bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dosimetric advantages of O‐ring design radiotherapy system for skull‐base tumors
Authors: Ogura Kengo , Mizowaki Takashi , Ishida Yuichi , Hiraoka Masahiro 
Published: February 2017

The purpose of this study was to investigate whether a new O‐ring design radiotherapy delivery system has advantages in radiotherapy planning for skull‐base tumors. Twenty‐five patients with skull‐base tumors were included in this study. Two plans were made using conventional (Plan A) or new (Plan B) techniques. Plan A consisted of four dynamic conformal arcs (DCAs): two were horizontal, and the other two were from cranial directions. Plan B was created by converting horizontal arcs to those from caudal directions making use of the O‐ring design radiotherapy system. The micromultileaf collimators were fitted to cover at least 99% of the planning target volume with prescribed doses, 90% of the dose at the isocenter. The two plans were compared in terms of target homogeneity, conformity, and irradiated volume of normal tissues, using a two‐sided paired t‐test. For evaluation regarding target coverage, the homogeneity indices defined by the International Commission on Radiation Units and Measurements 83 were (mean ± standard deviation) and , the conformity indices defined by the Radiation Therapy Oncology Group were and , and the Paddick's conformity indices were and , in Plans A and B, respectively. For evaluation of irradiated normal tissue, the Paddick's gradient indices were and in Plans A and B, respectively. All of these differences were statistically significant (p‐values ). The mean doses of optic nerves, eyes, brainstem, and hippocampi were also significantly lower in Plan B. The DCA technique from caudal directions using the new O‐ring design radiotherapy system can improve target homogeneity and conformity compared with conventional DCA techniques, and can also decrease the volume of surrounding normal tissues that receives moderate doses.PACS numbers: 87.55.‐x, 87.55.D‐, 87.55.dk
Assessment of potential jaw‐tracking advantage using control point sequences of VMAT planning
Authors: Kim Jung‐in , Park Jong Min , Park So‐Yeon , Choi Chang Heon , Wu Hong‐Gyun , Ye Sung‐Joon 
Published: February 2017

This study aims to evaluate the potential jaw‐tracking advantage using control point sequences of volume volumetric‐modulated arc therapy (VMAT) planning. VMAT plans for patients with prostate and head and neck (H&N) cancers were converted into new static arc (SA) plans. The SA plan consisted of a series of static fields at each control point of the VMAT plan. All other machine parameters of the SA plan were perfectly identical to those of the original VMAT plan. The jaw‐tracking static arc (JTSA) plans were generated with fields that closed the jaws of each SA field into the multileaf collimators (MLCs) aperture. The dosimetric advantages of JTSA over SA were evaluated in terms of a dose‐volume histogram (DVH) of organ at risk (OAR) after renormalizing both plans to make the same target coverage. Both plans were delivered to the MatriXX‐based COMPASS system for 3D volume dose verification. The average jaw size reduction of the JTSA along the X direction was for prostate patients and for H&N patients. For prostate patients, the organs far from the target showed larger sparing (3.7%—8.1% on aver‐age) in JTSA than the organs adjacent to the target (1.1%—1.5%). For the H&N plans, the mean dose reductions for all organs ranged from 4.3% to 11.9%. The dose reductions were more significant in the dose regions of , and than the dose regions of , and for all patients. Likewise, the deliverability and reproducibility of jaw‐tracking plan were validated. The measured dosimetric advantage of JTSA over SA coincided with the calculated one above.PACS numbers: 87.55.D‐, 87.55.ne
Commissioning and verification of the collapsed cone convolution superposition algorithm for SBRT delivery using flattening filter‐free beams
Authors: Foster Ryan D. , Speiser Michael P. , Solberg Timothy D. 
Published: February 2017

Linacs equipped with flattening filter‐free (FFF) megavoltage photon beams are now commercially available. However, the commissioning of FFF beams poses challenges that are not shared with traditional flattened megavoltage X‐ray beams. The planning system must model a beam that is peaked in the center and has an energy spectrum that is softer than the flattened beam. Removing the flattening filter also increases the maximum possible dose rates from 600 MU/min up to 2400 MU/min in some cases; this increase in dose rate affects the recombination correction factor, , used during absolute dose calibration with ionization chambers. We present the first‐reported experience of commissioning, verification, and clinical use of the collapsed cone convolution superposition (CCCS) dose calculation algorithm for commercially available flattening filter‐free beams. Our commissioning data are compared to previously reported measurements and Monte Carlo studies of FFF beams. Commissioning was verified by making point‐dose measurement of test plans, irradiating the RPC lung phantom, and performing patient‐specific QA. The average point‐dose difference between calculations and measurements of all test plans and all patient specific QA measurements is 0.80%, and the RPC phantom absolute dose differences for the two thermoluminescent dosimeters (TLDs) in the phantom planning target volume (PTV) were 1% and 2%, respectively. One hundred percent (100%) of points in the RPC phantom films passed the RPC gamma criteria of 5% and 5 mm. Our results show that the CCCS algorithm can accurately model FFF beams and calculate SBRT dose distributions using those beams.PACS number: 87.55.kh
Clinical evaluation of an anatomy‐based patient specific quality assurance system
Authors: Hauri Pascal , Verlaan Sarah , Graydon Shaun , Ahnen Linda , Klöck Stephan , Lang Stephanie 
Published: February 2017

The Delta4DVH Anatomy 3D quality assurance (QA) system (ScandiDos), which converts the measured detector dose into the dose distribution in the patient geometry was evaluated. It allows a direct comparison of the calculated 3D dose with the measured back‐projected dose. In total, 16 static and 16 volumetric‐modulated arc therapy (VMAT) fields were planned using four different energies. Isocenter dose was measured with a pinpoint chamber in homogeneous phantoms to investigate the dose prediction by the Delta4DVH Anatomy algorithm for static fields. Dose distributions of VMAT fields were measured using GAFCHROMIC film. Gravitational gantry errors up to 10° were introduced into all VMAT plans to study the potential of detecting errors. Additionally, 20 clinical treatment plans were verified. For static fields, the Delta4DVH Anatomy predicted the isocenter dose accurately, with a deviation to the measured phantom dose of . For VMAT fields the predicted Delta4DVH Anatomy dose in the isocenter plane corresponded to the measured dose in the phantom, with an average gamma agreement index (GAI) of . The Delta4DVH Anatomy detected the induced systematic gantry error of 10° with a relative GAI change of . The conventional Delta4PT QA system detected a GAI change of . The conventional Delta4PT GAI was for the clinical treatment plans. The mean body and PTV‐GAI for the Delta4DVH Anatomy were and ; however, this dropped to and for passing criteria of . The anatomy‐based patient specific quality assurance system predicts the dose distribution correctly for a homogeneous case. The limiting factor for the error detection is the large variability in the error‐free plans. The dose calculation algorithm is inferior to that used in the TPS (Eclipse).PACS numbers: 87.56.Fc, 87.56.‐v
Performance of dose calculation algorithms from three generations in lung SBRT: comparison with full Monte Carlo‐based dose distributions
Authors: Ojala Jarkko J. , Kapanen Mika K. , Hyödynmaa Simo J. , Wigren Tuija K. , Pitkänen Maunu A. 
Published: February 2017

The accuracy of dose calculation is a key challenge in stereotactic body radiotherapy (SBRT) of the lung. We have benchmarked three photon beam dose calculation algorithms — pencil beam convolution (PBC), anisotropic analytical algorithm (AAA), and Acuros XB (AXB) — implemented in a commercial treatment planning system (TPS), Varian Eclipse. Dose distributions from full Monte Carlo (MC) simulations were regarded as a reference. In the first stage, for four patients with central lung tumors, treatment plans using 3D conformal radiotherapy (CRT) technique applying 6 MV photon beams were made using the AXB algorithm, with planning criteria according to the Nordic SBRT study group. The plans were recalculated (with same number of monitor units (MUs) and identical field settings) using BEAMnrc and DOSXYZnrc MC codes. The MC‐calculated dose distributions were compared to corresponding AXB‐calculated dose distributions to assess the accuracy of the AXB algorithm, to which then other TPS algorithms were compared. In the second stage, treatment plans were made for ten patients with 3D CRT technique using both the PBC algorithm and the AAA. The plans were recalculated (with same number of MUs and identical field settings) with the AXB algorithm, then compared to original plans. Throughout the study, the comparisons were made as a function of the size of the planning target volume (PTV), using various dose‐volume histogram (DVH) and other parameters to quantitatively assess the plan quality. In the first stage also, 3D gamma analyses with threshold criteria and were applied. The AXB‐calculated dose distributions showed relatively high level of agreement in the light of 3D gamma analysis and DVH comparison against the full MC simulation, especially with large PTVs, but, with smaller PTVs, larger discrepancies were found. Gamma agreement index (GAI) values between 95.5% and 99.6% for all the plans with the threshold criteria were achieved, but threshold criteria showed larger discrepancies. The TPS algorithm comparison results showed large dose discrepancies in the PTV mean dose , nearly 60%, for the PBC algorithm, and differences of nearly 20% for the AAA, occurring also in the small PTV size range. This work suggests the application of independent plan verification, when the AAA or the AXB algorithm are utilized in lung SBRT having PTVs smaller than 20‐25 cc. The calculated data from this study can be used in converting the SBRT protocols based on type ‘a’ and/or type ‘b’ algorithms for the most recent generation type ‘c’ algorithms, such as the AXB algorithm.PACS numbers: 87.55.‐x, 87.55.D‐, 87.55.K‐, 87.55.kd, 87.55.Qr
Efficacy evaluation of retrospectively applying the Varian normal breathing predictive filter for volume definition and artifact reduction in 4D CT lung patients
Authors: Malone Ciaran , Rock Luke , Skourou Christina 
Published: February 2017

Phase‐based sorting of four‐dimensional computed tomography (4D CT) datasets is prone to image artifacts due to patient's breathing irregularities that occur during the image acquisition. The purpose of this study is to investigate the effect of the Varian normal breathing predictive filter (NBPF) as a retrospective phase‐sorting parameter in 4D CT. Ten 4D CT lung cancer datasets were obtained. The volumes of all tumors present, as well as the total lung volume, were calculated on the maximum intensity projection (MIP) images as well as each individual phase image. The NBPF was varied retrospectively within the available range, and changes in volume and image quality were recorded. The patients' breathing trace was analysed and the magnitude and location of any breathing irregularities were correlated to the behavior of the NBPF. The NBPF was found to have a considerable effect on the quality of the images in MIP and single‐phase datasets. When used appropriately, the NBPF is shown to have the ability to account for and correct image artifacts. However, when turned off (0%) or set above a critical level (approximately 40%), it resulted in erroneous volume reconstructions with variations in tumor volume up to 26.6%. Those phases associated with peak inspiration were found to be more susceptible to changes in the NBPF. The NBPF settings selected prior to exporting the breathing trace for patients evaluated using 4D CT directly affect the accuracy of the targeting and volume estimation of lung tumors. Recommendations are made to address potential errors in patient anatomy introduced by breathing irregularities, specifically deep breath or cough irregularities, by implementing the proper settings and use of this tool.PACS numbers: 87.57.Q‐, 87.57.C‐, 87.57.N‐, 87.57.nf, 87.55.D‐.
Dose modification factor analysis of multilumen balloon brachytherapy applicator with Monte Carlo simulation
Authors: Pearson David , Williams Eric A. 
Published: February 2017

The Contura brachytherapy applicator is a silicone balloon with five lumens in which a high‐dose‐rate brachytherapy source can traverse. Multilumen applicators, like the Contura, are used in accelerated partial breast irradiation (APBI) brachytherapy in instances where asymmetric dose distributions are desired; for example, when the applicator surface‐to‐skin thickness is small (< 7 mm). In these instances, the air outside the patient and the lung act as a poor scattering medium, scattering less dose back into the breast and affecting the dose distribution. The recent report by Task Group 186 of the American Association of Physicists in Medicine (AAPM) has outlined the importance of moving towards brachytherapy dose calculations using heterogeneity corrections. However, at this time, many commercial treatment planning systems do not correct for tissue heterogeneity, which can result in inaccuracies in the planned dose distribution. To quantify the deviation in the skin dose we utilize the dose modification factor (DMF), defined as the ratio of the dose rate at 1 cm beyond the applicator surface with homogenous medium, to the dose rate at 1 cm with heterogeneous medium. This investigation models the Contura applicator with the Monte Carlo N‐Particle code version 5, and determines a DMF through simulation. Taking all geometrical considerations into account, an accurate model of the Contura balloon applicator was created in MCNP and used to run simulations. The dose modification factor was found to be only slightly dependent on whether the dose distribution was symmetric or asymmetric. These results indicate that the dose delivered to part of the PTV may be lower than the planned dose by up to 12%, and that these brachytherapy plans should be viewed with caution. In addition to studying the effects of backscatter, an evaluation was made regarding the capabilities of the Contura device to shape an asymmetric dose distribution. We compared these results to a previous study of a MammoSite ML and a SAVI device and found that the dose shaping capabilities of the Contura were quite similar to that of the MammoSite ML, but markedly inferior to the SAVI.PACS number: 87.53.Jw
Dosimetric impact of gold markers implanted closely to lung tumors: a Monte Carlo simulation
Authors: Shiinoki Takehiro , Sawada Akira , Ishihara Yoshitomo , Miyabe Yuki , Matsuo Yukinori , Mizowaki Takashi , Kokubo Masaki , Hiraoka Masahiro 
Published: February 2017

We are developing an innovative dynamic tumor tracking irradiation technique using gold markers implanted around a tumor as a surrogate signal, a real‐time marker detection system, and a gimbaled X‐ray head in the Vero4DRT. The gold markers implanted in a normal organ will produce uncertainty in the dose calculation during treatment planning because the photon mass attenuation coefficient of a gold marker is much larger than that of normal tissue. The purpose of this study was to simulate the dose variation near the gold markers in a lung irradiated by a photon beam using the Monte Carlo method. First, the single‐beam and the opposing‐beam geometries were simulated using both water and lung phantoms. Subsequently, the relative dose profiles were calculated using a stereotactic body radiotherapy (SBRT) treatment plan for a lung cancer patient having gold markers along the anteriorposterior (AP) and right‐left (RL) directions. For the single beam, the dose at the gold marker‐phantom interface laterally along the perpendicular to the beam axis increased by a factor of 1.35 in the water phantom and 1.58 in the lung phantom, respectively. Furthermore, the entrance dose at the interface along the beam axis increased by a factor of 1.63 in the water phantom and 1.91 in the lung phantom, while the exit dose increased by a factor of 1.00 in the water phantom and 1.12 in the lung phantom, respectively. On the other hand, both dose escalations and dose de‐escalations were canceled by each beam for opposing portal beams with the same beam weight. For SBRT patient data, the dose at the gold marker edge located in the tumor increased by a factor of 1.30 in both AP and RL directions. In clinical cases, dose escalations were observed at the small area where the distance between a gold marker and the lung tumor was ≤ 5 mm, and it would be clinically negligible in multibeam treatments, although further investigation may be required.PACS number: 87.10.Rt
Dosimetric benefits of IMRT and VMAT in the treatment of middle thoracic esophageal cancer: is the conformal radiotherapy still an alternative option?
Authors: Wu Zhiqin , Xie Congying , Hu Meilong , Han Ce , Yi Jinling , Zhou Yongqiang , Yan Huawei , Jin Xiance 
Published: February 2017

The purpose of this study is to investigate the dosimetric differences among conformal radiotherapy (CRT), intensity‐modulated radiotherapy (IMRT), and volumetric‐modulated radiotherapy (VMAT) in the treatment of middle thoracic esophageal cancer, and determine the most appropriate treatment modality. IMRT and one‐arc VMAT plans were generated for eight middle thoracic esophageal cancer patients treated previous with CRT. The planning target volume (PTV) coverage and protections on organs at risk of three planning schemes were compared. All plans have sufficient PTV coverage and no significant differences were observed, except for the conformity and homogeneity. The lung V5, V10, and V13 in CRT were 47.9% ± 6.1%, 36.5% ± 4.6%, and 33.2% ± 4.2%, respectively, which were greatly increased to 78.2% ± 13.7% (p < 0.01), 80.8% ± 14.9% (p < 0.01), 48.4% ± 8.2% (p = 0.05) in IMRT and 58.6% ± 10.5% (p = 0.03), 67.7% ± 14.0% (p < 0.01), and 53.0% ± 10.1% (p < 0.01) in VMAT, respectively. The lung V20 (p = 0.03) in VMAT and the V30 (p = 0.04) in IMRT were lower than those in CRT. Both IMRT and VMAT achieved a better protection on heart. However, the volumes of the healthy tissue outside of PTV irradiated by a low dose were higher for IMRT and VMAT. IMRT and VMAT also had a higher MU, optimization time, and delivery time compared to CRT. In conclusion, all CRT, IMRT, and VMAT plans are able to meet the prescription and there is no clear distinction on PTV coverage. IMRT and VMAT can only decrease the volume of lung and heart receiving a high dose, but at a cost of delivering low dose to more volume of lung and normal tissues. CRT is still a feasible option for middle thoracic esophageal cancer radiotherapy, especially for the cost‐effective consideration.PACS numbers: 87.53.Kn, 87.55.x 87.55.D 87.55.dk
Monte Carlo modeling of HD120 multileaf collimator on Varian TrueBeam linear accelerator for verification of 6X and 6X FFF VMAT SABR treatment plans
Authors: Bergman Alanah M. , Gete Ermias , Duzenli Cheryl , Teke Tony 
Published: February 2017

A Monte Carlo (MC) validation of the vendor‐supplied Varian TrueBeam 6 MV flattened (6X) phase‐space file and the first implementation of the Siebers‐Keall MC MLC model as applied to the HD120 MLC (for 6X flat and 6X flattening filterfree (6X FFF) beams) are described. The MC model is validated in the context of VMAT patient‐specific quality assurance. The Monte Carlo commissioning process involves: 1) validating the calculated open‐field percentage depth doses (PDDs), profiles, and output factors (OF), 2) adapting the Siebers‐Keall MLC model to match the new HD120‐MLC geometry and material composition, 3) determining the absolute dose conversion factor for the MC calculation, and 4) validating this entire linac/MLC in the context of dose calculation verification for clinical VMAT plans. MC PDDs for the 6X beams agree with the measured data to within 2.0% for field sizes ranging from 2 × 2 to 40 × 40 cm2. Measured and MC profiles show agreement in the 50% field width and the 80%‐20% penumbra region to within 1.3 mm for all square field sizes. MC OFs for the 2 to 40 cm2 square fields agree with measurement to within 1.6%. Verification of VMAT SABR lung, liver, and vertebra plans demonstrate that measured and MC ion chamber doses agree within 0.6% for the 6X beam and within 2.0% for the 6X FFF beam. A 3D gamma factor analysis demonstrates that for the 6X beam, > 99% of voxels meet the pass criteria (3%/3 mm). For the 6X FFF beam, > 94% of voxels meet this criteria. The TrueBeam accelerator delivering 6X and 6X FFF beams with the HD120 MLC can be modeled in Monte Carlo to provide an independent 3D dose calculation for clinical VMAT plans. This quality assurance tool has been used clinically to verify over 140 6X and 16 6X FFF TrueBeam treatment plans.PACS number: 87.55.K‐
A Monte Carlo evaluation of beam characteristics for total body irradiation at extended treatment distances
Authors: Chakarova Roumiana , Krantz Marcus 
Published: February 2017

The aim is to study beam characteristics at large distances when focusing on the electron component. In particular, to investigate the utility of spoilers with various thicknesses as an electron source, as well as the effect of different spoiler‐to‐surface distances (STSD) on the beam characteristics and, consequently, on the dose in the superficial region. A MC model of a 15 MV Varian accelerator, validated earlier by experimental data at isocenter and extended distances used in large‐field total body irradiation, is applied to evaluate beam characteristics at distances larger than 400 cm. Calculations are carried out using BEAMnrc/DOSXYZnrc code packages and phase space data are analyzed by the beam data processor BEAMdp. The electron component of the beam is analyzed at isocenter and extended distances, with and without spoilers as beam modifiers, assuming vacuum or air surrounding the accelerator head. Spoiler thickness of 1.6 cm is found to be optimal compared to thicknesses of 0.8 cm and 2.4 cm. The STSD variations should be taken into account when treating patients, in particular when the treatment protocols are based on a fixed distance to the patient central sagittal plane, and also, in order to maintain high dose in the superficial region.PACS numbers: 87.55.D‐, 87.55.de, 87.55.K‐