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https://www.readbyqxmd.com/read/28323641/metal-artifacts-in-computed-tomography-for-radiation-therapy-planning-dosimetric-effects-and-impact-of-metal-artifact-reduction
#1
Drosoula Giantsoudi, Bruno De Man, Joost Verburg, Alexei Trofimov, Yannan Jin, Ge Wang, Lars Gjesteby, Harald Paganetti
A significant and increasing number of patients receiving radiation therapy present with metal objects close to, or even within, the treatment area, resulting in artifacts in computed tomography (CT) imaging, which is the most commonly used imaging method for treatment planning in radiation therapy. In the presence of metal implants, such as dental fillings in treatment of head-and-neck tumors, spinal stabilization implants in spinal or paraspinal treatment or hip replacements in prostate cancer treatments, the extreme photon absorption by the metal object leads to prominent image artifacts...
March 21, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28319041/practical-use-of-a-plastic-scintillator-for-quality-assurance-of-electron-beam-therapy
#2
Katsunori Yogo, Yuya Tatsuno, Masato Tsuneda, Yuki Aono, Daiki Mochizuki, Yoshiki Fujisawa, Akihiro Matsushita, Minoru Ishigami, Hiromichi Ishiyama, Kazushige Hayakawa
Quality assurance (QA) of the clinical electron beam is essential for performing accurate and safe radiation therapy. However, with advances in radiation therapy, QA tends to be labor-intensive and time consuming. Here, we propose the practical use of a tissue-equivalent plastic scintillator for quick and easy QA of clinical electron beams. This tool enabled us to verify simultaneously the constancy of output, beam quality, depth and lateral dose profiles during monthly QAs at lower doses of irradiation (small MUs)...
March 20, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28317312/evaluation-of-dose-calculation-accuracy-of-treatment-planning-systems-at-hip-prosthesis-interfaces
#3
David Paulu, Parham Alaei
There are an increasing number of radiation therapy patients with hip prosthesis. The common method of minimizing treatment planning inaccuracies is to avoid radiation beams to transit through the prosthesis. However, the beams often exit through them, especially when the patient has a double-prosthesis. Modern treatment planning systems employ algorithms with improved dose calculation accuracies but even these algorithms may not predict the dose accurately at high atomic number interfaces. The current study evaluates the dose calculation accuracy of three common dose calculation algorithms employed in two commercial treatment planning systems...
March 20, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28317152/-68-ga-psma-pet-for-radiation-treatment-planning-in-prostate-cancer-recurrences-after-surgery-individualized-medicine-or-new-standard-in-salvage-treatment
#4
Gregor Habl, Katharina Sauter, Kilian Schiller, Sabrina Dewes, Tobias Maurer, Matthias Eiber, Stephanie E Combs
BACKGROUND: (68) Ga-PSMA-PET imaging is a novel promising diagnostic tool to locate early biochemical failure after radical prostatectomy (RP) in prostate cancer (PC) patients. Exact knowledge of the relapse location may result in changes of the therapy concept aside from changes to the TNM stage. To gain data for this approach, we evaluated PC patients receiving (68) Ga-PSMA-PET imaging before salvage radiotherapy (RT). METHODS AND MATERIALS: In this study, 100 patients with biochemical failure after RP± prior RT who underwent (68) Ga-PSMA PET/CT or PET/MRI were evaluated undergoing salvage RT in our department...
March 20, 2017: Prostate
https://www.readbyqxmd.com/read/28317129/towards-robust-adaptive-radiation-therapy-strategies
#5
Michelle Böck, Anders Forsgren, Kjell Eriksson, Björn Hårdemark
PURPOSE: To set up a framework combining robust treatment planning with adaptive reoptimization in order to maintain high treatment quality, to respond to interfractional geometric variations and to identify those patients who will benefit the most from an adaptive fractionation schedule. METHODS: The authors propose robust adaptive strategies based on stochastic minimax optimization for a series of simulated treatments on a one-dimensional patient phantom. The plan applied during the first fractions should be able to handle anticipated systematic and random errors...
March 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28317122/an-anthropomorphic-abdominal-phantom-for-deformable-image-registration-accuracy-validation-in-adaptive-radiation-therapy
#6
Yuliang Liao, Linjing Wang, Xiangdong Xu, Haibin Chen, Jiawei Chen, Guoqian Zhang, Huaiyu Lei, Ruihao Wang, Shuxu Zhang, Xuejun Gu, Xin Zhen, Linghong Zhou
PURPOSE: To design and construct a three-dimensional (3D) anthropomorphic abdominal phantom for geometric accuracy and dose summation accuracy evaluations of deformable image registration (DIR) algorithms for adaptive radiation therapy (ART). METHOD: Organ molds, including liver, kidney, spleen, stomach, vertebra and two metastasis tumors, were 3D printed using contours from an ovarian cancer patient. The organ molds were molded with deformable gels made of different mixtures of polyvinyl chloride (PVC) and the softener dioctyl terephthalate...
March 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28306547/synthetic-ct-for-mri-based-liver-stereotactic-body-radiotherapy-treatment-planning
#7
Jeremy S Bredfeldt, Lianli Liu, Mary Feng, Yue Cao, James M Balter
A technique for generating MRI-derived synthetic CT volumes (MRCTs) is demonstrated in support of adaptive liver stereotactic body radiation therapy (SBRT). Under IRB approval, 16 subjects with hepatocellular carcinoma were scanned using a single MR pulse sequence (T1 Dixon). Air-containing voxels were identified by intensity thresholding on T1-weighted, water and fat images. The envelope of the anterior vertebral bodies was segmented from the fat image and fuzzy-C-means (FCM) was used to classify each non-air voxel as mid-density, lower-density, bone, or marrow in the abdomen, with only bone and marrow classified within the vertebral body envelope...
March 17, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28306546/substitute-ct-generation-from-a-single-ultra-short-time-echo-mri-sequence-preliminary-study
#8
Soumya Ghose, Jason A Dowling, Robba Rai, Gary P Liney
In MR guided radiation therapy planning both MR and CT images for a patient are acquired and co-registered to obtain a tissue specific HU map. Generation of the HU map directly from the MRI would eliminate the CT acquisition and may improve radiation therapy planning. In this preliminary study of substitute CT (sCT) generation, two porcine leg phantoms were scanned using a 3D ultrashort echo time (PETRA) sequence and co-registered to corresponding CT images to build tissue specific regression models. The model was created from one co-registered CT-PETRA pair to generate the sCT for the other PETRA image...
March 17, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28300381/comparison-of-ct-images-with-average-intensity-projection-free-breathing-and-mid-ventilation-for-dose-calculation-in-lung-cancer
#9
Chirasak Khamfongkhruea, Sangutid Thongsawad, Chirapha Tannanonta, Sasikarn Chamchod
The purpose of this study was to compare three computed tomography (CT) images under different conditions-average intensity projection (AIP), free breathing (FB), mid-ventilation (MidV)-used for radiotherapy contouring and planning in lung cancer patients. Two image sets derived from four-dimensional CT (4DCT) acquisition (AIP and MidV) and three-dimensional CT with FB were generated and used to plan for 29 lung cancer patients. Organs at risk (OARs) were delineated for each image. AIP images were calculated with 3D conformal radiotherapy (3DCRT) and intensity-modulated radiation therapy (IMRT)...
March 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28300369/perturbation-effects-of-the-carbon-fiber-peek-screws-on-radiotherapy-dose-distribution
#10
Alexander Nevelsky, Egor Borzov, Shahar Daniel, Raquel Bar-Deroma
Radiation therapy, in conjunction with surgical implant fixation, is a common combined treatment in cases of bone metastases. However, metal implants generally used in orthopedic implants perturb radiation dose distributions. Carbon-Fiber Reinforced Polyetheretherketone (CFR-PEEK) material has been recently introduced for production of intramedullary nails and plates. The purpose of this work was to investigate the perturbation effects of the new CFR-PEEK screws on radiotherapy dose distributions and to evaluate these effects in comparison with traditional titanium screws...
March 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28300368/reduction-in-stray-radiation-dose-using-a-body-shielding-device-during-external-radiation-therapy
#11
Shuxu Zhang, Shaohui Jiang, Quanbin Zhang, Shengqu Lin, Ruihao Wang, Xiang Zhou, Guoqian Zhang, Huaiyu Lei, Hui Yu
With the purpose of reducing stray radiation dose (SRD) in out-of-field region (OFR) during radiotherapy with 6 MV intensity-modulated radiation therapy (IMRT), a body-shielding device (BSD) was prepared according to the measurements obtained in experimental testing. In experimental testing, optimal shielding conditions, such as 1 mm lead, 2 mm lead, and 1 mm lead plus 10 mm bolus, were investigated along the medial axis of a phantom using thermoluminescent dosimeters (TLDs). The SRDs at distances from field edge were then measured and analyzed for a clinical IMRT treatment plan for nasopharyngeal carcinoma before and after shielding using the BSD...
March 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28299759/optimizing-the-benefit-of-cns-radiation-therapy-in-the-pediatric-population-part-2-novel-methods-of-radiation-delivery
#12
REVIEW
Lindsay S Rowe, Andra V Krauze, Holly Ning, Kevin A Camphausen, Aradhana Kaushal
Newer approaches in the field of radiation therapy have raised the bar in the treatment of central nervous system (CNS) malignancies, with recognized advances that have aimed to increase the therapeutic index by improving conformality of the radiation dose to the planned target volume. Beyond these advances, the continued evolution of more effective systems for delivery of radiation to the CNS may offer further benefit not only to adults but also to pediatric patients, a cohort of the population that may be more sensitive to the long-term effects of radiation...
March 15, 2017: Oncology (Williston Park, NY)
https://www.readbyqxmd.com/read/28297461/clinical-experience-with-planning-quality-assurance-and-delivery-of-burst-mode-modulated-arc-therapy
#13
Kristofer Kainz, Douglas Prah, Ergun Ahunbay, X Allen Li
"Burst-mode" modulated arc therapy (hereafter referred to as "mARC") is a form of volumetric-modulated arc therapy characterized by variable gantry rotation speed, static MLCs while the radiation beam is on, and MLC repositioning while the beam is off. We present our clinical experience with the planning techniques and plan quality assurance measurements of mARC delivery. Clinical mARC plans for five representative cases (prostate, low-dose-rate brain, brain with partial-arc vertex fields, pancreas, and liver SBRT) were generated using a Monte Carlo-based treatment planning system...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297459/on-the-use-of-a-convolution-superposition-algorithm-for-plan-checking-in-lung-stereotactic-body-radiation-therapy
#14
Nicholas Hardcastle, Bradley M Oborn, Annette Haworth
Stereotactic body radiation therapy (SBRT) aims to deliver a highly conformal ablative dose to a small target. Dosimetric verification of SBRT for lung tumors presents a challenge due to heterogeneities, moving targets, and small fields. Recent software (M3D) designed for dosimetric verification of lung SBRT treatment plans using an advanced convolution-superposition algorithm was evaluated. Ten lung SBRT patients covering a range of tumor volumes were selected. 3D CRT plans were created using the XiO treatment planning system (TPS) with the superposition algorithm...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297458/translucent-poly-vinyl-alcohol-cryogel-dosimeters-for-simultaneous-dose-buildup-and-monitoring-during-chest-wall-radiation-therapy
#15
Molham M Eyadeh, Mark A Weston, Janos Juhasz, Kevin R Diamond
Chest wall radiation therapy treatment delivery was monitored using a 5 mm thick radiochromic poly(vinyl alcohol) cryogel that also provided buildup material. The cryogels were used to detect positioning errors and measure the impact of shifts for a chest wall treatment that was delivered to a RANDO phantom. The phantom was shifted by ±2,±3, and ±5 mm from the planned position in the anterior/posterior (A/P) direction; these shifts represent setup errors and the uncertainty associated with lung filling during breath-hold...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297455/accuracy-of-one-algorithm-used-to-modify-a-planned-dvh-with-data-from-actual-dose-delivery
#16
Tianjun Ma, Matthew B Podgorsak, Lalith Kumaraswamy
Detection and accurate quantification of treatment delivery errors is important in radiation therapy. This study aims to evaluate the accuracy of DVH based QA in quantifying delivery errors. Eighteen previously treated VMAT plans (prostate, H&N, and brain) were randomly chosen for this study. Conventional IMRT delivery QA was done with the ArcCHECK diode detector for error-free plans and plans with the following modifications: 1) induced monitor unit differences up to ±3.0%,2) control point deletion (3, 5, and 8 control points were deleted for each arc), and 3) gantry angle shift (2° uniform shift clockwise and counterclockwise)...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297453/spot-scanning-proton-therapy-minimizes-neutron-dose-in-the-setting-of-radiation-therapy-administered-during-pregnancy
#17
Xin Wang, Falk Poenisch, Narayan Sahoo, Ronald X Zhu, MingFwu Lii, Michael T Gillin, Jing Li, David Grosshans
This is a real case study to minimize the neutron dose equivalent (H) to a fetus using spot scanning proton beams with favorable beam energies and angles. Minimum neutron dose exposure to the fetus was achieved with iterative planning under the guidance of neutron H measurement. Two highly conformal treatment plans, each with three spot scanning beams, were planned to treat a 25-year-old pregnant female with aggressive recurrent chordoma of the base of skull who elected not to proceed with termination. Each plan was scheduled for delivery every other day for robust target coverage...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297441/comprehensive-dosimetric-planning-comparison-for-early-stage-non-small-cell-lung-cancer-with-sabr-fixed-beam-imrt-versus-vmat-versus-tomotherapy
#18
Ilma Xhaferllari, Omar El-Sherif, Stewart Gaede
Volumetric-modulated arc therapy (VMAT) is emerging as a leading technology in treating early-stage, non-small cell lung cancer (NSCLC) with stereotactic ablative radiotherapy (SABR). However, two other modalities capable of delivering intensity-modulated radiation therapy (IMRT) include fixed-beam and helical TomoTherapy (HT). This study aims to provide an extensive dosimetric comparison among these various IMRT techniques for treating early-stage NSCLC with SABR. Ten early-stage NSCLC patients were retrospectively optimized using three fixed-beam techniques via nine to eleven beams (high and low modulation step-and-shoot (SS), and sliding window (SW)), two VMAT techniques via two partial arcs (SmartArc (SA) and RapidArc (RA)), and three HT techniques via three different fan beam widths (1 cm, 2...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297436/simultaneously-integrated-boost-sib-spares-oar-and-reduces-treatment-time-in-locally-advanced-cervical-cancer
#19
Christine H Feng, Yasmin Hasan, Malgorzata Kopec, Hania A Al-Hallaq
We performed a dosimetric comparison of sequential IMRT (sIMRT) and simultaneously integrated boost (SIB) IMRT to boost PET-avid lymph nodes while concurrently treating pelvic targets to determine the potential of SIB IMRT to reduce overall treatment duration in locally advanced cervical cancer. Ten patients receiving definitive radiation therapy were identified retrospectively. RTOG consensus guidelines were followed to delineate the clinical target volume and organs at risk (OAR), which were then expanded per IMRT consortium guidelines to yield the planning target volume (PTV)...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297432/difference-in-dose-volumetric-data-between-the-analytical-anisotropic-algorithm-the-dose-to-medium-and-the-dose-to-water-reporting-modes-of-the-acuros-xb-for-lung-stereotactic-body-radiation-therapy
#20
Wambaka A Mampuya, Mitsuhiro Nakamura, Yoshinori Hirose, Takashi Ishigaki, Takashi Mizowaki, Masahiro Hiraoka
The purpose of this study was to evaluate the difference in dose-volumetric data between the analytical anisotropic algorithms (AAA) and the two dose reporting modes of the Acuros XB, namely, the dose to water (AXB-Dw) and dose to medium (AXB-Dm) in lung stereotactic body radiotherapy (SBRT). Thirty-eight plans were generated using the AXB-Dm in Eclipse Treatment Planning System (TPS) and then recalculated with the AXB-Dw and AAA, using identical beam setup. A dose of 50 Gy in 4 fractions was prescribed to the isocenter and the planning target volume (PTV) D95%...
September 2016: Journal of Applied Clinical Medical Physics
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