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Physica Medica: PM

Sankar Arumugam, Mark Sidhom, Daniel Truant, Aitang Xing, Mark Udovitch, Lois Holloway
PURPOSE: To develop and validate a variable angle stereo image based position correction methodology in an X-ray based in-house online position monitoring system. MATERIALS AND METHODS: A stereo imaging module that enables 3D position determination and couch correction of the patient based on images acquired at any arbitrary angle and arbitrary angular separation was developed and incorporated to the in-house SeedTracker real-time position monitoring system. The accuracy of the developed system was studied by imaging an anthropomorphic phantom implanted with radiopaque markers set to known offset positions from its reference position in an Elekta linear accelerator (LA) and associated XVI imaging system...
January 7, 2017: Physica Medica: PM
José Olasolo-Alonso, Alejandro Vázquez-Galiñanes, Santiago Pellejero-Pellejero, José Fernando Pérez-Azorín
PURPOSE: This multi-institution study assessed the positioning accuracy of multileaf collimators (MLC) by analyzing log files. It determined the main machine parameters that affect MLC positioning errors for pre-TrueBeam (Clinac) and TrueBeam linacs. METHODS: Around 30,000 dIMRT and VMAT log files belonging to 6 linacs from 4 different centers were analyzed. An in-house software was used to calculate 95th percentile and RMS error values and their correlation with certain parameters such as maximum leaf speed, mean leaf speed and gantry angle...
January 5, 2017: Physica Medica: PM
V Gracanin, S Guatelli, D Prokopovich, A B Rosenfeld, A Berry
The Bonner Sphere Spectrometer (BSS) system is a well-established technique for neutron dosimetry that involves detection of thermal neutrons within a range of hydrogenous moderators. BSS detectors are often used to perform neutron field surveys in order to determine the ambient dose equivalent H*(10) and estimate health risk to personnel. There is a potential limitation of existing neutron survey techniques, since some detectors do not consider the direction of the neutron field, which can result in overly conservative estimates of dose in neutron fields...
January 2, 2017: Physica Medica: PM
Satoshi Abe, Yoshiki Kubota, Kei Shibuya, Yoshinari Koyama, Takanori Abe, Tatsuya Ohno, Takashi Nakano
PURPOSE: The aim of this study was to compare the dose-volume parameters of fiducial marker matching (MM) with vertebral body matching (VM) in patient positioning for carbon ion radiotherapy for primary hepatic cancer. MATERIALS AND METHODS: Twenty patients with primary hepatic cancer were retrospectively studied to assess changes in reproducibility of tumor position and dose distribution on two CT scans. One was for treatment planning and another was for dose confirmation, acquired the day before the first treatment day...
January 2, 2017: Physica Medica: PM
M E Capoulat, A J Kreiner
PURPOSE: Boron Neutron Capture Therapy (BNCT) requires neutron sources suitable for in-hospital siting. Low-energy particle accelerators working in conjunction with a neutron producing reaction are the most appropriate choice for this purpose. One of the possible nuclear reactions is (13)C(d,n)(14)N. The aim of this work is to evaluate the therapeutic capabilities of the neutron beam produced by this reaction, through a 30mA beam of deuterons of 1.45MeV. METHODS: A Beam Shaping Assembly design was computationally optimized...
December 31, 2016: Physica Medica: PM
R W Bouwman, M Goffi, R E van Engen, M J M Broeders, D R Dance, K C Young, W J H Veldkamp
PURPOSE: In mammography, images are processed prior to display. Model observers (MO) are candidates to objectively evaluate processed images if they can predict human observer performance for detail detection. The aim of this study was to investigate if the channelized Hotelling observer (CHO) can be configured to predict human observer performance in mammography like images. METHODS: The performance correlation between human observers and CHO has been evaluated using different channel-sets and by including aspects of the human visual system (HVS)...
December 28, 2016: Physica Medica: PM
Melek Zarifi, Susanna Guatelli, David Bolst, Brian Hutton, Anatoly Rosenfeld, Yujin Qi
In this paper we report a Geant4 simulation study to investigate the characteristic prompt gamma (PG) emission in a water phantom for real-time monitoring of the Bragg peak (BP) during proton beam irradiation. The PG production, emission spatial correlation with the BP, and position preference for detection with respect to the BP have been quantified in different PG energy windows as a function of proton pencil-beam energy from 100 to 200MeV. The PG response to small BP shifts was evaluated using a 2cm-thick slab with different human body materials embedded in a water phantom...
December 24, 2016: Physica Medica: PM
Aimee McNamara, Changran Geng, Robert Turner, Jose Ramos Mendez, Joseph Perl, Kathryn Held, Bruce Faddegon, Harald Paganetti, Jan Schuemann
Computational simulations offer a powerful tool for quantitatively investigating radiation interactions with biological tissue and can help bridge the gap between physics, chemistry and biology. The TOPAS collaboration is tackling this challenge by extending the current Monte Carlo tool to allow for sub-cellular in silico simulations in a new extension, TOPAS-nBio. TOPAS wraps and extends the Geant4 Monte Carlo simulation toolkit and the new extension allows the modeling of particles down to vibrational energies (∼2eV) within realistic biological geometries...
December 22, 2016: Physica Medica: PM
A Maldera, P De Marco, P E Colombo, D Origgi, A Torresin
The aim of this work was to evaluate how different acquisition geometries and reconstruction parameters affect the performance of four digital breast tomosynthesis (DBT) systems (Senographe Essential - GE, Mammomat Inspiration - Siemens, Selenia Dimensions - Hologic and Amulet Innovality - Fujifilm) on the basis of a physical characterization. Average Glandular Dose (AGD) and image quality parameters such as in-plane/in-depth resolution, signal difference to noise ratio (SDNR) and artefact spread function (ASF) were examined...
December 20, 2016: Physica Medica: PM
Oliver Faust, U Rajendra Acharya, Vidya K Sudarshan, Ru San Tan, Chai Hong Yeong, Filippo Molinari, Kwan Hoong Ng
The diagnosis of Coronary Artery Disease (CAD), Myocardial Infarction (MI) and carotid atherosclerosis is of paramount importance, as these cardiovascular diseases may cause medical complications and large number of death. Ultrasound (US) is a widely used imaging modality, as it captures moving images and image features correlate well with results obtained from other imaging methods. Furthermore, US does not use ionizing radiation and it is economical when compared to other imaging modalities. However, reading US images takes time and the relationship between image and tissue composition is complex...
December 20, 2016: Physica Medica: PM
Pedro L Esquinas, Cristina Rodríguez-Rodríguez, José Carlos De La Vega, Mehrdad Bokharaei, Katayoun Saatchi, Maryam Shirmohammad, Urs O Häfeli, Vesna Sossi, Anna Celler
PURPOSE: The goal of this study was to investigate the performance of a pre-clinical SPECT/PET/CT system for (188)Re imaging. METHODS: Phantom experiments were performed aiming to assess the characteristics of two multi-pinhole collimators: ultra-high resolution collimator (UHRC) and high-energy ultra high resolution collimator (HE-URHC) for imaging (188)Re. The spatial resolution, image contrast and contrast-to-noise ratio (CNR) were investigated using micro-Jaszczak phantoms...
December 19, 2016: Physica Medica: PM
Luisa Altabella, Cristian Borrazzo, Marco Carnì, Nicola Galea, Marco Francone, Andrea Fiorelli, Elisabetta Di Castro, Carlo Catalano, Iacopo Carbone
PURPOSE: Cardiac magnetic resonance (CMR) is a useful non-invasive tool for characterizing tissues and detecting myocardial fibrosis and edema. Estimation of extracellular volume fraction (ECV) using T1 sequences is emerging as an accurate biomarker in cardiac diseases associated with diffuse fibrosis. In this study, automatic software for T1 and ECV map generation consisting of an executable file was developed and validated using phantom and human data. METHODS: T1 mapping was performed in phantoms and 30 subjects (22 patients and 8 healthy subjects) on a 1...
December 18, 2016: Physica Medica: PM
Robert Bujila, Annette Fransson, Gavin Poludniowski
PURPOSE: To investigate two methods of approximating the Modulation Transfer Function (MTF) and Noise Power Spectrum (NPS) in computed tomography (CT) for a range of scan parameters, from limited image acquisitions. METHODS: The two methods consist of 1) using a linear systems approach to approximate the NPS for different filtered backprojection (FBP) kernels with a filter function derived from the kernel ratio of determined MTFs and 2) using an empirical fitted model to approximate the MTF and NPS...
December 18, 2016: Physica Medica: PM
Kentaro Miki, Mai Fukahori, Motoki Kumagai, Shigeru Yamada, Shinichiro Mori
PURPOSE: Pancreatic tumor treatment dose distribution variations associated with supine and prone patient positioning were evaluated. METHODS: A total of 33 patients with pancreatic tumors who underwent CT in the supine and prone positions were analyzed retrospectively. Gross tumor volume (GTV), planning target volume (PTV), and organs at risk (OARs) (duodenum and stomach) were contoured. The prescribed dose of 55.2Gy (RBE) was planned from four beam angles (0°, 90°, 180°, and 270°)...
December 18, 2016: Physica Medica: PM
Kazuhiro Arai, Noriyuki Kadoya, Takahiro Kato, Hiromitsu Endo, Shinya Komori, Yoshitomo Abe, Tatsuya Nakamura, Hitoshi Wada, Yasuhiro Kikuchi, Yoshihiro Takai, Keiichi Jingu
The aim of this study was to confirm On-Board Imager cone-beam computed tomography (CBCT) using the histogram-matching algorithm as a useful method for proton dose calculation. We studied one head and neck phantom, one pelvic phantom, and ten patients with head and neck cancer treated using intensity-modulated radiation therapy (IMRT) and proton beam therapy. We modified Hounsfield unit (HU) values of CBCT and generated two modified CBCTs (mCBCT-RR, mCBCT-DIR) using the histogram-matching algorithm: modified CBCT with rigid registration (mCBCT-RR) and that with deformable image registration (mCBCT-DIR)...
December 17, 2016: Physica Medica: PM
A Ben Abdennebi, S Aubry, L Ounalli, M S Fayache, E Delabrousse, Y Petegnief
PURPOSE: To estimate fetal absorbed doses for pregnant women pelvimetry, a comparative study between EOS imaging system and low-dose spiral CT-scanner was carried out. For this purpose three different studies were investigated: in vivo, in vitro and Monte Carlo calculations. METHODS: In vivo dosimetry was performed, using OSL NanoDot dosimeters, to determine the dose to the skin of twenty pregnant women. In vitro studies were established by using a cubic phantom of water, in order to estimate the out of field doses...
December 16, 2016: Physica Medica: PM
Umberto Ricardi, Serena Badellino, Andrea Riccardo Filippi
Stereotactic Body Radiotherapy (SBRT) is a well established therapeutic option for patients affected with peripheral early stage non-small cell lung cancer (NSCLC), given the positive clinical evidence accumulated so far on its efficacy and safety. SBRT is regarded as the best choice for inoperable patients, and could also be offered as an alternative to surgery to selected operable patients. More recently, its use for lung metastases progressively increased, and SBRT is now regarded as a low toxic and highly effective local therapy for lung oligometastases from different primary tumors, especially colorectal cancer...
November 30, 2016: Physica Medica: PM
Antonella Fogliata, Luca Cozzi
This review addresses the theme of dose calculation accuracy in the case of the stereotactic treatment of lung lesions. Based on the classical categories of type "a", "b" and "c" algorithms (according to their degree of complexity in the management of charged particle transport), a summary of findings from literature is reported. Two main critical areas have been identified: the use of small fields and the presence of low density medium. Concerning the latter point, the algorithm accuracy is intrinsic of the algorithm core, and, notwithstanding the materials discretization and their chemical composition knowledge, type "c" are, at the most, able to reproduce the actual physical dose distribution in heterogeneous media...
November 24, 2016: Physica Medica: PM
Eeva Boman, Maija Rossi, Mikko Haltamo, Tanja Skyttä, Mika Kapanen
PURPOSE: To investigate different volumetric modulated arc therapy (VMAT) field designs for lymph node positive breast cancer patients when compared to conventional static fields and standard VMAT designs. METHODS: Nineteen breast cancer patients with lymph node involvement (eleven left and eight right sided) were retrospectively analyzed with different arc designs. Proposed split arc designs with total rotations of 2×190° and 2×240° were compared to conventional field in field (FinF) and previously published non-split arc techniques with the same amount of total rotations...
October 28, 2016: Physica Medica: PM
Francesco Cadini, David Bolst, Susanna Guatelli, Chris Beltran, Michael Jackson, Anatoly B Rosenfeld
In this work, we used the Monte Carlo-based Geant4 simulation toolkit to calculate the ambient dose equivalents due to the secondary neutron field produced in a new projected proton therapy facility. In particular the facility geometry was modeled in Geant4 based on the CAD design. Proton beams were originated with an energy of 250MeV in the gantry rooms with different angles with respect to the patient; a fixed 250MeV proton beam was also modeled. The ambient dose equivalent was calculated in several locations of interest inside and outside the facility, for different scenarios...
December 2016: Physica Medica: PM
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