bluuebunny/crossref_metadata_2025_split huggingface dataset:
: a new and effective off‐line correction protocol for rotational setup errors when using a robotic couch
Authors: Martens Daan , Luesink Mark , Huizenga Henk , Pasma Kasper L. 
Published: February 2017

Cone‐beam CTs (CBCTs) installed on a linear accelerator can be used to provide fast and accurate automatic six degrees of freedom (6DoF) vector displacement information of the patient position just prior to radiotherapy. These displacement corrections can be made with 6DoF couches, which are primarily used for patient setup correction during stereotactic treatments. When position corrections are performed daily prior to treatment, the correction is deemed "online". However, the interface between the first generation 6DoF couches and the imaging software is suboptimal. The system requires the user to select manually the patient and type the match result by hand. The introduction of 6DoF setup correction for treatments, other than stereotactic radiotherapy, is hindered by both the high workload associated with the online protocol and the interface issues. For these reasons, we developed software that fully integrates the 6DoF couch with the linear accelerator. To further reduce both the workload and imaging dose, three off‐line 6DoF correction protocols were analyzed. While the protocols require significantly less imaging, the analysis assessed their ability to reduce the systematic rotation setup correction. CBCT scans were acquired for 19 patients with intracranial meningioma. The total number of CBCT scans was 856, acquired before and after radiotherapy treatment fractions. The patient positions were corrected online using a 6DoF robotic couch. The effects on the residual rotational setup error for three off‐line protocols were simulated. The three protocols used were two known off‐line protocols, the no action level (NAL) and the extended no action level (eNAL), and one new off‐line protocol (). The residual setup errors were compared using the systematic and random components of the total setup error. The reduction of the rotational setup error of these protocols was optimized with respect to the required workload (i.e., number of CBCTs required). Rotational errors up to 3.2° were found after initial patient setup. The protocol achieved a reduction of the systematic rotational setup error similar to that of the online protocol (pitch from 0.8° to 0.3°), while requiring 70% fewer CBCTs. With a 6DoF robotic couch, translation, and rotation patient position corrections can be performed off‐line to reduce the systematic setup error, workload, and patient scan dose.PACS numbers: 87.56.Fc, 87.56.Da, 87.57.‐s
Experimental assessment of out‐of‐field dose components in high energy electron beams used in external beam radiotherapy
Authors: Alabdoaburas Mohamad M. , Mege Jean‐Pierre , Chavaudra Jean , Bezin Jérémi Vũ , Veres Attila , de Vathaire Florent , Lefkopoulos Dimitri , Diallo Ibrahima 
Published: February 2017

The purpose of this work was to experimentally investigate the out‐of‐field dose in a water phantom, with several high energy electron beams used in external beam radiotherapy (RT). The study was carried out for 6, 9, 12, and 18 MeV electron beams, on three different linear accelerators, each equipped with a specific applicator. Measurements were performed in a water phantom, at different depths, for different applicator sizes, and off‐axis distances up to 70 cm from beam central axis (CAX). Thermoluminescent powder dosimeters (TLD‐700) were used. For given cases, TLD measurements were compared to EBT3 films and parallel‐plane ionization chamber measurements. Also, out‐of‐field doses at 10 cm depth, with and without applicator, were evaluated. With the Siemens applicators, a peak dose appears at about 12–15 cm out of the field edge, at 1 cm depth, for all field sizes and energies. For the Siemens Primus, with a applicator, this peak reaches 2.3%, 1%, 0.9% and 1.3% of the maximum central axis dose (Dmax) for 6, 9, 12 and 18 MeV electron beams, respectively. For the Siemens Oncor, with a applicator, this peak dose reaches 0.8%, 1%, 1.4%, and 1.6% of Dmax for 6, 9, 12, and 14 MeV, respectively, and these values increase with applicator size. For the Varian 2300C/D, the doses at 12.5 cm out of the field edge are 0.3%, 0.6%, 0.5%, and 1.1% of Dmax for 6, 9, 12, and 18 MeV, respectively, and increase with applicator size. No peak dose is evidenced for the Varian applicator for these energies. In summary, the out‐of‐field dose from electron beams increases with the beam energy and the applicator size, and decreases with the distance from the beam central axis and the depth in water. It also considerably depends on the applicator types. Our results can be of interest for the dose estimations delivered in healthy tissues outside the treatment field for the RT patient, as well as in studies exploring RT long‐term effects.PACS number(s): 87.53.Bn, 87.56.bd, 87.56.J‐
Intensity‐modulated radiotherapy versus proton radiotherapy versus carbon ion radiotherapy for spinal bone metastases: a treatment planning study
Authors: Rief Harald , Chaudhri Naved , Tonndorf‐Martini Eric , Bruckner Thomas , Rieken Stefan , Bostel Tilman , Förster Robert , Schlampp Ingmar , Debus Jürgen , Sterzing Florian 
Published: February 2017

Outcomes for selected patients with spinal metastases may be improved by dose escalation using stereotactic body radiotherapy (SBRT). As target geometry is complex, we compared SBRT plans using step‐and‐shoot intensity‐modulated radiotherapy (IMRT), carbon ion RT, and proton RT. We prepared plans treating cervical, thoracic, and lumbar metastases for three different techniques — IMRT, carbon ion, and proton plans — to deliver a median single 24 Gy fraction such that at least 90% of the planning target volume (PTV) received more than 18 Gy and were compared for PTV coverage, normal organ sparing, and estimated delivery time. PTV coverage did not show significant differences for the techniques, spinal cord dose sparing was lowered with the particle techniques. For the cervical lesion spinal cord maximum dose, dose of 1% (D1), and percent volume receiving 10 Gy () were 11.9 Gy, 9.1 Gy, and 0.5% in IMRT. This could be lowered to 4.3 Gy, 2.5 Gy, and 0% in carbon ion planning and to 8.1 Gy, 6.1 Gy, and 0% in proton planning. Regarding the thoracic lesion no difference was found for the spinal cord. For the lumbar lesion maximum dose, D1 and percent volume receiving 5 Gy () were 13.4 Gy, 8.9 Gy, and 8.9% for IMRT; 1.8 Gy, 0.7 Gy, and 0% for carbon ions; and , and 0% for protons. Estimated mean treatment times were shorter in particle techniques (6–7 min vs. 12–14 min with IMRT). This planning study indicates that carbon ion and proton RT can deliver high‐quality PTV coverage for complex treatment volumes that surround the spinal cord.PACS number: 87.55.dk
Feasibility of MV CBCT‐based treatment planning for urgent radiation therapy: dosimetric accuracy of MV CBCT‐based dose calculations
Authors: Held Mareike , Sneed Penny K. , Fogh Shannon E. , Pouliot Jean , Morin Olivier 
Published: February 2017

Unlike scheduled radiotherapy treatments, treatment planning time and resources are limited for emergency treatments. Consequently, plans are often simple 2D image‐based treatments that lag behind technical capabilities available for nonurgent radiotherapy. We have developed a novel integrated urgent workflow that uses onboard MV CBCT imaging for patient simulation to improve planning accuracy and reduce the total time for urgent treatments. This study evaluates both MV CBCT dose planning accuracy and novel urgent workflow feasibility for a variety of anatomic sites. We sought to limit local mean dose differences to less than 5% compared to conventional CT simulation. To improve dose calculation accuracy, we created separate Hounsfield unit–to–density calibration curves for regular and extended field‐of‐view (FOV) MV CBCTs. We evaluated dose calculation accuracy on phantoms and four clinical anatomical sites (brain, thorax/spine, pelvis, and extremities). Plans were created for each case and dose was calculated on both the CT and MV CBCT. All steps (simulation, planning, setup verification, QA, and dose delivery) were performed in one 30 min session using phantoms. The monitor units (MU) for each plan were compared and dose distribution agreement was evaluated using mean dose difference over the entire volume and gamma index on the central 2D axial plane. All whole‐brain dose distributions gave gamma passing rates higher than 95% for criteria, and pelvic sites ranged between 90% and 98% for criteria. However, thoracic spine treatments produced gamma passing rates as low as 47% for criteria. Our novel MV CBCT‐based dose planning and delivery approach was feasible and time‐efficient for the majority of cases. Limited MV CBCT FOV precluded workflow use for pelvic sites of larger patients and resulted in image clearance issues when tumor position was far off midline. The agreement of calculated MU on CT and MV CBCT was acceptable for all treatment sites.PACS numbers: 87.55.D‐, 87.57.Q‐
Gamma analysis dependence on specified low‐dose thresholds for VMAT QA
Authors: Song Ji‐Hye , Kim Min‐Joo , Park So‐Hyun , Lee Seu‐Ran , Lee Min‐Young , Lee Dong Soo , Suh Tae Suk 
Published: February 2017

The American Association of Physicists in Medicine Task Group 119 instructed institutions to use a low‐dose threshold of 10% or a region of interest determined by the jaw setting when they collected gamma analysis quality assurance (QA) data for the planar dose distribution. However, there are no clinical data to quantitatively demonstrate the impact of the low‐dose threshold on the gamma index. Therefore, we performed a gamma analysis with various low‐dose thresholds in the range of 0% to 15% according to both global and local normalization and different acceptance criteria (, , and ). A total of 30 treatment plans — 10 head and neck, 10 brain, and 10 prostate cancer cases — were randomly selected from the Varian Eclipse treatment planning system (TPS). For the gamma analysis, a calculated portal image was acquired through a portal dose calculation algorithm in the Eclipse TPS, and a measured portal image was obtained using an electronic portal‐imaging device. Then, the gamma analysis was performed using the Portal Dosimetry software (Varian Medical Systems, Palo Alto, CA). The gamma passing rate (%GP) for the global normalization decreased as the low‐dose threshold increased, and all low‐dose thresholds led to %GP values above 95% for both the and criteria. However, for the local normalization, %GP for a low‐dose threshold of 10% was 7.47%, 10.23%, and 6.71% greater than the low‐dose threshold of 0% for head and neck, brain, and prostate for the criteria, respectively. The results indicate that applying the low‐dose threshold to global normalization does not have a critical impact on patient‐specific QA results. However, in the local normalization, the low‐dose threshold level should be carefully selected because the excluded low‐dose points could cause the average %GP to increase rapidly.PACS number: 87.55.Qr
Evaluation of cumulative dose for cone‐beam computed tomography (CBCT) scans within phantoms made from different compositions using Monte Carlo simulations
Authors: Abuhaimed Abdullah , Martin Colin J. , Sankaralingam Marimuthu , Oomen Kurian , Gentle David J. 
Published: February 2017

Measurement of cumulative dose with a small ionization chamber within standard polymethyl methacrylate (PMMA) CT head and body phantoms, 150 mm in length, is a possible practical method for cone‐beam computed tomography (CBCT) dosimetry. This differs from evaluating cumulative dose under scatter equilibrium conditions within an infinitely long phantom , which is proposed by AAPM TG‐111 for CBCT dosimetry. The aim of this study was to investigate the feasibility of using to estimate values for in long head and body phantoms made of PMMA, polyethylene (PE), and water, using beam qualities for tube potentials of . The study also investigated the possibility of using 150 mm PE phantoms for assessment of within long PE phantoms, the ICRU/AAPM phantom. The influence of scan parameters, composition, and length of the phantoms was investigated. The capability of to assess has been defined as the efficiency and assessed in terms of the ratios . The efficiencies were calculated using Monte Carlo simulations for an On‐Board Imager (OBI) system mounted on a TrueBeam linear accelerator. Head and body scanning protocols with beams of width were used. Efficiencies and as a function of beam width exhibited three separate regions. For beam widths , and values were greater than 90% for the head and body phantoms. The efficiency values then fell rapidly with increasing beam width before levelling off at 74% for and 69% for for a 500 mm beam width. The quantities and varied with beam width in a different manner. Values at the centers of the phantoms for narrow beams were lower and increased to a steady state for wide beams, before declining with increasing the beam width, whereas values at the peripheries decreased steadily with beam width. Results for were virtually independent of tube potential, but there was more variation for and . underestimated for beam widths used for CBCT scans, thus it is necessary to use long phantoms, or apply conversion factors () to measurements with standard PMMA CT phantoms. The efficiency values have been used to derive () to allow evaluation of from measurements of . The () only showed a weak dependence on scan parameters and scanner type, and so may be suitable for general application.PACS number: 87.55.K‐, 87.57.Q‐, 87.57.uq.
Pion effects in flattening filter‐free radiation beams
Authors: Corns Robert A. , Huang Vicky W. , Thomas Steven D. 
Published: February 2017

Flattening filter‐free radiation beams have higher dose rates that significantly increase the ion recombination rate in an ion chamber's volume and lower the signal read by the chamber‐electrometer pair. The ion collection efficiency correction () accounts for the loss of signal and subsequently changes dosimetric quantities when applied. We seek to characterize the changes to the percent depth dose, tissue maximum ratio, relative dose factor, absolute dose calibration, off‐axis ratio, and the field width. We measured with the two‐voltage technique and represented as a linear function of the signal strength. This linear fit allows us to correct measurement sets when we have only gathered the high voltage signal and to correct derived quantities. The changes to dosimetric quantities can be up to 1.5%. Charge recombination significantly affects percent depth dose, tissue maximum ratio, and off‐axis ratio, but has minimal impact on the relative dose factor, absolute dose calibration, and field width.PACS number: 87.55.N‐
Optimal unified combination rule in application of Dempster‐Shafer theory to lung cancer radiotherapy dose response outcome analysis
Authors: He Yanyan , Hussaini M. Yousuff , Gong Yutao U. T. , Xiao Ying 
Published: February 2017

Our previous study demonstrated the application of the Dempster‐Shafer theory of evidence to dose/volume/outcome data analysis. Specifically, it provided Yager's rule to fuse data from different institutions pertaining to radiotherapy pneumonitis versus mean lung dose. The present work is a follow‐on study that employs the optimal unified combination rule, which optimizes data similarity among independent sources. Specifically, we construct belief and plausibility functions on the lung cancer radiotherapy dose outcome datasets, and then apply the optimal unified combination rule to obtain combined belief and plausibility, which bound the probabilities of pneumonitis incidence. To estimate the incidence of pneumonitis at any value of mean lung dose, we use the Lyman‐Kutcher‐Burman (LKB) model to fit the combined belief and plausibility curves. The results show that the optimal unified combination rule yields a narrower uncertainty range (as represented by the belief–plausibility range) than Yager's rule, which is also theoretically proven.PACS numbers: 87.55.dh, 87.55.dk
Pinnacle3 modeling and end‐to‐end dosimetric testing of a Versa HD linear accelerator with the Agility head and flattening filter‐free modes
Authors: Saenz Daniel L. , Narayanasamy Ganesh , Cruz Wilbert , Papanikolaou Nikos , Stathakis Sotirios 
Published: February 2017

The Elekta Versa HD incorporates a variety of upgrades to the line of Elekta linear accelerators, primarily including the Agility head and flattening filter‐free (FFF) photon beam delivery. The completely distinct dosimetric output of the head from its predecessors, combined with the FFF beams, requires a new investigation of modeling in treatment planning systems. A model was created in Pinnacle3 v9.8 with the commissioned beam data. A phantom consisting of several plastic water and Styrofoam slabs was scanned and imported into Pinnacle3, where beams of different field sizes, source‐to‐surface distances (SSDs), wedges, and gantry angles were devised. Beams included all of the available photon energies (6, 10, 18, 6 FFF, and 10 FFF MV), as well as the four electron energies commissioned for clinical use (6, 9, 12, and 15 MeV). The plans were verified at calculation points by measurement with a calibrated ionization chamber. Homogeneous and heterogeneous point‐dose measurements agreed within 2% relative to maximum dose for all photon and electron beams. AP photon open field measurements along the central axis at 100 cm SSD passed within 1%. In addition, IMRT testing was also performed with three standard plans (step and shoot IMRT, as well as a small‐ and large‐field VMAT plan). The IMRT plans were delivered on the Delta4 IMRT QA phantom, for which a gamma passing rate was for all plans with a 3% dose deviation, 3 mm distance‐to‐agreement, and 10% dose threshold. The IMRT QA results for the first 23 patients yielded gamma passing rates of . Such testing ensures confidence in the ability of Pinnacle3 to model photon and electron beams with the Agility head.PACS numbers: 87.55.D, 87.56.bd
Optimum location of external markers using feature selection algorithms for real‐time tumor tracking in external‐beam radiotherapy: a virtual phantom study
Authors: Nankali Saber , Torshabi Ahmad Esmaili , Miandoab Payam Samadi , Baghizadeh Amin 
Published: February 2017

In external‐beam radiotherapy, using external markers is one of the most reliable tools to predict tumor position, in clinical applications. The main challenge in this approach is tumor motion tracking with highest accuracy that depends heavily on external markers location, and this issue is the objective of this study. Four commercially available feature selection algorithms entitled 1) Correlation‐based Feature Selection, 2) Classifier, 3) Principal Components, and 4) Relief were proposed to find optimum location of external markers in combination with two “Genetic” and “Ranker” searching procedures. The performance of these algorithms has been evaluated using four‐dimensional extended cardiac‐torso anthropomorphic phantom. Six tumors in lung, three tumors in liver, and 49 points on the thorax surface were taken into account to simulate internal and external motions, respectively. The root mean square error of an adaptive neuro‐fuzzy inference system (ANFIS) as prediction model was considered as metric for quantitatively evaluating the performance of proposed feature selection algorithms. To do this, the thorax surface region was divided into nine smaller segments and predefined tumors motion was predicted by ANFIS using external motion data of given markers at each small segment, separately. Our comparative results showed that all feature selection algorithms can reasonably select specific external markers from those segments where the root mean square error of the ANFIS model is minimum. Moreover, the performance accuracy of proposed feature selection algorithms was compared, separately. For this, each tumor motion was predicted using motion data of those external markers selected by each feature selection algorithm. Duncan statistical test, followed by F‐test, on final results reflected that all proposed feature selection algorithms have the same performance accuracy for lung tumors. But for liver tumors, a correlation‐based feature selection algorithm, in combination with a genetic search algorithm, proved to yield best performance accuracy for selecting optimum markers.PACS numbers: 87.55.km, 87.56.Fc
Learning anatomy changes from patient populations to create artificial CT images for voxel‐level validation of deformable image registration
Authors: Yu Z. Henry , Kudchadker Rajat , Dong Lei , Zhang Yongbin , Court Laurence E. , Mourtada Firas , Yock Adam , Tucker Susan L. , Yang Jinzhong 
Published: February 2017

The purpose of this study was to develop an approach to generate artificial computed tomography (CT) images with known deformation by learning the anatomy changes in a patient population for voxel‐level validation of deformable image registration. Using a dataset of CT images representing anatomy changes during the course of radiation therapy, we selected a reference image and registered the remaining images to it, either directly or indirectly, using deformable registration. The resulting deformation vector fields (DVFs) represented the anatomy variations in that patient population. The mean deformation, computed from the DVFs, and the most prominent variations, which were captured using principal component analysis (PCA), composed an active shape model that could generate random known deformations with realistic anatomy changes based on those learned from the patient population. This approach was applied to a set of 12 head and neck patients who received intensity‐modulated radiation therapy for validation. Artificial planning CT and daily CT images were generated to simulate a patient with known anatomy changes over the course of treatment and used to validate the deformable image registration between them. These artificial CT images potentially simulated the actual patients' anatomies and also showed realistic anatomy changes between different daily CT images. They were used to successfully validate deformable image registration applied to intrapatient deformation.PACS number: 87.57.nj
SafetyNet: streamlining and automating QA in radiotherapy
Authors: Hadley Scott W. , Kessler Marc L. , Litzenberg Dale W. , Lee Choonik , Irrer Jim , Chen Xiaoping , Acosta Eduardo , Weyburne Grant , Keranen Wayne , Lam Kwok , Covington Elizabeth , Younge Kelly C. , Matuszak Martha M. , Moran Jean M. 
Published: February 2017

Proper quality assurance (QA) of the radiotherapy process can be time‐consuming and expensive. Many QA efforts, such as data export and import, are inefficient when done by humans. Additionally, humans can be unreliable, lose attention, and fail to complete critical steps that are required for smooth operations. In our group we have sought to break down the QA tasks into separate steps and to automate those steps that are better done by software running autonomously or at the instigation of a human. A team of medical physicists and software engineers worked together to identify opportunities to streamline and automate QA. Development efforts follow a formal cycle of writing software requirements, developing software, testing and commissioning. The clinical release process is separated into clinical evaluation testing, training, and finally clinical release. We have improved six processes related to QA and safety. Steps that were previously performed by humans have been automated or streamlined to increase first‐time quality, reduce time spent by humans doing low‐level tasks, and expedite QA tests. Much of the gains were had by automating data transfer, implementing computer‐based checking and automation of systems with an event‐driven framework. These coordinated efforts by software engineers and clinical physicists have resulted in speed improvements in expediting patient‐sensitive QA tests.PACS number(s): 87.55.Ne, 87.55.Qr, 87.55.tg, 87.55.tm