bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of Carbon-Neutral Residential Communities in Kuwait
Authors: Ameer Baqer , Krarti Moncef
Published: February 2017

In this paper, a general methodology for designing carbon-neutral residential communities is presented. Both energy efficiency measures and renewable energy technologies are considered in the design approach. First, energy end-uses for the buildings within the community are optimized based on a set of cost-effective energy efficiency measures that are selected based on a life-cycle cost analysis. Then, renewable energy technologies are considered to meet the energy needs for the residential community and ensure carbon-neutrality on an annual basis. The methodology is applied to design optimal and carbon-neutral hybrid electrical generation systems for three Kuwaiti residential communities with different sizes and energy efficiency designs. For Kuwait, it is found that wind turbines can cost-effectively generate significant electricity to meet most of the energy needs for the residential communities and thus reducing the country's reliance on fuel-based power plants. Specifically, it is found that wind turbines can generate electricity at a cost of $0.068/kWh well below the current grid power production costs of $0.103/kWh. Moreover, the analysis indicates that concentrated solar power (CSP) can be utilized to achieve carbon-neutral residential communities but at a levelized energy cost of $0.13/kWh slightly lower than the current grid power generation and distribution costs of $0.133/kWh.
A simple method to test geometrical reliability of digital reconstructed radiograph (DRR)
Authors: Pallotta Stefania , Bucciolini Marta
Published: February 2017

In radiotherapy treatment, portal images and digitally reconstructed radiographs (DRRs) are the most frequently used image‐guidance systems to monitor patient setup during clinical routine. DRR is therefore a critical element in the process of virtual simulation and patient position verification in radiotherapy. The aim of this work was to assess the geometric reliability of the DRR generated by XiO, Pinnacle, Odyssey and Oncentra Masterplan treatment planning systems (TPS). Instead of the computed tomography (CT) images of a quality assurance phantom, two synthetic phantoms were created and used to asses the linearity and the ray tracing reliability of the DRR generators. The obtained results demonstrate that the linearity and the reliability of DRR generators was less than 1 pixel for all TPSs.

PACS numbers: 87.55.D, 87.57.cp,87.57.nf
Evaluation of patient setup uncertainty of optical guided frameless system for intracranial stereotactic radiosurgery
Authors: Wang Jia‐Zhu , Rice Roger , Pawlicki Todd , Mundt Arno J. , Sandhu Ajay , Lawson Joshua , Murphy Kevin T.
Published: February 2017

The optically‐guided frameless system (OFLS) has been used in our clinic for intracranial stereotactic radiosurgery (SRS) since 2006, as it is especially effective in IMRT‐based radiosurgery (IMRS), which allows treating multiple brain lesions simultaneously using single isocenter approach. This study reports our retrospective analysis of patient setup accuracy using this system. The OFLS consists of a bite block with fiducial markers and an infra‐red camera system. To test reproducibility, patients are taken for reseat verification after bite block construction. Upon the completion of radiosurgery planning, the isocenter position(s) and images are sent to the optical guidance computer where fiducials are manually registered from the CT scan. During treatment, patient setup is monitored and guided by the camera readings on the fiducials. In addition, two orthogonal kV images are acquired and used as an isocenter verification tool. In addition, we have analyzed the reseat and fiducial digitization data of 56 patients. Retrospective comparison of kV images with reference images has been carried out for all the patients to evaluate actual patient setup accuracy at the time of treatment. The histogram of the findings shows that 82.2% of patients had 3D isodisplacement (; 5.2% had ). Hence, for 87.5 % of the patients in the study, treatments were finished under the optical guidance with a maximum setup error of 2 mm and the median setup error of 0 mm. For the remaining 12.5% of patients in the study, the isodisplacements were greater than 2 mm and the treatment records showed that those patients were repositioned, guided by the orthogonal kV‐images. It is found that the OFLS in the SRS treatment has acceptable accuracy when used in conjunction with orthogonal kV images, and the use of orthogonal kV images as a verification tool ensures the efficacy of frameless localization in the radiosurgery treatment.

PACS numbers: 87.53.Ly, 87.61.Tg, 87.55.Qr, 87.56.‐v, 29.20.Ej
Inverse planning optimization for hybrid prostate permanent‐seed implant brachytherapy plans using two source strengths
Authors: Cunha J. Adam M. , Pickett Barby , Pouliot Jean
Published: February 2017

The purpose is to demonstrate the ability to generate clinically acceptable prostate permanent seed implant plans using two seed types which are identical except for their activity. The IPSA inverse planning algorithms were modified to include multiple dose matrices for the calculation of dose from different sources, and a selection algorithm was implemented to allow for the swapping of source type at any given source position. Five previously treated patients with a range of prostate volumes from were re‐optimized under two hybrid scenarios: (1) using 0.32 and , and (2) using 0.64 and . Isodose lines were generated and dosimetric indices, , , , , , , and were calculated. The algorithm allows for the generation of single‐isotope, multi‐activity hybrid brachytherapy plans. By dealing with only one radionuclide, but of different activity, the biology is unchanged from a standard plan. All were within 2.3 percentage points for every plan and always above the clinically desirable 95%. All were identically zero, and is always below the clinically acceptable value of . Clinical optimization times for the hybrid plans are still under one minute, for most cases. It is possible to generate clinically advantageous brachytherapy plans (i.e. obtain the same quality dose distribution as a standard single‐activity plan) while incorporating leftover seeds from a previous patient treatment. This method will allow a clinic to continue to provide excellent patient care, but at a reduced cost. Multi‐activity hybrid plans were equal in quality (as measured by the standard dosimetric indices) to plans with seeds of a single activity. Despite the expanded search space, optimization times for these studies were still under two minutes on a modern day laptop and can be reduced to below one minute in a clinical setting. With the typical cost of a set of PPI seeds on the order of thousands of dollars, it is possible to reduce the cost of brachytherapy treatments by allowing for easier use of seeds left over from a previous patient or unused due to a cancelled treatment.

PACS number: 87.55.D‐, 87.55.Kd, 87.55.ne
Angular dependence of the output of a kilovoltage X‐ray therapy unit
Authors: Goharian Mehran , Nygren Ian , Tambasco Mauro , Barajas Jose Eduardo Villarreal
Published: February 2017

During the recommissioning of a Philips RT‐250 kilovoltage X‐ray unit, unexpected output variations with tube head rotation (cross‐plane) and tube head tilt (in‐plane) were observed. The measured output showed an increase of up to 7.3% relative to the neutral position (0° in‐plane and 0° cross‐plane) over the possible range of angles of in‐plane rotation for 75 kVp (half‐value layer, ). A less pronounced but noticeable output change (with respect to the neutral position) was observed for cross‐plane rotation reaching 2% for the 225 kVp beam (). This output variation was observed while manually adjusting the current to maintain constancy according to the current meter gauge. In order to address the observed output dependence with head orientation, the dose rate monitor chamber of the kilovoltage unit was calibrated to monitor the beam output in real time. The dose rate was manually adjusted to maintain a constant dose rate (in r/min) as displayed on the r/min gauge. This approach resulted in maintaining beam output for the 75 kVp and the 225 kVp beams within for the in‐plane angle variation and for the cross‐plane angle variation. A daily output check that includes ion chamber‐based measurements at the neutral position and an in‐plane angle of 45° has been implemented using the constant dose rate approach to monitor the stability of the X‐ray beams. As a result of the output variations with in/cross‐plane rotation, the quality control (QC) procedures that are typically used for clinical setup have been modified to test the stability of the beams under the non‐neutral positioning of the X‐ray tube.

PACS number: 87.56.Fc
Improved image quality of low‐dose thoracic CT examinations with a new postprocessing software
Authors: Martinsen Anne Catrine Traegde , Saether Hilde Kjernlie , Olsen Dag Rune , Wolff Per Aage , Skaane Per
Published: February 2017

In 2008 a phantom study indicated that there is a potential for reducing the CT doses when using a new postprocessing filter. The purpose of this study was to test this new postprocessing filter clinically for low‐dose chest CT examinations, to assess whether the diagnostic performance is the same or improved. A standardized clinical chest CT protocol was used on patients with colorectal cancer. Only mA settings changed between patients according to patient size. One standard and one low‐dose chest protocol were performed for all patients. The low‐dose images were postprocessed with a new software filter, which provides context‐controlled restoration of digital images by using adaptive filters. Three radiologists assessed randomly all the images independently. A total of 24 scan series were evaluated with respect to image quality according to quality criteria from the European guidelines for chest CT using a five‐point scale; 576 details were assessed. Overall mean score is the average score for all details rated for all three readers for all full‐dose series, low‐dose series and low‐dose enhanced series, respectively. The statistical methods used for comparison were paired sampled t‐test and intraclass correlation coefficient. The postprocessing filter improved the diagnostic performance compared to the unenhanced low‐dose images. Mean score for full‐dose, low‐dose and low‐dose enhanced series were 3.8, 3.0 and 3.3, respectively. For all patients the full‐dose series gave higher scores than the low‐dose series. Intraclass correlation coefficients were 0.2, 0.1 and 0.3 for the full‐dose, low‐dose and low‐dose enhanced series, respectively. There is a potential for improving diagnostic performance of low‐dose CT chest examinations using this new postprocessing filter.

PACS number: 87.57.C‐, 87.57.Q‐
Dosimetric comparison study between intensity modulated radiation therapy and three‐dimensional conformal proton therapy for pelvic bone marrow sparing in the treatment of cervical cancer
Authors: Song William Y. , Huh Soon N. , Liang Yun , White Greg , Nichols R. Charles , Watkins W. Tyler , Mundt Arno J. , Mell Loren K.
Published: February 2017

The objective was to compare intensity‐modulated radiation therapy (IMRT) with 3D conformal proton therapy (3DCPT) in the treatment of cervical cancer. In particular, each technique's ability to spare pelvic bone marrow (PBM) was of primary interest in this study. A total of six cervical cancer patients (3 postoperative and 3 intact) were planned and analyzed. All plans had uniform 1.0 cm CTV‐PTV margin and satisfied the 95% PTV with 100% isodose (prescription ) coverage. Dose‐volume histograms (DVH) were analyzed for comparison. The overall PTV and PBM volumes were cc and cc, respectively. In terms of PTV dose conformity index (DCI) and dose homogeneity index (DHI), 3DCPT was slightly superior to IMRT with , and , respectively. In addition, 3DCPT demonstrated superiority in reducing lower doses (i.e., V30 or less) to PBM, small bowel and bladder. Particularly in PBM, average V10 and V20 reductions of 10.8% and and 0.04), respectively, were observed. However, in the higher dose range, IMRT provided better sparing . For example, in small bowel and PBM, average reductions in V45 of 4.9% and and 0.008), respectively, were observed. Due to its physical characteristics such as low entrance dose, spread‐out Bragg peak and finite particle range of protons, 3DCPT illustrated superior target coverage uniformity and sparing of the lower doses in PBM and other organs. Further studies are, however, needed to fully exploit the benefits of protons for general use in cervical cancer.

PACS number: 87.55.D‐, 87.55.dk
A static multi‐slit collimator system for scatter reduction in cone‐beam CT
Authors: Chang Jina , Kim Siyong , Jang Doh‐Yun , Suh Tae‐Suk
Published: February 2017

A multiple‐slit collimator (MSC) design was introduced for scatter reduction in cone‐beam computed tomography (CBCT). Unlike most other collimators, the open and closed septa of the proposed MSC are placed in an equi‐angular interval on a circular track of the central sagittal plane. Therefore, one gantry rotation provides only the half of necessary dataset and two gantry rotations are needed to obtain full information. During the first gantry rotation, the MSC position relative to the source is fixed. For the second rotation, the MSC is rotated by the equi‐angle interval. We assume signals under the closed septa are totally attributed to scatter radiation. Then, scatter contributions under open septa are determined by interpolating them.

Monte Carlo (MC) simulations for two virtual phantoms (one with a simple geometry and the other with two heterogeneities simulating the bone and the lung) were performed to evaluate the effectiveness of the system. Using the method developed, we could obtain images with significant scatter reduction. Contrast ratio (CR) improvement factors were 1.165 in a 2D projection view, and 1.210 and 1.223 at the central and peripheral slice of the reconstructed CBCT image of the simple geometry phantom.

This preliminary study demonstrated that the proposed MSC, together with the imaging process technique, had a great potential to reduce scatter contribution in CBCT. Further studies will be performed to investigate the effect of various factors, such as reducing the detector size, increasing the number of history of MC simulation, and including many structures with different densities.

PACS number: 87.57.C
A quality assurance procedure to evaluate cone‐beam CT image center congruence with the radiation isocenter of a linear accelerator
Authors: Du Weiliang , Yang James N. , Chang Eric L. , Luo Dershan , McAleer Mary Frances , Shiu Almon , Martel Mary K.
Published: February 2017

A quality assurance (QA) procedure was developed to evaluate the congruence between the cone‐beam computed tomography (CBCT) image center and the radiation isocenter on a Varian Trilogy linac. In contrast to the published QA procedures, this method did not require a ball bearing (BB) phantom to be placed exactly at the radiation isocenter through precalibrated room lasers or light field crosshairs. The only requirement was that the BB phantom be in a stationary position near the radiation isocenter during the image acquisition process. The radiation isocenter was determined with respect to the center of the BB using a Winston‐Lutz test. The CBCT image center was found to have excellent short‐term positional reproducibility (i.e., less than 0.1 mm of wobble in each of the x (lateral), y (vertical), and z (longitudinal) directions) in 10 consecutive acquisitions. Measured over a seven‐month period, the CBCT image center deviated from the radiation isocenter by , and . The z displacement of the 3D CBCT image center was highly correlated with that of the 2D kV portal image center. The correlation coefficients in the x and y directions were poor ( and ‐0.35, respectively). Systematic discrepancies were found between the CBCT image center and the 2D MV, kV portal image centers. For the linear accelerator studied, we detected a 0.8 mm discrepancy between the CBCT image center and the MV EPID image center in the anterior‐posterior direction. This discrepancy was demonstrated in a clinical case study where the patient was positioned with CBCT followed by MV portal verification. The results from the new QA procedure are useful for guiding high‐precision patient positioning in stereotactic body radiation therapy.

PACS number: 87.55.Qr
Accurate positioning for head and neck cancer patients using 2D and 3D image guidance
Authors: Kang Hyejoo , Lovelock Dale M. , Yorke Ellen D. , Kriminiski Sergey , Lee Nancy , Amols Howard I.
Published: February 2017

Our goal is to determine an optimized image‐guided setup by comparing setup errors determined by two‐dimensional (2D) and three‐dimensional (3D) image guidance for head and neck cancer (HNC) patients immobilized by customized thermoplastic masks. Nine patients received weekly imaging sessions, for a total of 54, throughout treatment. Patients were first set up by matching lasers to surface marks (initial) and then translationally corrected using manual registration of orthogonal kilovoltage (kV) radiographs with DRRs (2D‐2D) on bony anatomy. A kV cone beam CT (kVCBCT) was acquired and manually registered to the simulation CT using only translations (3D‐3D) on the same bony anatomy to determine further translational corrections. After treatment, a second set of kVCBCT was acquired to assess intrafractional motion. Averaged over all sessions, 2D‐2D registration led to translational corrections from initial setup of (range 0–8) mm. The addition of 3D‐3D registration resulted in only small incremental adjustment (). We retrospectively calculated patient setup rotation errors using an automatic rigid‐body algorithm with 6 degrees of freedom (DoF) on regions of interest (ROI) of in‐field bony anatomy (mainly the C2 vertebral body). Small rotations were determined for most of the imaging sessions; however, occasionally rotations were observed. The calculated intrafractional motion with automatic registration was for eight patients, and for all patients. We conclude that daily manual 2D‐2D registration on radiographs reduces positioning errors for mask‐immobilized HNC patients in most cases, and is easily implemented. 3D‐3D registration adds little improvement over 2D‐2D registration without correcting rotational errors. We also conclude that thermoplastic masks are effective for patient immobilization.

PACS number: 87.53.Kn
Comparisons of multiple automated anatomy‐based image‐guidance methods for patient setup before head/neck external beam radiotherapy
Authors: Dogan Nesrin , Song Shiyu , Saleh Habeeb , Wu Jian , Murphy Martin J.
Published: February 2017

The purpose was to assess the variability in automated translational head/neck setup corrections computed from several different imaging modalities and rigid registration methods using patient anatomy. Shifts were calculated using three commercial and one in‐house automated rigid registration methods for nine head/neck patients who were imaged with three different image‐guidance systems. The mean difference between the daily isocenter shifts determined by the four methods ranged from 2.8 to 12.5 mm for all of the test cases. These differences are much greater than the variability observed for a rigid imaging phantom. Image‐guided setup procedures have an uncertainty that depends on the imaging modality, the registration algorithm, the image resolution and the image content. In the absence of an absolute ground truth, the variation in the shifts calculated by several different methods provides a useful estimate of that uncertainty.

PACS number: 87,55,km, 87.57.nj, 87.59.‐e, 87.59.bd
A monthly quality assurance procedure for 3D surface imaging
Authors: Wooten H. Omar , Klein Eric E. , Gokrhoo Garima , Santanam Lakshmi
Published: February 2017

A procedure for periodic quality assurance of a video surface imaging system is introduced. AlignRT is a video camera‐based patient localization system that captures and compares images of a patient's topography to a DICOM‐formatted external contour, then calculates shifts required to accurately reposition the patient. This technical note describes the tools and methods implemented in our department to verify correct and accurate operation of the AlignRT hardware and software components. The procedure described is performed monthly and complements a daily calibration of the system.

PACS number: 87.56Fc
Dose perturbation in the radiotherapy of breast cancer patients implanted with the Magna‐Site: a Monte Carlo study
Authors: Chatzigiannis Christos , Lymperopoulou Georgia , Sandilos Panagiotis , Dardoufas Constantinos , Yakoumakis Emmanouil , Georgiou Evaggelos , Karaiskos Pantelis
Published: February 2017

External beam radiation therapy (RT) is often offered to breast cancer patients after surgical mastectomy followed by breast reconstruction with silicone implants. In some cases, the RT is administered while the patient is still implanted with a temporary tissue expander including a high‐density metallic port, which is expected to affect the planned dose distribution.

This work uses Monte Carlo (MC) simulation in order to evaluate the aforementioned effect when the McGhan Style 133 Tissue Expander with the Magna‐Site injection port is used. Simulations have been performed on a patient model built using the actual CT images of the patient for two irradiation schemes, involving two tangential photon beams of 6 MV and 18 MV respectively. MC results show that the presence of the Magna‐Site within the two irradiation fields leads to an overall reduction of absorbed dose for points lying in the shadow of the metallic port (relative to each of the opposing beams). The relative reduction compared to dose results without the expander in place ranges from 7% to 13% for the 6 MV beam and is around 6% for the 18 MV photon beam. However, in the close vicinity of the metallic port, increased absorbed doses are observed, due to the increase of secondary electrons emerging from the metallic part of the insert.

PACS numbers: 87.53.Bn, 87.55.K‐, 29.20.‐c, 87.56.bd, 75.50.‐y
Comparison of four commercial devices for RapidArc and sliding window IMRT QA
Authors: Chandraraj Varatharaj , Stathakis Sotirios , Manickam Ravikumar , Esquivel Carlos , Supe Sanjay S. , Papanikolaou Nikos
Published: February 2017

For intensity‐modulated radiation therapy, evaluation of the measured dose against the treatment planning calculated dose is essential in the context of patient‐specific quality assurance. The complexity of volumetric arc radiotherapy delivery attributed to its dynamic and synchronization nature require new methods and potentially new tools for the quality assurance of such techniques. In the present study, we evaluated and compared the dosimetric performance of EDR2 film and three other commercially available quality assurance devices: IBA I'MatriXX array, PTW Seven29 array and the Delta4 array. The evaluation of these dosimetric systems was performed for RapidArc and IMRT deliveries using a Varian NovalisTX linear accelerator. The plans were generated using the Varian Eclipse treatment planning system. Our results showed that all four QA techniques yield equivalent results. All patient QAs passed our institutional clinical criteria of gamma index based on a 3% dose difference and 3 mm distance to agreement. In addition, the Bland‐Altman analysis was performed which showed that all the calculated gamma values of all three QA devices were within 5% from those of the film. The results showed that the four QA systems used in this patient‐specific IMRT QA analysis are equivalent. We concluded that the dosimetric systems under investigation can be used interchangeably for routine patient specific QA.

PACS numbers: 87.55.Qr, 87.56.Fc
Maximum kinetic energy considerations in proton stereotactic radiosurgery
Authors: Sengbusch Evan R. , Mackie Thomas R.
Published: February 2017

The purpose of this study was to determine the maximum proton kinetic energy required to treat a given percentage of patients eligible for stereotactic radiosurgery (SRS) with coplanar arc‐based proton therapy, contingent upon the number and location of gantry angles used. Treatment plans from 100 consecutive patients treated with SRS at the University of Wisconsin Carbone Cancer Center between June of 2007 and March of 2010 were analyzed. For each target volume within each patient, in‐house software was used to place proton pencil beam spots over the distal surface of the target volume from 51 equally‐spaced gantry angles of up to 360°. For each beam spot, the radiological path length from the surface of the patient to the distal boundary of the target was then calculated along a ray from the gantry location to the location of the beam spot. This data was used to generate a maximum proton energy requirement for each patient as a function of the arc length that would be spanned by the gantry angles used in a given treatment. If only a single treatment angle is required, 100% of the patients included in the study could be treated by a proton beam with a maximum kinetic energy of 118 MeV. As the length of the treatment arc is increased to 90°, 180°, 270°, and 360°, the maximum energy requirement increases to 127, 145, 156, and 179 MeV, respectively. A very high percentage of SRS patients could be treated at relatively low proton energies if the gantry angles used in the treatment plan do not span a large treatment arc. Maximum proton kinetic energy requirements increase linearly with size of the treatment arc.

PACS numbers: 87.55.‐x, 87.53.Ly, 87.53.Bn
Effectiveness of the single‐shot dual‐energy subtraction technique for portal images
Authors: Fujita Hideki , Morimi Sakon , Yamaguchi Michihiro , Fukuda Haruyuki , Murase Kenya
Published: February 2017

The aim of the present study was to evaluate the clinical efficacy of the single‐shot dual‐energy subtraction technique for obtaining portal images. We prepared two storage phosphor plates for this study. A 1 mm thick tungsten sheet was placed between the two storage phosphor plates. A single use of the double‐exposure technique provides two portal images simultaneously (i.e., a standard image and a low‐contrast image), using the same patient position and with no additional radiation delivered to the patient. A bone‐enhanced image is created by image subtraction between these two images. For evaluation of clinical efficacy, three treatment sites — the brain, lung, and pelvis — were imaged. Ten sets of images were obtained for each site, and five landmarks were selected for each treatment site. The visibility of each landmark and the ease of overall verification for the selected treatment sites were assessed separately for the standard and bone‐enhanced images. Four observers consisting of one radiation oncologist and three radiation therapists participated in the present study. For most of the landmarks studied, the bone‐enhanced images were significantly superior to the standard images. Regarding the ease of overall verification, the bone‐enhanced images were significantly superior to the standard images at all sites. The p‐values of mean rating for the brain, lung, and pelvis were 0.002, 0.012, and 0.003, respectively. The bone‐enhanced images obtained using our technique increased the image quality in terms of bone visibility, and are considered useful for routine clinical practice.

PACS number: 87.56.Da
Comparison of bulk electron density and voxel‐based electron density treatment planning
Authors: Karotki Aliaksandr , Mah Katherine , Meijer Gert , Meltsner Michael
Published: February 2017

The use of magnetic resonance imaging (MRI) alone for radiation planning is limited by the lack of electron density for dose calculations. The purpose of this work is to evaluate the dosimetric accuracy of using bulk electron density as a substitute for computed tomography (CT)‐derived electron density in intensity‐modulated radiation therapy (IMRT) treatment planning of head and neck (HN) cancers. Ten clinically‐approved, CT‐based IMRT treatment plans of HN cancer were used for this study. Three dose distributions were calculated and compared for each treatment plan. The first calculation used CT‐derived density and was assumed to be the most accurate. The second calculation used a homogeneous patient density of . For the third dose calculation, bone and air cavities were contoured and assigned a uniform density of and , respectively. The remaining tissues were assigned a density of . The use of homogeneous anatomy resulted in up to 4%–5% deviations in dose distribution as compared to CT‐derived electron density calculations. Assigning bulk density to bone and air cavities significantly improved the accuracy of the dose calculations. All parameters used to describe planning target volume coverage were within 2% of calculations based on CT‐derived density. For organs at risk, most of the parameters were within 2%, with the few exceptions located in low‐dose regions. The data presented here show that if bone and air cavities are overridden with the proper density, it is feasible to use a bulk electron density approach for accurate dose calculation in IMRT treatment planning of HN cancers. This may overcome the problem of the lack of electron density information should MRI‐only simulation be performed.

PACS number: 87.55.D‐
Evaluating and modeling of photon beam attenuation by a standard treatment couch
Authors: Hu Zhihui , Dai Jianrong , Li Liang , Cao Yin , Song Yixin , Fu Guishan
Published: February 2017

The purpose of this study was to evaluate beam attenuation by treatment couch and build a treatment couch model in TPS to check for beam–couch intersection at the planning stage and deal with beam attenuation by treatment couch in dose calculation. In this study, a standard treatment couch, Siemens ZXT couch, has been incorporated into 8.0 TPS, based on an existing TPS tool, model‐based segmentation (MBS). This was done by generating the couch's model from contours of the couch, together with the density information. Both the geometric and dosimetric accuracy of the couch model were evaluated. The test of beam–couch intersection prediction showed good agreement between predicted and measured results, and the differences were within 1° gantry rotation. For individual posterior oblique beams, the attenuation by metallic frames and PMMA couch top could reach nearly as high as 60% and 10%, respectively. For several posterior oblique beams (180°, 220°, 235°) that attenuated by the PMMA couch top, the calculated and measured dose distributions were compared. The dose differences at central axis were within 1%, and almost all points agreed with the calculations when the DD and DTA criteria of 3%/3 mm were adopted. The difference between calculated and measured attenuation factors were within 0.5%. This study demonstrates that the couch model created by MBS, which contains geometric and density information of the couch, can be used to detect the beam–couch intersection, and also is able to provide an accurate representation of the couch top attenuation properties in patient dose calculation.

PACS numbers: 87.55.D‐, 87.55.Gh, 87.55.km
Investigation of the feasibility of a simple method for verifying the motion of a binary multileaf collimator synchronized with the rotation of the gantry for helical tomotherapy
Authors: Hashimoto Masatoshi , Uematsu Masahiro , Ito Makiko , Hama Yukihiro , Inomata Takayuki , Fujii Masahiro , Nishio Teiji , Nakamura Naoki , Nakagawa Keiichi
Published: February 2017

In this paper, we suggest a new method for verifying the motion of a binary multileaf collimator (MLC) in helical tomotherapy. For this we used a combination of a cylindrical scintillator and a general‐purpose camcorder. The camcorder records the light from the scintillator following photon irradiation, which we use to track the motion of the binary MLC. The purpose of this study is to demonstrate the feasibility of this method as a binary MLC quality assurance (QA) tool. First, the verification was performed using a simple binary MLC pattern with a constant leaf open time; secondly, verification using the binary MLC pattern used in a clinical setting was also performed. Sinograms of simple binary MLC patterns, in which leaves that were open were detected as “open” from the measured light, define the sensitivity which, in this case, was 1.000. On the other hand, the specificity, which gives the fraction of closed leaves detected as “closed”, was 0.919. The leaf open error identified by our method was . The 68.6% of observed leaves were performed within relative error. The leaf open error was expressed by the relative errors calculated on the sinogram. In the clinical binary MLC pattern, the sensitivity and specificity were 0.994 and 0.997, respectively. The measurement could be performed with leaf open error. The 77.5% of observed leaves were performed within relative error. With this method, we can easily verify the motion of the binary MLC, and the measurement unit developed was found to be an effective QA tool.

PACS numbers: 87.56.Fc, 87.56.nk
Optimal parameters for clinical implementation of breast cancer patient setup using Varian DTS software
Authors: Ng Sook Kien , Zygmanski Piotr , Jeung Andrew , Mostafavi Hassan , Hesser Juergen , Bellon Jennifer R. , Wong Julia S. , Lyatskaya Yulia
Published: February 2017

Digital tomosynthesis (DTS) was evaluated as an alternative to cone‐beam computed tomography (CBCT) for patient setup. DTS is preferable when there are constraints with setup time, gantry‐couch clearance, and imaging dose using CBCT. This study characterizes DTS data acquisition and registration parameters for the setup of breast cancer patients using nonclinical Varian DTS software. DTS images were reconstructed from CBCT projections acquired on phantoms and patients with surgical clips in the target volume. A shift‐and‐add algorithm was used for DTS volume reconstructions, while automated cross‐correlation matches were performed within Varian DTS software. Triangulation on two short DTS arcs separated by various angular spread was done to improve 3D registration accuracy. Software performance was evaluated on two phantoms and ten breast cancer patients using the registration result as an accuracy measure; investigated parameters included arc lengths, arc orientations, angular separation between two arcs, reconstruction slice spacing, and number of arcs. The shifts determined from DTS‐to‐CT registration were compared to the shifts based on CBCT‐to‐CT registration. The difference between these shifts was used to evaluate the software accuracy. After findings were quantified, optimal parameters for the clinical use of DTS technique were determined. It was determined that at least two arcs were necessary for accurate 3D registration for patient setup. Registration accuracy of 2 mm was achieved when the reconstruction arc length was for clips with HU ; larger arc length () was required for very low HU clips. An optimal arc separation was found to be and optimal arc length was 10°. Registration accuracy did not depend on DTS slice spacing. DTS image reconstruction took 10–30 seconds and registration took less than 20 seconds. The performance of Varian DTS software was found suitable for the accurate setup of breast cancer patients. Optimal data acquisition and registration parameters were determined.

PACS numbers: 87.57.‐s, 87.57.nf, 87.57.nj
EPID dosimetry for pretreatment quality assurance with two commercial systems
Authors: Bailey Daniel W. , Kumaraswamy Lalith , Bakhtiari Mohammad , Malhotra Harish K. , Podgorsak Matthew B.
Published: February 2017

This study compares the EPID dosimetry algorithms of two commercial systems for pretreatment QA, and analyzes dosimetric measurements made with each system alongside the results obtained with a standard diode array. 126 IMRT fields are examined with both EPID dosimetry systems (EPIDose by Sun Nuclear Corporation, Melbourne FL, and Portal Dosimetry by Varian Medical Systems, Palo Alto CA) and the diode array, MapCHECK (also by Sun Nuclear Corporation). Twenty‐six VMAT arcs of varying modulation complexity are examined with the EPIDose and MapCHECK systems. Optimization and commissioning testing of the EPIDose physics model is detailed. Each EPID IMRT QA system is tested for sensitivity to critical TPS beam model errors. Absolute dose gamma evaluation (3%, 3 mm, 10% threshold, global normalization to the maximum measured dose) yields similar results (within 1%–2%) for all three dosimetry modalities, except in the case of off‐axis breast tangents. For these off‐axis fields, the Portal Dosimetry system does not adequately model EPID response, though a previously‐published correction algorithm improves performance. Both MapCHECK and EPIDose are found to yield good results for VMAT QA, though limitations are discussed. Both the Portal Dosimetry and EPIDose algorithms, though distinctly different, yield similar results for the majority of clinical IMRT cases, in close agreement with a standard diode array. Portal dose image prediction may overlook errors in beam modeling beyond the calculation of the actual fluence, while MapCHECK and EPIDose include verification of the dose calculation algorithm, albeit in simplified phantom conditions (and with limited data density in the case of the MapCHECK detector). Unlike the commercial Portal Dosimetry package, the EPIDose algorithm (when sufficiently optimized) allows accurate analysis of EPID response for off‐axis, asymmetric fields, and for orthogonal VMAT QA. Other forms of QA are necessary to supplement the limitations of the Portal Vision Dosimetry system.

PACS numbers: 87.53.Bn, 87.53.Jw, 87.53.Kn, 87.55.Qr, 87.56.Fc, 87.57.uq
Towards automated planning for unsealed source therapy
Authors: Schreibmann Eduard , Fox Tim
Published: February 2017

The purpose of this study was to develop and validate a technique for unsealed source radiotherapy planning that combines the segmentation and registration tasks of single‐photon emission tomography (SPECT) and computed tomography (CT) datasets. The segmentation task is automated by an atlas registration approach that takes advantage of a hybrid scheme using a diffeomorphic demons algorithm to warp a standard template to the patient's CT. To overcome the lack of common anatomical features between the CT and SPECT datasets, registration is achieved through a narrow band approach that matches liver contours in the CT with the gradients of the SPECT dataset. Deposited dose is then computed from the SPECT dataset using a convolution operation with tracer‐specific deposition kernels. Automatic segmentation showed good agreement with manual contouring, measured using the dice similarity coefficient and ranging from 0.72 to 0.87 for the liver, 0.47 to 0.93 for the kidneys, and 0.74 to 0.83 for the spinal cord. The narrow band registration achieved variations of less 0.5 mm translation and 1° rotation, as measured with convergence analysis. With the proposed combined segmentation–registration technique, the uncertainty of soft‐tissue target localization is greatly reduced, ensuring accurate therapy planning.

PACS number: 87.55.de, 87.55.kd
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