Healthcare Professionals

Reviews

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• The CyberKnife® Robotic Radiosurgery System in 2010. Kilby et al. This review, authored by Accuray research team members, includes the most complete and detailed technical description of the CyberKnife VSI™ System with detailed descriptions of key subsystem and a review of geometric studies on a wide range of experiments involving phantom tests and patient data. In addition, the relationship between technical developments and the greatly increased range of clinical applications they have allowed is described.
• CyberKnife radiosurgery for prostate cancer. A. Katz. This review summarizes the motivating factors for the treatment of prostate cancer with CyberKnife SBRT. Also, presented is an evaluation of the current literature and discussion of the future of prostate cancer treatment with SBRT.
• CyberKnife Robotic Radiosurgery System for tumor treatment. Hara et al. 2008. Stanford researchers provide a thorough, straightforward review of the technical capabilities of the CyberKnife® System that allow it to be used to treat tumors throughout the body.
• CyberKnife radiosurgery in neurosurgical practice. Naff 2008. Dr. Naff, from Sinai Hospital in Baltimore and Johns Hopkins University, describes the unique features of the CyberKnife System, and its use in brain and spine radiosurgery.
• Technology Insight: image-guided robotic radiosurgery—a new approach for noninvasive ablation of spinal lesions. Romanelli and Adler, 2008. These authors describe the application of radiosurgery for spinal lesions, featuring the non-invasive, fiducial-free Xsight® Spine Tracking System. Authors highlight the ability afforded by frameless radiosurgery to treat in more than one session when lesions are near or within the radiosensitive spinal cord.

Intracranial

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• CyberKnife radiosurgery for benign meningiomas: short-term results in 199 patients. Colombo et al. 2009. Researchers from Vicenza, Italy demonstrated a 5-year actuarial tumor control rate of 93.56% and a 0.5% complication rate. According to the authors, the ability to conveniently treat in multiple sessions allowed them to treat “63 patients (30%) who could not have been treated by single-session radiosurgical techniques.”
• Quality of radiosurgery for single brain metastases with respect to treatment technology: a matched-pair analysis. Wowra et al. 2009. This study compares the technical features of the Gamma Knife and the CyberKnife System, and their clinical outcomes in the treatment of single brain metastases, using the method of matched-pair analysis. Clinical outcomes were nearly identical between groups.
• Nonisocentric radiosurgical rhizotomy for trigeminal neuralgia. Adler et al. 2009. Stanford researchers examined outcomes after radiosurgery using the CyberKnife System for trigeminal neuralgia using treatment parameters that have evolved over several years. This “optimal” treatment approach resulted in pain relief judged as excellent or good by 96% of patients, with relatively low rates of facial numbness.
• Early results of CyberKnife radiosurgery for arteriovenous malformations. Colombo et al. 2009. Researchers using the CyberKnife System in Vicenza, Italy conducted a prospective study of 279 patients with arteriovenous malformations (AVMs) treated with the CyberKnife System. The overall rate of complete obliteration was 81.2% in patients with 36 months of follow-up, and no permanent complications were observed.
• Survival following CyberKnife radiosurgery and hypofractionated radiotherapy for newly diagnosed glioblastoma multiforme. Lipani et al. 2008. Researchers from Stanford University performed CyberKnife System treatment on 20 GBM patients after tumor resection. The overall median survival was 16 months, which compares favorably to post-surgical external beam radiation therapy.
• Cost-effectiveness analysis for trigeminal neuralgia: CyberKnife vs microvascular decompression. Tarricone et al. 2008. Investigators from Milan, Italy show that both radiosurgery using the non-invasive CyberKnife System and a surgical treatment, microvascular decompression (MVD), produce high rates of pain relief. The costs of a hospital stay and surgery, however, make MVD more expensive than CyberKnife SRS.
• Stereotactic radiosurgery of the postoperative resection cavity for brain metastases. Soltys, et al. 2007. Researchers from Stanford University used the CyberKnife System for adjuvant treatment of brain metastases by targeting post-resection cavities. They obtained a 79% local control rate at 12 months, which compares favorably to historic whole brain radiation treatment results.
• A volumetric study of CyberKnife hypofractionated stereotactic radiotherapy as salvage for progressive malignant brain tumors: initial experience. Giller et al. 2007. Researchers from Baylor University Medical Center used the CyberKnife System to perform fractionated stereotactic radiosurgery on lesions that are difficult to treat in a single fraction approach.
• Visual field preservation after multisession CyberKnife radiosurgery for perioptic lesions. Adler, et al. 2006. Stanford University researchers used the CyberKnife System to obtain high rates of tumor control for tumors near (less than 2 mm from) the optic apparatus; over 90% of patients treated maintained or improved their vision.
• Staged stereotactic irradiation for acoustic neuroma. Chang et al. 2005. Stanford researchers show that fractionated treatment using the CyberKnife System for acoustic neuromas may improve hearing preservation.

Head & Neck

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• Stereotactic body radiotherapy for recurrent squamous cell carcinoma of the head and neck: results of a phase I dose-escalation trial. Heron et al. 2009. University of Pittsburgh researchers recruited 31 patients with recurrent squamous cell carcinoma of the head and neck, each of whom had previous radiation therapy, to participate in this Phase I study of stereotactic body radiotherapy (SBRT) using the CyberKnife System. The authors concluded that SBRT using the CyberKnife System was “feasible and safe”, and a possible alternative to conventional radiation or surgery for previously irradiated patients.
• Treatment techniques and site considerations regarding dysphagia-related quality of life in cancer of the oropharynx and nasopharynx. Teguh et al. 2008. Rotterdam researchers related difficulties eating and swallowing in part to levels of radiation received by swallowing muscles. Brachytherapy boost and boosts using the CyberKnife System are less likely than radiotherapy boost to cause this complication.
• Excellent local control with stereotactic radiotherapy boost after external beam radiotherapy in patients with nasopharyngeal carcinoma. Hara et al. 2008. Stanford researchers obtained excellent local control (98% at five years) in patients with nasopharyngeal carcinoma using EBRT combined with a radiosurgery boost using the CyberKnife System and chemotherapy.
• Robotic radiosurgery vs. brachytherapy as a boost to intensity modulated radiotherapy for tonsillar fossa and soft palate tumors: the clinical and economic impact of an emerging technology. Nijdam et al. 2007. Rotterdam researchers show that both brachytherapy and radiosurgery using the CyberKnife System can boost the radiation dose to oral cavity tumors and achieve comparable short-term outcomes after intensity-modulated radiotherapy. Because patients treated with the CyberKnife System are not hospitalized or operated on their treatment may be less expensive.

Lung

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• Stereotactic body radiotherapy using real-time tumor tracking in octogenarians with non-small cell lung cancer. van der Voort van Zyp et al. 2010. Rotterdam researchers show that CyberKnife radiosurgery can be an effective treatment approach, with low rates of toxicity, for elderly patients with non-small cell lung cancer.
• Quality of life after stereotactic radiotherapy for stage I non-small-cell lung cancer. van der Voort van Zyp et al. 2010. Researchers from Rotterdam, The Netherlands, report on quality of life of 39 lung cancer patients in the first year after treatment with the CyberKnife System. In addition to a high tumor control rate and acceptable overall survival, the researchers observed no deterioration in global health status and respiratory symptoms, and a significant improvement in emotional functioning.
• Radical CyberKnife radiosurgery with tumor tracking: an effective treatment for inoperable small peripheral stage I non-small cell lung cancer. Collins et al. 2009. Georgetown researchers treated 20 patients with inoperable clinical stage I NSCLC with the CyberKnife System, delivering doses of 42-60 Gy in three equal fractions. At a median follow-up of 25 months for surviving patients, Kaplan-Meier overall survival at two years was 87%.
• Stereotactic radiotherapy with real-time tumor tracking for non-small cell lung cancer: Clinical outcome. van der Voort van Zyp et al., 2009. Clinicians from Rotterdam, the Netherlands, used the CyberKnife System to treat 70 surgically or medically inoperable patients with peripheral Stage I NSCLC with 45-60 Gy in 3 fractions. Authors report overall low toxicity and local tumor control at 2 years of 98% in the high-dose (60 Gy) patients.
• Fractionated stereotactic body radiation therapy in the treatment of primary, recurrent, and metastatic lung tumors: the role of positron emission tomography/computed tomography-based treatment planning. Coon et al. 2008. University of Pittsburgh researchers treated a variety of patients with primary lung cancer, metastatic lung tumors, or recurrent cancer. Using the CyberKnife System they delivered 3 fractions of 20 Gy and concluded it was an effective treatment for patients with medically inoperable recurrent or metastatic lung cancer.
• CyberKnife radiosurgery for stage I lung cancer: results at 36 months. Brown et al. 2007. Miami researchers show that image-guided robotic stereotactic radiosurgery of lung tumors with the CyberKnife System in medically inoperable patients with early non-small-cell lung cancer (NSCLC) achieves excellent local disease control with limited toxicity to surrounding tissues and, in many cases, might be curative for patients for whom surgery is not an option.
• Radical stereotactic radiosurgery with real-time tumor motion tracking in the treatment of small peripheral lung tumors. Collins et al. 2007. Georgetown researchers used the CyberKnife System to deliver 45-60 Gy in 3 fractions to small tumors (including some metastatic tumors) in the outer lung, resulting in 83% local control and 84% overall survival at 12 months.

Spine

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• Treatment of spinal tumors using CyberKnife fractionated stereotactic radiosurgery: pain and quality-of-life assessment after treatment in 200 patients. Gagnon et al. 2009. Mean pain scores decreased after treatments of spinal lesions using the CyberKnife System, and continued to decrease throughout the 4-year follow-up period. Quality of life was preserved.
• Stereotactic body radiotherapy is effective salvage therapy for patients with prior radiation of spinal metastases. Sahgal et al. 2009. Researchers from UC San Francisco treated 39 patients with 60 spinal metastases, over half of which had been irradiated previously, using the CyberKnife System. At a median follow-up of 8.5 months, encouraging levels of disease control without serious complications were obtained in all patients.
• Delayed radiation-induced myelopathy after spinal radiosurgery. Gibbs et al. 2009. In a collaboration between Stanford and University of Pittsburgh researchers, the records of 1075 patients treated with the CyberKnife System for spinal radiosurgery between 1996 and 2005 were examined. A total of six patients (approximately 0.6%) developed delayed spinal cord injury; authors recommended limiting radiation exposure to the spinal cord.
• Cost-utility analysis of the CyberKnife System for metastatic spinal tumors. Papatheofanis et al. 2009. Researchers from UC San Diego, Stanford, and the Aequitas group, showed in a cost-utility study that radiosurgery using the CyberKnife System was a cost-effective primary intervention for patients with metastatic spinal tumors compared to EBRT.
• CyberKnife radiosurgery for breast cancer spine metastases: a matched-pair analysis. Gagnon et al. 2007. Georgetown University researchers performed a comparison of external beam radiation therapy to CyberKnife System stereotactic radiosurgery for breast cancer metastasis to the spine. Outcomes were statistically comparable, even though most of the patients treated with the CyberKnife System had previously undergone external beam radiation therapy.
• Radiosurgery for spinal metastases: clinical experience in 500 cases from a single institution. Gerszten et al. 2007. Researchers from the University of Pittsburgh Medical Center performed the largest published study on spinal radiosurgery. Their results show that single fraction CyberKnife System radiosurgery is safe and effective both as a primary treatment modality and as salvage treatment for spinal tumors.
• CyberKnife radiosurgery for benign intradural extramedullary spinal tumors. Dodd et al. 2006. Stanford University researchers determined that benign lesions located on the spinal cord can be treated safely and effectively with the CyberKnife System.
• Multisession CyberKnife radiosurgery for intramedullary spinal cord arteriovenous malformations. Sinclair et al. 2006. Stanford University researchers used the CyberKnife System to treat spinal cord AVMs with fractionated stereotactic radiosurgery.

Prostate

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• Stereotactic body radiotherapy for low-risk prostate cancer: five-year outcomes. Freeman & King. (Paper available for free at this link). Researchers from Stanford University and Naples Florida present the first report of 5-year follow-up for CyberKnife treatment of prostate cancer. For their combined cohort of 41 low-risk prostate cancer patients, the 5-year disease-free survival rate is 92.7% with generally low rates of mild GU and GI toxicity.
• Long-Term Outcomes from a Prospective Trial of Stereotactic Body Radiotherapy for Low-Risk Prostate Cancer. King et al. 2011. In this update to Stanford University’s Phase II clinical trial of 67 low-risk prostate cancer patients treated with the CyberKnife System, the four-year Kaplan-Meier PSA relapse-free rate was 94%. Urinary and rectal toxicities were infrequent and not severe, equal to or lower than those in dose-escalated 3D-CRT studies and hypofractionated IMRT studies.
• Stereotactic body radiotherapy for organ-confined prostate cancer. Katz et al. 2010. Winthrop University researchers used the CyberKnife System to treat 304 patients with clinically localized prostate cancer. For those patients with a minimum of 12 months follow-up, 98% overall biochemical control rate was obtained. Both acute and late toxicity were mild and erectile function was preserved in 87% of patients at 18 months.
• Stereotactic body radiotherapy: an emerging treatment approach for localized prostate cancer. Friedland et al. 2009. Researchers from Naples, Florida presented their experience with prostate radiosurgery using the CyberKnife System. In these first 112 patients with early stage organ-confined disease, 97% biochemical control was obtained at a median of 24 months, with urethral/rectal toxicity comparable to EBRT. Erectile function was preserved in 81% of patients at two years.
• Stereotactic body radiotherapy for localized prostate cancer: interim results of a prospective phase II clinical trial. King et al. 2008. Stanford University Researchers used the CyberKnife System to treat 41 low-risk prostate cancer patients. With a median follow-up of 33 months they found no patient had a PSA failure. They conclude that the early and late toxicity profile and PSA response for prostate treatment using the CyberKnife System are highly encouraging.
• Image-guided stereotactic body radiation therapy for clinically localized prostate cancer: preliminary clinical results. Bolzicco et al. 2010 (Paper available for free at this link). In this study by researchers in Vicenza Italy, 45 low-intermediate risk patients were treated with 35 Gy in 5 fractions. At a median follow-up of 20 months no patient has recurred biochemically and toxicity rates have been low.
• Hypofractionated stereotactic body radiotherapy in low-risk prostate adenocarcinoma: Preliminary results of a multi-institutional phase 1 feasibility trial. McBride SM, et al. 2011 Cancer In a phase 1, multi-institutional trial 45 patients with low-risk prostate cancer were treated with CyberKnife prostate SBRT delivering 36.35-37.5 Gy in 5 fractions. At a median follow-up of 44.5 months the 3-year biochemical failure-free rate was 97.7%, and toxicities were similar to other published studies of prostate SBRT.
• Stereotactic Body Radiotherapy as Monotherapy or Post-External Beam Radiotherapy Boost for Prostate Cancer: Technique, Early Toxicity, and PSA Response. Jabbari et al. 2010. University of California at San Francisco researchers present results on the first 38 patients treated with their CyberKnife System. They adopted a four-session treatment approach based on their successful experience with high dose-rate (HDR) brachytherapy—using the CyberKnife HDR-like dose distributions could be delivered non-invasively. At a median 18 months follow-up toxicity has been minimal and ”PSA response as defined by PSA nadir to date has been excellent.”
• Stereotactic body radiation therapy for low- and low-intermediate-risk prostate cancer: is there a dose effect? Katz A, et al. 2011 Front. Oncol Researchers from Flushing Radiation Oncology compare outcomes for prostate cancer patients treated with CyberKnife SBRT to a total dose of either 35 or 36.25 Gy in five daily fractions. At an overall median follow-up of 51 months both groups had a 97.5% freedom from biochemical failure rate. Overall toxicity was mild and comparable in both dose groups. The authors conclude “the highly favorable PSA response, limited biochemical failures, limited toxicity, and limited impact on quality of life in these low- to low-intermediate-risk patients are supportive of excellent long-term results for CyberKnife delivered SBRT”.
• Image-guided stereotactic body radiation therapy for localized prostate cancer. Kang JK, et al. 2011 Tumori Researchers from the Korea Institute of Radiological & Medical Sciences in Seoul, Korea treated 44 low-to-high risk prostate cancer patients using CyberKnife SBRT in 4-fraction regimens of 32 to 36 Gy. At a median follow-up of 40 months the biochemical failure-free rate was 100% in low-risk and intermediate-risk patients and 90.8% in high-risk patients, with no Grade 3 or higher toxicities.
• Acute toxicity after CyberKnife-delivered hypofractionated radiotherapy for treatment of prostate cancer. Townsend et al. 2010.# Researchers at Drexel University report on the treatment of 50 patients with early-to-intermediate, organ-confined prostate cancer using the CyberKnife System. Acute toxicity included 10% Grade 2 and 6% Grade 3 gastrourinary (GU) toxicities. No Grade 2 or higher acute gastrointestinal (GI) toxicities were reported. The authors state that "both GU and GI symptoms were comparable to or lower than those that have been reported for either IMRT or 3D-CRT and HDR brachytherapy".
• Sexual function after stereotactic body radiotherapy for prostate cancer: results of a prospective clinical trial. Wiegner EA, et al. 2010 Int J Radiat Oncol Biol Phys Stanford researchers examined erectile function preservation in prostate cancer patients treated as part of their Phase II CyberKnife SBRT trial. These patients represented the first group of patients treated using CyberKnife prostate SBRT prior to the use of MRI for contouring of the prostate and surrounding critical structures. Erectile function preservation at a median 35.5 months follow-up was 40% among the 32 patients in the study and 60% in those patients who were younger than 70 years.
• CyberKnife stereotactic radiotherapy as monotherapy for low- to intermediate-stage prostate cancer: early experience, feasibility, and tolerance. Aluwini S, et al. 2010 J Endourol Researchers from Daniel den Hoed Cancer Center, Rotterdam, The Netherlands, reported their early experience with 10 low-risk prostate cancer patients treated with CyberKnife SBRT delivering 38.5 Gy in 4 fractions. Mild-to-moderate urinary and rectal toxicity occurred early in some patients, but lessened over the first six months post-treatment.
• Virtual HDR CyberKnife treatment for localized prostatic carcinoma: dosimetry comparison with HDR brachytherapy and preliminary clinical observations. Fuller et al. 2008. Researchers from San Diego’s Radiosurgery Medial Group report that the CyberKnife System can achieve HDR-like dose distributions with excellent conformality and sharp dose fall off.
• Stereotactic body radiotherapy as boost for organ-confined prostate cancer. Katz et al. 2010. (Paper available for free at this link). Researcher from Winthrop University report on the treatment of 41 intermediate- and 32 high-risk localized prostate cancer patients using the CyberKnife System as a boost to EBRT. Three-year actuarial biochemical control rates were 89.5% for intermediate-risk and 77.7% for high-risk patients.

Review Papers

• CyberKnife radiosurgery for prostate cancer. Katz AJ. 2010 Technol Cancer Res Treat This review summarizes the motivating factors for the treatment of prostate cancer with CyberKnife SBRT. Also, presented is an evaluation of the current literature and discussion of the future of prostate cancer treatment with SBRT.
• Stereotactic body radiotherapy for prostate cancer: ready for prime time? Katz A. 2012 J Radiat Oncol (Paper available for free at this link). Prostate cancer radiobiology, innovations in image-guided radiotherapy technology, and a growing body of clinical evidence support the use of SBRT in the treatment of prostate cancer. In this paper Dr. Katz reviews literature on hypofractionated radiotherapy and SBRT, and concludes "Thus far, the results have demonstrated excellent control rates, low PSA nadirs, long time to PSA nadir and overall low morbidity suggesting a bright future for SBRT."

Pancreas

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• Stereotactic body radiotherapy and gemcitabine for locally advanced pancreatic cancer. Mahadevan et al. 2010. Researchers at Beth Israel Deaconess Medical Center and Harvard Medical School treated 36 patients with locally advanced pancreatic cancer using the CyberKnife System. At a median follow-up of 24 months the local control rate was 78% and the median overall survival time was 14.3 months.
• Image-guided stereotactic radiosurgery for locally advanced pancreatic adenocarcinoma: Results of first 85 patients. Didolkar et al. 2010. Sinai Hospital researchers treated 85 locally advanced and recurrent pancreatic adenocarcinoma patients with CyberKnife SRS. Pain relief was noted in majority of patients lasting for 18-24 weeks. Overall median survival from diagnosis was 18.6 months and from SRS it was 8.65 months.
• Gemcitabine chemotherapy and single-fraction stereotactic body radiotherapy for locally advanced pancreatic cancer. Schellenberg et al. 2008. Stanford University researchers found that combining gemcitabine chemotherapy with CyberKnife System treatment resulted in good local control, but that a significant rate of duodenal ulcers occurred.
• Phase II study to assess the efficacy of conventionally fractionated radiotherapy followed by a stereotactic radiosurgery boost in patients with locally advanced pancreatic cancer. Koong et al. 2005. Stanford University researchers found that concurrent IMRT and 5-FU followed by treatment with the CyberKnife System on patients with locally advanced pancreatic cancer results in excellent local control. Overall survival was not affected, and the combined treatment caused more toxicity than radiosurgery alone.
• Phase I study of stereotactic radiosurgery in patients with locally advanced pancreatic cancer. Koong et al. 2004. Stanford University researchers treated patients with locally advanced pancreatic cancer using the CyberKnife System. They found it was feasible to achieve local control without significant acute gastrointestinal toxicity using a dose of 25 Gy.

Liver

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• Image-Guided Robotic Stereotactic Body Radiation Therapy for Liver Metastases: Is There a Dose Response Relationship? Vautravers-Dewas et al. 2011. Researchers from Lille France report on the treatment of 42 liver metastases patients treated with the CyberKnife System at either 40 or 45 Gy in 3 fractions. Two-year actuarial local control was 90% and at last follow-up 66% of patients had a complete response. The authors conclude that “image-guided robotic stereotactic body radiation therapy is feasible, safe, and effective, with encouraging local control. It provides a strong alternative for patients who cannot undergo surgery.”
• Stereotactic radiotherapy of hepatocellular carcinoma: preliminary results. Louis et al. 2010 (Paper available for free at this link). Researchers from Lille France treated 25 patients with hepatocellular carcinoma who were not eligible for other treatment modalities with a total dose of 45 Gy in three fractions of 15 Gy each. Treatment was well tolerated with actuarial 1- and 2-year local control rates of 95% (95% CI: 69-95%). At a median overall follow-up of 12.7 months (range, 1-24 months), the results suggest promising therapeutic efficacy and good clinical tolerance.
• Dose-escalation study of single-fraction stereotactic body radiotherapy for liver malignancies. Goodman et al. 2010. Stanford University researchers treated 26 cancer patients with primary or metastatic liver tumors using the CyberKnife System in a dose-escalation study, in which single-fraction doses were raised from 18 Gy to 30 Gy. At a median follow-up of 17.3 months, the one-year local tumor control rate was 71%. Authors reported minimal acute and long-term toxicity.
• Frameless single-session robotic radiosurgery of liver metastases in colorectal cancer patients. Stintzing et al. 2010. Researchers at the University of Munich, Germany treated 14 patients with a total of 19 colorectal liver metastases using the CyberKnife System. At a median follow-up of 16.8 months, the one-year local control rate was 87% and the median progression-free survival was 9.2 months; no serious toxicities were noted.
• Stereotactic body radiation therapy with or without transarterial chemoembolization for patients with primary hepatocellular carcinoma: preliminary analysis. Choi et al. 2008. Korean researchers treated patients with early-stage hepatocellular carcinoma using the CyberKnife System only, and those with more advanced disease with accompanying portal vein thrombosis, using a combination of radiosurgery with the CyberKnife System and transarterial chemoembolization, with encouraging results.

Kidney

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• Initial evaluation of Cyberknife technology for extracorporeal renal tissue ablation. Ponsky et al. 2003. Researchers from the Cleveland Clinic Foundation used the CyberKnife System to treat pig kidneys. They were able to ablate target tissue while leaving nearby tissue undamaged.

Technical

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• Dose gradient gear target-normal structure interface for nonisocentric CyberKnife and isocentric intensity-modulated body radiotherapy for prostate cancer. Hossain et al. 2010. Researchers from the University of California San Francisco compared CyberKnife and IMRT treatment plans using identical contours and dose constraints. They obtained significantly superior conformality for CyberKnife plans with no differences in homogeneity. Rectal V30% and V40% were significantly lower for CyberKnife plans; dose fall-off toward the rectum was more rapid for the CyberKnife plans than for IMRT. "One key advantage of CKS delivery is its capability to track on-line target motions to a high degree of precision."
• Patient motion and targeting accuracy in robotic spinal radiosurgery: 260 single-fraction fiducial-free cases. Furweger et al., 2010. In this study, Munich researchers used clinical patient data from 260 spine patients treated with the CyberKnife System to perform a retrospective analysis of Xsight Spine Tracking performance. Tumors from all spinal levels, and patients with a wide range of clinical conditions were included. Authors obtained an overall median targeting error 0.48 mm. They also examined whether error in dose placement would result from observed tracking error. They concluded, “Patient motion has little effect on the delivered dose distribution when image-guided correction of beam aiming is employed.”
• Clinical accuracy of the respiratory tumor tracking system of the CyberKnife: assessment by analysis of log files. Hoogeman et al. 2009. The Synchrony Respiratory Tracking System provides a significant reduction in PTV margins, and therefore the treated volume, compared with non-tracking treatment delivery.
• Performance evaluation of a CyberKnife G4 image-guided robotic stereotactic radiosurgery system. Antypas et al. 2008. Authors from the Department of Radiology, Aretaieion Hospital, University of Athens, Greece, describe in detail their experience with installation of quality assurance of the CyberKnife G4 System. Repeated tests showing sub-millimetric targeting accuracy are highlights of this paper.
• Intrafractional motion of the prostate during hypofractionated radiotherapy. Xie et al. 2008. In a collaboration between Stanford and UCSF researchers, considerable prostate motion was detected during treatment between X-ray acquisitions. Authors recommend imaging about every 40 seconds to maintain sub-millimetric accuracy.
• Dosimetric investigation of lung tumor motion compensation with a robotic respiratory tracking system: An experimental study. Nioutsikou et al. 2008. Researchers from the United Kingdom present an investigation of the ability of the Synchrony Respiratory Motion Tracking System to correct for tumor motion due to respiration. A reduction in dose misplacement due to movement was found with motion tracking, such that dosimetry for the motion-tracked case approximated that for the no-motion case.
• A fast, accurate, and automatic 2D-3D image registration for image-guided cranial radiosurgery. Fu et al. 2008. Researchers at Accuray Incorporated demonstrate that sub-millimetric accuracy for intracranial targets can be obtained with their 6D image registration algorithm.
• Four-dimensional stereotactic radiotherapy for early stage non-small cell lung cancer: a comparative planning study. Prevost et al. 2008. Researchers from the Netherlands compared CyberKnife System lung radiosurgery using the Synchrony Respiratory Motion Tracking System to a conventionally fractionated 3D conformal radiotherapy (3D-CRT) method, and concluded that the Synchrony system allows safe dose escalation to moving targets.
• Quantitative measurement of CyberKnife robotic arm steering. Wong et al. 2007. Researchers from Georgetown University demonstrate that the Synchrony® Respiratory Motion Tracking System of the CyberKnife System tracks simulated lung tumors with 0.43-0.60 mm precision and a tracking variability of 0.14-0.20 mm.
• A study of the accuracy of Cyberknife spinal radiosurgery using skeletal structure tracking. Ho et al. 2007. This study measured the accuracy of the Xsight Spine Tracking System which allows tracking of skeletal structures without the need for implanted fiducials. The measured total system error was 0.61 mm and the total tracking system error was 0.49 mm.
• CyberKnife radiosurgery in the treatment of complex skull base tumors: analysis of treatment planning parameters. Collins et al. 2006. Researchers from Georgetown University obtained CyberKnife System treatment plans with good conformality and homogeneity for oddly shaped lesions in the sensitive skull base region.
• Technical description, phantom accuracy, and clinical feasibility for fiducial-free frameless real-time image-guided spinal radiosurgery. Muacevic et al. 2006. Researchers from Munich, Germany demonstrate using phantom tests that the Xsight Spine Tracking System is accurate to within about 0.5 mm. They conclude that fiducial-free tracking is a feasible, accurate and reliable approach to non-invasive spine radiosurgery.