bluuebunny/crossref_metadata_2025_split huggingface dataset:
Craniofacial parameters of Syrian children with β‐thalassemia major
Authors: Takriti Moutaz , Dashash Mayssoon 
Published: January 2011

Abstract Aim:  To investigate cephalometric craniofacial parameters (skeletal and dental) of β‐thalassemic‐major patients and to compare findings with a group of healthy patients in the same age group.Methods:  Fifty‐one Syrian thalassemic‐major patients aged 8–12 years were recruited. Lateral cephalometric radiographs were taken. Linear and angular cephalometric measurements were recorded and compared with Syrian controls (n = 50) in the same age group.Results:  Thalassemic patients, when compared with controls, showed significant retrognathia in the mandible (reduced sella [mid‐point of sella turcica]–nasion [most anterior point on the frontonasal suture] B‐point [deepest point on the concavity of the mandibular profile between the alveolar crest and the point of the chin] angle, and decreased sella–nasion–pogonion [most anterior point on the bony chin] angle, P < 0.0001), a significant decrease in ramus height (articulare–gonian = 36.51 ± 3.87 mm, P < 0.0001). They also exhibited a significant class II skeletal pattern (P < 0.0001) and a convex facial profile as the nasion A‐point (deepest point on maxillary profile between the anterior nasal spine and the alveolar crest) pogonion angle and maxillomandibular A‐point–nasion P‐point angle increased. They also showed a highly‐significant decrease in the total posterior facial height (sella gonion [most posterior, inferior point on the angle of the mandible] = 64.24 ± 5.73 mm, P < 0.0001) and significant increase in the total anterior facial height (N–Me = 110.78 ± 6.66 mm, P = 0.009) when compared to controls.Conclusion:  Thalassemic patients exhibited a skeletal class II malocclusion, retrognathia of the mandible, a short height of the ramus, an increase in anterior facial height, and a decrease in posterior facial height.
Subscales measuring symptoms of non‐specific depression, anhedonia, and anxiety in the Edinburgh Postnatal Depression Scale
Authors: Tuohy Alan. , McVey Cynthia. 
Published: December 2010

ObjectivesThere has been considerable research and clinical interest in the comorbidity of anxiety and depression in the post‐partum period, and specifically in the possibility that the commonly used Edinburgh Postnatal Depression Scale (EPDS) incorporates an anxiety component. We hypothesized that the recommended version of factor analysis (Fabrigar, Wegener, MacCallum, & Strahan, 1999) would identify such covert dimensions more reliably than the commonly used principal components analysis with varimax rotation and eigenvalues greater than 1.DesignPrincipal axis factor extraction with parallel analysis and oblique (direct quartimin) factor rotation was applied to the 10 EPDS items.MethodThe study used a sample of recent mothers recruited and assessed via e‐mail and the Internet (N = 440). In addition to the EPDS, the Hospital Anxiety and Depression Scale (HADS) and the Positive and Negative Affect Scales (PANAS) were also administered.ResultsThree factors were found, which were identified as ‘non‐specific depressive symptoms’, ‘anhedonia’, and ‘anxietal symptoms’ subscales, respectively. These subscales were regressed on the HADS anxiety and depression and the PANAS positive and negative affectivity scales, with results substantially consistent with current structural models of the taxonomy of the emotional disorders.LimitationsThe data were obtained from a self‐selected non‐clinical sample. In addition, it is known that the use of computer‐based assessment may tend to inflate self‐report scores.ConclusionsIt was concluded that there is now sufficient evidence that clinicians should not assume the EPDS to be unidimensional, but should assess all three subscales when screening for susceptibility to post‐partum depression and/or post‐partum anxiety.
4D dose‐position verification in radiation therapy using the RADPOS system in a deformable lung phantom
Authors: Cherpak Amanda , Serban Monica , Seuntjens Jan , Cygler Joanna E. 
Published: December 2010

Purpose:A novel 4Din vivo dosimetry system (RADPOS), in conjunction with a deformable lung phantom, has been evaluated as a potential quality assurance tool for 4D radiotherapy.Methods:RADPOS detectors, which consist of a MOSFET dosimeter combined with an electromagnetic positioning probe, were placed inside the deformable lung phantom. One detector was positioned directly inside a tumor embedded in the lung phantom and another was positioned inside the lung portion of the phantom, outside the tumor. CT scans were taken with the phantom at three breathing phases, and for each phase, the detector position inside the phantom was read with the RADPOS software and compared to the position as determined from the CT data. These values were also compared to RADPOS measurements taken with the phantom on the couch of a Varian Clinac 6EX linac. The deformable phantom and the RADPOS system were also used in two radiation delivery scenarios: (1) A simulation of a free‐breathing delivery and (2) a simulation of an adaptive treatment.Results:Compared to CT imaging, the RADPOS positional accuracy was found to be better than 2.5 mm. The radial displacement measurements taken in the CT and linac rooms agreed to within an average of. Hence, the system can provide relative displacement measurements in the treatment room, consistent with measurements made in the CT room. For the free‐breathing delivery, the total dose reported by RADPOS agreed to within 4% and 5% of the treatment planning doses in the tumor and the lung portion of the phantom, respectively. The RADPOS‐measured dose values for the adaptive delivery were within 1.5% of the treatment plan values, which was well within the estimated experimental uncertainties.Conclusions:This work has shown that the deformable lung phantom‐RADPOS system can be an efficient quality assurance tool for 4D radiation therapy.
Patient‐specific radiation dose and cancer risk estimation in CT: Part I. Development and validation of a Monte Carlo program
Authors: Li Xiang , Samei Ehsan , Segars W. Paul , Sturgeon Gregory M. , Colsher James G. , Toncheva Greta , Yoshizumi Terry T. , Frush Donald P. 
Published: December 2010

Purpose:Radiation‐dose awareness and optimization in CT can greatly benefit from a dose‐reporting system that provides dose and risk estimates specific to each patient and each CT examination. As the first step toward patient‐specific dose and risk estimation, this article aimed to develop a method for accurately assessing radiation dose from CT examinations.Methods:A Monte Carlo program was developed to model a CT system (LightSpeed VCT, GE Healthcare). The geometry of the system, the energy spectra of the x‐ray source, the three‐dimensional geometry of the bowtie filters, and the trajectories of source motions during axial and helical scans were explicitly modeled. To validate the accuracy of the program, a cylindrical phantom was built to enable dose measurements at seven different radial distances from its central axis. Simulated radial dose distributions in the cylindrical phantom were validated against ion chamber measurements for single axial scans at all combinations of tube potential and bowtie filter settings. The accuracy of the program was further validated using two anthropomorphic phantoms (a pediatric one‐year‐old phantom and an adult female phantom). Computer models of the two phantoms were created based on their CT data and were voxelized for input into the Monte Carlo program. Simulated dose at various organ locations was compared against measurements made with thermoluminescent dosimetry chips for both single axial and helical scans.Results:For the cylindrical phantom, simulations differed from measurements by −4.8% to 2.2%. For the two anthropomorphic phantoms, the discrepancies between simulations and measurements ranged between (−8.1%, 8.1%) and (−17.2%, 13.0%) for the single axial scans and the helical scans, respectively.Conclusions:The authors developed an accurate Monte Carlo program for assessing radiation dose from CT examinations. When combined with computer models of actual patients, the program can provide accurate dose estimates for specific patients.
A new bias field correction method combining N3 and FCM for improved segmentation of breast density on MRI
Authors: Lin Muqing , Chan Siwa , Chen Jeon‐Hor , Chang Daniel , Nie Ke , Chen Shih‐Ting , Lin Cheng‐Ju , Shih Tzu‐Ching , Nalcioglu Orhan , Su Min‐Ying 
Published: December 2010

Purpose:Quantitative breast density is known as a strong risk factor associated with the development of breast cancer. Measurement of breast density based on three‐dimensional breast MRI may provide very useful information. One important step for quantitative analysis of breast density on MRI is the correction of field inhomogeneity to allow an accurate segmentation of the fibroglandular tissue (dense tissue). A new bias field correction method by combining the nonparametric nonuniformity normalization (N3) algorithm and fuzzy‐C‐means (FCM)‐based inhomogeneity correction algorithm is developed in this work.Methods:The analysis is performed on non‐fat‐sat T1‐weighted images acquired using a 1.5 T MRI scanner. A total of 60 breasts from 30 healthy volunteers was analyzed. N3 is known as a robust correction method, but it cannot correct a strong bias field on a large area. FCM‐based algorithm can correct the bias field on a large area, but it may change the tissue contrast and affect the segmentation quality. The proposed algorithm applies N3 first, followed by FCM, and then the generated bias field is smoothed using Gaussian kernal and B‐spline surface fitting to minimize the problem of mistakenly changed tissue contrast. The segmentation results based on the corrected images were compared to the N3 and FCM alone corrected images and another method, coherent local intensity clustering (CLIC), corrected images. The segmentation quality based on different correction methods were evaluated by a radiologist and ranked.Results:The authors demonstrated that the iterative correction method brightens the signal intensity of fatty tissues and that separates the histogram peaks between the fibroglandular and fatty tissues to allow an accurate segmentation between them. In the first reading session, the radiologist found ranking in 17 breasts, ranking in 7 breasts, in 32 breasts, in 2 breasts, and in 2 breasts. The results of the second reading session were similar. The performance in each pairwise Wilcoxon signed‐rank test is significant, showing superior to both N3 and FCM, and N3 superior to FCM. The performance of the new algorithm was comparable to that of CLIC, showing equivalent quality in 57/60 breasts.Conclusions:Choosing an appropriate bias field correction method is a very important preprocessing step to allow an accurate segmentation of fibroglandular tissues based on breast MRI for quantitative measurement of breast density. The proposed algorithm combining and CLIC both yield satisfactory results.
Comparison of scatter rejection and low‐contrast performance of scan equalization digital radiography (SEDR), slot‐scan digital radiography, and full‐field digital radiography systems for chest phantom imaging
Authors: Liu Xinming , Shaw Chris C. , Lai Chao‐Jen , Wang Tianpeng 
Published: December 2010

Purpose:To investigate and compare the scatter rejection properties and low‐contrast performance of the scan equalization digital radiography (SEDR) technique to the slot‐scan and conventional full‐field digital radiography techniques for chest imaging.Methods:A prototype SEDR system was designed and constructed with an a‐Se flat‐panel (FP) detector to improve image quality in heavily attenuating regions of an anthropomorphic chest phantom. Slot‐scanning geometry was used to reject scattered radiation without attenuating primary x rays. The readout scheme of the FP was modified to erase accumulated scatter signals prior to image readout. A 24‐segment beam width modulator was developed to regulate x‐ray exposures regionally and compensate for the low x‐ray flux in heavily attenuating regions. To measure the scatter‐to‐primary ratios (SPRs), a 2 mm thick lead plate with a 2‐D array of aperture holes was used to measure the primary signals, which were then subtracted from those obtained without the lead plate to determine scatter components. A 2‐D array of aluminum beads (3 mm in diameter) was used as the low‐contrast objects to measure the contrast ratios (CRs) and contrast‐to‐noise ratios (CNRs) for evaluating the low‐contrast performance in chest phantom images. A set of two images acquired with the same techniques were subtracted from each other to measure the noise levels. SPRs, CRs, and CNRs of the SEDR images were measured in four anatomical regions of chest phantom images and compared to those of slot‐scan images and full‐field images acquired with and without antiscatter grid.Results:The percentage reduction of SPR (percentage of SPRs reduced with scatter removal/rejection methods relative to that for nongrid full‐field imaging) averaged over four anatomical regions was measured to be 80%, 83%, and 71% for SEDR, slot‐scan, and full‐field with grid, respectively. The average CR over four regions was found to improve over that for nongrid full‐field imaging by 259%, 279%, and 145% for SEDR, slot‐scan, and full‐field with grid, respectively. The average CNR over four regions was found to improve over that for nongrid full‐field imaging by 201% for SEDR as compared to 133% for the slot‐scan technique and 14% for the antiscatter grid method.Conclusions:Both SEDR and slot‐scan techniques outperformed the antiscatter grid method used in standard full‐field radiography. For imaging with the same effective exposure, the SEDR technique offers no advantage over the slot‐scan method in terms of SPRs and CRs. However, it improves CNRs significantly, especially in heavily attenuating regions. The improvement of low‐contrast performance may help improve the detection of the lung nodules or other abnormalities and may offer SEDR the potential for dose reduction in chest radiography.
Neutron‐induced electronic failures around a high‐energy linear accelerator
Authors: Kry Stephen F. , Johnson Jennifer L. , White R. Allen , Howell Rebecca M. , Kudchadker Rajat J. , Gillin Michael T. 
Published: December 2010

Purpose:After a new in‐vault CT‐on‐rails system repeatedly malfunctioned following use of a high‐energy radiotherapy beam, we investigated the presence and impact of neutron radiation on this electronic system, as well as neutron shielding options.Methods:We first determined the CT scanner's failure rate as a function of the number of 18 MV monitor units (MUs) delivered. We then re‐examined the failure rate with both 2.7‐cm‐thick and 7.6‐cm‐thick borated polyethylene (BPE) covering the linac head for neutron shielding. To further examine shielding options, as well as to explore which neutrons were relevant to the scanner failure, Monte Carlo simulations were used to calculate the neutron fluence and spectrum in the bore of the CT scanner. Simulations included BPE covering the CT scanner itself as well as covering the linac head.Results:We found that the CT scanner had a 57% chance of failure after the delivery of 200 MUs. While the addition of neutron shielding to the accelerator head reduced this risk of failure, the benefit was minimal and even 7.6 cm of BPE was still associated with a 29% chance of failure after the delivery of 200 MU. This shielding benefit was achieved regardless of whether the linac head or CT scanner was shielded. Additionally, it was determined that fast neutrons were primarily responsible for the electronic failures.Conclusions:As illustrated by the CT‐on‐rails system in the current study, physicists should be aware that electronic systems may be highly sensitive to neutron radiation. Medical physicists should therefore monitor electronic systems that have not been evaluated for potential neutron sensitivity. This is particularly relevant as electronics are increasingly common in the therapy vault and newer electronic systems may exhibit increased sensitivity.
Beam commissioning and measurements validating the beam model in a new TPS that converts helical tomotherapy plans to step‐and‐shoot IMRT plans
Authors: Petersson Kristoffer , Ceberg Crister , Engström Per , Knöös Tommy 
Published: December 2010

Purpose:A new type of treatment planning system calledSHAREPLAN has been studied, which enables the transfer of treatment plans generated for helical tomotherapy delivery to plans that can be delivered on C‐arm linacs. The purpose is to ensure continuous patient treatment during periods of unscheduled downtime for the TomoTherapy unit, particularly in clinics without a backup unit. The purpose of this work was to verify that the plans generated in this novel planning system are deliverable and accurate. The work consists primarily of beam commissioning, verification of the beam model, and measurements verifying that generated plans are deliverable with sufficient accuracy.Methods:The beam commissioning process involves input of general geometric properties of the modeled linac, profiles and depth dose curves for a specific photon nominal energy (6 MV), and the automated modeling of other beam properties. Some manual tuning of the beam model is required. To evaluate its accuracy, the confidence limit concept [J. Venselaar et al., “Tolerances for the accuracy of photon beam dose calculations of treatment planning systems,” Radiother. Oncol. 60, 191–201 (2001)] was used, which is a method supported by ESTRO. Measurements were conducted with a 2D diode array at the commissioned linac as a final check of the beam model and to evaluate whether the generated plans were deliverable and accurate.Results:The comparison and evaluation of calculated data points and measured data according to the method applied confirmed the accuracy of the beam model. The profiles had a confidence limit of 1.1% and the depth dose curves had a confidence limit of 1.7%, both of which were well below the tolerance limit of 2%. Plan specific QC measurements and evaluation verified that different plans generated in the TPS were deliverable with sufficient accuracy at the commissioned linac, as none of the 160 beams for the 20 different plans evaluated had a fraction of approved data points below 90%, the local clinical approval criterion for delivery QA measurements.Conclusions:This study is a validation of the new TPS as it verifies that the generated plans are deliverable at a commissioned linac with adequate accuracy. A thorough investigation of the treatment plan quality will require a separate study. The TPS is proving to be a useful and time‐saving complement, especially for clinics having a single unit for helical delivery among its conventional linacs.
Technical Note: DIRART – A software suite for deformable image registration and adaptive radiotherapy research
Authors: Yang Deshan , Brame Scott , El Naqa Issam , Aditya Apte , Wu Yu , Murty Goddu S. , Mutic Sasa , Deasy Joseph O. , Low Daniel A. 
Published: December 2010

Purpose:Recent years have witnessed tremendous progress in image guide radiotherapy technology and a growing interest in the possibilities for adapting treatment planning and delivery over the course of treatment. One obstacle faced by the research community has been the lack of a comprehensive open‐source software toolkit dedicated for adaptive radiotherapy (ART). To address this need, the authors have developed a software suite called the Deformable Image Registration and Adaptive Radiotherapy Toolkit (DIRART).Methods:DIRART is an open‐source toolkit developed in MATLAB. It is designed in an object‐oriented style with focus on user‐friendliness, features, and flexibility. It contains four classes of DIR algorithms, including the newer inverse consistency algorithms to provide consistent displacement vector field in both directions. It also contains common ART functions, an integrated graphical user interface, a variety of visualization and image‐processing features, dose metric analysis functions, and interface routines. These interface routines make DIRART a powerful complement to the Computational Environment for Radiotherapy Research (CERR) and popular image‐processing toolkits such as ITK.Results:DIRART provides a set of image processing/registration algorithms and postprocessing functions to facilitate the development and testing of DIR algorithms. It also offers a good amount of options for DIR results visualization, evaluation, and validation.Conclusions: By exchanging data with treatment planning systems via DICOM‐RT files andCERR, and by bringing image registration algorithms closer to radiotherapy applications, DIRART is potentially a convenient and flexible platform that may facilitate ART and DIR research.
Prostate cancer characterization on MR images using fractal features
Authors: Lopes R. , Ayache A. , Makni N. , Puech P. , Villers A. , Mordon S. , Betrouni N. 
Published: December 2010

Purpose:Computerized detection of prostate cancer on T2‐weighted MR images.Methods:The authors combined fractal and multifractal features to perform textural analysis of the images. The fractal dimension was computed using the Variance method; the multifractal spectrum was estimated by an adaptation of a multifractional Brownian motion model. Voxels were labeled as tumor/nontumor via nonlinear supervised classification. Two classification algorithms were tested: Support vector machine (SVM) and AdaBoost.Results:Experiments were performed on images from 17 patients. Ground truth was available from histological images. Detection and classification results (sensitivity, specificity) were (83%, 91%) and (85%, 93%) for SVM and AdaBoost, respectively.Conclusions: Classification using the authors' model combining fractal and multifractal features was more accurate than classification using classical texture features (such as Haralick, wavelet, and Gabor filters). Moreover, the method was more robust against signal intensity variations. Although the method was only applied to T2 images, it could be extended to multispectral MR.