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David J Eaton, Jonathan Lee, Ian Paddick
PURPOSE: Stereotactic radiosurgery is indicated for treatment of multiple brain metastases. Various treatment platforms are available, but most comparisons are limited to single-center studies. As part of a national commissioning program, benchmark planning cases were completed by 21 clinical centers, providing a unique dataset of current practice across a large number of providers and equipment platforms. METHODS AND MATERIALS: Two brain metastases cases were provided, with images and structures predrawn, involving 3 and 7 lesions...
December 30, 2017: Practical Radiation Oncology
Kayhan Gonoodi, Alireza Moslem, Susan Darroudi, Mahsa Ahmadnezhad, Zahra Mazloum, Maryam Tayefi, Seyed Amir Tabatabaei Zadeh, Saeid Eslami, Mojtaba Shafiee, Zahra Khashayarmanesh, Hamideh Moalemzadeh Haghighi, Gordon A Ferns, Majid Ghayour-Mobarhan
OBJECTIVE: Girls with micronutrient deficiencies may have impaired growth and development, and furthermore this may also impact on their childbearing. We have investigated the relationship between serum zinc and copper concentrations, dietary zinc and copper intake and anthropometric and demographic parameters, and cardiovascular risk factors, in 408 girls living in northeastern Iran. METHODS: A total of 408 healthy girls, aged 12-18 years old, were included in our study...
February 10, 2018: Clinical Biochemistry
Liugang Gao, Hongfei Sun, Xinye Ni, Mingming Fang, Tao Lin
Dose distribution was calculated and analyzed on the basis of 16-bit computed tomography (CT) images in order to investigate the effect of scanning conditions on CT for metal implants. Stainless steel and titanium rods were inserted into a phantom, and CT images were obtained by scanning the phantom under various scanning conditions: i) Fixed tube current of 230 mA and tube voltages of 100, 120, and 140 kV; and ii) fixed tube voltage of 120 kV and tube currents of 180, 230, and 280 mA. The CT value of the metal rod was examined and corrected...
February 2018: Oncology Letters
Mireille Conrad, Grégory Bolard, Marie Nowak, Berardino De Bari, Wendy Jeanneret-Sozzi, Jean Bourhis, Jean-François Germond, François Bochud, Raphaël Moeckli
PURPOSE: Image guided radiotherapy (IGRT) improves patient positioning for treatment delivery at the cost of an additional dose. This work aimed to calculate the effective dose (as an indicator of dose) for head & neck (H&N) and breast IGRT treatments by implementing dose calculation models to determine the dose distributions. METHODS: The kV dose-models were created for the IGRT systems of Elekta Synergy (XVI) and Varian Clinac (OBI) linear accelerators within Philips Pinnacle TPS...
February 6, 2018: Zeitschrift Für Medizinische Physik
Timo Ikonen, Antti Kulmala, Christopher Boylan, Viljo Petäjä, Daren Sawkey
Monte Carlo simulations can provide powerful insight into the physical phenomena and geometrical interactions of linear accelerator beams. This insight can be used to understand the phenomena that govern the beam characteristic and, for instance, to guide the development of treatment planning systems. In this study, we use the VirtuaLinac, a cloud-based application to model the treatment head of the Varian TrueBeam linear accelerator. VirtuaLinac implements the treatment head geometry into the Monte Carlo code Geant4, which is then utilized to provide the physics and numerical engine for the simulations...
January 2018: Physica Medica: PM
Jaegi Lee, Sung-Joon Ye
Magnetic resonance imaging-guided radiotherapy provides real-time imaging with a superior soft-tissue contrast without radiation exposure. Recently, several groups have been developing such a new technology. Strong magnetic fields can influence trajectories of the secondary electrons by the Lorentz force. The reference dosimetry using an ion-chamber in magnetic fields needs additional correction factors [1]. In this study, we calculated magnetic field correction factors by the Monte Carlo method for the reference dosimetry using a parallel-plate ion-chamber...
January 2018: Physica Medica: PM
Do-Yeon Cho, Dong-Jin Lim, Calvin Mackey, Christopher G Weeks, Jaime A Peña Garcia, Daniel Skinner, Jessica W Grayson, Harrison S Hill, David K Alexander, Shaoyan Zhang, Bradford A Woodworth
BACKGROUND: Biofilms may contribute to refractory chronic rhinosinusitis (CRS), as they lead to antibiotic resistance and failure of effective clinical treatment. l-Methionine is an amino acid with reported biofilm-inhibiting properties. Ivacaftor is a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator with mild antimicrobial activity via inhibition of bacterial DNA gyrase and topoisomerase IV. The objective of this study was to evaluate whether co-treatment with ivacaftor and l-methionine can reduce the formation of Pseudomonas aeruginosa biofilms...
February 7, 2018: International Forum of Allergy & Rhinology
Lilie Wang, Anthony J Cmelak, George X Ding
Radiation dermatitis during radiotherapy is correlated with skin dose and is a common clinical problem for head and neck and thoracic cancer patients. Therefore, accurate prediction of skin dose during treatment planning is clinically important. The objective of this study is to evaluate the accuracy of skin dose calculated by a commercial treatment planning system (TPS). We evaluated the accuracy of skin dose calculations by the anisotropic analytical algorithm (AAA) implemented in Varian Eclipse (V.11) system...
February 6, 2018: Journal of Applied Clinical Medical Physics
Sean Pollock, Regina Tse, Darren Martin, Lisa McLean, Melissa Pham, David Tait, Reuben Estoesta, Grant Whittington, Jessica Turley, Christopher Kearney, Gwi Cho, Robin Hill, Sheila Pickard, Paul Aston, Kuldeep Makhija, Ricky O'Brien, Paul Keall
INTRODUCTION: Irregular breathing motion exacerbates uncertainties throughout a course of radiation therapy. Breathing guidance has demonstrated to improve breathing motion consistency. This was the first clinical implementation of audiovisual biofeedback (AVB) breathing guidance over a course of liver stereotactic body radiotherapy (SBRT) investigating interfraction reproducibility. METHODS: Five liver cancer patients underwent a screening procedure prior to CT sim during which patients underwent breathing conditions (i) AVB, or (ii) free breathing (FB)...
February 2018: Journal of Medical Imaging and Radiation Oncology
Maria D Pavlaki, Rui G Morgado, Amadeu M V M Soares, Ricardo Calado, Susana Loureiro
The present study assessed cadmium uptake and depuration rates in the euryhaline estuarine shrimp Palaemon varians under different exposure routes. Postlarval shrimp were exposed for four days under different exposure routes; through contaminated water, contaminated diet and a two-way exposure scenario where both contaminated water + diet were used. After exposure, postlarval shrimp were transferred to a clean medium and fed a non-contaminated diet for 96 h. Bioaccumulation via the different exposure routes was modeled with a standard first-order one-compartment toxicokinetics model and one with an additional parameter reflecting an inert fraction or storage compartment...
February 1, 2018: Environmental Toxicology and Chemistry
Hideyuki Takei, Tomonori Isobe, Nozomi Kitamura, Yutaro Mori, Tetsuya Tomita, Daisuke Kobayashi, Satoshi Kamizawa, Tomoharu Sato, Hideyuki Sakurai, Takeji Sakae
Liquid ionization chambers (LICs) are highly sensitive to dose irradiation and have small perturbations because of their liquid-filled sensitive volume. They require a sensitive volume much smaller than conventional air-filled chambers. However, it has been reported that the collection efficiency has dependencies on the dose per pulse and the pulse repetition frequency of a pulsed beam. The purpose of this study was to evaluate in detail the dependency of the ion collection efficiency on the pulse repetition frequency...
January 24, 2018: Journal of Radiation Research
James C L Chow, Runqing Jiang
This study evaluated the effects of dose-volume and radiobiological dependence on the calculation grid size in prostate volumetric-modulated arc therapy (VMAT) planning. Ten patients with prostate cancer were selected for this retrospective treatment planning study. Prostate VMAT plans were created for the patients using the 6 MV photon beam produced by a Varian TrueBEAM linac with the calculation grid size equal to 1, 2, 2.5, 3, 4, and 5 mm. Dose-volume histograms (DVHs) of targets and organs at risk were generated for different grid sizes...
January 17, 2018: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
Yongtao Liu, Linxue Yu, Zhenyue Wang, Qiuhong Yang, Jing Dong, Yibin Yang, Xiaohui Ai
A method was established for the simultaneous determination of seven avermectin (AVMs) residues, such as avermectin, ivermectin, doramectin, selamectin, eprinomectin, moxidectin and emamectin, in aquatic products using modified QuEChERS and high-performance liquid chromatography -tandem mass spectrometry (HPLC-MS/MS). The samples were extracted with 0.2% (v/v) ammoniate acetonitrile, and then 3 g of anhydrous magnesium sulfate and 2 g of anhydrous sodium sulfate were added to remove moisture and precipitate proteins...
December 8, 2017: Se Pu, Chinese Journal of Chromatography
Elham Hosseinzadeh, Nooshin Banaee, Hassan Ali Nedaie
Aim: The aim of this study is to calculate neutron contamination at the presence of circular cones irradiating by 18 MV photons using Monte Carlo code. Background: Small photon fields are one of the most useful methods in radiotherapy. One of the techniques for shaping small photon beams is applying circular cones made of lead. Using this method in high energy photon due to neutron contamination is a crucial issue. Materials and methods: Initially, Varian linac producing 18 MV photons was simulated and after validating the code, various circular cones were also simulated...
January 2018: Reports of Practical Oncology and Radiotherapy
Aileen Duffton, Azmat Sadozye, Lynsey Devlin, Nicholas MacLeod, Carolynn Lamb, Suzanne Currie, Philip McLoone, Marimuthu Sankaralingam, John Foster, Stephanie Paterson, Stefanie Keatings, David Dodds
OBJECTIVE: To investigate feasibility and safety of stereotactic ablative radiotherapy in the management of prostate cancer while employing MR/CT fusion for delineation, fiducial marker seeds for positioning and Varian RapidArc with flattening filter free (FFF) delivery. METHODS: 41 patients were treated for low-intermediate risk prostate cancer with initial prostate-specific antigen of ≤20 ng ml-1, Gleason score 6-7. Patients had MR/CT fusion for delineation of prostate ±seminal vesicles...
February 1, 2018: British Journal of Radiology
C-S Chang, R Shih, J-M Hwang, K-S Chuang
INTRODUCTION: The regular functions of CT-MRI registration include delineation of targets and organs-at-risk (OARs) in radiosurgery planning. The question of whether deformable image registration (DIR) could be applied to stereotactic radiosurgery (SRS) in its place remains a subject of debate. METHODS: This study collected data regarding 16 patients who had undergone single-fraction SRS treatment. All lesions were located close to the brainstem. CT and MRI two image sets were registered by both rigid image registration (RIR) and DIR algorithms...
February 2018: Radiography
Karunakaran Kaviarasu, N Arunai Nambi Raj, Misba Hamid, A Ananda Giri Babu, Lingampally Sreenivas, Kammari Krishna Murthy
Aim: The purpose of this study is to verify the accuracy of the commissioning of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) based on the recommendation of the American Association of Physicists in Medicine Task Group 119 (TG-119). Materials and Methods: TG-119 proposes a set of clinical test cases to verify the accuracy of IMRT planning and delivery system. For these test cases, we generated two sets of treatment plans, the first plan using 7-9 IMRT fields and a second plan utilizing two-arc VMAT technique for both 6 MV and 15 MV photon beams...
October 2017: Journal of Medical Physics
Christopher F Njeh, Howard W Salmon, Claire Schiller
Introduction: Intensity-modulated radiation therapy (IMRT) delivery using "step-and-shoot" technique on Varian C-Series linear accelerator (linac) is influenced by the communication frequency between the multileaf collimator and linac controllers. Hence, the dose delivery accuracy is affected by the dose rate. Aim: Our aim was to quantify the impact of using two dose rates on plan quality assurance (QA). Materials and Methods: Twenty IMRT patients were selected for this study...
October 2017: Journal of Medical Physics
L Ben Salem, A Essadok, I Saidani, M Mahdouani, M Benna, K Mahjoubi, M Besbes, F Benna
PURPOSE: The aim of this work is to determine experimentally the correction factors [Formula: see text] for four active commercial dosimeters: two microchambers and two diode detectors based on the output factor measured with radiochromic film for a radiotherapy linear accelerator equipped with circular cones. MATERIALS AND METHODS: Initially, a radiochromic film dosimetry measurement protocol with an accuracy of 2% was developed to approach the "reference output factor"...
December 28, 2017: Cancer Radiothérapie: Journal de la Société Française de Radiothérapie Oncologique
Teh Lin, Murshed Hossain, Jiajin Fan, C-M Charlie Ma
When a linear accelerator is unavailable for treatment, a clinical decision is imminent regarding whether a patient should be treated on a linear accelerator other than the machine the patient was scheduled on, or whether treatment should be postponed until the original Linac becomes available. This work investigates the feasibility of switching patients to different accelerators for intensity-modulated radiation therapy (IMRT). We have performed Monte Carlo simulations of photon beams from different Linac models and vendors...
December 26, 2017: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
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