bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dose distribution changes with shielding disc misalignments and wrong orientations in breast IOERT: a Monte Carlo – GEANT4 and experimental study
Authors: Russo Giorgio , Casarino Carlo , Arnetta Gaetano , Candiano Giuliana , Stefano Alessandro , Alongi Filippo , Borasi Giovanni , Messa Cristina , Gilardi Maria C. 
Published: February 2017

One of the most relevant risks in breast intraoperative electron radiotherapy (IOERT) is the incorrect positioning of the shielding disc. If such a setup error occurs, the treatment zone could receive a nonuniform dose delivery, and a considerable part of the electron beam could hit — and irradiate — the patient's healthy tissue. However misalignment and tilt angle of the shielding disc can be evaluated, but it is not possible to measure the corresponding in vivo dose distribution. This led us to develop a simulation using the Geant4 Monte Carlo toolkit to study the effects of disc configuration on dose distribution. Some parameters were investigated: the shielding factor (SF), the radiation back scattering factor (BSF), the volume–dose histogram in the treatment zone, and the maximum leakage dose (MLD) in normal tissue. A lateral shift of the disc (in the plane perpendicular to the beam axis) causes a decrease in SF (from 4% for a misalignment of 5 mm to 40% for a misalignment of 40 mm), but no relevant dose variations were found for a tilt angle until 10°. In the same uncorrected disc positions, the BSF shows no significant change. MLD rises to 3.45 Gy for a 14 mm misalignment and 4.60 Gy for 30° tilt angle when the prescribed dose is 21 Gy. The simulation results are compared with the experimental ones, and allow an a posteriori estimation of the dose distribution in the breast target and underlying healthy tissue. This information could help the surgical team choose a more correct clinical setup, and assist in quantifying the degree of success or failure of an IOERT breast treatment.PACS number: 87.53.Jw, 87.55.dk, 87.55.Gh, 87.55.K‐, 87.55.N‐
Peripheral dose from megavoltage cone‐beam CT imaging for nasopharyngeal carcinoma image‐guided radiation therapy
Authors: Jia Ming X. , Zhang Xu , Li Na , Wang En Y. , Liu Da W. , Cai Wei S. 
Published: February 2017

The growing use of cone‐beam computed tomography (CBCT) for IGRT has increased concerns over the additional radiation dose to patients. The in‐field dose of IGRT and the peripheral dose (PD) from kilovoltage CBCT (KV‐CBCT) imaging have been well quantified. The purpose of this work is to evaluate the peripheral dose from megavoltage CBCT (MV‐CBCT) imaging for nasopharyngeal carcinoma IGRT, to determine the correlation of peripheral dose with MU protocol and imaging field size, and to estimate out‐of‐field organ‐at‐risk (OAR) dose delivered to patients. Measurements of peripheral MV‐CBCT doses were made with a 0.65 cm3 ionization chamber placed inside in a specially designed phantom at various depths and distances from the imaging field edges. The peripheral dose at reference point inside the phantom was measured with the same ionization chamber to investigate the linearity between MUs used for MV‐CBCT imaging and the PD. The peripheral surface doses at the anterior, lateral, and posterior of the phantom at various distances from the imaging field edge were also measured with thermoluminescent dosimeters (TLDs). Seven nasopharyngeal carcinoma patients were selected and scanned before treatment with head–neck protocol, and the peripheral surface doses were measured with TLDs placed on the anterior, lateral, and posterior surfaces at the axial plane of 15 cm distance from the field edge. The measured peripheral doses data in the phantom were utilized to estimate the peripheral OAR dose. Peripheral dose from MV‐CBCT imaging increased with increasing number of MUs used for imaging protocol and with increasing the imaging field size. The measured peripheral doses in the phantom decreased as distance from the imaging field edges increased. PD also decreased as the depth from the phantom surface increased. For the patient PD measurements, the anterior, lateral, and posterior surface doses of 15 cm distance from the field edge were , , and , respectively. The lens, thyroid, breast, and ovary and testicle, which are outside the treatment and imaging fields, were estimated to receive peripheral OAR doses from MV‐CBCT imaging of , , , , and , respectively. In conclusion, MV‐CBCT generates a peripheral dose beyond the edge of the MV‐CBCT scanning field that is of a similar order of magnitude to the peripheral dose from kV‐CBCT imaging. In clinic, using the smallest number of MUs allowable and reducing MV‐CBCT scanning field size without compromising acquired image quality is an effective method of reducing the peripheral OAR dose received by patients.PACS number: 89
An automated method for comparing motion artifacts in cine four‐dimensional computed tomography images
Authors: Cui Guoqiang , Jew Brian , Hong Julian C. , Johnston Eric W. , Loo Billy W. , Maxim Peter G 
Published: February 2017

The aim of this study is to develop an automated method to objectively compare motion artifacts in two four‐dimensional computed tomography (4D CT) image sets, and identify the one that would appear to human observers with fewer or smaller artifacts. Our proposed method is based on the difference of the normalized correlation coefficients between edge slices at couch transitions, which we hypothesize may be a suitable metric to identify motion artifacts. We evaluated our method using ten pairs of 4D CT image sets that showed subtle differences in artifacts between images in a pair, which were identifiable by human observers. One set of 4D CT images was sorted using breathing traces in which our clinically implemented 4D CT sorting software miscalculated the respiratory phase, which expectedly led to artifacts in the images. The other set of images consisted of the same images; however, these were sorted using the same breathing traces but with corrected phases. Next we calculated the normalized correlation coefficients between edge slices at all couch transitions for all respiratory phases in both image sets to evaluate for motion artifacts. For nine image set pairs, our method identified the 4D CT sets sorted using the breathing traces with the corrected respiratory phase to result in images with fewer or smaller artifacts, whereas for one image pair, no difference was noted. Two observers independently assessed the accuracy of our method. Both observers identified 9 image sets that were sorted using the breathing traces with corrected respiratory phase as having fewer or smaller artifacts. In summary, using the 4D CT data of ten pairs of 4D CT image sets, we have demonstrated proof of principle that our method is able to replicate the results of two human observers in identifying the image set with fewer or smaller artifacts.PACS number: 87.57.cp; 87.57.N‐
A light field‐based method to adjust rounded leaf end MLC position for split shape dose calculation correction in a radiation therapy treatment planning system
Authors: Wu Jia‐Ming , Lee Tsair‐Fwu , Kuo Chung‐Ming , Chen Ching‐Jiang , Hsiao Kuan‐Yin , Yeh Shyh‐An 
Published: February 2017

We present an analytical and experimental study of split shape dose calculation correction by adjusting the position of the round leaf end position in an intensity‐modulated radiation therapy treatment planning system. The precise light field edge position () was derived from 50% of the central axis dose created by nominal light field using geometry and mathematical methods. Leaf position (), defined in the treatment planning system for monitor unit calculation, could be derived from . Offset (correction) could be obtained by the position corresponding to 50% of the central axis dose minus the position. For SSD from 90 cm to 120 cm at 6 MV and 10 MV, the 50% dose position was located outside of in the MLC leaf position range of to , where the offset correction positively increased, whereas the offset correction negatively increased when the MLC leaf position was in the range of to and to when the 50% position was located inside . The monitor unit calculation could provide underdosage or overdosage of 7.5% per mm without offset correction. Calibration could be performed at a certain SSD to fit all SSD offset corrections. With careful measurement and an accurate offset correction, it is possible to achieve the dose calculation with 0.5% error for the adjusted MLC leaf edge location in the treatment planning system.PACS number: 87.53.Tf, 87.55.x, 87.55.D, 87.55.dk
Reference dosimetry using radiochromic film
Authors: Girard Frédéric , Bouchard Hugo , Lacroix Frédéric 
Published: February 2017

The objectives of this study are to identify and quantify factors that influence radiochromic film dose response and to determine whether such films are suitable for reference dosimetry. The influence of several parameters that may introduce systematic dose errors when performing reference dose measurements were investigated. The effect of the film storage temperature was determined by comparing the performance of three lots of GAFCHROMIC EBT2 films stored at either or room temperature. The effect of high or low () relative humidity was also determined. Doses measured in optimal conditions with EBT and EBT2 films were then compared with an A12 ionization chamber measurement. Intensity‐modulated radiation therapy quality controls using EBT2 films were also performed in reference dose. The results obtained using reference dose measurements were compared with those obtained using relative dose measurements. Storing the film at improves the stability of the film over time, but does not eliminate the noncatalytic film development, seen as a rise in optical density over time in the absence of radiation. Relative humidity variations ranging from 80% to 20% have a strong impact on the optical density and could introduce dose errors of up to 15% if the humidity were not controlled during the film storage period. During the scanning procedure, the film temperature influences the optical density that is measured. When controlling for these three parameters, the dose differences between EBT or EBT2 and the A12 chamber are found to be within (2σ level) over a dose range of 20–350 cGy. Our results also demonstrate the limitation of the Anisotropic Analytical Algorithm for dose calculation of highly modulated treatment plans.PACS numbers: 87.55.Qr; 87.56.Fc
Is wax equivalent to tissue in electron conformal therapy planning? A Monte Carlo study of material approximation introduced dose difference
Authors: Zhang Ray R. , Feygelman Vladimir , Harris Eleanor R. , Rao Nikhil , Moros Eduardo G. , Zhang Geoffrey G. 
Published: February 2017

With CT‐based Monte Carlo (MC) dose calculations, material composition is often assigned based on the standard Hounsfield unit ranges. This is known as the density threshold method. In bolus electron conformal therapy (BolusECT), the bolus material, machineable wax, would be assigned as soft tissue and the electron density is assumed equivalent to soft tissue based on its Hounsfield unit. This study investigates the dose errors introduced by this material assignment. BEAMnrc was used to simulate electron beams from a Trilogy accelerator. SPRRZnrc was used to calculate stopping power ratios (SPR) of tissue to wax, , and tissue to water, , for 6, 9, 12, 15, and 18 MeV electron beams, of which 12 and 15 MeV beams are the most commonly used energies in BolusECT. DOSXYZnrc was applied in dose distribution calculations in a tissue phantom with either flat wax slabs of various thicknesses or a wedge‐shaped bolus on top. Dose distribution for two clinical cases, a chest wall and a head and neck, were compared with the bolus material treated as wax or tissue. The values for 12 and 15 MeV beams are between 0.935 and 0.945, while the values are between 0.990 and 0.991. For a 12 MeV beam, the dose in tissue immediately under the bolus is overestimated by 2.5% for a 3 cm bolus thickness if the wax bolus is treated as tissue. For 15 MeV beams, the error is 1.4%. However, in both clinical cases the differences in the PTV DVH is negligible. Due to stopping power differences, dose differences of up to 2.5% are observed in MC simulations if the bolus material is misassigned as tissue in BolusECT dose calculations. However, for boluses thinner than 2 cm that are more likely encountered in practice, the error is within clinical tolerance.PACS numbers: 87.55.km, 87.56.ng
A dosimetric evaluation of VMAT for the treatment of non‐small cell lung cancer
Authors: Merrow Caitlin E. , Wang Iris Z. , Podgorsak Matthew B. 
Published: February 2017

The purpose of this study was to demonstrate the dosimetric potential of volumetric‐modulated arc therapy (VMAT) for the treatment of patients with medically inoperable stage I/II non‐small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT). Fourteen patients treated with 3D CRT with varying tumor locations, tumor sizes, and dose fractionation schemes were chosen for study. The prescription doses were 48 Gy in 4 fractions, 52.5 Gy in 5 fractions, 57.5 Gy in 5 fractions, and 60 Gy in 3 fractions for 2, 5, 1, and 6 patients, respectively. VMAT treatment plans with a mix of two to three full and partial noncoplanar arcs with 5°–25° separations were retrospectively generated using Eclipse version 10.0. The 3D CRT and VMAT plans were then evaluated by comparing their target dose, critical structure dose, high dose spillage, and low dose spillage as defined according to RTOG 0813 and RTOG 0236 protocols. In the most dosimetrically improved case, VMAT was able to decrease the dose from 17.35 Gy to 1.54 Gy to the heart. The decreased in 11 of 14 cases when using VMAT. The three that worsened were still within the acceptance criteria. Of the 14 3D CRT plans, seven had a minor deviation, while only one of the 14 VMAT plans had a minor deviation. The improved in 13 of the 14 VMAT cases. The one case that worsened was still within the acceptance criteria of the RTOG protocol. Of the 14 3D CRT plans, seven had an deviation. Only one of the 14 VMAT plans had an deviation, but it was still improved compared to the 3D CRT plan. In this cohort of patients, no evident dosimetric compromises resulted from planning SBRT treatments with VMAT relative to the 3D CRT treatment plans actually used in their treatment.PACS numbers: 87.50.‐a, 87.53.‐j, 87.55.‐x, 87.55.D‐, 87.55.dk, 87.55.de
Indigenously developed multipurpose acrylic head phantom for verification of IMRT using film and gel dosimetry
Authors: Gopishankar N. , Vivekanandhan S. , Rath G.K. , Laviraj M.A. , Senthilkumaran S. , Kale S.S. , Thulkar S. , Bisht R.K. , Subramani V. 
Published: February 2017

The purpose of this study was to validate the newly designed acrylic phantom for routine dosimetric purpose in radiotherapy. The phantom can be used to evaluate and compare the calculated dose and measured dose using film and gel dosimetric methods. In this study, a doughnut‐shaped planning target volume () and inner organ at risk () were delineated for an IMRT test plan using the X‐ray CT image of the phantom. The phantom consists of acrylic slabs which are integrated to form a human head with a hole in the middle where several dosimetric inserts can be positioned for measurement. An inverse planning with nine coplanar intensity‐modulated fields was created using Pinnacle TPS. For the film analysis, EBT2 film, flatbed scanner, in‐house developed MATLAB codes and ImageJ software were used. The 3D dose distribution recorded in the MAGAT gel dosimeter was read using a 1.5 T MRI scanner. Scanning parameters were CPMG pulse sequence with 8 equidistant echoes, , echo ms, pixel times 0.5, slice . Using a calibration relationship between absorbed dose and spin‐spin relaxation rate (R2), R2 images were converted to dose images. The dose comparison was accomplished using in‐house MATLAB‐based graphical user interface named “IMRT3DCMP”. For gel measurement dose grid from the TPS was extracted and compared with the measured dose grid of the gel. Gamma index analysis of film measurement for the tolerance criteria of 2%/2 mm, 1%/1 mm showed more than 90% voxels pass rate. Gamma index analysis of 3D gel measurement data showed more than 90% voxels pass rate for different tolerance criteria of 2%/2 mm and 1%/1 mm. Overall both 2D and 3D measurement were in close agreement with the Pinnacle TPS calculated dose. The phantom designed is cost‐effective and the results are promising, but further investigation is required to validate the phantom with other 3D conformal techniques for dosimetric purpose.PACS numbers: 87.53.Kn, 87.55.km, 87.56.N‐
Patient dosimetry for selective internal radiation treatment based on PET imaging
Authors: Ng Sherry C. , Lee Victor H. , Law Martin W. , Liu Rico K. , Ma Vivian W. , Tso Wai Kuen , Leung To Wai 
Published: February 2017

Until recently, the radiation dose to patients undergoing the selective internal radiation treatment (SIRT) procedure is determined by applying the partition model to MAA pretreatment scan. There can be great uncertainty in radiation dose calculated from this approach and we presented a method to compute the 3D dose distributions resulting from SIRT based on positron emission tomography (PET) imaging. Five SIRT treatments were retrospectively analyzed. After SIRT, patients had PET/CT imaging within 6 hours of the procedure. To obtain the 3D dose distribution of the patients, their respective PET images were convolved with a Monte Carlo generated voxel dose kernel. The sensitivity of the PET/CT scanner for was determined through phantom studies. The 3D dose distributions were then presented in DICOM RT dose format. By applying the linear quadratic model to the dose data, we derived the biologically effective dose and dose equivalent to 2 Gy/fraction delivery, taking into account the spatial and temporal dose rate variations specific for SIRT. Based on this data, we intend to infer tumor control probability and risk of radiation induced liver injury from SIRT by comparison with established dose limits. For the five cases, the mean dose to target ranged from to . Due to the inhomogeneous nature of the dose distribution, the GTVs were not covered adequately, leading to very low values of tumor control probability. The mean dose to the normal liver ranged from to . According to QUANTEC recommendation, a patient with primary liver cancer and a patient with metastatic liver cancer has more than 5% risk of radiotherapy‐induced liver disease (RILD).PACS number: 87.53.Bn
Clinical introduction of Monte Carlo treatment planning for lung stereotactic body radiotherapy
Authors: Miura Hideharu , Masai Norihisa , Oh Ryoong–Jin , Shiomi Hiroya , Yamada Kouichi , Sasaki Junichi , Inoue Toshihiko 
Published: February 2017

The purpose of this study was to investigate the impact of Monte Carlo (MC) calculations and optimized dose definitions in stereotactic body radiotherapy (SBRT) for lung cancer patients. We used a retrospective patient review and basic virtual phantom to determine dose prescriptions. Fifty‐three patients underwent SBRT. A basic virtual phantom had a gross tumor volume (GTV) of 10.0 mm with equivalent water density of 1.0 g/cm3, which was surrounded by equivalent lung surrounding the GTV of 0.25 g/cm3. D95 of the planning target volume (PTV) and D99 of the GTV were evaluated with different GTV sizes (5.0 to 30.0 mm) and different lung densities (0.05 to 0.45 g/cm3). Prescribed dose was defined as 95% of the PTV should receive 100% of the dose (48 Gy/4 fractions) using pencil beam (PB) calculation and recalculated using MC calculation. In the patient study, average doses to the D95 of the PTV and D99 of the GTV using the MC calculation plan were 19.9% and 10.2% lower than those by the PB calculation plan, respectively. In the phantom study, decreased doses to the D95 of the PTV and D99 of the GTV using the MC calculation plan were accompanied with changes GTV size from 30.0 to 5.0 mm, which was decreased from 8.4% to 19.6% for the PTV and from 17.4% to 27.5% for the GTV Similar results were seen with changes in lung density from 0. 45 to 0.05 g/cm3, with doses to the D95 of the PTV and D99 of the GTV were decreased from 12.8% to 59.0% and from 7.6% to 44.8%, respectively. The decrease in dose to the PTV with MC calculation was strongly dependent on lung density. We suggest that dose definition to the GTV for lung cancer SBRT be optimized using MC calculation. Our current clinical protocol for lung SBRT is based on a prescribed dose of 44 Gy in 4 fractions to the GTV using MC calculation.PACS number: 87.55.D‐, 87.55.K‐
Characterization of atherosclerotic plaque: a contrast‐detail study using multidetector and cone‐beam computed tomography
Authors: Kasraie Nima , Mah Peter , Keener Carl R. , Clarke Geoffrey D. 
Published: February 2017

A Hindmarsh‐Rose model perceptibility phantom containing inserts with various in vitro atherosclerotic plaque compositions was constructed and imaged on a clinical 64 slice multidetector (MDCT) system using 80 and 120 kVp settings and two other cone‐beam (CBCT) systems at 80 kVp. Perceptibility of the simulated lipid‐fibrotic plaque solutions in the images was evaluated by six observers. The effective doses of the protocols employed were estimated using phantom CTDI‐vol measurements placed at identical settings. The CBCT system allowed reduction in effective dose in comparison with the conventional MDCT system for imaging of the carotid plaque phantoms without degrading image quality. The CBCT dose was less than MDCT, with a mean dose of and for MDCT using two measuring techniques vs. for CBCT. The image quality analysis showed no significant differences in the contrast‐detail (C‐D) curves of the best performing CBCT vs. clinical MDCT using a Mann‐Whitney U test. Results indicate that low‐tube‐potential CBCT may produce comparable C‐D resolution for phantom‐based representations of soft plaque types with respect to MDCT systems. This study suggests that the utility of low kVp CT techniques for evaluating carotid vulnerable atherosclerotic plaque merits further study.PACS numbers: 87.53.Bn, 87.57.N‐, 87.57.Q‐, 87.57.cj
Interactive contour delineation and refinement in treatment planning of image‐guided radiation therapy
Authors: Zhou Wu , Xie Yaoqin 
Published: February 2017

The accurate contour delineation of the target and/or organs at risk (OAR) is essential in treatment planning for image‐guided radiation therapy (IGRT). Although many automatic contour delineation approaches have been proposed, few of them can fulfill the necessities of applications in terms of accuracy and efficiency. Moreover, clinicians would like to analyze the characteristics of regions of interests (ROI) and adjust contours manually during IGRT. Interactive tool for contour delineation is necessary in such cases. In this work, a novel approach of curve fitting for interactive contour delineation is proposed. It allows users to quickly improve contours by a simple mouse click. Initially, a region which contains interesting object is selected in the image, then the program can automatically select important control points from the region boundary, and the method of Hermite cubic curves is used to fit the control points. Hence, the optimized curve can be revised by moving its control points interactively. Meanwhile, several curve fitting methods are presented for the comparison. Finally, in order to improve the accuracy of contour delineation, the process of the curve refinement based on the maximum gradient magnitude is proposed. All the points on the curve are revised automatically towards the positions with maximum gradient magnitude. Experimental results show that Hermite cubic curves and the curve refinement based on the maximum gradient magnitude possess superior performance on the proposed platform in terms of accuracy, robustness, and time calculation. Experimental results of real medical images demonstrate the efficiency, accuracy, and robustness of the proposed process in clinical applications.PACS number: 87.53.Tf