bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of acquisition parameters on MV‐CBCT image quality
Authors: Gayou Olivier 
Published: February 2017

The production of high quality pretreatment images plays an increasing role in image‐guided radiotherapy (IGRT) and adaptive radiation therapy (ART). Megavoltage cone‐beam computed tomography (MV‐CBCT) is the simplest solution of all the commercially available volumetric imaging systems for localization. It also suffers the most from relatively poor contrast due to the energy range of the imaging photons. Several avenues can be investigated to improve MV‐CBCT image quality while maintaining an acceptable patient exposure: beam generation, detector technology, reconstruction parameters, and acquisition parameters. This article presents a study of the effects of the acquisition scan length and number of projections of a Siemens Artiste MV‐CBCT system on image quality within the range provided by the manufacturer. It also discusses other aspects not related to image quality one should consider when selecting an acquisition protocol. Noise and uniformity were measured on the image of a cylindrical water phantom. Spatial resolution was measured using the same phantom half filled with water to provide a sharp water/air interface to derive the modulation transfer function (MTF). Contrast‐to‐noise ratio (CNR) was measured on a pelvis‐shaped phantom with four inserts of different electron densities relative to water (1.043, 1.117, 1.513, and 0.459). Uniformity was independent of acquisition protocol. Noise decreased from 1.96% to 1.64% when the total number of projections was increased from 100 to 600 for a total exposure of 13.5 MU. The CNR showed dependence on the number of projections and 10% dependence on the scan length. However, these variations were not statistically significant. The spatial resolution was unaffected by the arc length or the sampling rate. Acquisition parameters have little to no effect on the image quality of the MV‐CBCT system within the range of parameters available on the system. Considerations other than image quality, such as memory storage, acquisition speed, and individual projection image quality, speak in favor of the use of a coarse sampling rate on the short scan.PACS numbers: 87.57.C‐; 87.57.nf
Calculating the peak skin dose resulting from fluoroscopically‐guided interventions. Part II: Case studies
Authors: Jones A. Kyle , Pasciak Alexander S. 
Published: February 2017

Part II of this review article presents four case studies for which peak skin doses are calculated following the methods outlined in Part I of this review. The data available in the cases ranges from proprietary dose reports to fluoroscopy time and number of digital acquisition frames only. Flowcharts are provided for each case. These flowcharts outline the calculation steps and data sources used to estimate the peak skin dose. The accuracy that can be achieved using these methods depends on several factors, including the calibration accuracy of dosimetric equipment, accuracy of information reported in the DICOM header and proprietary dose reports, accuracy of quantities measured by the medical physicist, and procedural factors such as rotation of the C‐arm during a fluoroscopically‐guided procedure.PACS numbers: 87.59.Dj, 87.53.Bn
Medical physics staffing for radiation oncology: a decade of experience in Ontario, Canada
Authors: Battista Jerry J. , Clark Brenda G. , Patterson Michael S. , Beaulieu Luc , Sharpe Michael B. , Schreiner L. John , MacPherson Miller S. , Van Dyk Jacob 
Published: February 2017

The January 2010 articles in The New York Times generated intense focus on patient safety in radiation treatment, with physics staffing identified frequently as a critical factor for consistent quality assurance. The purpose of this work is to review our experience with medical physics staffing, and to propose a transparent and flexible staffing algorithm for general use. Guided by documented times required per routine procedure, we have developed a robust algorithm to estimate physics staffing needs according to center‐specific workload for medical physicists and associated support staff, in a manner we believe is adaptable to an evolving radiotherapy practice. We calculate requirements for each staffing type based on caseload, equipment inventory, quality assurance, educational programs, and administration. Average per‐case staffing ratios were also determined for larger‐scale human resource planning and used to model staffing needs for Ontario, Canada over the next 10 years. The workload specific algorithm was tested through a survey of Canadian cancer centers. For center‐specific human resource planning, we propose a grid of coefficients addressing specific workload factors for each staff group. For larger scale forecasting of human resource requirements, values of 260, 700, 300, 600, 1200, and 2000 treated cases per full‐time equivalent (FTE) were determined for medical physicists, physics assistants, dosimetrists, electronics technologists, mechanical technologists, and information technology specialists, respectively.PACS numbers: 87.55.N‐, 87.55.Qr
Feasibility of a remote, automated daily delivery verification of volumetric‐modulated arc therapy treatments using a commercial record and verify system
Authors: Fontenot Jonas D. 
Published: February 2017

Volumetric‐modulated arc therapy (VMAT) is an effective but complex technique for delivering radiation therapy. VMAT relies on precise combinations of dose rate, gantry speed, and multileaf collimator (MLC) shapes to deliver intensity‐modulated patterns. Such complexity warrants the development of correspondingly robust performance verification systems. In this work, we report on a remote, automated software system for daily delivery verification of VMAT treatments. The performance verification software system consists of three main components: (1) a query module for retrieving daily MLC, gantry, and jaw positions reported by the linear accelerator control system to the record and verify system; (2) an analysis module which reads the daily delivery report generated from the database query module, compares the reported treatment positions against the planned positions, and compiles delivery position error reports; and (3) a graphical reporting module which displays reports initiated by a user anywhere within the institutional network or which can be configured to alert authorized users when predefined tolerance values are exceeded. The utility of the system was investigated through analysis of patient data collected at our clinic. Nearly 2500 VMAT fractions have been analyzed with the delivery verification system at our institution. The average percentage of reported MLC leaf positions within 3 mm, gantry positions within 2°, and jaw positions within 3 mm of their planned positions was , and , respectively. The level of agreement between planned and reported MLC positions decreased for treatment plans requiring larger MLC leaf movements between control points. Differences in the reported MLC position error between the delivery verification system and data extracted manually from the control system were noted; however, the differences are likely systematic and, therefore, may be characterized if appropriately accounted for. Further investigation is needed to confirm the utility and accuracy of the system.PACS numbers: 87.55.N‐, 87.55.T‐, 87.55.Qr
A semi‐empirical model for the therapeutic range shift estimation caused by inhomogeneities in proton beam therapy
Authors: Moskvin Vadim , Cheng Chee‐Wai , Fanelli Leia , Zhao Li , Das Indra J. 
Published: February 2017

The purpose of this study was to devise a simple semi‐empirical model to estimate the range shift in clinical practices with high‐Z inhomogeneity in proton beam. A semi‐empirical model utilizing the logarithmic dependence on Z in stopping power from Bohr's classical approach has been developed to calculate the range shift due to the presence of inhomogeneity. Range shift from metallic plates of atomic number Z of various thicknesses were measured in water using a parallel plate ionization chamber and calculated with the FLUKA Monte Carlo code. The proton range shifts for bone and polymethyl methacrylate (PMMA) were estimated using the semi‐empirical model and compared with Monte Carlo calculation. The semi‐empirical equation to determine range shift and water equivalent thickness is presented. The model predicts a shift of the therapeutic range to within 2.5% accuracy for initial proton energies of 50 to 250 MeV and atomic numbers from 3.3 (effective Z for water) to 82. This equation is independent of beam energy, and thus provides range shift from high‐Z materials without the knowledge of proton energy. The proposed method of calculating the therapeutic range shift accurately requires only knowledge of the effective or actual atomic number of the inhomogeneity and the thickness of the inhomogeneity along the beam direction. The model generalizes the range shift calculation for any material based on its effective atomic number, and permits reliable prediction of the range shift for material combinations where no data is currently available. The proposed model can be readily implemented in routine clinical practice for proton range shift estimation and quality assurance on the treatment planning.PACS numbers: 87.53.‐j, 87.55.‐x, 87.53.Bn, 87.55.D‐, 87.55.Qr, 87.55.K‐
The extent and serial pattern of interfractional variation in patients with whole pelvic irradiation: a study using a kilovoltage orthogonal on‐board imager
Authors: Yoon Won Sup , Yang Dae Sik , Lee Jung Ae , Lee Suk , Park Young Je , Kim Chul Yong 
Published: February 2017

The purpose of this study is to assess the extent and serial pattern of setup error of conventional fractionated whole pelvic irradiation using a kilovoltage on‐board imager. The daily on‐board images of 69 patients were matched with the digitally reconstructed radiographs of simulation on the basis of pelvic bony structure. The shifts along x‐ (lateral), y‐ (longitudinal), and z‐ (vertical) axes, and the 3D vector, were measured. The shift between an origin of the first fraction and each fraction and the shift between an isocenter of simulation and each fraction were calculated. To evaluate serial changes, the shifts of each fraction were classified into four consecutive sessions, and an ANOVA and chi‐square test were used. The systematic error of the and were 2.72 and 1.43 mm along the x‐axis, 2.98 and 1.28 mm along the y‐axis, and 4.26 and 2.39 mm along the z‐axis, respectively. The and of the 3D vector occurred in 54.3% and 23.1%, respectively. The recommended margins to cover setup error in case of using were 3.81, 3.54, and 6.01 mm along x‐, y‐, and z‐axes, whereas those using were 6.39, 6.95, and 9.95 mm, respectively. With the passage of time, the of 3D vector and along any axis in supine setup increased from 14.1% for first session to 22.5% for fourth session and from 10.8% to 18.5% , respectively. In prone setup, first session was better than others in the of 3D vector and along any axis. It is expected that the correction using the on‐board images on the first fraction improves geometrical uncertainties and reduces the margin for target coverage. Daily continuous OBI follow‐up during conventional fractionated pelvic irradiation can increase the reproducibility and be more effective in the late period.PACS number: 87.55.km
In vivo proton dosimetry using a MOSFET detector in an anthropomorphic phantom with tissue inhomogeneity
Authors: Kohno Ryosuke , Hotta Kenji , Matsubara Kana , Nishioka Shie , Matsuura Taeko , Kawashima Mitsuhiko 
Published: February 2017

When in vivo proton dosimetry is performed with a metal‐oxide semiconductor field‐effect transistor (MOSFET) detector, the response of the detector depends strongly on the linear energy transfer. The present study reports a practical method to correct the MOSFET response for linear energy transfer dependence by using a simplified Monte Carlo dose calculation method (SMC). A depth‐output curve for a mono‐energetic proton beam in polyethylene was measured with the MOSFET detector. This curve was used to calculate MOSFET output distributions with the SMC . The output value at an arbitrary point was compared with the value obtained by the conventional , which calculates proton dose distributions by using the depth‐dose curve determined by a parallel‐plate ionization chamber (PPIC). The ratio of the two values was used to calculate the correction factor of the MOSFET response at an arbitrary point. The dose obtained by the MOSFET detector was determined from the product of the correction factor and the MOSFET raw dose. When in vivo proton dosimetry was performed with the MOSFET detector in an anthropomorphic phantom, the corrected MOSFET doses agreed with the results within the measurement error. To our knowledge, this is the first report of successful in vivo proton dosimetry with a MOSFET detector.PACS number: 87.56.‐v
Analysis of the optimum internal margin for respiratory‐gated radiotherapy using end‐exhalation phase assessments using a motion phantom
Authors: Yaegashi Yuji , Tateoka Kunihiko , Nakazawa Takuya , Fujimoto Kazunori , Shima Katsumi , Suzuki Junji , Nakata Akihiro , Saito Yuichi , Abe Tadanori , Sakata Koichi , Hareyama Masato 
Published: February 2017

We aimed to optimize internal margin (IM) determination for respiratory‐gated radiotherapy using end‐expiratory phase assessments using a motion phantom. Four‐dimensional computed tomography (4D CT) data were acquired using a GE LightSpeed RT CT scanner, a respiratory‐gating system, and a motion phantom designed to move sinusoidally. To analyze the accuracy of 4D CT temporal resolution, a 25.4 mm diameter sphere was inserted into the motion phantom, and we measured the differences in sphere diameters between static and end‐exhalation phase images. In addition, the IM obtained from the maximum intensity projection within the gating window image was compared to theoretical value. Cranial–caudal motion displacement ranged from 5.0 to 30.0 mm, and the respiratory period ranged from 2.0 to 6.0 sec. Differences in sphere diameters between static and end‐exhalation phase images ranged from 0.37 to 4.6 mm, with 5.0 ‐mm and 30 mm target displacements, respectively. Differences between the IM obtained from the and the theoretical values ranged from 1.12 to 6.23 mm with 5.0 mm and 30 mm target displacements, respectively. These differences increased in proportion to the target velocity due to a motion artifact generated during tube rotation. In this study, the IMs obtained using the image were overestimated in all cases. We therefore propose that the internal target volume (ITV) for respiratory‐gated radiotherapy should be determined by adding the calculated value to the end‐exhalation phase image. We also demonstrate a methodology for subtracting motion artifacts from the ITV using a motion phantom.PACS numbers: 87.53.Kn, 87.55.Gh, 87.56.jk
Comparison of 16 mm OSU‐Nag and COMS eye plaques
Authors: Zhang Hualin , Davidorf Frederick , Qi Yujin 
Published: February 2017

OSU‐NAG eye plaques use fewer sources than COMS‐plaques of comparable size, and do not employ a Silastic seed carrier insert. Monte Carlo modeling was used to calculate 3D dose distributions for a 16 mm OSU‐NAG eye plaque and a 16 mm COMS eye plaque loaded with either Iodine‐125 or Cesium‐131 brachytherapy sources. The OSU‐NAG eye plaque was loaded with eight sources forming two squares, whereas the COMS eye plaque was loaded with thirteen sources approximating three isocentric circles. A spherical eyeball 24.6 mm in diameter and an ellipsoid‐like tumor 6 mm in height and 12 mm in the major and minor axes were used to evaluate the doses delivered. To establish a fair comparison, a water seed carrier was used instead of the Silastic seed carrier designed for the traditional COMS eye plaque. Calculations were performed on the dose distributions along the eye plaque axis and the DVHs of the tumor, as well as the 3D distribution. Our results indicated that, to achieve a prescription dose of 85 Gy at 6 mm from the inner sclera edge for a six‐day treatment, the OSU‐NAG eye plaque will need 6.16 U/source and 6.82 U/source for and , respectively. The COMS eye plaque will require 4.02 U/source and 4.43 U/source for the same source types. The dose profiles of the two types of eye plaques on their central axes are within 9% difference for all applicable distances. The OSU‐NAG plaque delivers about 10% and 12% more dose than the COMS for and sources, respectively, at the inner sclera edge, but 6% and 3% less dose at the opposite retina. The DVHs of the tumor for two types of plaques were within 6% difference. In conclusion, the dosimetric quality of the OSU‐NAG eye plaque used in eye plaque brachytherapy is comparable to the COMS eye plaque.PACS number: 87.56B, 87.55k, 87.55kh
Immobilization precision of a modified GTC frame
Authors: Winey Brian , Daartz Juliane , Dankers Frank , Bussière Marc 
Published: February 2017

The purpose of this study was to evaluate and quantify the interfraction reproducibility and intrafraction immobilization precision of a modified GTC frame. The error of the patient alignment and imaging systems were measured using a cranial skull phantom, with simulated, predetermined shifts. The kV setup images were acquired with a room‐mounted set of kV sources and panels. Calculated translations and rotations provided by the computer alignment software relying upon three implanted fiducials were compared to the known shifts, and the accuracy of the imaging and positioning systems was calculated. Orthogonal kV setup images for 45 proton SRT patients and 1002 fractions (average 22.3 fractions/patient) were analyzed for interfraction and intrafraction immobilization precision using a modified GTC frame. The modified frame employs a radiotransparent carbon cup and molded pillow to allow for more treatment angles from posterior directions for cranial lesions. Patients and the phantom were aligned with three 1.5 mm stainless steel fiducials implanted into the skull. The accuracy and variance of the patient positioning and imaging systems were measured to be , with the maximum uncertainty of rotation being pairs of interfraction image sets and 974 intrafraction image sets were analyzed. 3D translations and rotations were recorded. The 3D vector interfraction setup reproducibility was 0.13 mm for translations and the largest uncertainty of for rotations. The intrafraction immobilization efficacy was 0.19 mm for translations and the largest uncertainty of for rotations. The modified GTC frame provides reproducible setup and effective intrafraction immobilization, while allowing for the complete range of entrance angles from the posterior direction.PACS number: 87.53.Ly, 87.55.Qr
Target localization using scanner‐acquired SPECT data
Authors: Roper Justin R. , Bowsher James E. , Wilson Joshua M. , Turkington Timothy G. , Yin Fang‐Fang 
Published: February 2017

Target localization using single photon emission computed tomography (SPECT) and planar imaging is being investigated for guiding radiation therapy delivery. Previous studies on SPECT‐based localization have used computer‐simulated or hybrid images with simulated tumors embedded in disease‐free patient images where the tumor position is known and localization can be calculated directly. In the current study, localization was studied using scanner‐acquired images. Five fillable spheres were placed in a whole body phantom. Sphere‐to‐background radioactivity was 6:1. Ten independent SPECT scans were acquired with a Trionix Triad scanner using three detector trajectories: left lateral 180°, 360°, and right lateral 180°. Scan time was equivalent to 4.5 min. Images were reconstructed with and without attenuation correction. True target locations were estimated from 12 hr SPECT and CT images. From the 12 hr SPECT scan, 45 sets of orthogonal planar images were used to assess target localization; total acquisition time per set was equivalent to 4.5 min. A numerical observer localized the center of the targets in the 4.5 min SPECT and planar images. SPECT‐based localization errors were compared for the different detector trajectories. Across the four peripheral spheres, and using optimal iteration numbers and postreconstruction smoothing, means and standard deviations in localization errors were for proximal 180° trajectories, for 360° orbits, and for distal 180° trajectories. This rank order in localization performance is predicted by target attenuation and distance from the target to the collimator. For the targets with mean localization errors , attenuation correction reduced localization errors by 0.15 mm on average. The improvement from attenuation correction was 1.0 mm on average for the more poorly localized targets. Attenuation correction typically reduced localization errors, but for well‐localized targets, the detector trajectory generally had a larger effect. Localization performance was found to be robust to iteration number and smoothing. Localization was generally worse using planar images as compared with proximal 180° and 360° SPECT scans. Using a proximal detector trajectory and attenuation correction, localization errors were within 2 mm for the three superficial targets, thus supporting the current role in biopsy and surgery, and demonstrating the potential for SPECT imaging inside radiation therapy treatment rooms.PACS numbers: 87.55.Gh, 87.57.qp, 87.57.uh
Study of ExacTrac X‐ray 6D IGRT setup uncertainty for marker‐based prostate IMRT treatment
Authors: Shi Chengyu , Tazi Adam , Fang Deborah Xiangdong , Iannuzzi Christopher 
Published: February 2017

Novalis Tx ExacTrac X‐ray system has the 6D adjustment ability for patient setup. Limited studies exist about the setup uncertainty with ExacTrac X‐ray system for IMRT prostate treatment with fiducial markers implanted. The purpose of this study is to investigate the marker‐based prostate IMRT treatment setup uncertainty using ExacTrac 6D IGRT ability for patient setup. Forty‐three patients with prostate cancers and markers implanted have been treated on the Novalis Tx machine. The ExacTrac X‐ray system has been used for the patient pretreatment setup and intratreatment verification. In total, the shifts data for 1261 fractions and 3504 correction times (the numbers of X‐ray images were taken from tube 1 and tube 2) have been analyzed. The setup uncertainty has been separated into uncertainties in 6D. Marker matching uncertainty was also analyzed. Correction frequency probability density function was plotted, and the radiation dose for imaging was calculated. The minimum, average, and maximum translation shifts were: , , and , respectively, in the lateral direction; , , and , respectively, in the longitudinal direction; and , , and , respectively, in the vertical direction. The minimum, average, and maximum rotation shifts were: , , and , respectively, along lateral direction; , , and , respectively, along longitudinal direction; and , , and , respectively, along vertical direction. On average, each patient had three correction times during one fraction treatment. The radiation dose is about 3 mSv per fraction. With the ExacTrac 6D X‐ray system, the prostate IMRT treatment with marker implanted can achieve less than 2 mm setup uncertainty in translations, and less than 0.25° in rotations as overall interfraction mean error. The imaging dose is less than kV (CBCT) for setup verification.PACS number: 87.55.km, 87.55.Qr, 87.56.bd