchitecture enabling treatment. The average radiation dose to the margin of the AVM nidus corresponding to the 50% isodose line was 15.6 Gy. No patient had treatment-associated hemorrhage. At early follow-up (mean, 16 months), 84% of patients had a decreasing or obliterated AVM nidus., Conclusion: CBCT-A-guided radiosurgery is feasible and useful because it provides sufficient detailed resolution and sensitivity for imaging brain AVMs.

Background and Objective: To evaluate the effectiveness of Leksell Gamma Knife stereotactic radio-surgery (Elekta, Stockholm, Sweden) with respect to local tumor control, visual acuity, and radiation side effects for uveal melanoma., Patients and Methods: Retrospective, non-comparative case series of 23 patients with uveal melanoma treated with Gamma Knife stereotactic radiosurgery at Tufts Medical Center from 2000 to 2012. Patients received single-fraction stereotactic radiation therapy of 20-25 gray (Gy) (mean: 21.7 Gy), primarily at the 50% isodose line. Follow-up was 4 to 121 months (median: 41.5 months). Main outcome measures included local tumor control, metastasis, visual acuity, and complications of therapy., Results: In 21 of 23 patients (91%), local control was achieved with a single session of Gamma Knife therapy. Both patients who did not have local control, as well as a third patient (three of 23, 13%) developed liver metastases. Visual acuity was 20/200 or better in eight of 23 patients (35%) at last follow-up. Radiation side effects severe enough to cause vision loss were present in 14 of 23 patients (61%)., Conclusion: Gamma Knife therapy may be an effective alternative to enucleation in patients with uveal melanoma who are deemed less satisfactory candidates for brachytherapy or wish to avoid surgery., (Copyright 2014, SLACK Incorporated.)

Background: Stereotactic radiosurgery represents a noninvasive alternative treatment for intracranial metastases., Objective: To investigate the treatment outcome of linear accelerator-based stereotactic radiosurgery (linac-SRS) for brainstem metastases., Methods: We retrospectively reviewed our database of patients who were diagnosed with brainstem metastases and underwent linac-SRS between 1997 and 2008 at the University of California, Los Angeles., Results: A total of 45 patients with 48 brainstem metastases were treated. The median target volume was 0.40 mL (range, 0.02-5.70 mL), and median prescription dose was 14 Gy (range, 10-17 Gy) at 90% isodose curve. The median survival time was 11.6 months. Longer survival time was associated with higher Karnofsky performance status. The local control rate was 92% at 6 months and 88% at 1 year. Univariate analysis demonstrated a significant relationship between local control and tumor volume (≤0.4 mL vs >0.4 mL, P = .023) and SRS mode (conventional circular arc vs dynamic conformal arc, P = .044). There was a trend toward improved local control and prescription dose >14 Gy (P = .059). Two patients had brainstem complications following treatment, and the complication rate was 4.7% at 2 years. Serious morbidity occurred with 17 Gy., Conclusion: Linac-SRS using a median dose of 14 Gy provided excellent local control in patients with brainstem metastases less than 0.4 mL with relatively low serious morbidity. The results of the study support the use of linac-SRS for patients with brainstem metastases. We advocate 14 to 16 Gy, given the high local control rate and low complication rate with this dose.

Given the potential morbidity of whole brain radiation therapy (WBRT), there has been an increasing trend to defer WBRT and deliver Gamma Knife stereotactic radiosurgery (GKS) to cerebral metastatic lesions. We analyzed our experience delivering GKS to the tumor cavity following surgical resection of brain metastases and compared our results to patients receiving WBRT after surgical resection of a metastatic lesion. We performed a retrospective review of patients undergoing surgical resection of at least one brain metastasis between December 1999 and December 2008. Both univariate and multivariate Cox proportional hazards regression were utilized to analyze the influence of various prognostic factors on survival. Twenty-five patients had a metastatic lesion resected followed by adjuvant GKS to the resection cavity while another 18 had surgical resection followed by WBRT. Aside from a disparity in gender distribution (72% of GKS patients were female while women only constituted 28% of the WBRT group), no significant differences existed between groups. The median survival for patients receiving GKS was 15.00 months as compared to 6.81 months among those receiving WBRT (P = 0.08). Univariate Cox regression analysis identified the number of metastases (HR 1.65, 95% CI 1.07-2.54, P = 0.02) and regional recurrence (RR 5.23, 95% CI 1.78-15.38, P = 0.003) as poor prognostic factors. Multivariate regression analysis showed that regional recurrence (HR 5.17, 95% CI 1.69-15.78, P = 0.004) was again strongly associated with worse survival. Although limited by the retrospective nature of our study and lack of some clinical measures, patients undergoing GKS to the resection cavity had a trend towards longer median survival.

Object: Gamma Knife surgery (GKS) has been shown to be effective in treating trigeminal neuralgia (TN). Existing studies have demonstrated success rates of 69.1-85% with median follow-up intervals of 19-60 months. However, series with uniform long-term follow-up data for all patients have been lacking. In the present study the authors examined outcomes in a series of patients with TN who underwent a single GKS treatment followed by a minimum follow-up of 36 months. They used a clinical scale that simplifies the reporting of outcome data for patients with TN., Methods: Fifty-three consecutive patients with typical, intractable TN received a median maximum radiation dose of 80 Gy applied with a single 4-mm isocenter to the affected trigeminal nerve. Follow-up data were obtained by clinical examination and questionnaire. Outcome results were categorized into the following classes (in order of decreasing success): Class 1A, complete pain relief without medications; 1B, complete pain relief with either a decrease or no change in medications; 1C, > or = 50% pain relief without medications; 1D, > or = 50% pain relief with either a decrease or no change in medications; and Class 2, < 50% pain relief and/or increase in medications. Patients with Class 1A-1D outcome (equivalent to Barrow Neurological Institute Grades I-IIIb) were considered to have a good treatment outcome, whereas in patients with Class 2 outcome (equivalent to Barrow Neurological Institute Grades IV and V) treatment was considered to have failed., Results: A good treatment outcome from initial GKS was achieved in 31 (58.5%) patients for whom the mean follow-up period was 48 months (range 36-66 months). Outcomes at last follow-up were reflected by class status: Class 1A, 32.1% of patients; 1B, 1.9%; 1C, 3.8%; 1D, 20.8%; and Class 2, 41.5%. Statistical analysis showed no difference in outcomes between patients previously treated with microvascular decompression or rhizotomy compared with patients with no previous surgical treatments. Thirty-six percent of patients reported some degree of posttreatment facial numbness. Anesthesia dolorosa did not develop in any patient., Conclusions: Despite a time-dependent deterioration in the success rate of GKS for medically intractable TN, the authors' study showed that > 50% of patients can be expected to have a good outcome based on their scoring system, with approximately 33% having an ideal outcome (pain free with no need for medications). Long-term data, as those presented here, are important when counseling patients on their treatment options.

Purpose: Single-fraction targeted radiation therapy delivered by the Leksell Gamma Knife system is a minimally invasive treatment option for choroidal melanoma that has been used as an alternative to enucleation, proton beam therapy, or brachytherapy. Previously reported Gamma Knife series involved the treatment of choroidal melanomas with a dose of 40 to 50 Gy at the tumor margin. We report our institutional experience using a significantly lower dose., Methods and Materials: Fourteen patients with choroidal melanoma were treated with the Leksell Gamma Knife at our institution over a 7-year period. The treatment and clinical data were analyzed in a retrospective fashion after a mean follow-up of 32.2 months., Results: The mean dose to the tumor margin was 22.2 +/- 2.4 Gy (range, 20- 25 Gy). Mean treated tumor volume was 1.1 +/- 1.2 cc. Local control was achieved in 13 cases (93%). In 1 patient both intraocular spread and distant metastatic disease developed after treatment. Visual function of the affected eye was preserved in 5 patients (36%) at latest follow-up, in 9 patients (64%) visual loss ensued. Mild to moderate radiation toxicity developed in 8 patients., Conclusions: Choroidal melanoma can be safely and effectively treated using Leksell Gamma Knife stereotactic radiosurgery with a marginal dose of less than 25 Gy.

Object: Trigeminal neuralgia (TN) is a disorder of the trigeminal nerve that results in intense episodic pain. Primary treatment with Gamma Knife surgery (GKS) is well established; however, a significant number of patients experience recurrence of TN over time. Repeat GKS can be performed, but the retreatment dose has not been well established. In this study, the authors present their institutional retreatment results and compare them with other series., Methods: Between December 2003 and January 2006, 28 patients were treated at Tufts Medical Center with repeat GKS for recurrence of TN. All patients had been initially treated with GKS at this institution, and only those with significant pain improvement were offered retreatment. The maximum dose was prescribed using a single isocenter; the 4-mm collimator was used. The initial median GKS dose was 80 Gy, the median retreatment dose was 45 Gy, and the median cumulative dose was 125 Gy. The median time between GKS procedures was 18.1 months. Facial pain outcomes were defined using the Marseille scale. Excellent outcome was defined as no pain (with or without medications), and good outcome was defined as > 50% pain relief. Toxicity was categorized as none, mild, or bothersome. The median clinical follow-up after the second GKS was 19.7 months. Our clinical outcomes were compared with 8 previously reported retreatment series (including 1 abstract), both for rate of pain control and for rate of complications., Results: Outcomes after the second GKS were excellent in 29% (8 patients), good in 32% (9), and poor in 39% (11). Four patients (14%) experienced no improvement after repeat GKS. Eight patients (29%) experienced new trigeminal nerve dysfunction, including numbness (11%), paresthesia (14%), dysesthesia (4%), taste alteration (11%), and bite weakness (4%). None of these were bothersome. No patient developed corneal numbness. Univariate analysis failed to reveal any significant predictors of pain control or complications. Seven published peer-reviewed retreatment series and the authors' data (total 215 patients) were analyzed. There was a cumulative dose-response relationship for both pain control (p = 0.04) and new trigeminal dysfunction (p = 0.08). Successful pain control was strongly correlated with development of new dysfunction (p = 0.02). A cumulative dose > 130 Gy was more likely to result in successful (> 50%) pain control, but was also more likely (> 20%) to result in development of new dysfunction., Conclusions: Successful retreatment of patients in whom the initial GKS treatment fails is feasible. Patients who respond initially may be at a higher risk of retreatment-related complications. There appears to be a dose-response relationship for both pain control and development of new side effects. It is important to counsel and treat patients individually based on this dose-response relationship.

We analyzed our recent stereotactic radiosurgery (SRS) experience to determine the radiographic response of intracranial metastatic melanomas to SRS. Twelve patients with 21 intracranial melanoma metastases treated with SRS were evaluated. Fifteen (72%) metastases were hemispheric, 3 (14%) were cerebellar, and 3 (14%) were in the basal ganglion or thalamus. All lesions were 2.5 cm or less in maximum diameter. Eleven patients also had whole brain external beam radiotherapy. Mean SRS dosage was 1,800 cGy to the 85% isodose surface and median dose was 1,800 cGy to the 80% isodose surface (range 1,100-3, 100 cGy at the 80-95% isodose surface). Overall, 12 (57%) lesions showed decrease or stabilization of tumor volume (i.e., local control), while 9 (43%) showed enlargement. Division of metastases into small (< or = 1.0 cm diameter) and large (> 1.0 cm diameter) tumors showed that the small tumors were more likely to regress than the large tumors (chi-square test; P < 0.03). Only 1 of 9 (11%) large lesions regressed as opposed to 7 of 12 (58%) small lesions regressed with SRS. We conclude that SRS is suited for small melanoma brain metastases, but lesions between 1.0 and 2.5 cm in diameter, while still generally considered appropriate for SRS, may not be as responsive to SRS at currently employed dosages.