8+ Year Performance of the Gamma Knife Perfexion/Icon Patient Positioning System and Possibilities for Preemptive Fault Detection Using Statistical Process Control.

Background: The large fractional doses, steep dose gradients, and small targets found in intracranial radiosurgery require extremely low beam delivery uncertainty. In the case of Gamma Knife radiosurgery (GKRS), this includes minimizing patient positioning system (PPS) positioning uncertainty. Existing QA techniques are recipe based, and feature point in time pass/fail tolerances.

Spatial shifts in frame-based Gamma Knife radiosurgery: A case for cone beam CT imaging as quality assurance using the Gamma Knife® Icon™.

Background: Cone beam CT (CBCT) imaging has been integrated into the most recent version of the Leksell Gamma Knife for the primary purpose to facilitate fractionated therapy.

Case Description: This case study presents three patients where the CBCT system of the Gamma Knife Icon discovered potentially clinically significant frame shifts. In each case, patients were imaged with volumetric MR prior to stereotactic frame placement.

Dosimetric effects of Onyx embolization on Gamma Knife arteriovenous malformation dose distributions.

OBJECTIVE Patients with arteriovenous malformations (AVMs) treated with Gamma Knife radiosurgery (GKRS) subsequent to embolization suffer from elevated local failure rates and differences in adverse radiation effects. Onyx is a common embolic material for AVMs. Onyx is formulated with tantalum, a high atomic number (Z = 73) element that has been investigated as a source of dosimetric uncertainty contributing to the less favorable clinical results.

Variability in spine radiosurgery treatment planning - results of an international multi-institutional study.

Background: The aim of this study was to quantify the variability in spinal radiosurgery (SRS) planning practices between five international institutions, all member of the Elekta Spine Radiosurgery Research Consortium.

Methods: Four institutions provided one representative patient case each consisting of the medical history, CT and MR imaging. A step-wise planning approach was used where, after each planning step a consensus was generated that formed the basis for the next planning step.

Safety and feasibility of STAT RAD: Improvement of a novel rapid tomotherapy-based radiation therapy workflow by failure mode and effects analysis.

Purpose: The clinical challenge of radiation therapy (RT) for painful bone metastases requires clinicians to consider both treatment efficacy and patient prognosis when selecting a radiation therapy regimen. The traditional RT workflow requires several weeks for common palliative RT schedules of 30 Gy in 10 fractions or 20 Gy in 5 fractions. At our institution, we have created a new RT workflow termed "STAT RAD" that allows clinicians to perform computed tomographic (CT) simulation, planning, and highly conformal single fraction treatment delivery within 2 hours.

Cranial nerve dysfunction following Gamma Knife surgery for pituitary adenomas: long-term incidence and risk factors.

Object: Gamma Knife surgery (GKS) has become a significant component of neurosurgical treatment for recurrent secretory and nonsecretory pituitary adenomas. Although the long-term risks of visual dysfunction following microsurgical resection of pituitary adenomas has been well studied, the comparable risk following radiosurgery is not well defined. This study evaluates the long-term risks of ophthalmological dysfunction following GKS for recurrent pituitary adenomas.

Initial experience with the eXtend System: a relocatable frame system for multiple-session gamma knife radiosurgery.

Objective: To present our initial experience with the Elekta eXtend System, a relocatable frame system for multiple-fraction or serial multiple-session radiosurgery.

Methods: The eXtend System comprises a carbon-fiber frame system known as the eXtend Frame, a vacuum cushion, and a vacuum pump/vacuum surveillance system. The eXtend Frame comprises a carbon-fiber frame, a mouthpiece with dental impression, and a configurable front-piece that accepts the mouthpiece and rigidly attaches to the carbon-fiber frame.

Leksell GammaPlan version 10.0 preview: performance of the new inverse treatment planning algorithm applied to Gamma Knife surgery for pituitary adenoma.

Object: Treatment planning for Gamma Knife surgery has traditionally been a forward planning (FP)-only approach with results that depend significantly on the experience of the user. Leksell GammaPlan version 10.0, currently in beta testing, introduces a new inverse planning (IP) engine that may allow more reproducible results across dosimetrists and individual institutions.

Gamma Knife surgery for arteriovenous malformations in children.

Object: The aim of this study was to evaluate the long-term imaging and clinical outcomes of intracranial arteriovenous malformations (AVMs) in children treated with Gamma Knife surgery (GKS).

Methods: Between 1989 and 2007, 200 patients with AVMs who were 18 years of age or younger were treated at the University of Virginia Health System. Excluding 14 patients who had not reached 2-year follow-up, 186 patients comprised this study.

Stereotactic body radiation therapy: the report of AAPM Task Group 101.

Task Group 101 of the AAPM has prepared this report for medical physicists, clinicians, and therapists in order to outline the best practice guidelines for the external-beam radiation therapy technique referred to as stereotactic body radiation therapy (SBRT). The task group report includes a review of the literature to identify reported clinical findings and expected outcomes for this treatment modality. Information is provided for establishing a SBRT program, including protocols, equipment, resources, and QA procedures.

Gamma knife radiosurgery for brain metastasis of nonsmall cell lung cancer: is there a difference in outcome between morning and afternoon treatment?

Background: Circadian cell-cycle progression causes fluctuating radiosensitivity in many tissues, which could affect clinical outcomes. The purpose of this study was to determine whether outcomes of single-session gamma knife radiosurgery (GKRS) for metastatic nonsmall cell lung cancer (NSCLC) differ based on treatment time.

Methods: Fifty-eight patients received GKRS between 10:00 am and 12:30 pm and 39 patients received GKRS between 12:30 pm and 3:00 pm.

Timing and risk factors for new brain metastasis formation in patients initially treated only with Gamma Knife surgery. Clinical article.

Object: Stereotactic radiosurgery has been shown to afford a reasonable chance of local tumor control. However, new brain metastasis can arise following successful local tumor control from radiosurgery. This study evaluates the timing, number, and risk factors for development of subsequent new brain metastasis in a group of patients treated with stereotactic radiosurgery alone.

Survey on human papillomavirus/p16 screening use in oropharyngeal carcinoma patients in the United States.

Background: Patients with human papillomavirus (HPV)-positive oropharyngeal carcinoma (OC) have better prognosis than patients with HPV-negative OC. The objective of the current study was to assess how different practices across the United States treat patients with OC with respect to screening for HPV DNA or p16.

Methods: Five hundred forty-two randomly selected radiation oncologists were sent an 11-question survey by email regarding the use of HPV/p16 screening in OC.

Tracking brain motion during the cardiac cycle using spiral cine-DENSE MRI.

Cardiac-synchronized brain motion is well documented, but the accurate measurement of such motion on the pixel-by-pixel basis has been hampered by the lack of proper imaging technique. In this article, the authors present the implementation of an autotracking spiral cine displacement-encoded stimulation echo (DENSE) magnetic resonance imaging (MRI) technique for the measurement of pulsatile brain motion during the cardiac cycle. Displacement-encoded dynamic MR images of three healthy volunteers were acquired throughout the cardiac cycle using the spiral cine-DENSE pulse sequence gated to the R wave of an electrocardiogram.

Gamma Knife surgery for brain metastases from gastrointestinal cancer.

Object: Brain metastases from gastrointestinal cancers are rare. However, the incidence is increasing because patients with gastrointestinal carcinoma tend to live longer due to earlier diagnosis and more effective treatment of systemic disease. The purpose of this study was to evaluate the efficacy of Gamma Knife surgery (GKS) for the treatment of brain metastases from gastrointestinal cancers.

Anniversary Paper: the role of medical physicists in developing stereotactic radiosurgery.

This article is a tribute to the pioneering medical physicists over the last 50 years who have participated in the research, development, and commercialization of stereotactic radiosurgery (SRS) and stereotactic radiotherapy utilizing a wide range of technology. The authors have described the evolution of SRS through the eyes of physicists from its beginnings with the Gamma Knife in 1951 to proton and charged particle therapy; modification of commercial linacs to accommodate high precision SRS setups; the multitude of accessories that have enabled fine tuning patients for relocalization, immobilization, and repositioning with submillimeter accuracy; and finally the emerging technology of SBRT. A major theme of the article is the expanding role of the medical physicist from that of advisor to the neurosurgeon to the current role as a primary driver of new technology that has already led to an adaptation of cranial SRS to other sites in the body, including, spine, liver, and lung.

Role of RecA in DNA damage repair in Deinococcus radiodurans.

It has been shown previously that the RecA protein of Deinococcus radiodurans plays a unique role in the repair of DNA damage in this highly DNA damage-resistant organism. Despite the high level of amino-acid identity, previous work has shown that Escherichia coli RecA does not complement D. radiodurans RecA mutants, further suggesting the uniqueness of D.

Possible origins of CTnBST, a conjugative transposon found recently in a human colonic Bacteroides strain.

A previous survey of Bacteroides isolates suggested that the ermB gene entered Bacteroides spp. recently. Previously, ermB had been found almost exclusively in gram-positive bacteria.