Frameless Radiosurgery Research Articles

CO-10. Salvage frameless radiosurgery as first treatment option for recurrent brain metastases. A single institution experience

CO-10. Salvage frameless radiosurgery as first treatment option for recurrent brain metastases. A single institution experience

182. Study of the accuracy of non-invasive fixation frames in brain treatments with Helical Tomotherapy

PurposeThe study focused on the accuracy of intracranial frame-less radiosurgery (RS) and intracranial hypo-fractionated treatments (HFT), delivered with helical Tomotherapy (HT), by means of two different mask-based fixation systems (FPM = Five Point Mask and DSPS = Double Shell Positioning System). MethodsA Megavoltage Computed Tomography (MVCT) was acquired and automatically registered with the planning CT of a Rando phantom, to evaluate the delivery accuracy of the HT image guided positioning tool. After the application of the suggested shifts, the phantom was scanned a second time and shifts in each direction and rotations were recorded; the vector displacement (v) was calculated as the square sum of the shifts in each directions. Analogous procedure was applied to 14 and 16 patients underwent intracranial HFT and RS respectively: overall 59 MVCT performed at the end of the treatment were acquired and analyzed. The v were analyzed in order to evaluate the intra-fraction motions. ResultsThe mean v, obtained in the phantom acquisitions, was 0.4 ± 0.2 mm, showing that HT-IGRT system is able to achieve positioning accuracy typical of RS (v<1mm). Moreover, the mean rotational variations were negligible. Results on the patient treatments, reported in Table 1, showed that both masks minimized the intra-fraction motion to an extent of 1 mm (with no statistically difference between FPM and DSPS: p < 0.573, Mann-Whitney Test). No dependence of v on the treatment time was observed. ConclusionsOur study demonstrates that mask-based fixation systems have a high intracranial positioning accuracy, comparable with for invasive immobilization systems (v = 0.6 ± 0.9 mm (range: 0.3–1.7 mm) [1]), therefore, they could be used for high-precision treatments, like RS. [Display omitted]

Comparison of Skull Motions in Six Degrees of Freedom Between Two Head Supports During Frameless Radiosurgery by CyberKnife.

Introduction: Maintaining immobilization to minimize skull motion is important during frameless radiosurgery. This study aimed to compare the intrafractional skull motions between two head supports.Methods: With 6D skull tracking system, 4,075 image records from 45 patients receiving radiosurgery by CyberKnife were obtained. Twenty-three patients used TIMO head supports (CIVCO) (Group A) and twenty-two patients used Silverman head supports (CIVCO) with MoldCare cushions (ALCARE) (Group B). The skull motions in X (superior-inferior), Y (right-left), Z (anterior-posterior) axes, 3D (three-dimensional) vector, Roll, Pitch and Yaw between the two groups were compared and the margins of planning target volume were estimated.Results: The translational motions in Group A were similar in three axes at initial but became different after 10 min, and those in Group B were less prominent in the Y axis. The rotational errors in Group A were most obvious in Yaw, but those in Group B were stationary in three axes. The motions in the X axis, 3D vector, Pitch and Yaw in Group B were significantly smaller than those in Group A; conversely, the motions in the Z axis in Group B were larger. To cover the 95% confidence intervals, margins of 0.77, 0.79, and 0.40 mm in the X, Y, and Z axes, respectively, were needed in Group A, and 0.69, 0.50, and 0.51 mm were needed in Group B.Conclusions: Both head supports could provide good immobilization during the frameless radiosurgery. Silverman head support with MoldCare cushion was better than TIMO head support in the superior-inferior direction, 3D vector, Pitch and Yaw axes, but worse in the anterior-posterior direction.

Clinical outcomes of perioptic tumors treated with hypofractionated stereotactic radiotherapy using CyberKnife® stereotactic radiosurgery.

Stereotactic radiation technique is widely reported as an effective treatment for various types of benign intracranial tumors. However, single fraction radiosurgery (SRS) is not recommended for tumors located close to the optic apparatus due to the restricted radiation tolerance dose of the optic pathway. Recent advances in radiotherapy include advanced frameless radiosurgery using hypofractionated stereotactic radiotherapy (HSRT), and this has become an attractive treatment option for perioptic tumors within 2-3mm of the optic pathway. Accordingly, the aim of this study was to investigate the clinical outcomes of perioptic tumors treated with HSRT using CyberKnife® (CK) robotic radiosurgery system relative to tumor control, vision preservation and toxicity. This retrospective analysis of prospectively collected data included consecutive 100 patients that were diagnosed with and treated for perioptic tumor at the Radiosurgery center, Ramathibodi Hospital during the January 2009 to December 2012 study period. The median tumor volume was 6.81cm3 (range 0.37-51.6), and the median prescribed dose was 25Gy (range 20-35) in 5 fractions (range 3-5). After the median follow-up time of 37.5months (range 21-103), two patients developed tumor progression at 6 and 34months post-HSRT. The 5-year overall survival was 97%, and the 5-year local control was 97.5%. At the last follow-up, no vision deterioration or newly developed hypopituitarism was detected in our study. Although a longer follow-up is needed, HSRT yields a high level of local control and vision preservation, and should be considered a treatment of choice for perioptic tumor located close to the optic apparatus.

EP-2034: Capacitive monitoring system for intra-fraction motion detection during frameless radiosurgery

EP-2034: Capacitive monitoring system for intra-fraction motion detection during frameless radiosurgery

Local control and overall survival after frameless radiosurgery: A single center experience

IntroductionStereotactic radiosurgery (SRS) has been increasingly advocated for 1–3 small brain metastases. The goal of this study was to evaluate the clinical results in patients with brain metastases treated with LINAC-based SRS using a thermoplastic mask (non-invasive fixation system) and Image-Guided Radiotherapy (IGRT). Material and MethodsIn this single-institution study 48 patients with 77 brain metastases were treated between February 2012 and January 2014. The prescribed dose was 20 Gy or 18 Gy as a single fraction. SRS was performed with a True Beam STX Novalis Radiosurgery LINAC (Varian Medical Systems). The verification of positioning was done using the BrainLAB ExacTrac ® X-ray 6D system and cone-beam CT. ResultsIn 69 of 77 treated brain metastases (90%) the follow-up was documented on MR imaging performed every 3 months. Mean follow-up time was 10.86 months. Estimated 1-year local control was 83%, using the Kaplan-Meier method. In 7/69 brain metastases (10%) local failure (LF) was diagnosed. Median progression free survival (PFS) was 3.73 months, largely due to distant brain relapse. A GTV of ≤2.0 cm3 was significantly associated with a better PFS than a GTV >2.0 cm3. Extracranial stable disease and GTV ≤2.5 cm³ were significant predictors of OS.We observed 2 cases of radiation necrosis diagnosed by histology after surgical resection. No other cases of severe side effects (CTACE ≥ 3) were observed. ConclusionLINAC-based frameless SRS with the BrainLAB Mask using the BrainLAB ExacTrac ® X-ray 6D system for patient positioning is well tolerated, safe and leads to favorable crude local control of 90%. In our experience, local control after frameless (ringless) SRS is as good as ring-based SRS reported in literature. Without invasive head fixation, radiotherapy is more comfortable for patients.

Clinical Outcomes of a Multileaf Collimator-Based Frameless Robotic Radiosurgery System for Spine Stereotactic Body Radiation Therapy

Clinical Outcomes of a Multileaf Collimator-Based Frameless Robotic Radiosurgery System for Spine Stereotactic Body Radiation Therapy

Practical considerations of linear accelerator-based frameless extracranial radiosurgery for treatment of occipital neuralgia for nonsurgical candidates.

Occipital neuralgia generally responds to medical or invasive procedures. Repeated invasive procedures generate increasing complications and are often contraindicated. Stereotactic radiosurgery (SRS) has not been reported as a treatment option largely due to the extracranial nature of the target as opposed to the similar, more established trigeminal neuralgia. A dedicated phantom study was conducted to determine the optimum imaging studies, fusion matrices, and treatment planning parameters to target the C2 dorsal root ganglion which forms the occipital nerve. The conditions created from the phantom were applied to a patient with medically and surgically refractory occipital neuralgia. A dose of 80 Gy in one fraction was prescribed to the C2 occipital dorsal root ganglion. The phantom study resulted in a treatment achieved with an average translational magnitude of correction of 1.35 mm with an acceptable tolerance of 0.5 mm and an average rotational magnitude of correction of 0.4° with an acceptable tolerance of 1.0°. For the patient, the spinal cord was 12.0 mm at its closest distance to the isocenter and received a maximum dose of 3.36 Gy, a dose to 0.35 cc of 1.84 Gy, and a dose to 1.2 cc of 0.79 Gy. The brain maximum dose was 2.20 Gy. Treatment time was 59 min for 18, 323 MUs. Imaging was performed prior to each arc delivery resulting in 21 imaging sessions. The average deviation magnitude requiring a positional or rotational correction was 0.96 ± 0.25 mm, 0.8 ± 0.41°, whereas the average deviation magnitude deemed within tolerance was 0.41 ± 0.12 mm, 0.57 ± 0.28°. Dedicated quality assurance of the treatment planning and delivery is necessary for safe and accurate SRS to the cervical spine dorsal root ganglion. With additional prospective study, linear accelerator‐based frameless radiosurgery can provide an accurate, noninvasive alternative for treating occipital neuralgia where an invasive procedure is contraindicated.

EP-1106: Local control and overall survival after frameless radiosurgery

EP-1106: Local control and overall survival after frameless radiosurgery

EP-1636: Evaluation of the accuracy in frame-less image-guided radiotherapy and radiosurgery

EP-1636: Evaluation of the accuracy in frame-less image-guided radiotherapy and radiosurgery

EP-1578: Frameless intracranial radiosurgery with Helical Tomotherapy: preliminary results

EP-1578: Frameless intracranial radiosurgery with Helical Tomotherapy: preliminary results

Frameless Stereotactic Radiosurgery for Treatment of Multiple Sclerosis-Related Trigeminal Neuralgia.

Trigeminal neuralgia (TN) affects 7% of patients with multiple sclerosis (MS). In such patients, TN is difficult to manage either pharmacologically and surgically. Radiosurgical rhizotomy is an effective treatment option. The nonisocentric geometry of radiation beams of CyberKnife introduces new concepts in the treatment of TN. Its efficacy for MS-related TN has not yet been demonstrated. Twenty-seven patients with refractory TN and MS were treated. A nonisocentric beams distribution was chosen; the maximal target dose was 72.5 Gy. The maximal dose to the brainstem was <12 Gy. Effects on pain, medications, sensory disturbance, rate, and time of pain recurrence were analyzed. Median follow-up was 37 (18-72) months. Barrow Neurological Institute pain scale score I-III was achieved in 23/27 patients (85%) within 45 days. Prescription isodose line (80%) accounting for a dose of 58 Gy incorporated an average of 4.85 mm (4-6 mm) of the nerve and mean nerve volume of 26.4 mm3 (range 20-38 mm3). Seven out of 27 patients (26%) had mild, not bothersome, facial numbness (Barrow Neurological Institute numbness score II). The rate of pain control decreased progressively after the first year, and only 44% of patients retained pain control 4 years later. Frameless radiosurgery can be effectively used to perform retrogasserian rhizotomy. Pain relief was satisfactory and, with our dose/volume constraints, no sensory complications were recorded. Nonetheless, long-term pain control was possible in less than half of the patients. This is a limitation that CyberKnife radiosurgery shares with other techniques in MS patients.

Radiosurgery for Arteriovenous Malformations Using Micro–Multi-leaf Collimators: Analyses of Outcome

Aim To assess the outcome of patients with AVMs treated using micro-MLC–based radiosurgery at Regional Cancer Centre (RCC), Thiruvananthapuram. Materials and Methods During January 1 to December 31, 2012, 24 patients were treated with stereotactic radiosurgery (SRS) at RCC. The median age was 28 years (range: 8–58 years). There were 11 males and 13 females. Fifteen patients had prior embolization. All patients were treated with a frameless radiosurgery system using micro-MLC–based linear accelerator (LINAC). Obliteration of the lesion was assessed with either magnetic resonance angiogram (MRA) or digital subtraction angiography (DSA). Results Nineteen patients who underwent an assessment procedure were evaluable for this study. At median follow-up of 12 months, nearly two-thirds of patients had complete obliteration of the AVM and the rest had partial obliteration. Among patients with complete obliteration, seven patients had an AVM volume of ≤ 3 cc and three-fourths of the patients had AVM score of &lt; 1.5. Further, marginal dose of &gt; 18 Gy resulted in higher obliteration. One patient had an episode of seizure after SRS. No complications or bleed was seen in any of the patients after treatment. Conclusion Our experience correlates with the existing literature reports, without any significant complications. Longer follow-up is required to assess the complete obliteration and late complications.

P14.20 Local control an overall survival after frameless LINAC radiosurgery: a single center experience

Abstract Introduction: Stereotactic radiosurgery (SRS) has been increasingly advocated for 1-3 small brain metastases. Goal of this study was to evaluate the clinical results in patients with brain metastases treated with SRS using a thermoplastic mask non-invasive fixation system and image-guided treatment. MATERIAL AND METHODS: In this single-institution study 48 patients with 77 brain metastases were treated between February 2012 and January 2014. The head fixation was realized using a BrainLAB thermoplastic mask. The prescribed dose was 20 Gy or 18 Gy as a single dose. The SRS were performed with a True Beam STX Novalis Radiosurgery LINAC (Varian Medical Systems). The verification of positioning was done using the BrainLAB ExacTrac ® X-ray 6D system and cone-beam CT. Results: In 69 of 77 (89.6%) treated brain metastases the follow-up was documented on MR imaging performed every 3 months. In 7/69 (10.1%) brain metastases local failure was diagnosed with a mean follow-up time of 10.7 months (range 1-43 months). Estimated 1-year local control was 83.1%. Median progression free survival (PFS) was 3.7 months, largely due to distant brain relapse. A GTV of ≤ 2.0 cm3 was significantly associated with a better PFS than a GTV > 2.0 cm3. We observed 2 cases of radiation necrosis diagnosed by histology after surgical resection. No other cases of severe side effects (CTACE≥3) were observed. CONCLUSION: In our experience local control after frameless (ringless) LINAC based SRS with mean follow-up of 10.7 months is 89.9%. Without the invasive head fixation radiotherapy is more comfortable for the patients.

Evaluation of positioning uncertainty for frameless radiosurgery for three IGRT methods with a head phantom

Introduction A BRAINLAB system for frameless radiosurgery is commissioned obtaining patient positioning accuracy with the STEEV head phantom (CIRS). Purpose Firstly the position accuracy for frameless radiosurgery has been compared with three different IGRT methods: EXACTRAC (BRANLAB), OBI-2D (VARIAN) and CBCT (VARIAN) with EXACTRAC registration. Secondly the uncertainty of image registration between MRI (PHILIPS INGENIA SYSTEMS 3.0T) and CT (PHILIPS BIG BORE) has been evaluated with IPLANRT image 4.1.1 software. Materials and methods Phantom positioning was done with automatic registration and with equivalent X-ray parameters for the three IGRT methods. Measurement was done 5 times, every of these the phantom with mask was replaced. Position accuracy was evaluated with the tool “detect Winston-Lutz pointer” from EXACTRAC. CT and MRI images of a multimodality fillable sphere insert in the phantom were registered. The registration was evaluated with IPLANRT image software finding the center of the sphere in each modality. Results For the three IGRT techniques the accuracy obtained was (0.466 ± 0.071)mm for EXACTRAC, (0.744 ± 0.209)mm for OBI-2D and (0.750 ± 0.386)mm for CBCT registered with EXACTRAC. For MRI was obtained (0.300 ± 0.1)mm. The total uncertainty for EXACTRACT IGRT system is (0.554 ± 0.374)mm (k = 2). Conclusions • The positioning system EXACTRAC have less uncertainty than both OBI-2D and CBCT registered with EXACTRAC for cranial SRS. • The total uncertainty for the EXACTRAC including IGRT and also image registration between CT and MRI is (0.554 ± 0.374)mm.

Margin of error for a frameless image guided radiosurgery system: Direct confirmation based on posttreatment MRI scans

PurposeTo report on radiosurgery delivery positioning accuracy in the treatment of tremor patients with frameless image guided radiosurgery using the linear accelerator (LINAC) based ExacTrac system and to describe quality assurance (QA) procedures used. Methods and materialsBetween 2010 and 2015, 20 patients underwent radiosurgical thalamotomy targeting the ventral intermediate nucleus for the treatment of severe tremor. The median prescription dose was 140 Gy (range, 120-145 Gy) in a single fraction. The median maximum dose was 156 Gy (range, 136-162 Gy). All treatment planning was performed with the iPlan system using a 4-mm circular cone with multiple arcs. Before each treatment, QA procedures were performed, including the imaging system. As a result of the extremely high dose delivered in a single fraction, a well-defined circular mark developed on the posttreatment magnetic resonance imaging (MRI). Eight of these 20 patients were selected to evaluate treatment localization errors because their circular marks were available in posttreatment MRI. In this study, the localization error is defined as the distance between the center of the intended target and the center of the posttreatment mark. ResultsThe mean error of distance was found to be 1.1 mm (range, 0.4-1.5 mm). The mean errors for the left-right, anteroposterior, and superoinferior directions are 0.5 mm, 0.6 mm, and 0.7 mm, respectively. ConclusionsThe result reported in this study includes all tremor patients treated at our institution when their posttreatment MRI data were available for study. It represents a direct confirmation of target positioning accuracy in radiosurgery with a LINAC-based frameless system and its limitations. This level of accuracy is only achievable with an appropriate QA program in place for a LINAC-based frameless radiosurgery system.

Poster ‐ 44: Development and implementation of a comprehensive end‐to‐end testing methodology for linac‐based frameless SRS QA using a modified commercial stereotactic anthropomorphic phantom

Purpose:An end‐to‐end testing methodology was designed to evaluate the overall SRS treatment fidelity, incorporating all steps in the linac‐based frameless radiosurgery treatment delivery process. The study details our commissioning experience of the Steev (CIRS, Norfolk, VA) stereotactic anthropomorphic head phantom including modification, test design, and baseline measurements.Methods:Repeated MR and CT scans were performed with interchanging inserts. MR‐CT fusion accuracy was evaluated and the insert spatial coincidence was verified on CT. Five non‐coplanar arcs delivered a prescription dose to a 15 mm spherical CTV with 2 mm PTV margin.Following setup, CBCT‐based shifts were applied as per protocol. Sequential measurements were performed by interchanging inserts without disturbing the setup. Spatial and dosimetric accuracy was assessed by a combination of CBCT hidden target, radiochromic film, and ion chamber measurements. To facilitate film registration, the film insert was modified in‐house by etching marks.Results:MR fusion error and insert spatial coincidences were within 0.3 mm. Both CBCT and film measurements showed spatial displacements of 1.0 mm in similar directions. Both coronal and sagittal films reported 2.3 % higher target dose relative to the treatment plan. The corrected ion chamber measurement was similarly greater by 1.0 %. The 3 %/2 mm gamma pass rate was 99% for both filmsConclusions:A comprehensive end‐to‐end testing methodology was implemented for our SRS QA program. The Steev phantom enabled realistic evaluation of the entire treatment process. Overall spatial and dosimetric accuracy of the delivery were 1 mm and 3 % respectively.

SU‐F‐T‐631: Linear Accelerator‐Based Frameless Extracranial Radiosurgery for Treatment of Occipital Neuralgia for Non‐Surgical Candidates

Purpose:Occipital neuralgia is a condition wherein pain is transmitted by the occipital nerves. Non‐invasive therapies generally alleviate symptoms; however, persistent or recurring pain may require invasive procedures. Repeated invasive procedures upon failure are considered higher risk and are often contraindicated due to compounding inherent risk. SRS has not been explored as a treatment option largely due to the extracranial nature of the target (as opposed to the similar, more established trigeminal neuralgia), but advances in linear‐accelerator frameless‐based SRS now present an opportunity to evaluate the novel potential of this modality for this application.Methods:Patient presented with severe occipital pain following decompression and fusion of the cervical vertebrae with prior intervention attempted via radiofrequency ablation yielding temporary pain cessation. A 0.6 mm slice spacing CT was obtained for treatment planning, and a cervical spine oriented 1.0 mm slice spacing CT myelogram was obtained for the purpose of defining the targeted C2 occipital dorsal root ganglion (to receive 80 Gy to the isocenter) and spinal cord.Results:The spinal cord was most proximally 12.0 mm from the isocenter receiving a maximum dose of 3.36 Gy, and doses to 0.35 and 1.2 cc of 1.84 Gy and 0.79 Gy, respectively. The brain maximum dose was 2.29 Gy. The treatment was successfully performed with a NovalisTX (Varian) equipped with ExacTrac stereoscopic x‐ray image guidance (BrainLAB). Treatment time was 59 minutes for 18,323 MUs. Imaging was performed prior to each arc delivery resulting in twenty‐one imaging sessions (twelve requiring positional corrections with the remaining verified within tolerance). The average deviation magnitude requiring a positional or rotational correction was 0.96±0.25 mm, 0.8±0.41° while the average deviation magnitude deemed within tolerance was 0.41±0.12 mm, 0.57±0.28°.Conclusion:Linear accelerator‐based frameless radiosurgery provides an accurate, non‐invasive alternative for treating occipital neuralgia where an invasive procedure is contraindicated.

Frameless single robotic radiosurgery of pulmonary metastases in colorectal cancer patients.

e15147Background: Metastases due to colorectal cancer are a rising problem, since modern therapy allows for long term survival. Surgical intervention and radiation therapy are the most common appro...

Re-irradiation of Recurrent Pineal Germ Cell Tumors with Radiosurgery: Report of Two Cases and Review of Literature.

Primary intracranial germ cell tumors are rare, representing less than 5% of all central nervous system tumors. Overall, the majority of germ cell tumors are germinomas and approximately one-third are non-germinomatous germ cell tumors (NGGCT), which include teratoma, embryonal carcinoma, yolk sac tumor (endodermal sinus tumor), choriocarcinoma, or mixed malignant germ cell tumor. Germ cell tumors may secrete detectable levels of proteins into the blood and/or cerebrospinal fluid, and these proteins can be used for diagnostic purposes or to monitor tumor recurrence. Germinomas have long been known to be highly curable with radiation therapy alone. However, many late effects of whole brain or craniospinal irradiation have been well documented. Strategies have been developed to reduce the dose and volume of radiation therapy, often in combination with chemotherapy. In contrast, patients with NGGCT have a poorer prognosis, with about 60% cured with multimodality chemoradiation. There are no standard approaches for relapsed germ cell tumors. Options may be limited by prior treatment. Radiation therapy has been utilized alone or in combination with chemotherapy or high-dose chemotherapy and transplant. We discuss two cases and review options for frameless radiosurgery or fractionated radiotherapy.