Technical description, phantom accuracy, and clinical feasibility for fiducial-free frameless real-time image-guided spinal radiosurgery

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>The authors describe the technical application of the Xsight Spine Tracking System, data pertaining to accuracy obtained during phantom testing, and the initial clinical feasibility of using this fiducial-free alignment system with the CyberKnife in spinal radiosurgery.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The Xsight integrates with the CyberKnife radiosurgery system to eliminate the need for implantation of radiographic markers or fiducials prior to spinal radiosurgery. It locates and tracks spinal lesions relative to spinal osseous landmarks. The authors performed 10 end-to-end tests of accuracy using an anthropomorphic head and cervical spine phantom. Xsight was also used in the treatment of 50 spinal lesions in 42 patients. Dose planning was based on 1.5-mm-thick computed tomography slices in which an inverse treatment planning technique was used.</jats:p> <jats:p>All lesions could be treated using the fiducial-free tracking procedure. Phantom tests produced an overall mean targeting error of 0.52 ± 0.22 mm. The setup time for patient alignment averaged 6 minutes (range 2–45 minutes). The treatment doses varied from 12 to 25 Gy to the median prescription isodose of 65% (40 to 70%). The tumor volume ranged between 1.3 and 152.8 cm<jats:sup>3</jats:sup>The mean spinal cord volume receiving greater than 8 Gy was 0.69 ± 0.35 cm<jats:sup>3</jats:sup>No short-term adverse events were noted during the 1- to 7-month follow-up period. Axial and radicular pain was relieved in 14 of 15 patients treated for pain.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Fiducial-free tracking is a feasible, accurate, and reliable tool for radiosurgery of the entire spine. By eliminating the need for fiducial implantation, the Xsight system offers patients noninvasive radiosurgical intervention for intra- and paraspinal tumors.</jats:p></jats:sec>

Report of AAPM TG 135: Quality assurance for robotic radiosurgery

“…The bony structure tracking includes skull tracking (6D Skull) and spine tracking 41,42 (XSight V R Spine). Soft tissue tracking (XSight V R Lung) uses density differences between the target and surrounding lung tissues without the need for invasive fiducial placement.…”

Stereotactic body radiotherapy for spinal metastases: current status, with a focus on its application in the postoperative patient

“…The IGRT systems can be broken down into those based on stereoscopic xray-and CT-based imaging. For spine SBRT, the target can be positioned accurately to within 1-2 mm and 1°-2° with either IGRT system, 9,22,25,27,34 but there are inherent differences between the two that require discussion.…”

Radiosurgery for Metastatic Spinal Tumors: Follow-Up MR Findings

“…5,[8][9][10][11][12][13][14][15][16][17] Although MR imaging is the best tool to evaluate the status of metastatic spinal tumors, many results about treatment efficacy are confined to clinical data such as pain control. 8,10,11,17 Some reports have included measurements of tumor volume by MR imaging but have not provided detailed MR imaging findings. 12,13,15,16 The life span of affected patients is limited, in most cases, by systemic disease.…”

“…Several studies have demonstrated the technical feasibility and clinical efficacy of SRS for spinal metastatic tumors, and it has become a standard treatment for these tumors. 5,[8][9][10][11][12][13][14][15][16][17] The main goals of SRS in this setting are to arrest tumor growth throughout the patient's life (rather than cure the lesions), improve symptoms, and prevent the development or progression of neurologic deficits. Previously published reports about efficacy of SRS for spinal metastatic tumors are focused on just clinical data and outcome.…”