bluuebunny/crossref_metadata_2025 huggingface dataset:
Flattening filter‐free accelerators: a report from the AAPM Therapy Emerging Technology Assessment Work Group
Authors: Xiao Ying , Kry Stephen F. , Popple Richard , Yorke Ellen , Papanikolaou Niko , Stathakis Sotirios , Xia Ping , Huq Saiful , Bayouth John , Galvin James , Yin Fang‐Fang
Published: February 2017

This report describes the current state of flattening filter‐free (FFF) radiotherapy beams implemented on conventional linear accelerators, and is aimed primarily at practicing medical physicists. The Therapy Emerging Technology Assessment Work Group of the American Association of Physicists in Medicine (AAPM) formed a writing group to assess FFF technology. The published literature on FFF technology was reviewed, along with technical specifications provided by vendors. Based on this information, supplemented by the clinical experience of the group members, consensus guidelines and recommendations for implementation of FFF technology were developed. Areas in need of further investigation were identified. Removing the flattening filter increases beam intensity, especially near the central axis. Increased intensity reduces treatment time, especially for high‐dose stereotactic radiotherapy/radiosurgery (SRT/SRS). Furthermore, removing the flattening filter reduces out‐of‐field dose and improves beam modeling accuracy. FFF beams are advantageous for small field (e.g., SRS) treatments and are appropriate for intensity‐modulated radiotherapy (IMRT). For conventional 3D radiotherapy of large targets, FFF beams may be disadvantageous compared to flattened beams because of the heterogeneity of FFF beam across the target (unless modulation is employed). For any application, the nonflat beam characteristics and substantially higher dose rates require consideration during the commissioning and quality assurance processes relative to flattened beams, and the appropriate clinical use of the technology needs to be identified. Consideration also needs to be given to these unique characteristics when undertaking facility planning. Several areas still warrant further research and development. Recommendations pertinent to FFF technology, including acceptance testing, commissioning, quality assurance, radiation safety, and facility planning, are presented. Examples of clinical applications are provided. Several of the areas in which future research and development are needed are also indicated.

PACS number: 87.53.‐j, 87.53.Bn, 87.53.Ly, 87.55.‐x, 87.55.N‐, 87.56.bc
A special report of current state of the medical physicist workforce — results of the 2012 ASTRO Comprehensive Workforce Study
Authors: Chen Erli , Arnone Anna , Sillanpaa Jussi K , Yu Yan , Mills Michael D.
Published: February 2017

The medical physics profession is undergoing significant changes. Starting in 2014, candidates registering for certification exams by the American Board of Radiology must have completed a CAMPEP‐accredited residency. This requirement, along with tightened state regulations, uncertainty in future reimbursement, and a stronger emphasis on board certification, have raised questions concerning the state of the medical physics workforce and its ability to adapt to changing requirements. In 2012, ASTRO conducted a workforce study of the comprehensive field of radiation oncology. This article reviews the findings of the medical physics section of the study, including age and gender distribution, educational background, workload, and primary work setting. We also report on job satisfaction, the perceived supply and demand of medical physicists, and the medical physicists' main concerns pertaining to patient safety and quality assurance.

PACS number: 87.90
AAPM Medical Physics Practice Guideline 3.a: Levels of supervision for medical physicists in clinical training
Authors: Seibert J. Anthony , Clements Jessica B. , Halvorsen Per H. , Herman Michael G. , Martin Melissa C. , Palta Jatinder , Pfeiffer Douglas E. , Pizzutiello Robert J. , Schueler Beth A. , Shepard S. Jeff , Fairobent Lynne A.
Published: February 2017

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States.

The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner.

Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized.

The following terms are used in the AAPM practice guidelines:

Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline.

Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.
Evaluation of the scatter doses in the direction of the buccal mucosa from dental metals
Authors: Shimamoto Hiroaki , Sumida Iori , Kakimoto Naoya , Marutani Keisuke , Okahata Ryoko , Usami Ai , Tsujimoto Tomomi , Murakami Shumei , Furukawa Souhei , Tetradis Sotirios
Published: February 2017

The presence of dental metals creates radiation dose perturbation due to scattered radiation during radiation therapy for the head and neck region. The purpose of our study was to compare the scatter doses resulting from various dental metals in the direction of the buccal mucosa among a single‐field technique, three‐dimensional conformal radiation therapy (3D CRT), and intensity‐modulated radiation therapy (IMRT) during radiation therapy for the head and neck region. We used nine metal cubes with 10 mm sides, which were placed inside a water phantom. The scatter doses from the cubes in the direction of the buccal mucosa were measured using radiochromic films. The films were placed perpendicularly to the surface of the cubes. The phantom was irradiated with a 4 MV photon energy by a linear accelerator for all techniques. In the single‐field technique, the scatter doses from dental metals showed 3.7%–19.3% dose increases, and gold showed the largest dose increase. In 3D CRT, the scatter doses from dental metals showed 1.4%–6.9% dose increases, which were within the measurement uncertainty (except for gold). In IMRT, the scatter doses from dental metals showed only 1.4%–4.3% dose increases, which were all within the measurement uncertainty. During radiation therapy for the head and neck region, the scatter doses from the tested dental metals in the direction of the buccal mucosa in 3D CRT or IMRT were lower than those using the single‐field technique. However, there were no differences between the scatter doses resulting from particular dental metals in the direction of the buccal mucosa in 3D CRT and those in IMRT, except for gold.

PACS number: 87
Comparison of pediatric radiation dose and vessel visibility on angiographic systems using piglets as a surrogate: antiscatter grid removal vs. lower detector air kerma settings with a grid — a preclinical investigation
Authors: Strauss Keith J. , Racadio John M. , Abruzzo Todd A. , Johnson Neil D. , Patel Manish N. , Kukreja Kamlesh U. , den Hartog Mark. J. H. , Hoornaert Bart P.A. , Nachabe Rami A.
Published: February 2017

The purpose of this study was to reduce pediatric doses while maintaining or improving image quality scores without removing the grid from X‐ray beam. This study was approved by the Institutional Animal Care and Use Committee. Three piglets (5, 14, and 20 kg) were imaged using six different selectable detector air kerma () per frame values (100%, 70%, 50%, 35%, 25%, 17.5%) with and without the grid. Number of distal branches visualized with diagnostic confidence relative to the injected vessel defined image quality score. Five pediatric interventional radiologists evaluated all images. Image quality score and pigletwere statistically compared using analysis of variance and receiver operating curve analysis to define the preferred dose setting and use of grid for a visibility of 2nd and 3rd order vessel branches. Grid removal reduced both dose to subject and imaging quality by 26%. Third order branches could only be visualized with the grid present; 100% detectorwas required for smallest pig, while 70% detectorwas adequate for the two larger pigs. Second order branches could be visualized with grid at 17.5% detectorfor all three pig sizes. Without the grid, 50%, 35%, and 35% detectorwere required for smallest to largest pig, respectively. Grid removal reduces both dose and image quality score. Image quality scores can be maintained with less dose to subject with the grid in the beam as opposed to removed. Smaller anatomy requires more dose to the detector to achieve the same image quality score.

PACS numbers: 87.53.Bn, 87.57.N‐, 87.57.cj, 87.59.cf, 87.59.Dj
Combination effects of tissue heterogeneity and geometric targeting error in stereotactic body radiotherapy for lung cancer using CyberKnife
Authors: Kang Ki Mun , Jeong Bae Kwon , Choi Hoon‐Sik , Yoo Seung Hoon , Hwang Ui‐Jung , Lim Young Kyung , Jeong Hojin
Published: February 2017

We have investigated the combined effect of tissue heterogeneity and its variation associated with geometric error in stereotactic body radiotherapy (SBRT) for lung cancer. The treatment plans for eight lung cancer patients were calculated using effective path length (EPL) correction and Monte Carlo (MC) algorithms, with both having the same beam configuration for each patient. These two kinds of plans for individual patients were then subsequently recalculated with adding systematic and random geometric errors. In the ordinary treatment plans calculated with no geometric offset, the EPL calculations, compared with the MC calculations, largely overestimated the doses to PTV by , whereas the overestimation were markedly lower in GTV by due to relatively higher density of GTV than of PTV. When recalculating the plans for individual patients with assigning the systematic and random geometric errors, no significant changes in the relative dose distribution, except for overall shift, were observed in the EPL calculations, whereas largely altered in the MC calculations with a consistent increase in dose to GTV. Considering the better accuracy of MC than EPL algorithms, the present results demonstrated the strong coupling of tissue heterogeneity and geometric error, thereby emphasizing the essential need for simultaneous correction for tissue heterogeneity and geometric targeting error in SBRT of lung cancer.

PACS numbers: 87.55.D, 87.55.kh, 87.53.Ly, 87.55.‐x
Camera‐based independent couch height verification in radiation oncology
Authors: Kusters Martijn , Louwe Rob , Kastel Liesbeth Biemans‐van , Nieuwenkamp Henk , Zahradnik Rien , Claessen Roy , van Seters Ronald , Huizenga Henk
Published: February 2017

For specific radiation therapy (RT) treatments, it is advantageous to use the isocenter‐to‐couch distance (ICD) for initial patient setup.(1) Since sagging of the treatment couch is not properly taken into account by the electronic readout of the treatment machine, this readout cannot be used for initial patient positioning using the isocenter‐to‐couch distance (ICD). Therefore, initial patient positioning to the prescribed ICD has been carried out using a ruler prior to each treatment fraction in our institution. However, the ruler method is laborious and logging of data is not possible. The objective of this study is to replace the ruler‐based setup of the couch height with an independent, user‐friendly, optical camera‐based method whereby the radiation technologists have to move only the couch to the correct couch height, which is visible on a display. A camera‐based independent couch height measurement system (ICHS) was developed in cooperation with Panasonic Electric Works Western Europe. Clinical data showed that the ICHS is at least as accurate as the application of a ruler to verify the ICD. The camera‐based independent couch height measurement system has been successfully implemented in seven treatment rooms, since 10 September 2012. The benefits of this system are a more streamlined workflow, reduction of human errors during initial patient setup, and logging of the actual couch height at the isocenter. Daily QA shows that the systems are stable and operate within the set 1 mm tolerance. Regular QA of the system is necessary to guarantee that the system works correctly.

PACS number: 87.55 QR
The impact of CT scan energy on range calculation in proton therapy planning
Authors: Grantham Kevin K. , Li Hua , Zhao Tianyu , Klein Eric E.
Published: February 2017

The purpose of this study was to investigate the impact of tube potential (kVp) on the CT number (HU) to proton stopping power ratio (PSPR) conversion. The range and dosimetric change introduced by a mismatch in kVp used for the CT scan and the HU to PSPR table, based on a specific kVp, used to calculate dose are analyzed. Three HU to PSPR curves, corresponding to three kVp settings on the CT scanner, were created. A treatment plan was created for a single beam in a water phantom passing through a wedge‐shaped bone heterogeneity. The dose was recalculated by changing only the HU to PSPR table used in the dose calculation. The change in the position of the distal 90% isodose line was recorded as a function of heterogeneity thickness along the beam path. The dosimetric impact of a mismatch in kVp between the CT and the HU to PSPR table was investigated by repeating this procedure for five clinical plans comparing DVH data and dose difference distributions. The HU to PSPR tables diverge for CT numbers greater than 200 HU. In the phantom plan, the divergence of the tables resulted in a difference in range of 1.6 mm per cm of bone in the beam path, for the HU used. For the clinical plans, the dosimetric effect of a kVp mismatch depends on the amount of bone in the beam path and the proximity of OARs to the distal range of the planned beams. A mismatch in kVp between the CT and the HU to PSPR table can introduce inaccuracy in the proton beam range. For dense bone, the measured range difference was approximately 1.6 mm per cm of bone along the beam path. However, the clinical cases analyzed showed a range change of 1 mm or less. Caution is merited when such a mismatch may occur.

PACS numbers: 87.55.D, 87.55.Qr
Calibration coefficients of dosimeters used in mammography for various target/filter combinations
Authors: Sekimoto Michiharu , Katoh Yoh , Katoh Tsuguhisa
Published: February 2017

A wide variety of existing combinations of target and filter materials (target/filter combinations) are used in mammography equipment. The patient dose depends on the X‐ray quality that is derived from the target/filter combination, and a calibration of the dosimeter that is used in the measurement that corresponds to the specific target/filter combination is necessary. However, dosimeters in mammography are generally calibrated with reference to the X‐ray quality of Mo/Mo or W/Al combinations, and it is unclear whether or not the X‐ray quality that is derived from other target/filter combinations will affect the calibration coefficients. In this paper, the calibration coefficients of different dosimeters were evaluated for target/filter combinations. For an ionization chamber‐type dosimeter, good energy dependence was found and the effect of the target/filter combination was small. However, for a semiconductor dosimeter, a large energy dependence was found, and different calibration coefficients that depended on the target/filter combination used were required.

PACS number: 87.59.E‐
Episcleral eye plaque dosimetry comparison for the Eye Physics EP917 using Plaque Simulator and Monte Carlo simulation
Authors: Zimmermann Leonard W. , Amoush Ahmad , Wilkinson Douglas A.
Published: February 2017

This work is a comparative study of the dosimetry calculated by Plaque Simulator, a treatment planning system for eye plaque brachytherapy, to the dosimetry calculated using Monte Carlo simulation for an Eye Physics model EP917 eye plaque. Monte Carlo (MC) simulation using MCNPX 2.7 was used to calculate the central axis dose in water for an EP917 eye plaque fully loaded with 17 IsoAid Advantage seeds. In addition, the dosimetry parameters , and were calculated for the IsoAid Advantage model IAI‐125 seed and benchmarked against published data. Bebig Plaque Simulator (PS) v5.74 was used to calculate the central axis dose based on the AAPM Updated Task Group 43 (TG‐43U1) dose formalism. The calculated central axis dose from MC and PS was then compared. When the MC dosimetry parameters for the IsoAid Advantage seed were compared with the consensus values, Λ agreed with the consensus value to within 2.3%. However, much larger differences were found between MC calculated gL(r) and and the consensus values. The differences between MC‐calculated dosimetry parameters are much smaller when compared with recently published data. The differences between the calculated central axis absolute dose from MC and PS ranged from 5% to 10% for distances between 1 and 12 mm from the outer scleral surface. When the dosimetry parameters for the seed from this study were used in PS, the calculated absolute central axis dose differences were reduced by 2.3% from depths of 4 to 12 mm from the outer scleral surface. We conclude that PS adequately models the central dose profile of this plaque using its defaults for the IsoAid model IAI‐125 at distances of 1 to 7 mm from the outer scleral surface. However, improved dose accuracy can be obtained by using updated dosimetry parameters for the IsoAid model IAI‐125 seed.

PACS number: 87.55.K‐
Determination of using MLC‐collimated rectangular fields for absolute dosimetry of the CyberKnife
Authors: Gersh Jacob A. , Willett Benjamin
Published: February 2017

Traditional CyberKnife (CK) calibration uses TG‐51, which requires to be defined using the standard reference condition of 100 cm SSD in a field. Since the CK is calibrated using a 6 cm fixed‐aperture collimating cone at 80 cm SAD, the BJR‐25 method is commonly used to relate circular‐field PDDs to square‐field PDDs for determination. Using the InCise MLC system, the CK is able to deliver rectangular fields, allowing a more direct measurement of using conventional reference conditions. We define the PDD correction factor () as the ratio of measured using CK reference conditions to that measured using standard TG‐51 reference conditions. Using four ionization chambers (A1SL, CC08, CC13, and A19), is measured using a 6 cm fixed cone at 80 cm SSD and at 100 cm SSD using an effective MLC‐collimated field. These values are used to calculate , while the latter is used to directly calculate a value. This direct value is then compared to values determined using the BJR‐25 method. Using the MLC system, this study demonstrates conversion between the measured using CyberKnife reference conditions and TG‐51 reference conditions. These values provide the means for derivation of a curve as a function of direct measurements of using a 6 cm fixed‐aperture collimating cone at 80 cm SSD.

PACS number: 87.55.Qr
Effect of electron contamination on in vivo dosimetry for lung block shielding during TBI
Authors: Narayanasamy Ganesh , Cruz Wilbert , Saenz Daniel L. , Stathakis Sotirios , Papanikolaou Niko , Kirby Neil
Published: February 2017

Our institution performs in vivo verification measurement for each of our total body irradiation (TBI) patients with optically stimulated luminescent dosimeters (OSLD). The lung block verification measurements were commonly higher than expected. The aim of this work is to understand this discrepancy and improve the accuracy of these lung block verification measurements. Initially, the thickness of the lung block was increased to provide adequate lung sparing. Further tests revealed the increase was due to electron contamination dose emanating from the lung block. The thickness of the bolus material covering the OSLD behind the lung block was increased to offset the electron contamination. In addition, the distance from the lung block to the dosimeter was evaluated for its effect on the OSLD reading and found to be clinically insignificant over the range of variability in our clinic. The results show that the improved TBI treatment technique provides for better accuracy of measured dose in vivo and consistency of patient setup.

PACS number(s): 87.53.Bn, 87.53.Kn, 87.55.N‐, 87.55.Qr
Two‐year experience with the commercial Gamma Knife Check software
Authors: Xu Andy (Yuanguang) , Bhatnagar Jagdish , Bednarz Greg , Novotny Josef , Flickinger John , Lunsford L. Dade , Huq M. Saiful
Published: February 2017

The Gamma Knife Check software is an FDA approved second check system for dose calculations in Gamma Knife radiosurgery. The purpose of this study was to evaluate the accuracy and the stability of the commercial software package as a tool for independent dose verification. The Gamma Knife Check software version 8.4 was commissioned for a Leksell Gamma Knife Perfexion and a 4C unit at the University of Pittsburgh Medical Center in May 2012. Independent dose verifications were performed using this software for 319 radiosurgery cases on the Perfexion and 283 radiosurgery cases on the 4C units. The cases on each machine were divided into groups according to their diagnoses, and an averaged absolute percent dose difference for each group was calculated. The percentage dose difference for each treatment target was obtained as the relative difference between the Gamma Knife Check dose and the dose from the tissue maximum ratio algorithm (TMR 10) from the GammaPlan software version 10 at the reference point. For treatment plans with imaging skull definition, results obtained from the Gamma Knife Check software using the measurement‐based skull definition method are used for comparison. The collected dose difference data were also analyzed in terms of the distance from the treatment target to the skull, the number of treatment shots used for the target, and the gamma angles of the treatment shots. The averaged percent dose differences between the Gamma Knife Check software and the GammaPlan treatment planning system are 0.3%, 0.89%, 1.24%, 1.09%, 0.83%, 0.55%, 0.33%, and 1.49% for the trigeminal neuralgia, acoustic neuroma, arteriovenous malformation (AVM), meningioma, pituitary adenoma, glioma, functional disorders, and metastasis cases on the Perfexion unit. The corresponding averaged percent dose differences for the 4C unit are 0.33%, 1.2%, 2.78% 1.99%, 1.4%, 1.92%, 0.62%, and 1.51%, respectively. The dose difference is, in general, larger for treatment targets in the peripheral regions of the skull owing to the difference in the numerical methods used for skull shape simulation in the GammaPlan and the Gamma Knife Check software. Larger than 5% dose differences were observed on both machines for certain targets close to patient skull surface and for certain targets in the lower half of the brain on the Perfexion, especially when shots with 70 and/or 110 gamma angles are used. Out of the 1065 treatment targets studied, a 5% cutoff criterion cannot always be met for the dose differences between the studied versions of the Gamma Knife Check software and the planning system for 40 treatment targets.

PACS number(s): 87.55.Qr, 87.56.Fc
A report from the AAPM Subcommittee on Guidelines for Competency Evaluation for Clinical Medical Physicists in Radiation Oncology
Authors: Pavord Daniel C. , Birnbaum Steven , Boccuzzi Douglas , deBoer Steven , Freedman D. Jay , Schell Michael , Sutlief Steven
Published: February 2017

The goal of this report is to provide a framework from which an institution can develop a competency and credentialing program. It is not intended to be adopted as written, but rather as a list of suggestions from which the institution develops their program. A clear distinction should be made between the initial evaluation of the competency of new staff (credentialing) and the ongoing verification of the competency of existing staff. Furthermore, whenever new technologies are implemented, the entire staff would be subject to the credentialing process. Competencies involve the ongoing verification of the performance of a procedure according to the established policies and procedures at a facility. This can be done by audits of work product, direct observation of performance, self‐evaluation, or testing.

PACS number(s): 87.10.‐e, 87.90.+y
Analysis of setup error based on CTVision for nasopharyngeal carcinoma during IGRT
Authors: Zhang Shuxu , Zhou Xiang , Zhang Quanbin , Jiang Shaohui , Wang Ruihao , Zhang Guoqian , Lei Huaiyu , Lin Shengqu
Published: February 2017

The aim of the present study was to investigate the role of CTVision in interfractional setup errors during intensity‐modulated radiation therapy (IMRT) in 12 nasopharyngeal carcinoma (NPC) patients. The trend of setup errors as a function of time during a fractionated radiotherapy course was investigated, and the influence of reconstructive thickness on image reconstruction for setup errors was analyzed. The appropriate planning target volume (PTV) margin and planning risk volume (PRV) margin were defined to provide a reference for the design of IMRT for NPC. Based on CTVision, online CT was performed weekly for each patient. Setup errors were measured by registration between the CT reconstructed image and reference image. Mean of setup errors, estimated population systematic (:), and population random (σ) errors were calculated using SPSS (v15.0). Optimum PTV and PRV margins were calculated. In the clinical data, for the LR (left–right), SI (superior–inferior), and AP (anterior–posterior) directions, : was 0.8, 0.8, and 1.0 mm, respectively, and σ was 1.0, 1.3, and 0.8 mm, respectively. In the LR, SI, and AP directions, PTV margins were at least 2.7, 2.9, and 3.0 mm, respectively, and PRV margins were at least 1.5, 1.7, and 1.7 mm, respectively. No significant differences in setup errors were observed during the fractionated radiotherapy course . However, CT image reconstruction with different thicknesses affected the accuracy of measurements for setup errors, particularly in the SI direction. The application of CTVision to correct setup errors is important and can provide reasonable margins to guarantee the coverage of PTVs and spare organs at risk. A thickness of 3 mm in the reconstructed image is appropriate for the measurement of setup errors by image registration.

PACS number(s): 87.55.Qr
Low‐dose 2.5 MV cone‐beam computed tomography with thick CsI flat‐panel imager
Authors: Tang Grace , Moussot Christopher , Morf Daniel , Seppi Edward , Amols Howard
Published: February 2017

Most of the treatment units, both new and old models, are equipped with a megavoltage portal imager but its use for volumetric imaging is limited. This is mainly due to the poor image quality produced by the high‐energy treatment beam ( MV). A linac at our center is equipped with a prototype 2.5 MV imaging beam. This study evaluates the feasibility of low‐dose megavoltage cone‐beam imaging with the 2.5 MV beam and a thick cesium iodide detector, which is a high‐efficiency imager. Basic imaging properties such as spatial resolution and modulation transfer function were assessed for the 2.5 MV prototype imaging system. For image quality and imaging dose, a series of megavoltage cone‐beam scans were acquired for the head, thorax, and pelvis of an anthropomorphic phantom and were compared to kilovoltage cone‐beam and 6X megavoltage cone‐beam images. To demonstrate the advantage of MV imaging, a phantom with metallic inserts was scanned and the image quality was compared to CT and kilovoltage cone‐beam scans. With a lower energy beam and higher detector efficiency, the 2.5 MV imaging system generally yields better image quality than does the 6 MV imaging system with the conventional MV imager. In particular, with the anthropomorphic phantom studies, the contrast to noise of bone to tissue is generally improved in the 2.5 MV images compared to 6 MV. With an image quality sufficient for bony alignment, the imaging dose for 2.5 MV cone‐beam images is MU compared to 26 MU in 6 MV cone‐beam scans for the head, thorax, and pelvis regions of the phantom. Unlike kilovoltage cone‐beam, the 2.5 MV imaging system does not suffer from high‐Z image artifacts. This can be very useful for treatment planning in cases where high‐Z prostheses are present.

PACS number(s): 87.57.Q‐
MRI geometric distortion: Impact on tangential whole‐breast IMRT
Authors: Walker Amy , Metcalfe Peter , Liney Gary , Batumalai Vikneswary , Dundas Kylie , Glide‐Hurst Carri , Delaney Geoff P , Boxer Miriam , Yap Mei Ling , Dowling Jason , Rivest‐Henault David , Pogson Elise , Holloway Lois
Published: February 2017

The purpose of this study was to determine the impact of magnetic resonance imaging (MRI) geometric distortions when using MRI for target delineation and planning for whole‐breast, intensity‐modulated radiotherapy (IMRT). Residual system distortions and combined systematic and patient‐induced distortions are considered. This retrospective study investigated 18 patients who underwent whole‐breast external beam radiotherapy, where both CT and MRIs were acquired for treatment planning. Distortion phantoms were imaged on two MRI systems, dedicated to radiotherapy planning (a wide, closed‐bore 3T and an open‐bore 1T). Patient scans were acquired on the 3T system. To simulate MRI‐based planning, distortion maps representing residual system distortions were generated via deformable registration between phantom CT and MRIs. Patient CT images and structures were altered to match the residual system distortion measured by the phantoms on each scanner. The patient CTs were also registered to the corresponding patient MRI scans, to assess patient and residual system effects. Tangential IMRT plans were generated and optimized on each resulting CT dataset, then propagated to the original patient CT space. The resulting dose distributions were then evaluated with respect to the standard clinically acceptable DVH and visual assessment criteria. Maximum residual systematic distortion was measured to be 7.9 mm () and 11.9 mm () for the 3T and 1T scanners, respectively, which did not result in clinically unacceptable plans. Eight of the plans accounting for patient and systematic distortions were deemed clinically unacceptable when assessed on the original CT. For these plans, the mean difference in PTV (volume receiving 95% prescription dose) was and for right‐ and left‐sided patients, respectively. Residual system distortions alone had minimal impact on the dosimetry for the two scanners investigated. The combination of MRI systematic and patient‐related distortions can result in unacceptable dosimetry for whole‐breast IMRT, a potential issue when considering MRI‐only radiotherapy treatment planning.

PACS number(s): 87.61.‐c, 87.57.cp, 87.57.nj, 87.55.D‐
RadShield: semiautomated shielding design using a floor plan driven graphical user interface
Authors: DeLorenzo Matthew C. , Wu Dee H. , Yang Kai , Rutel Isaac B.
Published: February 2017

The purpose of this study was to introduce and describe the development of RadShield, a Java‐based graphical user interface (GUI), which provides a base design that uniquely performs thorough, spatially distributed calculations at many points and reports the maximum air‐kerma rate and barrier thickness for each barrier pursuant to NCRP Report 147 methodology. Semiautomated shielding design calculations are validated by two approaches: a geometry‐based approach and a manual approach. A series of geometry‐based equations were derived giving the maximum air‐kerma rate magnitude and location through a first derivative root finding approach. The second approach consisted of comparing RadShield results with those found by manual shielding design by an American Board of Radiology (ABR)‐certified medical physicist for two clinical room situations: two adjacent catheterization labs, and a radiographic and fluoroscopic (R&F) exam room. RadShield's efficacy in finding the maximum air‐kerma rate was compared against the geometry‐based approach and the overall shielding recommendations by RadShield were compared against the medical physicist's shielding results. Percentage errors between the geometry‐based approach and RadShield's approach in finding the magnitude and location of the maximum air‐kerma rate was within 0.00124% and 14 mm. RadShield's barrier thickness calculations were found to be within 0.156 mm lead (Pb) and 0.150 mm lead (Pb) for the adjacent catheterization labs and R&F room examples, respectively. However, within the R&F room example, differences in locating the most sensitive calculation point on the floor plan for one of the barriers was not considered in the medical physicist's calculation and was revealed by the RadShield calculations. RadShield is shown to accurately find the maximum values of air‐kerma rate and barrier thickness using NCRP Report 147 methodology. Visual inspection alone of the 2D X‐ray exam distribution by a medical physicist may not be sufficient to accurately select the point of maximum air‐kerma rate or barrier thickness.

PACS number(s): 87.55.N, 87.52.‐g, 87.59.Bh, 87.57.‐s
Comparison of liver volumetry on contrast‐enhanced CT images: one semiautomatic and two automatic approaches
Authors: Cai Wei , He Baochun , Fan Yingfang , Fang Chihua , Jia Fucang
Published: February 2017

This study was to evaluate the accuracy, consistency, and efficiency of three liver volumetry methods— one interactive method, an in‐house‐developed 3D medical Image Analysis (3DMIA) system, one automatic active shape model (ASM)‐based segmentation, and one automatic probabilistic atlas (PA)‐guided segmentation method on clinical contrast‐enhanced CT images. Forty‐two datasets, including 27 normal liver and 15 space‐occupying liver lesion patients, were retrospectively included in this study. The three methods — one semiautomatic 3DMIA, one automatic ASM‐based, and one automatic PA‐based liver volumetry — achieved an accuracy with VD (volume difference) of , and 3.06% in the normal group, respectively, and with VD of , and 4.14% in the space‐occupying lesion group, respectively. However, the three methods achieved an efficiency of 27.63 mins, 1.26 mins, 1.18 mins on average, respectively, compared with the manual volumetry, which took 43.98 mins. The high intraclass correlation coefficient between the three methods and the manual method indicated an excellent agreement on liver volumetry. Significant differences in segmentation time were observed between the three methods (3DMIA, ASM, and PA) and the manual volumetry (), as well as between the automatic volumetries (ASM and PA) and the semiautomatic volumetry (3DMIA) (). The semiautomatic interactive 3DMIA, automatic ASM‐based, and automatic PA‐based liver volumetry agreed well with manual gold standard in both the normal liver group and the space‐occupying lesion group. The ASM‐ and PA‐based automatic segmentation have better efficiency in clinical use.

PACS number(s): 87.55.‐x
Diagnostic X‐ray facilities as per quality control performances in Tanzania
Authors: Sungita Yesaya Y. , Mdoe Simon S.L. , Msaki Peter
Published: February 2017

Without appropriate quality control (QC) and preventative maintenance (PM) measures for X‐ray machines in place, the benefits of reduced dose to the patient and early diagnosis will not be realized. Quality control and PM also make it possible to unify X‐ray‐imaging practices in the country using international image quality guidelines. The impetus for the present work resulted from the concern that with the recent increase in the numbers of X‐ray machines in Tanzania, but with limited technical support to maintain and operate them, can increase radiation risk to patients and lower diagnostic accuracy. The aim of this work is to report on the current status of diagnostic X‐ray machines in Tanzania in order to produce the data needed to formulate QC and PM policies and strategies. These policies and strategies are needed to ensure that patients receive the lowest possible radiation risk and maximum health benefits from X‐ray examinations. Four QC tests were performed on a total of 196 X‐ray units. Accurate beam alignment and collimation were tested on 80 (41%) units, the timer accuracy was tested on 120 (61%) units, and a radiation leakage test was performed on 47(24%) units. Preventative maintenance tests were performed on all 196 X‐ray units. The results showed that of the units tested for QC, 59% failed the kilovoltage (kVp) test, 57% failed the timer accuracy test, 60% failed the beam alignment test, and 20% failed the radiation leakage test. Only 13% of the units passed the PM test: 53% of the units were defective, and 34% were out of order. As a result of the PM findings, the government has introduced a rehabilitation project to service X‐ray units and replace nonoperational X‐ray units. The new units have full support service contracts signed by their suppliers. As a result of the QC findings, X‐ray maintenance retraining programs have been introduced.

PACS numbers: 87.52.‐g, 87.52.Tr, 87.58.SP, 87.59.Bh
Book Review
Authors: Goff David L.
Published: February 2017

Medical Health Physics, David Medich & Christopher Martel Editors, Medical Physics Publishing, ISBN 1‐30524‐31‐5, $75.00
MAGIC polymer gel for dosimetric verification in boron neutron capture therapy
Authors: Uusi–Simola Jouni , Heikkinen Sami , Kotiluoto Petri , Serén Tom , Seppälä Tiina , Auterinen Iiro , Savolainen Sauli
Published: February 2017

Radiation‐sensitive polymer gels are among the most promising three‐dimensional dose verification tools developed to date. We tested the normoxic polymer gel dosimeter known by the acronym MAGIC (methacrylic and ascorbic acid in gelatin initiated by copper) to evaluate its use in boron neutron capture therapy (BNCT) dosimetry. We irradiated a large cylindrical gel phantom (diameter: 10 cm; length: 20 cm) in the epithermal neutron beam of the Finnish BNCT facility at the FiR 1 nuclear reactor. Neutron irradiation was simulated with a Monte Carlo radiation transport code MCNP. To compare dose–response, gel samples from the same production batch were also irradiated with 6 MV photons from a medical linear accelerator. Irradiated gel phantoms then underwent magnetic resonance imaging to determine their R2 relaxation rate maps. The measured and normalized dose distribution in the epithermal neutron beam was compared with the dose distribution calculated by computer simulation. The results support the feasibility of using MAGIC gel in BNCT dosimetry.

PACS numbers: 87.53.Qc, 87.53.Wz, 87.66.Ff
WCK 5222 (Cefepime-Zidebactam) Antimicrobial Activity against Clinical Isolates of Gram-Negative Bacteria Collected Worldwide in 2015
Authors: Sader Helio S. , Castanheira Mariana , Huband Michael , Jones Ronald N. , Flamm Robert K.
Published: February 2017

WCK 5222 consists of cefepime combined with zidebactam, a bicyclo-acyl hydrazide β-lactam enhancer antibiotic with a dual action involving binding to Gram-negative bacterial PBP2 and β-lactamase inhibition. We evaluated the
in vitro
activity of cefepime-zidebactam against 7,876 contemporary (2015) clinical isolates of
Enterobacteriaceae
(
n
= 5,946),
Pseudomonas aeruginosa
(
n
= 1,291), and
Acinetobacter
spp. (
n
= 639) from the United States (
n
= 2,919), Europe (
n
= 3,004), the Asia-Pacific (
n
= 1,370), and Latin America (
n
= 583). The isolates were tested by a reference broth microdilution method for susceptibility against cefepime-zidebactam (1:1 and 2:1 ratios) and comparator agents. Cefepime-zidebactam was the most active compound tested against
Enterobacteriaceae
(MIC
50/90
, ≤0.03/0.12 μg/ml [1:1] and 0.06/0.25 μg/ml [2:1]; 99.9% of isolates were inhibited at ≤4 [1:1] and ≤8 μg/ml [2:1]). Cefepime-zidebactam was active against individual
Enterobacteriaceae
species (MIC
50/90
, ≤0.03 to 0.06/≤0.03 to 0.5 μg/ml [1:1]) and retained potent activity against carbapenem-resistant isolates (MIC
50/90
, 1/4 μg/ml; 99.3% of isolates were inhibited at ≤8 μg/ml [1:1]). Cefepime-zidebactam activity was consistent among geographic regions, and only one isolate showed MIC values of >8 μg/ml (1:1). Cefepime-zidebactam was also very active against
P. aeruginosa
with MIC
50/90
values of 1/4 μg/ml, and 99.5% of isolates were inhibited at ≤8 μg/ml (1:1). The MIC values for cefepime-zidebactam at the 1:1 ratio were generally 2-fold lower than those for cefepime-zidebactam at the 2:1 ratio (MIC
50/90
, 2/8 μg/ml) and zidebactam alone (MIC
50/90
, 4/8 μg/ml). Against
Acinetobacter
spp., cefepime-zidebactam at 1:1 and 2:1 ratios (MIC
50/90
, 16/32 μg/ml for both) was 4-fold more active than cefepime or ceftazidime. Zidebactam exhibited potent
in vitro
antimicrobial activity against some organisms. These results support the clinical development of WCK 5222 for the treatment of Gram-negative bacterial infections, including those caused by multidrug-resistant isolates.
Duodenal variceal bleed: an unusual cause of upper gastrointestinal bleed and a difficult diagnosis to make
Authors: Bhagani Shradha , Winters Conchubhair , Moreea Sulleman
Published: February 2017

We present a case of recurrent upper gastrointestinal (GI) bleeding in a man aged 57 years with primary biliary cholangitis who was ultimately diagnosed with an isolated duodenal variceal bleed, which was successfully treated with histoacryl glue injection. Duodenal varices are an uncommon presentation of portal hypertension and can result in significant GI bleeding with a high mortality. Diagnosis can be difficult and therapeutic options limited. Endoscopic variceal sclerotherapy with histoacryl glue provides an effective treatment, though endoscopists need to remain aware of and vigilant for the serious complications of this treatment option.
Role of canine circovirus in dogs with acute haemorrhagic diarrhoea
Authors: Anderson A. , Hartmann K. , Leutenegger C. M. , Proksch A. L. , Mueller R. S. , Unterer S.
Published: February 2017

Canine circovirus (CanineCV) has been detected in some dogs with severe haemorrhagic diarrhoea, but its pathogenic role is unclear. This study evaluated a suspected association between the presence of CanineCV and acute haemorrhagic diarrhoea syndrome (AHDS) in dogs. The prevalence of CanineCV in dogs with AHDS was compared with that in healthy dogs and those infected with canine parvovirus (CPV). Additionally, time to recovery and mortality rate were compared between CanineCV‐positive and CanineCV‐negative dogs. Faecal samples of dogs with AHDS (n=55), healthy dogs (n=66) and dogs infected with CPV (n=54) were examined by two real‐time TaqMan PCR assays targeting the replicase and capsid genes of CanineCV. CanineCV was detected in faecal samples of two dogs with AHDS, three healthy controls and seven dogs infected with CPV. Among the three groups, there was no significant difference in prevalence of CanineCV. CPV‐infected animals that were coinfected with CanineCV had a significantly higher mortality rate compared with those negative for CanineCV. CanineCV does not appear to be the primary causative agent of AHDS in dogs, but might play a role as a negative co‐factor in disease outcome in dogs with CPV infection.
Parasitism, immune response, and egg production of the spearhead bluet (Coenagrion hastulatum) damselfly
Authors: Kaunisto Kari M. , Kaunisto Pipsa , Ilvonen Jaakko J. , Suhonen Jukka
Published: February 2017

Theoretical models predict that parasites reduce reproductive success of their hosts, but very few empirical studies have given support to this. Using the spearhead bluet (Coenagrion hastulatum (Charpentier, 1825)) damselfly, we tested how immune response, wing length, and the number of both endo- and ecto-parasites affect egg production of host damselflies. The study was conducted with four different populations in southwest Finland. We found a negative association between endoparasitic gregarines and number of host eggs. Furthermore, immune response increased with the number of water mites, but decreased with the number of eggs. Contrary to previous studies with other damselfly species, the number of ectoparasitic water mites did not affect the number of eggs. Moreover, wing length, used as an indicator of individual size, was not associated with egg numbers. The negative effect of gregarine parasites on egg numbers is likely to affect the composition of host populations, i.e., damselflies that show higher resistance to these endoparasites will have more of their offspring represented in subsequent generations. In future, more experimental research on the varying effects of different parasite species on the number of eggs is needed.
Holographic cosmology from BIonic solutions
Authors: Sepehri Alireza , Faizal Mir , Setare Mohammad Reza , Ali Ahmed Farag
Published: February 2017

In this paper, we will use a BIonic solution for analyzing the holographic cosmology. A BIonic solution is a configuration of a D3-brane and an anti-D3-brane connected by a wormhole, and holographic cosmology is a recent proposal to explain cosmic expansion by using the holographic principle. In our model, a BIonic configuration will be produced by the transition of fundamental black strings. The formation of a BIonic configuration will cause inflation. As the D3-brane moves away from the anti-D3-brane, the wormhole will get annihilated, and the inflation will end with the annihilation of this wormhole. However, it is possible for a D3-brane to collide with an anti-D3-brane. Such a collision will occur if the distance between the D3-brane and the anti-D3-brane reduces, and this will create tachyonic states. We will demonstrate that these tachyonic states will lead to the formation of a new wormhole, and this will cause acceleration of the universe before such a collision.
Redundant Bit Security in RFIDs: Architecture Design and Security Performance Evaluation
Authors: Jeddi Zahra , Khattab Ahmed , Amini Esmaeil , Bayoumi Madgy
Published: February 2017

This paper presents an analysis of the security performance and evaluation of the hardware architecture of the redundant bit security (RBS) cryptosystem. RBS is a lightweight symmetric encryption algorithm that targets resource-constrained RFID devices. Unlike the existing cryptosystems, RBS simultaneously provides confidentiality, authentication, and integrity of the plaintext by inserting hash-generated redundant bits among the already modified plaintext data. A flexible-length hash algorithm in our optimized hardware architecture allows RBS to support different key sizes which allows flexibility in the security level. Our analysis shows the resilience of RBS against powerful and well-known attacks such as differential attacks and known-plaintext attacks. We compare the performance of the RBS cryptosystem against other distinguished ciphers developed for RFID systems. Simulation results show that RBS results in approximately 100%, 239%, and 153% higher hardware efficiencies while requiring 48%, 56%, and 59% less energy-per-bit compared to H-PRESENT, HB-2, and Grain, respectively. Such results present confirmatory evidence that RBS is a superior solution for providing security in resource-constrained systems such as RFID systems especially when authentication is a priority.