bluuebunny/crossref_metadata_2025_split huggingface dataset:
Edge‐detection of the radiation field in double exposure portal images using a curve propagation algorithm
Authors: Lasserre Patricia , Cutt Bryce , Moffat James 
Published: December 2008

An accurate detection of the radiation field is crucial to 3D conformal radiotherapy (3D‐CRT). Automated techniques to detect the field edges on double exposure portal images have previously focused on thresholding techniques. In this paper, we present a new approach based on a curve propagation technique (the Fast Marching method) which proves to be more effective at detecting the radiation field than its thresholding counterpart. The comparison of both techniques in terms of computational speed and effectiveness of the detection is presented using complex images with non‐homogeneous intensity levels inside the radiation field, and gradual variations in intensity level at the field boundaries. Results show that our Fast Marching method is easier to automate, and converges faster to the boundaries of the segmented radiation field. The computation time of the Fast Marching technique is five times faster in typical portal images.PACS numbers: 87.53.Oq, 87.57.Nk, 87.57.‐s.
A novel algorithm for initial lesion detection in ultrasound breast images
Authors: Yap Moi Hoon , Edirisinghe Eran A. , Bez Helmut E. 
Published: December 2008

This paper proposes a novel approach to initial lesion detection in ultrasound breast images. The objective is to automate the manual process of region of interest (ROI) labeling in computer‐aided diagnosis (CAD). We propose the use of hybrid filtering, multifractal processing, and thresholding segmentation in initial lesion detection and automated ROI labeling. We used 360 ultrasound breast images to evaluate the performance of the proposed approach. Images were preprocessed using histogram equalization before hybrid filtering and multifractal analysis were conducted. Subsequently, thresholding segmentation was applied on the image. Finally, the initial lesions are detected using a rule‐based approach. The accuracy of the automated ROI labeling was measured as an overlap of 0.4 with the lesion outline as compared with lesions labeled by an expert radiologist. We compared the performance of the proposed method with that of three state‐of‐the‐art methods, namely, the radial gradient index filtering technique, the local mean technique, and the fractal dimension technique. We conclude that the proposed method is more accurate and performs more effectively than do the benchmark algorithms considered.PACS numbers: 87.57.Nk
Radiographic film dosimetry for IMRT fields in the near‐surface buildup region
Authors: Roberson Peter L. , Moran Jean M. , Kulasekere Ravi 
Published: December 2008

Radiographic film dosimetry provides fast, convenient 2‐D dose distributions, but is challenged by the dependence of film response on scatter conditions (i.e., energy dependence). Verification of delivered dose in the surface buildup region is important for intensity modulated radiation therapy (IMRT) when volumes of interest encroach on these regions (e.g., head/neck, breast). The current work demonstrates that film dosimetry can accurately predict the dose in the buildup region for IMRT, since 1) film dosimetry can be performed with sufficient accuracy for small fields and 2) IMRT is delivered by a series of “small” segments (step and shoot IMRT). This work evaluates the accuracy of X‐OMAT V (XV) and Extended Dose Range (EDR) film for measurements from 2 mm to 15 mm depths for small fields and clinical IMRT beams. Film measurements have been compared to single point measurements made with a stereotactic diode and parallel plate ionization chamber (P11) and thermoluminescent dosimeters (TLD) at various depths for square (diode, P11) and IMRT (diode, TLD) fields. Film calibration was performed using an 8‐field step exposure on a single film at 5 cm depth, which has been corrected to represent either small field or large field depth dependent film calibration techniques. Up to 10% correction for film response variation as a function of depth was required for measurements in the buildup region. A depth‐dependent calibration can sufficiently improve the accuracy for IMRT calculation verification (i.e., uncertainty). A small field film calibration technique was most appropriate for IMRT field measurements. Improved buildup region dose measurements for clinical IMRT fields promotes improved dose estimation performance for (inverse) treatment planning and allows more quantitative treatment delivery validation.PACS numbers: 87.53.‐j, 87.53.Dq
FBX aqueous chemical dosimeter for measurement of virtual wedge profiles
Authors: Semwal Manoj K. , Bansal Anil K. , Thakur Pradeep K. , Vidyasagar Pandit B. 
Published: December 2008

We investigated the ferrous sulfate–benzoic acid–xylenol orange (FBX) aqueous chemical dosimeter for measurement of virtual (dynamic) wedge profiles on a linear accelerator. The layout for irradiation of the FBX‐filled tubes mimicked a conventional linear detector array geometry. A comparison of the resulting measurements with film‐measured profiles showed that, in the main beam region, the difference between the FBX system and the film system was within and that, in the penumbra region, the difference varied from to in terms of positional equivalence, depending on the size of the dosimeter tubes. We thus believe that the energy‐independent FBX dosimetry system can measure virtual wedge profiles with reasonable accuracy at reasonable cost. However, efficiency improvement is required before this dosimetry system can be accepted into routine practice.PACS numbers: 87.53.‐j, 87.53.Dq, 87.53.Mr, 87.53.Xd, 87.66.Ff
Optimal acquisition parameter selection for CT simulators in radiation oncology
Authors: Liu Ruijie Rachel , Prado Karl L , Cody Dianna 
Published: December 2008

The purpose of this study was to identify optimal CT acquisition parameter settings for each make and model of scanners used in a large Radiation Oncology (RO) Department, considering the special requirements of CT simulation. Two CT phantoms were used to evaluate the image quality of the five different multichannel CT scanners using helical scan mode. We compared the effects of various pitch, detector configurations, and rotation time parameters on image artifacts, and on spatial and contrast resolution. We found that helical artifact was closely related to pitch and detector configuration settings. This artifact was scanner‐specific and generally more obvious when the channel width or detector collimation was equal to the image thickness. Different acquisition parameter settings produced slight differences in observed high‐ and low‐contrast resolution. Short rotation time degraded image quality for certain scanners, but only slightly, while other rotation times, such as 0.75 sec/rotation and above, had no obvious effect on resolution. An optimized combination of acquisition parameters was determined for each scanner make and model, based on phantom image quality and other considerations for clinical applications. This information may be directly useful for physicists whose CT simulation scanners match one of the five examined in this study. If not, the strategy reported here may be used as a guide to perform a similar evaluation of the scanner.PACS numbers: 87.57.Ce, 87.57.qp, 87.55.Gh, 87.57.C‐
Glandular radiation dose in tomosynthesis of the breast using tungsten targets
Authors: Sechopoulosa Ioannis , D'Orsi Carl J. 
Published: December 2008

With the advent of new detector technology, digital tomosynthesis imaging of the breast has, in the past few years, become a technique intensely investigated as a replacement for planar mammography. As with all other x‐ray–based imaging methods, radiation dose is of utmost concern in the development of this new imaging technology. For virtually all development and optimization studies, knowledge of the radiation dose involved in an imaging protocol is necessary. A previous study characterized the normalized glandular dose in tomosynthesis imaging and its variation with various breast and imaging system parameters. This characterization was performed with x‐ray spectra generated by molybdenum and rhodium targets. In the recent past, many preliminary patient studies of tomosynthesis imaging have been reported in which the x‐ray spectra were generated with x‐ray tubes with tungsten targets. The differences in x‐ray distribution among spectra from these target materials make the computation of new normalized glandular dose values for tungsten target spectra necessary. In this study we used previously obtained monochromatic normalized glandular dose results to obtain spectral results for twelve different tungsten target x‐ray spectra. For each imaging condition, two separate values were computed: the normalized glandular dose for the zero degree projection angle (), and the ratio of the glandular dose for non‐zero projection angles to the glandular dose for the zero degree projection (the relative glandular dose, RGD(α)). It was found thatis higher for tungsten target x‐ray spectra when compared withvalues for molybdenum and rhodium target spectra of both equivalent tube voltage and first half value layer. Therefore, thefor the twelve tungsten target x‐ray spectra and different breast compositions and compressed breast thicknesses simulated are reported. The RGD(α) values for the tungsten spectra vary with the parameters studied in a similar manner to that found for the molybdenum and rhodium target spectra. The surface fit equations and the fit coefficients for RGD(α) included in the previous study were also found to be appropriate for the tungsten spectra.PACS numbers: 87.57.uq
MiniMax equilibrium of networked differential games
Authors: Cao Hui , Ertin Emre , Arora Anish 
Published: December 2008

Surveillance systems based on wireless sensor network technology have been shown to successfully detect, classify and track evaders over a large area. State information collected via the sensor network also enables these systems to actuate mobile agents so as to achieve surveillance goals, such as target capture and asset protection. But satisfying these goals is complicated by the fact that the track information in a sensor network is routed to mobile agents through multihop wireless communication links and is thus subject to message delays and losses. Stabilization must also be considered in designing pursuer strategies so as to deal with state corruption as well as suboptimal evader strategies.
In this article, we formulate optimal pursuit control strategies in the presence of network effects, assuming that target track information has been established locally in the sensor network. We adapt ideas from the theory of differential games to networked games—including ones involving nonperiodic track updates, message losses and message delays—to derive optimal strategies, bounds on the information requirements, and scaling properties of these bounds. We show the inherent stabilization features of our pursuit strategies, both in terms of implementation as well as the strategies themselves.
Efficient constraint propagation engines
Authors: Schulte Christian , Stuckey Peter J. 
Published: December 2008

This article presents a model and implementation techniques for speeding up constraint propagation. Three fundamental approaches to improving constraint propagation based on propagators as implementations of constraints are explored: keeping track of which propagators are at fixpoint, choosing which propagator to apply next, and how to combine several propagators for the same constraint.
We show how idempotence reasoning and events help track fixpoints more accurately. We improve these methods by using them dynamically (taking into account current variable domains to improve accuracy). We define priority-based approaches to choosing a next propagator and show that dynamic priorities can improve propagation. We illustrate that the use of multiple propagators for the same constraint can be advantageous with priorities, and introduce staged propagators that combine the effects of multiple propagators with priorities for greater efficiency.
Thinking issues
Authors: Clear Tony 
Published: December 2008

Critiquing the negative consequences of journal impact factor measurement on software engineering researchers, Offut has noted the amount of time many of us spend measuring and observed that "measurement is very difficult" [1]. Then proceeding to critique our measurements in the teaching context he asserted, "We assign students grades in classes (a process once described as 'an inadequate report of an inaccurate judgment by a biased and variable judge of the extent to which a student has attained an undefined level of mastery of an unknown proportion of an indefinite amount of material')" [1].
This paints a rather dismal picture of the grading process? Yet as computing educators can we really refute this argument?
Colorful challenges
Authors: Ginat David 
Published: December 2008

The current issue's new challenge involves the development of two sequence processing algorithms. The naïve challenge solutions require repeated "passes" over the sequence. The problem-solver's challenge is to reduce the number of passes as much as possible, perhaps even into only one pass.
Following the presentation of the new challenge, we present the solution of the previous column's Separating Between Foes challenge. The elegant solution of this challenge embeds an approach that is useful and employed in various algorithmic tasks.
Lack of association between aspirin responsiveness and seven candidate gene haplotypes in patients with symptomatic vascular disease
Authors: Williams Shirley , Nugent Diane , Harrison Paul , Segal Helen , Syed Anila , Rothwell Peter , Kunicki Thomas 
Published: December 2008

SummaryWe studied the effect of prophylactic aspirin (ASA) ingestion on platelet function in 463 patients with stroke, transient ischemic attack (TIA) or acute coronary disease (ACD), using the Platelet Function Analyzer-100 (PFA-100). We correlated ASA responsiveness with haplotypes of seven candidate genes, selected for their documented role in platelet function, namely, the genes for integrins α2β1and αIIbβ3 (ITGA2, ITGA2B, and ITGB3), platelet glycoproteins Ibα and VI (GPIBA and GP6), the purinergic receptor P2Y1 (P2RY1), and prostaglandin H synthase 1 (PTGS1 = COX1). Non-responsiveness to ASA was defined as the failure of prior ASA ingestion to prolong the PFA-100 closure time (CT) when blood was perfused through cartridges coated with collagen plus epinephrine (CEPI-CT). ASA non-responsiveness was observed in 114 of 463 patients (24.6 %), but was not associated with haplotypes of any of the seven candidate genes. There was also no association between any haplotypes and the CT when blood was perfused through cartridges coated with collagen plus ADP (CADP-CT). The ASA non-responsive cohort had significantly increased whole blood platelet counts (p = 0.03) and plasma von Willebrand Factor antigen levels (p<0.001), which likely contributes to resistance to the inhibitory effects of ASA in the PFA-100.
High long-term absolute risk of recurrent venous thromboembolism in patients with hereditary deficiencies of protein S, protein C or antithrombin
Authors: Brouwer Jan-Leendert , Lijfering Willem , Kate Min Ki ten , Kluin-Nelemans Hanneke , Veeger Nic , van der Meer Jan 
Published: December 2008

SummaryHereditary deficiencies of protein S, protein C and antithrombin are known risk factors for first venous thromboembolism. We assessed the absolute risk of recurrence, and the contribution of concomitant thrombophilic defects in a large cohort of families with these deficiencies. Annual incidence of recurrence was estimated in 130 deficient patients, with separate estimates for those with each of protein S, protein C, and antithrombin deficiency, and in eight non-deficient patients with prior venous thromboembolism. All patients were also tested for factor V Leiden, prothrombin G20210A, high levels of factors VIII, IX and XI, and hyperhomocysteinemia. There were 81 recurrent events among 130 deficient patients. Median follow-up was 4.6 years. Annual incidences (95% confidence interval) of recurrent venous thromboembolism were 8.4% (5.8–11.7) for protein S deficiency, 6.0% (3.9–8.7) for protein C deficiency, 10.0% (6.1–15.4) for antithrombin deficiency, and overall 7.7% (6.1–9.5). Relative risk of recurrence in patients with a spontaneous versus provoked first event was 1.5 (0.95–2.3). Cumulative recurrence rates at 1, 5 and 10 years were 15%, 38% and 53%. Relative risk of recurrence with concomitant defects was 1.4 (0.7–2.6) (1 defect) and 1.4 (0.8–2.7) (≥2 defects). Annual incidence was 1.0% (0.03–5.5) in eight non-deficient patients. Annual incidence of major bleeding in deficient patients on oral anticoagulant treatment was 0.5% (0.2–1.0). We conclude that patients with a hereditary protein S, protein C or antithrombin deficiency appear to have a high absolute risk of recurrence. This risk is increased after a first spontaneous event, and by concomitance of other thrombophilic defects.
Validity and clinical utility of the simplified Wells rule for assessing clinical probability for the exclusion of pulmonary embolism
Authors: Gibson Nadine , Gerdes Victor , Büller Harry , Wells Philip , Perrier Arnaud , Gal Grégoire Le , Douma Renée 
Published: December 2008

SummaryThe recently introduced simplified Wells rule for the exclusion of pulmonary embolism (PE) assigns only one point to the seven variables of the original Wells rule. This study was performed to independently validate the simplified Wells rule for the exclusion of PE. We retrospectively calculated the prevalence of PE in the “unlikely” probability categories of the original Wells (cut-off ≤4) and the simplified Wells rule (cut-off ≤1) in 922 consecutive patients with clinically suspected PE from a multicenter cohort study. We compared the three-month incidence of venous thromboembolism (VTE) in patients with an unlikely probability and a normal D-dimer test using both scores, and the proportion of patients with this combination (clinical utility). The proportion of patients categorized as PE “unlikely” was similar using the original (78%) and the simplified (70%) Wells rule. The prevalence of PE was 13% (95% confidence interval [CI], 11–16%) and 12% (95%CI, 9.7–15%) for the original Wells and simplified Wells “unlikely” categories, respectively. None of the patients with PE “unlikely” and a normal D-dimer test experienced VTE during three-month follow-up. The proportions of patients in whom further tests could safely be withheld based on PE “unlikely” and a normal D-dimer test was 28% (95%CI, 25–31%) using the original and 26% (95%CI, 24–29%) using the simplified Wells rule. In this external retrospective validation study, the simplified Wells rule appeared to be safe and clinically useful, although prospective validation remains necessary. Simplification of the Wells rule may enhance the applicability.
The technique of measuring thrombin generation with fluorogenic substrates: 3. The effects of sample dilution
Authors: Wagenvoord Rob , Hemker Coen , Smedt Erik De 
Published: December 2008

SummaryAssessing the clotting function inevitably brings about dilution of plasma. With the existing techniques of thrombin generation (TG) measurement, dilution ranges from 2:3 to 1:8. However, the possibility that dilution alters procoagulant and anticoagulant pathways differently has not been examined. We investigated the effects of dilution on the thrombin generation process and found that the anticoagulant pathways are far more affected by dilution than the procoagulant pathways. That is, when prothrombin and antithrombin concentrations are kept constant, dilution of plasma does not significantly affect tissue factor (TF)-driven thrombin generation. We demonstrate that dilution of plasma slows down the inhibitory activity of tissue factor pathway inhibitor (TFPI) to a greater extent when compared with the down regulation by diluting procoagulant factors. Dilution of plasma has also a negative effect on the participation of the anti-haemophiliac factors VIII and IX in TG driven by contact activation or low TF concentration. We also investigated the effect of dilution on the participation of the anticoagulant system that consists of thrombomodulin, protein C and protein S (APC system). We found that plasma dilution causes a loss of sensitivity towards TM and APC. Furthermore, at high dilutions (> 1:12) a second wave of prothrombinase-activity was observed that could be attributed to the suppression of protein S-dependent inhibition. In conclusion, the mechanism of TG is profoundly disturbed by plasma dilution. As a consequence, the less a plasma sample is diluted, the better a TG experiment represents the physiological process.
Oncogenic Kras-induced leukemogeneis: hematopoietic stem cells as the initial target and lineage-specific progenitors as the potential targets for final leukemic transformation
Authors: Zhang Jing , Wang Jing , Liu Yangang , Sidik Harwin , Young Ken H. , Lodish Harvey F. , Fleming Mark D. 
Published: December 2008

Abstract
KRAS is often mutated in human hematopoietic malignancies, including juvenile myelomonocytic leukemia (JMML) and T-cell lymphoblastic leukemia/lymphoma (TLL/L). However, the exact role and function of oncogenic KRAS mutations in the initiation and progression of JMML and TLL/L remain elusive. Here, we report the use of a mouse bone marrow transplantation model to study oncogenic Kras-induced leukemogenesis. We show that as the first genetic hit, oncogenic Kras mutations initiate both JMML and TLL/L, but with different efficiencies. Limiting dilution analyses indicated that an oncogenic Kras mutation alone is insufficient to produce frank malignancy. Instead, it cooperates with additional subsequent genetic event(s). Moreover, transplantation of highly purified hematopoietic stem cells (HSCs) and myeloid progenitors identified HSCs as the primary target for the oncogenic Kras mutation. Karyotypic analysis further indicated that secondary genetic hit(s) target lineage-specific progenitors rather than HSCs for terminal tumor transformation into leukemic stem cells. Thus, we propose the cellular mechanism underlying oncogenic Kras-induced leukemogenesis, with HSCs as the primary target by the oncogenic Kras mutations and lineage-committed progenitors as the final target for cancer stem cell transformation. Our model might be also applicable to other solid tumors harboring oncogenic Kras mutations.