Frameless Radiosurgery Research Articles

PO-0884: Frameless radiosurgery: less invasive, more accurate

PO-0884: Frameless radiosurgery: less invasive, more accurate

EP-1249: Evaluation of the clinical usefulness for using verification images during frameless radiosurgery

EP-1249: Evaluation of the clinical usefulness for using verification images during frameless radiosurgery

Clinical outcomes for a novel 6 degrees of freedom image guided localization method for frameless radiosurgery for intracranial brain metastases

Stereotactic radiosurgery (SRS) is an accepted method of treatment for intracranial brain metastases with sub-millimeter accuracy. Frameless radiosurgery (FRS) is becoming an alternative to framed SRS due to its less invasive requirements. The purpose of this study is to describe the clinical outcomes and local patterns of failure for a novel 6 degrees of freedom CT guided method of localization for FRS of intracranial brain metastases. 42 patients underwent linear accelerator-based FRS to 94 intracranial brain metastases between 01/2009 and 07/2011. 78 and 22 % of treated sites were intact metastases and resection cavities, respectively. 55 % of patients had undergone prior brain radiotherapy (45 % SRS, 26 % whole brain radiation therapy). The 1 year actuarial local recurrence rate was 18 %, with a median imaging follow-up period of 13.2 months. Single fraction equivalent dose was the most important predictor of local recurrence. The 1 year actuarial first distant brain recurrence and total intracranial recurrence rate was 58 and 69 %, respectively. The crude radiographic radiation necrosis rate was 3 %. Of the 10 local recurrence events, 8 (80 %) were in-field only, 1 (10 %) was marginal only, and 1 (10 %) was both. The preponderance of in-field only patterns of failure suggests that geographic miss is not a major contributor to local recurrence using this novel localization method for FRS. The 1 year local control rate is comparable to other similar published series of framed and frameless radiosurgery.

Frame-based radiosurgery: Is it relevant in the era of IGRT?

To assess the setup errors and intrafraction motion in patients treated with frame-based and frameless stereotactic radiosurgery (SRS). Ten patients treated with frame-based and six patients treated with frameless radiosurgery were prospectively enrolled in the study. Leksell frame was used for frame-based and a customized uniframe orfit cast for frameless techniques. Cone beam computed tomography (CBCT) scans were taken immediately before and after each treatment to evaluate the positional accuracy and corrections applied with the use of hexapod couch for both groups. The mean translational shifts with frame-based SRS were 1.00 ± 0.30 mm in the lateral direction (X), 0.20 ± 1.20 mm in craniocaudal direction (Y) and -0.10 ± 0.31 mm in the anteroposterior direction (Z). The rotational shifts for frame-based treatments were as follows: roll 0.32 ± 0.70, pitch 0.44 ± 0.66 and yaw 0.20 ± 0.4. For frameless SRS, translational shifts were -0.40 ± 0.90, 1.10 ± 1.10, and 0.50 ± 1.30 mm in X, Y, and Z directions, respectively, and rotational shifts were -0.11 ± 0.78, 0.20 ± 0.44, and 0.29 ± 0.35 in roll, pitch, and yaw, respectively. Intrafraction shifts with frame-based SRS were: X = 0.60 ± 1.80 mm, Y = 0.20 ± 0.60 mm, and Z = 0.00 ± 0.05 mm; and rotational shifts were: roll 0.01 ± 0.27, pitch 0.06 ± 0.15, and yaw 0.01 ± 0.09. For frameless SRS, these were: X = 0.11 ± 0.20 mm, Y = 0.20 ± 0.40 mm, and Z = 0.20 ± 0.20 mm and rotational shifts were: roll 0.09 ± 0.23, pitch 0.00 ± 0.12, and yaw 0.00 ± 0.09. In our experience, set up accuracy of frameless SRS is as good as frame-based SRS. With availability of verification methods such as CBCT and hexapod couch, an accurate and precise treatment delivery is feasible with frameless techniques.

Six degrees of freedom CBCT‐based positioning for intracranial targets treated with frameless stereotactic radiosurgery

Frameless radiosurgery is an attractive alternative to the framed procedure if it can be performed with comparable precision in a reasonable time frame. Here, we present a positioning approach for frameless radiosurgery based on in‐room volumetric imaging coupled with an advanced six‐degrees‐of‐freedom (6 DOF) image registration technique which avoids use of a bite block. Patient motion is restricted with a custom thermoplastic mask. Accurate positioning is achieved by registering a cone‐beam CT to the planning CT scan and applying all translational and rotational shifts using a custom couch mount. System accuracy was initially verified on an anthropomorphic phantom. Isocenters of delineated targets in the phantom were computed and aligned by our system with an average accuracy of 0.2 mm, 0.3 mm, and 0.4 mm in the lateral, vertical, and longitudinal directions, respectively. The accuracy in the rotational directions was 0.1°, 0.2°, and 0.1° in the pitch, roll, and yaw, respectively. An additional test was performed using the phantom in which known shifts were introduced. Misalignments up to 10 mm and 3° in all directions/rotations were introduced in our phantom and recovered to an ideal alignment within 0.2 mm, 0.3 mm, and 0.4 mm in the lateral, vertical, and longitudinal directions, respectively, and within 0.3° in any rotational axis. These values are less than couch motion precision. Our first 28 patients with 38 targets treated over 63 fractions are analyzed in the patient positioning phase of the study. Mean error in the shifts predicted by the system were less than 0.5 mm in any translational direction and less than 0.3° in any rotation, as assessed by a confirmation CBCT scan. We conclude that accurate and efficient frameless radiosurgery positioning is achievable without the need for a bite block by using our 6 DOF registration method. This system is inexpensive compared to a couch‐based 6 DOF system, improves patient comfort compared to systems that utilize a bite block, and is ideal for the treatment of pediatric patients with or without general anesthesia, as well as of patients with dental issues. From this study, it is clear that only adjusting for 4 DOF may, in some cases, lead to significant compromise in PTV coverage. Since performing the additional match with 6 DOF in our registration system only adds a relatively short amount of time to the overall process, we advocate making the precise match in all cases.PACS number: 87.55.tm; 87.55.Qr; 87.57.nj

Clinical Outcomes for a Novel 6 Degrees of Freedom Image Guided Immobilization and Localization Method for Frameless Radiosurgery for Brain Metastases

Clinical Outcomes for a Novel 6 Degrees of Freedom Image Guided Immobilization and Localization Method for Frameless Radiosurgery for Brain Metastases

Evaluation of the clinical usefulness for using verification images during frameless radiosurgery

Evaluation of the clinical usefulness for using verification images during frameless radiosurgery

Comparison of fractionated and single session radiosurgery for radiation resistant brain metastases.

2091 Background: Melanoma and renal cell carcinoma are commonly called radiation resistant tumors due to the decreased response rate to traditional radiation (1.8-2 Gy /Fraction). Large brain metastases from radioresistant primaries are clinical challenges. This study examines the impact of fractionation on the treatment of intracranial metastases from radiation resistant tumors. Methods: Patients with a primary diagnosis of melanoma or renal cell carcinoma and intracranial metastases who completed treatment at The University of North Carolina with frameless robotic radiosurgery between 2007-2011 were retrospectively analyzed. Patients were treated with either single or 3-5 fractions depending on volume. The study’s primary endpoints were overall survival (OS) and local control (LC), and its secondary endpoint was patient steroid requirements. Outcomes data and pre-treatment variables were analyzed for significance using appropriate non-parametric tests. Results: 25 patients were included in the single fraction arm and 13 patients in the multi-fraction arm, and both had equivalent pre-treatment characteristics with the exception of tumor volume which was larger in the multi-fraction arm (p=0.01). At a median follow-up of 4.7 months (range, 1.8-11.6), the median OS for all patients was 6.2 months. One year survival was 35.1% and 5 patients (13%) had local failures at a median time to local failure of 5.5 months. Patients in the multi-fraction arm failed at a higher rate (10.5%) than patients in the single fraction arm (2.6%) (p=0.04), but there was no difference in OS (p=0.34). There was no difference between pre-treatment and post-treatment steroid requirements between the two arms (p=0.351). Conclusions: Fractionation is intended to facilitate radiosurgery in large tumors by limiting high doses of radiation to a large portion of normal brain. In our study of radioresistant intracranial metastases, large tumors receiving multi-fraction radiosurgery had decreased local control with no difference in toxicity or OS. These results suggest a need for either dose escalation, or combination therapy designed to reduce tumor size (resection or aspiration) in order to facilitate single fraction treatment.

Clinical Evaluation of a Robotic 6-Degree of Freedom Treatment Couch for Frameless Radiosurgery

To evaluate the added value of 6-degree of freedom (DOF) patient positioning with a robotic couch compared with 4DOF positioning for intracranial lesions and to estimate the immobilization characteristics of the BrainLAB frameless mask (BrainLAB AG, Feldkirchen, Germany), more specifically, the setup errors and intrafraction motion. We enrolled 40 patients with 66 brain metastases treated with frameless stereotactic radiosurgery and a 6DOF robotic couch. Patient positioning was performed with the BrainLAB ExacTrac stereoscopic X-ray system. Positioning results were collected before and after treatment to assess patient setup error and intrafraction motion. Existing treatment planning data were loaded and simulated for 4DOF positioning and compared with the 6DOF positioning. The clinical relevance was analyzed by means of the Paddick conformity index and the ratio of prescribed isodose volume covered with 4DOF to that obtained with the 6DOF positioning. The mean three-dimensional setup error before 6DOF correction was 1.91 mm (SD, 1.25 mm). The rotational errors were larger in the longitudinal (mean, 0.23°; SD, 0.82°) direction compared with the lateral (mean, -0.09°; SD, 0.72°) and vertical (mean, -0.10°; SD, 1.03°) directions (p < 0.05). The mean three-dimensional intrafraction shift was 0.58 mm (SD, 0.42 mm). The mean intrafractional rotational errors were comparable for the vertical, longitudinal, and lateral directions: 0.01° (SD, 0.35°), 0.03° (SD, 0.31°), and -0.03° (SD, 0.33°), respectively. The mean conformity index decreased from 0.68 (SD, 0.08) (6DOF) to 0.59 (SD, 0.12) (4DOF) (p < 0.05). A loss of prescribed isodose coverage of 5% (SD, 0.08) was found with the 4DOF positioning (p < 0.05). Half a degree for longitudinal and lateral rotations can be identified as a threshold for coverage loss. With a mask immobilization, patient setup error and intrafraction motions need to be evaluated and corrected for. The 6DOF patient positioning with a 6DOF robotic couch to correct translational and rotational setup errors improves target positioning with respect to treatment isocenter, which is in direct relation with the clinical outcome, compared with the 4DOF positioning.

2051 POSTER Feasibility of Frameless Cranial Radiosurgery With Infrared Markers Fixed to an Immobilization Mask That is Monitored Under X-ray and Infrared Image Guidance System

2051 POSTER Feasibility of Frameless Cranial Radiosurgery With Infrared Markers Fixed to an Immobilization Mask That is Monitored Under X-ray and Infrared Image Guidance System

2061 POSTER Clinical Evaluation of 6 Degree-of-freedom X-ray Image-guidance Fusion Algorithm and Robotic Positioning System for Frameless Cranial Radiosurgery

2061 POSTER Clinical Evaluation of 6 Degree-of-freedom X-ray Image-guidance Fusion Algorithm and Robotic Positioning System for Frameless Cranial Radiosurgery

SU‐E‐J‐136: Clinical Evaluation of a Robotic 6‐Degree of Freedom Treatment Couch for Frameless Radiosurgery

Purpose: To evaluate the added value of 6 degree‐of‐freedom (DOF) patient positioning with robotic couch compared to 4DOF positioning for intracranial lesions and to estimate the immobilization characteristics of the Brainlab frameless mask, more specifically the setup errors and the intrafraction motion. Methods: Forty patients with 66 brain metastases treated with frameless stereotactic radiosurgery and 6DOF robotic couch were enrolled. Patient positioning was performed with the Brainlab ExacTrac stereoscopic x‐ray system. Positioning results were collected before and after treatment to assess patient setup error and intrafraction motion. Existing treatment plannings were loaded and simulated for 4DOF positioning and compared to the 6DOF positioning. The clinical relevance was analyzed by means of the Paddick conformity index (CI) and the ratio of prescribed isodose volume covered with 4DOF to that obtained with the 6DOF positioning. Results: Results. The mean 3D setup error before 6DOF correction was 1.91 mm (SD1.25mm). The rotational errors were larger in the longitudinal (0.23° SD0.82°) direction compared to the lateral (−0.09° SD0.72°) and vertical (−0.10° SD1.03°) ones (p&lt;0.05). The mean 3D intrafraction shift was 0.58 (SD0.42mm). The intrafractional rotational errors were comparable,0.01° (SD0.35°), 0.03° (SD0.31°), −0.03° (SD0.33°), for the vertical, longitudinal and lateral, respectively. The mean CI decreased from 0.68 (SD 0.08) (6DOF) to 0.59 (SD 0.12) (4DOF) (p&lt;0.05). A loss of prescribed isodose coverage of 5% (SD0.08) was found with the 4DOF positioning (p&lt;0.05). Half a degree for longitudinal and lateral rotations can be identified as a threshold for coverage loss. Conclusions: With a mask immobilization, patient setup error and intrafraction motions need to be evaluated and corrected for. The 6DOF patient positioning with 6DOF robotic couch to correct translational and rotational setup errors improves target positioning with respect to treatment isocenter, which is in direct relation with the clinical outcome, compared to 4DOF positioning.

Setup Accuracy of the Novalis ExacTrac 6DOF System for Frameless Radiosurgery

Stereotactic radiosurgery using frame-based positioning is a well-established technique for the treatment of benign and malignant lesions. By contrast, a new trend toward frameless systems using image-guided positioning techniques is gaining mainstream acceptance. This study was designed to measure the detection and positioning accuracy of the ExacTrac/Novalis Body (ET/NB) for rotations and to compare the accuracy of the frameless with the frame-based radiosurgery technique. A program was developed in house to rotate reference computed tomography images. The angles measured by the system were compared with the known rotations. The accuracy of ET/NB was evaluated with a head phantom with seven lead beads inserted, mounted on a treatment couch equipped with a robotic tilt module, and was measured with a digital water level and portal films. Multiple hidden target tests (HTT) were performed to measure the overall accuracy of the different positioning techniques for radiosurgery (i.e., frameless and frame-based with relocatable mask or invasive ring, respectively). The ET/NB system can detect rotational setup errors with an average accuracy of 0.09° (standard deviation [SD] 0.06°), 0.02° (SD 0.07°), and 0.06° (SD 0.14°) for longitudinal, lateral, and vertical rotations, respectively. The average positioning accuracy was 0.06° (SD 0.04°), 0.08° (SD 0.06°), and 0.08° (SD 0.07°) for longitudinal, lateral and vertical rotations, respectively. The results of the HTT showed an overall three-dimensional accuracy of 0.76 mm (SD 0.46 mm) for the frameless technique, 0.87 mm (SD 0.44 mm) for the relocatable mask, and 1.19 mm (SD 0.45 mm) for the frame-based technique. The study showed high detection accuracy and a subdegree positioning accuracy. On the basis of phantom studies, the frameless technique showed comparable accuracy to the frame-based approach.

Deep brain stimulation and frameless stereotactic radiosurgery in the treatment of bilateral parkinsonian tremor: target selection and case report of two patients

Considerable positive experience in functional radiosurgery has been reported since Leksell's first experience in 1951, but the development of frameless radiosurgery was been limited because of the difficulty of identifying invisible functional targets. In this paper we report on two cases of bilateral parkinsonian tremor successfully treated with DBS on one side and with frameless radiosurgery on the contralateral side. We focus on the methodology developed to define the three-dimensional target coordinates for frameless radiosurgery. Two patients suffering from a disabling upper-limb parkinsonian tremor underwent frameless radiosurgical thalamotomy. To accurately identify the treatment target the CT gantry was treated as a stereotactic frame; a rototranslation between the origin of the screen and the origin of the stereotactic atlas allowed us to obtain atlas-registered 3D coordinates of each point on the CT axial brain slices. Both patients achieved complete bilateral tremor control by unilateral radiosurgery and contralateral DBS. We developed a method for determining the 3D coordinates of a known functional target to treat with frameless radiosurgery. Based on the initial experiences, frameless radiosurgery appears to be an alternative treatment for Parkinsonian upper limb tremor in the presence of increased surgical risks for DBS placement.

Frameless Image-Guided Radiosurgery for Initial Treatment of Typical Trigeminal Neuralgia

Frameless Image-Guided Radiosurgery for Initial Treatment of Typical Trigeminal Neuralgia

A clinical comparison of patient setup and intra-fraction motion using frame-based radiosurgery versus a frameless image-guided radiosurgery system for intracranial lesions

Background and purpose A comparison of patient positioning and intra-fraction motion using invasive frame-based radiosurgery with a frameless X-ray image-guided system utilizing a thermoplastic mask for immobilization. Materials and methods Overall system accuracy was determined using 57 hidden-target tests. Positioning agreement between invasive frame-based setup and image-guided (IG) setup, and intra-fraction displacement, was evaluated for 102 frame-based SRS treatments. Pre and post-treatment imaging was also acquired for 7 patients (110 treatments) immobilized with an aquaplast mask receiving fractionated IG treatment. Results The hidden-target tests demonstrated a mean error magnitude of 0.7 mm (SD = 0.3 mm). For SRS treatments, mean deviation between frame-based and image-guided initial positioning was 1.0 mm (SD = 0.5 mm). Fusion failures were observed among 3 patients resulting in aberrant predicted shifts. The image-guidance system detected frame slippage in one case. The mean intra-fraction shift magnitude observed for the BRW frame was 0.4 mm (SD = 0.3 mm) compared to 0.7 mm (SD = 0.5 mm) for the fractionated patients with the mask system. Conclusions The overall system accuracy is similar to that reported for invasive frame-based SRS. The intra-fraction motion was larger with mask-immobilization, but remains within a range appropriate for stereotactic treatment. These results support clinical implementation of frameless radiosurgery using the Novalis Body Exac-Trac system.

Localization Technique for Frameless Image-guided Robotic Radiosurgery of Arteriovenous Malformations

Purpose/Objective(s): To integrate three-dimensional digital rotation angiography (3D DRA) and two-dimensional digital subtraction angiography (2D DSA) imaging in a localization technique that enables frameless image-guided robotic radiosurgery of arteriovenous malformations (AVMs). Materials/Methods: The geometric integrity of the 3D DRA images generated by a clinical flat panel detector Carm neuroangiography system was evaluated and quantified by imaging a phantom with embedded markers. Dedicated DSA acquisition modes with preset C-arm positions were configured. The geometric reproducibility of the C-arm presets was investigated and its impact on localization accuracy evaluated. An imaging protocol comprising anterior-posterior (AP) and lateral (LAT) 2D DSA series combined with 3D DRA without couch displacement between acquisitions was introduced. A software environment (Angio-Localize) was developed for 2D-3D registration of the 3D DRA and the 2D DSA images to correct for: (i) small misalignments of the C-arm with respect to the assumed geometry of the preset imaging positions and (ii) potential patient motion between the image series. Within the same environment, correlated navigation of the registered 3D DRA and DSA images was incorporated so that an AVM could be localized and contoured within the 3D DRA coordinate space. AVM contours were then transferred onto a planning CT by CT-3D DRA registration. The subsequent treatment planning and delivery followed the standard process for frameless image-guided robotic radiosurgery treatments. Results: The magnitude of the 3D DRA spatial distortions was smaller than 0.3 mm throughout a 140 mm x 140 mm x 140 mm field of view. Localization uncertainties resulting from the achievable reproducibility of the C-arm preset positions were reduced to less than 0.2 mm with 3D-2D image registration. Overall system-related localization uncertainty within the DRA coordinate space was estimated to be 0.4-0.5 mm. The localization protocol was implemented clinically and image-guided frameless robotic radiosurgical treatments with this technique were initiated. Conclusions:The integration of three-dimensional digital rotation angiography (3D DRA) and two-dimensional digital subtraction angiography (2D DSA) imaging in a localization technique that enables frameless image-guided robotic radiosurgery of arteriovenous malformations (AVMs) is possible. Clinically it is expected to result in increased patient comfort; reduced time pressure on clinical and technical staff, and possible reduction of the number of neuro-angiography procedures for particular patient.

Experience with cyberknife

Objectifs New indication of Stereotactic radiosurgery. To describe the Cyberknife. To know about Frameless radiosurgery. Messages a retenir Stereotactic surgery with cyberknife enlarges the therapeutic options in oncology. Cyberknife allows frameless radiosurgery with a high precision. Fields of investigations are still works in progress. Resume The Cyberknife is a unique instrument for performing frameless stereotactic radiosurgery. Rather than using rigid immobilization, the Cyberknife relies on an image-to-image correlation algorithm for target localization. The Cyberknife System uses the coupling of an orthogonal pair of X-ray cameras to a dynamically manipulated robot-mounted novel linear accelerator with six degrees of freedom that guides the therapy beam to the intended target without the use of frame-base fixation. Real time imaging allows the tracking of patient movements. Lesions were tracked by bony landmarks without any implanted fiducials. The authors describe the technical specifications of the Cyberknife and summarize the clinical experience with 1800 patients treated with single fraction radiosurgery for various indications throughout the body.

Robotic radiosurgery for severe recurrent and primary head and neck cancer

e17038 Background: We considered the functional reconstruction following head and neck tumor ablation, however, it was impossible to recover completely the function against the severe postoperative status. Here we describe our aim to improve local control and to obtain organ preservation by using the non-surgical outpatient procedure the CyberKnife frameless radiosurgery (CK). Methods: Between March 2006 and January 2008, 22 patients with severe recurrent, previously treated with conventional methods, and 14 patients with primary lesions were treated with CK in the management of head and neck cancer. All the patients had biopsy confirmation of disease prior to radiation therapy; rT2 (3 patients), rT3 (8), rT4 (9), T2 (5), T3 (3), T4 (6), N1 (4), N2b (3), M1 (1), tongue (11), mandibule (11), maxilla (6), maxillary sinus (4), soft palate (2), with sq. cell ca.(34), adenoid cystic ca.(1), fibrosarcoma (1). The treatment plan was set up based on CT, MRI and PET-CT in Yokohama CyberKnife Center. CK's lightweight linear accelerator always irradiates toward the target from 120 directions with image-guided computer based on CT. Marginal Doses were 2000–4200cGy in 3–5 fractions. Curative effects were evaluated assessed by RECIST included PET. Results: 11/22 (50.0%) of the severe recurrent cases were controlled from 6 to 25 months at follow-up range. The local recurrent cases with non-lymph node metastases were excellently controlled as 10/12 (83.3%). For the primary cases, significant tumor reduction were noted at the third-month follow-up, all the 14 patients went into remission with 5 cases in CR, and 9 cases in PR. Between the 4–6 month follow-up, 4 cases were performed additional CK treatment for the recurrent lesions, however, 3 patients with T4 tongue cancer were not cured. Finally, the total control rate of the primary cases was 10/14 (71.4%), however, 8/9 (88.9%) primary cases except tongue cancer has been controlled treated by CK with chemotherapy. The cases of non-lymph node metastases were cured 8/8 (100.0%) by CK. There have been no seriously complications of treatment caused by CK except severe osteoradionecrosis of the 4 patients irradiated with maximum dose. Conclusions: It is now possible with the development of CyberKnife Radiosurgery to improve our treatments of the local control in head and neck cancer. No significant financial relationships to disclose.

Frameless Image-Guided Intracranial Stereotactic Radiosurgery: Clinical Outcomes for Brain Metastases

After preclinical investigations confirming the accuracy of target localization by frameless image-guided radiosurgery, we report the clinical outcomes of patients with brain metastases who underwent frameless radiosurgery. Between 2005 and 2006, 53 patients underwent frameless stereotactic radiosurgery using a linear accelerator equipped with on-board image guidance for the treatment of 158 brain metastases. The radiation doses were delivered in a single fraction (dose range, 12-22 Gy; median, 18). Patients were followed with magnetic resonance imaging scans at 2-3-month intervals. Progression-free survival was the primary study endpoint. With a median follow-up of 38 weeks (range, 14-112), the overall survival rate was 70% at 6 months, 44% at 1 year, 29% at 18 months, and 16% at 24 months. Local control was achieved in 90% of 168 treated lesions at 6 months, 80% at 12 months, 78% at 18 months, and 78% at 24 months. Local control tended to be improved in lesions treated with >or=18 Gy and for lesions <0.2 cm(3). Adverse events occurred in 5 patients (9.6%). No evidence of imaging changes on post-stereotactic radiosurgery scans was found to suggest mistargeting of a radiation isocenter. The clinical outcomes after frameless stereotactic radiosurgery were comparable to those after frame-based radiosurgery techniques. Given its significant advantages in terms of patient comfort, ability to use fractionated treatment regimens, and convenience in scheduling of personnel and equipment resources, frameless radiosurgery will likely become a common technique for intracranial radiosurgery.