Individual Beam Sharpening Improves Composite Dose Fall-off near a Target for Non-Isocentric Cyberknife Radiosurgery

Abstract OBJECTIVE: Intramedullary spinal cord arteriovenous malformations (AVMs) have an unfavorable natural history that characteristically involves myelopathy secondary to progressive ischemia and/or recurrent hemorrhage. Although some lesions can be managed successfully with embolization and surgery, AVM size, location, and angioarchitecture precludes treatment in many circumstances. Given the poor outlook for such patients, and building on the successful experience with radiosurgical ablation of cerebral AVMs, our group at Stanford University has used CyberKnife (Accuray, Inc., Sunnyvale, CA) stereotactic radiosurgery (SRS) to treat selected spinal cord AVMs since 1997. In this article, we retrospectively analyze our preliminary experience with this technique. METHODS: Fifteen patients with intramedullary spinal cord AVMs (nine cervical, three thoracic, and three conus medullaris) were treated by image-guided SRS between 1997 and 2005. SRS was delivered in two to five sessions with an average marginal dose of 20.5 Gy. The biologically effective dose used in individual patients was escalated gradually over the course of this study. Clinical and magnetic resonance imaging follow-up were carried out annually, and spinal angiography was repeated at 3 years. RESULTS: After a mean follow-up period of 27.9 months (range, 3–59 mo), six of the seven patients who were more than 3 years from SRS had significant reductions in AVM volumes on interim magnetic resonance imaging examinations. In four of the five patients who underwent postoperative spinal angiography, persistent AVM was confirmed, albeit reduced in size. One patient demonstrated complete angiographic obliteration of a conus medullaris AVM 26 months after radiosurgery. There was no evidence of further hemorrhage after CyberKnife treatment or neurological deterioration attributable to SRS. CONCLUSION: This description of CyberKnife radiosurgical ablation demonstrates its feasibility and apparent safety for selected intramedullary spinal cord AVMs. Additional experience is necessary to ascertain the optimal radiosurgical dose and ultimate efficacy of this technique.

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140 speaker MARKER-BASED AND MARKER-LESS NAVIGATION IN CYBERKNIFE RADIOSURGERY

Radiotherapy and Oncology ◽

10.1016/s0167-8140(11)70262-6 ◽

2011 ◽

Vol 99 ◽

pp. S52

Author(s):

A. Schweikard

Keyword(s):

Cyberknife Radiosurgery

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CyberKnife rhizotomy for facetogenic back pain: a pilot study

Neurosurgical FOCUS ◽

10.3171/foc-07/12/e2 ◽

2007 ◽

Vol 23 (6) ◽

pp. E1 ◽

Cited By ~ 3

Author(s):

Gordon Li ◽

Chirag Patil ◽

John R. Adler ◽

Shivanand P. Lad ◽

Scott G. Soltys ◽

...

Keyword(s):

Back Pain ◽

Radiofrequency Ablation ◽

Facet Joint ◽

Late Onset ◽

Target Volume ◽

Facet Joints ◽

Positron Emission ◽

Cyberknife Radiosurgery ◽

Joint Injections

Object By targeting the medial branches of the dorsal rami, radiofrequency ablation and facet joint injections can provide temporary amelioration of facet joint–producing (or facetogenic) back pain. The authors used CyberKnife radiosurgery to denervate affected facet joints with the goal of obtaining a less invasive yet more thorough and durable antinociceptive rhizotomy. Methods Patients with refractory low-back pain, in whom symptoms are temporarily resolved by facet joint injections, were eligible. The patients were required to exhibit positron emission tomography–positive findings at the affected levels. Radiosurgical rhizotomy, targeting the facet joint, was performed in a single session with a marginal prescription dose of 40 Gy and a maximal dose of 60 Gy. Results Seven facet joints in 5 patients with presumptive facetogenic back pain underwent CyberKnife lesioning. The median follow-up was 9.8 months (range 3–16 months). The mean planning target volume was 1.7 cm3 (range 0.9–2.7 cm3). A dose of 40 Gy was prescribed to a mean isodose line of 79% (range 75–80%). Within 1 month of radiosurgery, improvement in pain was observed in 3 of the 5 patients with durable responses at 16, 12, and 6 months, respectively, of follow-up. Two patients, after 12 and 3 months of follow-up, have neither improved nor worsened. No patient has experienced acute or late-onset toxicity. Conclusions These preliminary results suggest that CyberKnife radiosurgery could be a safe, effective, and non-invasive alternative to radiofrequency ablation for managing facetogenic back pain. No patient suffered recurrent symptoms after radiosurgery. It is not yet known whether pain relief due to such lesions will be more durable than that produced by alternative procedures. A larger series of patients with long-term follow-up is ongoing.

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