Read by QxMD icon Read

Physica Medica: PM

Rowan M Thomson, Iwan Kawrakow
PURPOSE: Classical trajectory Monte Carlo (MC) simulations modelling radiation-induced damage on subcellular length scales ignore quantum effects that may be non-negligible as electron energy decreases below 1 keV. This work investigates quantum mechanical (QM) treatments of low-energy electron transport in condensed media, comparing with classical MC. METHODS: QM calculations involve a simplified model of electron transport in water with a plane wave incident on a cylinder ("droplet") consisting of a cluster of point scatterers (positioned randomly but constrained by a minimum separation, dmin )...
July 12, 2018: Physica Medica: PM
Hyun Joon Choi, Hyun-Tai Chung, Jason W Sohn, Chul Hee Min
Leksell GammaPlan was specifically designed for Gamma Knife (GK) radiosurgery planning, but it has limited accuracy for estimating the dose distribution in inhomogeneous areas, such as the embolization of arteriovenous malformations. We aimed to develop an independent patient dose validation system based on a patient-specific model, constructed using a DICOM-RT interface and the Geant4 toolkit. Leksell Gamma Knife Perfexion was designed in Geant4.10.00 and includes a DICOM-RT interface. Output factors for each collimator in a sector and dose distributions in a spherical water phantom calculated using a Monte Carlo (MC) algorithm were compared with the output factors calculated by the tissue maximum ratio (TMR) 10 algorithm and dose distributions measured using film, respectively...
June 15, 2018: Physica Medica: PM
Liset de la Fuente Rosales, Sebastien Incerti, Ziad Francis, Mario A Bernal
The use of Monte Carlo (MC) simulations remains a powerful tool to study the biological effects induced by ionizing radiation on living beings. Several MC codes are commonly used in research fields such as nanodosimetry, radiotherapy, radiation protection, and space radiation. This work presents an enhancement of an existing model [1] for radiobiological purposes, to account for the indirect DNA damage induced by ionizing particles. The Geant4-DNA simulation toolkit was used to simulate the physical, pre-chemical, and chemical stages of early DNA damage induced by protons and α-particles...
June 13, 2018: Physica Medica: PM
Antonio Sarno, Giovanni Mettivier, Raffaele M Tucciariello, Kristina Bliznakova, John M Boone, Ioannis Sechopoulos, Francesca Di Lillo, Paolo Russo
PURPOSE: In cone-beam computed tomography dedicated to the breast (BCT), the mean glandular dose (MGD) is the dose metric of reference, evaluated from the measured air kerma by means of normalized glandular dose coefficients (DgNCT ). This work aimed at computing, for a simple breast model, a set of DgNCT values for monoenergetic and polyenergetic X-ray beams, and at validating the results vs. those for patient specific digital phantoms from BCT scans. METHODS: We developed a Monte Carlo code for calculation of monoenergetic DgNCT coefficients (energy range 4...
June 7, 2018: Physica Medica: PM
Nicole L Ackerman, Liset de la Fuente Rosales, Nadia Falzone, Katherine A Vallis, Mario A Bernal
Targeted α-therapy (TAT) could be delivered early to patients who are at a high-risk for developing brain metastases, targeting the areas of the vasculature where tumor cells are penetrating into the brain. We have utilized a Monte Carlo model representing brain vasculature to calculate physical dose and DNA damage from the α-emitters 225 Ac and 212 Pb. The micron-scale dose distributions from all radioactive decay products were modeled in Geant4, including the eV-scale interactions using the Geant4-DNA models...
May 25, 2018: Physica Medica: PM
Sara Gholampourkashi, Joanna E Cygler, Bernie Lavigne, Emily Heath
PURPOSE: To verify the accuracy of 4D Monte Carlo (MC) simulations, using the 4DdefDOSXYZnrc user code, in a deforming anatomy. We developed a tissue-equivalent and reproducible deformable lung phantom and evaluated 4D simulations of delivered dose to the phantom by comparing calculations against measurements. METHODS: A novel deformable phantom consisting of flexible foam, emulating lung tissue, inside a Lucite external body was constructed. A removable plug, containing an elastic tumor that can hold film and other dosimeters, was inserted in the phantom...
May 15, 2018: Physica Medica: PM
E Fiorina, V Ferrero, F Pennazio, G Baroni, G Battistoni, N Belcari, P Cerello, N Camarlinghi, M Ciocca, A Del Guerra, M Donetti, A Ferrari, S Giordanengo, G Giraudo, A Mairani, M Morrocchi, C Peroni, A Rivetti, M D Da Rocha Rolo, S Rossi, V Rosso, P Sala, G Sportelli, S Tampellini, F Valvo, R Wheadon, M G Bisogni
Hadrontherapy is a method for treating cancer with very targeted dose distributions and enhanced radiobiological effects. To fully exploit these advantages, in vivo range monitoring systems are required. These devices measure, preferably during the treatment, the secondary radiation generated by the beam-tissue interactions. However, since correlation of the secondary radiation distribution with the dose is not straightforward, Monte Carlo (MC) simulations are very important for treatment quality assessment...
May 7, 2018: Physica Medica: PM
G Paternò, P Cardarelli, A Contillo, M Gambaccini, A Taibi
An extension to Geant4 Monte Carlo code was developed to take into account inter-atomic (molecular) interference effects in X-ray coherent scattering. Based on our previous works, the developed code introduces a set of form factors including interference effects for a selected variety of amorphous materials useful for medical applications, namely various tissues and plastics used to build phantoms. The code is easily upgradable in order to include new materials and offers the possibility to model a generic tissue as a combination of a set of four basic components...
April 30, 2018: Physica Medica: PM
A Sarno, G Mettivier, F Di Lillo, K Bliznakova, I Sechopoulos, P Russo
PURPOSE: To compare, via Monte Carlo simulations, homogeneous and non-homogenous breast models adopted for mean glandular dose (MGD) estimates in mammography vs. patient specific digital breast phantoms. METHODS: We developed a GEANT4 Monte Carlo code simulating four homogenous cylindrical breast models featured as follows: (1) semi-cylindrical section enveloped in a 5-mm adipose layer; (2) semi-elliptical section with a 4-mm thick skin; (3) semi-cylindrical section with a 1...
April 25, 2018: Physica Medica: PM
Shunsuke Yonai, Naruhiro Matsufuji, Keiichi Akahane
PURPOSE: The aim of this work was to estimate typical dose equivalents to out-of-field organs during carbon-ion radiotherapy (CIRT) with a passive beam for prostate cancer treatment. Additionally, sensitivity analyses of organ doses for various beam parameters and phantom sizes were performed. METHODS: Because the CIRT out-of-field dose depends on the beam parameters, the typical values of those parameters were determined from statistical data on the target properties of patients who received CIRT at the Heavy-Ion Medical Accelerator in Chiba (HIMAC)...
April 23, 2018: Physica Medica: PM
Francesco Tommasino, Francesco Fellin, Stefano Lorentini, Paolo Farace
PURPOSE: Proton therapy for the treatment of breast cancer is acquiring increasing interest, due to the potential reduction of radiation-induced side effects such as cardiac and pulmonary toxicity. While several in silico studies demonstrated the gain in plan quality offered by pencil beam scanning (PBS) compared to passive scattering techniques, the related dosimetric uncertainties have been poorly investigated so far. METHODS: Five breast cancer patients were planned with Raystation 6 analytical pencil beam (APB) and Monte Carlo (MC) dose calculation algorithms...
June 2018: Physica Medica: PM
L Presotto, V Bettinardi, E De Bernardi, M L Belli, G M Cattaneo, S Broggi, C Fiorino
PURPOSE: The analysis of PET images by textural features, also known as radiomics, shows promising results in tumor characterization. However, radiomic metrics (RMs) analysis is currently not standardized and the impact of the whole processing chain still needs deep investigation. We characterized the impact on RM values of: i) two discretization methods, ii) acquisition statistics, and iii) reconstruction algorithm. The influence of tumor volume and standardized-uptake-value (SUV) on RM was also investigated...
June 2018: Physica Medica: PM
Michael P Grams, Luis E Fong de Los Santos
PURPOSE: To describe the design and clinical use of a rotational phantom for dosimetric verification of IMRT/VMAT treatment plans using radiochromic film. METHODS: A solid water cylindrical phantom was designed with separable upper and lower halves and rests on plastic bearings allowing for 360° rotation about its central axis. The phantom accommodates a half sheet of radiochromic film, and by rotating the cylinder, the film can be placed in any plane between coronal and sagittal...
June 2018: Physica Medica: PM
Shinichi Nakayama, Hajime Monzen, Yuichi Onishi, Soichiro Kaneshige, Ikuo Kanno
The purpose of this study was a dosimetric validation of the Vero4DRT for brain stereotactic radiotherapy (SRT) with extremely small fields calculated by the treatment planning system (TPS) iPlan (Ver.4.5.1; algorithm XVMC). Measured and calculated data (e.g. percentage depth dose [PDD], dose profile, and point dose) were compared for small square fields of 30 × 30, 20 × 20, 10 × 10 and 5 × 5 mm2 using ionization chambers of 0.01 or 0.04 cm3 and a diamond detector. Dose verifications were performed using an ionization chamber and radiochromic film (EBT3; the equivalent field sizes used were 8...
June 2018: Physica Medica: PM
Ji Sung Jang, Hyung Jin Yang, Hyun Jung Koo, Sung Ho Kim, Chan Rok Park, Suk Hwan Yoon, So Youn Shin, Kyung-Hyun Do
PURPOSE: Dose reduction using additional filters with high kilovoltage peak (kVp) for abdominal digital radiography has received much attention recently. We evaluated image quality with dose reduction in abdominal digital radiography by using high kVp and additional copper filters at a tertiary hospital. METHODS: Between June 2016 and July 2016, 82 patients underwent abdominal digital radiography using 80 kVp in X-ray room 1 and 82 were imaged using 92 kVp with 0...
June 2018: Physica Medica: PM
Amir Ghabrial, Daniel Franklin, Habib Zaidi
OBJECTIVE: The purpose of this study is to validate a Monte Carlo simulation model for the clinical Siemens Biograph mCT PET scanner using the GATE simulation toolkit, and to evaluate the performance of six different scintillation materials in this model using the National Electrical Manufactures Association (NEMA) NU 2-2007 protocol. METHODS: A model of the Biograph mCT PET detection system and its geometry was developed. NEMA NU 2-2007 phantoms were also modelled...
June 2018: Physica Medica: PM
Fei Yang, Nesrin Dogan, Radka Stoyanova, John Chetley Ford
The purpose of this study was to examine the dependence of image texture features on MR acquisition parameters and reconstruction using a digital MR imaging phantom. MR signal was simulated in a parallel imaging radiofrequency coil setting as well as a single element volume coil setting, with varying levels of acquisition noise, three acceleration factors, and four image reconstruction algorithms. Twenty-six texture features were measured on the simulated images, ground truth images, and clinical brain images...
June 2018: Physica Medica: PM
Shin Miyakawa, Hidenobu Tachibana, Shunsuke Moriya, Tomoyuki Kurosawa, Teiji Nishio
PURPOSE: This study aimed to evaluate different deformable image registration (DIR) parameters for the open-source NiftyReg package in its application to DIR-based ventilation imaging. METHODS: Two three-dimensional (3D)-computed tomography (CT) scans of a non-rigid air-ventilating phantom were acquired at peak exhalation and peak inhalation, with xenon (Xe) gas being used as an air-based contrast agent. We compared four different sets of DIR parameters, including one set with two-step deformation and three sets with four-step deformation...
June 2018: Physica Medica: PM
Kuo Men, Tao Zhang, Xinyuan Chen, Bo Chen, Yu Tang, Shulian Wang, Yexiong Li, Jianrong Dai
PURPOSE: To train and evaluate a very deep dilated residual network (DD-ResNet) for fast and consistent auto-segmentation of the clinical target volume (CTV) for breast cancer (BC) radiotherapy with big data. METHODS: DD-ResNet was an end-to-end model enabling fast training and testing. We used big data comprising 800 patients who underwent breast-conserving therapy for evaluation. The CTV were validated by experienced radiation oncologists. We performed a fivefold cross-validation to test the performance of the model...
June 2018: Physica Medica: PM
Wei Zou, Brendan Burgdorf, Ning J Yue, Lingshu Yin, Miao Zhang, Atif Khan, Salma K Jabbour, James McDonough, Lei Dong, Boon-Keng Kevin Teo
PURPOSE: Passive scattering proton radiotherapy utilizes beam-specific compensators to shape the dose to the distal end of the tumor target. These compensators typically require therapists to enter the treatment room to mount between beams. This study investigates a novel approach that utilizes a single patient-specific bolus to accomplish the role of multi-field compensators to improve the efficiency of the treatment delivery. METHODS: Ray-tracing from the proton virtual source was used to convert the beam-specific compensators (mounted on the gantry nozzle) into an equivalent bolus thickness on the patient surface...
June 2018: Physica Medica: PM
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"