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Peter Keuschnigg, Daniel Kellner, Karl Fritscher, Andrea Zechner, Ulrich Mayer, Philipp Huber, Felix Sedlmayer, Heinz Deutschmann, Philipp Steininger
PURPOSE: Couch-mounted cone-beam computed tomography (CBCT) imaging devices with independently rotatable x-ray source and flat-panel detector arms for acquisitions of arbitrary regions of interest (ROI) have recently been introduced in image-guided radiotherapy (IGRT). This work analyzes mechanical limitations and gravity-induced effects influencing the geometric accuracy of images acquired with arbitrary angular constellations of source and detector in nonisocentric trajectories, which is considered essential for IGRT...
January 2017: Medical Physics
M Nakayama, Y Munetomo, T Ogata, K Uehara, S Tsudou, H Nishimura, H Mayahara, R Sasaki
PURPOSE: To evaluate the practicality use of ionization chambers with different volumes for delivery quality assurance of CyberKnife plans, METHODS: Dosimetric measurements with a spherical solid water phantom and three ionization chambers with volumes of 0.13, 0.04, and 0.01 cm3 (IBA CC13, CC04, and CC01, respectively) were performed for various CyberKnife clinical treatment plans including both isocentric and nonisocentric delivery. For each chamber, the ion recombination correction factors <I>Ks</I> were calculated using the Jaffe plot method and twovoltage method at a 10-cm depth for a 60-mm collimator field in a water phantom...
June 2016: Medical Physics
I Zhang, J Antone, L Vijeh, J Li, J Lauritano, M Marrero, S Saha, A Goenka, H D Zinkin, J P S Knisely
No abstract text is available yet for this article.
October 1, 2016: International Journal of Radiation Oncology, Biology, Physics
Jieming Liang, Todd Atwood, Rie von Eyben, Benjamin Fahimian, Erika Chin, Kathleen Horst, Karl Otto, Dimitre Hristov
PURPOSE: To develop planning and delivery capabilities for linear accelerator-based nonisocentric trajectory modulated arc therapy (TMAT) and to evaluate the benefit of TMAT for accelerated partial breast irradiation (APBI) with the patient in prone position. METHODS AND MATERIALS: An optimization algorithm for volumetrically modulated arc therapy (VMAT) was generalized to allow for user-defined nonisocentric TMAT trajectories combining couch rotations and translations...
August 1, 2015: International Journal of Radiation Oncology, Biology, Physics
Brian Winey, Marc Bussiere
The purpose of this study was to determine the effects of geometric uncertainties of patient position on treatments of multiple nonisocentric intracranial lesions. The average distance between lesions in patients with multiple targets was determined by a retrospective survey of patients with multiple lesions. Retrospective patient imaging data from fractionated stereotactic patients were used to calculate interfractional and intrafractional patient position uncertainty. Three different immobilization devices were included in the positioning study...
May 8, 2014: Journal of Applied Clinical Medical Physics
Ruijiang Li, Lei Xing, Kathleen C Horst, Karl Bush
PURPOSE: To propose a nonisocentric treatment strategy as a special form of station parameter optimized radiation therapy, to improve sparing of critical structures while preserving target coverage in breast radiation therapy. METHODS AND MATERIALS: To minimize the volume of exposed lung and heart in breast irradiation, we propose a novel nonisocentric treatment scheme by strategically placing nonconverging beams with multiple isocenters. As its name suggests, the central axes of these beams do not intersect at a single isocenter as in conventional breast treatment planning...
March 15, 2014: International Journal of Radiation Oncology, Biology, Physics
Lejing Wang, Pascal Fallavollita, Rui Zou, Xin Chen, Simon Weidert, Nassir Navab
For trauma and orthopedic surgery, maneuvering a mobile C-arm fluoroscope into a desired position to acquire an X-ray is a routine surgical task. The precision and ease of use of the C-arm becomes even more important for advanced interventional imaging techniques such as parallax-free X-ray image stitching. Today's standard mobile C-arms have been modeled with only five degrees of freedom (DOF), which definitely restricts their motions in 3-D Cartesian space. In this paper, we present a method to model both the mobile C-arm and patient's table as an integrated kinematic chain having six DOF without constraining table position...
May 2012: IEEE Transactions on Medical Imaging
Anuj V Peddada, D James Sceats, Gerald A White, Gyongyver Bulz, Greg L Gibbs, Barry Switzer, Susan Anderson, Alan T Monroe
This case report of 74-year-old man with trigeminal neuralgia is presented to underscore the importance of evaluating the entire treatment plan, especially when delivering large doses where even a low percentage of the prescription dose can contribute a substantial dose to an unintended target. The patient was treated using the CyberKnife stereotactic radiosurgery system utilizing a nonisocentric beam treatment plan with a 5-mm fixed collimator generating 111 beams to deliver 6000 cGy to the 79% isodose line with a maximum dose of 7594 cGy to the target...
November 2011: Journal of Neurosurgery
Sonja Dieterich, Iris C Gibbs
The CyberKnife system deploys a linac mounted on an agile robot and directed under image guidance for stereotactic radiotherapy using nonisocentric beam delivery. A design advantage of the CyberKnife system is its method of active image guidance during treatment delivery. Recent developments in the hardware and software of the system have significantly enhanced its functionality: (a) an optimized path traversal process significantly reduces the robot motion time, resulting in reductions of overall treatment times of at least 5-10 min; (b) to optimize the accuracy of dose calculation in CyberKnife planning/delivery, Monte Carlo algorithms have been introduced; (c) the new IRIS collimator reduces the monitor units required, increases treatment speed and improves conformality and homogeneity of treatment plans; (d) XSight lung tracking, an algorithm for fiducial-less lung tracking, has been developed for peripheral, radio-dense lung tumors with diameters >15 mm; and (e) a sequential optimization planning process incorporates a more flexible approach to optimize the multiple, complex treatment planning criteria used today...
2011: Frontiers of Radiation Therapy and Oncology
Steven van de Water, Mischa S Hoogeman, Sebastiaan Breedveld, Joost J M E Nuyttens, Dennis R Schaart, Ben J M Heijmen
PURPOSE: Compared with many small circular beams used in CyberKnife treatments, beam's eye view-shaped fields are generally more time-efficient for dose delivery. However, beam's eye view-shaping devices, such as a mini-multileaf collimator (mMLC), are not presently available for CyberKnife, although a variable-aperture collimator (Iris, 12 field diameters; 5-60 mm) is available. We investigated whether the Iris can mimic noncoplanar mMLC treatments using a limited set of principal beam orientations (nodes) to produce time-efficient treatment plans...
November 1, 2011: International Journal of Radiation Oncology, Biology, Physics
Martina Descovich, Penny K Sneed, Nicholas M Barbaro, Michael W McDermott, Cynthia F Chuang, Igor J Barani, Jean L Nakamura, Ma Lijun
OBJECT: The Leksell Gamma Knife and the Accuray CyberKnife systems have been used in the radio surgical treatment of trigeminal neuralgia. The 2 techniques use different delivery methods and different treatment parameters. In the past, CyberKnife treatments have been associated with an increased incidence of treatment-related complications, such as facial numbness. The goal of this study was to develop a method for planning a CyberKnife treatment for trigeminal neuralgia that would reproduce the dosimetric characteristics of a Gamma Knife plan...
December 2010: Journal of Neurosurgery
Danny Y Song, Ameet K Jain, Zhe Zhang, Anton Deguet, Yi Le, Elwood Armour, E Clif Burdette, Gabor Fichtinger
PURPOSE: To evaluate a prototypical system of dynamic intraoperative dosimetry for prostate brachytherapy using registered ultrasound and fluoroscopy (RUF) with a nonisocentric C-arm (GE OEC, Salt Lake City, UT) and to compare intraoperative dosimetry of RUF as well as ultrasound-based seed localization (USD) with Day 0 CT dosimetry. METHODS: Seed positions were independently determined using RUF and USD. RUF uses a radio-opaque fiducial for registration to ultrasound and 3-dimensional reconstruction of seeds relative to prostate using nonisocentric C-arm fluoroscopy...
March 2011: Brachytherapy
Lijun Ma, Arjun Sahgal, Martina Descovich, Young-Bin Cho, Cynthia Chuang, Kim Huang, Normand J Laperriere, Dennis C Shrieve, David A Larson
PURPOSE: To investigate whether dose fall-off characteristics would be significantly different among intracranial radiosurgery modalities and the influence of these characteristics on fractionation schemes in terms of normal tissue sparing. METHODS AND MATERIALS: An analytic model was developed to measure dose fall-off characteristics near the target independent of treatment modalities. Variations in the peripheral dose fall-off characteristics were then examined and compared for intracranial tumors treated with Gamma Knife, Cyberknife, or Novalis LINAC-based system...
March 1, 2010: International Journal of Radiation Oncology, Biology, Physics
Sabbir Hossain, Ping Xia, Kim Huang, Martina Descovich, Cynthia Chuang, Alexander R Gottschalk, Mack Roach, Lijun Ma
PURPOSE: The treatment planning quality between nonisocentric CyberKnife (CK) and isocentric intensity modulation treatment was studied for hypofractionated prostate body radiotherapy. In particular, the dose gradient across the target and the critical structures such as the rectum and bladder was characterized. METHODS AND MATERIALS: In the present study, patients treated with CK underwent repeat planning for nine fixed-field intensity-modulated radiotherapy (IMRT) using identical contour sets and dose-volume constraints...
September 1, 2010: International Journal of Radiation Oncology, Biology, Physics
John R Adler, Regina Bower, Gaurav Gupta, Michael Lim, Allen Efron, Iris C Gibbs, Steven D Chang, Scott G Soltys
OBJECTIVE: Although stereotactic radiosurgery is an established procedure for treating trigeminal neuralgia (TN), the likelihood of a prompt and durable complete response is not assured. Moreover, the incidence of facial numbness remains a challenge. To address these limitations, a new, more anatomic radiosurgical procedure was developed that uses the CyberKnife (Accuray, Inc., Sunnyvale, CA) to lesion an elongated segment of the retrogasserian cisternal portion of the trigeminal sensory root...
February 2009: Neurosurgery
Marco Lee, M Yashar S Kalani, Samuel Cheshier, Iris C Gibbs, John R Adler, Steven D Chang
OBJECT: Many benign intracranial tumors are amenable to radiotherapy treatment including meningiomas, schwannomas, pituitary tumors, and craniopharyngiomas. The authors present their experience in the treatment of craniopharyngiomas in 16 patients using frameless CyberKnife stereotactic radiosurgery (SRS). The authors discuss the role of radiation therapy in the management of these tumors, and more specifically, the role of CyberKnife SRS. METHODS: Sixteen patients were treated for residual or recurrent craniopharyngioma between 2000 and 2007 with CyberKnife SRS at Stanford University Medical Center...
2008: Neurosurgical Focus
Achim Schweikard, Alexander Schlaefer, John R Adler
By design, the range of beam directions in conventional radiosurgery are constrained to an isocentric array. However, the recent introduction of robotic radiosurgery dramatically increases the flexibility of targeting, and as a consequence, beams need be neither coplanar nor isocentric. Such a nonisocentric design permits a large number of distinct beam directions to be used in one single treatment. These major technical differences provide an opportunity to improve upon the well-established principles for treatment planning used with GammaKnife or LINAC radiosurgery...
November 2006: Medical Physics
Jeno Palvolgyi
In our institution we have introduced the variable angle reconstruction method with a nonisocentric C-arm as brachytherapy localizer in gynecological treatments. The main advantage of this method is that on the posterior oblique images the ovoids of the Fletcher-Suit-Delclos (FSD) applicator are clearly separated. The main problem with the nonisocentric machine is that the magnification factor is not known exactly and varies with the C-arm angle. For generation of treatment plans with a commercial brachytherapy planning system the magnification factors of the reconstruction images have to be determined previously...
January 2006: Medical Physics
Joseph Stancanello, Carlo Cavedon, Paolo Francescon, Pietro Cerveri, Giancarlo Ferrigno, Federico Colombo, Stefano Perini
In this paper a novel technique is proposed and validated for radiosurgery treatment planning of arteriovenous malformations (AVMs). The technique was developed for frameless radiosurgery by means of the CyberKnife, a nonisocentric, linac-based system which allows highly conformed isodose surfaces to be obtained, while also being valid for other treatment strategies. The technique is based on registration between computed tomography (CT) and three-dimensional rotational angiography (3DRA). Tests were initially performed on the effectiveness of the correction method for distortion offered by the angiographic system...
June 2004: Medical Physics
S D Chang, J R Adler
The field of stereotactic radiosurgery is rapidly advancing as a result of both improvements in radiosurgical equipment and better physician understanding of the clinical applications of stereotactic radiosurgery. This article will review recent developments in the field of radiosurgery, including advances in our understanding of the treatment of brain metastases and arteriovenous malformations, as well as the use of stereotactic radiosurgery as a boost following conventional radiation for nasopharyngeal carcinoma to minimize the rate of local recurrence...
February 2001: Oncology (Williston Park, NY)
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