bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a deformable lung phantom for the evaluation of deformable registration
Authors: Chang Jina , Suh Tae‐Suk , Lee Dong‐Soo 
Published: February 2017

A deformable lung phantom was developed to simulate patient breathing motion and to evaluate a deformable image registration algorithm. The phantom consisted of an acryl cylinder filled with water and a latex balloon located in the inner space of the cylinder. A silicon membrane was attached to the inferior end of the phantom. The silicon membrane was designed to simulate a real lung diaphragm and to reduce motor workload. This specific design was able to reduce the use of metal, which may prevent infrared sensing of the real position management (RPM) gating system for four‐dimensional (4D) CT image acquisition. Verification of intensity based three‐dimensional (3D) demons deformable registration was based on the peak exhale and peak inhale breathing phases. The registration differences ranged from 0.60 mm to 1.11 mm and accuracy was determined according to inner target deformation. The phantom was able to simulate features and deformation of a real human lung and has the potential for wide application for 4D radiation treatment planning.PACS number: 87.57.Gg
Absorbed dose and dose rate using the Varian OBI 1.3 and 1.4 CBCT system
Authors: Palm Åsa , Nilsson Elisabeth , Herrnsdorf Lars 
Published: February 2017

According to published data, the absorbed dose used for a CBCT image acquisition with Varian OBI v1.3 can be as high as 100 mGy. In 2008 Varian released a new OBI version (v1.4), which promised to reduce the imaging dose. In this study, absorbed doses used for CBCT image acquisitions with the default irradiation techniques of Varian OBI v1.3 and v1.4 are measured.TLDs are used to derive dose distributions at three planes inside an anthropomorphic phantom. In addition, point doses and dose profiles inside a ‘stack’ of three CTDI body phantoms are measured using a new solid state detector, the CT Dose Profiler. With the CT Dose Profiler, the individual pulses from the X‐ray tube are also studied. To verify the absorbed dose measured with the CT Dose Profiler, it is compared to TLD. The image quality is evaluated using a Catphan phantom.For OBI v1.3, doses measured in transverse planes of the Alderson phantom range between 64 mGy and 144 mGy. The average dose is around 100 mGy. For OBI v1.4, doses measured in transverse planes of the Alderson phantom range between 1 mGy and 51 mGy. Mean doses range between 3‐35 mGy depending on CBCT mode. CT Dose Profiler data agree with TLD measurements in a CTDI phantom within the uncertainty of the TLD measurements (estimated SD ). Instantaneous dose rate at the periphery of the phantom can be higher than 20 mGy/s, which is 10 times the dose rate at the center. The spatial resolution in v1.4 is not as high as in v1.3.In conclusion, measurements show that the imaging doses for default modes in Varian OBI v1.4 CBCT system are significantly lower than in v1.3. The CT Dose Profiler is proven fast and accurate for CBCT applications.PACS number: 87.53.Bn
Validation of dosimetric field matching accuracy from proton therapy using a robotic patient positioning system
Authors: Farr Jonathan B. , O'Ryan‐Blair Avril , Jesseph Frederick , Hsi Wen‐Chien , Allgower Chris E. , Mascia Anthony E. , Thornton Allan F. , Schreuder Andreas N. 
Published: February 2017

Large area, shallow fields are well suited to proton therapy. However, due to beam production limitations, such volumes typically require multiple matched fields. This is problematic due to the relatively narrow beam penumbra at shallow depths compared to electron and photon beams. Therefore, highly accurate dose planning and delivery is required. As the dose delivery includes shifting the patient for matched fields, accuracy at the 1–2 millimeter level in patient positioning is also required. This study investigates the dosimetric accuracy of such proton field matching by an innovative robotic patient positioner system (RPPS). The dosimetric comparisons were made between treatment planning system calculations, radiographic film and ionization chamber measurements. The results indicated good agreement amongst the methods and suggest that proton field matching by a RPPS is accurate and efficient.PACS number: 87.55.km
Volume assessment accuracy in computed tomography: a phantom study
Authors: Prionas Nicolas D. , Ray Shonket , Boone John M. 
Published: February 2017

There is a broad push in the cancer imaging community to eventually replace linear tumor measurements with three‐dimensional evaluation of tumor volume. To evaluate the potential accuracy of volume measurement in tumors by CT, a gelatin phantom consisting of 55 polymethylmethacrylate (PMMA) spheres spanning diameters from 1.6 mm to 25.4 mm was fabricated and scanned using thin slice (0.625 mm) CT (GE LightSpeed 16). Nine different reconstruction combinations of field of view dimension and CT kernel (standard, lung, bone) were analyzed. Contiguous thin‐slice images were averaged to produce CT images with greater thicknesses (1.25, 2.50, 5.0 mm). Simple grayscale thresholding techniques were used to segment the PMMA spheres from the gelatin background, where a total of 1800 spherical volumes were evaluated across the permutations studied. The geometric simplicity of the phantom established upper limits on measurement accuracy. In general, smaller slice thickness and larger sphere diameters produced more accurate volume assessment than larger slice thickness and smaller sphere diameter. The measured volumes were smaller than the actual volumes by a common factor depending on slice thickness; overall, 0.625 mm slices produced on average 18%, 1.25 mm slices produced 22%, 2.5 mm CT slices produced 29%, and 5.0 mm slices produced 39% underestimates of volume (mm3). Field of view did not have a significant effect on volume accuracy. Reconstruction algorithm significantly affected volume accuracy , with the lung kernel having the smallest error, followed by the bone and standard kernels. The results of this investigation provide guidance for CT protocol development and may guide the development of more advanced techniques to promote quantitatively accurate CT volumetric analysis of tumors.PACS number: 87.57.Q‐
Study of a spherical phantom for Gamma knife dosimetry
Authors: Zhu Dengsong , Austerlitz Carlos , Benhabib Sidi , Mota Helvecio , Allison Ron R. , Campos Diana 
Published: February 2017

Four 16 cm diameter spherical phantoms were modeled in this study: a homogenous water phantom, and three water phantoms with 1 cm thick shell each made of different materials (PMMA, Plastic Water™ and polystyrene). The PENELOPE Monte Carlo code was utilized to simulate photon beams from the Leksell Gamma Knife (LGK) unit and to determine absorbed dose to water from a single 18 mm beam delivered to each phantom. A score spherical volume of 0.007 cm3 was used to simulate the dimensions of the sensitive volume of the Exradin A‐16 ionization chamber, in the center of the phantom. In conclusion, the PMMA shell filled with water required a small correction for the determination of the absorbed dose, while remaining within the statistical uncertainty of the calculations . Plastic Water™ and polystyrene shells can be used without correction. There is a potential advantage to measuring the 4 mm helmet output using these spherical water phantoms.PACS numbers: 87.10.Rt, 87.50.cm
Assessment and management of radiotherapy beam intersections with the treatment couch
Authors: van Prooijen Monique , Kanesalingam Thilakshan , Islam Mohammad K. , Heaton Robert K. 
Published: February 2017

The impact of the treatment couch on a radiotherapy plan is rarely fully assessed during the treatment planning process. Incorporating a couch model into the treatment planning system (TPS) enables the planner to avoid or dosimetrically evaluate beam‐couch intersections. In this work, we demonstrate how existing TPS tools can be used to establish this capability and assess the accuracy and effectiveness of the system through dose measurements and planning studies. Such capabilities may be particularly relevant for the planning of arc therapies.Treatment couch top models were introduced into a TPS by fusing their CT image sets with the patient CT dataset. Regions of interest characterizing couch elements were then imported and assigned appropriate densities in the TPS. Measurements in phantom agreed with TPS calculations to within 2% dose and 1° gantry rotation. To clinically validate the model, a retrospective study was performed on patient plans that posed difficulties in beam‐couch intersection during setup. Beam‐couch intersection caused up to a 3% reduction in PTV coverage, defined by the 95% of the prescribed dose, and up to a 1% reduction in mean CTV coverage. Dose compensation strategies for IMRT treatments with beams passing through couch elements were investigated using a four‐field IMRT plan with three beams passing through couch elements. In this study, ignoring couch effects resulted in point dose reductions of .A methodology for incorporating detailed couch characteristics into a TPS has been established and explored. The method can be used to predict beam‐couch intersections during planning, potentially eliminating the need for pretreatment appointments. Alternatively, if a beam‐couch intersection problem arises, the impact of the couch can be assessed on a case‐by‐case basis and a clinical decision made based on full dosimetric information.PACS numbers: 87.53.Bn;87.55.Gh;87.55.de;87.56.nk
Evaluation of a fast method of EPID‐based dosimetry for intensity‐modulated radiation therapy
Authors: Nelms Benjamin E. , Rasmussen Karl H. , Tomé Wolfgang A. 
Published: February 2017

Electronic portal imaging devices (EPIDs) could potentially be useful for intensity‐modulated radiation therapy (IMRT) QA. The data density, high resolution, large active area, and efficiency of the MV EPID make it an attractive option. However, EPIDs were designed as imaging devices, not dosimeters, and as a result they do not inherently measure dose in tissue equivalent media. EPIDose (Sun Nuclear, Melbourne, FL) is a tool designed for the use of EPIDs in IMRT QA that uses raw MV EPID images (no additional build‐up and independent of gantry angle, but with dark and flood field corrections applied) to estimate absolute dose planes normal to the beam axis in a homogeneous media (i.e. similar to conventional IMRT QA methods). However, because of the inherent challenges of the EPID‐based dosimetry, validating and commissioning such a system must be done very carefully, by exploring the range of use cases and using well‐proven “standards” for comparison. In this work, a multi‐institutional study was performed to verify accurate EPID image to dose plane conversion over a variety of conditions. Converted EPID images were compared to 2D diode array absolute dose measurements for 188 fields from 28 clinical IMRT treatment plans. These plans were generated using a number of commercially available treatment planning systems (TPS) covering various treatment sites including prostate, head and neck, brain, and lung. The data included three beam energies (6, 10, and 15 MV) and both step‐and‐shoot and dynamic MLC fields. Out of 26,207 points of comparison over 188 fields analyzed, the average overall field pass rate was 99.7% when DTA criteria were used (range 94.0–100 per field). The pass rates for more stringent criteria were 97.8% for DTA (range 82.0–100 per field), and 84.6% for DTA (range 54.7–100 per field). Individual patient‐specific sites as well, as different beam energies, followed similar trends to the overall pass rates.PACS number: 87.53.Dq; 87.66.Jj
Evaluation of the need for simultaneous orthogonal gated setup imaging
Authors: Berbeco Ross I. , Nishioka Seiko , Shirato Hiroki 
Published: February 2017

Image‐guided patient setup for respiratory‐gated radiotherapy often relies on a pair of respiratory‐gated orthogonal radiographs, acquired one after the other. This study quantifies the error due to changes in the internal/external correlation which may affect asynchronous (non‐simultaneous) imaging. The dataset from eight patients includes internal and external coordinates acquired at 30Hz during multi‐fraction SBRT treatments using the Mitsubishi RTRT system coupled with an external surrogate gating device. We performed a computational simulation of the position of an implanted fiducial marker in an asynchronous orthogonal image set. A comparison is made to the reference position, the actual 3D fiducial location at the initial time point, as would be obtainable by simultaneous orthogonal setup imaging at that time point. The time interval between the two simulated radiographic acquisitions was set to a minimum of 30, 60 or 90 seconds, based on our clinical experience. The setup position is derived from a combination of both the initial (AP) and the final (LR) simulated 2D images in the following way: . The 3D error is then the magnitude of the vector from the initial (reference) position to the setup position. The calculation was done for every exhale phase in the data for which there was another one at least 30, 60 or 90 seconds later, at an amplitude within 0.5 mm from the first. A correlation between the time interval and the 3D error was also sought. The mean 3D error is found to be roughly equivalent for time intervals of 30, 60 and 90 seconds between the orthogonal simulated images (0.8 mm, 0.8 mm, 0.6 mm, respectively). The 3D error is less than 1, 2 and 3 mm for 77%, 89% and 98% of the data points, respectively. The actual time between simulated images turned out to be very close to , with 90% of the second simulated image acquisitions being completed within 38, 68 and 95 seconds of the first simulated image for of 30, 60 and 90 seconds, respectively. No correlation was found between the length of the time interval and the 3D error. When acquiring respiratory‐gated radiographs for patient setup, only small errors should be expected if those images are not taken simultaneously.PACS number: 87.55.ne
Dosimetric performance of the new high‐definition multileaf collimator for intracranial stereotactic radiosurgery
Authors: Dhabaan Anees , Elder Eric , Schreibmann Eduard , Crocker Ian , Curran Walter J. , Oyesiku Nelson M. , Shu Hui‐Kuo , Fox Tim 
Published: February 2017

The objective was to evaluate the performance of a high‐definition multileaf collimator (MLC) of 2.5 mm leaf width () and compare to standard 5 mm leaf width MLC () for the treatment of intracranial lesions using dynamic conformal arcs (DCA) technique with a dedicated radiosurgery linear accelerator. Simulated cases of spherical targets were created to study solely the effect of target volume size on the performance of the two MLC systems independent of target shape complexity. In addition, 43 patients previously treated for intracranial lesions in our institution were retrospectively planned using DCA technique with and systems. The gross tumor volume ranged from 0.07 to with an average volume of . All treatment parameters were kept the same for both MLC‐based plans. The plan evaluation was performed using figures of merits (FOM) for a rapid and objective assessment on the quality of the two treatment plans for and . The prescription isodose surface was selected as the greatest isodose surface covering of the target volume and delivering 95% of the prescription dose to 99% of target volume. A Conformity Index (CI) and conformity distance index (CDI) were used to quantifying the dose conformity to a target volume. To assess normal tissue sparing, a normal tissue difference (NTD) was defined as the difference between the volume of normal tissue receiving a certain dose utilizing and the volume receiving the same dose using . The CI and normal tissue sparing for the simulated spherical targets were better with the as compared to . For the clinical patients, the CI and CDI results indicated that the provides better treatment conformity than even at large target volumes. The CI's range was 1.15 to 2.44 with a median of 1.59 for compared to 1.60–2.85 with a median of 1.71 for . Improved normal tissue sparing was also observed for over , with the NTD always positive, indicating improvement, and ranging from 0.1 to 8.3 for normal tissue receiving 50% (), 70% () and 90% () of the prescription dose. The has a dosimetric advantage over the in Linac‐based radiosurgery using DCA method for intracranial lesions, both in treatment conformity and normal tissue sparing when target shape complexity increases.PACS number: 87.56J‐, 87.56 jk
Suggesting a new design for multileaf collimator leaves based on Monte Carlo simulation of two commercial systems
Authors: Hariri Sanaz , Shahriari Majid 
Published: February 2017

Due to intensive use of multileaf collimators (MLCs) in clinics, finding an optimum design for the leaves becomes essential. There are several studies which deal with comparison of MLC systems, but there is no article with a focus on offering an optimum design using accurate methods like Monte Carlo. In this study, we describe some characteristics of MLC systems including the leaf tip transmission, beam hardening, leakage radiation and penumbra width for Varian and Elekta 80‐leaf MLCs using MCNP4C code. The complex geometry of leaves in these two common MLC systems was simulated. It was assumed that all of the MLC systems were mounted on a Varian accelerator and with a similar thickness as Varian's and the same distance from the source. Considering the obtained results from Varian and Elekta leaf designs, an optimum design was suggested combining the advantages of three common MLC systems and the simulation results of this proposed one were compared with the Varian and the Elekta. The leakage from suggested design is 29.7% and 31.5% of the Varian and Elekta MLCs. In addition, other calculated parameters of the proposed MLC leaf design were better than those two commercial ones. Although it shows a wider penumbra in comparison with Varian and Elekta MLCs, taking into account the curved motion path of the leaves, providing a double focusing design will solve the problem. The suggested leaf design is a combination of advantages from three common vendors (Varian, Elekta and Siemens) which can show better results than each one. Using the results of this theoretical study may bring about superior practical outcomes.PACS number: 87.56.nk, 87.55.K, 87.56.N
Evaluation of a commercially‐available block for spatially fractionated radiation therapy
Authors: Buckey Courtney , Stathakis Sotirios , Cashon Ken , Gutierrez Alonso , Esquivel Carlos , Shi Chengyu , Papanikolaou Nikos 
Published: February 2017

In this paper, we present the dosimetric characteristics of a commercially‐produced universal GRID block for spatially fractioned radiation therapy. The dosimetric properties of the GRID block were evaluated. Ionization chamber and film measurements using both Kodak EDR2 and Gafchromic EBT film were performed in a solid water phantom to determine the relative output of the GRID block as well as its spatial dosimetric characteristics. The surface dose under the block and at the openings was measured using ultra thin TLDs. After introducing the GRID block into the treatment planning system, a treatment plan was created using the GRID block and also by creating a GRID pattern using the multi‐leaf collimator. The percent depth doses measured with film showed that there is a shift of the towards shallower depths for both energies (6 MV and 18 MV) under investigation. It was observed that the skin dose at the GRID openings was higher than the corresponding open field by a factor as high as 50% for both photon energies. The profiles showed the transmission under the block was in the order of 15–20% for 6 MV and 30% for 18 MV. The MUs calculated for a real patient using the block were about 80% less than the corresponding MUs for the same plan using the multileaf collimator to define the GRID. Based on this investigation, this brass GRID compensator is a viable alternative to other solid compensators or MLC‐based fields currently in use. Its ease of creation and use give it decided advantages. Its ability to be created once and used for multiple patients (by varying the collimation of the linear accelerator jaws) makes it attractive from a cost perspective. We believe this compensator can be put to clinical use, and will allow more centers to offer GRID therapy to their patients.PACS number: 87.53.Mr
A dosimetric comparison of stereotactic body radiation therapy techniques for lung cancer: robotic versus conventional linac‐based systems
Authors: Ding Chuxiong , Chang Cheng‐Hui , Haslam Joshua , Timmerman Robert , Solberg Timothy 
Published: February 2017

The aim of this study is to compare the dosimetric characteristics of robotic and conventional linac‐based SBRT techniques for lung cancer, and to provide planning guidance for each modality. Eight patients who received linac‐based SBRT were retrospectively included in this study. A dose of 60 Gy given in three fractions was prescribed to each target. The Synchrony Respiratory Tracking System and a 4D dose calculation methodology were used for CyberKnife and linac‐based SBRT, respectively, to minimize respiratory impact on dose calculation. Identical image and contour sets were used for both modalities. While both modalities can provide satisfactory target dose coverage, the dose to GTV was more heterogeneous for CyberKnife than for linac planning/delivery in all cases. The dose to 1000 cc lung was well below institutional constraints for both modalities. In the high dose region, the lung dose depended on tumor size, and was similar between both modalities. In the low dose region, however, the quality of CyberKnife plans was dependent on tumor location. With anteriorly‐located tumors, the CyberKnife may deliver less dose to normal lung than linac techniques. Conversely, for posteriorly‐located tumors, CyberKnife delivery may result in higher doses to normal lung. In all cases studied, more monitor units were required for CyberKnife delivery for given prescription. Both conventional linacs and CyberKnife provide acceptable target dose coverage while sparing normal tissues. The results of this study provide a general guideline for patient and treatment modality selection based on dosimetric, tumor and normal tissue sparing considerations.PACS numbers: 87.53.Ly, 87.55.dk.