bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of serrated gold coil markers in prostate localization
Authors: Gates Larry L. , Gladstone David J. , Kasibhatla Mohit S. , Marshall John F. , Seigne John D. , Hug Eugen , Hartford Alan C. 
Published: February 2017

We investigated the stability of serrated gold coils (Visicoil) implanted within the prostate glands of patients undergoing definitive external beam radiotherapy for prostate cancer. Radiopaque Visicoils of diameter 0.75 mm and median length 3 cm (range 2–4 cm) were implanted, one into each lobe of the prostate glands of 30 patients planned for external beam treatment. The coils were visualized on CT simulation and again after 25 fractions of treatment (5WK). Data from 30 patients were studied, of whom 19 also received androgen ablation therapy. The average change in the distance between the two coils over five weeks of treatment was 0.8 mm , with a maximum of 2.5 mm in one patient. Average residual errors (standard deviations) for the positions of individual coil segments after five weeks of therapy were only 0.7 mm LAT, 0.6 mm AP, and 0.4 mm SI. The average change in distance between the coils over five weeks compared favorably with published data regarding marker seed stability. Overall, less than a 2 mm margin (i.e., 2 standard deviations) would adequately compensate for positioning uncertainty of the coils in more than 95% of cases.PACS number: 87.55.kh
Characterization of linear accelerator X‐ray source size using a laminated beam‐spot camera
Authors: Yeboah Collins 
Published: February 2017

A laminated beam‐spot camera of length 20 cm and effective cross‐sectional area was designed and constructed for the measurement of X‐ray beam‐spot sizes on different models of Siemens accelerators. With the accelerator gantry at 180° and camera positioned on an accessory tray holder, an XV film placed in contact with the camera at the distal end of it detected those X‐rays that were transmitted through the camera. The FWHM of the detected X‐ray intensity profile in the gun–target (G–T) direction or the orthogonal A–B direction was used as a measure of the beam‐spot size in that direction. Siemens Mevatron MXEs exhibited a beam‐spot size of 1.7 in both the in‐plane and cross‐plane directions for 6 MV photon beams. The beam‐spot size observed for a Mevatron MDX‐2 was larger by up to 1 mm, and also was different for the in‐plane and cross‐plane directions. For Siemens PRIMUS accelerators, the beam‐spot size in the in‐plane direction was found to fall in the range , whereas the beam‐spot size in the cross‐plane direction fell within for 6, 10, and 18 MV photon beams. Assessment of long‐term stability of the beam‐spot size shows the spot size remains fairly stable over time.PACS number: 87.56.B‐, 87.56.bd
Characterization of dose impact on IMRT and VMAT from couch attenuation for two Varian couches
Authors: Li Heng , Lee Andrew K. , Johnson Jennifer L. , Zhu Ronald X. , Kudchadker Rajat J. 
Published: February 2017

In intensity‐modulated radiation therapy (IMRT) and volumetric‐modulated arc therapy (VMAT), the use of posterior oblique beams has become common. Beam attenuation by the treatment couch is not negligible when the couch is in the beam portal. In this study, we established the relationship of relative dose vs. beam angle for two Varian 21EX linacs, one equipped with the Exact couch (standard couch) with sliding side support rails, and the other equipped with the Exact image‐guided radiation therapy (IGRT) carbon fiber couch. Measurements were performed using an ion chamber placed at the center of an acrylic cylindrical phantom positioned at the linac isocenter for 6 MV and 18 MV photon beams. Measurements were performed at three different field sizes , and , and were repeated with the phantom positioned at different longitudinal locations on the couches. To evaluate beam attenuation by the standard couch in a clinical setting, two test IMRT plans and two test VMAT plans on the standard couch were delivered. The plans were generated with the sliding rails at the “in” position and delivered with the rails at both “in” and “out” positions. The dose difference to the ion chamber was determined. For oblique fields with 6 MV photons, the standard couch attenuated the radiation beam by up to 26.8%, while the carbon fiber IGRT couch attenuated the beam by up to 4.1%. In the clinical evaluation, the highest dose difference between rails set at the “in” and “out” positions was 2.6% in the IMRT case and 2.1% in the VMAT case. The magnitude of potential dose difference has been quantified and could be used for a quick estimation of dose difference due to couch attenuation in IMRT and VMAT.PACS number: 87.56.‐v
Impact of the vaginal applicator and dummy pellets on the dosimetry parameters of Cs‐137 brachytherapy source
Authors: Sina Sedigheh , Faghihi Reza , Meigooni Ali S. , Mehdizadeh Simin , Shirazi M. Amin Mosleh , Zehtabian Mehdi 
Published: February 2017

In this study, dose rate distribution around a spherical pellet source, from a low‐dose‐rate (LDR) Selectron remote afterloading system used in gynecological brachytherapy, has been determined using experimental and Monte Carlo simulation techniques. Monte Carlo simulations were performed using MCNP4C code, for a single pellet source in water medium and Plexiglas, and measurements were performed in Plexiglas phantom material using LiF TLD chips. Absolute dose rate distribution and the dosimetric parameters, such as dose rate constant, radial dose functions, and anisotropy functions, were obtained for a single pellet source. In order to investigate the effect of the applicator and surrounding pellets on dosimetric parameters of the source, the simulations were repeated for six different arrangements with a single active source and five non‐active pellets inside central metallic tubing of a vaginal cylindrical applicator. In commercial treatment planning systems (TPS), the attenuation effects of the applicator and inactive spacers on total dose are neglected. The results indicate that this effect could lead to overestimation of the calculated F(r,θ), by up to 7% along the longitudinal axis of the applicator, especially beyond the applicator tip. According to the results obtained in this study, in a real situation in treatment of patients using cylindrical vaginal applicator and using several active pellets, there will be a large discrepancy between the result of superposition and Monte Carlo simulations.PACS number: 87.53.Jw
Detection of patient setup errors with a portal image – DRR registration software application
Authors: Sutherland Kenneth , Ishikawa Masayori , Bengua Gerard , Ito Yoichi M. , Miyamoto Yoshiko , Shirato Hiroki 
Published: February 2017

The purpose of this study was to evaluate a custom portal image — digitally reconstructed radiograph (DRR) registration software application. The software works by transforming the portal image into the coordinate space of the DRR image using three control points placed on each image by the user, and displaying the fused image. In order to test statistically that the software actually improves setup error estimation, an intra‐ and interobserver phantom study was performed. Portal images of anthropomorphic thoracic and pelvis phantoms with virtually placed irradiation fields at known setup errors were prepared. A group of five doctors was first asked to estimate the setup errors by examining the portal and DRR image side‐by‐side, not using the software. A second group of four technicians then estimated the same set of images using the registration software. These two groups of human subjects were then compared with an auto‐registration feature of the software, which is based on the mutual information between the portal and DRR images. For the thoracic case, the average distance between the actual setup error and the estimated error was for doctors using the side‐by‐side method, for technicians using the registration method, and for the automatic algorithm. For the pelvis case, the average distance between the actual setup error and estimated error was for the doctors using the side‐by‐side method, for technicians using the registration method, and for the automatic algorithm. The ability of humans to estimate offset values improved statistically using our software for the chest phantom that we tested. Setup error estimation was further improved using our automatic error estimation algorithm. Estimations were not statistically different for the pelvis case. Consistency improved using the software for both the chest and pelvis phantoms. We also tested the automatic algorithm with a database of over 5,000 clinical cases from our hospital. The algorithm performed well for head and breast but performed poorly for pelvis cases, probably due to lack of contrast in the megavoltage portal image. The software incorporates an original algorithm to fuse portal and DRR images, which we describe in detail. The offset optimization algorithm used in the automatic mode of operation is also unique, and may be useful if the contrast of the portal images can be improved.PACS numbers: 87.55.Qr, 87.57.nj
Evaluation of tomotherapy MVCT image enhancement program for tumor volume delineation
Authors: Martin Spencer , Rodrigues George , Chen Quan , Pavamani Simon , Read Nancy , Ahmad Belal , Hammond J. Alex , Venkatesan Varagur , Renaud James , Yartsev Slav 
Published: February 2017

The aims of this study were to investigate the variability between physicians in delineation of head and neck tumors on original tomotherapy megavoltage CT (MVCT) studies and corresponding software enhanced MVCT images, and to establish an optimal approach for evaluation of image improvement. Five physicians contoured the gross tumor volume (GTV) for three head and neck cancer patients on 34 original and enhanced MVCT studies. Variation between original and enhanced MVCT studies was quantified by DICE coefficient and the coefficient of variance. Based on volume of agreement between physicians, higher correlation in terms of average DICE coefficients was observed in GTV delineation for enhanced MVCT for patients 1, 2, and 3 by 15%, 3%, and 7%, respectively, while delineation variance among physicians was reduced using enhanced MVCT for 12 of 17 weekly image studies. Enhanced MVCT provides advantages in reduction of variance among physicians in delineation of the GTV. Agreement on contouring by the same physician on both original and enhanced MVCT was equally high.PACS numbers: 87.57.N‐, 87.57.np, 87.57.nt
The impact of uncertainties associated with MammoSite brachytherapy on the dose distribution in the breast
Authors: Bensaleh Saleh , Bezak Eva 
Published: February 2017

The MammoSite radiation therapy system is a novel technique for treatment of patients with early‐stage breast cancer. It was developed to overcome the longer schedules associated with external‐beam radiation therapy. It consists of a small balloon (4 cm in diameter) connected to an inflation channel and a catheter for the passage of a high dose ratebrachytherapy source. The device is placed into the tumor resection cavity and inflated with a mixture of saline and radiographic contrast agent to a size that fills the cavity. A high dose ratesource is driven into the balloon center using a remote afterloader to deliver the prescribed dose at a point 1 cm away from the balloon surface. There are several uncertainties that affect the dose distribution in the MammoSite brachytherapy. They include source position deviation, balloon deformation, and the concentration of the contrast medium inside the balloon. The purpose of this study is to investigate the extent of the dose perturbation for various concentrations of the contrast medium in a MammoSite balloon using Monte Carlo simulations and thermoluminescent dosimetry. This study also combines the impact of these uncertainties on the MammoSite treatment efficacy. The current study demonstrates that the combined uncertainties associated with the MammoSite brachytherapy technique — up to the value of 2 mm balloon deformation, 1 mm source deviation, and 15% contrast concentration — have no impact on the tumor control probability.PACS number: 87.53.‐j
Development and applicability of a quality control phantom for dental cone‐beam CT
Authors: Pauwels Ruben , Stamatakis Harry , Manousaridis Giorgos , Walker Adrian , Michielsen Koen , Bosmans Hilde , Bogaerts Ria , Jacobs Reinhilde , Horner Keith , Tsiklakis Kostas ,   The SEDENTEXCT Project Consortium
Published: February 2017

Cone‐beam CT (CBCT) has shown to be a useful imaging modality for various dentomaxillofacial applications. However, optimization and quality control of dental CBCT devices is hampered due to the lack of an appropriate tool for image quality assessment. To investigate the application of different image quality parameters for CBCT, a prototype polymethyl methacrylate (PMMA) cylindrical phantom with inserts for image quality analysis was developed. Applicability and reproducibility of the phantom were assessed using seven CBCT devices with different scanning protocols. Image quality parameters evaluated were: CT number correlation, contrast resolution, image homogeneity and uniformity, point spread function, and metal artifacts. Deviations of repeated measurements were between 0.0% and 3.3%. Correlation coefficients of CBCT voxel values with CT numbers ranged between 0.68 and 1.00. Contrast‐to‐noise ratio (CNR) values were much lower for hydroxyapatite than for air and aluminum . Noise values ranged between 35 and 419. The uniformity index was between 3.3% and 11.9%. Full width at half maximum (FWHM) measurements varied between 0.43 mm and 1.07 mm. The increase of mean voxel values surrounding metal objects ranged between 6.7% and 43.0%. Results from preliminary analyses of the prototype quality control phantom showed its potential for routine quality assurance on CBCT. Large differences in image quality performance were seen between CBCT devices. Based on the initial evaluations, the phantom can be optimized and validated.PACS numbers: 87.57.C‐, 87.57.N‐, 87.57.Q‐
Dependence of intrafraction motion on fraction duration for pediatric patients with brain tumors
Authors: Beltran Chris , Merchant Thomas E. 
Published: February 2017

The purpose of this study was to quantify the intrafraction motion of pediatric patients with brain tumors during radiation therapy and investigate any correlation between motion, use of general anesthesia, and daily treatment duration. 100 pediatric patients with a mean age of 8.5 years (range: 1.0 to 17.8) were included in this prospective study. Forty‐one patients required general anesthesia during treatment, mean age 4.8 years; 59 patients did not, mean age 11.2 years. Each patient had an intracranial tumor and was treated in the supine position with a thermoplastic facemask and headrest for immobilization. A pretreatment localization CBCT was acquired for each treatment fraction and a post‐treatment CBCT was acquired every other fraction. If the magnitude of the patient's position pre‐CBCT offset was , the position was corrected. The difference between the patient's position based on the post‐CBCT and the assumed position at the start of treatment (either the pre‐CBCT offset if the magnitude was , or 0 offset due to correction) was determined and labeled intrafraction motion. Correlations between daily treatment duration and intrafraction motion were examined. There was an average of 14.2 post‐CBCTs acquired per patient. The magnitude of the mean intrafraction motion was for patients requiring general anesthesia, and for those without . The mean offset in each direction was less than 0.5 mm for both cohorts. There was no correlation between daily treatment duration and the magnitude of intrafraction motion. The intrafraction motion of pediatric patients undergoing external beam therapy for intracranial tumors is small, , and is independent of the daily treatment duration.PACS number: 87.53.Jw
Establishing the quality management baseline in the use of computed tomography machines in Kenya
Authors: Korir Geoffrey K. , Wambani Jeska S. , Korir Ian K. , Ochieng Bernard O. 
Published: February 2017

The objective of this study was to assess the level of compliance to quality assurance and image quality standards in computed tomography facilities in Kenyan hospitals. A quality assurance inspection and physical image quality assessment in eighteen representative computed tomography facilities were completed. A quantitative method was developed and used to score the results obtained from the physical image quality measurements using the American Association of Physicists in Medicine (AAPM) water phantom. Inspection was done in order to establish the level of compliance with internationally recognized standards such as those stipulated in the European Guidelines Quality Criteria for Computed Tomography and the International Basic Safety Standards for Protection against Ionizing Radiation. The overall findings placed the national quality management performance at , while image quality and quality assurance performance were and , respectively. The quality assurance assessment benchmarked the country's level of quality management system compliance in diagnostic radiology. During accreditation appraisal, the scrutiny of scores from each stage in the medical imaging chain per facility will encourage continual implementation of the quality improvement process.PACS number: 87.57.C, 87.57.cf, 87.57.cj, 87.57.cm, 87.57.cp, 87.57.Q, 87.55.N
Dosimetric characteristics of the small diameter BrainLab™ cones used for stereotactic radiosurgery
Authors: Khelashvili Gocha , Chu James , Diaz Aidnag , Turian Julius 
Published: February 2017

The purpose was to study the dosimetric characteristics of the small diameter () BrainLAB cones used for stereotactic radiosurgery (SRS) treatments in conjunction with a Varian Trilogy accelerator. Required accuracy and precision in dose delivery during SRS can be achieved only when the geometric and dosimetric characteristics of the small radiation fields is completely understood. Although a number of investigators have published the dosimetric characteristics of SRS cones, to our knowledge, there is no generally accepted value for the relative output factor (ROF) for the 5.0 mm diameter cone. Therefore, we have investigated the dosimetric properties of the small () diameter BrainLAB SRS cones used in conjunction with the iPlan TPS and a Trilogy linear accelerator with a SRS beam mode. Percentage depth dose (PDD), off‐axis ratios (OAR), and ROF were measured using a SRS diode and verified with Monte Carlo (MC) simulations. The dependence of ROF on detector material response was studied. The dependence of PDD, OAR, and ROF on the alignment of the beam CAX with the detector motion line was also investigated using MC simulations. An agreement of 1% and 1 mm was observed between measurements and MC for PDD and OAR. The calculated ROF for the 5.0 mm diameter cone was — in good agreement with the measured value of after the diode response was corrected. Simulations of the misalignment between the beam axis and detector motion axis for angles between 0.5°–1.0° have shown a deviation > 2% in PDD beyond a certain depth. We have also provided a full set of dosimetric data for BrainLAB SRS cones. Monte Carlo calculated ROF values for cones with diameters less than 10.0 mm agrees with measured values to within 1.8%. Care should be exercised when measuring PDD and OAR for small cones. We recommend the use of MC to confirm the measurement under these conditions.PACS numbers: 87.53.Ly, 87.55.‐x, 87.53.Bn, 87.55.K‐
Effects of dose scaling on delivery quality assurance in tomotherapy
Authors: Whitmore Nathan , Nalichowski Adrian , Burmeister Jay 
Published: February 2017

Delivery quality assurance (DQA) of tomotherapy plans is routinely performed with silver halide film which has a limited range due to the effects of saturation. DQA plans with dose values exceeding this limit require the dose of the entire plan to be scaled downward if film is used, to evaluate the dose distribution in two dimensions. The potential loss of fidelity between scaled and unscaled DQA plans as a function of dose scaling is investigated. Three treatment plans for 12 Gy fractions designed for SBRT of the lung were used to create DQA procedures that were scaled between 100% and 10%. The dose was measured with an ionization chamber array and compared to values from the tomotherapy treatment planning system. Film and cylindrical ion chamber measurements were also made for one patient for scaling factors of 50% to 10% to compare with the ionization chamber array measurements. The array results show the average gamma pass rate is from 100% to 30% scaling. The average gamma pass rate falls to 93.6% and 51.1% at 20% and 10% scaling, respectively. Film analysis yields similar pass rates. Cylindrical ion chambers did not exhibit significant variation with dose scaling, but only represent points in the low gradient region of the dose distribution. Scaling the dose changes the mechanics of the radiation delivery, as well as the signal‐to‐noise ratio. Treatment plans which exhibit parameters that differ significantly from those common to DQA plans studied in this paper may exhibit different behavior. Dose scaling should be limited to the smallest degree possible. Planar information, such as that from film or a detector array, is required. The results show that it is not necessary to perform both a scaled and unscaled DQA plan for the treatment plans considered here.PACS numbers: 87.55.km, 87.55.Qr
Anatomy driven optimization strategy for total marrow irradiation with a volumetric modulated arc therapy technique
Authors: Mancosu Pietro , Navarria Pierina , Castagna Luca , Roggio Antonella , Pellegrini Chiara , Reggiori Giacomo , Fogliata Antonella , Lobefalo Francesca , Castiglioni Simona , Alongi Filippo , Cozzi Luca , Santoro Armando , Scorsetti Marta 
Published: February 2017

The purpose of this study was to evaluate the possibility of dose distribution optimization for total marrow irradiation (TMI) employing volumetric‐modulated arc therapy (VMAT) with RapidArc (RA) technology setting isocenter's positions and jaw's apertures according to patient's anatomical features. Plans for five patients were generated with the RA engine (PROIII): eight arcs were distributed along four isocenters and simultaneously optimized with collimator set to 90°. Two models were investigated for geometrical settings of arcs: (1) in the “symmetric” model, isocenters were equispaced and field apertures were set the same for all arcs to uniformly cover the entire target length; (2) in the “anatomy driven” model, both field sizes and isocenter positions were optimized in order to minimize the target volume near the field edges (i.e., to maximize the freedom of motion of MLC leaves inside the field aperture (for example, avoiding arcs with ribs and iliac wings in the same BEV)). All body bones from the cranium to mid of the femurs were defined as PTV; the maximum length achieved in this study was 130 cm. Twelve (12) Gy in 2 Gy/fractions were prescribed in order to obtain the covering of 85% of the PTV by 100% of the prescribed dose. For all organs at risk (including brain, optical structures, oral and neck structures, lungs, heart, liver, kidneys, spleen, bowels, bladder, rectum, genitals), planning strategy aimed to maximize sparing according to ALARA principles, looking to reach a mean dose lower than 6 Gy (i.e., 50% of the prescribed dose). Mean MU/fraction resulted and for the two strategies, corresponding to a reduction of 7% (range to 13%) for (1) and (2). Target homogeneity, defined as was 18% better for (2). Mean dose to the healthy tissue, defined as body minus PTV, had 10% better reduction with (2). The isocenter's position and the jaw's apertures are significant parameters in the optimization of the TMI with RA technique, giving the medical physicist a crucial role in driving the optimization and thus obtaining the best plan. A clinical protocol started in our department in October 2010.PACS numbers: 87.55.de, 87.55.dk, 87.56.nk, 87.57.uq