bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calibration coefficients of dosimeters used in mammography for various target/filter combinations
Authors: Sekimoto Michiharu , Katoh Yoh , Katoh Tsuguhisa 
Published: February 2017

A wide variety of existing combinations of target and filter materials (target/filter combinations) are used in mammography equipment. The patient dose depends on the X‐ray quality that is derived from the target/filter combination, and a calibration of the dosimeter that is used in the measurement that corresponds to the specific target/filter combination is necessary. However, dosimeters in mammography are generally calibrated with reference to the X‐ray quality of Mo/Mo or W/Al combinations, and it is unclear whether or not the X‐ray quality that is derived from other target/filter combinations will affect the calibration coefficients. In this paper, the calibration coefficients of different dosimeters were evaluated for target/filter combinations. For an ionization chamber‐type dosimeter, good energy dependence was found and the effect of the target/filter combination was small. However, for a semiconductor dosimeter, a large energy dependence was found, and different calibration coefficients that depended on the target/filter combination used were required.PACS number: 87.59.E‐
Episcleral eye plaque dosimetry comparison for the Eye Physics EP917 using Plaque Simulator and Monte Carlo simulation
Authors: Zimmermann Leonard W. , Amoush Ahmad , Wilkinson Douglas A. 
Published: February 2017

This work is a comparative study of the dosimetry calculated by Plaque Simulator, a treatment planning system for eye plaque brachytherapy, to the dosimetry calculated using Monte Carlo simulation for an Eye Physics model EP917 eye plaque. Monte Carlo (MC) simulation using MCNPX 2.7 was used to calculate the central axis dose in water for an EP917 eye plaque fully loaded with 17 IsoAid Advantage seeds. In addition, the dosimetry parameters , and were calculated for the IsoAid Advantage model IAI‐125 seed and benchmarked against published data. Bebig Plaque Simulator (PS) v5.74 was used to calculate the central axis dose based on the AAPM Updated Task Group 43 (TG‐43U1) dose formalism. The calculated central axis dose from MC and PS was then compared. When the MC dosimetry parameters for the IsoAid Advantage seed were compared with the consensus values, Λ agreed with the consensus value to within 2.3%. However, much larger differences were found between MC calculated gL(r) and and the consensus values. The differences between MC‐calculated dosimetry parameters are much smaller when compared with recently published data. The differences between the calculated central axis absolute dose from MC and PS ranged from 5% to 10% for distances between 1 and 12 mm from the outer scleral surface. When the dosimetry parameters for the seed from this study were used in PS, the calculated absolute central axis dose differences were reduced by 2.3% from depths of 4 to 12 mm from the outer scleral surface. We conclude that PS adequately models the central dose profile of this plaque using its defaults for the IsoAid model IAI‐125 at distances of 1 to 7 mm from the outer scleral surface. However, improved dose accuracy can be obtained by using updated dosimetry parameters for the IsoAid model IAI‐125 seed.PACS number: 87.55.K‐
Determination of using MLC‐collimated rectangular fields for absolute dosimetry of the CyberKnife
Authors: Gersh Jacob A. , Willett Benjamin 
Published: February 2017

Traditional CyberKnife (CK) calibration uses TG‐51, which requires to be defined using the standard reference condition of 100 cm SSD in a field. Since the CK is calibrated using a 6 cm fixed‐aperture collimating cone at 80 cm SAD, the BJR‐25 method is commonly used to relate circular‐field PDDs to square‐field PDDs for determination. Using the InCise MLC system, the CK is able to deliver rectangular fields, allowing a more direct measurement of using conventional reference conditions. We define the PDD correction factor () as the ratio of measured using CK reference conditions to that measured using standard TG‐51 reference conditions. Using four ionization chambers (A1SL, CC08, CC13, and A19), is measured using a 6 cm fixed cone at 80 cm SSD and at 100 cm SSD using an effective MLC‐collimated field. These values are used to calculate , while the latter is used to directly calculate a value. This direct value is then compared to values determined using the BJR‐25 method. Using the MLC system, this study demonstrates conversion between the measured using CyberKnife reference conditions and TG‐51 reference conditions. These values provide the means for derivation of a curve as a function of direct measurements of using a 6 cm fixed‐aperture collimating cone at 80 cm SSD.PACS number: 87.55.Qr
Effect of electron contamination on in vivo dosimetry for lung block shielding during TBI
Authors: Narayanasamy Ganesh , Cruz Wilbert , Saenz Daniel L. , Stathakis Sotirios , Papanikolaou Niko , Kirby Neil 
Published: February 2017

Our institution performs in vivo verification measurement for each of our total body irradiation (TBI) patients with optically stimulated luminescent dosimeters (OSLD). The lung block verification measurements were commonly higher than expected. The aim of this work is to understand this discrepancy and improve the accuracy of these lung block verification measurements. Initially, the thickness of the lung block was increased to provide adequate lung sparing. Further tests revealed the increase was due to electron contamination dose emanating from the lung block. The thickness of the bolus material covering the OSLD behind the lung block was increased to offset the electron contamination. In addition, the distance from the lung block to the dosimeter was evaluated for its effect on the OSLD reading and found to be clinically insignificant over the range of variability in our clinic. The results show that the improved TBI treatment technique provides for better accuracy of measured dose in vivo and consistency of patient setup.PACS number(s): 87.53.Bn, 87.53.Kn, 87.55.N‐, 87.55.Qr
Two‐year experience with the commercial Gamma Knife Check software
Authors: Xu Andy (Yuanguang) , Bhatnagar Jagdish , Bednarz Greg , Novotny Josef , Flickinger John , Lunsford L. Dade , Huq M. Saiful 
Published: February 2017

The Gamma Knife Check software is an FDA approved second check system for dose calculations in Gamma Knife radiosurgery. The purpose of this study was to evaluate the accuracy and the stability of the commercial software package as a tool for independent dose verification. The Gamma Knife Check software version 8.4 was commissioned for a Leksell Gamma Knife Perfexion and a 4C unit at the University of Pittsburgh Medical Center in May 2012. Independent dose verifications were performed using this software for 319 radiosurgery cases on the Perfexion and 283 radiosurgery cases on the 4C units. The cases on each machine were divided into groups according to their diagnoses, and an averaged absolute percent dose difference for each group was calculated. The percentage dose difference for each treatment target was obtained as the relative difference between the Gamma Knife Check dose and the dose from the tissue maximum ratio algorithm (TMR 10) from the GammaPlan software version 10 at the reference point. For treatment plans with imaging skull definition, results obtained from the Gamma Knife Check software using the measurement‐based skull definition method are used for comparison. The collected dose difference data were also analyzed in terms of the distance from the treatment target to the skull, the number of treatment shots used for the target, and the gamma angles of the treatment shots. The averaged percent dose differences between the Gamma Knife Check software and the GammaPlan treatment planning system are 0.3%, 0.89%, 1.24%, 1.09%, 0.83%, 0.55%, 0.33%, and 1.49% for the trigeminal neuralgia, acoustic neuroma, arteriovenous malformation (AVM), meningioma, pituitary adenoma, glioma, functional disorders, and metastasis cases on the Perfexion unit. The corresponding averaged percent dose differences for the 4C unit are 0.33%, 1.2%, 2.78% 1.99%, 1.4%, 1.92%, 0.62%, and 1.51%, respectively. The dose difference is, in general, larger for treatment targets in the peripheral regions of the skull owing to the difference in the numerical methods used for skull shape simulation in the GammaPlan and the Gamma Knife Check software. Larger than 5% dose differences were observed on both machines for certain targets close to patient skull surface and for certain targets in the lower half of the brain on the Perfexion, especially when shots with 70 and/or 110 gamma angles are used. Out of the 1065 treatment targets studied, a 5% cutoff criterion cannot always be met for the dose differences between the studied versions of the Gamma Knife Check software and the planning system for 40 treatment targets.PACS number(s): 87.55.Qr, 87.56.Fc
A report from the AAPM Subcommittee on Guidelines for Competency Evaluation for Clinical Medical Physicists in Radiation Oncology
Authors: Pavord Daniel C. , Birnbaum Steven , Boccuzzi Douglas , deBoer Steven , Freedman D. Jay , Schell Michael , Sutlief Steven 
Published: February 2017

The goal of this report is to provide a framework from which an institution can develop a competency and credentialing program. It is not intended to be adopted as written, but rather as a list of suggestions from which the institution develops their program. A clear distinction should be made between the initial evaluation of the competency of new staff (credentialing) and the ongoing verification of the competency of existing staff. Furthermore, whenever new technologies are implemented, the entire staff would be subject to the credentialing process. Competencies involve the ongoing verification of the performance of a procedure according to the established policies and procedures at a facility. This can be done by audits of work product, direct observation of performance, self‐evaluation, or testing.PACS number(s): 87.10.‐e, 87.90.+y
Analysis of setup error based on CTVision for nasopharyngeal carcinoma during IGRT
Authors: Zhang Shuxu , Zhou Xiang , Zhang Quanbin , Jiang Shaohui , Wang Ruihao , Zhang Guoqian , Lei Huaiyu , Lin Shengqu 
Published: February 2017

The aim of the present study was to investigate the role of CTVision in interfractional setup errors during intensity‐modulated radiation therapy (IMRT) in 12 nasopharyngeal carcinoma (NPC) patients. The trend of setup errors as a function of time during a fractionated radiotherapy course was investigated, and the influence of reconstructive thickness on image reconstruction for setup errors was analyzed. The appropriate planning target volume (PTV) margin and planning risk volume (PRV) margin were defined to provide a reference for the design of IMRT for NPC. Based on CTVision, online CT was performed weekly for each patient. Setup errors were measured by registration between the CT reconstructed image and reference image. Mean of setup errors, estimated population systematic (:), and population random (σ) errors were calculated using SPSS (v15.0). Optimum PTV and PRV margins were calculated. In the clinical data, for the LR (left–right), SI (superior–inferior), and AP (anterior–posterior) directions, : was 0.8, 0.8, and 1.0 mm, respectively, and σ was 1.0, 1.3, and 0.8 mm, respectively. In the LR, SI, and AP directions, PTV margins were at least 2.7, 2.9, and 3.0 mm, respectively, and PRV margins were at least 1.5, 1.7, and 1.7 mm, respectively. No significant differences in setup errors were observed during the fractionated radiotherapy course . However, CT image reconstruction with different thicknesses affected the accuracy of measurements for setup errors, particularly in the SI direction. The application of CTVision to correct setup errors is important and can provide reasonable margins to guarantee the coverage of PTVs and spare organs at risk. A thickness of 3 mm in the reconstructed image is appropriate for the measurement of setup errors by image registration.PACS number(s): 87.55.Qr
Low‐dose 2.5 MV cone‐beam computed tomography with thick CsI flat‐panel imager
Authors: Tang Grace , Moussot Christopher , Morf Daniel , Seppi Edward , Amols Howard 
Published: February 2017

Most of the treatment units, both new and old models, are equipped with a megavoltage portal imager but its use for volumetric imaging is limited. This is mainly due to the poor image quality produced by the high‐energy treatment beam ( MV). A linac at our center is equipped with a prototype 2.5 MV imaging beam. This study evaluates the feasibility of low‐dose megavoltage cone‐beam imaging with the 2.5 MV beam and a thick cesium iodide detector, which is a high‐efficiency imager. Basic imaging properties such as spatial resolution and modulation transfer function were assessed for the 2.5 MV prototype imaging system. For image quality and imaging dose, a series of megavoltage cone‐beam scans were acquired for the head, thorax, and pelvis of an anthropomorphic phantom and were compared to kilovoltage cone‐beam and 6X megavoltage cone‐beam images. To demonstrate the advantage of MV imaging, a phantom with metallic inserts was scanned and the image quality was compared to CT and kilovoltage cone‐beam scans. With a lower energy beam and higher detector efficiency, the 2.5 MV imaging system generally yields better image quality than does the 6 MV imaging system with the conventional MV imager. In particular, with the anthropomorphic phantom studies, the contrast to noise of bone to tissue is generally improved in the 2.5 MV images compared to 6 MV. With an image quality sufficient for bony alignment, the imaging dose for 2.5 MV cone‐beam images is MU compared to 26 MU in 6 MV cone‐beam scans for the head, thorax, and pelvis regions of the phantom. Unlike kilovoltage cone‐beam, the 2.5 MV imaging system does not suffer from high‐Z image artifacts. This can be very useful for treatment planning in cases where high‐Z prostheses are present.PACS number(s): 87.57.Q‐
MRI geometric distortion: Impact on tangential whole‐breast IMRT
Authors: Walker Amy , Metcalfe Peter , Liney Gary , Batumalai Vikneswary , Dundas Kylie , Glide‐Hurst Carri , Delaney Geoff P , Boxer Miriam , Yap Mei Ling , Dowling Jason , Rivest‐Henault David , Pogson Elise , Holloway Lois 
Published: February 2017

The purpose of this study was to determine the impact of magnetic resonance imaging (MRI) geometric distortions when using MRI for target delineation and planning for whole‐breast, intensity‐modulated radiotherapy (IMRT). Residual system distortions and combined systematic and patient‐induced distortions are considered. This retrospective study investigated 18 patients who underwent whole‐breast external beam radiotherapy, where both CT and MRIs were acquired for treatment planning. Distortion phantoms were imaged on two MRI systems, dedicated to radiotherapy planning (a wide, closed‐bore 3T and an open‐bore 1T). Patient scans were acquired on the 3T system. To simulate MRI‐based planning, distortion maps representing residual system distortions were generated via deformable registration between phantom CT and MRIs. Patient CT images and structures were altered to match the residual system distortion measured by the phantoms on each scanner. The patient CTs were also registered to the corresponding patient MRI scans, to assess patient and residual system effects. Tangential IMRT plans were generated and optimized on each resulting CT dataset, then propagated to the original patient CT space. The resulting dose distributions were then evaluated with respect to the standard clinically acceptable DVH and visual assessment criteria. Maximum residual systematic distortion was measured to be 7.9 mm () and 11.9 mm () for the 3T and 1T scanners, respectively, which did not result in clinically unacceptable plans. Eight of the plans accounting for patient and systematic distortions were deemed clinically unacceptable when assessed on the original CT. For these plans, the mean difference in PTV (volume receiving 95% prescription dose) was and for right‐ and left‐sided patients, respectively. Residual system distortions alone had minimal impact on the dosimetry for the two scanners investigated. The combination of MRI systematic and patient‐related distortions can result in unacceptable dosimetry for whole‐breast IMRT, a potential issue when considering MRI‐only radiotherapy treatment planning.PACS number(s): 87.61.‐c, 87.57.cp, 87.57.nj, 87.55.D‐
RadShield: semiautomated shielding design using a floor plan driven graphical user interface
Authors: DeLorenzo Matthew C. , Wu Dee H. , Yang Kai , Rutel Isaac B. 
Published: February 2017

The purpose of this study was to introduce and describe the development of RadShield, a Java‐based graphical user interface (GUI), which provides a base design that uniquely performs thorough, spatially distributed calculations at many points and reports the maximum air‐kerma rate and barrier thickness for each barrier pursuant to NCRP Report 147 methodology. Semiautomated shielding design calculations are validated by two approaches: a geometry‐based approach and a manual approach. A series of geometry‐based equations were derived giving the maximum air‐kerma rate magnitude and location through a first derivative root finding approach. The second approach consisted of comparing RadShield results with those found by manual shielding design by an American Board of Radiology (ABR)‐certified medical physicist for two clinical room situations: two adjacent catheterization labs, and a radiographic and fluoroscopic (R&F) exam room. RadShield's efficacy in finding the maximum air‐kerma rate was compared against the geometry‐based approach and the overall shielding recommendations by RadShield were compared against the medical physicist's shielding results. Percentage errors between the geometry‐based approach and RadShield's approach in finding the magnitude and location of the maximum air‐kerma rate was within 0.00124% and 14 mm. RadShield's barrier thickness calculations were found to be within 0.156 mm lead (Pb) and 0.150 mm lead (Pb) for the adjacent catheterization labs and R&F room examples, respectively. However, within the R&F room example, differences in locating the most sensitive calculation point on the floor plan for one of the barriers was not considered in the medical physicist's calculation and was revealed by the RadShield calculations. RadShield is shown to accurately find the maximum values of air‐kerma rate and barrier thickness using NCRP Report 147 methodology. Visual inspection alone of the 2D X‐ray exam distribution by a medical physicist may not be sufficient to accurately select the point of maximum air‐kerma rate or barrier thickness.PACS number(s): 87.55.N, 87.52.‐g, 87.59.Bh, 87.57.‐s
Comparison of liver volumetry on contrast‐enhanced CT images: one semiautomatic and two automatic approaches
Authors: Cai Wei , He Baochun , Fan Yingfang , Fang Chihua , Jia Fucang 
Published: February 2017

This study was to evaluate the accuracy, consistency, and efficiency of three liver volumetry methods— one interactive method, an in‐house‐developed 3D medical Image Analysis (3DMIA) system, one automatic active shape model (ASM)‐based segmentation, and one automatic probabilistic atlas (PA)‐guided segmentation method on clinical contrast‐enhanced CT images. Forty‐two datasets, including 27 normal liver and 15 space‐occupying liver lesion patients, were retrospectively included in this study. The three methods — one semiautomatic 3DMIA, one automatic ASM‐based, and one automatic PA‐based liver volumetry — achieved an accuracy with VD (volume difference) of , and 3.06% in the normal group, respectively, and with VD of , and 4.14% in the space‐occupying lesion group, respectively. However, the three methods achieved an efficiency of 27.63 mins, 1.26 mins, 1.18 mins on average, respectively, compared with the manual volumetry, which took 43.98 mins. The high intraclass correlation coefficient between the three methods and the manual method indicated an excellent agreement on liver volumetry. Significant differences in segmentation time were observed between the three methods (3DMIA, ASM, and PA) and the manual volumetry (), as well as between the automatic volumetries (ASM and PA) and the semiautomatic volumetry (3DMIA) (). The semiautomatic interactive 3DMIA, automatic ASM‐based, and automatic PA‐based liver volumetry agreed well with manual gold standard in both the normal liver group and the space‐occupying lesion group. The ASM‐ and PA‐based automatic segmentation have better efficiency in clinical use.PACS number(s): 87.55.‐x
Diagnostic X‐ray facilities as per quality control performances in Tanzania
Authors: Sungita Yesaya Y. , Mdoe Simon S.L. , Msaki Peter 
Published: February 2017

Without appropriate quality control (QC) and preventative maintenance (PM) measures for X‐ray machines in place, the benefits of reduced dose to the patient and early diagnosis will not be realized. Quality control and PM also make it possible to unify X‐ray‐imaging practices in the country using international image quality guidelines. The impetus for the present work resulted from the concern that with the recent increase in the numbers of X‐ray machines in Tanzania, but with limited technical support to maintain and operate them, can increase radiation risk to patients and lower diagnostic accuracy. The aim of this work is to report on the current status of diagnostic X‐ray machines in Tanzania in order to produce the data needed to formulate QC and PM policies and strategies. These policies and strategies are needed to ensure that patients receive the lowest possible radiation risk and maximum health benefits from X‐ray examinations. Four QC tests were performed on a total of 196 X‐ray units. Accurate beam alignment and collimation were tested on 80 (41%) units, the timer accuracy was tested on 120 (61%) units, and a radiation leakage test was performed on 47(24%) units. Preventative maintenance tests were performed on all 196 X‐ray units. The results showed that of the units tested for QC, 59% failed the kilovoltage (kVp) test, 57% failed the timer accuracy test, 60% failed the beam alignment test, and 20% failed the radiation leakage test. Only 13% of the units passed the PM test: 53% of the units were defective, and 34% were out of order. As a result of the PM findings, the government has introduced a rehabilitation project to service X‐ray units and replace nonoperational X‐ray units. The new units have full support service contracts signed by their suppliers. As a result of the QC findings, X‐ray maintenance retraining programs have been introduced.PACS numbers: 87.52.‐g, 87.52.Tr, 87.58.SP, 87.59.Bh
MAGIC polymer gel for dosimetric verification in boron neutron capture therapy
Authors: Uusi–Simola Jouni , Heikkinen Sami , Kotiluoto Petri , Serén Tom , Seppälä Tiina , Auterinen Iiro , Savolainen Sauli 
Published: February 2017

Radiation‐sensitive polymer gels are among the most promising three‐dimensional dose verification tools developed to date. We tested the normoxic polymer gel dosimeter known by the acronym MAGIC (methacrylic and ascorbic acid in gelatin initiated by copper) to evaluate its use in boron neutron capture therapy (BNCT) dosimetry. We irradiated a large cylindrical gel phantom (diameter: 10 cm; length: 20 cm) in the epithermal neutron beam of the Finnish BNCT facility at the FiR 1 nuclear reactor. Neutron irradiation was simulated with a Monte Carlo radiation transport code MCNP. To compare dose–response, gel samples from the same production batch were also irradiated with 6 MV photons from a medical linear accelerator. Irradiated gel phantoms then underwent magnetic resonance imaging to determine their R2 relaxation rate maps. The measured and normalized dose distribution in the epithermal neutron beam was compared with the dose distribution calculated by computer simulation. The results support the feasibility of using MAGIC gel in BNCT dosimetry.PACS numbers: 87.53.Qc, 87.53.Wz, 87.66.Ff