bluuebunny/crossref_metadata_2025 huggingface dataset:
Deformable image registration and interobserver variation in contour propagation for radiation therapy planning
Authors: Riegel Adam C. , Antone Jeffrey G. , Zhang Honglai , Jain Prachi , Raince Jagdeep , Rea Anthony , Bergamo Angelo M. , Kapur Ajay , Potters Louis
Published: February 2017

Deformable image registration (DIR) and interobserver variation inevitably introduce uncertainty into the treatment planning process. The purpose of the current work was to measure deformable image registration (DIR) errors and interobserver variability for regions of interest (ROIs) in the head and neck and pelvic regions. Measured uncertainties were combined to examine planning margin adequacy for contours propagated for adaptive therapy and to assess the trade‐off of DIR and interobserver uncertainty in atlas‐based automatic segmentation. Two experienced dosimetrists retrospectively contoured brainstem, spinal cord, anterior oral cavity, larynx, right and left parotids, optic nerves, and eyes on the planning CT () and attenuation‐correction CT of diagnostic PET/CT () for 30 patients who received radiation therapy for head and neck cancer. Two senior radiation oncology residents retrospectively contoured prostate, bladder, and rectum on the postseed‐implant CT () and planning CT () for 20 patients who received radiation therapy for prostate cancer. Interobserver variation was measured by calculating mean Hausdorff distances between the two observers' contours. was deformably registered to via commercially available multipass B‐spline DIR. contours were propagated and compared with contours via mean Hausdorff distances. These values were summed in quadrature with interobserver variation for margin analysis and compared with interobserver variation for statistical significance using two‐tailed t‐tests for independent samples (). Combined uncertainty ranged from 1.5‐5.8 mm for head and neck structures and 3.1‐3.7 mm for pelvic structures. Conventional 5 mm margins may not be adequate to cover this additional uncertainty. DIR uncertainty was significantly less than interobserver variation for four head and neck and one pelvic ROI. DIR uncertainty was not significantly different than interobserver variation for four head and neck and one pelvic ROI. DIR uncertainty was significantly greater than interobserver variation for two head and neck and one pelvic ROI. The introduction of DIR errors may offset any reduction in interobserver variation by using atlas‐based automatic segmentation.

PACS number(s): 87.57.nj, 87.55.D‐
Effective method of measuring the radioactivity of ‐capsule prior to radioiodine therapy with significant reduction of the radiation exposure to the medical staff
Authors: Lützen Ulf , Zhao Yi , Marx Marlies , Imme Thea , Assam Isong , Siebert Frank‐Andre , Culman Juraj , Zuhayra Maaz
Published: February 2017

Radiation Protection in Radiology, Nuclear Medicine and Radio Oncology is of the utmost importance. Radioiodine therapy is a frequently used and effective method for the treatment of thyroid disease. Prior to each therapy the radioactivity of the ‐capsule must be determined to prevent misadministration. This leads to a significant radiation exposure to the staff. We describe an alternative method, allowing a considerable reduction of the radiation exposure. Two ‐capsules were measured multiple times in their own delivery lead containers — that is to say, ‐capsules remain inside the containers during the measurements (shielded measurement) using a dose calibrator and a well‐type and a thyroid uptake probe. The results of the shielded measurements were correlated linearly with the ‐capsules radioactivity to create calibration curves for the used devices. Additional radioactivity measurements of 50 ‐capsules of different radioactivities were done to validate the shielded measuring method. The personal skin dose rate was determined using calibrated thermo luminescent dosimeters. The determination coefficients for the calibration curves were for all devices. The relative uncertainty of the shielded measurement was . At a distance of 10 cm from the unshielded capsule the was , and on the surface of the lead container containing the ‐capsule the was 2.99 and for the two used container sizes. The calculated reduction of the effective dose by using the shielded measuring method was, depending on the used container size, 74.0% and 97.4%, compared to the measurement of the unshielded ‐capsule using a dose calibrator. The measured reduction of the effective radiation dose in the practice was 56.6% and 94.9 for size I and size II containers. The shielded ‐capsule measurement reduces the radiation exposure to the staff significantly and offers the same accuracy of the unshielded measurement in the same amount of time. In order to maintain the consistency of the measuring method, monthly tests have to be done by measuring a ‐capsule with known radioactivity.

PACS number(s): 93.85.Np, 92.20.Td, 87.50.yk, 87.53.Bn
A novel arc geometry setting for pelvic radiotherapy with extensive nodal involvement
Authors: Rossi Maija , Boman Eeva , Skyttä Tanja , Kapanen Mika
Published: February 2017

The aim of this study was to find optimal planning approach for large planning targets with complicated geometry requiring wide field openings. The study presents a novel approach for arc geometry design for pelvic targets with extensive nodal involvement. A total of 15 patients with anorectal carcinoma or vulvar cancer were selected retrospectively. For each patient, one seven‐field IMRT plan and three VMAT plans were calculated: one with two 360° arcs with no limitations for the field size (VMATw); one with two asymmetrically field‐size‐restricted 360° arcs (VMATr); and the proposed novel approach which consisted of one 360° arc with the field size restricted to the central PTV, and another arc divided into two 180° arcs, restricting the field sizes with the focus on the lymph nodes. The techniques were compared in terms of PTV coverage , dose maximum (D(max)), dose conformity index (CI), homogeneity index (HI), and organs at risk doses. The proposed novel approach with one full and two half arcs tended to have better PTV coverage (, compared to , and in VMATw, VMATr, and 7f‐IMRT, respectively) and lower maxima (, compared to , and in VMATw, VMATr, and 7f‐IMRT, respectively); and lower or equal organs at risk doses. The superiority of the proposed technique was more pronounced compared with the VMATw plans (, paired t‐test ), but the proposed technique was slightly better also in comparison with the VMATr plans and 7f‐IMRT plans . Radiotherapy treatment planning for large and complicated treatment volumes benefits not only from restricting the field size but also from careful field design that considers PTV geometry. This optimizes multileaf collimator movements, leading to better dose conformity and homogeneity.

PACS number(s): 87.53.Jw, 87.55.D, 87.56.jk:
Performance evaluation of the RITG148+ set of TomoTherapy quality assurance tools using RTQA2 radiochromic film
Authors: Lobb Eric C.
Published: February 2017

Version 6.3 of the software package offers eight automated analysis routines for quality assurance of the TomoTherapy platform. A performance evaluation of each routine was performed in order to compare results with traditionally accepted analysis techniques and verify that simulated changes in machine parameters are correctly identified by the software. Reference films were exposed according to AAPM TG‐148 methodology for each routine and the results were compared with either alternative software analysis techniques or manual analysis techniques in order to assess baseline agreement. Changes in machine performance were simulated through translational and rotational adjustments to subsequently irradiated films, and these films were analyzed to verify that the applied changes were accurately detected by each of the routines. For the Hounsfield unit routine, an assessment of the “Frame Averaging” functionality and the effects of phantom roll on the routine results are presented. All routines reported acceptable baseline results consistent with alternative analysis techniques, with 9 of the 11 baseline test results showing agreement of 0.1 mm/0.1° or better. Simulated changes were correctly identified by the routines within approximately with the exception of the Field Center vs. Jaw Setting routine, which was found to have limited accuracy in cases where field centers were not aligned for all jaw settings due to inaccurate autorotation of the film during analysis. The performance of the software package was found to be acceptable for introduction into our clinical environment as an automated alternative to traditional analysis techniques for routine TomoTherapy quality assurance testing.

PACS number(s): 87.55.Qr
Dosimetric accuracy of the cone‐beam CT‐based treatment planning of the Vero system: a phantom study
Authors: Yohannes Indra , Prasetio Heru , Kallis Karoline , Bert Christoph
Published: February 2017

We report an investigation on the accuracy of dose calculation based on the cone‐beam computed tomography (CBCT) images of the nonbowtie filter kV imaging system of the Vero linear accelerator. Different sets of materials and tube voltages were employed to generate the Hounsfield unit lookup tables (HLUTs) for both CBCT and fan‐beam CT (FBCT) systems. The HLUTs were then implemented for the dose calculation in a treatment planning system (TPS). Dosimetric evaluation was carried out on an in‐house‐developed cube phantom that consists of water‐equivalent slabs and inhomogeneity inserts. Two independent dosimeters positioned in the cube phantom were used in this study for point‐dose and two‐dimensional (2D) dose distribution measurements. The differences of HLUTs from various materials and tube voltages in both CT systems resulted in differences in dose calculation accuracy. We found that the higher the tube voltage used to obtain CT images, the better the point‐dose calculation and the gamma passing rate of the 2D dose distribution agree to the values determined in the TPS. Moreover, the insert materials that are not tissue‐equivalent led to higher dose‐calculation inaccuracy. There were negligible differences in dosimetric evaluation between the CBCT‐ and FBCT‐based treatment planning if the HLUTs were generated using the tissue‐equivalent materials. In this study, the CBCT images of the Vero system from a complex inhomogeneity phantom can be applied for the TPS dose calculation if the system is calibrated using tissue‐equivalent materials scanned at high tube voltage (i.e., 120 kV).

PACS number(s): 87.55.de, 87.56.Fc, 87.57.qp
Electrocardiogram‐gated coronary CT angiography dose estimates using ImPACT
Authors: Kobayashi Masanao , Asada Yasuki , Matsubara Kosuke , Suzuki Shouichi , Koshida Kichiro , Matsunaga Yuta , Haba Tomonobu , Kawaguchi Ai , Toyama Hiroshi , Kato Ryoichi
Published: February 2017

The primary study objective was to assess radiation doses using a modified form of the Imaging Performance Assessment of Computed Tomography (CT) scanner (ImPACT) patient dosimetry for cardiac applications on an Aquilion ONE ViSION Edition scanner, including the Ca score, target computed tomography angiography (CTA), prospective CTA, continuous CTA/cardiac function analysis (CFA), and CTA/CFA modulation. Accordingly, we clarified the CT dose index (CTDI) to determine the relationship between heart rate (HR) and X‐ray exposure. As a secondary objective, we compared radiation doses using modified ImPACT, a whole‐body dosimetry phantom study, and the k‐factor method to verify the validity of the dose results obtained with modified ImPACT. The effective dose determined for the reference person (4.66 mSv at 60 beats per minute (bpm) and 33.43 mSv at 90 bpm) were approximately 10% less than those determined for the phantom study (5.28 mSv and 36.68 mSv). The effective doses according to the k‐factor (; 2.57 mSv and 17.10 mSv) were significantly lower than those obtained with the other two methods. In the present study, we have shown that ImPACT, when modified for cardiac applications, can assess both absorbed and effective doses. The results of our dose comparison indicate that modified ImPACT dose assessment is a promising and practical method for evaluating coronary CTA.

PACS number(s): 87.57.Q‐, 87.59.Dj, 87.57.uq
Evaluation of cassette‐based digital radiography detectors using standardized image quality metrics: AAPM TG‐150 Draft Image Detector Tests
Authors: Li Guang , Greene Travis C. , Nishino Thomas K. , Willis Charles E.
Published: February 2017

The purpose of this study was to evaluate several of the standardized image quality metrics proposed by the American Association of Physics in Medicine (AAPM) Task Group 150. The task group suggested region‐of‐interest (ROI)‐based techniques to measure nonuniformity, minimum signal‐to‐noise ratio (SNR), number of anomalous pixels, and modulation transfer function (MTF). This study evaluated the effects of ROI size and layout on the image metrics by using four different ROI sets, assessed result uncertainty by repeating measurements, and compared results with two commercially available quality control tools, namely the Carestream DIRECTVIEW Total Quality Tool (TQT) and the GE Healthcare Quality Assurance Process (QAP). Seven Carestream DRX‐1C (CsI) detectors on mobile DR systems and four GE FlashPad detectors in radiographic rooms were tested. Images were analyzed using MATLAB software that had been previously validated and reported. Our values for signal and SNR nonuniformity and MTF agree with values published by other investigators. Our results show that ROI size affects nonuniformity and minimum SNR measurements, but not detection of anomalous pixels. Exposure geometry affects all tested image metrics except for the MTF. TG‐150 metrics in general agree with the TQT, but agree with the QAP only for local and global signal nonuniformity. The difference in SNR nonuniformity and MTF values between the TG‐150 and QAP may be explained by differences in the calculation of noise and acquisition beam quality, respectively. TG‐150's SNR nonuniformity metrics are also more sensitive to detector nonuniformity compared to the QAP. Our results suggest that fixed ROI size should be used for consistency because nonuniformity metrics depend on ROI size. Ideally, detector tests should be performed at the exact calibration position. If not feasible, a baseline should be established from the mean of several repeated measurements. Our study indicates that the TG‐150 tests can be used as an independent standardized procedure for detector performance assessment.

PACS number(s): 87.57.‐s, 87.57.C
Evaluation of the uncertainty in an EBT3 film dosimetry system utilizing net optical density
Authors: Marroquin Elsa Y. León , Herrera González José A. , Camacho López Miguel A. , Barajas José E. Villarreal , García‐Garduño Olivia A.
Published: February 2017

Radiochromic film has become an important tool to verify dose distributions for intensity‐modulated radiotherapy (IMRT) and quality assurance (QA) procedures. A new radiochromic film model, EBT3, has recently become available, whose composition and thickness of the sensitive layer are the same as those of previous EBT2 films. However, a matte polyester layer was added to EBT3 to prevent the formation of Newton's rings. Furthermore, the symmetrical design of EBT3 allows the user to eliminate side‐orientation dependence. This film and the flatbed scanner, Epson Perfection V750, form a dosimetry system whose intrinsic characteristics were studied in this work. In addition, uncertainties associated with these intrinsic characteristics and the total uncertainty of the dosimetry system were determined. The analysis of the response of the radiochromic film (net optical density) and the fitting of the experimental data to a potential function yielded an uncertainty of 2.6%, 4.3%, and 4.1% for the red, green, and blue channels, respectively. In this work, the dosimetry system presents an uncertainty in resolving the dose of 1.8% for doses greater than 0.8 Gy and less than 6 Gy for red channel. The films irradiated between 0 and 120 Gy show differences in the response when scanned in portrait or landscape mode; less uncertainty was found when using the portrait mode. The response of the film depended on the position on the bed of the scanner, contributing an uncertainty of 2% for the red, 3% for the green, and 4.5% for the blue when placing the film around the center of the bed of scanner. Furthermore, the uniformity and reproducibility radiochromic film and reproducibility of the response of the scanner contribute less than 1% to the overall uncertainty in dose. Finally, the total dose uncertainty was 3.2%, 4.9%, and 5.2% for red, green, and blue channels, respectively. The above uncertainty values were obtained by minimizing the contribution to the total dose uncertainty of the film orientation and film homogeneity.

PACS number(s): 87.53.Bn
Surface dose variations in 6 and 10 MV flattened and flattening filter‐free (FFF) photon beams
Authors: Cashmore Jason
Published: February 2017

As the use of linear accelerators operating in flattening filter‐free (FFF) modes becomes more widespread, it is important to have an understanding of the surface doses delivered to patients with these beams. Flattening filter removal alters the beam quality and relative contributions of low‐energy X‐rays and contamination electrons in the beam. Having dosimetric data to describe the surface dose and buildup regions under a range of conditions for FFF beams is important if clinical decisions are to be made. An Elekta Synergy linac with standard MLCi head has been commissioned to run at 6 MV and 10 MV running with the flattening filter in or out. In this linac the 6 MV FFF beam has been energy‐matched to the clinical beam on the central axis (). The 10 MV beam energy has not been adjusted. The flattening filter in both cases is replaced by a thin (2 mm) stainless steel plate. A thin window parallel plate chamber has been used to measure a comprehensive set of surface dose data in these beams for variations in field size and SSD, and for the presence of attenuators (wedge, shadow tray, and treatment couch). Surface doses are generally higher in FFF beams for small field sizes and lower for large field sizes with a crossover at at 6 MV and at 10 MV. This trend is also seen in the presence of the wedge, shadow tray, and treatment couch. Only small differences () are seen between the beams on varying SSD. At both 6 and 10 MV the filter‐free beams show far less variation with field size than conventional beams. By removing the flattening filter, a source of contamination electrons is exchanged for a source of low‐energy photons (as these are no longer attenuated). In practice these two components almost balance out. No significant effects on surface dose are expected by the introduction of FFF delivery.

PACS number(s): 87.53.Bn, 87.55.ne, 87.56.bd
Correlation of quantitative dynamic contrast‐enhanced MRI with microvascular density in necrotic, partial necrotic, and viable liver tumors in a rabbit model
Authors: Moon Jungwon , Kim Jae‐Hun , Choi Dongil , Yang Jehoon , Lee Min Woo , Choi Yoon‐La , Rhim, MD Hyunchul
Published: February 2017

The purpose of this study was to examine the correlation of quantitative dynamic contrast‐enhanced (DCE) magnetic resonance imaging (MRI) with microvessel density (MVD) in necrotic, partial necrotic, and viable tumors using a rabbit VX2 liver tumor model. Nine rabbits were used for this study. The complete necrotic area (CNA), partial necrotic area (PNA), and viable tumor area (VTA) of liver tumors were experimentally induced by radiofrequency ablation (RFA). DCE‐MRI data were processed based on the extended Kety model to estimate and vp parameters. The boundaries among CNA, PNA, and VTA were delineated based on H&E stain images, and MVD was assessed for each subregion of each VX2 tumor based. There were no correlations between ph‐parameters (, and ) and MVD for CNA. For PNA, the values were positively correlated with the MVD (). For VTA, we found a positive correlation between values and the MVD (). Measuring from both the PNA and the VTA, mean values were positively correlated with mean MVD (). In a rabbit VX2 liver tumor model, values correlated well with MVD counts of PNA and VTA in liver tumors.

PACS number(s): 87.19.If MRI
Spot scanning proton therapy minimizes neutron dose in the setting of radiation therapy administered during pregnancy
Authors: Wang Xin , Poenisch Falk , Sahoo Narayan , Zhu Ronald X. , Lii MingFwu , Gillin Michael T. , Li Jing , Grosshans David
Published: February 2017

This is a real case study to minimize the neutron dose equivalent (H) to a fetus using spot scanning proton beams with favorable beam energies and angles. Minimum neutron dose exposure to the fetus was achieved with iterative planning under the guidance of neutron H measurement. Two highly conformal treatment plans, each with three spot scanning beams, were planned to treat a 25‐year‐old pregnant female with aggressive recurrent chordoma of the base of skull who elected not to proceed with termination. Each plan was scheduled for delivery every other day for robust target coverage. Neutron H to the fetus was measured using a REM500 neutron survey meter placed at the fetus position of a patient simulating phantom. 4.1 and 44.1 were measured for the two initial plans. A vertex beam with higher energy and the fetal position closer to its central axis was the cause for the plan that produced an order higher neutron H. Replacing the vertex beam with a lateral beam reduced neutron H to be comparable with the other plan. For a prescription of 70 Gy in 35 fractions, the total neutron H to the fetus was estimated to be 0.35 mSv based on final measurement in single fraction. In comparison, the passive scattering proton plan and photon plan had an estimation of 26 and 70 mSv, respectively, for this case. While radiation therapy in pregnant patients should be avoided if at all possible, our work demonstrated spot scanning beam limited the total neutron H to the fetus an order lower than the suggested 5 mSv regulation threshold. It is far superior than passive scattering beam and careful beam selection with lower energy and keeping fetus further away from beam axis are essential in minimizing the fetus neutron exposure.

PACS number(s): 87.53.Bn, 87.55.D‐, 87.55.N‐
Dosimetric and volumetric changes in the rectum and bladder in patients receiving CBCT‐guided prostate IMRT: analysis based on daily CBCT dose calculation
Authors: Pearson David , Gill Sukhdeep K. , Campbell Nina , Reddy Krishna
Published: February 2017

Delivered dose can be calculated by transferring the planned treatment beams onto the daily CBCT. Bladder and rectum volumetric doses were calculated and correlated to the daily bladder and rectum fullness. Patients for this study underwent hypofractionated prostate IMRT to 70 Gy in 28 fractions. Daily CBCT was utilized for image guidance. A clinically acceptable plan was created using a CTV‐to‐PTV uniform margin of 5 mm. Image fusion was performed to transfer the bladder and rectum contours onto each CBCT. Contours were then edited to match the anatomy of each CBCT. Using the daily treatment isocenter, the planned beams were transferred onto the CBCT and daily and cumulative DVHs calculated. For the results a total of 168 daily CBCTs were evaluated. The bladder was found to be smaller for 74.7% of the 168 daily CBCTs accessed in this study. This reduction in volume correlated to an increase in the cumulative bladder V70 Gy from 9.47% on the planning CT to 10.99% during treatment. V70Gy for the rectum was 7.27% on the planning CT, when all six patients were averaged, and increased to 11.56% on the average of all daily treatment CBCTs. Increases in volumetric rectum dose correlated with increases in rectal volume. For one patient, the rectum and bladder absolute V70 Gy, averaged over the course of treatment, increased by 295% and 61%, respectively. Larger variations in the daily bladder and rectal volume were observed and these correlated to large deviations from the volumetric dose received by these structures. In summary, bladder and rectum volume changes during treatment have an effect on the cumulative dose received by these organs. It was observed that the volumetric dose received by the bladder decreases as the volume of the bladder increases. The inverse was true for the rectum.

PACS number(s): 87.55.dk‐, 87.57.Q‐
Dosimetric assessment of brass mesh bolus for postmastectomy photon radiotherapy
Authors: Manger Ryan , Paxton Adam , Cerviño Laura
Published: February 2017

Brass mesh bolus has been shown to be an acceptable substitute for tissue‐equivalent bolus to increase superficial dose for chest wall tangent photon radiotherapy. This work investigated the increase in surface dose, the change in the dose at depth, and the safety implications of higher energy photon beams when using brass mesh bolus for postmastectomy chest wall radiotherapy. A photon tangent plan was delivered to a thorax phantom, and the superficial dose ranged from 40%–72% of prescription dose with no bolus. The surface dose increased to 75%–110% of prescription dose with brass mesh bolus and 85%–109% of prescription dose with tissue‐equivalent bolus. It was also found that the dose at depth when using brass mesh bolus is comparable to that measured with no bolus for en face and oblique incidence. Monte Carlo calculations were used to assess the photoneutron production from brass mesh bolus used with 15 MV and 24 MV photon beams. The effective dose from photoneutrons was approximated and found to be relatively small, yet not negligible. Activation products generated by these photoneutrons, the surface dose rate due to the activation products, and the half‐life of the activation products were also considered in this work. The authors conclude that brass mesh bolus is a reasonable alternative to tissue‐equivalent bolus, and it may be used with high‐energy beam; but one should be aware of the potential increased effective dose to staff and patients due to the activation products produced by photoneutrons.

PACS number(s): 87.53.Kn, 87.55.K
Comparison of the low‐contrast detectability of two ultrasound systems using a grayscale phantom
Authors: Lorentsson Robert , Hosseini Nasser , Johansson Jan‐Olof , Rosenberg Wiebke , Stenborg Benny , Månsson Lars Gunnar , Båth Magnus
Published: February 2017

The purpose of the present study was to use a commercially available grayscale phantom to compare two ultrasound systems regarding their ability to reproduce clinically relevant low‐contrast objects at different sizes and depths, taking into account human observer variability and other methodological issues related to observer performance studies. One high‐end and one general ultrasound scanner from the same manufacturer using the same probe were included. The study was intended to simulate the clinical situation where small low‐contrast objects are embedded in relatively homogeneous organs. Images containing 4 and 6.4 mm objects of four different contrasts were acquired from the grayscale phantom at different depths. Six observers participated in a 4‐alternative forced‐choice study based on 960 images. Case sample and human observer variabilities were taken into account using bootstrapping. At four of sixteen depth/size/contrast combinations, the visual performance of the high‐end scanner was significantly higher. Thus, it was possible to use a grayscale phantom to discriminate between the two evaluated ultrasound systems in terms of their ability to reproduce clinically relevant low‐contrast objects. However, the number of images and number of observers were larger than those usually used for constancy control.

PACS number(s): 87.57.C‐, 87.63.dh
Investigation of dosimetric differences between the TMR 10 and convolution algorithm for Gamma Knife stereotactic radiosurgery
Authors: Rojas‐Villabona Alvaro , Kitchen Neil , Paddick Ian
Published: February 2017

Since its inception, doses applied using Gamma Knife Radiosurgery (GKR) have been calculated using a simple TMR algorithm, which assumes the patient's head is of even density, the same as water. This results in a significant approximation of the dose delivered by the Gamma Knife. We investigated how GKR dose calculations varied when using a new convolution algorithm clinically available for GKR planning that takes into account density variations in the head compared with the established calculation algorithm. Fifty‐five patients undergoing GKR and harboring 85 lesions were voluntarily and prospectively enrolled into the study. Their clinical treatment plans were created and delivered using TMR 10, but were then recalculated using the density correction algorithm. Dosimetric differences between the planning algorithms were noted. Beam on time (BOT), which is directly proportional to dose, was the main value investigated. Changes of mean and maximum dose to organs at risk (OAR) were also assessed. Phantom studies were performed to investigate the effect of frame and pin materials on dose calculation using the convolution algorithm. Convolution yielded a mean increase in BOT of 7.4% (3.6%–11.6%). However, approximately 1.5% of this amount was due to the head contour being derived from the CT scans, as opposed to measurements using the Skull Scaling Instrument with TMR. Dose to the cochlea calculated with the convolution algorithm was approximately 7% lower than with the TMR 10 algorithm. No significant difference in relative dose distribution was noted and CT artifact typically caused by the stereotactic frame, glue embolization material or different fixation pin materials did not systematically affect convolution isodoses. Nonetheless, substantial error was introduced to the convolution calculation in one target located exactly in the area of major CT artifact caused by a fixation pin. Inhomogeneity correction using the convolution algorithm results in a considerable, but consistent, dose shift compared to the TMR 10 algorithm traditionally used for GKR. A reduction of the prescription dose may be necessary to obtain the same clinical effect with the convolution algorithm. Head shape definition using CT outlining can reduce treatment uncertainty from head shape approximations.

PACS number(s): 87.53.‐j; 87.55.D; 87.55.kd
A dosimetric evaluation of knowledge‐based VMAT planning with simultaneous integrated boosting for rectal cancer patients
Authors: Wu Hao , Jiang Fan , Yue Haizhen , Li Sha , Zhang Yibao
Published: February 2017

RapidPlan, a commercial knowledge‐based optimizer, has been tested on head and neck, lung, esophageal, breast, liver, and prostate cancer patients. To appraise its performance on VMAT planning with simultaneous integrated boosting (SIB) for rectal cancer, this study configured a DVH (dose‐volume histogram) estimation model consisting 80 best‐effort manual cases of this type. Using the model‐ generated objectives, the MLC (multileaf collimator) sequences of other 70 clinically approved plans were reoptimized, while the remaining parameters, such as field geometry and photon energy, were maintained. Dosimetric outcomes were assessed by comparing homogeneity index (HI), conformal index (CI), hot spots (volumes receiving over 107% of the prescribed dose, ), mean dose and dose to the 50% volume of femoral head ( and ), and urinary bladder ( and ), and the mean DVH plotting. Paired samples t‐test or Wilcoxon signed‐rank test suggested that comparable CI were achieved by RapidPlan ( for , and for PTV) and original plans ( for and for PTV), respectively . Slightly improved HI of planning target volume and PTV were observed in the RapidPlan cases ( for , and for PTV) than the original plans ( for and for PTV), . More cases with positive were found in the original (18 plans) than the RapidPlan group (none). RapidPlan significantly reduced the (by from to ), (by from to G), (by from to ), and (by from to ), respectively. The more concentrated distribution of RapidPlan data points indicated an enhanced consistency of plan quality.

PACS number(s): 87.55.de; 87.55.dk
Validation of an improved helical diode array and dose reconstruction software using TG‐244 datasets and stringent dose comparison criteria
Authors: Ahmed Saeed , Nelms Benjamin , Kozelka Jakub , Zhang Geoffrey , Moros Eduardo , Feygelman Vladimir
Published: February 2017

The original helical ArcCHECK (AC) diode array and associated software for 3D measurement‐guided dose reconstruction were characterized and validated; however, recent design changes to the AC required that the subject be revisited. The most important AC change starting in 2014 was a significant reduction in the overresponse of diodes to scattered radiation outside of the direct beam, accomplished by reducing the amount of high‐Z materials adjacent to the diodes. This change improved the diode measurement accuracy, but in the process invalidated the dose reconstruction models that were assembled based on measured data acquired with the older version of the AC. A correction mechanism was introduced in the reconstruction software (3DVH) to accommodate this and potential future design changes without requiring updating model parameters. For each permutation of AC serial number and beam model, the user can define in 3DVH a single correction factor which will be used to compensate for the difference in the out‐of‐field response between the new and original AC designs. The exact value can be determined by minimizing the dose‐difference with an ionization chamber or another independent dosimeter. A single value of 1.17, corresponding to the maximum measured out‐of‐field response difference between the new and old AC, provided satisfactory results for all studied energies (6X, 15X, and flattening filter‐free 10XFFF). A library of standard cases recommended by the AAPM TG‐244 Report was used for reconstructed dose verification. The overall difference between reconstructed dose and an ion chamber in a water‐equivalent phantom in the targets was (1 SD). The reconstructed dose on a homogeneous phantom was also compared to a biplanar diode dosimeter () using gamma analysis with cutoff criteria. The mean agreement rate was . For the plans common with the previous comparison, the mean agreement rate was , essentially unchanged. We conclude that the proposed software modification adequately addresses the change in the dosimeter response.

PACS number(s): 87.55Qr
Dosimetric comparison of intensity‐modulated radiotherapy and volumetric‐modulated arc radiotherapy in patients with prostate cancer: a meta‐analysis
Authors: Ren Wenting , Sun Chao , Lu Ningning , Xu Yingjie , Han Fei , Ping Liu Yue , Dai Jianrong
Published: February 2017

Intensity‐modulated radiotherapy (IMRT) and volumetric‐modulated arc therapy (VMAT) are two main radiotherapy techniques. The aim of this study is to explore which is the preferred technique in prostate treatment through the related publications and meta‐analysis. Two authors independently identified all relevant articles available regarding eligibility criteria on PubMed, Embase, and Cochrane Library databases until December 2015. Publication bias was evaluated with funnel plot, and statistical analyses were performed with Stata software. was thought statistically significant. Ten studies comprised a total of 110 patients; in total 110 IMRT plans and 110 VMAT plans that were included in this study. V40, V60, and V70 of rectum were significantly decreased in VMAT than in IMRT. However, V50 of rectum and V40, V50, V60, V70 of bladder had no statistical differences between IMRI and VMAT plans. Compared with IMRT, the treatment time and MUs of VMAT were significantly lower. VMAT protects rectum better than IMRT and improves the delivery efficiency. VMAT may be the preferred modality for treating prostate cancer.

PACS number(s): 87.55. D‐
Prediction of jet mixing noise with Lighthill's Acoustic Analogy and geometrical acoustics
Authors: Ilário Carlos R. S. , Azarpeyvand Mahdi , Rosa Victor , Self Rod H. , Meneghini Júlio R.
Published: February 2017

A computational aeroacoustics prediction tool based on the application of Lighthill's theory is presented to compute noise from subsonic turbulent jets. The sources of sound are modeled by expressing Lighthill's source term as two-point correlations of the velocity fluctuations and the sound refraction effects are taken into account by a ray tracing methodology. Both the source and refraction models use the flow information collected from a solution of the Reynolds Averaged Navier-Stokes equations with a standard k-epsilon turbulence model. By adopting the ray tracing method to compute the refraction effects a high-frequency approximation is implied, while no assumption about the mean flow is needed, enabling the application of the method to jet noise problems with inherently three-dimensional propagation effects. Predictions show good agreement with narrowband measurements for the overall sound pressure levels and spectrum shape in polar angles between 60° and 110° for isothermal and hot jets with acoustic Mach number ranging from 0.5 to 1.0. The method presented herein can be applied as a relatively low cost and robust engineering tool for industrial optimization purposes.
In Vitro
Selection of Meropenem Resistance among Ceftazidime-Avibactam-Resistant, Meropenem-Susceptible Klebsiella pneumoniae Isolates with Variant KPC-3 Carbapenemases
Authors: Shields Ryan K. , Nguyen M. Hong , Press Ellen G. , Chen Liang , Kreiswirth Barry N. , Clancy Cornelius J.
Published: February 2017

Ceftazidime-avibactam resistance is mediated by
bla
KPC-3
mutations, which restore carbapenem susceptibility. We subjected
Klebsiella pneumoniae
isolates with different
bla
KPC-3
mutations (
n
= 5) or wild-type
bla
KPC-3
(
n
= 2) to serial passages with meropenem. The meropenem MIC against each isolate increased. Mutations in the
ompK36
porin gene evolved in 5 isolates. Among isolates with D179Y substitutions in KPC-3,
bla
KPC-3
mutations reverted to wild type, were replaced by new mutations, or were retained. Carbapenem treatment of ceftazidime-avibactam-resistant
K. pneumoniae
infections may select for carbapenem resistance.
GMP and IMP Are Competitive Inhibitors of CMY-10, an Extended-Spectrum Class C β-Lactamase
Authors: Na Jung-Hyun , An Young Jun , Cha Sun-Shin
Published: February 2017

Nucleotides were effective in inhibiting the class C β-lactamase CMY-10. IMP was the most potent competitive inhibitor, with a

K
i

value of 16.2 μM. The crystal structure of CMY-10 complexed with GMP or IMP revealed that nucleotides fit into the R2 subsite of the active site with a unique vertical binding mode where the phosphate group at one terminus is deeply bound in the subsite and the base at the other terminus faces the solvent.
Molecular Epidemiology of Colistin-Resistant, Carbapenemase-Producing Klebsiella pneumoniae in Serbia from 2013 to 2016
Authors: Novović Katarina , Trudić Anika , Brkić Snežana , Vasiljević Zorica , Kojić Milan , Medić Deana , Ćirković Ivana , Jovčić Branko
Published: February 2017

Twenty-seven colistin-resistant, carbapenemase-producing
Klebsiella pneumoniae
isolates were identified from hospitals in Serbia. All isolates were
bla
CTX-M-15
positive; ST101, ST888, ST437, ST336, and ST307 were
bla
OXA-48
positive; and ST340 was
bla
NDM-1
positive. ST307 had an insertion, and ST336 had a premature stop codon in the
mgrB
gene. Amino acid substitutions were detected in PmrAB of isolates ST101, ST888, ST336, and ST307. The
mcr-1
and
mcr-2
were not detected. An increase in
phoP
,
phoQ
, and
pmrK
gene transcription was detected for all sequence types.
A Farnesylated Coxiella burnetii Effector Forms a Multimeric Complex at the Mitochondrial Outer Membrane during Infection
Authors: Fielden Laura F. , Moffatt Jennifer H. , Kang Yilin , Baker Michael J. , Khoo Chen Ai , Roy Craig R. , Stojanovski Diana , Newton Hayley J.
Published: February 2017

Coxiella burnetii
, the causative agent of Q fever, establishes a unique lysosome-derived intracellular niche termed the
Coxiella
-containing vacuole (CCV). The Dot/Icm-type IVB secretion system is essential for the biogenesis of the CCV and the intracellular replication of
Coxiella
. Effector proteins, translocated into the host cell through this apparatus, act to modulate host trafficking and signaling processes to facilitate CCV development. Here we investigated the role of CBU0077, a conserved
Coxiella
effector that had previously been observed to localize to lysosomal membranes. CBU0077 was dispensable for the intracellular replication of
Coxiella
in HeLa and THP-1 cells and did not appear to participate in CCV biogenesis. Intriguingly, native and epitope-tagged CBU0077 produced by
Coxiella
displayed specific punctate localization at host cell mitochondria. As such, we designated CBU0077 MceA (
m
itochondrial

C

oxiella
e
ffector protein
A
). Analysis of ectopically expressed MceA truncations revealed that the capacity to traffic to mitochondria is encoded within the first 84 amino acids of this protein. MceA is farnesylated by the host cell; however, this does not impact mitochondrial localization. Examination of mitochondria isolated from infected cells revealed that MceA is specifically integrated into the mitochondrial outer membrane and forms a complex of approximately 120 kDa. Engineering
Coxiella
to express either MceA tagged with 3×FLAG or MceA tagged with 2×hemagglutinin allowed us to perform immunoprecipitation experiments that showed that MceA forms a homo-oligomeric species at the mitochondrial outer membrane during infection. This research reveals that mitochondria are a bona fide target of
Coxiella
effectors and MceA is a complex-forming effector at the mitochondrial outer membrane during
Coxiella
infection.
Tail-Anchored Inner Membrane Protein ElaB Increases Resistance to Stress While Reducing Persistence in Escherichia coli
Authors: Guo Yunxue , Liu Xiaoxiao , Li Baiyuan , Yao Jianyun , Wood Thomas K. , Wang Xiaoxue
Published: February 2017

Host-associated bacteria, such as
Escherichia coli
, often encounter various host-related stresses, such as nutritional deprivation, oxidative stress, and temperature shifts. There is growing interest in searching for small endogenous proteins that mediate stress responses. Here, we characterized the small C-tail-anchored inner membrane protein ElaB in
E. coli
. ElaB belongs to a class of tail-anchored inner membrane proteins with a C-terminal transmembrane domain but lacking an N-terminal signal sequence for membrane targeting. Proteins from this family have been shown to play vital roles, such as in membrane trafficking and apoptosis, in eukaryotes; however, their role in prokaryotes is largely unexplored. Here, we found that the transcription of
elaB
is induced in the stationary phase in
E. coli
and stationary-phase sigma factor RpoS regulates
elaB
transcription by binding to the promoter of
elaB
. Moreover, ElaB protects cells against oxidative stress and heat shock stress. However, unlike membrane peptide toxins TisB and GhoT, ElaB does not lead to cell death, and the deletion of
elaB
greatly increases persister cell formation. Therefore, we demonstrate that disruption of C-tail-anchored inner membrane proteins can reduce stress resistance; it can also lead to deleterious effects, such as increased persistence, in
E. coli
.

IMPORTANCE
Escherichia coli
synthesizes dozens of poorly understood small membrane proteins containing a predicted transmembrane domain. In this study, we characterized the function of the C-tail-anchored inner membrane protein ElaB in
E. coli
. ElaB increases resistance to oxidative stress and heat stress, while inactivation of ElaB leads to high persister cell formation. We also demonstrated that the transcription of
elaB
is under the direct regulation of stationary-phase sigma factor RpoS. Thus, our study reveals that small inner membrane proteins may have important cellular roles during the stress response.
Improving outcomes from high-risk surgery: a multimethod evaluation of a patient-centred advanced care planning intervention
Authors: Selwood Amanda , Senthuran Siva , Blakely Brette , Lane Paul , North John , Clay-Williams Robyn
Published: February 2017

Introduction

Patients who are frail, have multiple comorbidities or have a terminal illness often have poor outcomes from surgery. However, sole specialists may recommend surgery in these patients without consultation with other treating clinicians or allowing for patient goals. The Patient-Centred Advanced Care Planning (PC-ACP) model of care provides a framework in which a multidisciplinary advanced care plan is devised to incorporate high-risk patients' values and goals. Decision-making is performed collaboratively by patients, their family, surgeons, anaesthetists, intensivists and surgical case managers. This study aims to evaluate the feasibility of this new model of care, and to determine potential benefits to patients and clinicians.

Methods and analysis

After being assessed for frailty, patients will complete a patient–clinician information engagement survey pretreatment and at 6 months follow-up. Patients (and/or family members) will be interviewed about their experience of care pretreatment and at 3 and 6 months follow-ups. Clinicians will complete a survey on workplace attitudes and engagement both preimplementation and postimplementation of PC-ACP and be interviewed, following each survey, on the implementation of PC-ACP. We will use process mapping to map the patient journey through the surgical care pathway to determine areas of improvement and to identify variations in patient experience.

Ethics and dissemination

This study has received ethical approval from Townsville Hospital and Health Service HREC (HREC/16/QTHS/100). Results will be communicated to the participating hospital, presented at conferences and submitted for publication in a peer-reviewed MEDLINE-indexed journal.
Complementarity of resonant scalar, vector-like quark and superpartner searches in elucidating new phenomena
Authors: Biekötter Anke , Hewett JoAnne L. , Kim Jong Soo , Krämer Michael , Rizzo Thomas G. , Rolbiecki Krzysztof , Tattersall Jamie , Weber Torsten
Published: February 2017

The elucidation of the nature of new phenomena requires a multi-pronged approach to understand the essential physics that underlies it. As an example, we study the simplified model containing a new scalar singlet accompanied by vector-like quarks. To be specific, we investigate three models with [Formula: see text]-doublet, vector-like quarks with Yukawa couplings to a new scalar singlet and which also couple off-diagonally to corresponding Standard Model fermions of the first or third generation through the usual Higgs boson. We demonstrate that three classes of searches can play important and complementary roles in constraining this model. In particular, we find that missing energy searches designed for sparticle production, are also very sensitive to vector-like quarks.
Global stabilization of memristor-based fractional-order neural networks with delay via output-feedback control
Authors: Chen Jiyang , Li Chuandong , Huang Tingwen , Yang Xujun
Published: February 2017

In this paper, the memristor-based fractional-order neural networks (MFNN) with delay and with two types of stabilizing control are described in detail. Based on the Lyapunov direct method, the theories of set-value maps, differential inclusions and comparison principle, some sufficient conditions and assumptions for global stabilization of this neural network model are established. Finally, two numerical examples are presented to demonstrate the effectiveness and practicability of the obtained results.