bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of interfractional variation of the breast surface following conventional patient positioning for whole‐breast radiotherapy
Authors: Padilla Laura , Kang Hyejoo , Washington Maxine , Hasan Yasmin , Chmura Steve J. , Al‐Hallaq Hania 
Published: February 2017

The purpose of this study was to quantify the variability of the breast surface position when aligning whole‐breast patients to bony landmarks based on MV portal films or skin marks alone. Surface imaging was used to assess the breast surface position of 11 whole‐breast radiotherapy patients, but was not used for patient positioning. On filmed fractions, AlignRT v5.0 was used to capture the patient's surface after initial positioning based on skin marks (28 “preshifts” surfaces), and after treatment couch shifts based on MV films (41 “postshifts” surfaces). Translations and rotations based on surface captures were recorded, as well as couch shifts based on MV films. For nonfilmed treatments, “daily” surface images were captured following positioning to skin marks alone. Group mean and systematic and random errors were calculated for all datasets. Pearson correlation coefficients, setup margins, and 95% limits of agreement (LOA) were calculated for preshifts translations and MV film shifts. LOA between postshifts surfaces and the filmed treatment positions were also computed. All the surface captures collected were retrospectively compared to both a DICOM reference surface created from the planning CT and to an AlignRT reference surface. All statistical analyses were performed using the DICOM reference surface dataset. AlignRT reference surface data was only used to calculate the LOA with the DICOM reference data. This helped assess any outcome differences between both reference surfaces. Setup margins for preshifts surfaces and MV films range between 8.3–12.0 mm and 5.4–13.4 mm, respectively. The largest margin is along the left–right (LR) direction for preshift surfaces, and along craniocaudal (CC) for films. LOA ranges between the preshifts surfaces and MV film shifts are large (12.6–21.9 mm); these decrease for postshifts surfaces (9.8–18.4 mm), but still show significant disagreements between the two modalities due to their focus on different anatomical landmarks (patient's topography versus bony anatomy). Pearson's correlation coefficients further support this by showing low to moderate correlations in the anterior–posterior (AP) and LR directions (0.47–0.69) and no correlation along . The use of an AlignRT reference surface compared to the DICOM reference surface does not significantly affect the LOA. Alignment of breast patients based solely on bony alignment may lead to interfractional inconsistencies in the breast surface position. The use of surface imaging tools highlights these discrepancies, and allows the radiation oncology team to better assess the possible effects on treatment quality.PACS number: 87
An improvement in IMRT QA results and beam matching in linacs using statistical process control
Authors: Gagneur Justin D. , Ezzell Gary A. 
Published: February 2017

The purpose of this study is to apply the principles of statistical process control (SPC) in the context of patient specific intensity‐modulated radiation therapy (IMRT) QA to set clinic‐specific action limits and evaluate the impact of changes to the multileaf collimator (MLC) calibrations on IMRT QA results. Ten months of IMRT QA data with 247 patient QAs collected on three beam‐matched linacs were retrospectively analyzed with a focus on the gamma pass rate (GPR) and the average ratio between the measured and planned doses. Initial control charts and action limits were calculated. Based on this data, changes were made to the leaf gap parameter for the MLCs to improve the consistency between linacs. This leaf gap parameter is tested monthly using a MLC sweep test. A follow‐up dataset with 424 unique QAs were used to evaluate the impact of the leaf gap parameter change. The initial data average GPR was 98.6% with an SPC action limit of 93.7%. The average ratio of doses was 1.003, with an upper action limit of 1.017 and a lower action limit of 0.989. The sweep test results for the linacs were , and from nominal. After the adjustment of the leaf gap parameter, all sweep test results were within 0.4% of nominal. Subsequently, the average GPR was 99.4% with an SPC action limit of 97.3%. The average ratio of doses was 0.997 with an upper action limit of 1.011 and a lower action limit of 0.981. Applying the principles of SPC to IMRT QA allowed small differences between closely matched linacs to be identified and reduced. Ongoing analysis will monitor the process and be used to refine the clinical action limits for IMRT QA.PACS number: 87.55.Qr
Radiation shielding evaluation based on five years of data from a busy CyberKnife center
Authors: Yang Jun , Feng Jing 
Published: February 2017

We examined the adequacy of existing shielding guidelines using five‐year clinical data from a busy CyberKnife center. From June 2006 through July 2011, 1,370 patients were treated with a total of 4,900 fractions and 680,691 radiation beams using a G4 CyberKnife. Prescription dose and total monitor units (MU) were analyzed to estimate the shielding workload and modulation factor. In addition, based on the beam's radiation source position, targeting position, MU, and beam collimator size, the MATLAB program was used to project each beam toward the shielding barrier. The summation of the projections evaluates the distribution of the shielding load. On average, each patient received 3.6 fractions, with an average 9.1 Gy per fraction prescribed at the 71.1% isodose line, using 133.7 beams and 6,200 MU. Intracranial patients received an average of 2.7 fractions, with 8.6 Gy per fraction prescribed at the 71.4% isodose line, using 133 beams and 5,083 MU. Extracranial patients received an average of 3.94 fractions, with 9.2 Gy per fraction prescribed at the 71% isodose line, using 134 beams and 6,514 MU. Most‐used collimator sizes for intracranial patients were smaller (7.5 to 20 mm) than for extracranial patients (20 to 40 mm). Eighty‐five percent of the beams exited through the floor, and about 40% of the surrounding wall area received no direct beam. For the rest of the wall, we found “hot” areas that received above‐average MU. The locations of these areas were correlated with the projection of the nodes for extracranial treatments. In comparison, the beam projections on the wall were more spread for intracranial treatments. The maximum MU any area received from intracranial treatment was less than 0.25% of total MU used for intracranial treatments, and was less than 1.2% of total MU used for extracranial treatments. The combination of workload, modulation factor, and use factor in our practice are about tenfold less than recommendations in the existing CyberKnife shielding guidelines. The current guidelines were found to be adequate for shielding, even in a busy center. There may be a potential to reduce shielding in areas with no or few direct beams in the current G4 model. Since a newer model CyberKnife (M6) has recently been introduced, the patterns of usage reported here may be changed in the future. The uneven distribution of use factor we have found may, however, be considered in the vault design.PACS number: 87.55.N
A retrospective tomotherapy image‐guidance study: analysis of more than 9,000 MVCT scans for ten different tumor sites
Authors: Sánchez‐Rubio Patricia , Rodríguez‐Romero Ruth , Castro‐Tejero Pablo 
Published: February 2017

The purpose of this study was to quantify the systematic and random errors for various disease sites when daily MVCT scans are acquired, and to analyze alternative off‐line verification protocols (OVP) with respect to the patient setup accuracy achieved. Alignment data from 389 patients (9,418 fractions) treated at ten different anatomic sites with daily image‐guidance (IG) on a helical tomotherapy unit were analyzed. Moreover, six OVP were retrospectively evaluated. For each OVP, the frequency of the residual setup errors and additional margins required were calculated for the treatment sessions without image guidance. The magnitude of the three‐dimensional vector displacement and its frequency were evaluated for all OVP. From daily IG, the main global systematic error was in the vertical direction (4.4–9.4 mm), and all rotations were negligible (less than 0.5°) for all anatomic sites. The lowest systematic and random errors were found for H&N and brain patients. All OVP were effective in reducing the mean systematic error to less than 1 mm and 0.2° in all directions and roll corrections for almost all treatment sites. The treatment margins needed to adapt the residual errors should be increased by 2–5 mm for brain and H&N, around 8 mm in the vertical direction for the other anatomic sites, and up to 19 mm in the longitudinal direction for abdomen patients. Almost 70% of the sessions presented a setup error of 3 mm for OVPs with an imaging frequency above 50%. Only for brain patients it would be feasible to apply an OVP because the residual setup error could be compensated for with a slight margin increase. However, daily imaging should be used for anatomic sites of difficult immobilization and/or large interfraction movement.PACS numbers: 87.55.‐x, 87.56.‐v
Using a 2D detector array for meaningful and efficient linear accelerator beam property validations
Authors: Ritter Timothy A. , Gallagher Ian , Roberson Peter L. 
Published: February 2017

Following linear accelerator commissioning, the qualified medical physicist is responsible for monitoring the machine's ongoing performance, detecting and investigating any changes in beam properties, and assessing the impact of unscheduled repairs. In support of these responsibilities, the authors developed a method of using a 2D ionization chamber array to efficiently test and validate important linear accelerator photon beam properties. A team of three physicists identified critical properties of the accelerator and developed constancy tests that were sensitive to each of the properties. The result was a 14‐field test plan. The test plan includes large and small fields at varying depths, a reduced SSD field at shallow depth for sensitivity to extra focal photon and electron components, and analysis of flatness, symmetry, dose, dose profiles, and dose ratios. Constancy tests were repeated five times over a period of six weeks and used to set upper and lower investigation levels at SDs. Deliberate variations in output, penumbra, and energy were tested to determine the suitability of the proposed method. Measurements were also performed on a similar, but distinct, machine to assess test sensitivity. The results demonstrated upper and lower investigation levels significantly smaller than the comparable TG‐142 annual recommendations, with the exception of the surrogate used for output calibration, which still fell within the TG‐142 monthly recommendation. Subtle changes in output, beam energy, and penumbra were swiftly identified for further investigation. The test set identified the distinct nature of the second accelerator. The beam properties of two photon energies can be validated in approximately 1.5 hrs using this method. The test suite can be used to evaluate the impact of minor repairs, detect changes in machine performance over time, and supplement other machine quality assurance testing.PACS numbers: 87.56bd, 87.56Fc
Retrospective evaluation of CTV to PTV margins using CyberKnife in patients with thoracic tumors
Authors: Floriano Alejandro , García Rafael , Moreno Ramón , Sánchez‐Reyes Alberto 
Published: February 2017

The objectives of this study were to estimate global uncertainty for patients with thoracic tumors treated in our center using the CyberKnife VSI after placement of fiducial markers and to compare our findings with the standard CTV to PTV margins used to date. Datasets for 16 patients (54 fractions) treated with the CyberKnife and the Synchrony Respiratory Tracking System were analyzed retrospectively based on CT planning, tracking information, and movement data generated and saved in the logs files by the system. For each patient, we analyzed all the main uncertainty sources and assigned a value. We also calculated an expanded global uncertainty to ensure a robust estimation of global uncertainty and to enable us to determine the position of 95% of the CTV points with a 95% confidence level during treatment. Based on our estimation of global uncertainty and compared with our general margin criterion (5 mm in all three directions: superior/inferior [SI], anterior/posterior [AP], and lateral [LAT]), 100% were adequately covered in the LAT direction, as were 94% and 94% in the SI and AP directions. We retrospectively analyzed the main sources of uncertainty in the CyberKnife process patient by patient. This individualized approach enabled us to estimate margins for patients with thoracic tumors treated in our unit and compare the results with our standard 5 mm margin.PACS number: 87.55‐x
Towards a paperless medical physics residency management system
Authors: Schubert Leah K. , Miften Moyed 
Published: February 2017

Documentation is a required component of a residency program, but can be difficult to collect and disseminate, resulting in minimal utilization by residents and faculty. The purpose of this work is to adapt a commercially‐available Web‐based medical residency management system to improve the learning experience by efficiently distributing program information, documenting resident activities, and providing frequent monitoring and timely feedback of resident progress. To distribute program information, program requirements and rotation readings were uploaded. An educational conference calendar was created with associated files and attendance records added. To document resident progress, requirements for over 37 different clinical procedures were added, for which the resident logged the total number of procedures performed. Progress reports were created and automatically distributed. To provide feedback to the resident, an extensive electronic evaluation system was created. Results are shown for the initial 21 months of program existence, consisting of a single resident for the first 12 months and two residents for the subsequent 9 months. The system recorded that 130 documents were uploaded and 100% of required documents were downloaded by the resident. In total, 385 educational conferences and meetings were offered, of which the residents attended 95%. The second‐year and first‐year residents logged 1030 and 522 clinical procedures, respectively. The residents submitted a total of 116 status reports detailing weekly activities, 100% of which were reviewed by faculty within an average of 11.3 days. A total of 65 evaluations of the residents were submitted. The residents reviewed 100% of respective evaluations within an average of 1.5 days. We have successfully incorporated a paperless, Web‐based management system in a medical physics residency program. A robust electronic documentation system has been implemented, which has played a central role in enhancing the training experience.PACS number: 01
Development of image quality assurance measures of the ExacTrac localization system using commercially available image evaluation software and hardware for image‐guided radiotherapy
Authors: Stanley Dennis N. , Papanikolaou Nikos , Gutierrez Alonso N. 
Published: February 2017

Quality assurance (QA) of the image quality for image‐guided localization systems is crucial to ensure accurate visualization and localization of target volumes. In this study, a methodology was developed to assess and evaluate the constancy of the high‐contrast spatial resolution, dose, energy, contrast, and geometrical accuracy of the BrainLAB ExacTrac system. An in‐house fixation device was constructed to hold the QCkV‐1 phantom firmly and reproducibly against the face of the flat panel detectors. Two image sets per detector were acquired using ExacTrac preset console settings over a period of three months. The image sets were analyzed in PIPSpro and the following metrics were recorded: high‐contrast spatial resolution ( (lp/mm)), noise, and contrast‐to‐noise ratio. Geometrical image accuracy was evaluated by assessing the length between to predetermined points of the QCkV‐1 phantom. Dose and kVp were recorded using the Unfors RaySafe Xi R/F Detector. The kVp and dose were evaluated for the following: Cranial Standard (CS) (80 kV,80 mA,80 ms), Thorax Standard (TS) (120 kV,160 mA,160 ms), Abdomen Standard (AS) (120 kV,160 mA,130 ms), and Pelvis Standard (PS) (120 kV,160 mA,160 ms). With regard to high‐contrast spatial resolution, the mean values of the (lp/mm), (lp/mm) and (lp/mm) for the left detector were , and , respectively, while for the right detector they were , and , respectively. Mean CNRs for the left and right detectors were and , respectively. For geometrical accuracy, both detectors had a measured image length of the QCkV‐1 of . The left detector showed dose measurements of , , , and , while the right detector showed , , , and , respectively. For X‐ray energy, the left detector (right X‐ray tube) had mean kVp readings of , , , and , and the right detector (left X‐ray tube) had , , , and . Run charts were created so that each parameter could be tracked over time and the constancy of the system could be monitored. A methodology was developed to assess the basic image quality parameters recommended by TG‐142 for the ExacTrac system. The ExacTrac system shows a consistent dose, kVp, high‐contrast spatial resolution, CNR, and geometrical accuracy for each detector over the evaluated timeframe.PACS number: 87.10.‐e
Monte Carlo‐based beam quality and phantom scatter corrections for solid‐state detectors in and brachytherapy dosimetry
Authors: Subhalaxmi Mishra , Selvam T. Palani 
Published: February 2017

Beam quality correction, , for solid‐state detectors diamond, LiF, , and plastic scintillator are calculated as a function of distance, r, along the transverse axis of the and brachytherapy sources using the Monte Carlo‐based EGSnrc code system. This study also includes calculation of detector‐specific phantom scatter correction, , for solid phantoms such as PMMA, polystyrene, solid water, virtual water, plastic water, RW1, RW3, A150, and WE210. For source, is about unity and distance‐independent for diamond, plastic scintillator, and LiF detectors. For this source, decreases gradually with r for detector (about 6% smaller than unity at 15 cm). For source, is about unity and distance‐independent for detector (overall variation is about 1% in the distance range of 1–15 cm). For this source, increases with r for diamond and plastic scintillator (about 6% and 8% larger than unity at 15 cm, respectively). Whereas decreases with r gradually for LiF (about 4% smaller than unity at 15 cm) and steeply for (about 25% smaller than unity at 15 cm). For source, solid water, virtual water, RW1, RW3, and WE210 phantoms are water‐equivalent for all the investigated solid‐state detectors. Whereas polystyrene and plastic water phantoms are water‐equivalent for diamond, plastic scintillator, and LiF detectors, but show distance‐dependent values for detector. PMMA phantom is water‐equivalent at all distances for detector, but shows distance‐dependent values for remaining detectors. A150 phantom shows distance‐dependent values for all the investigated detector materials. For source, solid water, virtual water, RW3, and WE210 phantoms are water‐equivalent for diamond, plastic scintillator, and LiF detectors, but show distance‐dependent values for detector. All other phantoms show distance‐dependent values for all the detector materials.PACS numbers: 87.10.Rt, 87.53.Bn, 87.53.Jw
Performance evaluation of a newly developed high‐resolution, dual‐head animal SPECT system based on the NEMA NU1–2007 standard
Authors: Moji Vahideh , Zeraatkar Navid , Farahani Mohammad Hossein , Aghamiri Mahmood Reza , Sajedi Salar , Teimourian Behnoosh , Ghafarian Pardis , Sarkar Saeed , Ay Mohammad Reza 
Published: February 2017

Small‐animal single‐photon emission computed tomography (SPECT) system plays an important role in the field of drug development and investigation of potential drugs in the preclinical phase. The small‐animal High‐Resolution SPECT (HiReSPECT) scanner has been recently designed and developed based on compact and high‐resolution detectors. The detectors are based on a high‐resolution parallel hole collimator, a cesium iodide (sodium‐activated) pixelated crystal array and two H8500 position‐sensitive photomultiplier tubes. In this system, a full set of data corrections such as energy, linearity, and uniformity, together with resolution recovery option in reconstruction algorithms, are available. In this study, we assessed the performance of the system based on NEMA‐NU1–2007 standards for pixelated detector cameras. Characterization of the HiReSPECT was performed by measurement of the physical parameters including planar and tomographic performance. The planar performance of the system was characterized with flood‐field phantom for energy resolution and uniformity. Spatial resolution and sensitivity were evaluated as functions of distance with capillary tube and cylindrical source, respectively. Tomographic spatial resolution was characterized as a function of radius of rotation (ROR). A dedicated hot rod phantom and image quality phantom was used for the evaluation of overall tomographic quality of the HiReSPECT. The results showed that the planar spatial resolution was and in terms of full‐width at half‐maximum (FWHM) along short‐ and long‐axis dimensions, respectively, when the source was placed on the detector surface. The integral uniformity of the system after uniformity correction was 1.7% and 1.2% in useful field of view (UFOV) and central field of view (CFOV), respectively. System sensitivity on the collimator surface was and didn't vary significantly with distance. Mean tomographic spatial resolution was measured mm FWHM at the radius of rotation of 25 mm with dual‐head configuration.The measured performance demonstrated that the HiReSPECT scanner has acceptable image quality and, hence, is well suited for preclinical molecular imaging research.PACS number: 87.57.U