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Peter C. Gerszten and Edward A. Monaco III

in a circumferential manner under fluoroscopic guidance. The physically allowable arc for the working tip is 16°. The goal was to create a cavity within the effected vertebral body prior to balloon insertion. The created cavity space could be visualized on lateral fluoroscopic imaging. The exact volume of tumor removed by the wand cannot be measured. The cavity size was extrapolated by the different positions of the wand tip within the affected vertebral body. There were no complications associated with the procedure. Polymethylmethacrylate was then placed into the

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Peter C. Gerszten and William C. Welch

the balloon. As seen in Fig. 3B , the newly created space can be visualized on lateral fluoroscopic imaging. The exact volume of tumor removed using the wand cannot be measured. The cavity size was extrapolated by the different positions of the wand tip within the affected VB. There were no complications associated with the kyphoplasty procedure. There was no case of extravasation of PMMA into the spinal canal. F ig . 1. Photograph showing the Cavity SpineWand with its bayoneted end that allows for maximum tissue removal within the VB. F ig . 2

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Quality of life assessment in patients undergoing nucleoplasty-based percutaneous discectomy

Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2005

Peter C. Gerszten, William C. Welch and Joseph T. King Jr.

, microdiscecto-my was an “unsatisfactory” treatment. Hence, patients with contained herniated discs may best be treated with alternative disc decompression approaches. Percutaneous disc decompression is based on the principle that creating a small reduction of volume in a closed hydraulic space, such as an intact (that is, contained herniated) disc, can promote significant relief of pressure 8 , 15 and therefore reduce or eliminate pain. Once intradiscal pressure is relieved, the disc is believed to downregulate inflammatory mediators, reduce in size, and initiate a healing

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Peter C. Gerszten, Josef Novotny Jr., Mubina Quader, Valerie C. Dewald and John C. Flickinger

treatment planning system (version 8.0, Philips) and a 1.5-mm CT slice thickness were used to plan all spine radiosurgery treatments. F ig . 1. Photograph showing the Synergy S system, which combines a LINAC with an onboard, integrated high-resolution 3D volume imaging system that allows the target to be visualized at the precise time of treatment while the patient is in position on the treatment couch. The cone beam imaging system is located in a position orthogonal to the LINAC beam. The robotic couch is adjusted in 3 translations and 3 rotations to ensure that

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Peter C. Gerszten, Cihat Ozhasoglu, Steven A. Burton, Shalom Kalnicki and William C. Welch

Object

The role of stereotactic radiosurgery for the treatment of intracranial lesions is well established. Its use for the treatment of spinal lesions has been limited by the availability of effective target-immobilizing devices. In this study the authors evaluated the CyberKnife Real-Time Image-Guided Radiosurgery System for spinal lesion treatment involving a single-fraction radiosurgical technique.

Methods

This frameless image-guided radiosurgery system uses the coupling of an orthogonal pair of x-ray cameras to a dynamically manipulated robot-mounted linear accelerator possessing six degrees of freedom, which guides the therapy beam to the target without the use of frame-based fixation. Cervical lesions were located and tracked relative to osseous skull landmarks; lower spinal lesions were tracked relative to percutaneously placed gold fiducial bone markers. Fifty-six spinal lesions in 46 consecutive patients were treated using single-fraction radiosurgery (26 cervical, 15 thoracic, and 11 lumbar, and four sacral). There were 11 benign and 45 metastatic lesions.

Tumor volume ranged from 0.3 to 168 ml (mean 26.7 ml). Thirty-one lesions had previously received external-beam radiotherapy with maximum spinal cord doses. Dose plans were calculated based on computerized tomography scans acquired using 1.25-mm slices. Tumor dose was maintained at 12 to 18 Gy to the 80% isodose line; spinal cord lesions receiving greater than 8 Gy ranged from 0 to 1.3 ml (mean 0.3 ml). All patients tolerated the procedure in an outpatient setting. No acute radiation-induced toxicity or new neurological deficits occurred during the follow-up period. Axial and radicular pain improved in all patients who were symptomatic prior to treatment.

Conclusions

Spinal stereotactic radiosurgery involving a frameless image-guided system was found to be feasible and safe. The major potential benefits of radiosurgical ablation of spinal lesions are short treatment time in an outpatient setting with rapid recovery and symptomatic response. This procedure offers a successful alternative therapeutic modality for the treatment of a variety of spinal lesions not amenable to open surgical techniques; the intervention can be performed in medically untreatable patients, lesions located in previously irradiated sites, or as an adjunct to surgery.

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James P. Caruso, Or Cohen-Inbar, Mark H. Bilsky, Peter C. Gerszten and Jason P. Sheehan

surgery is to decompress epidural tumor from a posterolateral approach to circumferentially decompress the spinal cord and reconstitute the thecal sac, followed by long posterior segmental fixation (e.g., with pedicle screws) to provide immediate stability. 43 Following surgery, patients undergo high-dose single-fraction or hypofractionated radiation to ablate the residual gross and microscopic tumor volume. The radiation treatments spare normal tissue tolerance to at-risk structures, such as the spinal cord, since the separation surgery establishes an adequate

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Peter C. Gerszten, Steven A. Burton, Cihat Ozhasoglu, William J. Vogel, William C. Welch, Joseph Baar and David F. Friedland

prior radiation exposure and those with lesions close to the spinal cord. The prescription dose was independent of the tumor volume. In each case, the spinal cord and/or cauda equina was outlined as a critical structure. At the level of the cauda equina, the spinal canal was outlined. Therefore, at the level of the cauda equina, the critical volume is the entire spinal canal and not actual neural tissue. The maximum dose was defined as that delivered to a single pixel. Several patients had previously undergone resection and placement of stabilizing hardware; thus

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Peter C. Gerszten, Stephanie Chen, Mubina Quader, Yuanguang Xu, Josef Novotny Jr. and John C. Flickinger

14 Gy, which was delivered in a single fraction with a 2-mm PTV expansion of 12 Gy. The maximum dose delivered to the spinal cord was 10 Gy with a 1-mm safety expansion that received a maximum dose of 9 Gy. E: Dose-volume histogram of the radiosurgery treatment plan demonstrating 90% coverage of the GTV and 99% coverage of the PTV. The patient reported significant improvement in his symptoms within 1 month. Six patients (13%) had undergone surgical stabilization at the time of open resection and therefore spinal instrumentation was present at the time of the

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Peter C. Gerszten, Edward A. Monaco III, Mubina Quader, Josef Novotny Jr., Jong Oh Kim, John C. Flickinger and M. Saiful Huq

spine radiosurgery treatments. F ig . 1. The Synergy S system (Elekta, Inc.) combines a linear accelerator with an onboard, integrated high-resolution 3D volume imaging system that allows the target to be visualized at the precise moment of treatment while the patient is in position on the treatment couch. The cone beam imaging system is located in a position orthogonal to the linear accelerator beam. The robotic couch is adjusted in 3 translations and 3 rotations to ensure that the radiation is directed precisely at the target. Initial patient setup was

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Peter C. Gerszten, Anand Germanwala, Steven A. Burton, William C. Welch, Cihat Ozhasoglu and William J. Vogel

. The patients were placed supine in a conformal alpha cradle during CT scanning and during treatment. The CT scans were acquired using 1.25-mm-thick slices to include the lesion of interest and all fiducials. 28 The entire VB and any adjacent area where the tumor extended were included in the radiosurgical treatment plan as the target volume. The patients then returned for the radiosurgical treatment. All treatments were performed using a single-fraction technique in an outpatient setting. Results The two procedures were successfully completed in all