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https://www.readbyqxmd.com/read/28297462/surface-dose-variations-in-6-and-10-mv-flattened-and-flattening-filter-free-fff-photon-beams
#1
Jason Cashmore
As the use of linear accelerators operating in flattening filter-free (FFF) modes becomes more widespread, it is important to have an understanding of the surface doses delivered to patients with these beams. Flattening filter removal alters the beam quality and relative contributions of low-energy X-rays and contamination electrons in the beam. Having dosimetric data to describe the surface dose and buildup regions under a range of conditions for FFF beams is important if clinical decisions are to be made...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297443/comparison-of-automatic-image-registration-uncertainty-for-three-igrt-systems-using-a-male-pelvis-phantom
#2
Jeffrey Barber, Jonathan R Sykes, Lois Holloway, David I Thwaites
A series of phantom images using the CIRS Virtual Human Male Pelvis was acquired across available dose ranges for three image-guided radiotherapy (IGRT) imaging systems: Elekta XVI CBCT, Varian TrueBeam CBCT, and TomoTherapy MV CT. Each image was registered to a fan-beam CT within the XVI software 100 times with random initial offsets. The residual registration error was analyzed to assess the role of imaging hardware and reconstruction in the uncertainty of the IGRT process. Residual translation errors were similar for all systems and <0...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297419/radiation-leakage-dose-from-elekta-electron-collimation-system
#3
Garrett M Pitcher, Kenneth R Hogstrom, Robert L Carver
This study provided baseline data required for a greater project, whose objective was to design a new Elekta electron collimation system having significantly lighter electron applicators with equally low out-of field leakage dose. Specifically, off-axis dose profiles for the electron collimation system of our uniquely configured Elekta Infinity accelerator with the MLCi2 treatment head were measured and calculated for two primary purposes: 1) to evaluate and document the out-of-field leakage dose in the patient plane and 2) to validate the dose distributions calculated using a BEAMnrc Monte Carlo (MC) model for out-of-field dose profiles...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297340/dosimetric-properties-of-equivalent-quality-flattening-filter-free-fff-and-flattened-photon-beams-of-versa-hd-linear-accelerator
#4
Mukesh N Meshram, Srimanta Pramanik, C P Ranjith, Saravana K Gopal, Rishabh Dobhal
This study presents the basic dosimetric properties of photon beams of a Versa HD linear accelerator (linac), which is capable of delivering flattening filter-free (FFF) beams with a beam quality equivalent to the corresponding flattened beams based on comprehensive beam data measurement. The analyzed data included the PDDs, profiles, penumbra, out-of-field doses, surface doses, output factors, head and phantom scatter factors, and MLC transmissions for both FFF and flattened beams of 6 MV and 10 MV energy from an Elekta Versa HD linac...
May 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297337/one-year-analysis-of-elekta-cbct-image-quality-using-nps-and-mtf
#5
Satomi Nakahara, Masayuki Tachibana, Yoichi Watanabe
The image quality (IQ) of imaging systems must be sufficiently high for image-guided radiation therapy (IGRT). Hence, users should implement a quality assurance program to maintain IQ. In our routine IQ tests of the kV cone-beam CT system (Elekta XVI), image noise was quantified by noise standard deviation (NSD), which was the standard deviation of CT numbers measured in a small area in an image of an IQ test phantom (Catphan), and the high spatial resolution (HSR) was evaluated by the number of line-pairs (LPN) visually recognizable in the image...
May 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297327/small-field-detector-correction-factors-effects-of-the-flattening-filter-for-elekta-and-varian-linear-accelerators
#6
Madelaine K Tyler, Paul Z Y Liu, Christopher Lee, David R McKenzie, Natalka Suchowerska
Flattening filter-free (FFF) beams are becoming the preferred beam type for stereotactic radiosurgery (SRS) and stereotactic ablative radiation therapy (SABR), as they enable an increase in dose rate and a decrease in treatment time. This work assesses the effects of the flattening filter on small field output factors for 6 MV beams generated by both Elekta and Varian linear accelerators, and determines differences between detector response in flattened (FF) and FFF beams. Relative output factors were measured with a range of detectors (diodes, ionization chambers, radiochromic film, and microDiamond) and referenced to the relative output factors measured with an air core fiber optic dosimeter (FOD), a scintillation dosimeter developed at Chris O'Brien Lifehouse, Sydney...
May 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297319/modeling-the-agility-mlc-in-the-monaco-treatment-planning-system
#7
Michael Snyder, Robert Halford, Cory Knill, Jeffrey N Adams, Todd Bossenberger, Adrian Nalichowski, Ahmad Hammoud, Jay Burmeister
We investigate the relationship between the various parameters in the Monaco MLC model and dose calculation accuracy for an Elekta Agility MLC. The vendor-provided MLC modeling procedure - completed first with external vendor participation and then exclusively in-house - was used in combination with our own procedures to investigate several sets of MLC modeling parameters to determine their effect on dose distributions and point-dose measurements. Simple plans provided in the vendor procedure were used to elucidate specific mechanical characteristics of the MLC, while ten complex treatment plans - five IMRT and five VMAT - created using TG-119-based structure sets were used to test clinical dosimetric effects of particular parameter choices...
May 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297304/evaluation-of-kidney-motion-and-target-localization-in-abdominal-sbrt-patients
#8
Marcus Sonier, William Chu, Nafisha Lalani, Darby Erler, Patrick Cheung, Renee Korol
The purpose of this study was to evaluate bilateral kidney and target translational/rotational intrafraction motion during stereotactic body radiation therapy treatment delivery of primary renal cell carcinoma and oligometastatic adrenal lesions for patients immobilized in the Elekta BodyFIX system. Bilateral kidney motion was assessed at midplane for 30 patients immobilized in a full-body dual-vacuum-cushion system with two patients immobilized via abdominal compression. Intrafraction motion was assessed for 15 patients using kilovoltage cone-beam computed tomography (kV-CBCT) datasets (n=151) correlated to the planning CT...
November 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297303/experimental-evaluation-of-a-gpu-based-monte-carlo-dose-calculation-algorithm-in-the-monaco-treatment-planning-system
#9
Moti R Paudel, Anthony Kim, Arman Sarfehnia, Sayed B Ahmad, David J Beachey, Arjun Sahgal, Brian M Keller
A new GPU-based Monte Carlo dose calculation algorithm (GPUMCD), developed by the vendor Elekta for the Monaco treatment planning system (TPS), is capable of modeling dose for both a standard linear accelerator and an Elekta MRI linear accelerator. We have experimentally evaluated this algorithm for a standard Elekta Agility linear accelerator. A beam model was developed in the Monaco TPS (research version 5.09.06) using the commissioned beam data for a 6 MV Agility linac. A heterogeneous phantom representing several scenarios - tumor-in-lung, lung, and bone-in-tissue - was designed and built...
November 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297279/difference-in-performance-between-3d-and-4d-cbct-for-lung-imaging-a-dose-and-image-quality-analysis
#10
Sheeba Thengumpallil, Kathleen Smith, Pascal Monnin, Jean Bourhis, François Bochud, Raphaël Moeckli
The study was to describe and to compare the performance of 3D and 4D CBCT imaging modalities by measuring and analyzing the delivered dose and the image quality. The 3D (Chest) and 4D (Symmetry) CBCT Elekta XVI lung IGRT protocols were analyzed. Dose profiles were measured with TLDs inside a dedicated phantom. The dosimetric indicator cone-beam dose index (CBDI) was evaluated. The image quality analysis was performed by assessing the contrast transfer function (CTF), the noise power spectrum (NPS) and the noise-equivalent quanta (NEQ)...
November 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297276/rounded-leaf-end-modeling-in-pinnacle-vmat-treatment-planning-for-fixed-jaw-linacs
#11
Lori A Young, Fei Yang, Ning Cao, Juergen Meyer
During volume-modulated arc therapies (VMAT), dosimetric errors are introduced by multiple open dynamic leaf gaps that are present in fixed diaphragm linear accelerators. The purpose of this work was to develop a methodology for adjusting the rounded leaf end modeling parameters to improve out-of-field dose agreement in SmartArc VMAT treatment plans delivered by fixed jaw linacs where leaf gap dose is not negligible. Leaf gap doses were measured for an Elekta beam modulator linac with 0.4 cm micro-multileaf collimators (MLC) using an A16 micro-ionization chamber, a MatriXX ion chamber detector array, and Kodak EDR2 film dosimetry in a solid water phantom...
November 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28296328/out-of-field-doses-and-neutron-dose-equivalents-for-electron-beams-from-modern-varian-and-elekta-linear-accelerators
#12
Carlos E Cardenas, Paige L Nitsch, Rajat J Kudchadker, Rebecca M Howell, Stephen F Kry
Out-of-field doses from radiotherapy can cause harmful side effects or eventually lead to secondary cancers. Scattered doses outside the applicator field, neutron source strength values, and neutron dose equivalents have not been broadly investigated for high-energy electron beams. To better understand the extent of these exposures, we measured out-of-field dose characteristics of electron applicators for high-energy electron beams on two Varian 21iXs, a Varian TrueBeam, and an Elekta Versa HD operating at various energy levels...
July 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28291912/improving-the-efficiency-of-breast-radiotherapy-treatment-planning-using-a-semi-automated-approach
#13
Robert A Mitchell, Philip Wai, Ruth Colgan, Anna M Kirby, Ellen M Donovan
OBJECTIVES: To reduce treatment planning times while maintaining plan quality through the introduction of semi-automated planning techniques for breast radiotherapy. METHODS: Automatic critical structure delineation was examined using the Smart Probabilistic Image Contouring Engine (SPICE) commercial autosegmentation software (Philips Radiation Oncology Systems, Fitchburg, WI) for a cohort of ten patients. Semiautomated planning was investigated by employing scripting in the treatment planning system to automate segment creation for breast step-and-shoot planning and create objectives for segment weight optimization; considerations were made for three different multileaf collimator (MLC) configurations...
January 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28291908/does-gated-beam-delivery-impact-delivery-accuracy-on-an-elekta-linac
#14
Mohammed Jermoumi, Roger Xie, Daliang Cao, David J Housley, David M Shepard
In this study, we evaluated the performance of an Elekta linac in the delivery of gated radiotherapy. Delivery accuracy was examined with an emphasis on the impact of using short gating windows (low monitor unit beam-on segments) or long beam hold times. The performance was assessed using a 20cm by 20cm open field with the radiation delivered using a range of beam-on and beam-off time periods. Gated delivery measurements were also performed for two SBRT plans delivered using volumetric modulated arc therapy (VMAT)...
January 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28279147/dosimetric-comparison-and-evaluation-of-4-stereotactic-body-radiotherapy-techniques-for-the-treatment-of-prostate-cancer
#15
Jan Seppälä, Sami Suilamo, Mikko Tenhunen, Liisa Sailas, Heli Virsunen, Erna Kaleva, Jani Keyriläinen
PURPOSE: The aim of this study was to compare dosimetric characteristics, monitor unit, and delivery efficiency of 4 different stereotactic body radiotherapy techniques for the treatment of prostate cancer. METHODS: This study included 8 patients with localized prostate cancer. Dosimetric assets of 4 delivery techniques for stereotactic body radiotherapy were evaluated: robotic CyberKnife, noncoplanar intensity-modulated radiotherapy, and 2 intensity-modulated arc therapy techniques (RapidArc and Elekta volumetric-modulated arc therapy)...
April 2017: Technology in Cancer Research & Treatment
https://www.readbyqxmd.com/read/28273357/energy-and-field-size-dependence-of-a-silicon-diode-designed-for-small-field-dosimetry
#16
Mehran Yarahmadi, Sonja Wegener, Otto A Sauer
PURPOSE: To investigate the energy dependence/spectral sensitivity of silicon diodes designed for small-field dosimetry and obtain response factors (RFs) for arbitrary photon spectra using Monte Carlo (MC) simulations. METHODS: The EGSnrc user-code DOSRZnrc was used to calculate the dose deposition in water and in the active volume of a stereotactic diode field detector (SFD). Then the RFs of the SFD were calculated for several circular field sizes and energies at 5 cm depth in water...
March 8, 2017: Medical Physics
https://www.readbyqxmd.com/read/28253202/evaluation-of-the-shielding-in-a-treatment-room-with-an-electronic-brachytherapy-unit
#17
Blanca Ibanez-Rosello, Juan Antonio Bautista-Ballesteros, Cristian Candela-Juan, Juan Ignacio Villaescusa, Facundo Ballester, Javier Vijande, Jose Perez-Calatayud
Esteya® (Elekta Brachytherapy, Veenendaal, The Netherlands) is an electronic brachytherapy (eBT) system based on a 69.5 kVp x-ray source and a set of collimators of 1 to 3 cm in diameter, used for treating non-melanoma skin cancer lesions. This study aims to estimate room shielding requirements for this unit. The non-primary (scattered and leakage) ambient dose equivalent rates were measured with a Berthold LB-133 monitor (Berthold Technologies, Bad Wildbad, Germany). The latter ranges from 17 mSv h(-1) at 0...
March 2, 2017: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
https://www.readbyqxmd.com/read/28173979/image-movement-of-the-elekta-epid-during-gantry-rotation-effects-on-the-verification-of-dose-distributions
#18
J Köhn, J Licher, M Mielke, B Loutfi-Krauss, N Blümer, B Heine, C Rödel, C Scherf, U Ramm
PURPOSE: The use of Electronic Portal Imaging Devices (EPIDs) to acquire dosimetric information, especially for 3D-back-projection, has been increasingly extended. For a precise back-projection, the accurate knowledge of the movement characteristics of the EPID during gantry rotation is an essential requirement. METHODS AND MATERIAL: Measurements were conducted with different alignments of steel balls, which were mounted on the treatment table to avoid secondary effects such as the mechanical sag of gantry or jaws...
February 4, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28168813/the-impacts-of-mid-treatment-cbct-guided-patient-repositioning-on-target-coverage-during-lung-vmat
#19
Dominique Mathieu, Marie-Pierre Campeau, Stéphane Bedwani, David Roberge, Robert Doucet, Karim Zerouali, Houda Bahig, Toni Vu, Louise Lambert, Laura Masucci, Edith Filion
INTRODUCTION: The purpose of this study is quantify intrafraction motion (IFM) during lung volumetric-modulated arc therapy (VMAT) and evaluate the impact of mid-treatment cone beam computed tomography (CBCT)-guided patient repositioning on target coverage. METHOD: This analysis included lung tumours treated with VMAT to 50-60 Gy in 3-5 fractions. Treatment planning was based on four-dimensional CT scans from which internal tumour volumes (ITV) were derived. An isotropic 5 mm margin was added to obtain the final planning target volume (PTV)...
February 7, 2017: Journal of Medical Imaging and Radiation Oncology
https://www.readbyqxmd.com/read/28168125/role-of-gamma-knife%C3%A2-radiosurgery-for-the-treatment-of-brain-metastases-from-gynecological-cancers
#20
Andrew Keller, Rahim Ismail, Peter S Potrebko, Julie Pepe, Meiling Wu, Kunal Saigal, Matthew Biagioli, Ravi Shridhar, Robert Holloway, Melvin Field, Nikhil G Rao
OBJECTIVE: Gamma Knife(®) (GK) (Elekta Instruments, Stockholm, Sweden) radiosurgery is well established for treatment of brain metastases. There are limited data on patients treated with GK from gynecological cancers. The authors sought to determine the effectiveness of the GK in patients with brain metastases from gynecological cancers. METHODS: An IRB-approved database was queried for patients with gynecologic cancers treated with GK between June 1996 and May 2016...
December 31, 2016: Curēus
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