bluuebunny/crossref_metadata_2025 huggingface dataset:
Quality control of VMAT synchronization using portal imaging
Authors: Bedford James L. , Chajecka‐Szczygielska Honorata , Thomas Michael D. R.
Published: February 2017

For accurate delivery of volumetric‐modulated arc therapy (VMAT), the gantry position should be synchronized with the multileaf collimator (MLC) leaf positions and the dose rate. This study, therefore, aims to implement quality control (QC) of VMAT synchronization, with as few arcs as possible and with minimal data handling time, using portal imaging. A steel bar of diameter 12 mm is accurately positioned in the G–T direction, 80 mm laterally from the isocenter. An arc prescription irradiates the bar with a field during a complete 360° arc, so as to cast a shadow of the bar onto the portal imager. This results in a sinusoidal sweep of the field and shadow across the portal imager and back. The method is evaluated by simulating gantry position errors of 1°–9° at one control point, dose errors of 2 monitor units to 20 monitor units (MU) at one control point (0.3%–3% overall), and MLC leaf position errors of 1 mm ‐ 6 mm at one control point. Inhomogeneity metrics are defined to characterize the synchronization of all leaves and of individual leaves with respect to the complete set. Typical behavior is also investigated for three models of accelerator. In the absence of simulated errors, the integrated images show uniformity, and with simulated delivery errors, irregular patterns appear. The inhomogeneity metrics increase by 67% due to a 4° gantry position error, 33% due to an 8 MU (1.25%) dose error, and 70% due to a 2 mm MLC leaf position error. The method is more sensitive to errors at gantry angle 90°/270° than at 0°/180° due to the geometry of the test. This method provides fast and effective VMAT QC suitable for inclusion in a monthly accelerator QC program. The test is able to detect errors in the delivery of individual control points, with the possibility of using movie images to further investigate suspicious image features.

PACS numbers: 87.55.Qr, 87.56.bd, 87.56.Fc
Compliance with AAPM Practice Guideline 1.a: CT Protocol Management and Review — from the perspective of a university hospital
Authors: Szczykutowicz Timothy P. , Bour Robert K. , Pozniak Myron , Ranallo Frank N.
Published: February 2017

The purpose of this paper is to describe our experience with the AAPM Medical Physics Practice Guideline 1.a: “CT Protocol Management and Review Practice Guideline”. Specifically, we will share how our institution's quality management system addresses the suggestions within the AAPM practice report. We feel this paper is needed as it was beyond the scope of the AAPM practice guideline to provide specific details on fulfilling individual guidelines. Our hope is that other institutions will be able to emulate some of our practices and that this article would encourage other types of centers (e.g., community hospitals) to share their methodology for approaching CT protocol optimization and quality control. Our institution had a functioning CT protocol optimization process, albeit informal, since we began using CT. Recently, we made our protocol development and validation process compliant with a number of the ISO 9001:2008 clauses and this required us to formalize the roles of the members of our CT protocol optimization team. We rely heavily on PACS‐based IT solutions for acquiring radiologist feedback on the performance of our CT protocols and the performance of our CT scanners in terms of dose (scanner output) and the function of the automatic tube current modulation. Specific details on our quality management system covering both quality control and ongoing optimization have been provided. The roles of each CT protocol team member have been defined, and the critical role that IT solutions provides for the management of files and the monitoring of CT protocols has been reviewed. In addition, the invaluable role management provides by being a champion for the project has been explained; lack of a project champion will mitigate the efforts of a CT protocol optimization team. Meeting the guidelines set forth in the AAPM practice guideline was not inherently difficult, but did, in our case, require the cooperation of radiologists, technologists, physicists, IT, administrative staff, and hospital management. Some of the IT solutions presented in this paper are novel and currently unique to our institution.

PACS number: 87.57.Q
An image‐based method to synchronize cone‐beam CT and optical surface tracking
Authors: Fassi Aurora , Schaerer Joël , Riboldi Marco , Sarrut David , Baroni Guido
Published: February 2017

The integration of in‐room X‐ray imaging and optical surface tracking has gained increasing importance in the field of image guided radiotherapy (IGRT). An essential step for this integration consists of temporally synchronizing the acquisition of X‐ray projections and surface data. We present an image‐based method for the synchronization of cone‐beam computed tomography (CBCT) and optical surface systems, which does not require the use of additional hardware. The method is based on optically tracking the motion of a component of the CBCT/gantry unit, which rotates during the acquisition of the CBCT scan. A calibration procedure was implemented to relate the position of the rotating component identified by the optical system with the time elapsed since the beginning of the CBCT scan, thus obtaining the temporal correspondence between the acquisition of X‐ray projections and surface data. The accuracy of the proposed synchronization method was evaluated on a motorized moving phantom, performing eight simultaneous acquisitions with an Elekta Synergy CBCT machine and the AlignRT optical device. The median time difference between the sinusoidal peaks of phantom motion signals extracted from the synchronized CBCT and AlignRT systems ranged between ‐3.1 and 12.9 msec, with a maximum interquartile range of 14.4 msec. The method was also applied to clinical data acquired from seven lung cancer patients, demonstrating the potential of the proposed approach in estimating the individual and daily variations in respiratory parameters and motion correlation of internal and external structures. The presented synchronization method can be particularly useful for tumor tracking applications in extracranial radiation treatments, especially in the field of patient‐specific breathing models, based on the correlation between internal tumor motion and external surface surrogates.

PACS number: 87
MLC positional accuracy evaluation through the Picket Fence test on EBT2 films and a 3D volumetric phantom
Authors: Antypas Christos , Floros Ioannis , Rouchota Maritina , Armpilia Christina , Lyra Maria
Published: February 2017

The accuracy of MLC positions during radiotherapy is important as even small positional deviations can translate into considerable dose delivery errors. This becomes crucial when radiosensitive organs are located near the treated volume and especially during IMRT, where dose gradients are steep. A test commonly conducted to measure the positional accuracy of the MLCs is the Picket Fence test. In this study two alterations of the Picket Fence test were performed and evaluated, the first one using radiochromic EBT2 films and the second one the diode array phantom and its software. Our results showed that EBT2 films provide a relatively fast, qualitative visual inspection of the significant leaf dispositions. When slight inaccuracies need to be revealed or precise numerical results for each leaf position are needed, provides the desired accuracy of 1 mm. In treatment modalities where a higher accuracy is required in the delivered dose distribution, such as in IMRT, precise numerical values of the measurements for the MLC positional inspection are required.

PACS number: 87.55.Qr, 87.56.bd, 87.56.Fc, 87.56.nk
Efficacy and workload analysis of a fixed vertical couch position technique and a fixed‐action–level protocol in whole‐breast radiotherapy
Authors: Petillion Saskia , Verhoeven Karolien , Weltens Caroline , Van den Heuvel Frank
Published: February 2017

Quantification of the setup errors is vital to define appropriate setup margins preventing geographical misses. The no‐action–level (NAL) correction protocol reduces the systematic setup errors and, hence, the setup margins. The manual entry of the setup corrections in the record‐and‐verify software, however, increases the susceptibility of the NAL protocol to human errors. Moreover, the impact of the skin mobility on the anteroposterior patient setup reproducibility in whole‐breast radiotherapy (WBRT) is unknown. In this study, we therefore investigated the potential of fixed vertical couch position‐based patient setup in WBRT. The possibility to introduce a threshold for correction of the systematic setup errors was also explored. We measured the anteroposterior, mediolateral, and superior–inferior setup errors during fractions 1–12 and weekly thereafter with tangential angled single modality paired imaging. These setup data were used to simulate the residual setup errors of the NAL protocol, the fixed vertical couch position protocol, and the fixed‐action–level protocol with different correction thresholds. Population statistics of the setup errors of 20 breast cancer patients and 20 breast cancer patients with additional regional lymph node (LN) irradiation were calculated to determine the setup margins of each off‐line correction protocol. Our data showed the potential of the fixed vertical couch position protocol to restrict the systematic and random anteroposterior residual setup errors to 1.8 mm and 2.2 mm, respectively. Compared to the NAL protocol, a correction threshold of 2.5 mm reduced the frequency of mediolateral and superior–inferior setup corrections with 40% and 63%, respectively. The implementation of the correction threshold did not deteriorate the accuracy of the off‐line setup correction compared to the NAL protocol. The combination of the fixed vertical couch position protocol, for correction of the anteroposterior setup error, and the fixed‐action–level protocol with 2.5 mm correction threshold, for correction of the mediolateral and the superior–inferior setup errors, was proved to provide adequate and comparable patient setup accuracy in WBRT and WBRT with additional LN irradiation.

PACS numbers: 87.53.Kn, 87.57.‐s
Effect of ROI filtering in 3D cone‐beam rotational angiography on organ dose and effective dose in cerebral investigations
Authors: Göpfert Fabian , Schmidt Ralph , Wulff Jörg , Zink Klemens
Published: February 2017

The assessment of intracranial aneurysms is increasingly performed using three‐dimensional cone‐beam rotational angiography (3D CBRA). To reduce the dose to the patient during 3D CBRA procedures, filtered region‐of‐interest imaging (FROI) is presented in literature to be an effective technique as the dose in regions of low interest is reduced, while high image quality is preserved in the ROI. The purpose of this study was to quantify the benefit of FROI imaging during a typical 3D CBRA procedure in a patient's head region. A cone‐beam rotational angiography unit (Infinix) was modeled in GMctdospp, an EGSnrc‐based Monte Carlo software, which calculates patient dose distributions in rotational computed tomography. Kodak Lanex, a gadolinium compound, was chosen to be the ROI filter material. The adult female ICRP reference phantom was integrated in GMctdospp to calculate organ and effective doses in simulations of FROI‐CBRA examinations. During the Monte Carlo simulations, different parameters as the ROI filter thickness, the ROI opening size, the tube voltage, and the isocenter position were varied. The results showed that the reduction in dose clearly depends on these parameters. Comparing the reduction in organ dose in standard 3D CBRA and FROI‐CBRA, a maximum reduction of about 60%–80% could be achieved with a small sized ROI filter and about 40%–70% of the dose could be saved using a ROI filter with a large opening. Further we could show that dose reduction strongly depends on filter thickness, the location of the organ in the radiated area, and the position of the isocenter. As a consequence, dose reduction partially differs from theoretically calculated values by a factor up to 1.6. The effective dose could be reduced to a minimum of about 40%. Due to the fact that standard 3D CBRA is only used for the assessment of aneurysms at present and, thus, most of the patient dose originates from the aneurysm treatment (with 2D techniques) itself, the dose reduction effect of ROI filtering in 3D CBRA tends to be much smaller, if the patient dose of a whole aneurysm treatment procedure is considered.

PACS numbers: 87.59.DJ, 87.55.kh
Planning for mARC treatments with the Eclipse treatment planning system
Authors: Sarkar Vikren , Huang Long , Rassiah‐Szegedi Prema , Zhao Hui , Huang Jessica , Szegedi Martin , Salter Bill J.
Published: February 2017

While modulated arc (mARC) capabilities have been available on Siemens linear accelerators for almost two years now, there was, until recently, only one treatment planning system capable of planning these treatments. The Eclipse treatment planning system now offers a module that can plan for mARC treatments. The purpose of this work was to test the module to determine whether it is capable of creating clinically acceptable plans. A total of 23 plans were created for various clinical sites and all plans delivered without anomaly. The average 3%/3 mm gamma pass rate for the plans was 98.0%, with a standard deviation of 1.7%. For a total of 14 plans, an equivalent static gantry IMRT plan was also created to compare delivery time. In all but two cases, the mARC plans delivered significantly faster than the static gantry plan. We have confirmed the successful creation of mARC plans that are deliverable with high fidelity on an ARTISTE linear accelerator, thus demonstrating the successful implementation of the Eclipse mARC module.

PACS numbers: 87.55.D‐, 87.55.ne, 87.57.uq,
Site‐specific tolerance tables and indexing device to improve patient setup reproducibility
Authors: McCullough Kiernan T. , James Joshua A. , Cetnar Ashley J. , McCullough Mark A. , Wang Brian
Published: February 2017

While the implementation of tools such as image‐guidance and immobilization devices have helped to prevent geometric misses in radiation therapy, many treatments remain prone to error if these items are not available, not utilized for every fraction, or are misused. The purpose of this project is to design a set of site‐specific treatment tolerance tables to be applied to the treatment couch for use in a record and verify (R&V) system that will insure accurate patient setup with minimal workflow interruption. This project also called for the construction of a simple indexing device to help insure reproducible patient setup for patients that could not be indexed with existing equipment. The tolerance tables were created by retrospective analysis on a total of 66 patients and 1,308 treatments, separating them into five categories based on disease site: lung, head and neck (H&N), breast, pelvis, and abdomen. Couch parameter tolerance tables were designed to encompass 95% of treatments, and were generated by calculating the standard deviation of couch vertical, longitudinal, and lateral values using the first day of treatment as a baseline. We also investigated an alternative method for generating the couch tolerances by updating the baseline values when patient position was verified with image guidance. This was done in order to adapt the tolerances to any gradual changes in patient setup that would not correspond with a mistreatment. The tolerance tables and customizable indexing device were then implemented for a trial period in order to determine the feasibility of the system. During this trial period we collected data from 1,054 fractions from 65 patients. We then analyzed the number of treatments that would have been out of tolerance, as well as whether or not the tolerances or setup techniques should be adjusted. When the couch baseline values were updated with every imaging fraction, the average rate of tolerance violations was 10% for the lung, H&N, abdomen, and pelvis treatments. Using the indexing device, tolerances for patients with pelvic disease decreased (e.g., from 5.3 cm to 4.3 cm longitudinally). Unfortunately, the results from breast patients were highly variable due to the complexity of the setup technique, making the couch an inadequate surrogate for measuring setup accuracy. In summary, we have developed a method to turn the treatment couch parameters within the R&V system into a useful alert tool, which can be implemented at other institutions, in order to identify potential errors in patient setup.

PACS numbers: 87.53Kn, 87.55.kh, 87.55.ne, 87.55.km, 87.55K‐, 87.55.Qr
Dosimetric characterization of the high‐dose‐rate brachytherapy source using the AAPM and ESTRO formalism
Authors: Thanh Minh‐Tri Ho , Munro John J. , Medich David C.
Published: February 2017

The Source Production & Equipment Co. (SPEC) model is a new brachytherapy source model intended for use as a temporary high‐dose‐rate (HDR) brachytherapy source for the Nucletron microSelectron Classic afterloading system. The purpose of this study is to characterize this HDR source for clinical application by obtaining a complete set of Monte Carlo calculated dosimetric parameters for the M‐15, as recommended by AAPM and ESTRO, for isotopes with average energies greater than 50 keV. This was accomplished by using the MCNP6 Monte Carlo code to simulate the resulting source dosimetry at various points within a pseudoinfinite water phantom. These dosimetric values next were converted into the AAPM and ESTRO dosimetry parameters and the respective statistical uncertainty in each parameter also calculated and presented. The source was modeled in an MCNP6 Monte Carlo environment using the physical source specifications provided by the manufacturer. photons were uniformly generated inside the iridium core of the model with photon and secondary electron transport replicated using photoatomic cross‐sectional tables supplied with MCNP6. Simulations were performed for both water and air/vacuum computer models with a total of sources photon history for each simulation and the in‐air photon spectrum filtered to remove low‐energy photons below . Dosimetric data, including , and , and their statistical uncertainty were calculated from the output of an MCNP model consisting of an source placed at the center of a spherical water phantom of 100 cm diameter. The air kerma strength in free space, , and dose rate constant, Λ, also was computed from a MCNP model with source, was centered at the origin of an evacuated phantom in which a critical volume containing air at STP was added 100 cm from the source center. The reference dose rate, , is found to be . The air kerma strength, , is reported to be , and the dose rate constant, Λ, is calculated to be . The normalized dose rate, radial dose function, and anisotropy function with their uncertainties were computed and are represented in both tabular and graphical format in the report. A dosimetric study was performed of the new HDR brachytherapy source using the MCNP6 radiation transport code. Dosimetric parameters, including the dose‐rate constant, radial dose function, and anisotropy function, were calculated in accordance with the updated AAPM and ESTRO dosimetric parameters for brachytherapy sources of average energy greater than 50 keV. These data therefore may be applied toward the development of a treatment planning program and for clinical use of the source.

PACS numbers: 87.56.bg, 87.53.Jw
Development of a novel remote‐controlled and self‐contained audiovisual‐aided interactive system for immobilizing claustrophobic patients
Authors: Ju Harang , Kim Siyong , Read Paul , Trifiletti Daniel , Harrell Andrew , Libby Bruce , Kim Taeho
Published: February 2017

In radiotherapy, only a few immobilization systems, such as open‐face mask and head mold with a bite plate, are available for claustrophobic patients with a certain degree of discomfort. The purpose of this study was to develop a remote‐controlled and self‐contained audiovisual (AV)‐aided interactive system with the iPad mini with Retina display for intrafractional motion management in brain/H&N (head and neck) radiotherapy for claustrophobic patients. The self‐contained, AV‐aided interactive system utilized two tablet computers: one for AV‐aided interactive guidance for the subject and the other for remote control by an operator. The tablet for audiovisual guidance traced the motion of a colored marker using the built‐in front‐facing camera, and the remote control tablet at the control room used infrastructure Wi‐Fi networks for real‐time communication with the other tablet. In the evaluation, a programmed QUASAR motion phantom was used to test the temporal and positional accuracy and resolution. Position data were also obtained from ten healthy volunteers with and without guidance to evaluate the reduction of intrafractional head motion in simulations of a claustrophobic brain or H&N case. In the phantom study, the temporal and positional resolution was 24 Hz and 0.2 mm. In the volunteer study, the average superior–inferior and right–left displacement was reduced from 1.9 mm to 0.3 mm and from 2.2 mm to 0.2 mm with AV‐aided interactive guidance, respectively. The superior–inferior and right–left positional drift was reduced from 0.5 mm/min to 0.1 mm/min and from 0.4 mm/min to 0.04 mm/min with audiovisual‐aided interactive guidance. This study demonstrated a reduction in intrafractional head motion using a remote‐controlled and self‐contained AV‐aided interactive system of iPad minis with Retina display, easily obtainable and cost‐effective tablet computers. This approach can potentially streamline clinical flow for claustrophobic patients without a head mask and also allows patients to practice self‐motion management before radiation treatment delivery.

PACS number: 87.55.Gh
Effect of radiation dose reduction on image quality in adult head CT with noise‐suppressing reconstruction system with a 256 slice MDCT
Authors: Baskan Ozdil , Erol Cengiz , Ozbek Hanefi , Paksoy Yahya
Published: February 2017

The purpose of our study was to investigate the effect of iterative reconstruction (IR) as a dose reduction system on the image quality (IQ) of the adult head computed tomography (CT) at various low‐dose levels, and to identify ways of setting the amount of dose reduction. We performed two noncontrast low‐dose (LD) adult head CT protocols modified by lowering the tube current with IR which were decided in the light of a group of phantom studies. Two groups of patients, each 100 underwent noncontrast head CT with LD‐I and LD‐II, respectively. These groups were compared with 100 consecutive standard dose (STD) adult head CT protocol in terms of quantitative and qualitative IQ. The signal‐to‐noise ratio (SNR) of the white matter (WM) and gray matter (GM) and contrast‐to‐noise ratio (CNR) values in the LD groups were higher than the STD group. The differences were statistically significant. When the STD and the LD groups were compared qualitatively, no significant differences were found in overall quality. By selecting the appropriate level of IR 34%, radiation dose reduction in adult head CT can be achieved without compromising IQ.

PACS number: 87.57.‐s
VMAT linear accelerator commissioning and quality assurance: dose control and gantry speed tests
Authors: Barnes Michael P. , Rowshanfarzad Pejman , Greer Peter B.
Published: February 2017

In VMAT treatment delivery the ability of the linear accelerator (linac) to accurately control dose versus gantry angle is critical to delivering the plan correctly. A new VMAT test delivery was developed to specifically test the dose versus gantry angle with the full range of allowed gantry speeds and dose rates. The gantry‐mounted IBA MatriXX with attached inclinometer was used in movie mode to measure the instantaneous relative dose versus gantry angle during the plan every 0.54 s. The results were compared to the expected relative dose at each gantry angle calculated from the plan. The same dataset was also used to compare the instantaneous gantry speeds throughout the delivery compared to the expected gantry speeds from the plan. Measurements performed across four linacs generally show agreement between measurement and plan to within 1.5% in the constant dose rate regions and dose rate modulation within 0.1 s of the plan. Instantaneous gantry speed was measured to be within of the plan (1 SD). An error in one linac was detected in that the nominal gantry speed was incorrectly calibrated. This test provides a practical method to quality‐assure critical aspects of VMAT delivery including dose versus gantry angle and gantry speed control. The method can be performed with any detector that can acquire time‐resolved dosimetric information that can be synchronized with a measurement of gantry angle. The test fulfils several of the aims of the recent Netherlands Commission on Radiation Dosimetry (NCS) Report 24, which provides recommendations for comprehensive VMAT quality assurance.

PACS number(s): 87.55.Qr
Effect of contrast‐enhanced CT scans on heterogeneity corrected dose computations in the lung
Authors: Burridge Nichola A. , Rowbottom Carl G. , Burt Paul A.
Published: February 2017

The aim of this study was to investigate and, if possible, compensate for the effect of intravenous contrast‐enhanced CT scans on the treatment planning dose distributions for lung patients. The contrast and noncontrast CT scans of 3 patients were registered, and the effect of contrast on the Hounsfield units (HU) was assessed. The effect of contrast was then simulated in the CT scans of 18 patients receiving radiotherapy of the lung by modification of the CT numbers for relevant sections of noncontrast‐enhanced CT scans. All treatment planning was performed on the Pinnacle3 planning system. The dose distributions computed from simulated contrast CT scans were compared to the original dose distributions by comparison of the monitor units (MUs) for each beam in the treatment plan required to deliver the prescribed dose to the isocenter as well as a comparison of the total MUs for each patient, a percentage change in required MUs being equivalent to a percentage change in the dose. A correction strategy to enable the use of contrast‐enhanced CT scans in treatment planning was developed, and the feasibility of applying the strategy was investigated by calculating dose distributions for both the original and simulated contrast CT scans. A mean increase in the overall patient MUs of was found, with a maximum increase of 3.3% when contrast was simulated on the original CT scans. The simulated contrast scans confirmed that the use of contrast‐enhanced CT scans for routine treatment planning would result in a systematic change in the dose delivered to the isocenter. The devised correction strategy had no clinically relevant effect on the dose distribution for the original CT scans. The application of the correction strategy to the simulated contrast CT scans led to a reduction of the mean difference in the overall MUs to compared to the original scan, demonstrating that the effect of contrast was eliminated with the correction strategy. This work has highlighted the problems associated with using contrast‐enhanced CT scans in heterogeneity corrected dose computation. Contrast visible in the CT scan is transient and should not be accounted for in the treatment plan. A correction strategy has been developed that minimizes the effect of intravenous contrast while having no clinical effect on noncontrast CT scans. The correction strategy allows the use of contrast without detriment to the treatment plan.

PACS number: 87.53.Tf
Book Review
Authors: Gray Joel E.
Published: February 2017

Physics for Radiation Protection: A Handbook, James E. Martin, PhD, CHP, Editor, John Wiley Publishers, ISBN 3527406115, $250 Hc
Book Review
Authors: Cho Paul S.
Published: February 2017

Advances in Medical Physics 2006, Edited by Anthony B. Wolbarst, Robert G. Zamenhof, and William R. Hendee, Medical Physics Publishing, Madison, Wisconsin 2006, 331 pp ISBN: 978‐1‐30524‐34‐,7 List price: $80
Simplifying intensity‐modulated radiotherapy plans with fewer beam angles for the treatment of oropharyngeal carcinoma
Authors: Takamiya Robert , Missett Brian , Weinberg Vivian , Akazawa Clayton , Akazawa Pam , Zytkovicz Andrea , Bucci Mary Kara , Lee Nancy , Quivey Jeanne , Xia Ping
Published: February 2017

The first aim of the present study was to investigate the feasibility of using fewer beam angles to improve delivery efficiency for the treatment of oropharyngeal cancer (OPC) with inverse‐planned intensity‐modulated radiation therapy (IP‐IMRT). A secondary aim was to evaluate whether the simplified IP‐IMRT plans could reduce the indirect radiation dose. The treatment plans for 5 consecutive OPC patients previously treated with a forward‐planned IMRT (FP‐IMRT) technique were selected as benchmarks for this study. The initial treatment goal for these patients was to deliver 70 Gy to of the planning gross tumor volume (PTV‐70) and 59.4 Gy to of the planning clinical tumor volume (PTV‐59.4) simultaneously. Each case was re‐planned using IP‐IMRT with multiple beam‐angle arrangements, including four complex IP‐IMRT plans using 7 or more beam angles, and one simple IMRT plan using 5 beam angles. The complex IP‐IMRT plans and simple IP‐IMRT plans were compared to each other and to the FP‐IMRT plans by analyzing the dose coverage of the target volumes, the plan homogeneity, the dose–volume histograms of critical structures, and the treatment delivery parameters including delivery time and the total number of monitor units (MUs). When comparing the plans, we found no significant difference between the complex IP‐IMRT, simple IP‐IMRT, and FP‐IMRT plans for tumor target coverage (PTV‐70: ; PTV‐59.4: ). The plan homogeneity, measured by the mean percentage isodose, did not significantly differ between the IP‐IMRT and FP‐IMRT plans , although we observed a trend toward greater inhomogeneity of dose in the simple IP‐IMRT plans. All IP‐IMRT plans either met or exceeded the quality of the FP‐IMRT plans in terms of dose to adjacent critical structures, including the parotids, spinal cord, and brainstem. As compared with the complex IP‐IMRT plans, the simple IP‐IMRT plans significantly reduced the mean treatment time (maximum probability for four pairwise comparisons: ). In conclusion, our study demonstrates that, as compared with complex IP‐IMRT, simple IP‐IMRT can significantly improve treatment delivery efficiency while maintaining similar target coverage and sparing of critical structures. However, the improved efficiency does not significantly reduce the total number of MUs nor the indirect radiation dose.

PACS number: 87.53.tf
GafChromic XR‐QA film in testing panoramic dental radiography
Authors: Chu Robert Y.L. , Lam Tin , Liang Yongguang
Published: February 2017

The location and field size of the incident X‐ray beam in panoramic dental radiography cannot be ascertained visually most of the time. However, these parameters are needed for quality control and dosimetry determination. To alleviate this problem, we tested GafChromic XR‐QA film on two panoramic systems. For each system, we used the length of a cross‐sectional image of the incident beam and the exposure measurement with a pencil ion chamber to compute the dose–area product. The result was confirmed by direct analysis of a dose distribution on a film. Placement of the ion chamber was determined by the latter images. The GafChromic XR‐QA version of radiochromic film has thus been demonstrated to usefully complement a pencil ion chamber in the testing of a panoramic radiography system.

PACS numbers: 87.52.Df, 87.59Bh, 87.66.Cd, 87.66Jj
An interaural-correlation-based approach that accounts for a wide variety of binaural detection data
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: February 2017

Interaural cross-correlation-based models of binaural processing have accounted successfully for a wide variety of binaural phenomena, including binaural detection, binaural discrimination, and measures of extents of laterality based on interaural temporal disparities, interaural intensitive disparities, and their combination. This report focuses on quantitative accounts of data obtained from binaural detection experiments published over five decades. Particular emphasis is placed on stimulus contexts for which commonly used correlation-based approaches fail to provide adequate explanations of the data. One such context concerns binaural detection of signals masked by certain noises that are narrow-band and/or interaurally partially correlated. It is shown that a cross-correlation-based model that includes stages of peripheral auditory processing can, when coupled with an appropriate decision variable, account well for a wide variety of classic and recently published binaural detection data including those that have, heretofore, proven to be problematic.
Uncommon mutation in mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS)
Authors: David Jasna , Okiro Julie Omolola , Murphy Kevin , Elamin Marwa
Published: February 2017

A 26-year-old man presented to the emergency department with new-onset generalised tonic–clonic seizures. His clinical picture suggested either autoimmune or infectious encephalitis while his brain imaging raised the possibility of a stroke. A detailed developmental and childhood medical history added suspicion of a mitochondrial defect to the differential. After several molecular genetic analyses, an uncommon mitochondrial mutation was confirmed, unequivocally consistent with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome.
A Flexible Fault Injection Platform for the Analysis of the Symptoms of Soft Errors in FPGA Soft Processors
Authors: Sari Aitzan , Psarakis Mihalis
Published: February 2017

Due to the high vulnerability of SRAM-based FPGAs in single-event upsets (SEUs), effective fault tolerant soft processor architectures must be considered when we use FPGAs to build embedded systems for critical applications. In the past, the detection of symptoms of soft errors in the behavior of microprocessors has been used for the implementation of low-budget error detection techniques, instead of costly hardware redundancy techniques. To enable the development of such low-cost error detection techniques for FPGA soft processors, we propose an in-depth analysis of the symptoms of SEUs in the FPGA configuration memory. To this end, we present a flexible fault injection platform based on an open-source CAD framework (RapidSmith) for the soft error sensitivity analysis of soft processors in Xilinx SRAM-based FPGAs. Our platform supports the estimation of soft error sensitivity per configuration bit/frame, processor component and benchmark. The fault injection is performed on-chip by a dedicated microcontroller which also monitors processor behavior to identify specific symptoms as consequences of soft errors. The performed analysis showed that these symptoms can be used to build an efficient, low-cost error detection scheme. The proposed platform is demonstrated through an extensive fault injection campaign in the Leon3 soft processor.
Joint DOA and Frequency Estimation for Linear Array with Compressed Sensing PARAFAC Framework
Authors: Li Shu , Sun Zezhou , Zhang Xiaofei , Chen Weiyang , Xu Dazhuan
Published: February 2017

In this paper, a joint direction of arrival (DOA) and frequency estimation algorithm of narrow-band signals is proposed via compressed sensing (CS) parallel factor (PARAFAC) framework. The proposed algorithm constructs the data model into a PARAFAC model, and compresses it to a smaller one. Then trilinear alternating least-squares (TALS) algorithm is exploited to estimate the compressed parameter matrices, and finally the joint DOA and frequency estimation is obtained via the spatial sparsity and the frequency sparsity. Due to compression, the proposed algorithm has lower computational complexity than the conventional PARAFAC algorithm, and saves more memory capacity for practical application. The DOA and frequency estimation performance of the proposed algorithm is very close to that of the conventional PARAFAC algorithm, and better than those of the estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm and the propagator method (PM). Furthermore, the proposed algorithm can achieve automatically paired DOA and frequency estimation. Besides, it is applicable for nonuniform linear arrays. Effectiveness of the proposed algorithm is assessed by simulations.
Testable Novel Parity-Preserving Reversible Gate and Low-Cost Quantum Decoder Design in 1D Molecular-QCA
Authors: Misra Neeraj Kumar , Sen Bibhash , Wairya Subodh , Bhoi Bandan
Published: February 2017

In this era of emerging technology, reversible logic is applied for circuit design. Due to the deep submicron and scaling, a number of pitfalls are faced by the CMOS technology. So a lot of constraints related to CMOS are stated with the QCA technology. The aim of this paper is the efficient conservative reversible decoder circuit design with optimal reversible metrics. It aims at furnishing a proposed DC gate (DC stands for decoder comparator) to help the construction of these mentioned circuits. Finally, the DC is employed to construct the [Formula: see text]-bit reversible decoder. Moreover, a new concept of the quantum equivalent of combined reversible gates is presented by the algorithm. By the comparative outcomes, it is found that the proposed decoder had achieved 25% quantum cost, 66% gate count, and 50% garbage outputs as compared to the counterpart. Further, stuck-at-fault for the single- and multiple-bit input and output is applied to the DC gate for testability. Moreover, the DC gate in the physical foreground on QCADesigner achieved 0.63 μm2 area, 15 majority voter gates, and 451 cell complexities. It is observed that nanoelectronics has also made an inevitable contribution in the area of QCA.
A Switchable Chaotic Oscillator with Two Amplitude–Frequency Controllers
Authors: Hu Wen , Akgul Akif , Li Chunbiao , Zheng Taicheng , Li Peng
Published: February 2017

A simple chaotic system with a single nonquadratic term is developed to be a switchable chaotic signal generator in this paper. Additional nonlinearity of the absolute value function is introduced for reforming the structure without damaging the basic dynamics but yielding a new independent amplitude–frequency controller. A switchable chaotic experimental oscillator is designed afterwards, where two coefficients corresponding to two independent rheostats rescale the amplitude and frequency of the chaotic signals smoothly. To our knowledge, this has never been found in other chaotic oscillators.
Analyzing Knowledge Construction in Online Health Group Discussion
Authors: Ghazali Achmad , Tretiakov Alexei , Pringgabayu Dematria , Ramdlany Dany Muhammad Athory
Published: February 2017

The ongoing transition to the patient-centred healthcare paradigm suggests that patients adopt an active role in managing their health conditions. As a result, the Internet is becoming an important source of health-related information. Internet-based health support groups allow patients to access diverse information relevant to their particular situation by participating in online discussions. The quality of such information may have effects on the patients’ health outcomes. The purpose of the present study was to investigate the effects of knowledge construction in health support group online discussions on perceived information quality, information quality from the perspective of information consumers, and on information integrity, that is, validity from the point of view of the current state of scientific knowledge. It was hypothesised that knowledge construction results in better perceived information quality and in higher information integrity. A health support group online discussion site devoted to weight management was used as a source of data. Quantitative content analysis was used with a discussion thread as a unit of analysis. Based on the findings, the study suggested that moderators of health support group online discussions should promote explicitation or lower level knowledge construction by encouraging clarifications and refinements of health-related recommendations. Moreover, participation of qualified health practitioners is desirable to promote health-related behaviours based on evidence-based knowledge and to expose recommendations that have uncertain or even dangerous effects.
Optimal Scheduling of Cybersecurity Analysts for Minimizing Risk
Authors: Ganesan Rajesh , Jajodia Sushil , Cam Hasan
Published: February 2017

Cybersecurity threats are on the rise with evermore digitization of the information that many day-to-day systems depend upon. The demand for cybersecurity analysts outpaces supply, which calls for optimal management of the analyst resource. Therefore, a key component of the cybersecurity defense system is the optimal scheduling of its analysts. Sensor data is analyzed by automatic processing systems, and alerts are generated. A portion of these alerts is considered to be
significant
, which requires thorough examination by a cybersecurity analyst. Risk, in this article, is defined as the percentage of unanalyzed or not thoroughly analyzed alerts among the
significant
alerts by analysts. The article presents a generalized optimization model for scheduling cybersecurity analysts to minimize risk (a.k.a., maximize
significant
alert coverage by analysts) and maintain risk under a pre-determined upper bound. The article tests the optimization model and its scalability on a set of given sensors with varying analyst experiences, alert generation rates, system constraints, and system requirements. Results indicate that the optimization model is scalable and is capable of identifying both the right mix of analyst expertise in an organization and the sensor-to-analyst allocation in order to maintain risk below a given upper bound. Several meta-principles are presented, which are derived from the optimization model, and they further serve as guiding principles for hiring and scheduling cybersecurity analysts. The simulation studies (validation) of the optimization model outputs indicate that risk varies non-linearly with an analyst/sensor ratio, and for a given analyst/sensor ratio, the risk is independent of the number of sensors in the system.
Research for practice
Authors: Bailis Peter , Zhang Irene , Adib Fadel
Published: February 2017

Expert-curated guides to the best of CS research.
Privacy-Enhanced Television Audience Measurements
Authors: Drosatos George , Tasidou Aimilia , Efraimidis Pavlos S.
Published: February 2017

Internet-enabled television systems (SmartTVs) are a development that introduces these devices into the interconnected environment of the Internet of Things. We propose a privacy-preserving application for computing Television Audience Measurement (TAM) ratings. SmartTVs communicate over the Internet to calculate aggregate measurements. Contemporary cryptographic building blocks are utilized to ensure the privacy of the participating individuals and the validity of the computed TAM ratings. Additionally, user compensation capabilities are introduced to bring some of the company profits back to the data owners. A prototype implementation is developed on an Android-based SmartTV platform and experimental results illustrate the feasibility of the approach.
Automatic Construction of Statechart-Based Anomaly Detection Models for Multi-Threaded Industrial Control Systems
Authors: Kleinmann Amit , Wool Avishai
Published: February 2017

Traffic of Industrial Control System (ICS) between the Human Machine Interface (HMI) and the Programmable Logic Controller (PLC) is known to be highly periodic. However, it is sometimes multiplexed, due to asynchronous scheduling. Modeling the network traffic patterns of multiplexed ICS streams using Deterministic Finite Automata (DFA) for anomaly detection typically produces a very large DFA and a high false-alarm rate. In this article, we introduce a new modeling approach that addresses this gap. Our
Statechart DFA
modeling includes multiple DFAs, one per cyclic pattern, together with a DFA-selector that de-multiplexes the incoming traffic into sub-channels and sends them to their respective DFAs. We demonstrate how to automatically construct the statechart from a captured traffic stream. Our unsupervised learning algorithms first build a Discrete-Time Markov Chain (DTMC) from the stream. Next, we split the symbols into sets, one per multiplexed cycle, based on symbol frequencies and node degrees in the DTMC graph. Then, we create a sub-graph for each cycle and extract Euler cycles for each sub-graph. The final statechart is comprised of one DFA per Euler cycle. The algorithms allow for non-unique symbols, which appear in more than one cycle, and also for symbols that appear more than once in a cycle.

We evaluated our solution on traces from a production ICS using the Siemens S7-0x72 protocol. We also stress-tested our algorithms on a collection of synthetically-generated traces that simulated multiplexed ICS traces with varying levels of symbol uniqueness and time overlap. The algorithms were able to split the symbols into sets with 99.6% accuracy. The resulting statechart modeled the traces with a median false-alarm rate of as low as 0.483%. In all but the most extreme scenarios, the
Statechart
model drastically reduced both the false-alarm rate and the learned model size in comparison with the naive single-DFA model.
Tracking Illicit Drug Dealing and Abuse on Instagram Using Multimodal Analysis
Authors: Yang Xitong , Luo Jiebo
Published: February 2017

Illicit drug trade via social media sites, especially photo-oriented Instagram, has become a severe problem in recent years. As a result, tracking drug dealing and abuse on Instagram is of interest to law enforcement agencies and public health agencies. However, traditional approaches are based on manual search and browsing by trained domain experts, which suffers from the problem of poor scalability and reproducibility. In this article, we propose a novel approach to detecting drug abuse and dealing automatically by utilizing multimodal data on social media. This approach also enables us to identify drug-related posts and analyze the behavior patterns of drug-related user accounts. To better utilize multimodal data on social media, multimodal analysis methods including multi-task learning and decision-level fusion are employed in our framework. We collect three datasets using Instagram and web search engine for training and testing our models. Experiment results on expertly labeled data have demonstrated the effectiveness of our approach, as well as its scalability and reproducibility over labor-intensive conventional approaches.
CDF-LDPC
Authors: Qi Shigui , Feng Dan , Su Nan , Mei Linjun , Liu Jingning
Published: February 2017

The raw error rate of a Solid-State drive (SSD) increases gradually with the increase of Program/Erase (P/E) cycles, retention time, and read cycles. Traditional approaches often use Error Correction Code (ECC) to ensure the reliability of SSDs. For error-free flash memory pages, time costs spent on ECC are redundant and make read performance suboptimal. This article presents a CRC-Detect-First LDPC (CDF-LDPC) algorithm to optimize the read performance of SSDs. The basic idea is to bypass Low-Density Parity-Check (LDPC) decoding of error-free flash memory pages, which can be found using a Cyclic Redundancy Check (CRC) code. Thus, error-free pages can be read directly without sacrificing the reliability of SSDs. Experiment results show that the read performance is improved more than 50% compared with traditional approaches. In particular, when idle time of benchmarks and SSD parallelism are exploited, CDF-LDPC can be performed more efficiently. In this case, the read performance of SSDs can be improved up to about 80% compared to that of the state-of-art.