bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of patient dose and optimization levels in chest and abdomen CR examinations at referral hospitals in Tanzania
Authors: Masoud A. O. , Muhogora W.E. , Msaki P.K. 
Published: February 2017

The aim of this study was to evaluate the radiation doses to patient during chest and abdomen CR examinations, and assess the related level of optimization at five referral hospitals in Tanzania. The international code of practice for dosimetry in diagnostic radiology was applied to determine the entrance surface air kerma (ESAK) to patients. The level of optimization was assessed from low‐contrast objects scores of phantom images at different exposures. The results show that mean ESAK varied from 0.16 to 0.37 mGy for chest PA and from 2 to 6 mGy for abdomen AP. Assuming similar patient and phantom attenuations, the optimization performed at all facilities was consistent with phantom evaluations in terms of tube potential settings in use. However, all facilities seemed to operate at higher tube load values above 5 mAs for chest examination, which can lead to unnecessary patient doses. Inadequate initial training on CR technology explains in large proportion the inappropriate use of exposure parameters.PACS numbers: 87.50.up, 87.59bd
Fractionated SRT using VMAT and Gamma Knife for brain metastases and gliomas — a planning study
Authors: Huss Marie , Barsoum Pierre , Dodoo Ernest , Sinclair Georges , Toma‐Dasu Iuliana 
Published: February 2017

Stereotactic radiosurgery using Gamma Knife (GK) or linear accelerators has been used for decades to treat brain tumors in one fraction. A new positioning system, Extend™, was introduced by Elekta AB for fractionated stereotactic radiotherapy (SRT) with GK. Another option for fractionated SRT is advanced planning and delivery using linacs and volumetric modulated arc therapy (VMAT). This project aims to assess the performance of GK Extend™ for delivering fractionated SRT by comparing GK treatments plans for brain targets performed using Leksell GammaPlan (LGP) with VMAT treatment plans. Several targets were considered for the planning: simulated metastasis‐ and glioma‐like targets surrounding an organ at risk (OAR), as well as three clinical cases of metastases. Physical parameters such as conformity, gradient index, dose to OARs, and brain volume receiving doses above the threshold associated with risk of damaging healthy tissue, were determined and compared for the treatment plans. The results showed that GK produced better dose distributions for target volumes below 15 cm3, while VMAT results in better dose conformity to the target and lower doses to the OARs in case of fractionated treatments for large or irregular volumes. The volume receiving doses above a threshold associated with increased risk of damage to normal brain tissue was also smaller for VMAT. The GK consistently performed better than VMAT in producing a lower dose‐bath to the brain. The above is subjected only to margin‐dependent fractionated radiotherapy (CTV/PTV). The results of this study could lead to clinically significant decisions regarding the choice of the radiotherapy technique for brain targets.PACS numbers: 87.53.Ly, 87.55.D‐
Automated Verification of IGRT‐based Patient Positioning
Authors: Jiang Xiaojun , Fox Tim , Cordova James S. , Schreibmann Eduard 
Published: February 2017

A system for automated quality assurance in radiotherapy of a therapist's registration was designed and tested in clinical practice. The approach compliments the clinical software's automated registration in terms of algorithm configuration and performance, and constitutes a practical approach for ensuring safe patient setups. Per our convergence analysis, evolutionary algorithms perform better in finding the global optima of the cost function with discrepancies from a deterministic optimizer seen sporadically.PACS number(s): 87.55.Qr, 87.55.T, 87.55.N
Contralateral breast dose from partial breast brachytherapy
Authors: Robinson R. Cole , Nelson Christopher L. , Bloom Elizabeth S. , Kisling Kelly D. , Mason Bryan E. , Fisher Gary D. , Kirsner Steven M. 
Published: February 2017

The purpose of this study was to determine the dose to the contralateral breast during accelerated partial breast irradiation (APBI) and to compare it to external beam‐published values. Thermoluminescent dosimeter (TLD) packets were used to measure the dose to the most medial aspect of the contralateral breast during APBI simulation, daily quality assurance (QA), and treatment. All patients in this study were treated with a single‐entry, multicatheter device for 10 fractions to a total dose of 34 Gy. A mark was placed on the patient's skin on the medial aspect of the opposite breast. Three TLD packets were taped to this mark during the pretreatment simulation. Simulations consisted of an AP and Lateral scout and a limited axial scan encompassing the lumpectomy cavity (miniscan), if rotation was a concern. After the simulation the TLD packets were removed and the patients were moved to the high‐dose‐rate (HDR) vault where three new TLD packets were taped onto the patients at the skin mark. Treatment was administered with a Nucletron HDR afterloader using Iridium‐192 as the treatment source. Post‐treatment, TLDs were read (along with the simulation and QA TLD and a set of standards exposed to a known dose of 6 MV photons). Measurements indicate an average total dose to the contralateral breast of 70 cGy for outer quadrant implants and 181 cGy for inner quadrant implants. Compared to external beam breast tangents, these results point to less dose being delivered to the contralateral breast when using APBI.PACS number: 87.55.D‐
Dosimetric verification and quality assurance of running‐start‐stop (RSS) delivery in tomotherapy
Authors: Lee Francis Kar‐ho , Chan Simon Kar‐yiu , Chau Ricky Ming‐chun 
Published: February 2017

The purpose of this study was to evaluate the dosimetric profiles and delivery accuracy of running‐start‐stop (RSS) delivery in tomotherapy and to present initial quality assurance (QA) results on the accuracy of the dynamic jaw motion, dosimetric penumbrae of the RSS dynamic jaw and the static jaw were measured by radiographic films. Delivery accuracy of the RSS was evaluated by gamma analysis on film measurements of 12 phantom plans. Consistency in the performance of RSS was evaluated by QA procedures over the first nine months after the installation of the feature. These QA were devised to check: 1) positional accuracy of moving jaws; 2) consistency of relative radiation output collimated by discrete and continuously sweeping jaws; 3) consistency of field widths and profiles. In the longitudinal direction, the dose penumbra in RSS delivery was reduced from 17.3 mm to 10.2 mm for 2.5 cm jaw, and from 33.2 mm to 9.6 mm for 5 cm jaw. Gamma analysis on the twelve plans revealed that over 90% of the voxels in the proximity of the penumbra region satisfied the gamma criteria of 2% dose difference and 2 mm distance‐to‐agreement. The initial QA results during the first nine months after installation of the RSS are presented. Jaw motion was shown to be accurate with maximum encoder error less than 0.42 mm. The consistency of relative output for discrete and continuously sweeping jaws was within 1.2%. Longitudinal radiation profiles agreed to the reference profile with maximum gamma and field width error . With the same jaw width, RSS showed better dose penumbrae compared to those from static jaw delivery. The initial QA results on the accuracy of moving jaws, reproducibility of dosimetric output and profiles were satisfactory.PACS number: 87.55.km
Dose differences in intensity‐modulated radiotherapy plans calculated with pencil beam and Monte Carlo for lung SBRT
Authors: Liu Han , Zhuang Tingliang , Stephans Kevin , Videtic Gregory , Raithel Stephen , Djemil Toufik , Xia Ping 
Published: February 2017

For patients with medically inoperable early‐stage non‐small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy, early treatment plans were based on a simpler dose calculation algorithm, the pencil beam (PB) calculation. Because these patients had the longest treatment follow‐up, identifying dose differences between the PB calculated dose and Monte Carlo calculated dose is clinically important for understanding of treatment outcomes. Previous studies found significant dose differences between the PB dose calculation and more accurate dose calculation algorithms, such as convolution‐based or Monte Carlo (MC), mostly for three‐dimensional conformal radiotherapy (3D CRT) plans. The aim of this study is to investigate whether these observed dose differences also exist for intensity‐modulated radiotherapy (IMRT) plans for both centrally and peripherally located tumors. Seventy patients (35 central and 35 peripheral) were retrospectively selected for this study. The clinical IMRT plans that were initially calculated with the PB algorithm were recalculated with the MC algorithm. Among these paired plans, dosimetric parameters were compared for the targets and critical organs. When compared to MC calculation, PB calculation overestimated doses to the planning target volumes (PTVs) of central and peripheral tumors with different magnitudes. The doses to 95% of the central and peripheral PTVs were overestimated by and , respectively. This dose overestimation did not affect doses to the critical organs, such as the spinal cord and lung. In conclusion, for NSCLC treated with IMRT, dose differences between the PB and MC calculations were different from that of 3D CRT. No significant dose differences in critical organs were observed between the two calculations.PACS number: 87.53.Ly
Quantitative analysis of brass compensators for commissioning of the Pinnacle planning system for IMRT
Authors: Gates Larry L. , Gladstone David J. 
Published: February 2017

Brass compensators for beam modulation present an alternative method for IMRT treatment planning to traditional dynamic leaf modulation. In this work, we present a detailed method to commission the Pinnacle treatment planning system for IMRT using brass compensators. Beam attenuation from various brass thicknesses were measured using an ion chamber, as well as a MapCHECK device, for a representative seven‐field IMRT plan. We show that Pinnacle's parameters for compensators can be optimized to match the measured results while still maintaining the original open‐beam model. Only Pinnacle's modified scatter factor and brass density value were adjusted. Beam attenuation in several brass slabs were optimized by minimizing a function of measured and modeled data for several depths in solid water. Using MapCHECK, Pinnacle's parameters were optimized by minimizing the number of points that fail during a gamma analysis of seven fields in a typical IMRT plan. Our results show that Pinnacle's 10X beam is best modeled using a brass density of and a modified scatter factor of 0.1 .PACS numbers: 87.56.N, 87.56.ng, 87.55.kh, 87.55.de
Characterization of the energy response and backscatter contribution for two electronic personal dosimeter models
Authors: Meier Joseph , Kappadath S. Cheenu 
Published: February 2017

We characterized the energy response of personal dose equivalent ( in mrem) and the contribution of backscatter to the readings of two electronic personal dosimeter (EPD) models with radionuclides commonly used in a nuclear medicine clinic. The EPD models characterized were the RADOS RAD‐60R, and the SAIC PD‐10i. The experimental setup and calculation of EPD energy response was based on ANSI/HPS N13.11‐2009. Fifteen RAD‐60R and 2 PD‐10i units were irradiated using , , and radionuclides with emission energies at 140 keV, 364 keV, and 511 keV, respectively. At each energy, the EPDs output in [mrem] were recorded with 15 inch thick PMMA to simulate backscatter form the torso. Simultaneous free‐in‐air exposure rate measurements were also performed using two Victoreen ionization survey meters to calculate the expected EPD values per ANSI/HPS N13.11‐2009. The energy response was calculated by taking the ratio of the EPD readings with the expected readings and a two‐tailed z‐test was used to determine the significance of the ratio deviating away from unity. The contribution from backscatter was calculated by taking the ratio of the EPD readings with and without backscatter material. A paired, two‐tailed t‐test was used to determine the significance of change in EPD readings. The RAD‐60R mean energy response at 140 keV was 0.85, and agreed to within 5% and 11% at 364 and 511 keV, respectively. The PD‐10i mean energy response at 140 keV was 1.20, and agreed to within 5% at 364 and 511 keV, respectively. On average, in the presence of acrylic, RAD‐60R values increased by 32%, 12%, and 14%, at 140, 364, and 511 keV, respectively; all increases were statistically significant. The PD‐10i increased by 25%, 19%, and 10% at 140 keV, 364 keV, and 511 keV, respectively; however, only the 140 keV measurement was statistically significant. Although both EPD models performed within the manufacturers' specifications of in the energy ranges used, they fell outside of our criteria of 10% at lower energies, suggesting the need to calculate energy‐dependent correction factors, depending on the intended EPD use.PACS numbers: 87.53.Bn, 87.55.N‐, 87.57.U‐
Impact of scanning parameters and breathing patterns on image quality and accuracy of tumor motion reconstruction in 4D CBCT: a phantom study
Authors: Lee Soyoung , Yan Guanghua , Lu Bo , Kahler Darren , Li Jonathan G. , Sanjiv Samant S. 
Published: February 2017

Four‐dimensional, cone‐beam CT (4D CBCT) substantially reduces respiration‐induced motion blurring artifacts in three‐dimension (3D) CBCT. However, the image quality of 4D CBCT is significantly degraded which may affect its accuracy in localizing a mobile tumor for high‐precision, image‐guided radiation therapy (IGRT). The purpose of this study was to investigate the impact of scanning parameters (hereinafter collectively referred to as scanning sequence) and breathing patterns on the image quality and the accuracy of computed tumor trajectory for a commercial 4D CBCT system, in preparation for its clinical implementation. We simulated a series of periodic and aperiodic sinusoidal breathing patterns with a respiratory motion phantom. The aperiodic pattern was created by varying the period or amplitude of individual sinusoidal breathing cycles. 4D CBCT scans of the phantom were acquired with a manufacturer‐supplied scanning sequence (4D‐S‐slow) and two in‐house modified scanning sequences (4D‐M‐slow and 4D‐M‐fast). While 4D‐S‐slow used small field of view (FOV), partial rotation (200°), and no imaging filter, 4D‐M‐slow and 4D‐M‐fast used medium FOV, full rotation, and the F1 filter. The scanning speed was doubled in 4D‐M‐fast (100°/min gantry rotation). The image quality of the 4D CBCT scans was evaluated using contrast‐to‐noise ratio (CNR), signal‐to‐noise ratio (SNR), and motion blurring ratio (MBR). The trajectory of the moving target was reconstructed by registering each phase of the 4D CBCT with a reference CT. The root‐mean‐squared‐error (RMSE) analysis was used to quantify its accuracy. Significant decrease in CNR and SNR from 3D CBCT to 4D CBCT was observed. The 4D‐S‐slow and 4D‐M‐fast scans had comparable image quality, while the 4D‐M‐slow scans had better performance due to doubled projections. Both CNR and SNR decreased slightly as the breathing period increased, while no dependence on the amplitude was observed. The difference of both CNR and SNR between periodic and aperiodic breathing patterns was insignificant (). At end‐exhale phases, the motion blurring was negligible for both periodic and aperiodic breathing patterns; at mid‐inhale phase, the motion blurring increased as the period, the amplitude or the amount of cycle‐to‐cycle variation on amplitude increased. Overall, the accuracy of localizing the moving target in 4D CBCT was within 2 mm under all studied cases. No difference in the RMSEs was noticed among the three scanning sequences. The 4D‐M‐fast scans, free of volume truncation artifacts, exhibited comparable image quality and accuracy in tumor motion reconstruction as the 4D‐S‐slow scans with reduced imaging dose (0.60 cGy vs. 0.99 cGy) due to the use of faster gantry rotation and the F1 filter, suggesting its suitability for clinical use.PACS number: 87.55.Qr
A new method and device of aligning patient setup lasers in radiation therapy
Authors: Hwang Ui‐Jung , Jo Kwanghyun , Lim Young Kyung , Kwak Jung Won , Choi Sang Hyoun , Jeong Chiyoung , Kim Mi Young , Jeong Jong Hwi , Shin Dongho , Lee Se Byeong , Park Jeong‐Hoon , Park Sung Yong , Kim Siyong 
Published: February 2017

The aim of this study is to develop a new method to align the patient setup lasers in a radiation therapy treatment room and examine its validity and efficiency. The new laser alignment method is realized by a device composed of both a metallic base plate and a few acrylic transparent plates. Except one, every plate has either a crosshair line (CHL) or a single vertical line that is used for alignment. Two holders for radiochromic film insertion are prepared in the device to find a radiation isocenter. The right laser positions can be found optically by matching the shadows of all the CHLs in the gantry head and the device. The reproducibility, accuracy, and efficiency of laser alignment and the dependency on the position error of the light source were evaluated by comparing the means and the standard deviations of the measured laser positions. After the optical alignment of the lasers, the radiation isocenter was found by the gantry and collimator star shots, and then the lasers were translated parallel to the isocenter. In the laser position reproducibility test, the mean and standard deviation on the wall of treatment room were mm for the new method whereas they were mm for the conventional method. The mean alignment accuracy was 1.4 mm for the new method, and 2.1 mm for the conventional method on the walls. In the test of the dependency on the light source position error, the mean laser position was shifted just by a similar amount of the shift of the light source in the new method, but it was greatly magnified in the conventional method. In this study, a new laser alignment method was devised and evaluated successfully. The new method provided more accurate, more reproducible, and faster alignment of the lasers than the conventional method.PACS numbers: 87.56.Fc, 87.53.Bn, 87.53.Kn, 87.53.Ly, 87.55.Gh
Soft tissue and water substitutes for megavoltage photon beams: An EGSnrc‐based evaluation
Authors: Aslam Ambreen , Kakakhel Muhammad Basim , Shahid Shaukat Ali , Younas Lubna , Zareen Sobia 
Published: February 2017

In this work, soft‐tissue equivalence of water, polystyrene, PMMA and water equivalence of polystyrene, and PMMA has been assessed for multiple megavoltage photon beams and field sizes. EGSnrc based Monte Carlo (MC) codes, BEAMnrc and DOSXYZnrc are used for the linac head modeling and the phantom dose calculations, respectively. Percentage depth doses (PDDs) are scored for two field sizes (, ) and photon energies (6 MV and 10 MV) in water, polystyrene, PMMA, and soft tissue. The comparisons of PDDs show that soft‐tissue equivalence of various materials varies with the depth in the phantom, field size, and photon energy. Water and PMMA are found to be the closest soft‐tissue and water substitutes, respectively. Soft‐tissue and water equivalence of dosimetry materials need to be evaluated for a range of photon energies and field sizes before their application in complex radiation beams.PACS numbers: 87.55.Gh, 87.55.K‐
Evaluation of MVCT imaging dose levels during helical IGRT: comparison between ion chamber, TLD, and EBT3 films
Authors: Mege Jean‐Pierre , Wenzhao Sun , Veres Attila , Auzac Guillaume , Diallo Ibrahima , Lefkopoulos Dimitri 
Published: February 2017

The purpose of this investigation was to evaluate the dose on megavoltage CT (MVCT) images required for tomotherapy. As imaging possibilities are often used before each treatment and usually used several times before the session, we tried to evaluate the dose delivered during the procedure. For each scanning mode (fine, normal, and coarse), we first established the relative variation of these doses according to different technical parameters (explored length, patient setup). These dose variations measured with the TomoPhant, also known as Cheese phantom, showed the expected variations (due to the variation of scattered radiation) of 15% according to the explored length and according to the phantom setup (due to the variation of the point of measurement in the bore). In order to estimate patient doses, an anthropomorphic phantom was used for thermoluminescent and film dosimetry. The degree of agreement between the two methods was very satisfactory (the differences correspond to 5 mGy per imaging session) for the three sites studied (head & neck, thorax, and abdomen). These measurements allowed us to estimate the delivered dose of between 1 cGy and 4 cGy according to the site and imaging mode. Finally, we attempted to investigate a way to calculate this delivered dose in our patients from the study conducted on a cylindrical phantom and by taking into account data from the initial kV‐CT scan. The results we obtained were close to our measurements, with discrepancies below 5 mGy per MVCT.PACS numbers: 87.53.Bn, 87.55.km, 87.55.Qr
Evaluation of commercial extension plates for the ACR CT accreditation phantom
Authors: Greene‐Donnelly Kerry A. , Ogden Kent M. 
Published: February 2017

The American College of Radiology (ACR) Computed Tomography (CT) Accreditation Program requires submission of phantom scans acquired with the ACR accreditation phantom. There is a known issue with some wide‐beam scanners in which the Hounsfield unit (HU) value of water may be correct when using the scanner manufacturer's phantom, but will be out of range in some scan modes when scanning the accreditation phantom. The phantom manufacturer has developed a product known as Extension Plates to eliminate the water HU value issue. The purpose of this technical note is to evaluate the effectiveness of the Extension Plates in alleviating the water HU issue. The ACR phantom was scanned on nine different CT scanners representing four CT manufacturers at eight different facilities. Scanner models included 16‐ and 64‐channel geometries from each manufacturer. All scanners passed routine daily water HU testing per the manufacturer's instructions. The accreditation phantom was scanned in helical and axial modes both with and without the Extension Plates present. Regions of interest were placed on the linearity test objects as well as the water HU test object in Module 1 of the phantom. Mean values were recorded and compared with the acceptable ranges specified by the ACR accreditation phantom testing instructions. Water HU values failed for one scanner model when scanned in helical mode using the widest collimation available and the Extension Plates were not present. All other scanner models passed the water HU linearity test with or without the Extension Plates in both axial and helical scan modes. Three of the four manufacturers tested failed the linearity test for different materials. The presence of the Extension Plates only affected the HU measurement for the water test object.PACS number(s): 87.57Q, 87.57C