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Dose calculation algorithms

Konstantinos A Mountris, Dimitris Visvikis, Julien Bert
PURPOSE: Inverse planning is an integral part of modern low-dose-rate (LDR) brachytherapy. Current clinical planning systems do not exploit the total dose information and largely use the AAPM TG-43 dosimetry formalism to ensure clinically acceptable planning times. Thus, sub-optimal plans may be derived due to TG-43-related dose overestimation and non-conformity with dose distribution requirements. The purpose of this study was to propose an inverse planning approach that can improve planning quality by combining dose-volume information and precision without compromising the overall execution times...
October 10, 2018: International Journal of Radiation Oncology, Biology, Physics
Ludovic De Marzi, Annalisa Patriarca, Catherine Nauraye, Eric Hierso, Rémi Dendale, Consuelo Guardiola, Yolanda Prezado
PURPOSE: Proton minibeam radiation therapy (pMBRT) is an innovative approach that combines the advantages of minibeam radiation therapy with the more precise ballistics of protons to further reduce the side effects of radiation. One of the main challenges of this approach is the generation of very narrow proton pencil beams with an adequate dose-rate to treat patients within a reasonable treatment time (several minutes) in existing clinical facilities. The aim of this study was to demonstrate the feasibility of implementing pMBRT by combining the pencil beam scanning (PBS) technique with the use of multislit collimators...
September 22, 2018: Medical Physics
Gaganpreet Singh, Arun S Oinam, Rose Kamal, Bhumika Handa, Vivek Kumar, Bhavana Rai
Introduction: Three-dimensional (3D) treatment planning of patient undergoing radiotherapy uses complex and meticulous computational algorithms. These algorithms use 3D voxel data of the patient to calculate the radiation dose distribution and display it over the CT image dataset for treatment plan evaluation. Aims and Objective: The purpose of the present study is the development and implementation of radiobiological evaluation of the radiotherapy treatment plan incorporating the tissue-specific radiobiological parameters...
July 2018: Journal of Medical Physics
Karsten Mueller, Robert Jech, Tommaso Ballarini, Štefan Holiga, Filip Růžička, Fabian A Piecha, Harald E Möller, Josef Vymazal, Evžen Růžička, Matthias L Schroeter
Levodopa has been the mainstay of symptomatic therapy for Parkinson's disease (PD) for the last five decades. However, it is associated with the development of motor fluctuations and dyskinesia, in particular after several years of treatment. The aim of this study was to shed light on the acute brain functional reorganization in response to a single levodopa dose. Functional magnetic resonance imaging (fMRI) was performed after an overnight withdrawal of dopaminergic treatment and 1 h after a single dose of 250 mg levodopa in a group of 24 PD patients...
October 8, 2018: Cerebellum
Sheng Huang, Kevin Souris, Siyang Li, Minglei Kang, Ana Maria Barragan Montero, Guillaume Janssens, Alexander Lin, Elizabeth Garver, Christopher Ainsley, Paige Taylor, Ying Xiao, Liyong Lin
PURPOSE: Monte Carlo (MC) dose calculation is generally superior to analytical dose calculation (ADC) used in commercial TPS to model the dose distribution especially for heterogeneous sites, such as lung and head/neck patients. The purpose of this study is to provide a validated, fast and open-source MC code, MCsquare, to assess the impact of approximations in ADC on clinical pencil beam scanning (PBS) plans covering various sites. METHODS: First, MCsquare was validated using tissue-mimicking IROC lung phantom measurements as well as benchmarked with the general-purpose Monte Carlo TOPAS for patient dose calculation...
October 8, 2018: Medical Physics
Luca Cozzi, Antonella Fogliata, Stephen Thompson, Ciro Franzese, Davide Franceschini, Fiorenza de Rose, Stefano Tomatis, Marta Scorsetti
PURPOSE: To ascertain whether a new delivery system (the Halcyon system) equipped with dual-layer stacked multileaf collimator operating in a mode, which allows independent, fully interdigitating motion of both layers and 6 flattening filter free energy, could generate plans of high clinical quality compared to a well-established delivery system with single layer multileaf collimator. METHODS: Twenty patients in each of the 3 groups (advanced head and neck, breast, and high-risk prostate) were selected for an in silico planning study...
January 1, 2018: Technology in Cancer Research & Treatment
R Lee MacDonald, Christopher G Thomas, Lucy Ward, Alasdair Syme
PURPOSE: To design and implement a novel treatment planning algorithm based on a modification of dynamic conformal arc (DCA) therapy for the treatment of multiple cranial metastases with variable prescription doses. METHODS: A workflow was developed in which separate dose matrices were calculated for each target at each control point (i.e. the MLC was fit conformally to that single target). A cost function was used to quantify the relative contributions of each dose matrix in the plan to the overall plan objectives...
October 4, 2018: Medical Physics
Stewart Mein, Kyungdon Choi, Benedikt Kopp, Thomas Tessonnier, Julia Bauer, Alfredo Ferrari, Thomas Haberer, Jürgen Debus, Amir Abdollahi, Andrea Mairani
Radiotherapy with protons and heavier ions landmarks a novel era in the field of high-precision cancer therapy. To identify patients most benefiting from this technologically demanding therapy, fast assessment of comparative treatment plans utilizing different ion species is urgently needed. Moreover, to overcome uncertainties of actual in-vivo physical dose distribution and biological effects elicited by different radiation qualities, development of a reliable high-throughput algorithm is required. To this end, we engineered a unique graphics processing unit (GPU) based software architecture allowing rapid and robust dose calculation...
October 4, 2018: Scientific Reports
Tengjiao Fan, Guohui Sun, Lijiao Zhao, Xin Cui, Rugang Zhong
To better understand the mechanism of in vivo toxicity of N -nitroso compounds (NNCs), the toxicity data of 80 NNCs related to their rat acute oral toxicity data (50% lethal dose concentration, LD50 ) were used to establish quantitative structure-activity relationship (QSAR) and classification models. Quantum chemistry methods calculated descriptors and Dragon descriptors were combined to describe the molecular information of all compounds. Genetic algorithm (GA) and multiple linear regression (MLR) analyses were combined to develop QSAR models...
October 3, 2018: International Journal of Molecular Sciences
Masakazu Otsuka, Hajime Monzen, Kenji Matsumoto, Mikoto Tamura, Masahiro Inada, Noriyuki Kadoya, Yasumasa Nishimura
BACKGROUND: Four-dimensional computed tomography (4D-CT) ventilation is an emerging imaging modality. Functional avoidance of regions according to 4D-CT ventilation may reduce lung toxicity after radiation therapy. This study evaluated associations between 4D-CT ventilation-based dosimetric parameters and clinical outcomes. METHODS: Pre-treatment 4D-CT data were used to retrospectively construct ventilation images for 40 thoracic cancer patients retrospectively...
2018: PloS One
André Euler, Justin Solomon, Maciej A Mazurowski, Ehsan Samei, Rendon C Nelson
OBJECTIVES: To assess the impact of scan- and patient-related factors on the error and the minimum detectable difference in iodine concentration among different generations of single-source (SS) fast kV-switching and dual-source (DS) dual-energy CT (DECT). METHODS: Lesions having eight different iodine concentrations (0.2-4 mgI/mL) were emulated in a 3D-printed phantom of medium and large size. Each combination of concentration and size was scanned in dual-energy mode on four different SS and DS DECTs...
October 1, 2018: European Radiology
Tamilarasan Rajamanickam, Sivakumar Muthu, Perumal Murugan, Muddappa Pathokonda, Krishnamoorthy Senthilnathan, Narayanasamy Arunai Nambi Raj, Padmanabhan Ramesh Babu
PURPOSE: Addition of high Z implants in the treatment vicinity or beam path is unavoidable in certain clinical situation. In this work, we study the properties of radiation interaction parameters such as mass attenuation coefficient (MAC), x ray beam transmission factor (indirect beam attenuation), interface effects like backscatter dose perturbation factor (BSDF) and forward dose perturbation factor (FDPF) for flattened (FF) and unflattened (UF) x ray beams. METHODS: MAC for stainless steel and titanium alloy was measured using CC13 chamber with appropriate buildup in narrow beam geometry...
September 28, 2018: Journal of Applied Clinical Medical Physics
Arezoo Modiri, Line Bjerregaard Stick, Stephanie Renee Rice, Laura Ann Rechner, Ivan Richter Vogelius, Søren Møller Bentzen, Amit Sawant
PURPOSE: Current radiation therapy planning uses a set of defined dose-volume constraints to ensure a specified level of tumor coverage while constraining the dose distribution in the organs at risk. Such constraints are aggregated, population-based quantities which do not adequately consider patient-specific risk. Furthermore, these constraints are calculated for each organ independently and it is therefore not guaranteed that the optimal tradeoff between organs is achieved. We introduce a novel radiotherapy planning approach, where a patient-specific all-cause mortality risk is minimized using inverse plan optimization...
September 23, 2018: Medical Physics
Andrew D Wiese, Marie R Griffin, William Schaffner, C Michael Stein, Robert A Greevy, Edward F Mitchel, Carlos G Grijalva
Background: Although evidence from animal and human studies indicates opioid analgesics increase susceptibility to infections, it is unclear whether the risk varies by specific opioid. We compared the risk of serious infection among patients initiating long-acting opioid analgesics with and without previously reported immunosuppressive properties. Methods: We conducted a retrospective cohort study of Tennessee Medicaid enrollees age ≥18 years initiating long-acting opioids (1995-2015)...
September 15, 2018: Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America
Jae Pil Chung, Young Min Seong, Tae Yeon Kim, Yona Choi, Tae Hoon Kim, Hyun Joon Choi, Chul Hee Min, Hamza Benmakhlouf, Kook Jin Chun, Hyun-Tai Chung
BACKGROUND: To measure the absorbed dose rate to water and penumbra of a Gamma Knife® (GK) using a polymethyl metacrylate (PMMA) phantom. METHODS: A multi-purpose PMMA phantom was developed to measure the absorbed dose rate to water and the dose distribution of a GK. The phantom consists of a hemispherical outer phantom, one exchangeable cylindrical chamber-hosting inner phantom, and two film-hosting inner phantoms. The radius of the phantom was determined considering the electron density of the PMMA such that it corresponds to 8 g/cm2 water depth, which is the reference depth of the absorbed dose measurement of GK...
September 14, 2018: Radiation Oncology
Hossein Arabi, Jason A Dowling, Ninon Burgos, Xiao Han, Peter B Greer, Nikolaos Koutsouvelis, Habib Zaidi
PURPOSE: Magnetic resonance imaging (MRI)-guided radiation therapy (RT) treatment planning is limited by the fact that the electron density distribution required for dose calculation is not readily provided by MR imaging. We compare a selection of novel synthetic CT generation algorithms recently reported in the literature, including segmentation-based, atlas-based and machine learning techniques, using the same cohort of patients and quantitative evaluation metrics. METHODS: Six MRI-guided synthetic CT generation algorithms were evaluated: one segmentation technique into a single tissue class (water-only), four atlas-based techniques, namely, median value of atlas images (ALMedian) 1 , atlas-based local weighted voting (ALWV) 2 , bone enhanced atlas-based local weighted voting (ALWV-Bone) 3 , iterative atlas-based local weighted voting (ALWV-Iter) 4 , and a machine learning technique using deep convolution neural network (DCNN) 5 ...
September 14, 2018: Medical Physics
Roger Cai Xiang Soh, Guan Heng Tay, Wen Siang Lew, James Cheow Lei Lee
Aim: To identifying depth dose differences between the two versions of the algorithms using AIP CT of a 4D dataset. Background: Motion due to respiration may challenge dose prediction of dose calculation algorithms during treatment planning. Materials and methods: The two versions of depth dose calculation algorithms, namely, Anisotropic Analytical Algorithm (AAA) version 10.0 (AAAv10.0), AAA version 13.6 (AAAv13.6) and Acuros XB dose calculation (AXB) algorithm version 10...
September 2018: Reports of Practical Oncology and Radiotherapy
W-L Qian, D-J Zhou, Y Jiang, C Feng, Q Chen, H Wang, J-B Zhang, J-M Xu
AIM: To investigate the image quality of lower-extremity computed tomography (CT) angiography (CTA) with ultra-low radiation dose using the iterative model reconstruction (IMR) algorithm. MATERIALS AND METHODS: Lower-extremity CTA was acquired using a 256-multidetector CT system from 90 patients assigned into three groups: (1) the routine dose (RD) group: 120 kVp, automatic tube current modulation (ACTM) with an image quality index of 12, and filtered back projection (FBP); (2) the low-dose (LD) group: 80 kVp, ACTM with an image quality index of 1, and IMR; and (3) the ultra-low dose (ULD) group: 80 kVp, 20 mAs, and IMR...
September 6, 2018: Clinical Radiology
Oleg N Vassiliev, Stephen F Kry, He C Wang, Christine B Peterson, Joe Y Chang, Radhe Mohan
The purpose of this work was to investigate radiotherapy underdosing at the periphery of lung tumors, and differences in dose for treatments delivered with flattening filter-free (FFF) beams and with conventional flattened (FF) beams. The true differences between these delivery approaches, as assessed with Monte Carlo simulations, were compared to the apparent differences seen with clinical treatment planning algorithms AAA and Acuros XB. Dose was calculated in a phantom comprised of a chest wall, lung parenchyma, and a spherical tumor (tested diameters: 1, 3, and 5 cm)...
September 28, 2018: Physics in Medicine and Biology
Choonsik Lee, Gleb A Kuzmin, Jinyong Bae, Jianhua Yao, Elizabeth Mosher, Les R Folio
To develop an algorithm to automatically map CT scan locations of patients onto computational human phantoms to provide with patient-specific organ doses. We developed an algorithm that compares a two-dimensional skeletal mask generated from patient CTs with that of a whole body computational human phantom. The algorithm selected the scan locations showing the highest Dice Similarity Coefficient (DSC) calculated between the skeletal masks of a patient and a phantom. To test the performance of the algorithm, we randomly selected five sets of neck, chest, and abdominal CT images from the National Institutes of Health Clinical Center...
September 5, 2018: Journal of Digital Imaging: the Official Journal of the Society for Computer Applications in Radiology
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