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Physica Medica: PM

I Kyriakou, V Ivanchenko, D Sakata, M C Bordage, S Guatelli, S Incerti, D Emfietzoglou
The Geant4 toolkit offers a range of electromagnetic (EM) models for simulating the transport of charged particles down to sub-keV energies. They can be divided to condensed-history (CH) models (like the Livermore and Penelope models) and the track-structure (TS) models included in the Geant4-DNA low-energy extension of Geant4. Although TS models are considered the state-of-the-art for nanoscale electron transport, they are difficult to develop, computationally intensive, and commonly tailored to a single medium (e...
January 11, 2019: Physica Medica: PM
Carsten Nieder
Except for straightforward palliative indications such as painful bone metastases, re-irradiation is often characterized by a narrow therapeutic window and the potential for decreased efficacy and increased toxicity, especially if the cumulative total dose from both courses is high. Second re-irradiations tend to pose even bigger challenges and are thus offered in a restrictive manner to highly selected patients on a case-by-case basis. Normal tissue dose constraints are still an area of active investigation...
January 8, 2019: Physica Medica: PM
Simone Busoni, Luca Fedeli, Giacomo Belli, Elisabetta Genovese, Vittorio Cannatà, Cesare Gori, Francesco Rossi
Pre and post-operative exposure levels of medical staff and people from public in intra-operative Ru-106 ophthalmic brachytherapy are reported, together with attenuation properties of selected shielding materials. In particular radiation exposure of workers during plaque transportation and during medical assistance of implanted plaque patient was measured. Taking into account dose rates and considering standard assistance procedure of hospitalized patients, the exposure of medical staff and people of the public were evaluated for a given workload...
December 17, 2018: Physica Medica: PM
R Castriconi, C Fiorino, S Broggi, C Cozzarini, N Di Muzio, R Calandrino, G M Cattaneo
PURPOSE: To develop and apply a stepping approach for the validation of Knowledge-based (KB) models for planning optimization: the method was applied to the case of concomitant irradiation of pelvic nodes and prostate + seminal-vesicles bed irradiation in post-prostatectomy patients. METHODS: The clinical VMAT plans of 52 patients optimized by two reference planners were selected to generate a KB-model (RapidPlan, v.13.5 Varian). A stepping-validation approach was followed by comparing KB-generated plans (with and without planner-interaction, RP and only-RP respectively) against delivered clinical plans (RA)...
December 10, 2018: Physica Medica: PM
Thomas Henry, Jakob Ödén
PURPOSE: Interlaced beams have previously been proposed for delivering proton grid therapy. This study aims to assess dose-averaged LET (LETd ) and RBE-weighted dose (DRBE ) distributions of such beam geometries, and compare them with conventional intensity modulated proton therapy (IMPT). METHODS: IMPT plans and four different interlaced proton grid therapy plans were generated for five patient cases (esophagus, lung, liver, prostate, anus). The constant RBE = 1...
November 22, 2018: Physica Medica: PM
Davide Gurrera, Karmenos K Gallias, Marco Spanò, Boris F Abbate, Francesca D'Alia, Giuseppina Iacoviello, Vittorio Caputo
Does the exposure of magnetic resonance imaging personnel to static magnetic fields fully comply with Directive 2013/35/EU? Despite the obligation to satisfy this question, a general answer cannot be provided, nor are final satisfying good practices methods for exposure assessment currently available. In order to contribute to fix this problem, three different 1.5 T scanners are analysed and - by a new theoretical insight - a positive answer is provided.
November 20, 2018: Physica Medica: PM
Mika Kortesniemi, Virginia Tsapaki, Annalisa Trianni, Paolo Russo, Ad Maas, Hans-Erik Källman, Marco Brambilla, John Damilakis
Big data and deep learning will profoundly change various areas of professions and research in the future. This will also happen in medicine and medical imaging in particular. As medical physicists, we should pursue beyond the concept of technical quality to extend our methodology and competence towards measuring and optimising the diagnostic value in terms of how it is connected to care outcome. Functional implementation of such methodology requires data processing utilities starting from data collection and management and culminating in the data analysis methods...
November 16, 2018: Physica Medica: PM
Elham Karimi Ghodoosi, Calogero D'Alessandria, Ye Li, Alexandra Bartel, Markus Köhner, Vera Höllriegl, Nassir Navab, Matthias Eiber, Wei Bo Li, Eric Frey, Sibylle Ziegler
PURPOSE: The objective of this study was to evaluate the image degrading factors in quantitative 177 Lu SPECT imaging when using both main gamma photopeak energies. METHODS: Phantom measurements with two different vials containing various calibrated activities in air or water were performed to derive a mean calibration factor (CF) for large and small volumes of interest (VOIs). In addition, Monte Carlo simulations were utilized to investigate the effect of scatter energy window width, scatter correction method, such as effective scatter source estimation (ESSE) and triple energy window (TEW), and attenuation map on the quantification of 177 Lu...
December 2018: Physica Medica: PM
Shunsuke Moriya, Hidenobu Tachibana, Kenji Hotta, Naoki Nakamura, Takeji Sakae, Tetsuo Akimoto
PURPOSE: The purpose of this study was to design and develop a new range optimization for target and organs at risk (OARs) in dynamic adaptive proton beam therapy (PBT). METHODS: The new range optimization for target and OARs (RO-TO) was optimized to maintain target dose coverage but not to increase the dose exposure of OARs, while the other procedure, range optimization for target (RO-T), only focused on target dose coverage. A retrospective analysis of a patient who received PBT for abdominal lymph node metastases was performed to show the effectiveness of our new approach...
December 2018: Physica Medica: PM
Hidenobu Tachibana, Yukihiro Uchida, Ryuta Miyakawa, Mikiko Yamashita, Aya Sato, Satoshi Kito, Daiki Maruyama, Shigetoshi Noda, Toru Kojima, Hiroshi Fukuma, Ryosuke Shirata, Hiroyuki Okamoto, Mitsuhiro Nakamura, Yuma Takada, Hironori Nagata, Naoki Hayashi, Ryo Takahashi, Daisuke Kawai, Masanobu Itano
PURPOSE: This report covers the first multi-institutional study of independent monitor unit (MU)/dose calculation verification for the CyberKnife, Vero4DRT, and TomoTherapy radiotherapy delivery systems. METHODS: A total of 973 clinical treatment plans were collected from 12 institutions. Commercial software employing the Clarkson algorithm was used for verification after a measurement validation study, and the doses from the treatment planning systems (TPSs) and verification programs were compared on the basis of the mean value ± two standard deviations...
December 2018: Physica Medica: PM
Mirjana Josipovic, Gitte Fredberg Persson, Jonas Scherman Rydhög, Bob Smulders, Jakob Borup Thomsen, Marianne Camille Aznar
PURPOSE: Evaluating performance of modern dose calculation algorithms in SBRT and locally advanced lung cancer radiotherapy in free breathing (FB) and deep inspiration breath hold (DIBH). METHODS: For 17 patients with early stage and 17 with locally advanced lung cancer, a plan in FB and in DIBH were generated with Anisotropic Analytical Algorithm (AAA). Plans for early stage were 3D-conformal SBRT, 45 Gy in 3 fractions, prescribed to 95% isodose covering 95% of PTV and aiming for 140% dose centrally in the tumour...
December 2018: Physica Medica: PM
Gwennaëlle Marin, Bruno Vanderlinden, Ioannis Karfis, Thomas Guiot, Zena Wimana, Nick Reynaert, Stefaan Vandenberghe, Patrick Flamen
PURPOSE: Peptide receptor radionuclide therapy with 177 Lu-DOTATATE has become a standard treatment modality in neuroendocrine tumours (NETs). No consensus has yet been reached however regarding the absorbed dose threshold for lesion response, the absorbed dose limit to organs-at-risk, and the optimal fractionation and activity to be administered. This is partly due to a lack of uniform and comparable dosimetry protocols. The present article details the development of an organ-at-risk dosimetry procedure, which could be implemented and used routinely in a clinical context...
December 2018: Physica Medica: PM
Shingo Ohira, Hayate Washio, Masashi Yagi, Tsukasa Karino, Kenji Nakamura, Yoshihiro Ueda, Masayoshi Miyazaki, Masahiko Koizumi, Teruki Teshima
PURPOSE: Assess the accuracy for quantitative measurements of electron density relative to water (ρe /ρe,w ), effective atomic number (Zeff ) and stopping power ratio relative to water (SPRw ) using a dual-layer computed tomography (DLCT) system. METHODS AND MATERIALS: A tissue characterization phantom was scanned using DLCT with varying scanning parameters (i.e., tube voltage, rotation time, CTDIvol , and scanning mode) and different reference materials. Then, electron density ρe /ρe,w and atomic number Zeff images were reconstructed, and their values were determined for each reference materials...
December 2018: Physica Medica: PM
Laura Masi, Margherita Zani, Raffaela Doro, Silvia Calusi, Vanessa Di Cataldo, Ivano Bonucci, Samantha Cipressi, Giulio Francolini, Pierluigi Bonomo, Lorenzo Livi
PURPOSE: This study evaluated the plan quality of CyberKnife MLC-based treatment planning in comparison to the Iris collimator for abdominal and pelvic SBRT. Multiple dosimetric parameters were considered together with a global scoring index validated by clinical scoring. METHODS AND MATERIALS: Iris and MLC plans were created for 28 liver, 15 pancreas and 13 prostate cases including a wide range of PTV sizes (24-643 cm3 ). Plans were compared in terms of coverage, conformity (nCI), dose gradient (R50%), homogeneity (HI), OAR doses, PTV gEUD, MU, treatment time both estimated by TPS (tTPS ) and measured...
December 2018: Physica Medica: PM
Sonja Dieterich, Olga Green, Jeremy Booth
The technology of treating SBRT targets that move with respiration has undergone profound changes over the last 20 years. This review article summarizes modern image guidance to localize the target in real-time to account for intra-fraction motion. The state-of-the art respiratory motion compensation techniques will be discussed, including the determination and application of appropriate margins. This includes compression, gating and breath-hold, including the use of audiovisual feedback to manage motion...
December 2018: Physica Medica: PM
A Vanhanen, H Syrén, M Kapanen
The aim of this study was to evaluate the localization accuracy of electromagnetic (EM) tracking systems RayPilot (Micropos Medical AB) and Calypso (Varian Medical Systems) in prostate cancer radiotherapy. The accuracy was assessed by comparing couch shifts obtained with the EM methods to the couch shifts determined by simultaneous fiducial marker (FM) based orthogonal kilovoltage (kV) imaging. Agreement between the methods was compared using Bland-Altman analysis. Interfractional positional stability of the FMs, RayPilot transmitters and Calypso transponders was investigated...
December 2018: Physica Medica: PM
Makoto Sakai, Raj Kumar Parajuli, Mikiko Kikuchi, Mitsutaka Yamaguchi, Yuto Nagao, Naoki Kawachi, Kazuo Arakawa, Takashi Nakano
INTRODUCTION: We have been developing a medical imaging technique using a Compton camera, which is expected to reconstruct three-dimensional images. If the number of views is not sufficient, star-shaped artifacts (streak artifacts) could arise in cross-sectional images. Therefore, we estimated the point spread function (PSF) of cross-sectional Compton images and the effect of the number of views by Monte Carlo simulations and experimental studies. MATERIALS AND METHODS: A cross-sectional Compton image was reconstructed using a dataset comprising 719 view directions and PSF was analyzed using a radial distribution...
December 2018: Physica Medica: PM
Stefano Riga, Gianfranco Cicoria, Davide Pancaldi, Federico Zagni, Sara Vichi, Michele Dassenno, Luca Mora, Filippo Lodi, Maria Pia Morigi, Mario Marengo
PURPOSE: In recent years the use of 68 Ga (t1/2  = 67.84 min, β+ : 88.88%) for the labelling of different PET radiopharmaceuticals has significantly increased. This work aims to evaluate the feasibility of the production of 68 Ga via the 68 Zn(p,n)68 Ga reaction by proton irradiation of an enriched zinc solution, using a biomedical cyclotron, in order to satisfy its increasing demand. METHODS: Irradiations of 1.7 Msolution of 68 Zn(NO3 )2 in 0.2 N HNO3 were conducted with a GE PETtrace cyclotron using a slightly modified version of the liquid target used for the production of fluorine-18...
November 2018: Physica Medica: PM
Elisabetta Cagni, Andrea Botti, Yibing Wang, Mauro Iori, Steven F Petit, Ben J M Heijmen
PURPOSE: Treatment plans manually generated in clinical routine may suffer from variations and inconsistencies in quality. Using such plans for validating a DVH prediction algorithm might obscure its intrinsic prediction accuracy. In this study we used a recently published large database of Pareto-optimal prostate cancer plans to assess the prediction accuracy of a commercial knowledge-based DVH prediction algorithm, RapidPlan. The database plans were consistently generated with automated planning using an independent optimizer, and can be considered as aground truth of plan quality...
November 2018: Physica Medica: PM
Androniki Kozana, Themis Boursianis, George Kalaitzakis, Maria Raissaki, Thomas G Maris
PURPOSE: Tο fabricate a tissue-mimicking phantom simulating the MR relaxation times of neonatal gray and white matter at 1.5 T, for the optimization of clinical Τ1 weighted (T1w) and T2 weighted (T2w) sequences. METHODS: Numerous agarose gel solutions, doped with paramagnetic Gadopentetic acid (Gd-DTPA) ions, underwent quantitative relaxometry with a Turbo-Inversion-Recovery Spin-Echo (TIRSE) sequence and a Car-Purcell-Meiboom-Gill (CPMG) sequence for T1 and T2 measurements, respectively...
November 2018: Physica Medica: PM
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