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Sample records for exam mlc reserved

  1. Pelvic Exam

    MedlinePlus

    ... hyphen, e.g. -historical Searches are case-insensitive Exam, Pelvic Add to My Pictures View /Download : Small: ... 1500x1230 View Download Large: 3000x2460 View Download Title: Exam, Pelvic Description: Pelvic exam; drawing shows a side ...

  2. Megalencephalic Leukoencephalopathy with Subcortical Cysts (MLC)

    MedlinePlus

    ... new treatments for the disease. Are there other names for Megalencephalic Leukoencephalopathy with subcortical Cysts (MLC)? Other names for Megalencephalic Leukoencephalopathy with subcortical Cysts (MLC) include: ...

  3. Testicular Exams

    MedlinePlus

    ... the exam make sense to most guys: The scale is used to weigh you, the stethoscope is used to listen to your heartbeat. But why does the doctor need to touch and feel your testicles ? Isn't there a better, less embarrassing way to check things out? When you are healthy and going for ...

  4. Testicular self-exam

    MedlinePlus

    Screening - testicular cancer - self-exam; Testicular cancer - screening - self-exam ... A testicular self-exam is done to check for testicular cancer . Testicles have blood vessels and other structures that can make the exam ...

  5. Skin self-exam

    MedlinePlus

    Skin cancer - self-exam; Melanoma - self-exam; Basal cell cancer - self-exam; Squamous cell - self-exam; Skin mole - self-exam ... do not agree on whether or not skin self-exams should be performed. So there is no ...

  6. Skin self-exam

    MedlinePlus

    Skin cancer - self-exam; Melanoma - self-exam; Basal cell cancer - self-exam; Squamous cell - self-exam; Skin mole - self-exam ... Experts do not agree on whether or not skin self-exams should be performed. So there is ...

  7. The impact of MLC transmitted radiation on EPID dosimetry for dynamic MLC beams

    SciTech Connect

    Vial, Philip; Greer, Peter B.; Hunt, Peter; Oliver, Lyn; Baldock, Clive

    2008-04-15

    The purpose of this study was to experimentally quantify the change in response of an amorphous silicon (a-Si) electronic portal imaging device (EPID) to dynamic multileaf collimator (dMLC) beams with varying MLC-transmitted dose components and incorporate the response into a commercial treatment planning system (TPS) EPID prediction model. A combination of uniform intensity dMLC beams and static beams were designed to quantify the effect of MLC transmission on EPID response at the central axis of 10x10 cm{sup 2} beams, at off-axis positions using wide dMLC beam profiles, and at different field sizes. The EPID response to MLC transmitted radiation was 0.79{+-}0.02 of the response to open beam radiation at the central axis of a 10x10 cm{sup 2} field. The EPID response to MLC transmitted radiation was further reduced relative to the open beam response with off-axis distance. The EPID response was more sensitive to field size changes for MLC transmitted radiation compared to open beam radiation by a factor of up to 1.17 at large field sizes. The results were used to create EPID response correction factors as a function of the fraction of MLC transmitted radiation, off-axis distance, and field size. Software was developed to apply the correction factors to each pixel in the TPS predicted EPID image. The corrected images agreed more closely with the measured EPID images in areas of intensity modulated fields with a large fraction of MLC transmission and, as a result the accuracy of portal dosimetry with a-Si EPIDs can be improved. Further investigation into the detector response function and the radiation source model are required to achieve improvements in accuracy for the general case.

  8. Slit-lamp exam

    MedlinePlus

    ... to light for a few hours after the exam if dilating drops are used. ... The slit lamp exam may detect many diseases of the eye, including: Clouding of the lens of the eye ( cataract ) Injury to the ...

  9. Testicular self-exam

    MedlinePlus

    Screening - testicular cancer - self-exam; Testicular cancer - screening - self-exam ... 2014:chap 86. National Cancer Institute: Testicular Cancer Screening (PDQ). Bethesda, MD. Date last modified: July 19, ...

  10. Diabetes eye exams

    MedlinePlus

    ... catch problems early if you get regular eye exams. ... diabetes checks your eyes, you need an eye exam every 1 to 2 years by an eye ... problems with your vision. Many can do screening exams for damage from diabetes. Once you have eye ...

  11. Exams: The Secret Ingredients

    ERIC Educational Resources Information Center

    DiJulio, Betsy

    2012-01-01

    This year, many high-school teachers in the district where the author teaches experienced exam anxiety because midterms--as they had come to know and love them--were no more. For a variety of reasons, the semester exam schedule looked very different. More to the point is the new philosophy about exam content and format that underpinned the…

  12. Challenges When Introducing Electronic Exam

    ERIC Educational Resources Information Center

    Kuikka, Matti; Kitola, Markus; Laakso, Mikko-Jussi

    2014-01-01

    Time pressures often necessitate the use of more efficient exam tools, such as electronic exams (e-exams), instead of traditional paper exams. However, teachers may face challenges when introducing e-exams in a higher education context. This paper describes what kinds of challenges teachers may face when introducing e-exams, based on experiences…

  13. Exam preparation learning

    NASA Astrophysics Data System (ADS)

    Fakcharoenphol, Witat

    This thesis investigates student learning through practice exams. A series of experiments were conducted using a web-based platform that provided students with an organized structure to study past exam problems. We establish the learning obtained from doing these practice exams (Chapter 1) and then manipulate the feedback mechanisms (Chapter 2 and 4) and duration of the treatment (Chapter 3). The results show that all students benefit from practice exams and worked out solution feedback. However, investing more resources in this learning tool might not result in better learning gains. A comparison between experiments suggests that, beyond the quality of the practice exams and solution feedback, motivation and learning goals may be crucial to enhancing student learning during exam preparation.

  14. Examining Exam Reviews: A Comparison of Exam Scores and Attitudes

    ERIC Educational Resources Information Center

    Hackathorn, Jana; Cornell, Kathryn; Garczynski, Amy M.; Solomon, Erin D.; Blankmeyer, Katheryn E.; Tennial, Rachel E.

    2012-01-01

    Instructors commonly use exam reviews to help students prepare for exams and to increase student success. The current study compared the effects of traditional, trivia, and practice test-based exam reviews on actual exam scores, as well as students' attitudes toward each review. Findings suggested that students' exam scores were significantly…

  15. Identification of novel MLC1 mutations in Chinese patients with megalencephalic leukoencephalopathy with subcortical cysts (MLC).

    PubMed

    Wang, Jingmin; Shang, Jing; Wu, Ye; Gu, Qiang; Xiong, Hui; Ding, Changhong; Wang, Liwen; Gao, Zhijie; Wu, Xiru; Jiang, Yuwu

    2011-02-01

    Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is an autosomal, recessively inherited disease caused by mutations in the MLC1 gene. Most of the previously published studies have been carried out in ethnic populations other than the Chinese. In this study, the analysis of clinical features and MLC1 mutation screening were performed in 13 Chinese patients for the first time. A total of 10 MLC1 mutations were identified in these patients, including five novel missense mutations (c.65G>A, p.R22Q; c.95C>T, p.A32V; c.218G>A, p.G73E; c.823G>A, p.A275T; c.832T>C, p.Y278H), one novel splicing mutation (c.772-1G>C in IVS9-1), one novel small deletion (c.907_930del, p.V303_L310del), one known nonsense mutation (c.593delCTCA, p.Y198X) and two known missense mutations (c.206C>T, p.S69L; c.353C>T, p.T118M). Mutation c.772-1G>C in IVS9-1, accounting for 27.3% (3/11) of the total number of genetically confirmed patients found in this study, is thus a putative hot-spot mutation in the present study group. The existence of a unique MLC1 mutation spectrum in Chinese MLC patients was shown. A systemic study to assess the mutation spectra in different populations should be undertaken. PMID:21160490

  16. My Favorite Exam Question

    ERIC Educational Resources Information Center

    Styer, Dan

    2015-01-01

    My favorite exam question comes from the final exam in an introductory mechanics course: "A rolling 31 ton railroad boxcar collides with a stationary flatcar. The coupling mechanism activates so the cars latch together and roll down the track attached. Of the initial kinetic energy, 38% dissipates as heat, sound, vibrations, mechanical…

  17. My Favorite Exam Question

    NASA Astrophysics Data System (ADS)

    Styer, Dan

    2015-12-01

    My favorite exam question comes from the final exam in an introductory mechanics course: A rolling 31 ton railroad boxcar collides with a stationary flatcar. The coupling mechanism activates so the cars latch together and roll down the track attached. Of the initial kinetic energy, 38% dissipates as heat, sound, vibrations, mechanical deformation, and so forth. How much does the flatcar weigh?

  18. Breast self-exam

    MedlinePlus

    Self-examination of the breast; BSE; Breast cancer - BSE; Breast cancer screening - self exam ... American Cancer Society recommendations for early breast cancer detection in women without breast symptoms. ... . Revised October 20, ...

  19. Physical exam frequency

    MedlinePlus

    How often you need a physical exam; Health maintenance visit; Health screening; Checkup ... All adults should visit their health care provider from time to time, even if they are healthy. The purpose of these visits is to: Screen for diseases ...

  20. Exam Question Exchange.

    ERIC Educational Resources Information Center

    Alexander, John J.

    1979-01-01

    Describes an exam question which challenges college freshmen, enrolled in chemistry, to derive temperature dependence of an equilibrium constant. The question requires cognitive response at the level of synthesis. (Author/SA)

  1. Oral Cancer Exam

    MedlinePlus Videos and Cool Tools

    ... Dental Research See All Continuing Education Practical Oral Care for People With Developmental Disabilities – This booklet presents ... developmental disabilities and offers strategies for providing oral care. NIDCR > OralHealth > Topics > Oral Cancer > Oral Cancer Exam ...

  2. Neuroprotective and neuroproliferative activities of NeuroAid (MLC601, MLC901), a Chinese medicine, in vitro and in vivo.

    PubMed

    Heurteaux, C; Gandin, C; Borsotto, M; Widmann, C; Brau, F; Lhuillier, M; Onteniente, B; Lazdunski, M

    2010-06-01

    Although stroke remains a leading cause of death and adult disability, numerous recent failures in clinical stroke trials have led to some pessimism in the field. Interestingly, NeuroAid (MLC601), a traditional medicine, particularly used in China, South East Asia and Middle East has been reported to have beneficial effects in patients, particularly in post-stroke complications. Here, we demonstrate in a rodent model of focal ischemia that NeuroAid II (MLC901) pre- and post-treatments up to 3 h after stroke improve survival, protect the brain from the ischemic injury and drastically decrease functional deficits. MLC601 and MLC901 also prevent neuronal death in an in vitro model of excitotoxicity using primary cultures of cortical neurons exposed to glutamate. In addition, MLC601/MLC901 treatments were shown to induce neurogenesis in rodent and human cells, promote cell proliferation as well as neurite outgrowth and stimulate the development of a dense axonal and dendritic network. MLC601 and MLC901 clearly represent a very interesting strategy for stroke treatment at different stages of the disease. PMID:20064536

  3. Exam Question Exchange.

    ERIC Educational Resources Information Center

    Ramette, R. W.

    1988-01-01

    Describes a take-home exam story problem based on stoichiometry. Requires the student to determine the percentage of phosphoric acid in a large container of nitric acid if a man fell into it. Provides assumptions, clues, and an acceptable solution. (MVL)

  4. Breast self-exam

    MedlinePlus

    Self-examination of the breast; BSE; Breast cancer - BSE ... The best time to do a monthly self-breast exam is about 3 to 5 days after ... it at the same time every month. Your breasts are not as tender or lumpy at this ...

  5. Exam Question Exchange.

    ERIC Educational Resources Information Center

    Alexander, John J., Ed.

    1978-01-01

    Two exam questions are presented. One suitable for advanced undergraduate or beginning graduate courses in organic chemistry, is on equivalent expressions for the description of several pericyclic reactions. The second, for general chemistry students, asks for an estimation of the rate of decay of a million-year-old Uranium-238 sample. (BB)

  6. Exam 2 Strategy

    ERIC Educational Resources Information Center

    Cummings, Richard G.; Gruber, Robert A.

    2006-01-01

    After students take their first exam in an accounting course, tax accounting and intermediate accounting in this case, their reactions to their test scores may be varied. This is their first major assessment of how they have performed in the class. The students in the class near the high end of the grading scale are going to be satisfied with…

  7. Performing Automatic Exams.

    ERIC Educational Resources Information Center

    Frosini, G.; Lazzerini, B.; Marcelloni, F.

    1998-01-01

    Describes a tool for building software systems which replace the role of the examiner during a typical Italian academic exam in technical/scientific subjects. Such systems are designed to exploit the advantages of self-adapted testing for reducing effects of anxiety, and of computerized adaptive testing for increasing assessment efficiency.…

  8. Exam experience and some reactions to exam stress.

    PubMed

    Simić, N; Manenica, I

    2012-01-01

    The aim of this study was to assess the effects of previous exam experience on some psychophysiological reactions before, during and after repeated exams. A sample of 15 first year psychology students took part in the study. While the subjects were expecting a oral exam for the first time, their levels of exam apprehension, high activation and state anxiety were measured a day before, an hour before the exam and the following day. Furthermore, subjects' cardiac R-R intervals were continuously recorded from five minutes before the exam to five minutes after the exam. Four, out of 15 subjects, passed the exams at first sitting, while the rest of them failed and had to repeat it. These 11 students underwent the same procedure for the second time. The levels of exam apprehension, high activation and anxiety did not show any differences between the first and the second exam sittings. R-R interval parameters indicated a higher stress before and after the second exam sitting, while the stress level was more or less the same during both exams. PMID:22567840

  9. Modeling the Agility MLC in the Monaco treatment planning system.

    PubMed

    Snyder, Michael; Halford, Robert; Knill, Cory; Adams, Jeffrey N; Bossenberger, Todd; Nalichowski, Adrian; Hammoud, Ahmad; Burmeister, Jay

    2016-01-01

    We investigate the relationship between the various parameters in the Monaco MLC model and dose calculation accuracy for an Elekta Agility MLC. The vendor-provided MLC modeling procedure - completed first with external vendor participation and then exclusively in-house - was used in combination with our own procedures to investigate several sets of MLC modeling parameters to determine their effect on dose distributions and point-dose measurements. Simple plans provided in the vendor procedure were used to elucidate specific mechanical characteristics of the MLC, while ten complex treatment plans - five IMRT and five VMAT - created using TG-119-based structure sets were used to test clinical dosimetric effects of particular parameter choices. EDR2 film was used for the vendor fields to give high spatial resolution, while a combination of MapCHECK and ion chambers were used for the in-house TG-119-based proced-ures. The vendor-determined parameter set provided a reasonable starting point for the MLC model and largely delivered acceptable gamma pass rates for clinical plans - including a passing external evaluation using the IROC H&N phantom. However, the vendor model did not provide point-dose accuracy consistent with that seen in other treatment systems at our center. Through further internal testing it was found that there existed many sets of MLC parameters, often at opposite ends of their allowable ranges, that provided similar dosimetric characteristics and good agreement with planar and point-dose measurements. In particular, the leaf offset and tip leakage parameters compensated for one another if adjusted in opposite directions, which provided a level curve of acceptable parameter sets across all plans. Interestingly, gamma pass rates of the plans were less dependent upon parameter choices than point-dose measurements, suggesting that MLC modeling using only gamma evaluation may be generally an insufficient approach. It was also found that exploring all

  10. Preparing Students for the AP Psychology Exam

    ERIC Educational Resources Information Center

    Whitlock, Kristin

    2013-01-01

    The Advanced Placement Psychology exam is one of the fastest growing exams offered by the College Board. The average percent of change in the number of students taking this exam over the past five years is 12.4%. With 238,962 students taking the exam in 2013, the AP Psychology exam is the sixth largest exam, surpassing AP Biology and AP World…

  11. SU-E-T-545: MLC Distance Travelled as a Predictor for Motor Failure

    SciTech Connect

    Stathakis, S; Defoor, D; Linden, P; Kirby, N; Papanikolaou, N; Mavroidis, P

    2015-06-15

    Purpose: To study the frequency of Multi-Leaf Collimator (MLC) leaf failures, investigate methods to predict them and reduce linac downtime. Methods: A Varian HD120 MLC was used in our study. The hyperterminal MLC errors logged from 06/2012 to 12/2014 were collected. Along with the hyperterminal errors, the MLC motor changes and all other MLC interventions by the linear accelerator engineer were recorded. The MLC dynalog files were also recorded on a daily basis for each treatment and during linac QA. The dynalog files were analyzed to calculate root mean square errors (RMS) and cumulative MLC travel distance per motor. An in-house MatLab code was used to analyze all dynalog files, record RMS errors and calculate the distance each MLC traveled per day. Results: A total of 269 interventions were recorded over a period of 18 months. Of these, 146 included MLC motor leaf change, 39 T-nut replacements, and 84 MLC cleaning sessions. Leaves close to the middle of each side required the most maintenance. In the A bank, leaves A27 to A40 recorded 73% of all interventions, while the same leaves in the B bank counted for 52% of the interventions. On average, leaves in the middle of the bank had their motors changed approximately every 1500m of travel. Finally, it was found that the number of RMS errors increased prior to an MLC motor change. Conclusion: An MLC dynalog file analysis software was developed that can be used to log daily MLC usage. Our eighteen-month data analysis showed that there is a correlation between the distance an MLC travels, the RMS and the life of the MLC motor. We plan to use this tool to predict MLC motor failures and with proper and timely intervention, reduce the downtime of the linac during clinical hours.

  12. The Use of NeuroAiD (MLC601) in Postischemic Stroke Patients.

    PubMed

    Navarro, Jose C; Molina, Mark C; Baroque Ii, Alejandro C; Lokin, Johnny K

    2012-01-01

    Aim. We aimed to assess the efficacy of MLC601 on functional recovery in patients given MLC601 after an ischemic stroke. Methods. This is a retrospective cohort study comparing poststroke patients given open-label MLC601 (n = 30; 9 female) for three months and matching patients who did not receive MLC601 from our Stroke Data Bank. Outcome assessed was modified Rankin Scale (mRS) at three months and analyzed according to: (1) achieving a score of 0-2, (2) achieving a score of 0-1, and (3) mean change in scores from baseline. Results. At three months, 21 patients on MLC601 became independent as compared to 17 patients not on MLC601 (OR 1.79; 95% CI 0.62-5.2; P = 0.29). There were twice as many patients (n = 16) on MLC601 who attained mRS scores similar to their prestroke state than in the non-MLC601 group (n = 8) (OR 3.14; 95% CI 1.1-9.27; P = 0.038). Mean improvement in mRS from baseline was better in the MLC601 group than in the non-MLC601 group (-1.7 versus -0.9; mean difference -0.73; 95% CI -1.09 to -0.38; P < 0.001). Conclusion. MLC601 improves functional recovery at 3 months postischemic stroke. An ongoing large randomized control trial of MLC601 will help validate these results. PMID:23304514

  13. MLC1 is associated with the Dystrophin-Glycoprotein Complex at astrocytic endfeet

    PubMed Central

    Boor, Ilja; Nagtegaal, Machiel; Kamphorst, Wouter; van der Valk, Paul; Pronk, Jan C.; van Horssen, Jack; Dinopoulos, Argirios; Bove, Kevin E.; Pascual-Castroviejo, Ignacio; Muntoni, Francesco; Estévez, Raúl; Scheper, Gert C.

    2007-01-01

    Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a progressive cerebral white matter disease with onset in childhood, caused by mutations in the MLC1 gene. MLC1 is a protein with unknown function that is mainly expressed in the brain in astrocytic endfeet at the blood–brain and cerebrospinal fluid–brain barriers. It shares its localization at astrocytic endfeet with the dystrophin-associated glycoprotein complex (DGC). The objective of the present study was to investigate the possible association of MLC1 with the DGC. To test this hypothesis, (co)-localization of DGC-proteins and MLC1 was analyzed by immunohistochemical stainings in gliotic brain tissue from a patient with multiple sclerosis, in glioblastoma tissue and in brain tissue from an MLC patient. In control tissue, a direct protein interaction was tested by immunoprecipitation. Results revealed that MLC1 is co-localized with DGC-proteins in gliotic brain tissue. We demonstrated that both MLC1 and aquaporin-4, a member of the DGC, were redistributed in glioblastoma cells. In MLC brain tissue, we showed absence of MLC1 and altered expression of several DGC-proteins. We demonstrated a direct protein interaction between MLC1 and Kir4.1. From these results we conclude that MLC1 is associated with the DGC at astrocytic endfeet. PMID:17628813

  14. Fast regional readout CMOS Image Sensor for dynamic MLC tracking

    NASA Astrophysics Data System (ADS)

    Zin, H.; Harris, E.; Osmond, J.; Evans, P.

    2014-03-01

    Advanced radiotherapy techniques such as volumetric modulated arc therapy (VMAT) require verification of the complex beam delivery including tracking of multileaf collimators (MLC) and monitoring the dose rate. This work explores the feasibility of a prototype Complementary metal-oxide semiconductor Image Sensor (CIS) for tracking these complex treatments by utilising fast, region of interest (ROI) read out functionality. An automatic edge tracking algorithm was used to locate the MLC leaves edges moving at various speeds (from a moving triangle field shape) and imaged with various sensor frame rates. The CIS demonstrates successful edge detection of the dynamic MLC motion within accuracy of 1.0 mm. This demonstrates the feasibility of the sensor to verify treatment delivery involving dynamic MLC up to ~400 frames per second (equivalent to the linac pulse rate), which is superior to any current techniques such as using electronic portal imaging devices (EPID). CIS provides the basis to an essential real-time verification tool, useful in accessing accurate delivery of complex high energy radiation to the tumour and ultimately to achieve better cure rates for cancer patients.

  15. Monte Carlo study of MLC fields for cobalt therapy machine

    PubMed Central

    Ayyangar, Komanduri M.; Rani, Roopa A.; Kumar, Anil; Reddy, A. R.

    2014-01-01

    An automated Multi-Leaf Collimator (MLC) system has been developed as add-on for the cobalt-60 teletherapy machines available in India. The goal of the present computational study is to validate the MLC design using Monte Carlo (MC) modeling. The study was based on the Kirloskar-supplied Phoenix model machines that closely match the Atomic Energy of Canada Limited (AECL) theratron-80 machine. The MLC is a retrofit attachment to the collimator assembly, with 14 non-divergent leaf pairs of 40 mm thick, 7 mm wide, and 150 mm long tungsten alloy plates with rounded edges and 20 mm tongue and 2 mm groove in each leaf. In the present work, the source and collimator geometry has been investigated in detail to arrive at a model that best represents the measured dosimetric data. The authors have studied in detail the proto-I MLC built for cobalt-60. The MLC field sizes were MC simulated for 2 × 2 cm2 to 14 × 14 cm2 square fields as well as irregular fields, and the percent depth dose (PDD) and profile data were compared with ROPS† treatment planning system (TPS). In addition, measured profiles using the IMATRIXX system‡ were also compared with the MC simulations. The proto-I MLC can define radiation fields up to 14 × 14 cm2 within 3 mm accuracy. The maximum measured leakage through the leaf ends in closed condition was 3.4% and interleaf leakage observed was 7.3%. Good agreement between MC results, ROPS and IMATRIXX results has been observed. The investigation also supports the hypothesis that optical and radiation field coincidence exists for the square fields studied with the MLC. Plots of the percent depth dose (PDD) data and profile data for clinically significant irregular fields have also been presented. The MC model was also investigated to speed up the calculations to allow calculations of clinically relevant conformal beams. †Radiation Oncology Planning System (ROPS) is supplied by Tirumala Jyothi Computer Systems described at https

  16. An MLC calibration method using a detector array

    SciTech Connect

    Simon, Thomas A.; Kahler, Darren; Simon, William E.; Fox, Christopher; Li, Jonathan; Palta, Jatinder; Liu, Chihray

    2009-10-15

    Purpose: The authors have developed a quantitative calibration method for a multileaf collimator (MLC) which measures individual leaf positions relative to the MLC backup jaw on an Elekta Synergy linear accelerator. Methods: The method utilizes a commercially available two-axis detector array (Profiler 2; Sun Nuclear Corporation, Melbourne, FL). To calibrate the MLC bank, its backup jaw is positioned at the central axis and the opposing jaw is retracted to create a half-beam configuration. The position of the backup jaws field edge is then measured with the array to obtain what is termed the radiation defined reference line. The positions of the individual leaf ends relative to this reference line are then inferred by the detector response in the leaf end penumbra. Iteratively adjusting and remeasuring the leaf end positions to within specifications completes the calibration. Using the backup jaw as a reference for the leaf end positions is based on three assumptions: (1) The leading edge of an MLC leaf bank is parallel to its backup jaw's leading edge, (2) the backup jaw position is reproducible, and (3) the measured radiation field edge created by each leaf end is representative of that leaf's position. Data from an electronic portal imaging device (EPID) were used in a similar analysis to check the results obtained with the array. Results: The relative leaf end positions measured with the array differed from those measured with the EPID by an average of 0.11 {+-}0.09 mm per leaf. The maximum leaf positional change measured with the Profiler 2 over a 3 month period was 0.51 mm. A leaf positional accuracy of {+-}0.4 mm is easily attainable through the iterative calibration process. The method requires an average of 40 min to measure both leaf banks. Conclusions: This work demonstrates that the Profiler 2 is an effective tool for efficient and quantitative MLC quality assurance and calibration.

  17. MLC901, a traditional Chinese medicine protects the brain against global ischemia.

    PubMed

    Quintard, H; Borsotto, M; Veyssiere, J; Gandin, C; Labbal, F; Widmann, C; Lazdunski, M; Heurteaux, C

    2011-09-01

    Global ischemia leads to damage in the hippocampal CA1 region and is associated with behavioral deficits. NeuroAid (MLC601 and MLC901), a Traditional Chinese Medicine is used in China for patients after stroke. We have investigated here the effects of MLC901 on brain injury and deficits after global ischemia in the rat. Global ischemia induced by four-vessel occlusion resulted in degeneration of CA1 neurons. MLC901 (0.074 mg/ml) prevented both necrosis and apoptosis of neurons up to 3 h after ischemia. These positive MLC901 effects were associated with a decrease in Bax expression and in levels of the lipid peroxidation product malondialdehyde. Using the PI3-kinase inhibitor LY294002 we also demonstrated the critical role of the Akt pathway in MLC901-mediated neuroprotection. MLC901 enhanced neurogenesis. Furthermore, MLC901 improved functional recovery of rats after global ischemia as assessed by the Morris water maze. In this test MLC901 reduced the increase in escape latency and in swim distance induced by ischemia. MLC901 also improved post-ischemic grip strength. If observations made with rats can be extended to humans, then MLC901 will represent a novel therapeutic strategy after cardiac arrest with a clinically interesting time window of protection. PMID:21605573

  18. MLC1 protein: a likely link between leukodystrophies and brain channelopathies

    PubMed Central

    Brignone, Maria S.; Lanciotti, Angela; Camerini, Serena; De Nuccio, Chiara; Petrucci, Tamara C.; Visentin, Sergio; Ambrosini, Elena

    2015-01-01

    Megalencephalic leukoencephalopathy with subcortical cysts (MLCs) disease is a rare inherited, autosomal recessive form of childhood-onset spongiform leukodystrophy characterized by macrocephaly, deterioration of motor functions, epileptic seizures and mental decline. Brain edema, subcortical fluid cysts, myelin and astrocyte vacuolation are the histopathological hallmarks of MLC. Mutations in either the MLC1 gene (>75% of patients) or the GlialCAM gene (<20% of patients) are responsible for the disease. Recently, the GlialCAM adhesion protein was found essential for the membrane expression and function of the chloride channel ClC-2 indicating MLC disease caused by mutation in GlialCAM as the first channelopathy among leukodystrophies. On the contrary, the function of MLC1 protein, which binds GlialCAM, its functional relationship with ClC-2 and the molecular mechanisms underlying MLC1 mutation-induced functional defects are not fully understood yet. The human MLC1 gene encodes a 377-amino acid membrane protein with eight predicted transmembrane domains which shows very low homology with voltage-dependent potassium (K+) channel subunits. The high expression of MLC1 in brain astrocytes contacting blood vessels and meninges and brain alterations observed in MLC patients have led to hypothesize a role for MLC1 in the regulation of ion and water homeostasis. Recent studies have shown that MLC1 establishes structural and/or functional interactions with several ion/water channels and transporters and ion channel accessory proteins, and that these interactions are affected by MLC1 mutations causing MLC. Here, we review data on MLC1 functional properties obtained in in vitro and in vivo models and discuss evidence linking the effects of MLC1 mutations to brain channelopathies. PMID:25883547

  19. Dynamic tumor tracking using the Elekta Agility MLC

    SciTech Connect

    Fast, Martin F. Nill, Simeon Bedford, James L.; Oelfke, Uwe

    2014-11-01

    Purpose: To evaluate the performance of the Elekta Agility multileaf collimator (MLC) for dynamic real-time tumor tracking. Methods: The authors have developed a new control software which interfaces to the Agility MLC to dynamically program the movement of individual leaves, the dynamic leaf guides (DLGs), and the Y collimators (“jaws”) based on the actual target trajectory. A motion platform was used to perform dynamic tracking experiments with sinusoidal trajectories. The actual target positions reported by the motion platform at 20, 30, or 40 Hz were used as shift vectors for the MLC in beams-eye-view. The system latency of the MLC (i.e., the average latency comprising target device reporting latencies and MLC adjustment latency) and the geometric tracking accuracy were extracted from a sequence of MV portal images acquired during irradiation for the following treatment scenarios: leaf-only motion, jaw + leaf motion, and DLG + leaf motion. Results: The portal imager measurements indicated a clear dependence of the system latency on the target position reporting frequency. Deducting the effect of the target frequency, the leaf adjustment latency was measured to be 38 ± 3 ms for a maximum target speed v of 13 mm/s. The jaw + leaf adjustment latency was 53 ± 3 at a similar speed. The system latency at a target position frequency of 30 Hz was in the range of 56–61 ms for the leaves (v ≤ 31 mm/s), 71–78 ms for the jaw + leaf motion (v ≤ 25 mm/s), and 58–72 ms for the DLG + leaf motion (v ≤ 59 mm/s). The tracking accuracy showed a similar dependency on the target position frequency and the maximum target speed. For the leaves, the root-mean-squared error (RMSE) was between 0.6–1.5 mm depending on the maximum target speed. For the jaw + leaf (DLG + leaf) motion, the RMSE was between 0.7–1.5 mm (1.9–3.4 mm). Conclusions: The authors have measured the latency and geometric accuracy of the Agility MLC, facilitating its future use for clinical

  20. Developing On-line Exams.

    ERIC Educational Resources Information Center

    Hartsell, Taralynn S.; Yuen, Steve Chi-Yin

    2003-01-01

    Discusses advantages and limitations of online exams, describes available software tools for creating computer-based tests (CGI, JavaScript, commercial programs, course authoring tools), and offers suggestions for implementation. (JOW)

  1. EXPOSURE ANALYSIS MODELING SYSTEM (EXAMS)

    EPA Science Inventory

    The Exposure Analysis Modeling System (EXAMS), first published in 1982 (EPA-600/3-82-023), provides interactive computer software for formulating aquatic ecosystem models and rapidly evaluating the fate, transport, and exposure concentrations of synthetic organic chemicals--pesti...

  2. Reassessing the Annual Pelvic Exam

    MedlinePlus

    ... recommendation released Tuesday, the U.S. Preventive Services Task Force said it couldn't weigh in for or ... pelvic exams based on current evidence. "The Task Force is calling for more research to better understand ...

  3. Are Online Exams an Invitation to Cheat?

    ERIC Educational Resources Information Center

    Harmon, Oskar R.; Lambrinos, James; Kennedy, Peter, Ed.

    2008-01-01

    In this study, the authors use data from two online courses in principles of economics to estimate a model that predicts exam scores from independent variables of student characteristics. In one course, the final exam was proctored, and in the other course, the final exam was not proctored. In both courses, the first three exams were unproctored.…

  4. Physics Exams That Promote Collaborative Learning

    ERIC Educational Resources Information Center

    Wieman, Carl E.; Rieger, Georg W.; Heiner, Cynthia E.

    2014-01-01

    The two-stage exam is a relatively simple way to introduce collaborative learning and formative assessment into an exam. Their use is rapidly growing in the physics department at the University of British Columbia, as both students and faculty find them rewarding. In a two-stage exam students first complete and turn in the exam individually, and…

  5. Student Exam Creation as a Learning Tool

    ERIC Educational Resources Information Center

    Brink, Jan; Capps, Emerson; Sutko, Al

    2004-01-01

    The purpose of this study was to determine if there is a relationship between: 1) comprehensiveness of student developed model tests and final exam score, 2) the quality of student developed model tests and answer keys combined, and final exam score, and 3) student developed model test similarity to instructor final exam and final exam score.…

  6. TomoTherapy MLC verification using exit detector data

    SciTech Connect

    Chen Quan; Westerly, David; Fang Zhenyu; Sheng, Ke; Chen Yu

    2012-01-15

    Purpose: Treatment delivery verification (DV) is important in the field of intensity modulated radiation therapy (IMRT). While IMRT and image guided radiation therapy (IGRT), allow us to create more conformal plans and enables the use of tighter margins, an erroneously executed plan can have detrimental effects on the treatment outcome. The purpose of this study is to develop a DV technique to verify TomoTherapy's multileaf collimator (MLC) using the onboard mega-voltage CT detectors. Methods: The proposed DV method uses temporal changes in the MVCT detector signal to predict actual leaf open times delivered on the treatment machine. Penumbra and scattered radiation effects may produce confounding results when determining leaf open times from the raw detector data. To reduce the impact of the effects, an iterative, Richardson-Lucy (R-L) deconvolution algorithm is applied. Optical sensors installed on each MLC leaf are used to verify the accuracy of the DV technique. The robustness of the DV technique is examined by introducing different attenuation materials in the beam. Additionally, the DV technique has been used to investigate several clinical plans which failed to pass delivery quality assurance (DQA) and was successful in identifying MLC timing discrepancies as the root cause. Results: The leaf open time extracted from the exit detector showed good agreement with the optical sensors under a variety of conditions. Detector-measured leaf open times agreed with optical sensor data to within 0.2 ms, and 99% of the results agreed within 8.5 ms. These results changed little when attenuation was added in the beam. For the clinical plans failing DQA, the dose calculated from reconstructed leaf open times played an instrumental role in discovering the root-cause of the problem. Throughout the retrospective study, it is found that the reconstructed dose always agrees with measured doses to within 1%. Conclusions: The exit detectors in the TomoTherapy treatment systems

  7. The Use of NeuroAiD (MLC601) in Postischemic Stroke Patients

    PubMed Central

    Navarro, Jose C.; Molina, Mark C.; Baroque II, Alejandro C.; Lokin, Johnny K.

    2012-01-01

    Aim. We aimed to assess the efficacy of MLC601 on functional recovery in patients given MLC601 after an ischemic stroke. Methods. This is a retrospective cohort study comparing poststroke patients given open-label MLC601 (n = 30; 9 female) for three months and matching patients who did not receive MLC601 from our Stroke Data Bank. Outcome assessed was modified Rankin Scale (mRS) at three months and analyzed according to: (1) achieving a score of 0-2, (2) achieving a score of 0-1, and (3) mean change in scores from baseline. Results. At three months, 21 patients on MLC601 became independent as compared to 17 patients not on MLC601 (OR 1.79; 95% CI 0.62–5.2; P = 0.29). There were twice as many patients (n = 16) on MLC601 who attained mRS scores similar to their prestroke state than in the non-MLC601 group (n = 8) (OR 3.14; 95% CI 1.1–9.27; P = 0.038). Mean improvement in mRS from baseline was better in the MLC601 group than in the non-MLC601 group (−1.7 versus −0.9; mean difference −0.73; 95% CI −1.09 to −0.38; P < 0.001). Conclusion. MLC601 improves functional recovery at 3 months postischemic stroke. An ongoing large randomized control trial of MLC601 will help validate these results. PMID:23304514

  8. From Exam to Education: The Math Exam/Education Resources

    ERIC Educational Resources Information Center

    Bruni, Carmen; Koch, Christina; Konrad, Bernhard; Lindstrom, Michael; Moyles, Iain; Thompson, Will

    2016-01-01

    The Math Exam/Education Resources (MER) is an open online learning resource hosted at The University of British Columbia (UBC), aimed at providing mathematics education resources for students and instructors at UBC. In this paper, there will be a discussion of the motivation for creating this resource on the MediaWiki platform, key features of the…

  9. Are simple IMRT beams more robust against MLC error? Exploring the impact of MLC errors on planar quality assurance and plan quality for different complexity beams.

    PubMed

    Wang, Jiazhou; Jin, Xiance; Peng, Jiayuan; Xie, Jiang; Chen, Junchao; Hu, Weigang

    2016-01-01

    This study investigated the impact of beam complexities on planar quality assur-ance and plan quality robustness by introducing MLC errors in intensity-modulate radiation therapy. Forty patients' planar quality assurance (QA) plans were enrolled in this study, including 20 dynamic MLC (DMLC) IMRT plans and 20 static MLC (SMLC) IMRT plans. The total beam numbers were 150 and 160 for DMLC and SMLC, respectively. Six different magnitudes of MLC errors were introduced to these beams. Gamma pass rates were calculated by comparing error-free fluence and error-induced fluence. The plan quality variation was acquired by comparing PTV coverage. Eight complexity scores were calculated based on the beam flu-ence and the MLC sequence. The complexity scores include fractal dimension, monitor unit, modulation index, fluence map complexity, weighted average of field area, weighted average of field perimeter, and small aperture ratio (< 5 cm2 and < 50cm2). The Spearman's rank correlation coefficient was calculated to analyze the correlation between these scores and gamma pass rate and plan quality varia-tion. For planar QA, the most significant complexity index was fractal dimension for DMLC (p = -0.40) and weighted segment area for SMLC (p = 0.27) at low magnitude MLC error. For plan quality, the most significant complexity index was weighted segment perimeter for DMLC (p = 0.56) and weighted segment area for SMLC (p= 0.497) at low magnitude MLC error. The sensitivity of planar QA was weakly associated with the field complexity with low magnitude MLC error, but the plan quality robustness was associated with beam complexity. Plans with simple beams were more robust to MLC error. PMID:27167272

  10. Exam Schools from the Inside

    ERIC Educational Resources Information Center

    Finn, Chester E., Jr.; Hockett, Jessica

    2012-01-01

    Sometimes called "exam schools," academically selective institutions have long been a part of the American secondary-education landscape. The schools are diverse in origin and purpose. No single catalyst describes why or how they began as or morphed into academically selective institutions. A number of them were products of the country's efforts…

  11. Stool ova and parasites exam

    MedlinePlus

    Parasites and stool ova exam ... order this test if you have signs of parasites, diarrhea that does not go away, or other ... There are no parasites or eggs in the stool sample. Talk to your health care provider about the meaning of your specific test ...

  12. Leaf transmission reduction using moving jaws for dynamic MLC IMRT

    SciTech Connect

    Schmidhalter, D.; Fix, M. K.; Niederer, P.; Mini, R.; Manser, P.

    2007-09-15

    The aim of this work is to investigate to what extent it is possible to use the secondary collimator jaws to reduce the transmitted radiation through the multileaf collimator (MLC) during an intensity modulated radiation therapy (IMRT). A method is developed and introduced where the jaws follow the open window of the MLC dynamically (dJAW method). With the aid of three academic cases (Closed MLC, Sliding-gap, and Chair) and two clinical cases (prostate and head and neck) the feasibility of the dJAW method and the influence of this method on the applied dose distributions are investigated. For this purpose the treatment planning system Eclipse and the Research-Toolbox were used as well as measurements within a solid water phantom were performed. The transmitted radiation through the closed MLC leads to an inhomogeneous dose distribution. In this case, the measured dose within a plane perpendicular to the central axis differs up to 40% (referring to the maximum dose within this plane) for 6 and 15 MV. The calculated dose with Eclipse is clearly more homogeneous. For the Sliding-gap case this difference is still up to 9%. Among other things, these differences depend on the depth of the measurement within the solid water phantom and on the application method. In the Chair case, the dose in regions where no dose is desired is locally reduced by up to 50% using the dJAW method instead of the conventional method. The dose inside the chair-shaped region decreased up to 4% if the same number of monitor units (MU) as for the conventional method was applied. The undesired dose in the volume body minus the planning target volume in the clinical cases prostate and head and neck decreased up to 1.8% and 1.5%, while the number of the applied MU increased up to 3.1% and 2.8%, respectively. The new dJAW method has the potential to enhance the optimization of the conventional IMRT to a further step.

  13. What Is a Comprehensive Dilated Eye Exam?

    MedlinePlus

    ... su oculista What is a comprehensive dilated eye exam? You may think your eyes are healthy, but ... eye care professional for a comprehensive dilated eye exam is the only way to really be sure. ...

  14. Combining MLC and SVM Classifiers for Learning Based Decision Making: Analysis and Evaluations

    PubMed Central

    Zhang, Yi; Ren, Jinchang; Jiang, Jianmin

    2015-01-01

    Maximum likelihood classifier (MLC) and support vector machines (SVM) are two commonly used approaches in machine learning. MLC is based on Bayesian theory in estimating parameters of a probabilistic model, whilst SVM is an optimization based nonparametric method in this context. Recently, it is found that SVM in some cases is equivalent to MLC in probabilistically modeling the learning process. In this paper, MLC and SVM are combined in learning and classification, which helps to yield probabilistic output for SVM and facilitate soft decision making. In total four groups of data are used for evaluations, covering sonar, vehicle, breast cancer, and DNA sequences. The data samples are characterized in terms of Gaussian/non-Gaussian distributed and balanced/unbalanced samples which are then further used for performance assessment in comparing the SVM and the combined SVM-MLC classifier. Interesting results are reported to indicate how the combined classifier may work under various conditions. PMID:26089862

  15. Combining MLC and SVM Classifiers for Learning Based Decision Making: Analysis and Evaluations.

    PubMed

    Zhang, Yi; Ren, Jinchang; Jiang, Jianmin

    2015-01-01

    Maximum likelihood classifier (MLC) and support vector machines (SVM) are two commonly used approaches in machine learning. MLC is based on Bayesian theory in estimating parameters of a probabilistic model, whilst SVM is an optimization based nonparametric method in this context. Recently, it is found that SVM in some cases is equivalent to MLC in probabilistically modeling the learning process. In this paper, MLC and SVM are combined in learning and classification, which helps to yield probabilistic output for SVM and facilitate soft decision making. In total four groups of data are used for evaluations, covering sonar, vehicle, breast cancer, and DNA sequences. The data samples are characterized in terms of Gaussian/non-Gaussian distributed and balanced/unbalanced samples which are then further used for performance assessment in comparing the SVM and the combined SVM-MLC classifier. Interesting results are reported to indicate how the combined classifier may work under various conditions. PMID:26089862

  16. Exit Exam as Academic Performance Indicator

    ERIC Educational Resources Information Center

    Al Ahmad, Mahmoud; Al Marzouqi, Ali H.; Hussien, Mousa

    2014-01-01

    This paper focuses on the impact of exit exams on different elements of the educational process, namely: curriculum development, students and instructors. A 50-question multiple-choice Exit Exam was prepared by Electrical Engineering (EE) faculty members covering a poll of questions from EE core courses. A copy of the Exit Exam applied during each…

  17. Cumulative Exams in the Introductory Psychology Course

    ERIC Educational Resources Information Center

    Lawrence, Natalie K.

    2013-01-01

    Many teachers require their students to take cumulative exams, but there are surprisingly few studies that examine the benefits of such exams. The purpose of this study was to determine whether introductory psychology students who take cumulative exams throughout the semester would have better long-term retention than students who take a…

  18. Translating bed total body irradiation lung shielding and dose optimization using asymmetric MLC apertures.

    PubMed

    Ahmed, Shahbaz; Brown, Derek; Ahmed, Saad B S; Kakakhel, Muhammad B; Muhammad, Wazir; Hussain, Amjad

    2016-01-01

    A revised translating bed total body irradiation (TBI) technique is developed for shielding organs at risk (lungs) to tolerance dose limits, and optimizing dose distribution in three dimensions (3D) using an asymmetrically-adjusted, dynamic multileaf collimator. We present a dosimetric comparison of this technique with a previously developed symmetric MLC-based TBI technique. An anthropomor-phic RANDO phantom is CT scanned with 3 mm slice thickness. Radiological depths (RD) are calculated on individual CT slices along the divergent ray lines. Asymmetric MLC apertures are defined every 9 mm over the phantom length in the craniocaudal direction. Individual asymmetric MLC leaf positions are optimized based on RD values of all slices for uniform dose distributions. Dose calculations are performed in the Eclipse treatment planning system over these optimized MLC apertures. Dose uniformity along midline of the RANDO phantom is within the confidence limit (CL) of 2.1% (with a confidence probability p = 0.065). The issue of over- and underdose at the interfaces that is observed when symmetric MLC apertures are used is reduced from more than ± 4% to less than ± 1.5% with asymmetric MLC apertures. Lungs are shielded by 20%, 30%, and 40% of the prescribed dose by adjusting the MLC apertures. Dose-volume histogram analysis confirms that the revised technique provides effective lung shielding, as well as a homogeneous dose coverage to the whole body. The asymmetric technique also reduces hot and cold spots at lung-tissue interfaces compared to previous symmetric MLC-based TBI technique. MLC-based shielding of OARs eliminates the need to fabricate and setup cumbersome patient-specific physical blocks. PMID:27074477

  19. The art of a pediatric exam.

    PubMed

    Riley, Debra

    2014-06-15

    This article discusses incorporating "artistry" into a primary care pediatric exam, a technique that considers a child's cognitive developmental stage, previous medical experiences, and the family's general stressors and fears. Benefits of using the artistic exam technique include decreased fear and anxiety for both the child and parent and fewer unnecessary diagnostic tests. The artistic exam has also been shown to improve adherence to pre- and postcare instructions and improved quality outcomes. PMID:24841465

  20. The first clinical implementation of electromagnetic transponder-guided MLC tracking

    PubMed Central

    Keall, Paul J.; Colvill, Emma; O’Brien, Ricky; Ng, Jin Aun; Poulsen, Per Rugaard; Eade, Thomas; Kneebone, Andrew; Booth, Jeremy T.

    2014-01-01

    Purpose: We report on the clinical process, quality assurance, and geometric and dosimetric results of the first clinical implementation of electromagnetic transponder-guided MLC tracking which occurred on 28 November 2013 at the Northern Sydney Cancer Centre. Methods: An electromagnetic transponder-based positioning system (Calypso) was modified to send the target position output to in-house-developed MLC tracking code, which adjusts the leaf positions to optimally align the treatment beam with the real-time target position. Clinical process and quality assurance procedures were developed and performed. The first clinical implementation of electromagnetic transponder-guided MLC tracking was for a prostate cancer patient being treated with dual-arc VMAT (RapidArc). For the first fraction of the first patient treatment of electromagnetic transponder-guided MLC tracking we recorded the in-room time and transponder positions, and performed dose reconstruction to estimate the delivered dose and also the dose received had MLC tracking not been used. Results: The total in-room time was 21 min with 2 min of beam delivery. No additional time was needed for MLC tracking and there were no beam holds. The average prostate position from the initial setup was 1.2 mm, mostly an anterior shift. Dose reconstruction analysis of the delivered dose with MLC tracking showed similar isodose and target dose volume histograms to the planned treatment and a 4.6% increase in the fractional rectal V60. Dose reconstruction without motion compensation showed a 30% increase in the fractional rectal V60 from that planned, even for the small motion. Conclusions: The real-time beam-target correction method, electromagnetic transponder-guided MLC tracking, has been translated to the clinic. This achievement represents a milestone in improving geometric and dosimetric accuracy, and by inference treatment outcomes, in cancer radiotherapy. PMID:24506591

  1. The first clinical implementation of electromagnetic transponder-guided MLC tracking

    SciTech Connect

    Keall, Paul J. O’Brien, Ricky; Ng, Jin Aun; Colvill, Emma; Poulsen, Per Rugaard; Eade, Thomas; Kneebone, Andrew; Booth, Jeremy T.

    2014-02-15

    Purpose: We report on the clinical process, quality assurance, and geometric and dosimetric results of the first clinical implementation of electromagnetic transponder-guided MLC tracking which occurred on 28 November 2013 at the Northern Sydney Cancer Centre. Methods: An electromagnetic transponder-based positioning system (Calypso) was modified to send the target position output to in-house-developed MLC tracking code, which adjusts the leaf positions to optimally align the treatment beam with the real-time target position. Clinical process and quality assurance procedures were developed and performed. The first clinical implementation of electromagnetic transponder-guided MLC tracking was for a prostate cancer patient being treated with dual-arc VMAT (RapidArc). For the first fraction of the first patient treatment of electromagnetic transponder-guided MLC tracking we recorded the in-room time and transponder positions, and performed dose reconstruction to estimate the delivered dose and also the dose received had MLC tracking not been used. Results: The total in-room time was 21 min with 2 min of beam delivery. No additional time was needed for MLC tracking and there were no beam holds. The average prostate position from the initial setup was 1.2 mm, mostly an anterior shift. Dose reconstruction analysis of the delivered dose with MLC tracking showed similar isodose and target dose volume histograms to the planned treatment and a 4.6% increase in the fractional rectal V{sub 60}. Dose reconstruction without motion compensation showed a 30% increase in the fractional rectal V{sub 60} from that planned, even for the small motion. Conclusions: The real-time beam-target correction method, electromagnetic transponder-guided MLC tracking, has been translated to the clinic. This achievement represents a milestone in improving geometric and dosimetric accuracy, and by inference treatment outcomes, in cancer radiotherapy.

  2. The Escherichia coli glucose transporter enzyme IICBGlc recruits the global repressor Mlc

    PubMed Central

    Nam, Tae-Wook; Cho, Seung-Hyon; Shin, Dongwoo; Kim, Ja-Hee; Jeong, Jin-Young; Lee, Joon-Hee; Roe, Jung-Hye; Peterkofsky, Alan; Kang, Sa-Ouk; Ryu, Sangryeol; Seok, Yeong-Jae

    2001-01-01

    In addition to effecting the catalysis of sugar uptake, the bacterial phosphoenolpyruvate:sugar phosphotransferase system regulates a variety of physiological processes. Exposure of cells to glucose can result in repression or induction of gene expression. While the mechanism for carbon catabolite repression by glucose was well documented, that for glucose induction was not clearly understood in Escherichia coli. Recently, glucose induction of several E.coli genes has been shown to be mediated by the global repressor Mlc. Here, we elucidate a general mechanism for glucose induction of gene expression in E.coli, revealing a novel type of regulatory circuit for gene expression mediated by the phosphorylation state-dependent interaction of a membrane-bound protein with a repressor. The dephospho-form of enzyme IICBGlc, but not its phospho-form, interacts directly with Mlc and induces transcription of Mlc-regulated genes by displacing Mlc from its target sequences. Therefore, the glucose induction of Mlc-regulated genes is caused by dephosphorylation of the membrane-bound transporter enzyme IICBGlc, which directly recruits Mlc to derepress its regulon. PMID:11157755

  3. Real-time dynamic MLC tracking for inversely optimized arc radiotherapy

    PubMed Central

    Falk, Marianne; Rosenschöld, Per Munck Af; Keall, Paul; Cattell, Herbert; Cho, Byung Chul; Poulsen, Per; Povzner, Sergey; Sawant, Amit; Zimmerman, Jens; Korreman, Stine

    2010-01-01

    Background and Purpose Motion compensation with MLC tracking was tested for inversely optimized arc radiotherapy with special attention to the impact of the size of the target displacements and the angle of the leaf trajectory. Material and methods An MLC tracking algorithm was used to adjust the MLC positions according to the target movements using information from an optical real-time positioning management system. Two plans with collimator angles of 45° and 90°, respectively, were delivered and measured using the Delta4® dosimetric device moving in the superior-inferior direction with peak-to-peak displacements of 5, 10, 15, 20 and 25 mm and a cycle time of 6 s. Results Gamma index evaluation for plan delivery with MLC tracking gave a pass rate higher than 98% for criteria 3% and 3 mm for both plans and for all sizes of the target displacement. With no motion compensation, the average pass rate was 75% for plan 1 and 70% for plan 2 for 25 mm peak-to-peak displacement. Conclusion MLC tracking improves the accuracy of inversely optimized arc delivery for the cases studied. With MLC tracking, the dosimetric accuracy was independent of the magnitude of the peak-to-peak displacement of the target and not significantly affected by the angle between the leaf trajectory and the target movements. PMID:20089322

  4. Functional Studies of MLC1 Mutations in Chinese Patients with Megalencephalic Leukoencephalopathy with Subcortical Cysts

    PubMed Central

    Shang, Jing; Kou, Liping; Guo, Mangmang; Wu, Ye; Gu, Qiang; Colman, David; Wu, Xiru; Jiang, Yuwu

    2012-01-01

    Megalencephalic leukoencephalopathy with subcortical cysts (MLC, MIM# 604004) is an autosomal recessive inherited disease mostly resulting from MLC1 mutations. In this study, we finished the functional analysis of MLC1 mutations identified recently in Chinese patients, including five newly described missense mutations (R22Q, A32V, G73E, A275T, Y278H), one known nonsense mutation (Y198X), and two known missense mutations (S69L, T118M). We found MLC1wt was localized to the cell periphery, whereas mutant R22Q, A32V, G73E, S69L and T118M were trapped in the lumen of endoplasmic reticulum (ER) when we transfected the wild-type and mutant MLC1 in U373MG cells. Compared to wild type, the mutant G73E, T118M, Y198X and A275T transcript decreased and all mutants except R22Q had lower protein expression in transfected U373MG cells. Therefore, we propose that all these eight MLC1 mutations had functional effect either on their protein/mRNA expression, or on their intracellular protein localization, or both. PMID:22416245

  5. Detecting MLC errors in stereotactic radiotherapy plans with a liquid filled ionization chamber array.

    PubMed

    O'Connor, Patrick; Seshadri, Venkatakrisnan; Charles, Paul

    2016-03-01

    Quality assurance of stereotactic radiotherapy demands the use of equipment with the highest resolution and sensitivity available. This study examines the sensitivity of a commercially available liquid-filled ionization chamber array-the Octavius 1000 SRS (PTW, Frieburg, Germany) for detecting small (sub-millimetre) multi-leaf collimator (MLC) alignment errors in static square fields (side length 16-40 mm). Furthermore, the effectiveness of detecting small MLC errors in clinical stereotactic radiotherapy patient plans using the device was also evaluated. The commonly used gamma pass rate metric (of the measurements compared with treatment planning system generated results) was used. The gamma pass rates were then evaluated as a function of MLC position error (MLC error size 0.1-2.5 mm). The detector array exhibited a drop in pass rate between plans without error and those which had MLC errors induced. For example a drop in pass rate of 4.5 % (gamma criteria 3 %, 1 mm) was observed when a 0.8 mm error was introduced into a 16 mm square field. Furthermore the drop in pass rate increased as the MLC position error increased. This study showed that the Octavius 1000 SRS array could be a useful tool for applications requiring the detection of small geometric delivery uncertainties. PMID:26979835

  6. Profile of State High School Exit Exam Policies. Tennessee

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Tennessee's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam first…

  7. Profile of State High School Exit Exam Policies. Oregon

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Oregon's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam first…

  8. Profile of State High School Exit Exam Policies. Nevada

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Nevada's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam first…

  9. Profile of State High School Exit Exam Policies. New Mexico

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on New Mexico's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam first…

  10. Profile of State High School Exit Exam Policies. Georgia

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Georgia's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam first…

  11. Profile of State High School Exit Exam Policies. New Jersey

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on New Jersey's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam first…

  12. Profile of State High School Exit Exam Policies. New York

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on New York's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam first…

  13. Profile of State High School Exit Exam Policies. Ohio

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Ohio's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam first…

  14. Profile of State High School Exit Exam Policies. Oklahoma

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Oklahoma's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam first…

  15. Tailoring the Preparticipation Exam to Female Athletes.

    ERIC Educational Resources Information Center

    Johnson, Mimi D.

    1992-01-01

    Discusses the basics of the preparticipation exam, focusing on aspects specific to females, such as menstrual dysfunction, disordered eating, and orthopedic problems such as scoliosis and patellofemoral pain. Health history questionnaire and other parts of the exam are included in six tables. (SM)

  16. Physics Exams that Promote Collaborative Learning

    NASA Astrophysics Data System (ADS)

    Wieman, Carl E.; Rieger, Georg W.; Heiner, Cynthia E.

    2014-01-01

    The two-stage exam is a relatively simple way to introduce collaborative learning and formative assessment into an exam. Their use is rapidly growing in the physics department at the University of British Columbia, as both students and faculty find them rewarding. In a two-stage exam students first complete and turn in the exam individually, and then, working in small groups, answer the exam questions again. During the second stage, the room is filled with spirited and effective debate with nearly every student participating. This provides students with immediate targeted feedback supplied by discussions with their peers. Furthermore, we see indications that the use of this exam format not only ensures consistency across interactive course components, but it also positively impacts how students approach the other collaborative course components. This is accomplished without losing the summative assessment of individual performance that is the expectation of exams for most instructors. In this paper we describe how to implement two-stage exams and provide arguments why they should be part of physics courses that use interactive engagement and social/collaborative learning methods.

  17. From Exam Factories to Communities of Discovery

    ERIC Educational Resources Information Center

    Coffield, Frank; Williamson, Bill

    2011-01-01

    The British current model of education has turned schools into exam factories and further education colleges and universities into skills factories for British industry. In their book, "From Exam Factories to Communities of Discovery: the Democratic Route," the authors offer an alternative way of thinking and talking about education, as well as…

  18. Hyperosmotic stress activates Rho: differential involvement in Rho kinase-dependent MLC phosphorylation and NKCC activation.

    PubMed

    Di Ciano-Oliveira, Caterina; Sirokmány, Gábor; Szászi, Katalin; Arthur, William T; Masszi, András; Peterson, Mark; Rotstein, Ori D; Kapus, András

    2003-09-01

    Hyperosmotic stress initiates adaptive responses, including phosphorylation of myosin light chain (MLC) and concomitant activation of Na+-K+-Cl- cotransporter (NKCC). Because the small GTPase Rho is a key regulator of MLC phosphorylation, we investigated 1) whether Rho is activated by hyperosmotic stress, and if so, what the triggering factors are, and 2) whether the Rho/Rho kinase (ROK) pathway is involved in MLC phosphorylation and NKCC activation. Rho activity was measured in tubular epithelial cells by affinity pulldown assay. Hyperosmolarity induced rapid (<1 min) and sustained (>20 min) Rho activation that was proportional to the osmotic concentration and reversed within minutes upon restoration of isotonicity. Both decreased cell volume at constant ionic strength and elevated total ionic strength at constant cell volume were capable of activating Rho. Changes in [Na+] and [K+] at normal total salinity failed to activate Rho, and Cl- depletion did not affect the hyperosmotic response. Thus alterations in cellular volume and ionic strength but not individual ion concentrations seem to be the critical triggering factors. Hyperosmolarity induced mono- and diphosphorylation of MLC, which was abrogated by the Rho-family blocker Clostridium toxin B. ROK inhibitor Y-27632 suppressed MLC phosphorylation under isotonic conditions and prevented its rise over isotonic levels in hypertonically stimulated cells. ML-7 had a smaller inhibitory effect. In contrast, it abolished the hypertonic activation of NKCC, whereas Y-27632 failed to inhibit this response. Thus hyperosmolarity activates Rho, and Rho/ROK pathway contributes to basal and hyperosmotic MLC phosphorylation. However, the hypertonic activation of NKCC is ROK independent, implying that the ROK-dependent component of MLC phosphorylation can be uncoupled from NKCC activation. PMID:12748065

  19. SU-E-T-195: Gantry Angle Dependency of MLC Leaf Position Error

    SciTech Connect

    Ju, S; Hong, C; Kim, M; Chung, K; Kim, J; Han, Y; Ahn, S; Chung, S; Shin, E; Shin, J; Kim, H; Kim, D; Choi, D

    2014-06-01

    Purpose: The aim of this study was to investigate the gantry angle dependency of the multileaf collimator (MLC) leaf position error. Methods: An automatic MLC quality assurance system (AutoMLCQA) was developed to evaluate the gantry angle dependency of the MLC leaf position error using an electronic portal imaging device (EPID). To eliminate the EPID position error due to gantry rotation, we designed a reference maker (RM) that could be inserted into the wedge mount. After setting up the EPID, a reference image was taken of the RM using an open field. Next, an EPID-based picket-fence test (PFT) was performed without the RM. These procedures were repeated at every 45° intervals of the gantry angle. A total of eight reference images and PFT image sets were analyzed using in-house software. The average MLC leaf position error was calculated at five pickets (-10, -5, 0, 5, and 10 cm) in accordance with general PFT guidelines using in-house software. This test was carried out for four linear accelerators. Results: The average MLC leaf position errors were within the set criterion of <1 mm (actual errors ranged from -0.7 to 0.8 mm) for all gantry angles, but significant gantry angle dependency was observed in all machines. The error was smaller at a gantry angle of 0° but increased toward the positive direction with gantry angle increments in the clockwise direction. The error reached a maximum value at a gantry angle of 90° and then gradually decreased until 180°. In the counter-clockwise rotation of the gantry, the same pattern of error was observed but the error increased in the negative direction. Conclusion: The AutoMLCQA system was useful to evaluate the MLC leaf position error for various gantry angles without the EPID position error. The Gantry angle dependency should be considered during MLC leaf position error analysis.

  20. A New Comprehensive Final Exam

    NASA Astrophysics Data System (ADS)

    Bhavsar, Suketu P.

    2015-01-01

    Instructors aspire for students to master all the material covered. The final exam should assess the breadth and depth of their learning and be a significant basis for the final grade. I insist on a comprehensive final because I want students to review early material in light of later topics. I believe that this helps students create connections, integrate understanding, and retain knowledge for the long term. For non-science majors, reviewing and retaining the large amount of astronomy material is daunting. I experimented with a final exam format that calmed their fears and encouraged thorough review. It is only practical for a class of about twenty students or less. I provided a number of challenging conceptual and problem solving questions (at least as many as there were students), crafted to interconnect and span the entire range of topics. The order of the questions reflected the sequence in which the topics had been discussed. Students received these questions in ample time to prepare prior to the final. A student could bring up to 5 standard sheets of notes to the final. At the final, each student picked a number out of a hat. This was the question they had to answer in a 5-minute presentation. They were allowed 15 minutes for a final preparation during which they could use their 5 pages of notes. The presentations were given in order, 1- 20. Written comments on at least 10 other talks, explaining what was missed or correcting a mistake were required. They were graded both on their talk and on their comments. This format required students to be prepared for any question and encouraged interaction and communication while studying. Knowing the questions beforehand provided a guide to their studying as well as allayed their fears about what could be asked. The students also received guidance to what constituted a good answer, namely accuracy (correct scientific argument, appropriate facts, no irrelevant material), thoroughness (answered the complete questions

  1. Comparision of beam data requirements for MLC commissioning on a TPS

    NASA Astrophysics Data System (ADS)

    Solaiappan, Gopi; Singaravelu, Ganesan; Prakasarao, Aruna; Supe, Sanjay S.

    2008-01-01

    The treatment planning system (TPS) has become a key element in the radiotherapy process with the introduction of computer tomography (CT) based 3D conformal treatment planning. Commissioning of a MLC on a TPS either for conformal radiotherapy or intensity modulated radiation therapy (IMRT) requires beam data to be generated on a linear accelerator. Most of the TPS require these beam data to be generated with routine collimator jaws. However some TPS demand the data to be provided for MLC shaped fields. This prompted us to investigate whether beam data with jaws differ than that with MLC and whether the jaw based beam data would suffice for the commissioning of a MLC on a TPS. Beam data like percentage depth dose (PDD), cross beam profiles and output factors was acquired for jaws and MLC defined square fields for 6, 10 and 23 MV photon beams. Percentage depth dose and cross beam profiles were acquired with a radiation field analyzer RFA-200, CC13-S ion chambers with active volume of 0.13 cm3 and OmniPro-Accept software from Scanditronix-Wellhofer. A Medtec-TG51 water tank with Max-4000 electrometer and 0.6 cc PTW ionization chamber and a mini phantom from Standard Imaging was utilized for output measurements for millennium-120 MLC (Varian Medical Systems) and SRS diode detector (Scanditronix-Wellhofer) of 0.6 mm diameter of active area and 0.3 mm of active volume thickness for micro-MLC (BrainLab). The difference in PDD in the build-up region for millennium MLC was ±1.0% for 6 MV photons. For 10 MV photons the PDD difference was within ±4.0%. The difference in PDD for 23 MV photons ranged from 0% to 40.0%. PDD difference from build-up depth to about 28 cm was within ±1.0%. Difference in PDD crossed ±1.0% at 30 cm depth for 6 MV photons. The difference in PDD in the build-up region for mMLC was ±8.0% for 6 MV photons. For the smallest field size studied with micro-MLC i.e. 0.6 × 0.6 cm2 difference in PDD was more than ±1.0% in the build-up region and beyond a

  2. Dose domain regularization of MLC leaf patterns for highly complex IMRT plans

    SciTech Connect

    Nguyen, Dan; Yu, Victoria Y.; Ruan, Dan; Cao, Minsong; Low, Daniel A.; Sheng, Ke; O’Connor, Daniel

    2015-04-15

    Purpose: The advent of automated beam orientation and fluence optimization enables more complex intensity modulated radiation therapy (IMRT) planning using an increasing number of fields to exploit the expanded solution space. This has created a challenge in converting complex fluences to robust multileaf collimator (MLC) segments for delivery. A novel method to regularize the fluence map and simplify MLC segments is introduced to maximize delivery efficiency, accuracy, and plan quality. Methods: In this work, we implemented a novel approach to regularize optimized fluences in the dose domain. The treatment planning problem was formulated in an optimization framework to minimize the segmentation-induced dose distribution degradation subject to a total variation regularization to encourage piecewise smoothness in fluence maps. The optimization problem was solved using a first-order primal-dual algorithm known as the Chambolle-Pock algorithm. Plans for 2 GBM, 2 head and neck, and 2 lung patients were created using 20 automatically selected and optimized noncoplanar beams. The fluence was first regularized using Chambolle-Pock and then stratified into equal steps, and the MLC segments were calculated using a previously described level reducing method. Isolated apertures with sizes smaller than preset thresholds of 1–3 bixels, which are square units of an IMRT fluence map from MLC discretization, were removed from the MLC segments. Performance of the dose domain regularized (DDR) fluences was compared to direct stratification and direct MLC segmentation (DMS) of the fluences using level reduction without dose domain fluence regularization. Results: For all six cases, the DDR method increased the average planning target volume dose homogeneity (D95/D5) from 0.814 to 0.878 while maintaining equivalent dose to organs at risk (OARs). Regularized fluences were more robust to MLC sequencing, particularly to the stratification and small aperture removal. The maximum and

  3. Indian Reservations

    ERIC Educational Resources Information Center

    Weewish Tree, 1974

    1974-01-01

    Answers to questions asked by junior high school students about American Indian reservations are given. The areas covered include nearly every facet of reservation life from the first Federal issuance of particles of land to the American Indians to present conditions on the reservations. (AH)

  4. Expedition 35/36 Final Exams

    NASA Video Gallery

    Three Expedition 35/36 crew members prepare for their final exams in their Sokol launch and entry suits at the Gagarin Cosmonaut Training Center in Star City, Russia. NASA astronaut Chris Cassidy a...

  5. Expedition 32 Final Soyuz Qualification Exams

    NASA Video Gallery

    Expedition 32 Flight Engineers Suni Williams, Yuri Malenchenko and Aki Hoshide take their final Soyuz systems qualification exams at the Gagarin Cosmonaut Training Center in Star City, Russia. The ...

  6. Wogonin inhibits LPS-induced vascular permeability via suppressing MLCK/MLC pathway.

    PubMed

    Huang, Yujie; Luo, Xuwei; Li, Xiaorui; Song, Xiuming; Wei, Libin; Li, Zhiyu; You, Qidong; Guo, Qinglong; Lu, Na

    2015-09-01

    Wogonin, a naturally occurring monoflavonoid extracted from the root of Scutellaria baicalensis Georgi, has been shown to have anti-inflammatory and anti-tumor activities and inhibits oxidant stress-induced vascular permeability. However, the influence of wogonin on vascular hyperpermeability induced by overabounded inflammatory factors often appears in inflammatory diseases and tumor is not well known. In this study, we evaluate the effects of wogonin on LPS induced vascular permeability in human umbilical vein endothelial cells (HUVECs) and investigate the underlying mechanisms. We find that wogonin suppresses the LPS-stimulated hyperactivity and cytoskeleton remodeling of HUVECs, promotes the expression of junctional proteins including VE-Cadherin, Claudin-5 and ZO-1, as well as inhibits the invasion of MDA-MB-231 across EC monolayer. Miles vascular permeability assay proves that wogonin can restrain the extravasated Evans in vivo. The mechanism studies reveal that the expressions of TLR4, p-PLC, p-MLCK and p-MLC are decreased by wogonin without changing the total steady state protein levels of PLC, MLCK and MLC. Moreover, wogonin can also inhibit KCl-activated MLCK/MLC pathway, and further affect vascular permeability. Significantly, compared with wortmannin, the inhibitor of MLCK/MLC pathway, wogonin exhibits similar inhibition effects on the expression of p-MLCK, p-MLC and LPS-induced vascular hyperpermeability. Taken together, wogonin can inhibit LPS-induced vascular permeability by suppressing the MLCK/MLC pathway, suggesting a therapeutic potential for the diseases associated with the development of both inflammatory and tumor. PMID:25956732

  7. Anatomy-based, patient-specific VMAT QA using EPID or MLC log files.

    PubMed

    Defoor, Dewayne L; Vazquez-Quino, Luis A; Mavroidis, Panayiotis; Papanikolaou, Nikos; Stathakis, Sotirios

    2015-01-01

    In this project, we investigated the use of an electronic portal imaging device (EPID), together with the treatment planning system (TPS) and MLC log files, to determine the delivered doses to the patient and evaluate the agreement between the treatment plan and the delivered dose distribution. The QA analysis results are presented for 15 VMAT patients using the EPID measurements, the ScandiDos Delta4 dosimeter, and the beam fluence calculated from the multileaf collimator (MLC) log file. EPID fluence images were acquired in continuous acquisition mode for each of the patients and they were processed through an in-house MATLAB program to create an opening density matrix (ODM), which was used as the input fluence for the dose calculation in the TPS (Pinnacle3). The EPID used in this study was the aSi1000 Varian on a Novalis TX linac equipped with high-definition MLC. The actual MLC positions and gantry angles were retrieved from the MLC log files and the data were used to calculate the delivered dose distributions in Pinnacle. The resulting dose distributions were then compared against the corresponding planned dose distributions using the 3D gamma index with 3 mm/3% passing criteria. The ScandiDos Delta4 phantom was also used to measure a 2D dose distribution for all the 15 patients and a 2D gamma was calculated for each patient using the Delta4 software. The average 3D gamma using the EPID images was 96.1% ± 2.2%. The average 3D gamma using the log files was 98.7% ± 0.5%. The average 2D gamma from the Delta4 was 98.1% ± 2.1%. Our results indicate that the use of the EPID, combined with MLC log files and a TPS, is a viable method for QA of VMAT plans. PMID:26103490

  8. Neutron dose equivalent measured at the maze door with various openings for the jaws and MLC

    SciTech Connect

    Krmar, M.; Baucal, M.; Bozic, N.; Jovancevic, N.; Ciraj-Bjelac, O.

    2012-03-15

    Purpose: This study was undertaken to explore the effects of the jaws and the MLC openings on the neutron dose equivalent (DE) at the maze door and neutron flux at the patient plane. Methods: The neutron dose equivalent was measured at the maze entrance door of a 15 MV therapy linear accelerator room. All measurements were performed using various field sizes up to 40 cm x 40 cm. Activation detectors constructed from natural Indium (In) were exposed at Cd envelope to neutrons in order to estimate relative changes of epithermal neutron fluences in the patient plane. Results: Our study showed that the dose equivalent at the maze door is at the highest when the jaw are closed and that maximal jaws opening reduces the DE by more than 20%. The neutron dose equivalent at the maze door measured for radiation fields defined by jaws do not differ significantly from the DE measured when MLC determines the same size radiation field. The epithermal capture reaction rate measured using different jaw openings differs by approximately 10%. When an MLC leaf is inserted into a fixed geometry for one opening of the jaws, an increase of the epithermal neutron capture reaction rate in Indium activation detectors was observed. Conclusions: There is no significant difference in the neutron DE when MLC defines radiation field instead of jaws. This leads to the conclusion that the overall number of neutrons remains similar and it does not depend on how primary photon beam was stopped--by the jaws or the MLC. An increase of the fast neutron capture reaction rate when MLC leaves are inserted probably originates from the neutron scattering.

  9. The sensitivity of patient specific IMRT QC to systematic MLC leaf bank offset errors

    SciTech Connect

    Rangel, Alejandra; Palte, Gesa; Dunscombe, Peter

    2010-07-15

    Purpose: Patient specific IMRT QC is performed routinely in many clinics as a safeguard against errors and inaccuracies which may be introduced during the complex planning, data transfer, and delivery phases of this type of treatment. The purpose of this work is to evaluate the feasibility of detecting systematic errors in MLC leaf bank position with patient specific checks. Methods: 9 head and neck (H and N) and 14 prostate IMRT beams were delivered using MLC files containing systematic offsets ({+-}1 mm in two banks, {+-}0.5 mm in two banks, and 1 mm in one bank of leaves). The beams were measured using both MAPCHECK (Sun Nuclear Corp., Melbourne, FL) and the aS1000 electronic portal imaging device (Varian Medical Systems, Palo Alto, CA). Comparisons with calculated fields, without offsets, were made using commonly adopted criteria including absolute dose (AD) difference, relative dose difference, distance to agreement (DTA), and the gamma index. Results: The criteria most sensitive to systematic leaf bank offsets were the 3% AD, 3 mm DTA for MAPCHECK and the gamma index with 2% AD and 2 mm DTA for the EPID. The criterion based on the relative dose measurements was the least sensitive to MLC offsets. More highly modulated fields, i.e., H and N, showed greater changes in the percentage of passing points due to systematic MLC inaccuracy than prostate fields. Conclusions: None of the techniques or criteria tested is sufficiently sensitive, with the population of IMRT fields, to detect a systematic MLC offset at a clinically significant level on an individual field. Patient specific QC cannot, therefore, substitute for routine QC of the MLC itself.

  10. Student exam analysis (debriefing) promotes positive changes in exam preparation and learning.

    PubMed

    Favero, Terence G; Hendricks, Nora

    2016-09-01

    Traditional exam review sessions, typically conducted orally and in class by the instructor, are intended to identify the most frequently missed or problematic question with the intent of helping students perform better on subsequent exams. The shortcoming of this instructor-led activity is that it tends to focus on issues with content or understanding rather than helping the individual student prevent or avoid similar mistakes on future exams. Here, we report that students who performed a more comprehensive out-of-class exam debrief after the first exam significantly improve their exam performance compared with students that did not conduct the exam debrief. We also identify the most common mistakes that students make on exams and the most frequent self-selected strategies to improve their learning. By having students focus on missed questions coupled with addressing deficiencies in their test preparation strategies and behaviors, they likely engage in more self-regulated learning to better prepare for exams and avoid repeating past mistakes. PMID:27445280

  11. Disrupting MLC1 and GlialCAM and ClC-2 interactions in leukodystrophy entails glial chloride channel dysfunction

    NASA Astrophysics Data System (ADS)

    Hoegg-Beiler, Maja B.; Sirisi, Sònia; Orozco, Ian J.; Ferrer, Isidre; Hohensee, Svea; Auberson, Muriel; Gödde, Kathrin; Vilches, Clara; de Heredia, Miguel López; Nunes, Virginia; Estévez, Raúl; Jentsch, Thomas J.

    2014-03-01

    Defects in the astrocytic membrane protein MLC1, the adhesion molecule GlialCAM or the chloride channel ClC-2 underlie human leukoencephalopathies. Whereas GlialCAM binds ClC-2 and MLC1, and modifies ClC-2 currents in vitro, no functional connections between MLC1 and ClC-2 are known. Here we investigate this by generating loss-of-function Glialcam and Mlc1 mouse models manifesting myelin vacuolization. We find that ClC-2 is unnecessary for MLC1 and GlialCAM localization in brain, whereas GlialCAM is important for targeting MLC1 and ClC-2 to specialized glial domains in vivo and for modifying ClC-2’s biophysical properties specifically in oligodendrocytes (OLs), the cells chiefly affected by vacuolization. Unexpectedly, MLC1 is crucial for proper localization of GlialCAM and ClC-2, and for changing ClC-2 currents. Our data unmask an unforeseen functional relationship between MLC1 and ClC-2 in vivo, which is probably mediated by GlialCAM, and suggest that ClC-2 participates in the pathogenesis of megalencephalic leukoencephalopathy with subcortical cysts.

  12. Evaluation of two methods of predicting MLC leaf positions using EPID measurements

    SciTech Connect

    Parent, Laure; Seco, Joao; Evans, Phil M.; Dance, David R.; Fielding, Andrew

    2006-09-15

    In intensity modulated radiation treatments (IMRT), the position of the field edges and the modulation within the beam are often achieved with a multileaf collimator (MLC). During the MLC calibration process, due to the finite accuracy of leaf position measurements, a systematic error may be introduced to leaf positions. Thereafter leaf positions of the MLC depend on the systematic error introduced on each leaf during MLC calibration and on the accuracy of the leaf position control system (random errors). This study presents and evaluates two methods to predict the systematic errors on the leaf positions introduced during the MLC calibration. The two presented methods are based on a series of electronic portal imaging device (EPID) measurements. A comparison with film measurements showed that the EPID could be used to measure leaf positions without introducing any bias. The first method, referred to as the 'central leaf method', is based on the method currently used at this center for MLC leaf calibration. It mimics the manner in which leaf calibration parameters are specified in the MLC control system and consequently is also used by other centers. The second method, a new method proposed by the authors and referred to as the ''individual leaf method,'' involves the measurement of two positions for each leaf (-5 and +15 cm) and the interpolation and extrapolation from these two points to any other given position. The central leaf method and the individual leaf method predicted leaf positions at prescribed positions of -11, 0, 5, and 10 cm within 2.3 and 1.0 mm, respectively, with a standard deviation (SD) of 0.3 and 0.2 mm, respectively. The individual leaf method provided a better prediction of the leaf positions than the central leaf method. Reproducibility tests for leaf positions of -5 and +15 cm were performed. The reproducibility was within 0.4 mm on the same day and 0.4 mm six weeks later (1 SD). Measurements at gantry angles of 0 deg., 90 deg., and 270 deg

  13. Profile of State High School Exit Exam Policies. South Carolina

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on South Carolina's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam…

  14. Profile of State High School Exit Exam Policies. Rhode Island

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Rhode Island's high school exit exam standards and policies. Some of the categories presented include: (1) State exit exam policy; (2) Type of Test; (3) Purpose; (4) Major changes in exit exam policy since the 2009-10 school year for financial reasons; (5) Subjects tested on exam; (6) Grade exam…

  15. Physics Exam Preparation: A Comparison of Three Methods

    ERIC Educational Resources Information Center

    Fakcharoenphol, Witat; Stelzer, Timothy

    2014-01-01

    In this clinical study on helping students prepare for an exam, we compared three different treatments. All students were asked to take a practice exam. One group was then given worked-out solutions for that exam, another group was given the solutions and targeted exercises to do as homework based on the result of their practice exam, and the…

  16. Oral Exams as a Tool for Teaching and Assessment

    ERIC Educational Resources Information Center

    Sayre, Eleanor C.

    2014-01-01

    Oral exams are a fruitful and practical alternative to written exams in small-enrolment Science classes. In an oral exam, the instructor can assess conceptual understanding, problem-solving, scientific communication skills, and a student's philosophy of science. In contrast, a written exam gives a much poorer picture of how students learn and…

  17. The Changing Roles of Statewide High School Exams

    ERIC Educational Resources Information Center

    Southern Regional Education Board (SREB), 2007

    2007-01-01

    SREB states were among the first in the nation to implement statewide high school exams. Today, these exams are a key component of each state's accountability system. This report identifies which states use comprehensive exams and which use end-of-course exams, how students perform on them, and whether achievement gaps have narrowed. It also…

  18. MLC901, a Traditional Chinese Medicine induces neuroprotective and neuroregenerative benefits after traumatic brain injury in rats.

    PubMed

    Quintard, H; Lorivel, T; Gandin, C; Lazdunski, M; Heurteaux, C

    2014-09-26

    Traumatic brain injury (TBI) is a frequent and clinically highly heterogeneous neurological disorder with large socioeconomic consequences. NeuroAid (MLC601 and MLC901), a Traditional Medicine used in China for patients after stroke has been previously reported to induce neuroprotection and neuroplasticity. This study was designed to evaluate the neuroprotective and neuroregenerative effects of MLC901 in a rat model of TBI. TBI was induced by a moderate lateral fluid percussion applied to the right parietal cortex. MLC901 was injected intraperitoneally at 2h post-TBI, and then administered in drinking water at a concentration of 10mg/ml until sacrifice of the animals. The cognitive deficits induced by TBI were followed by using the "what-where-when" task, which allows the measurement of episodic-like memory. MLC901 treatment decreased brain lesions induced by TBI. It prevented the serum increase of S-100 beta (S100B) and neuron-specific enolase (NSE), which may be markers to predict the neurologic outcome in human patients with TBI. MLC901 reduced the infarct volume when injected up to 2h post-TBI, prevented edema formation and assisted its resolution, probably via the regulation of aquaporin 4. These positive MLC901 effects were associated with an upregulation of vascular endothelial growth factor (VEGF) as well as an increase of endogenous hippocampal neurogenesis and gliogenesis around the lesion. Furthermore, MLC901 reduced cognitive deficits induced by TBI. Rats subjected to TBI displayed a suppression of temporal order memory, which was restored by MLC901. This work provides evidence that MLC901 has neuroprotective and neurorestorative actions, which lead to an improvement in the recovery of cognitive functions in a model of traumatic brain injury. PMID:24993477

  19. SU-C-BRB-02: Symmetric and Asymmetric MLC Based Lung Shielding and Dose Optimization During Translating Bed TBI

    SciTech Connect

    Ahmed, S; Kakakhel, MB; Ahmed, SBS; Hussain, A

    2015-06-15

    Purpose: The primary aim was to introduce a dose optimization method for translating bed total body irradiation technique that ensures lung shielding dynamically. Symmetric and asymmetric dynamic MLC apertures were employed for this purpose. Methods: The MLC aperture sizes were defined based on the radiological depth values along the divergent ray lines passing through the individual CT slices. Based on these RD values, asymmetrically shaped MLC apertures were defined every 9 mm of the phantom in superior-inferior direction. Individual MLC files were created with MATLAB™ and were imported into Eclipse™ treatment planning system for dose calculations. Lungs can be shielded to an optimum level by reducing the MLC aperture width over the lungs. The process was repeated with symmetrically shaped apertures. Results: Dose-volume histogram (DVH) analysis shows that the asymmetric MLC based technique provides better dose coverage to the body and optimum shielding of the lungs compared to symmetrically shaped beam apertures. Midline dose homogeneity is within ±3% with asymmetric MLC apertures whereas it remains within ±4.5% with symmetric ones (except head region where it drops down to −7%). The substantial over and under dosage of ±5% at tissue interfaces has been reduced to ±2% with asymmetric MLC technique. Lungs dose can be reduced to any desired limit. In this experiment lungs dose was reduced to 80% of the prescribed dose, as was desired. Conclusion: The novel asymmetric MLC based technique assures optimum shielding of OARs (e.g. lungs) and better 3-D dose homogeneity and body-dose coverage in comparison with the symmetric MLC aperture optimization. The authors acknowledge the financial and infrastructural support provided by Pakistan Institute of Engineering & Applied Sciences (PIEAS), Islamabad and Aga Khan University Hospital (AKUH), Karachi during the course of this research project. Authors have no conflict of interest with any national / international

  20. INSTA-EXAM: A Card-Based Exam Preparation System that Eliminates Repeated Typing and Proofreading.

    ERIC Educational Resources Information Center

    Tauber, Robert T.

    1984-01-01

    A system that rivals today's computer-based exam preparation systems is described. The INSTA-EXAM system is 10 times faster than the more traditional, labor-intensive method of typing directly on stencil masters. Its ability to quickly and efficiently change, update, and delete information makes it especially useful. (RM)

  1. Use of dMLC for implementation of dynamic respiratory-gated radiation therapy

    SciTech Connect

    Pepin, Eric W.; Wu, Huanmei; Shirato, Hiroki

    2013-10-15

    Purpose: To simulate and evaluate the use of dynamic multileaf collimators (dMLC) in respiratory gating to compensate for baseline drift.Methods: Tumor motion tracking data from 30 lung tumors over 322 treatment fractions was analyzed with the finite state model. A dynamic respiratory gating window was established in real-time by determining the average positions during the previous two end-of-expiration breathing phases and centering the dMLC aperture on a weighted average of these positions. A simulated dMLC with physical motion constraints was used in dynamic gating treatment simulations. Fluence maps were created to provide a statistical description of radiation delivery for each fraction. Duty cycle was also calculated for each fraction.Results: The average duty cycle was 2.3% greater under dynamic gating conditions. Dynamic gating also showed higher fluences and less tumor obstruction. Additionally, dynamic gating required fewer beam toggles and each delivery period was longer on average than with static gating.Conclusions: The use of dynamic gating showed better performance than static gating and the physical constraints of a dMLC were shown to not be an impediment to dynamic gating.

  2. Regulation of Yersinia enterocolitica mal genes by MalT and Mlc proteins.

    PubMed

    Raczkowska, Adrianna; Brzóstkowska, Marta; Brzostek, Katarzyna

    2008-01-01

    To show the role of MalT protein in the regulation of mal genes, encoding proteins involved in transport and metabolism of maltose/ maltodextrins in Yersinia enterocolitica, we constructed a malT mutant which was characterized by a strong reduction in maltose transport and a loss of MBP protein. We also studied the influence of MalT activity on the production of Yop proteins in Y. enterocolitica and found that the level of these virulence factors is not changed in the malT mutant. Subsequently, transcriptional fusion malT::lacZYA was applied to study the activity of malT promoter. Monitoring of beta-galactosidase activity suggests the influence of catabolic repression on malT transcription, sincethe activity of malT promoter was decreased twofold in the presence of glucose. Furthermore, Mlc protein was identified in Y. enterocolitica as a factor regulating the transcription of malT. We observed a two-fold increase in the level of malT transcription in the mlc mutant background. Moreover, overproduction of Mlc protein strongly inhibited the activity of malT promoter. Thus, the data presented in this study suggest that the level of mal gene expression in Y. enterocolitica may be regulated by two proteins: MalT, the activator of mal transcription and Mlc, the repressor of malT expression. PMID:18610652

  3. Analytic IMRT dose calculations utilizing Monte Carlo to predict MLC fluence modulation

    PubMed Central

    Mihaylov, I. B.; Lerma, F. A.; Wu, Y.; Siebers, J. V.

    2007-01-01

    A hybrid dose-computation method is designed which accurately accounts for multileaf collimator (MLC)-induced intensity modulation in intensity modulated radiation therapy (IMRT) dose calculations. The method employs Monte Carlo (MC) modeling to determine the fluence modulation caused by the delivery of dynamic or multisegmental (step-and-shoot) MLC fields, and a conventional dose-computation algorithm to estimate the delivered dose to a phantom or a patient. Thus, it determines the IMRT fluence prediction accuracy achievable by analytic methods in the limit that the analytic method includes all details of the MLC leaf transport and scatter. The hybrid method is validated and benchmarked by comparison with in-phantom film dose measurements, as well as dose calculations from two in-house, and two commercial treatment planning system analytic fluence estimation methods. All computation methods utilize the same dose algorithm to calculate dose to a phantom, varying only in the estimation of the MLC modulation of the incident photon energy fluence. Gamma analysis, with respect to measured two-dimensional (2D) dose planes, is used to benchmark each algorithm’s performance. The analyzed fields include static and dynamic test patterns, as well as fields from ten DMLC IMRT treatment plans (79 fields) and five SMLC treatment plans (29 fields). The test fields (fully closed MLC, picket fence, sliding windows of different size, and leaf-tip profiles) cover the extremes of MLC usage during IMRT, while the patient fields represent realistic clinical conditions. Of the methods tested, the hybrid method most accurately reproduces measurements. For the hybrid method, 79 of 79 DMLC field calculations have γ ≤1 (3% /3 mm) for more than 95% of the points (per field) while for SMLC fields, 27 of 29 pass the same criteria. The analytic energy fluence estimation methods show inferior pass rates, with 76 of 79 DMLC and 24 of 29 SMLC fields having more than 95% of the test points

  4. Impact of the MLC on the MRI field distortion of a prototype MRI-linac

    SciTech Connect

    Kolling, Stefan; Keall, Paul; Oborn, Brad

    2013-12-15

    Purpose: To cope with intrafraction tumor motion, integrated MRI-linac systems for real-time image guidance are currently under development. The multileaf collimator (MLC) is a key component in every state-of-the-art radiotherapy treatment system, allowing for accurate field shaping and tumor tracking. This work quantifies the magnetic impact of a widely used MLC on the MRI field homogeneity for such a modality.Methods: The finite element method was employed to model a MRI-linac assembly comprised of a 1.0 T split-bore MRI magnet and the key ferromagnetic components of a Varian Millennium 120 MLC, namely, the leaves and motors. Full 3D magnetic field maps of the system were generated. From these field maps, the peak-to-peak distortion within the MRI imaging volume was evaluated over a 30 cm diameter sphere volume (DSV) around the isocenter and compared to a maximum preshim inhomogeneity of 300 μT. Five parametric studies were performed: (1) The source-to-isocenter distance (SID) was varied from 100 to 200 cm, to span the range of a compact system to that with lower magnetic coupling. (2) The MLC model was changed from leaves only to leaves with motors, to determine the contribution to the total distortion caused by MLC leaves and motors separately. (3) The system was configured in the inline or perpendicular orientation, i.e., the linac treatment beam was oriented parallel or perpendicular to the magnetic field direction. (4) The treatment field size was varied from 0 × 0 to 20×20 cm{sup 2}, to span the range of clinical treatment fields. (5) The coil currents were scaled linearly to produce magnetic field strengths B{sub 0} of 0.5, 1.0, and 1.5 T, to estimate how the MLC impact changes with B{sub 0}.Results: (1) The MLC-induced MRI field distortion fell continuously with increasing SID. (2) MLC leaves and motors were found to contribute to the distortion in approximately equal measure. (3) Due to faster falloff of the fringe field, the field

  5. Real-time motion-adaptive delivery (MAD) using binary MLC: I. Static beam (topotherapy) delivery

    NASA Astrophysics Data System (ADS)

    Lu, Weiguo

    2008-11-01

    Intra-fraction target motion hits the fundamental basis of IMRT where precise target positions are assumed. Real-time motion compensation is necessary to ensure that the same dose is delivered as planned. Strategies for conventional IMRT delivery for moving targets by dynamic multi-leaf collimators (MLC) tracking are well published. Binary MLC-based IMRT, such as TomoTherapy®, requires synchronized motion of MLC, the couch and the gantry, which suggests a unique motion management strategy. Thanks to its ultra-fast leaf response and fast projection rate, real-time motion compensation for binary MLC-based IMRT is feasible. Topotherapy is a new IMRT delivery technique, which can be implemented in commercial helical TomoTherapy® machines using only fixed gantry positions. In this paper, we present a novel approach for TopoTherapy delivery that adjusts for moving targets without additional hardware and control requirement. This technique uses the planned leaf sequence but rearranges the projection and leaf indices. It does not involve time-consuming operations, such as reoptimization. Unlike gating or breath-hold-based methods, this technique can achieve nearly a 100% duty cycle with little breath control. Unlike dynamic MLC-based tracking methods, this technique requires neither the whole target motion trajectory nor the velocity of target motion. Instead, it only requires instantaneous target positions, which greatly simplifies the system implementation. Extensive simulations, including the worst-case scenarios, validated the presented technique to be applicable to relatively regular or mild irregular respirations. The delivered dose conforms well to the target, and significant margin reduction can be achieved provided that accurate, real-time tumor localization is available.

  6. The effect of MLC speed and acceleration on the plan delivery accuracy of VMAT

    PubMed Central

    Park, J M; Wu, H-G; Kim, J H; Carlson, J N K

    2015-01-01

    Objective: To determine a new metric utilizing multileaf collimator (MLC) speeds and accelerations to predict plan delivery accuracy of volumetric modulated arc therapy (VMAT). Methods: To verify VMAT delivery accuracy, gamma evaluations, analysis of mechanical parameter difference between plans and log files, and analysis of changes in dose–volumetric parameters between plans and plans reconstructed with log files were performed with 40 VMAT plans. The average proportion of leaf speeds ranging from l to h cm s−1 (Sl–h and l–h = 0–0.4, 0.4–0.8, 0.8–1.2, 1.2–1.6 and 1.6–2.0), mean and standard deviation of MLC speeds were calculated for each VMAT plan. The same was carried out for accelerations in centimetre per second squared (Al–h and l–h = 0–4, 4–8, 8–12, 12–16 and 16–20). The correlations of those indicators to plan delivery accuracy were analysed with Spearman's correlation coefficient (rs). Results: The S1.2–1.6 and mean acceleration of MLCs showed generally higher correlations to plan delivery accuracy than did others. The highest rs values were observed between S1.2–1.6 and global 1%/2 mm (rs = −0.698 with p < 0.001) as well as mean acceleration and global 1%/2 mm (rs = −0.650 with p < 0.001). As the proportion of MLC speeds and accelerations >0.4 and 4 cm s−2 increased, the plan delivery accuracy of VMAT decreased. Conclusion: The variations in MLC speeds and accelerations showed considerable correlations to VMAT delivery accuracy. Advances in knowledge: As the MLC speeds and accelerations increased, VMAT delivery accuracy reduced. PMID:25734490

  7. Quantifying the gantry sag on linear accelerators and introducing an MLC-based compensation strategy

    PubMed Central

    Du, Weiliang; Gao, Song; Wang, Xiaochun; Kudchadker, Rajat J.

    2012-01-01

    Purpose: Gantry sag is one of the well-known sources of mechanical imperfections that compromise the spatial accuracy of radiation dose delivery. The objectives of this study were to quantify the gantry sag on multiple linear accelerators (linacs), to investigate a multileaf collimator (MLC)-based strategy to compensate for gantry sag, and to verify the gantry sag and its compensation with film measurements. Methods: The authors used the Winston–Lutz method to measure gantry sag on three Varian linacs. A ball bearing phantom was imaged with megavolt radiation fields at 10° gantry angle intervals. The images recorded with an electronic portal imaging device were analyzed to derive the radiation isocenter and the gantry sag, that is, the superior–inferior wobble of the radiation field center, as a function of the gantry angle. The authors then attempted to compensate for the gantry sag by applying a gantry angle-specific correction to the MLC leaf positions. The gantry sag and its compensation were independently verified using film measurements. Results: Gantry sag was reproducible over a six-month measurement period. The maximum gantry sag was found to vary from 0.7 to 1.0 mm, depending on the linac and the collimator angle. The radiation field center moved inferiorly (i.e., away from the gantry) when the gantry was rotated from 0° to 180°. After the MLC leaf position compensation was applied at 90° collimator angle, the maximum gantry sag was reduced to <0.2 mm. The film measurements at gantry angles of 0° and 180° verified the inferior shift of the radiation fields and the effectiveness of MLC compensation. Conclusions: The results indicate that gantry sag on a linac can be quantitatively measured using a simple phantom and an electronic portal imaging device. Reduction of gantry sag is feasible by applying a gantry angle-specific correction to MLC leaf positions at 90° collimator angle. PMID:22482636

  8. Quantifying the gantry sag on linear accelerators and introducing an MLC-based compensation strategy

    SciTech Connect

    Du Weiliang; Gao Song; Wang Xiaochun; Kudchadker, Rajat J.

    2012-04-15

    Purpose: Gantry sag is one of the well-known sources of mechanical imperfections that compromise the spatial accuracy of radiation dose delivery. The objectives of this study were to quantify the gantry sag on multiple linear accelerators (linacs), to investigate a multileaf collimator (MLC)-based strategy to compensate for gantry sag, and to verify the gantry sag and its compensation with film measurements. Methods: The authors used the Winston-Lutz method to measure gantry sag on three Varian linacs. A ball bearing phantom was imaged with megavolt radiation fields at 10 deg. gantry angle intervals. The images recorded with an electronic portal imaging device were analyzed to derive the radiation isocenter and the gantry sag, that is, the superior-inferior wobble of the radiation field center, as a function of the gantry angle. The authors then attempted to compensate for the gantry sag by applying a gantry angle-specific correction to the MLC leaf positions. The gantry sag and its compensation were independently verified using film measurements. Results: Gantry sag was reproducible over a six-month measurement period. The maximum gantry sag was found to vary from 0.7 to 1.0 mm, depending on the linac and the collimator angle. The radiation field center moved inferiorly (i.e., away from the gantry) when the gantry was rotated from 0 deg. to 180 deg. After the MLC leaf position compensation was applied at 90 deg. collimator angle, the maximum gantry sag was reduced to <0.2 mm. The film measurements at gantry angles of 0 deg. and 180 deg. verified the inferior shift of the radiation fields and the effectiveness of MLC compensation. Conclusions: The results indicate that gantry sag on a linac can be quantitatively measured using a simple phantom and an electronic portal imaging device. Reduction of gantry sag is feasible by applying a gantry angle-specific correction to MLC leaf positions at 90 deg. collimator angle.

  9. Mouse and computational models link Mlc2v dephosphorylation to altered myosin kinetics in early cardiac disease

    PubMed Central

    Sheikh, Farah; Ouyang, Kunfu; Campbell, Stuart G.; Lyon, Robert C.; Chuang, Joyce; Fitzsimons, Dan; Tangney, Jared; Hidalgo, Carlos G.; Chung, Charles S.; Cheng, Hongqiang; Dalton, Nancy D.; Gu, Yusu; Kasahara, Hideko; Ghassemian, Majid; Omens, Jeffrey H.; Peterson, Kirk L.; Granzier, Henk L.; Moss, Richard L.; McCulloch, Andrew D.; Chen, Ju

    2012-01-01

    Actin-myosin interactions provide the driving force underlying each heartbeat. The current view is that actin-bound regulatory proteins play a dominant role in the activation of calcium-dependent cardiac muscle contraction. In contrast, the relevance and nature of regulation by myosin regulatory proteins (for example, myosin light chain-2 [MLC2]) in cardiac muscle remain poorly understood. By integrating gene-targeted mouse and computational models, we have identified an indispensable role for ventricular Mlc2 (Mlc2v) phosphorylation in regulating cardiac muscle contraction. Cardiac myosin cycling kinetics, which directly control actin-myosin interactions, were directly affected, but surprisingly, Mlc2v phosphorylation also fed back to cooperatively influence calcium-dependent activation of the thin filament. Loss of these mechanisms produced early defects in the rate of cardiac muscle twitch relaxation and ventricular torsion. Strikingly, these defects preceded the left ventricular dysfunction of heart disease and failure in a mouse model with nonphosphorylatable Mlc2v. Thus, there is a direct and early role for Mlc2 phosphorylation in regulating actin-myosin interactions in striated muscle contraction, and dephosphorylation of Mlc2 or loss of these mechanisms can play a critical role in heart failure. PMID:22426213

  10. Therapeutic efficacy of Neuro AiD™ (MLC 601), a traditional Chinese medicine, in experimental traumatic brain injury.

    PubMed

    Tsai, Ming-Che; Chang, Ching-Ping; Peng, Syue-Wei; Jhuang, Kai-Sheng; Fang, Yi-Hsien; Lin, Mao-Tsun; Tsao, Thomas Chang-Yao

    2015-03-01

    Traumatic brain injury (TBI) causes increased release of several mediators from injured and dead cells and elicits microglial activation. Activated microglia change their morphology, migrate to injury sites, and release tumor necrosis factor-alpha (TNF-α) and others. In this study we used a controlled fluid percussion injury model of TBI in the rat to determine whether early (4 h post-injury) or late (4 days post-injury) treatment with MLC 601, a Traditional Chinese Medicine, would affect microglial activation and improve recovery. MLC 601 was chosen for this study because its herbal component MLC 901 was beneficial in treating TBI in rats. Herein, rats with induced TBI were treated with MLC 601 (0.2-0.8 mg/kg) 1 h (early treatment) or 4 day post-injury (late treatment) and then injected once daily for consecutive 2 days. Acute neurological and motor deficits were assessed in all rats the day before and 4 days after early MLC 601 treatment. An immunofluorescence microscopy method was used to count the numbers of the cells colocalized with neuron- and apoptosis-specific markers, and the cells colocalized with microglia- and TNF-α-specific markers, in the contused brain regions 4 days post-injury. An immunohistochemistry method was used to evaluate both the number and the morphological transformation of microglia in the injured areas. It was found that early treatment with MLC 601 had better effects in reducing TBI-induced cerebral contusion than did the late therapy with MLC 601. Cerebral contusion caused by TBI was associated with neurological motor deficits, brain apoptosis, and activated microglia (e.g., microgliosis, amoeboid microglia, and microglial overexpression of TNF-α), which all were significantly attenuated by MLC 601 therapy. Our data suggest that MLC 601 is a promising agent for treatment of TBI in rats. PMID:25331680

  11. SU-E-T-33: An EPID-Based Method for Testing Absolute Leaf Position for MLC Without Backup Jaws

    SciTech Connect

    Hancock, S; Whitaker, M

    2014-06-01

    Purpose: Methods in common use for MLC leaf position QA are limited to measurements relative to an arbitrary reference position. The authors previously presented an EPID-based method for efficiently testing accuracy of leaf position relative to the mechanical isocenter for MLC with backup jaws. The purpose of this work is to extend that method to the general case of MLC without backup jaws. Methods: A pair of collimator walkout images is used to determine the location of the mechanical isocenter relative to the center of one field using a parameter called X-offset. The method allows for shift of the imager panel to cover subsets of MLC leaves within the limited field of view of the imager. For a shifted panel position, an image of three beam strips defined by a subset of MLC leaves allows determination of the position of each leaf relative to the isocenter. The location of the isocenter is determined by applying X-offset to an image of a single rectangular field obtained at that panel position. The method can also be used to test backup jaws instead of MLC leaves. A software tool was developed to efficiently analyze the images. Results: The software tool reports leaf position and deviation from nominal position, and provides visual displays to facilitate rapid qualitative interpretation. Test results using this method agree well with results using the previous method requiring backup jaws. Test results have been successfully used to recalibrate one model MLC (Elekta MLCi2™). Work in progress includes extension of the software tool to other MLC models, and quantification of reproducibility of the measurements. Conclusion: This work successfully demonstrates a method to efficiently and accurately measure MLC leaf position, or backup jaw position, relative to the mechanical isocenter of the collimator.

  12. Implementation of Hospital Examination Reservation System Using Data Mining Technique

    PubMed Central

    Cha, Hyo Soung; Yoon, Tae Sik; Ryu, Ki Chung; Shin, Il Won; Choe, Yang Hyo; Lee, Kyoung Yong; Lee, Jae Dong; Ryu, Keun Ho

    2015-01-01

    Objectives New methods for obtaining appropriate information for users have been attempted with the development of information technology and the Internet. Among such methods, the demand for systems and services that can improve patient satisfaction has increased in hospital care environments. Methods In this paper, we proposed the Hospital Exam Reservation System (HERS), which uses the data mining method. First, we focused on carrying clinical exam data and finding the optimal schedule for generating rules using the multi-examination pattern-mining algorithm. Then, HERS was applied by a rule master and recommending system with an exam log. Finally, HERS was designed as a user-friendly interface. Results HERS has been applied at the National Cancer Center in Korea since June 2014. As the number of scheduled exams increased, the time required to schedule more than a single condition decreased (from 398.67% to 168.67% and from 448.49% to 188.49%; p < 0.0001). As the number of tests increased, the difference between HERS and non-HERS increased (from 0.18 days to 0.81 days). Conclusions It was possible to expand the efficiency of HERS studies using mining technology in not only exam reservations, but also the medical environment. The proposed system based on doctor prescription removes exams that were not executed in order to improve recommendation accuracy. In addition, we expect HERS to become an effective system in various medical environments. PMID:25995961

  13. [Why are some high achievers on the course final exam unsuccessful on the proficiency exam in English?].

    PubMed

    Matsunuma, Mitsuyasu

    2009-04-01

    This study examined why some high achievers on the course final exam were unsuccessful on the proficiency exam in English. We hypothesized that the learning motives and learning behaviors (learning strategy, learning time) had different effects on the outcomes of the exams. First, the relation between the variables was investigated using structural equation modeling. Second, the learning behaviors of students who got good marks on both exams were compared with students who did well only on the course final exam. The results were as follows. (a) Learning motives influenced test performance via learning behaviors. (b) Content-attached motives influenced all variables concerning learning behaviors. (c) Content-detached motives influenced all variables concerning learning behaviors that were related only to the course final exam. (d) The students who got good marks on both exams performed the learning behaviors that were useful on the proficiency exam more frequently than the students who did well only on the course final exam. PMID:19489425

  14. Undergraduate range management exam: 1999-2014

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Undergraduate Range Management Exam (URME) has been administered to undergraduate students at the Annual Meeting of the Society for Range Management since 1983, with students demonstrating their higher order learning skills and synthesis knowledge of the art and science of rangeland management. ...

  15. Scholars Probe Diverse Effects of Exit Exams

    ERIC Educational Resources Information Center

    Viadero, Debra

    2009-01-01

    The author reports on a study released in April 2009 that suggests that California's high school exit exams are affecting some student demographic groups more than others. The California study, which was released by the Institute for Research on Education Policy and Practice at Stanford University, is the latest in a small spate of studies…

  16. Automatic Assessment of 3D Modeling Exams

    ERIC Educational Resources Information Center

    Sanna, A.; Lamberti, F.; Paravati, G.; Demartini, C.

    2012-01-01

    Computer-based assessment of exams provides teachers and students with two main benefits: fairness and effectiveness in the evaluation process. This paper proposes a fully automatic evaluation tool for the Graphic and Virtual Design (GVD) curriculum at the First School of Architecture of the Politecnico di Torino, Italy. In particular, the tool is…

  17. History of New York State Regents Exams

    ERIC Educational Resources Information Center

    Johnson, Carol Siri

    2009-01-01

    This paper is a brief history of the Regents subject-matter examinations and New York State's efforts to move towards educational equity. New York State was a leader in integrated curriculum and outcomes assessment in high schools for over a century. The first academic exit exam was administered in 1878 and it evolved into the controversial…

  18. Introducing Standardized EFL/ESL Exams

    ERIC Educational Resources Information Center

    Laborda, Jesus Garcia

    2007-01-01

    This article presents the features, and a brief comparison, of some of the most well-known high-stakes exams. They are classified in the following fashion: tests that only include multiple-choice questions, tests that include writing and multiple-choice questions, and tests that include speaking questions. The tests reviewed are: BULATS, IELTS,…

  19. Learning during a Collaborative Final Exam

    ERIC Educational Resources Information Center

    Dahlstrom, Orjan

    2012-01-01

    Collaborative testing has been suggested to serve as a good learning activity, for example, compared to individual testing. The aim of the present study was to measure learning at different levels of knowledge during a collaborative final exam in a course in basic methods and statistical procedures. Results on pre- and post-tests taken…

  20. English-Spanish Verbatim Translation Exam.

    ERIC Educational Resources Information Center

    Stansfield, Charles W.; And Others

    The development and validation of the English-Spanish Verbatim Translation Exam (ESVTE) is described. The test is for use by the Federal Bureau of Investigation (FBI) in the selection of applicants for the positions of Language Specialist or Contract Linguist. The report is divided into eight sections. Section 1 describes the need for the test,…

  1. Determinants of Student Attitudes toward Team Exams

    ERIC Educational Resources Information Center

    Reinig, Bruce A.; Horowitz, Ira; Whittenburg, Gene

    2014-01-01

    We examine how student attitudes toward their group, learning method, and perceived development of professional skills are initially shaped and subsequently evolve through multiple uses of team exams. Using a Tobit regression model to analyse a sequence of 10 team quizzes given in a graduate-level tax accounting course, we show that there is an…

  2. New Exams for New Professional Styles

    ERIC Educational Resources Information Center

    Chaptal, Alain; Pouzard, Guy

    2004-01-01

    Recruiting professionals for schools' media resources centres needs to take into account the new dimensions of the information society. This article describes the radical reform of the very high-stakes and competitive national selection of those professionals in France. The new exam is now driven by a problem-solving approach and based on an…

  3. High School Exit Exams and Hispanics

    ERIC Educational Resources Information Center

    Adam, Michelle

    2005-01-01

    This article deals with the report, entitled "State High School Exit Exams: A Maturing Reform", that addressed the achievement gaps that exist for minority and English language learner (ELL) populations. In this article, the author shows how Hispanics and ELLs lag behind Caucasians in terms of passing percentage in different subject areas. The…

  4. Quality assurance of MLC leaf position accuracy and relative dose effect at the MLC abutment region using an electronic portal imaging device

    PubMed Central

    Sumida, Iori; Yamaguchi, Hajime; Kizaki, Hisao; Koizumi, Masahiko; Ogata, Toshiyuki; Takahashi, Yutaka; Yoshioka, Yasuo

    2012-01-01

    We investigated an electronic portal image device (EPID)-based method to see whether it provides effective and accurate relative dose measurement at abutment leaves in terms of positional errors of the multi-leaf collimator (MLC) leaf position. A Siemens ONCOR machine was used. For the garden fence test, a rectangular field (0.2 × 20 cm) was sequentially irradiated 11 times at 2-cm intervals. Deviations from planned leaf positions were calculated. For the nongap test, relative doses at the MLC abutment region were evaluated by sequential irradiation of a rectangular field (2 × 20 cm) 10 times with a MLC separation of 2 cm without a leaf gap. The integral signal in a region of interest was set to position A (between leaves) and B (neighbor of A). A pixel value at position B was used as background and the pixel ratio (A/B × 100) was calculated. Both tests were performed at four gantry angles (0, 90, 180 and 270°) four times over 1 month. For the nongap test the difference in pixel ratio between the first and last period was calculated. Regarding results, average deviations from planned positions with the garden fence test were within 0.5 mm at all gantry angles, and at gantry angles of 90 and 270° tended to decrease gradually over the month. For the nongap test, pixel ratio tended to increase gradually in all leaves, leading to a decrease in relative doses at abutment regions. This phenomenon was affected by both gravity arising from the gantry angle, and the hardware-associated contraction of field size with this type of machine. PMID:22843372

  5. Brushed permanent magnet DC MLC motor operation in an external magnetic field

    SciTech Connect

    Yun, J.; St Aubin, J.; Rathee, S.; Fallone, B. G.

    2010-05-15

    Purpose: Linac-MR systems for real-time image-guided radiotherapy will utilize the multileaf collimators (MLCs) to perform conformal radiotherapy and tumor tracking. The MLCs would be exposed to the external fringe magnetic fields of the linac-MR hybrid systems. Therefore, an experimental investigation of the effect of an external magnetic field on the brushed permanent magnet DC motors used in some MLC systems was performed. Methods: The changes in motor speed and current were measured for varying external magnetic field strengths up to 2000 G generated by an EEV electromagnet. These changes in motor characteristics were measured for three orientations of the motor in the external magnetic field, mimicking changes in motor orientations due to installation and/or collimator rotations. In addition, the functionality of the associated magnetic motor encoder was tested. The tested motors are used with the Varian 120 leaf Millennium MLC (Maxon Motor half leaf and full leaf motors) and the Varian 52 leaf MKII MLC (MicroMo Electronics leaf motor) including a carriage motor (MicroMo Electronics). Results: In most cases, the magnetic encoder of the motors failed prior to any damage to the gearbox or the permanent magnet motor itself. This sets an upper limit of the external magnetic field strength on the motor function. The measured limits of the external magnetic fields were found to vary by the motor type. The leaf motor used with a Varian 52 leaf MKII MLC system tolerated up to 450{+-}10 G. The carriage motor tolerated up to 2000{+-}10 G field. The motors used with the Varian 120 leaf Millennium MLC system were found to tolerate a maximum of 600{+-}10 G. Conclusions: The current Varian MLC system motors can be used for real-time image-guided radiotherapy coupled to a linac-MR system, provided the fringe magnetic fields at their locations are below the determined tolerance levels. With the fringe magnetic fields of linac-MR systems expected to be larger than the

  6. EPID-based verification of the MLC performance for dynamic IMRT and VMAT

    SciTech Connect

    Rowshanfarzad, Pejman; Sabet, Mahsheed; Barnes, Michael P.; O'Connor, Daryl J.; Greer, Peter B.

    2012-10-15

    Purpose: In advanced radiotherapy treatments such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), verification of the performance of the multileaf collimator (MLC) is an essential part of the linac QA program. The purpose of this study is to use the existing measurement methods for geometric QA of the MLCs and extend them to more comprehensive evaluation techniques, and to develop dedicated robust algorithms to quantitatively investigate the MLC performance in a fast, accurate, and efficient manner. Methods: The behavior of leaves was investigated in the step-and-shoot mode by the analysis of integrated electronic portal imaging device (EPID) images acquired during picket fence tests at fixed gantry angles and arc delivery. The MLC was also studied in dynamic mode by the analysis of cine EPID images of a sliding gap pattern delivered in a variety of conditions including different leaf speeds, deliveries at fixed gantry angles or in arc mode, and changing the direction of leaf motion. The accuracy of the method was tested by detection of the intentionally inserted errors in the delivery patterns. Results: The algorithm developed for the picket fence analysis was able to find each individual leaf position, gap width, and leaf bank skewness in addition to the deviations from expected leaf positions with respect to the beam central axis with sub-pixel accuracy. For the three tested linacs over a period of 5 months, the maximum change in the gap width was 0.5 mm, the maximum deviation from the expected leaf positions was 0.1 mm and the MLC skewness was up to 0.2 Degree-Sign . The algorithm developed for the sliding gap analysis could determine the velocity and acceleration/deceleration of each individual leaf as well as the gap width. There was a slight decrease in the accuracy of leaf performance with increasing leaf speeds. The analysis results were presented through several graphs. The accuracy of the method was assessed

  7. SU-E-T-01: 2-D Characterization of DLG Among All MLC Leaf Pairs

    SciTech Connect

    Kumaraswamy, L; Xu, Z; Podgorsak, M; Schmitt, J; Bailey, D

    2014-06-01

    Purpose: The aim of this study is to evaluate the variation of dosimetric leaf-gap (DLG) along the travel path of each MLC leaf pair. This study evaluates whether the spatial variations in DLG could cause dose differences between TPS-calculated and measured dose. Methods: The 6MV DLG values were measured for all leaf pairs in the direction of leaf motion using a 2-D diode array and 0.6cc ion chamber. These measurements were performed on two Varian Linacs, employing the Millennium 120-leaf MLC and a 2-D-DLG variation map was created via in-house software. Several test plans were created with sweeping MLC fields using constant gaps from 2mm to 10mm and corrected for 2-D variation utilizing in-house software. Measurements were performed utilizing the MapCHECK at 5.0cm depth for plans with and without the 2-D DLG correction and compared to the TPS calculated dose via gamma analysis (3%/3mm). Results: The measured DLGs for the middle 40 MLC leaf pairs (0.5cm width) were very similar along the central superior-inferior axis, with maximum variation of 0.2mm. The outer 20 MLC leaf pairs (1.0cm width) have DLG values from 0.32mm (mean) to 0.65mm (maximum) lower than the central leaf-pair, depending on off-axis distance. Gamma pass rates for the 2mm, 4mm, and 6mm sweep plans increased by 23.2%, 28.7%, and 26.0% respectively using the 2-D-DLG correction. The most improved dose points occur in areas modulated by the 1.0cm leaf-pairs. The gamma pass rate for the 10mm sweep plan increased by only 7.7%, indicating that the 2D variation becomes less significant for dynamic plans with larger MLC gaps. Conclusion: Fluences residing significantly off-axis with narrow sweeping gaps may exhibit significant variations from planned dose due to large differences between the true DLG exhibited by the 1.0cm leaf-pairs versus the constant DLG value utilized by the TPS for dose calculation.

  8. Monte Carlo based beam model using a photon MLC for modulated electron radiotherapy

    SciTech Connect

    Henzen, D. Manser, P.; Frei, D.; Volken, W.; Born, E. J.; Vetterli, D.; Chatelain, C.; Fix, M. K.; Neuenschwander, H.; Stampanoni, M. F. M.

    2014-02-15

    Purpose: Modulated electron radiotherapy (MERT) promises sparing of organs at risk for certain tumor sites. Any implementation of MERT treatment planning requires an accurate beam model. The aim of this work is the development of a beam model which reconstructs electron fields shaped using the Millennium photon multileaf collimator (MLC) (Varian Medical Systems, Inc., Palo Alto, CA) for a Varian linear accelerator (linac). Methods: This beam model is divided into an analytical part (two photon and two electron sources) and a Monte Carlo (MC) transport through the MLC. For dose calculation purposes the beam model has been coupled with a macro MC dose calculation algorithm. The commissioning process requires a set of measurements and precalculated MC input. The beam model has been commissioned at a source to surface distance of 70 cm for a Clinac 23EX (Varian Medical Systems, Inc., Palo Alto, CA) and a TrueBeam linac (Varian Medical Systems, Inc., Palo Alto, CA). For validation purposes, measured and calculated depth dose curves and dose profiles are compared for four different MLC shaped electron fields and all available energies. Furthermore, a measured two-dimensional dose distribution for patched segments consisting of three 18 MeV segments, three 12 MeV segments, and a 9 MeV segment is compared with corresponding dose calculations. Finally, measured and calculated two-dimensional dose distributions are compared for a circular segment encompassed with a C-shaped segment. Results: For 15 × 34, 5 × 5, and 2 × 2 cm{sup 2} fields differences between water phantom measurements and calculations using the beam model coupled with the macro MC dose calculation algorithm are generally within 2% of the maximal dose value or 2 mm distance to agreement (DTA) for all electron beam energies. For a more complex MLC pattern, differences between measurements and calculations are generally within 3% of the maximal dose value or 3 mm DTA for all electron beam energies. For the

  9. EXPOSURE ANALYSIS MODELING SYSTEM: REFERENCE MANUAL FOR EXAMS 2

    EPA Science Inventory

    The Exposure Analysis Modeling System (EXAMS), published in 1982 (EPA-600/3-82-023), provides rapid evaluations of the behavior of synthetic organic chemicals in aquatic ecosystems. EXAMS combines laboratory data describing reactivity and thermodynamic properties of chemicals wit...

  10. A method for testing the performance and the accuracy of the binary MLC used in helical tomotherapy.

    PubMed

    Lissner, Steffen; Schubert, Kai; Klüter, Sebastian; Oetzel, Dieter; Debus, Jürgen

    2013-05-01

    During a helical tomotherapy a binary MLC is used for fluence modulation. The 64 pneumatically driven leaves of the MLC are either completely open or closed. The fast and frequent leaf movements result in a high demand of accuracy and stability of the MLC. This article is based on the analytical investigation of the accuracy and the stability of the MLC. Different patterns of MLC movements were generated to investigate the characteristics of the MLC. One of the considered aspects contains the friction between the leaves. The influence of variations of the compressed air on the MLC was also explored. The integrated MVCT detector of the tomotherapy system deposits the treatment data in a matrix. The detector is triggered with the linear accelerator, which is pulsed by 300Hz. The data matrix is available after the treatment. An IDL (Interactive Data Language) routine was programmed in order to analyse the matrix. The points of time, at which the leaves open (POT), and the period, in which the leaves stay open (LOT), were measured and compared with the desired values. That procedure has been repeated several times a week for approximately 6 months to investigate the stability of the MLC. Relative deviations of the LOT from -0.4% to -5.4% were measured. The friction between the leaves had no significant influence on the LOT. The available compressed air, that is used to move the leaves, depends on the number of moving leaves and also on the previous movements of the MLC. Variations of the compressed air resulted in deviations of the LOT from -1.8% to -3.7%. The measured POT deviates from the programmed POT up to -18.4ms±0.7ms. This maximal deviation correlates with a shift of the gantry angle of 0.52̊ which is negligible. The MLC has shown a stable behaviour over the 6 months. A separate consideration of the leaves showed no higher standard deviation of the LOT than ±0.7ms during the investigated time. The variation between the different leaves is much higher than

  11. Motion management during IMAT treatment of mobile lung tumors—A comparison of MLC tracking and gated delivery

    PubMed Central

    Falk, Marianne; Pommer, Tobias; Keall, Paul; Korreman, Stine; Persson, Gitte; Poulsen, Per; Munck af Rosenschöld, Per

    2014-01-01

    Purpose: To compare real-time dynamic multileaf collimator (MLC) tracking, respiratory amplitude and phase gating, and no compensation for intrafraction motion management during intensity modulated arc therapy (IMAT). Methods: Motion management with MLC tracking and gating was evaluated for four lung cancer patients. The IMAT plans were delivered to a dosimetric phantom mounted onto a 3D motion phantom performing patient-specific lung tumor motion. The MLC tracking system was guided by an optical system that used stereoscopic infrared (IR) cameras and five spherical reflecting markers attached to the dosimetric phantom. The gated delivery used a duty cycle of 35% and collected position data using an IR camera and two reflecting markers attached to a marker block. Results: The average gamma index failure rate (2% and 2 mm criteria) was <0.01% with amplitude gating for all patients, and <0.1% with phase gating and <3.7% with MLC tracking for three of the four patients. One of the patients had an average failure rate of 15.1% with phase gating and 18.3% with MLC tracking. With no motion compensation, the average gamma index failure rate ranged from 7.1% to 46.9% for the different patients. Evaluation of the dosimetric error contributions showed that the gated delivery mainly had errors in target localization, while MLC tracking also had contributions from MLC leaf fitting and leaf adjustment. The average treatment time was about three times longer with gating compared to delivery with MLC tracking (that did not prolong the treatment time) or no motion compensation. For two of the patients, the different motion compensation techniques allowed for approximately the same margin reduction but for two of the patients, gating enabled a larger reduction of the margins than MLC tracking. Conclusions: Both gating and MLC tracking reduced the effects of the target movements, although the gated delivery showed a better dosimetric accuracy and enabled a larger reduction of the

  12. SU-E-T-430: Modeling MLC Leaf End in 2D for Sliding Window IMRT and Arc Therapy

    SciTech Connect

    Liang, X; Zhu, T

    2014-06-01

    Purpose: To develop a 2D geometric model for MLC accounting for leaf end dose leakage for dynamic IMRT and Rapidarc therapy. Methods: Leaf-end dose leakage is one of the problems for MLC dose calculation and modeling. Dosimetric leaf gap used to model the MLC and to count for leakage in dose calculation, but may not be accurate for smaller leaf gaps. We propose another geometric modeling method to compensate for the MLC round-shape leaf ends dose leakage, and improve the accuracy of dose calculation and dose verification. A triangular function is used to geometrically model the MLC leaf end leakage in the leaf motion direction, and a step function is used in the perpendicular direction. Dose measurements with different leaf gap, different window width, and different window height were conducted, and the results were used to fit the analytical model to get the model parameters. Results: Analytical models have been obtained for stop-and-shoot and dynamic modes for MLC motion. Parameters a=0.4, lw'=5.0 mm for 6X and a=0.54, lw'=4.1 mm for 15x were obtained from the fitting process. The proposed MLC leaf end model improves the dose profile at the two ends of the sliding window opening. This improvement is especially significant for smaller sliding window openings, which are commonly used for highly modulated IMRT plans and arc therapy plans. Conclusion: This work models the MLC round leaf end shape and movement pattern for IMRT dose calculation. The theory, as well as the results in this work provides a useful tool for photon beam IMRT dose calculation and verification.

  13. Exhausting treadmill running causes dephosphorylation of sMLC2 and reduced level of myofilament MLCK2 in slow twitch rat soleus muscle

    PubMed Central

    Hortemo, Kristin Halvorsen; Aronsen, Jan Magnus; Lunde, Ida G; Sjaastad, Ivar; Lunde, Per Kristian; Sejersted, Ole M

    2015-01-01

    Myosin light chain 2 (MLC2) is a small protein in the myosin complex, regulating muscle contractile function by modulating Ca2+ sensitivity of myofilaments. MLC2 can be modified by phosphorylation and O-GlcNAcylation, two reversible and dynamic posttranslational modifications. The slow isoform of MLC2 (sMLC2) is dephosphorylated in soleus muscle during in situ loaded shortening contractions, which correlates with reduction in shortening capacity. Here, we hypothesize that exhausting in vivo treadmill running induces dephosphorylation of MLC2 in slow twitch soleus, but not in fast twitch EDL muscle, and that there are reciprocal changes in MLC2 O-GlcNAcylation. At rest, both phosphorylation and O-GlcNAcylation of MLC2 were lower in slow than fast twitch muscles. One bout of exhausting treadmill running induced dephosphorylation of sMLC2 in soleus, paralleled by reduced levels of the kinase MLCK2 associated to myofilaments, suggesting that the acute reduction in phosphorylation is mediated by dissociation of MLCK2 from myofilaments. O-GlcNAcylation of MLC2 did not change significantly, and seems of limited importance in the regulation of MLC2 phosphorylation during in vivo running. After 6 weeks of treadmill running, the dephosphorylation of sMLC2 persisted in soleus along with reduction in MLCK2 both in myofilament- and total protein fraction. In EDL on the contrary, phosphorylation of MLC2 was not altered after one exercise bout or after 6 weeks of treadmill running. Thus, in contrast to fast twitch muscle, MLC2 dephosphorylation occurs in slow twitch muscle during in vivo exercise and may be linked to reduced myofilament-associated MLCK2 and reduced shortening capacity. PMID:25713325

  14. Enhanced Security for Online Exams Using Group Cryptography

    ERIC Educational Resources Information Center

    Jung, I. Y.; Yeom, H. Y.

    2009-01-01

    While development of the Internet has contributed to the spread of online education, online exams have not been widely adopted. An online exam is defined here as one that takes place over the insecure Internet, and where no proctor is in the same location as the examinees. This paper proposes an enhanced secure online exam management environment…

  15. Exit Exams: Decreases or Increases the Dropout Rate

    ERIC Educational Resources Information Center

    Barnes, Teresa A.

    2009-01-01

    The purpose of this paper was to examine the impact of exit exams on the dropout rate. Data was gathered from several research articles. The most impressionable research revealed exit exams have a negative effect on minorities, especially black males. Results indicate by 2012, that exit exams in 25 states will affect 81 percent of minority high…

  16. The Effect of Announced Quizzes on Exam Performance: II

    ERIC Educational Resources Information Center

    Azorlosa, Julian L.

    2011-01-01

    I administered announced, multiple-choice quizzes to 1 of 2 sections of a Psychology of Learning class in each of 2 consecutive fall semesters. The quizzes were administered between the first and second exams which were also multiple-choice. Quizzes were discontinued after the second exam. After the second exam, students completed a questionnaire…

  17. Comparing the Lexical Difficulty of French Reading Comprehension Exam Texts

    ERIC Educational Resources Information Center

    Milton, James

    2004-01-01

    There is an acknowledged difficulty in demonstrating that the standard of school exams remains constant over the years. It is a source of debate every summer when exam results come out. There is some evidence that foreign language exams, and French in particular, have declined in standard since the 1980s, but empirical measures to demonstrate this…

  18. Evaluating Multiple-Choice Exams in Large Introductory Physics Courses

    ERIC Educational Resources Information Center

    Scott, Michael; Stelzer, Tim; Gladding, Gary

    2006-01-01

    The reliability and validity of professionally written multiple-choice exams have been extensively studied for exams such as the SAT, graduate record examination, and the force concept inventory. Much of the success of these multiple-choice exams is attributed to the careful construction of each question, as well as each response. In this study,…

  19. The Cognitive Abilities of Children: Reflections from an Entrance Exam

    ERIC Educational Resources Information Center

    Cil, Emine; Cepni, Salih

    2012-01-01

    The basic determiner for the school in which the children who completed their primary education will in at an upper education level in Turkey is the entrance exam carried out nationwide. The items of national exam, called as LDE (Level Determination Exam) which the primary education pupils (aged between 12 and 15) will participate in Turkey were…

  20. Profile of State College Entrance Exam Policies. Alabama

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Alabama's college entrance exam standards and polices. Some of the categories presented include: (1) College entrance exam policy; (2) Purpose; (3) Major changes in college entrance exam policy since the 2009-10 school year for financial reasons; (4) Preparation state offers to students taking…

  1. Profile of State College Entrance Exam Policies. North Dakota

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on North Dakota's college entrance exam standards and polices. Some of the categories presented include: (1) College entrance exam policy; (2) Purpose; (3) Major changes in college entrance exam policy since the 2009-10 school year for financial reasons; (4) Preparation state offers to students taking…

  2. Profile of State College Entrance Exam Policies. Idaho

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Idaho's college entrance exam standards and polices. Some of the categories presented include: (1) College entrance exam policy; (2) Purpose; (3) Major changes in college entrance exam policy since the 2009-10 school year for financial reasons; (4) Preparation state offers to students taking college…

  3. Profile of State College Entrance Exam Policies. Delaware

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Delaware's college entrance exam standards and polices. Some of the categories presented include: (1) College entrance exam policy; (2) Purpose; (3) Major changes in college entrance exam policy since the 2009-10 school year for financial reasons; (4) Preparation state offers to students taking…

  4. Profile of State College Entrance Exam Policies. Tennessee

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Tennessee's college entrance exam standards and polices. Some of the categories presented include: (1) College entrance exam policy; (2) Purpose; (3) Major changes in college entrance exam policy since the 2009-10 school year for financial reasons; (4) Preparation state offers to students taking…

  5. Profile of State College Entrance Exam Policies. Kentucky

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Kentucky's college entrance exam standards and polices. Some of the categories presented include: (1) College entrance exam policy; (2) Purpose; (3) Major changes in college entrance exam policy since the 2009-10 school year for financial reasons; (4) Preparation state offers to students taking…

  6. Profile of State College Entrance Exam Policies. Maine

    ERIC Educational Resources Information Center

    Center on Education Policy, 2011

    2011-01-01

    This individual profile provides information on Maine's college entrance exam standards and polices. Some of the categories presented include: (1) College entrance exam policy; (2) Purpose; (3) Major changes in college entrance exam policy since the 2009-10 school year for financial reasons; (4) Preparation state offers to students taking college…

  7. A Legal Overview and History of High School Exit Exams

    ERIC Educational Resources Information Center

    Sutton, Lenford

    2006-01-01

    State exit exams, also known as graduation tests, are tests that student must pass to graduate from high school. These tests are more influential than ever. Accordingly, in 2004, 20 states required students to pass an exit exam to graduate from high school, and six additional states will implement an exit exam by 2009. This affects more than half…

  8. The Effect of Announced Quizzes on Exam Performance: Quiz Content

    ERIC Educational Resources Information Center

    Azorlosa, Julian L.

    2012-01-01

    I administered quizzes to two sections of a course named "The Psychology of Learning." There were three multiple choice exams during the semester. Quizzes were given between exam 1 and exam 2. For one section, (lecture) quizzes occurred after the material had been covered in lecture. For the other section, quizzes were based on material not yet…

  9. On the suitability of Elekta’s Agility 160 MLC for tracked radiation delivery: closed-loop machine performance

    NASA Astrophysics Data System (ADS)

    Glitzner, M.; Crijns, S. P. M.; de Senneville, B. Denis; Lagendijk, J. J. W.; Raaymakers, B. W.

    2015-03-01

    For motion adaptive radiotherapy, dynamic multileaf collimator tracking can be employed to reduce treatment margins by steering the beam according to the organ motion. The Elekta Agility 160 MLC has hitherto not been evaluated for its tracking suitability. Both dosimetric performance and latency are key figures and need to be assessed generically, independent of the used motion sensor. In this paper, we propose the use of harmonic functions directly fed to the MLC to determine its latency during continuous motion. Furthermore, a control variable is extracted from a camera system and fed to the MLC. Using this setup, film dosimetry and subsequent γ statistics are performed, evaluating the response when tracking (MRI)-based physiologic motion in a closed-loop. The delay attributed to the MLC itself was shown to be a minor contributor to the overall feedback chain as compared to the impact of imaging components such as MRI sequences. Delay showed a linear phase behaviour of the MLC employed in continuously dynamic applications, which enables a general MLC-characterization. Using the exemplary feedback chain, dosimetry showed a vast increase in pass rate employing γ statistics. In this early stage, the tracking performance of the Agility using the test bench yielded promising results, making the technique eligible for translation to tracking using clinical imaging modalities.

  10. SU-E-T-471: Small Field Jaw/MLC Reference Data

    SciTech Connect

    Kerns, J; Alvarez, P; Followill, D; Lowenstein, J; Molineu, A; Summers, P; Kry, S

    2014-06-01

    Purpose: In recent years the need for small field data of MLCs has increased due to the use of intensity-modulated radiation (IMRT), but moreover the use of stereotactic body radiation (SBRT) has increased, which uses not simply small field sizes, but small jaw and field sizes together. Having reference data for these small fields that is reliable would be invaluable to the physics community. Our study has gathered these values and the data distributions from the Radiological Physics Center's (RPC) site visits between 1990 and the present. Methods: For all measurements, the RPC used a 25 × 25 × 25cm water phantom placed at 100cm SSD. All measurements were made with an Exradin A16 cylindrical ion chamber at an effective depth of 10 cm. A total of 42 Varian machine measurements were used to compose the data for a 6 MV beam and 5 TrueBeam 6 MV flattening filter free (FFF) beams were used for FFF data. Results: Jaw/MLC fields were measured for both 6 MV and 6 MF FFF beams with the jaws and MLCs both at the following field sizes: 6×6, 4×4, 3×3, and 2×2cm. Measurements were normalized to the 10×10 field readings (defined by the jaws and MLC). Spread in the data was minimal and demonstrates a high level of accuracy of acquired data. Conclusion: Small field Jaw/MLC reference data for Varian 6MV and 6 MV FFF beams has been analyzed and presented here, composed of the aggregation of numerous RPC site visits. Obtaining reliable small field data remains difficult, however the RPC has collected high fidelity small field Jaw/MLC data. The data are presented as a reference along with their distributions, in such a way that the physicist can act based upon their own desired agreement with the reference data.

  11. Word line program disturbance based data retention error recovery strategy for MLC NAND Flash

    NASA Astrophysics Data System (ADS)

    Ma, Haozhi; Pan, Liyang; Song, Changlai; Gao, Zhongyi; Wu, Dong; Xu, Jun

    2015-07-01

    NAND Flash has been widely used as storage solutions for portable system due to improvement on data throughput, power consumption and mechanical reliability. However, NAND Flash presents inevitable decline in reliability due to scaling down and multi-level cell (MLC) technology. High data retention error rate in highly stressed blocks causes a trend of stronger ECC deployed in system, with higher hardware overhead and spare bits cost. In this paper, a word line program disturbance (WPD) based data retention error recovery strategy, which induces extra electron injection to compensate floating gate electron leakage during long retention time, is proposed to reduce the data retention error rate and improve the retention reliability of highly scaled MLC NAND Flash memories. The proposed strategy is applied on 2×-nm MLC NAND Flash and the device one-year retention error rate after 3 K, 4 K, 5 K and 6 K P/E cycled decreases by 75.7%, 79.3%, 82.3% and 83.3%, respectively.

  12. New technologies to manage exam anxiety.

    PubMed

    Grassi, Alessandra; Gaggioli, Andrea; Riva, Giuseppe

    2011-01-01

    A Stress Inoculation Training-based protocol tested if multimedia audio-video content induced emotional changes and reduced exam anxiety in university students. Seventy-five participants took part in six experimental sessions consisting of viewing multimedia content and performing relaxation exercises. Participants were randomly assigned to five experimental groups: 1) audio and video narrative on mobile phone (UMTS); 2) audio and video narrative on DVD (DVD), 3) audio narrative on MP3 player (M3), 4) audio narrative on CD (CD), 5) control group (CTRL). Results showed that audio/video content induced a significant reduction in exam anxiety and an increase of relaxation in students, compared to the audio-only contents. PMID:21685642

  13. Delaying pelvic exams to encourage contraceptive use.

    PubMed

    Donovan, P

    1992-01-01

    The Family Planning Council of Southeastern Pennsylvania created a project called Start Smart, permitting some new adolescent clients to delay blood tests and pelvic exams up to 6 months after their oral contraceptive prescription. The rationale for the trial is the perception that fear of the pelvic exam is one of the reasons why teen women delay coming to medical care for contraception for 1 year on average after becoming sexually active. 5 clinics participated in the pilot trial from November 1988 to March 1990, giving anticipatory counseling and follow-up telephone calls to all young women in the program, and permitting postponement of the medical work-up to certain teens in 3 of the clinics. Special waivers from the Department of Health and Human Services were needed to permit the exception under Title K. These women had a comprehensive family, social, and medical history, weight, height, blood pressure, urinalysis, and pregnancy test. 627 teens aged 11-17 participated in the pilot trail; 90% were already sexually active; 33% had been so for 1 year; 25% had never used contraception. 25% decided to delay pelvic exams and 40% elected to delay blood tests. Most accepted pelvic exams on their 2nd visit. Those who delayed attended the clinic slightly more often than did others. Although there were no significant results, there were also no adverse medical consequences, such as missed sexually transmitted disease infections. The staff participating in this trial thought the teens had an added sense of control over their medical care. PMID:1628718

  14. Direct and Indirect Effects of Completion versus Accuracy Contingencies on Practice-Exam and Actual-Exam Performance

    ERIC Educational Resources Information Center

    Oliver, Renee; Williams, Robert L.

    2005-01-01

    Students in four sections of an undergraduate educational course (two large and two small sections) took out-of-class practice exams prior to actual exams for each of five course units. Each course unit consisted of five class sessions focusing on a specific developmental theme. Some sections received practice-exam credit based on the number of…

  15. Physics exam preparation: A comparison of three methods

    NASA Astrophysics Data System (ADS)

    Fakcharoenphol, Witat; Stelzer, Timothy

    2014-06-01

    In this clinical study on helping students prepare for an exam, we compared three different treatments. All students were asked to take a practice exam. One group was then given worked-out solutions for that exam, another group was given the solutions and targeted exercises to do as homework based on the result of their practice exam, and the third group was given the solutions, homework, and also an hour of one-on-one tutoring. Participants from all three conditions significantly outperformed the control group on the midterm exam. However, participants that had one-on-one tutoring did not outperform the other two participant groups.

  16. Treatment plan comparison between helical tomotherapy and MLC-based IMRT using radiobiological measures

    NASA Astrophysics Data System (ADS)

    Mavroidis, Panayiotis; Costa Ferreira, Brigida; Shi, Chengyu; Lind, Bengt K.; Papanikolaou, Nikos

    2007-07-01

    The rapid implementation of advanced treatment planning and delivery technologies for radiation therapy has brought new challenges in evaluating the most effective treatment modality. Intensity-modulated radiotherapy (IMRT) using multi-leaf collimators (MLC) and helical tomotherapy (HT) are becoming popular modes of treatment delivery and their application and effectiveness continues to be investigated. Presently, there are several treatment planning systems (TPS) that can generate and optimize IMRT plans based on user-defined objective functions for the internal target volume (ITV) and organs at risk (OAR). However, the radiobiological parameters of the different tumours and normal tissues are typically not taken into account during dose prescription and optimization of a treatment plan or during plan evaluation. The suitability of a treatment plan is typically decided based on dosimetric criteria such as dose-volume histograms (DVH), maximum, minimum, mean and standard deviation of the dose distribution. For a more comprehensive treatment plan evaluation, the biologically effective uniform dose ({\\bar{\\bar{D}}}) is applied together with the complication-free tumour control probability (P+). Its utilization is demonstrated using three clinical cases that were planned with two different forms of IMRT. In this study, three different cancer types at different anatomical sites were investigated: head and neck, lung and prostate cancers. For each cancer type, a linac MLC-based step-and-shoot IMRT plan and a HT plan were developed. The MLC-based IMRT treatment plans were developed on the Philips treatment-planning platform, using the Pinnacle 7.6 software release. For the tomotherapy HiArt plans, the dedicated tomotherapy treatment planning station was used, running version 2.1.2. By using {\\bar{\\bar{D}}} as the common prescription point of the treatment plans and plotting the tissue response probabilities versus {\\bar{\\bar{D}}} for a range of prescription doses

  17. SU-E-T-506: Dosimetric Verification of Photon MLC Delivered Electron Fields for Implementing MERT On An Artiste Linac

    SciTech Connect

    Jin, L; Eldib, A; Li, J; Wang, L; Ma, C; Fan, J

    2014-06-01

    Purpose: To verify the dose accuracy of photon MLC delivered electron fields for implementing energy-intensity modulated electron radiotherapy (MERT) on an Artiste linac. Methods: It was proposed to deliver MERT on an Artiste linac at a short SSD (60 cm) to reduce beam penumbra caused by electron scatters. An in-house developed Monte Carlo (MC)-based dose calculation/optimization planning code was used for treatment planning. Our previous study showed that the measured dose distribution of a breast plan showed good agreement with the calculations in low-medium dose regions while the differences in high dose regions were outstanding. A continuous work found that the discrepancy is mainly caused by improper modeling in MC for the single focused MLC in the Artiste which was simplified as double focused in the previous MC simulations. With this remodeled MLC in the calculations, an energy-intensity modulated electron plan using 6, 9, 12 and 15 MeV was generated for a breast treatment on a breast phantom at a 60 cm SSD and recalculated regarding a solid water phantom. For a test study, four of MLC segments (each with a different energy) generated in the plan were delivered to the phantom and a film measurement was performed at the depth of 2 cm. The measured 2D dose distribution was then compared with calculations. Results: For composite doses of the four segments, measured 2D dose distributions overall agree well with the calculations (3mm/3%) in most area. The separate measurement for a single MLC segment for each of energies also showed the consistence with the calculations. Conclusion: After remodeling MLC in the MC calculations, the measured dose distribution for a subset of MLC segments from a MERT plan showed good agreement. Further detailed verification for the full plan will be the work in the next step.

  18. Distinct gene expression patterns in skeletal and cardiac muscle are dependent on common regulatory sequences in the MLC1/3 locus.

    PubMed Central

    McGrew, M J; Bogdanova, N; Hasegawa, K; Hughes, S H; Kitsis, R N; Rosenthal, N

    1996-01-01

    The myosin light-chain 1/3 locus (MLC1/3) is regulated by two promoters and a downstream enhancer element which produce two protein isoforms in fast skeletal muscle at distinct stages of mouse embryogenesis. We have analyzed the expression of transcripts from the internal MLC3 promoter and determined that it is also expressed in the atria of the heart. Expression from the MLC3 promoter in these striated muscle lineages is differentially regulated during development. In transgenic mice, the MLC3 promoter is responsible for cardiac-specific reporter gene expression while the downstream enhancer augments expression in skeletal muscle. Examination of the methylation status of endogenous and transgenic promoter and enhancer elements indicates that the internal promoter is not regulated in a manner similar to that of the MLC1 promoter or the downstream enhancer. A GATA protein consensus sequence in the proximal MLC3 promoter but not the MLC1 promoter binds with high affinity to GATA-4, a cardiac muscle- and gut-specific transcription factor. Mutation of either the MEF2 or GATA motifs in the MLC3 promoter attenuates its activity in both heart and skeletal muscles, demonstrating that MLC3 expression in these two diverse muscle types is dependent on common regulatory elements. PMID:8754853

  19. Development and evaluation of aperture-based complexity metrics using film and EPID measurements of static MLC openings

    SciTech Connect

    Götstedt, Julia; Karlsson Hauer, Anna; Bäck, Anna

    2015-07-15

    Purpose: Complexity metrics have been suggested as a complement to measurement-based quality assurance for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). However, these metrics have not yet been sufficiently validated. This study develops and evaluates new aperture-based complexity metrics in the context of static multileaf collimator (MLC) openings and compares them to previously published metrics. Methods: This study develops the converted aperture metric and the edge area metric. The converted aperture metric is based on small and irregular parts within the MLC opening that are quantified as measured distances between MLC leaves. The edge area metric is based on the relative size of the region around the edges defined by the MLC. Another metric suggested in this study is the circumference/area ratio. Earlier defined aperture-based complexity metrics—the modulation complexity score, the edge metric, the ratio monitor units (MU)/Gy, the aperture area, and the aperture irregularity—are compared to the newly proposed metrics. A set of small and irregular static MLC openings are created which simulate individual IMRT/VMAT control points of various complexities. These are measured with both an amorphous silicon electronic portal imaging device and EBT3 film. The differences between calculated and measured dose distributions are evaluated using a pixel-by-pixel comparison with two global dose difference criteria of 3% and 5%. The extent of the dose differences, expressed in terms of pass rate, is used as a measure of the complexity of the MLC openings and used for the evaluation of the metrics compared in this study. The different complexity scores are calculated for each created static MLC opening. The correlation between the calculated complexity scores and the extent of the dose differences (pass rate) are analyzed in scatter plots and using Pearson’s r-values. Results: The complexity scores calculated by the edge

  20. SU-E-T-583: Optimizing the MLC Model Parameters for IMRT in the RayStation Treatment Planning System

    SciTech Connect

    Chen, S; Yi, B; Xu, H; Yang, X; Prado, K; D'Souza, W

    2014-06-01

    Purpose: To optimize the MLC model parameters for IMRT in the RayStation v.4.0 planning system and for a Varian C-series Linac with a 120-leaf Millennium MLC. Methods: The RayStation treatment planning system models rounded leaf-end MLC with the following parameters: average transmission, leaf-tip width, tongue-and-groove, and position offset. The position offset was provided by Varian. The leaf-tip width was iteratively evaluated by comparing computed and measured transverse dose profiles of MLC-defined fields at dmax in water. The profile comparison was also used to verify the MLC position offset. The transmission factor and leaf tongue width were derived iteratively by optimizing five clinical patient IMRT QA Results: brain, lung, pancreas, head-and-neck (HN), and prostate. The HN and prostate cases involved splitting fields. Verifications were performed with Mapcheck2 measurements and Monte Carlo calculations. Finally, the MLC model was validated using five test IMRT cases from the AAPM TG119 report. Absolute gamma analyses (3mm/3% and 2mm/2%) were applied. In addition, computed output factors for MLC-defined small fields (2×2, 3×3, 4×4, 6×6cm) of both 6MV and 18MV were compared to those measured by the Radiological Physics Center (RPC). Results: Both 6MV and 18MV models were determined to have the same MLC parameters: 2.5% transmission, tongue-and-groove 0.05cm, and leaftip 0.3cm. IMRT QA analysis for five cases in TG119 resulted in a 100% passing rate with 3mm/3% gamma analysis for 6MV, and >97.5% for 18MV. With 2mm/2% gamma analysis, the passing rate was >94.6% for 6MV and >90.9% for 18MV. The difference between computed output factors in RayStation and RPC measurements was less than 2% for all MLCdefined fields, which meets the RPC's acceptance criterion. Conclusion: The rounded leaf-end MLC model in RayStation 4.0 planning system was verified and IMRT commissioning was clinically acceptable. The IMRT commissioning was well validated using guidance from

  1. SU-E-J-67: Evaluation of Adaptive MLC Morphing for Online Correction of Prostate Cancer Radiotherapy

    SciTech Connect

    Sandhu, R; Qin, A; Yan, D

    2015-06-15

    Purpose: Online adaptive MLC morphing is desirable over translational couch shifts to accommodate target position as well as anatomic changes. A reliable method of adaptive MLC segment to target during prostate cancer IMRT treatment is proposed and evaluated by comparison with daily online-image guidance (IGRT) correction and online-IMRT planning. Methods: The MLC adaptive algorithm involves following steps; move the MLC segments according to target translational shifts, and then morph the segment shape to maintain the spatial relationship between the planning-target contour and MLC segment. Efficacy of this method was evaluated retrospectively using daily-CBCT images on seven prostate patients treated with seven-beam IMRT treatment to deliver 64Gy in 20 fractions. Daily modification was simulated with three approaches; daily-IGRT correction based on implanted radio-markers, adaptive MLC morphing, and online-IMRT planning, with no-residual variation. The selected dosimetric endpoints and nEUD (normalized equivalent uniform dose to online-IMRT planning) of each organ of interest were determined for evaluation and comparison. Results: For target(prostate), bladder and rectal-wall, the mean±sd of nEUD were 97.6%+3.2%, 103.9%±4.9% and 97.4%±1.1% for daily-IGRT correction; and 100.2%+0.2%, 108.9%±5.1% and 99.8%±1.2% for adaptive MLC morphing, respectively. For daily-IGRT correction, adaptive MLC morphing and online-IMRT planning, target D99 was <95% of the prescription dose in 30%, 0% and 0% of 140 fractions, respectively. For the rectal-wall, D5 exceeded 105% of the planned-D5 in 2.8%, 11.4% and 0% of 140 fractions, respectively. For the bladder, Dmax exceeded 105% of the planned-D5 in 2.8%, 5.6% and 0% of 140 fractions, respectively. D30 of bladder and rectal-wall were well within the planned-D30 for all three approaches. Conclusion: The proposed method of adaptive MLC morphing can be beneficial for the prostate patient population with large deformation and

  2. Monitoring daily MLC positional errors using trajectory log files and EPID measurements for IMRT and VMAT deliveries

    NASA Astrophysics Data System (ADS)

    Agnew, A.; Agnew, C. E.; Grattan, M. W. D.; Hounsell, A. R.; McGarry, C. K.

    2014-05-01

    This work investigated the differences between multileaf collimator (MLC) positioning accuracy determined using either log files or electronic portal imaging devices (EPID) and then assessed the possibility of reducing patient specific quality control (QC) via phantom-less methodologies. In-house software was developed, and validated, to track MLC positional accuracy with the rotational and static gantry picket fence tests using an integrated electronic portal image. This software was used to monitor MLC daily performance over a 1 year period for two Varian TrueBeam linear accelerators, with the results directly compared with MLC positions determined using leaf trajectory log files. This software was validated by introducing known shifts and collimator errors. Skewness of the MLCs was found to be 0.03 ± 0.06° (mean ±1 standard deviation (SD)) and was dependent on whether the collimator was rotated manually or automatically. Trajectory log files, analysed using in-house software, showed average MLC positioning errors with a magnitude of 0.004 ± 0.003 mm (rotational) and 0.004 ± 0.011 mm (static) across two TrueBeam units over 1 year (mean ±1 SD). These ranges, as indicated by the SD, were lower than the related average MLC positioning errors of 0.000 ± 0.025 mm (rotational) and 0.000 ± 0.039 mm (static) that were obtained using the in-house EPID based software. The range of EPID measured MLC positional errors was larger due to the inherent uncertainties of the procedure. Over the duration of the study, multiple MLC positional errors were detected using the EPID based software but these same errors were not detected using the trajectory log files. This work shows the importance of increasing linac specific QC when phantom-less methodologies, such as the use of log files, are used to reduce patient specific QC. Tolerances of 0.25 mm have been created for the MLC positional errors using the EPID-based automated picket fence test. The software allows diagnosis

  3. Effectiveness and Safety of MLC601 in the Treatment of Mild to Moderate Alzheimer's Disease: A Multicenter, Randomized Controlled Trial

    PubMed Central

    Pakdaman, Hossein; Harandi, Ali Amini; Hatamian, Hamidreza; Tabatabae, Mojgan; Delavar Kasmaei, Hosein; Ghassemi, Amirhossein; Gharagozli, Koroush; Ashrafi, Farzad; Emami Naeini, Pardis; Tavakolian, Mehrnaz; Shahin, Darush

    2015-01-01

    Background MLC601 is a possible modulator of amyloid precursor protein processing, and in a clinical trial study MLC601 showed some effectiveness in cognitive function in Alzheimer's disease (AD) patients. We aimed to evaluate the effectiveness and safety of MLC601 in the treatment of mild to moderate AD as compared to 3 approved cholinesterase inhibitors (ChEIs) including donepezil, rivastigmine and galantamine. Methods In a multicenter, nonblinded, randomized controlled trial, 264 volunteers with AD were randomly divided into 4 groups of 66; groups 1, 2, 3 and 4 received donepezil, rivastigmine, MLC601 and galantamine, respectively. Subjects underwent a clinical diagnostic interview and a cognitive/functional battery including the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale – Cognitive subscale (ADAS-Cog). Patients were visited every 4 months, and the score of cognition was recorded by the neurologists. Results There were no significant differences in age, sex, marital status and baseline score of cognition among the 4 groups. In total, 39 patients (14.7%) left the study. Trend of cognition changes based on the modifications over the time for MMSE and ADAS-cog scores did not differ significantly among groups (p = 0.92 for MMSE and p = 0.87 for ADAS-Cog). Conclusion MLC601 showed a promising safety profile and also efficacy compared to 3 FDA-approved ChEIs. PMID:25873931

  4. Improving the performance of BICM-ID and MLC systems with different FEC codes

    NASA Astrophysics Data System (ADS)

    Arafa, T.; Sauer-Greff, W.; Urbansky, R.

    2013-07-01

    In bandwidth limited communication systems, the high data rate transmission with performance close to capacity limits is achieved by applying multilevel modulation schemes in association with powerful forward error correction (FEC) coding, i.e. coded modulation systems. The most important practical approaches to coded modulation systems are multilevel coding with multistage decoding (MLC/MSD) and bit interleaved coded modulation with iterative demapping and decoding (BICM-ID). Multilevel modulation formats such as M-QAM, which can be used as a part of coded modulation systems, have the capability of multilevel protection. Based on this fact, we investigate the methods to improve the performance of BICM-ID using multiple interleavers with different binary channel coding schemes such as convolutional codes, turbo codes and low-density parity-check (LDPC) codes. Moreover, an MLC system with parallel decoding on levels (PDL) at the receiver is considered. In our contribution, we propose to design the individual coding schemes using the extrinsic information transfer (EXIT) charts for individual bit levels in the constellation. Our simulation results show that the BICM-ID systems, taking into account different bit-level protections, can provide an improvement of 0.65 dB, 1.2 dB and 1.5 dB for 256-QAM with turbo, LDPC and convolutional codes, respectively. On the other hand, MLC systems with PDL designed using EXIT charts for individual bit levels can slightly improve the performance and eliminate the error floor compared to the systems with MSD.

  5. Improving IMRT-plan quality with MLC leaf position refinement post plan optimization

    PubMed Central

    Niu, Ying; Zhang, Guowei; Berman, Barry L.; Parke, William C.; Yi, Byongyong; Yu, Cedric X.

    2012-01-01

    Purpose: In intensity-modulated radiation therapy (IMRT) planning, reducing the pencil-beam size may lead to a significant improvement in dose conformity, but also increase the time needed for the dose calculation and plan optimization. The authors develop and evaluate a postoptimization refinement (POpR) method, which makes fine adjustments to the multileaf collimator (MLC) leaf positions after plan optimization, enhancing the spatial precision and improving the plan quality without a significant impact on the computational burden. Methods: The authors’ POpR method is implemented using a commercial treatment planning system based on direct aperture optimization. After an IMRT plan is optimized using pencil beams with regular pencil-beam step size, a greedy search is conducted by looping through all of the involved MLC leaves to see if moving the MLC leaf in or out by half of a pencil-beam step size will improve the objective function value. The half-sized pencil beams, which are used for updating dose distribution in the greedy search, are derived from the existing full-sized pencil beams without need for further pencil-beam dose calculations. A benchmark phantom case and a head-and-neck (HN) case are studied for testing the authors’ POpR method. Results: Using a benchmark phantom and a HN case, the authors have verified that their POpR method can be an efficient technique in the IMRT planning process. Effectiveness of POpR is confirmed by noting significant improvements in objective function values. Dosimetric benefits of POpR are comparable to those of using a finer pencil-beam size from the optimization start, but with far less computation and time. Conclusions: The POpR is a feasible and practical method to significantly improve IMRT-plan quality without compromising the planning efficiency. PMID:22894437

  6. SU-D-18A-05: Assessing Elekta MLC Tracking Performance

    SciTech Connect

    Glitzner, M; Crijns, S; Lagendijk, J; Raaymakers, B

    2014-06-01

    Purpose: To investigate the technical feasibility of using Elekta MLCs in tracked radiotherapy, specifically to show the capability of an Agility MLC to follow model tumor trajectories using object tracking. The system performance of the MLC is to be assessed via dosimetric experiments and temporal response measures. Methods: The system observer in the tracking cascade consisted of a camera serving for this proof of concept; Images of a moving object were acquired continuously and decorrelated for the position information, which was fed forward to the RT computer controlling the MLC via an interface provided by Elekta. The 1D motion (in the direction of the leaves) was induced by a CIRS motion controller. Additionally, the aperture position was observed by means of the light field of the linac. Calculating the phase between aperture and object yielded the mean aperture lag for the current setup. The object was restricted to sinusoidal motion with a period of 10s. For dosimetry, GafChromic radiosensitive film was irradiated with a total dose of 1000MU using an aperture size of 40mm and a motion range of 30mm. Results: Object tracking can substantially reconstruct the geometric dose response of a static target. In the dynamic case, dose is smeared out into the legs of the static distribution, leading to a reduced plateau and increased FWHM of 5mm, compared to the static width of 38mm. The time-lag between object and aperture was determined to be approximately 300ms for the current set-up. Conclusion: We demonstrated a tracking experiment performed on a clinical Elekta linear accelator for the first time. Observed profile variations show the dosimetric impact of tracked delivery. The determined lag is a valuable descriptor for a future tracking cascade employing predictor filters. The performed experiments are generic and possible predecessors for future applications with MR-Linac or ultrasound probes. Conflict of interest: this project is partly funded by Elekta.

  7. Dosimetric and mechanical characteristics of a commercial dynamic {mu}MLC used in SRS

    SciTech Connect

    Galal, Mohamed M.; Keogh, Sinead; Khalil, Sultan

    2011-07-15

    Purpose: The aim of this work is to carry out mechanical and dosimetric assessments on a commercial dynamic micromulti leaf collimator system to be used for stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). Mechanical parameters such as leaf position accuracy with different gantry angles and leaf position reproducibility were measured. Also dosimetric measurements of the interleaf leakage, intraleaf transmission, penumbra width, and light field alignment were carried out. Furthermore, measurements of output factors (S{sub cp}) and in-air factors (S{sub c}) for the {mu}MLC system will be reported. Methods: EBT2 films were used to assess the leaf position error with gantry angle and after stress test, penumbra width and light field alignment. Leaf leakage was quantified using both EBT2 film and a pinpoint ion chamber. With regard to output factors, the pinpoint chamber was placed in a water phantom at 10 cm depth and 100 cm SSD. For in-air output factor measurements, 0.2 cm of brass was placed above the photon diode as build-up. Results: Measurements of mechanical parameters gave values of 0.05 cm (SD 0.035) for the average leaf position accuracy for different gantry angles and after stress test. Dosimetric measurements, yielded values of 0.22 {+-} 0.01 and 0.24 {+-} 0.01 cm, respectively, for side and head leaf penumbras. Also, average leaf abutting, leakage and transmission were found to be 0.65, 0.91, and 0.20%, respectively. Conclusions: (a) The add-on {mu}MLC system in combination with our LINAC has been commissioned to be used for clinical purposes and showed good agreement with published results for different {mu}MLC types. (b) This work has lead to the recommendation that leaves should be recalibrated after ten static beams or after each dynamic arc.

  8. Quantification of the impact of MLC modeling and tissue heterogeneities on dynamic IMRT dose calculations

    SciTech Connect

    Mihaylov, I. B.; Lerma, F. A.; Fatyga, M.; Siebers, J. V.

    2007-04-15

    This study quantifies the dose prediction errors (DPEs) in dynamic IMRT dose calculations resulting from (a) use of an intensity matrix to estimate the multi-leaf collimator (MLC) modulated photon fluence (DPE{sub IGfluence}) instead of an explicit MLC particle transport, and (b) handling of tissue heterogeneities (DPE{sub hetero}) by superposition/convolution (SC) and pencil beam (PB) dose calculation algorithms. Monte Carlo (MC) computed doses are used as reference standards. Eighteen head-and-neck dynamic MLC IMRT treatment plans are investigated. DPEs are evaluated via comparing the dose received by 98% of the GTV (GTV D{sub 98%}), the CTV D{sub 95%}, the nodal D{sub 90%}, the cord and the brainstem D{sub 02%}, the parotid D{sub 50%}, the parotid mean dose (D{sub Mean}), and generalized equivalent uniform doses (gEUDs) for the above structures. For the MC-generated intensity grids, DPE{sub IGfluence} is within {+-}2.1% for all targets and critical structures. The SC algorithm DPE{sub hetero} is within {+-}3% for 98.3% of the indices tallied, and within {+-}3.4% for all of the tallied indices. The PB algorithm DPE{sub hetero} is within {+-}3% for 92% of the tallied indices. Statistical equivalence tests indicate that PB DPE{sub hetero} requires a {+-}3.6% interval to state equivalence with the MC standard, while the intervals are <1.5% for SC DPE{sub hetero} and DPE{sub IGfluence}. Overall, these results indicate that SC and MC IMRT dose calculations which use MC-derived intensity matrices for fluence prediction do not introduce significant dose errors compared with full Monte Carlo dose computations; however, PB algorithms may result in clinically significant dose deviations.

  9. Determination of the optimal tolerance for MLC positioning in sliding window and VMAT techniques

    SciTech Connect

    Hernandez, V. Abella, R.; Calvo, J. F.; Jurado-Bruggemann, D.; Sancho, I.; Carrasco, P.

    2015-04-15

    Purpose: Several authors have recommended a 2 mm tolerance for multileaf collimator (MLC) positioning in sliding window treatments. In volumetric modulated arc therapy (VMAT) treatments, however, the optimal tolerance for MLC positioning remains unknown. In this paper, the authors present the results of a multicenter study to determine the optimal tolerance for both techniques. Methods: The procedure used is based on dynalog file analysis. The study was carried out using seven Varian linear accelerators from five different centers. Dynalogs were collected from over 100 000 clinical treatments and in-house software was used to compute the number of tolerance faults as a function of the user-defined tolerance. Thus, the optimal value for this tolerance, defined as the lowest achievable value, was investigated. Results: Dynalog files accurately predict the number of tolerance faults as a function of the tolerance value, especially for low fault incidences. All MLCs behaved similarly and the Millennium120 and the HD120 models yielded comparable results. In sliding window techniques, the number of beams with an incidence of hold-offs >1% rapidly decreases for a tolerance of 1.5 mm. In VMAT techniques, the number of tolerance faults sharply drops for tolerances around 2 mm. For a tolerance of 2.5 mm, less than 0.1% of the VMAT arcs presented tolerance faults. Conclusions: Dynalog analysis provides a feasible method for investigating the optimal tolerance for MLC positioning in dynamic fields. In sliding window treatments, the tolerance of 2 mm was found to be adequate, although it can be reduced to 1.5 mm. In VMAT treatments, the typically used 5 mm tolerance is excessively high. Instead, a tolerance of 2.5 mm is recommended.

  10. The Formal Oral Group Exam: Challenges and Possibilities--The Oral Exam and Critical Thinking.

    ERIC Educational Resources Information Center

    Dressel, Janice Hartwick

    Defining critical thinking as a conscious process means that teachers can make students aware of the process and can affect the process. In addition, teachers can help students to evaluate their use of the process. The goal in any course is to involve students in the practice of critical thinking, and the oral exam reflects the students'…

  11. Engagement with Online Pre-Exam Formative Tests Improves Exam Performance and Feedback Satisfaction

    ERIC Educational Resources Information Center

    Hope, Sheila A.; Polwart, Anthony

    2012-01-01

    The National Union of Students (NUS) National Student Experience Report identified examination feedback as an area where students had particular concerns. This finding was echoed in the authors' institution and triggered an action research project to investigate ways of improving students' perceptions of pre- and post-exam feedback. We report the…

  12. The AP Exam: Is This How People Learn?

    NASA Astrophysics Data System (ADS)

    Eisenkraft, Arthur

    2001-04-01

    The AP Physics course is often the most rigorous experience a student will have in high school. The culminating AP exam tests problem solving skills using traditional questions that are found in most freshmen books. The nature of the test imparts a specific focus on the course, which in turn shapes the students' impression of physics. Over the past decade, we have been discovering a great deal about how people learn in general. We have also learned specifically about the inadequacies of traditional physics instruction. Has the AP exam kept pace with this new knowledge? Can the AP exam be altered in order to require a different type of instruction that is informed by cognitive research? What would the new exam look like? Samples of exam questions from AP Exams will be viewed through the lens of cognitive research. Alternative physics challenges will be presented and the difficulties in grading these questions noted.

  13. Comparative Analysis of Different Measurement Techniques for MLC Characterization: Preliminary Results

    SciTech Connect

    Larraga-Gutierrez, J. M.; Ballesteros-Zebadua, P.; Garcia-Garduno, O. A.; Martinez-Davalos, A.; Rodriguez-Villafuerte, M.; Moreno-Jimenez, S.; Celis, M. A.

    2008-08-11

    Radiation transmission, leakage and beam penumbra are essential dosimetric parameters related to the commissioning of a multileaf collimation system. This work shows a comparative analysis of commonly used film detectors: X-OMAT V2 and EDR2 radiographic films, and GafChromic EBT registered radiochromic film. The results show that X-OMAT over-estimates radiation leakage and 80-20% beam penumbra. However, according to the reference values reported by the manufacturer for these dosimetric parameters, all three films are adequate for MLC dosimetric characterization, but special care must be taken when X-OMAT V2 film is used due to its low energy photon dependence.

  14. Characterization of megavoltage electron beams delivered through a photon multi-leaf collimator (pMLC)

    NASA Astrophysics Data System (ADS)

    du Plessis, F. C. P.; Leal, A.; Stathakis, S.; Xiong, W.; Ma, C.-M.

    2006-04-01

    A study is presented that characterizes megavoltage electron beams delivered through an existing double-focused photon multi-leaf collimator (pMLC) using film measurements in a solid water phantom. Machine output stability and linearity were evaluated as well as the effect of source-to-surface distance (SSD) and field size on the penumbra for electron energies between 6 and 18 MeV over an SSD range of 60-100 cm. Penumbra variations as a function of field size, depth of measurement and the influence of the jaws were also studied. Field abutment, field flatness and target coverage for segmented beams were also addressed. The measured field size for electrons transported through the pMLC was the same as that for an x-ray beam up to SSDs of 70 cm. At larger SSD, the lower energy electron fields deviated from the projected field. Penumbra data indicated that 60 cm SSD was the most favourable treatment distance. Backprojection of P20-80 penumbra data yielded a virtual source position located at 98.9 cm from the surface for 18 MeV electrons. For 6 MeV electrons, the virtual source position was at a distance of 82.6 cm. Penumbra values were smaller for small beam slits and reached a near-constant value for field widths larger than 5 cm. The influence of the jaws had a small effect on the penumbra. The R90 values ranged from 1.4 to 4.8 cm between 6 and 21 MeV as measured at 60 cm SSD for a 9 × 9 cm2 field. Uniformity and penumbra improvement could be demonstrated using weighted abutted fields especially useful for small segments. No detectable electron leakage through the pMLC was observed. Bremsstrahlung measurements taken at 60 cm SSD for a 9 × 9 cm2 field as shaped by the pMLC compared within 1% to bremsstrahlung measurements taken at 100 cm SSD for a 10 × 10 cm2 electron applicator field at 100 cm SSD.

  15. ExamFolder(R) technology integrator

    NASA Astrophysics Data System (ADS)

    Scott, David K.

    1994-10-01

    Cargo examination systems will integrate multiple sensors because single sensor systems can be defeated. Trials with multiple sensors have also resulted in both increased inspection accuracy and throughput. The traditional integration point for multiple sensor outputs is paper. Cargo inspection analysts must evaluate a file folder containing many interrelated pieces of paper within minutes. File folders with paper have proven to be an obsolete medium for complex data presentation. A computer-based system, ExamFolder Technology Integrator uses an open architecture to receive input from multiple sensors treating each input data set as a document. Documents from any sensor, even those yet to be developed, can be collected, structured, and displayed to the analyst. The documents include, but are not limited to: digital data, imagery, video and digitized voice. The system structures the documents for scrutinizing manifested cargo, shipper, shipping agent, carrier, broker, forwarder and consignee histories. This reduces pressure on the analyst for timely completion of the inspection. The ExamFolder Technology Integrator is an efficient, sensor-vendor independent, computer screen-based, cargo inspection system providing meaningful information to the cargo analyst.

  16. EXAM: A search for extragalactic antimatter

    SciTech Connect

    Crary, D.J.

    1991-01-01

    This thesis presents results from a search for extragalactic antimatter in the cosmic rays (the EXAM experiment). The reasons for undertaking a search for antimatter are given, along with various arguments that indicate that a antimatter fraction of 10{sup {minus}6} {minus} 10{sup {minus}7} in the cosmic-ray flux at earth would not be inconsistent with current antimatter limits obtained from cosmic-ray experiments or with limits set by gamma-ray observations. An experimental technique sensitive to antinuclei with charge Z near iron (Z = 26) is reviewed. This technique uses a combination of active detectors (scintillators, Cerenkov counters) and CR-39 track-etch detectors to provide a unique signature for antimatter detection at a level consistent with the flux estimates given above. This is followed by description of the implementation of this technique (the EXAM detector), along with a summary of the data analysis to date. Directions for future work are described. A detailed description of the microscope system used in the automated analysis of the CR-39 plastic is presented.

  17. The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

    SciTech Connect

    Falk, Marianne; Larsson, Tobias; Keall, Paul; Chul Cho, Byung; Aznar, Marianne; Korreman, Stine; Poulsen, Per; Munck af Rosenschoeld, Per

    2012-03-15

    Purpose: Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced by using a leaf position constraint (LPC) that reduces the difference in the position of adjacent MLC leaves in the plan. The purpose of this study was to investigate the impact of the LPC on the quality of inversely optimized arc radiotherapy plans and the effect of the MLC motion pattern on the dosimetric accuracy of MLC tracking delivery. Specifically, the possibility of predicting the accuracy of MLC tracking delivery based on the plan modulation was investigated. Methods: Inversely optimized arc radiotherapy plans were created on CT-data of three lung cancer patients. For each case, five plans with a single 358 deg. arc were generated with LPC priorities of 0 (no LPC), 0.25, 0.5, 0.75, and 1 (highest possible LPC), respectively. All the plans had a prescribed dose of 2 Gy x 30, used 6 MV, a maximum dose rate of 600 MU/min and a collimator angle of 45 deg. or 315 deg. To quantify the plan modulation, an average adjacent leaf distance (ALD) was calculated by averaging the mean adjacent leaf distance for each control point. The linear relationship between the plan quality [i.e., the calculated dose distributions and the number of monitor units (MU)] and the LPC was investigated, and the linear regression coefficient as well as a two tailed confidence level of 95% was used in the evaluation. The effect of the plan modulation on the performance of MLC tracking was tested by delivering the plans to a cylindrical diode array phantom moving with sinusoidal motion in the superior-inferior direction with a peak-to-peak displacement of 2 cm and a cycle time of 6 s. The delivery was adjusted to the target motion using MLC tracking, guided in real-time by an infrared optical system

  18. The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

    PubMed Central

    Falk, Marianne; Larsson, Tobias; Keall, Paul; Chul Cho, Byung; Aznar, Marianne; Korreman, Stine; Poulsen, Per; af Rosenschöld, Per Munck

    2012-01-01

    Purpose: Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced by using a leaf position constraint (LPC) that reduces the difference in the position of adjacent MLC leaves in the plan. The purpose of this study was to investigate the impact of the LPC on the quality of inversely optimized arc radiotherapy plans and the effect of the MLC motion pattern on the dosimetric accuracy of MLC tracking delivery. Specifically, the possibility of predicting the accuracy of MLC tracking delivery based on the plan modulation was investigated. Methods: Inversely optimized arc radiotherapy plans were created on CT-data of three lung cancer patients. For each case, five plans with a single 358° arc were generated with LPC priorities of 0 (no LPC), 0.25, 0.5, 0.75, and 1 (highest possible LPC), respectively. All the plans had a prescribed dose of 2 Gy × 30, used 6 MV, a maximum dose rate of 600 MU/min and a collimator angle of 45° or 315°. To quantify the plan modulation, an average adjacent leaf distance (ALD) was calculated by averaging the mean adjacent leaf distance for each control point. The linear relationship between the plan quality [i.e., the calculated dose distributions and the number of monitor units (MU)] and the LPC was investigated, and the linear regression coefficient as well as a two tailed confidence level of 95% was used in the evaluation. The effect of the plan modulation on the performance of MLC tracking was tested by delivering the plans to a cylindrical diode array phantom moving with sinusoidal motion in the superior–inferior direction with a peak-to-peak displacement of 2 cm and a cycle time of 6 s. The delivery was adjusted to the target motion using MLC tracking, guided in real-time by an infrared optical system. The

  19. Activation of ATP-sensitive potassium channels as an element of the neuroprotective effects of the Traditional Chinese Medicine MLC901 against oxygen glucose deprivation.

    PubMed

    Moha Ou Maati, H; Borsotto, M; Chatelain, F; Widmann, C; Lazdunski, M; Heurteaux, C

    2012-09-01

    NeuroAid (MLC601 and MLC901), a Traditional Medicine used in China for patients after stroke has been reported in preclinical models of ischemia to induce neuroprotection and neuroplasticity. This work shows the effects of MLC901 on an in vitro model of oxygen glucose deprivation (OGD). MLC901 prevents neuronal death induced by 120 min OGD and decreases the exaggerated Ca²⁺ entry in mature cortical neurons exposed to 120 min OGD. The neuroprotective effect of MLC901 is associated with a large hyperpolarization of ∼20 mV which is antagonized by glibenclamide, the specific inhibitor of K(ATP) channels. In addition MLC901 strengthens the activation of K(ATP) channels. MLC901 has been directly shown to act as an activator of K(ATP) channels as potent as the classical K(ATP) channel opener. The capacity of MLC901 to produce a large hyperpolarization, particularly in neurons that have suffered from energy deprivation probably plays an important role in the neuroprotective effects of this traditional medicine that comes in addition to its previously demonstrated neuroregenerative properties. PMID:22659084

  20. SU-E-T-405: Robustness of Volumetric-Modulated Arc Therapy (VMAT) Plans to Systematic MLC Positional Errors

    SciTech Connect

    Qi, P; Xia, P

    2014-06-01

    Purpose: To evaluate the dosimetric impact of systematic MLC positional errors (PEs) on the quality of volumetric-modulated arc therapy (VMAT) plans. Methods: Five patients with head-and-neck cancer (HN) and five patients with prostate cancer were randomly chosen for this study. The clinically approved VMAT plans were designed with 2–4 coplanar arc beams with none-zero collimator angles in the Pinnacle planning system. The systematic MLC PEs of 0.5, 1.0, and 2.0 mm on both MLC banks were introduced into the original VMAT plans using an in-house program, and recalculated with the same planned Monitor Units in the Pinnacle system. For each patient, the original VMAT plans and plans with MLC PEs were evaluated according to the dose-volume histogram information and Gamma index analysis. Results: For one primary target, the ratio of V100 in the plans with 0.5, 1.0, and 2.0 mm MLC PEs to those in the clinical plans was 98.8 ± 2.2%, 97.9 ± 2.1%, 90.1 ± 9.0% for HN cases and 99.5 ± 3.2%, 98.9 ± 1.0%, 97.0 ± 2.5% for prostate cases. For all OARs, the relative difference of Dmean in all plans was less than 1.5%. With 2mm/2% criteria for Gamma analysis, the passing rates were 99.0 ± 1.5% for HN cases and 99.7 ± 0.3% for prostate cases between the planar doses from the original plans and the plans with 1.0 mm MLC errors. The corresponding Gamma passing rates dropped to 88.9 ± 5.3% for HN cases and 83.4 ± 3.2% for prostate cases when comparing planar doses from the original plans and the plans with 2.0 mm MLC errors. Conclusion: For VMAT plans, systematic MLC PEs up to 1.0 mm did not affect the plan quality in term of target coverage, OAR sparing, and Gamma analysis with 2mm/2% criteria.

  1. Development of a Monte Carlo model for the Brainlab microMLC

    NASA Astrophysics Data System (ADS)

    Belec, Jason; Patrocinio, Horacio; Verhaegen, Frank

    2005-03-01

    Stereotactic radiosurgery with several static conformal beams shaped by a micro multileaf collimator (μMLC) is used to treat small irregularly shaped brain lesions. Our goal is to perform Monte Carlo calculations of dose distributions for certain treatment plans as a verification tool. A dedicated μMLC component module for the BEAMnrc code was developed as part of this project and was incorporated in a model of the Varian CL2300 linear accelerator 6 MV photon beam. As an initial validation of the code, the leaf geometry was visualized by tracing particles through the component module and recording their position each time a leaf boundary was crossed. The leaf dimensions were measured and the leaf material density and interleaf air gap were chosen to match the simulated leaf leakage profiles with film measurements in a solid water phantom. A comparison between Monte Carlo calculations and measurements (diode, radiographic film) was performed for square and irregularly shaped fields incident on flat and homogeneous water phantoms. Results show that Monte Carlo calculations agree with measured dose distributions to within 2% and/or 1 mm except for field size smaller than 1.2 cm diameter where agreement is within 5% due to uncertainties in measured output factors.

  2. Development of a Monte Carlo model for the Brainlab microMLC.

    PubMed

    Belec, Jason; Patrocinio, Horacio; Verhaegen, Frank

    2005-03-01

    Stereotactic radiosurgery with several static conformal beams shaped by a micro multileaf collimator (microMLC) is used to treat small irregularly shaped brain lesions. Our goal is to perform Monte Carlo calculations of dose distributions for certain treatment plans as a verification tool. A dedicated microMLC component module for the BEAMnrc code was developed as part of this project and was incorporated in a model of the Varian CL2300 linear accelerator 6 MV photon beam. As an initial validation of the code, the leaf geometry was visualized by tracing particles through the component module and recording their position each time a leaf boundary was crossed. The leaf dimensions were measured and the leaf material density and interleaf air gap were chosen to match the simulated leaf leakage profiles with film measurements in a solid water phantom. A comparison between Monte Carlo calculations and measurements (diode, radiographic film) was performed for square and irregularly shaped fields incident on flat and homogeneous water phantoms. Results show that Monte Carlo calculations agree with measured dose distributions to within 2% and/or 1 mm except for field size smaller than 1.2 cm diameter where agreement is within 5% due to uncertainties in measured output factors. PMID:15798255

  3. Assessment of MLC tracking performance during hypofractionated prostate radiotherapy using real-time dose reconstruction

    NASA Astrophysics Data System (ADS)

    Fast, M. F.; Kamerling, C. P.; Ziegenhein, P.; Menten, M. J.; Bedford, J. L.; Nill, S.; Oelfke, U.

    2016-02-01

    By adapting to the actual patient anatomy during treatment, tracked multi-leaf collimator (MLC) treatment deliveries offer an opportunity for margin reduction and healthy tissue sparing. This is assumed to be especially relevant for hypofractionated protocols in which intrafractional motion does not easily average out. In order to confidently deliver tracked treatments with potentially reduced margins, it is necessary to monitor not only the patient anatomy but also the actually delivered dose during irradiation. In this study, we present a novel real-time online dose reconstruction tool which calculates actually delivered dose based on pre-calculated dose influence data in less than 10 ms at a rate of 25 Hz. Using this tool we investigate the impact of clinical target volume (CTV) to planning target volume (PTV) margins on CTV coverage and organ-at-risk dose. On our research linear accelerator, a set of four different CTV-to-PTV margins were tested for three patient cases subject to four different motion conditions. Based on this data, we can conclude that tracking eliminates dose cold spots which can occur in the CTV during conventional deliveries even for the smallest CTV-to-PTV margin of 1 mm. Changes of organ-at-risk dose do occur frequently during MLC tracking and are not negligible in some cases. Intrafractional dose reconstruction is expected to become an important element in any attempt of re-planning the treatment plan during the delivery based on the observed anatomy of the day.

  4. In vitro study of cell survival following dynamic MLC intensity-modulated radiation therapy dose delivery

    SciTech Connect

    Moiseenko, Vitali; Duzenli, Cheryl; Durand, Ralph E.

    2007-04-15

    The possibility of reduced cell kill following intensity-modulated radiation therapy (IMRT) compared to conventional radiation therapy has been debated in the literature. This potential reduction in cell kill relates to prolonged treatment times typical of IMRT dose delivery and consequently increased repair of sublethal lesions. While there is some theoretical support to this reduction in cell kill published in the literature, direct experimental evidence specific to IMRT dose delivery patterns is lacking. In this study we present cell survival data for three cell lines: Chinese hamster V79 fibroblasts, human cervical carcinoma, SiHa and colon adenocarcinoma, WiDr. Cell survival was obtained for 2.1 Gy delivered as acute dose with parallel-opposed pair (POP), irradiation time 75 s, which served as a reference; regular seven-field IMRT, irradiation time 5 min; and IMRT with a break for multiple leaf collimator (MLC) re-initialization after three fields were delivered, irradiation time 10 min. An actual seven-field dynamic MLC IMRT plan for a head and neck patient was used. The IMRT plan was generated for a Varian EX or iX linear accelerator with 120 leaf Millenium MLC. Survival data were also collected for doses 1x, 2x, 3x, 4x, and 5x 2.1 Gy to establish parameters of the linear-quadratic equation describing survival following acute dose delivery. Cells were irradiated inside an acrylic cylindrical phantom specifically designed for this study. Doses from both IMRT and POP were validated using ion chamber measurements. A reproducible increase in cell survival was observed following IMRT dose delivery. This increase varied from small for V79, with a surviving fraction of 0.8326 following POP vs 0.8420 following uninterrupted IMRT, to very pronounced for SiHa, with a surviving fraction of 0.3903 following POP vs 0.5330 for uninterrupted IMRT. When compared to IMRT or IMRT with a break for MLC initialization, cell survival following acute dose delivery was

  5. Biological consequences of MLC calibration errors in IMRT delivery and QA

    SciTech Connect

    Moiseenko, Vitali; LaPointe, Vincent; James, Kerry; Yin Lingshu; Liu, Mitchell; Pawlicki, Todd

    2012-04-15

    Purpose: The purpose of this work is threefold: (1) to explore biological consequences of the multileaf collimator (MLC) calibration errors in intensity modulated radiotherapy (IMRT) of prostate and head and neck cancers, (2) to determine levels of planning target volume (PTV) and normal tissue under- or overdose flagged with clinically used QA action limits, and (3) to provide biologically based input for MLC QA and IMRT QA action limits. Methods: Ten consecutive prostate IMRT cases and ten consecutive head and neck IMRT cases were used. Systematic MLC offsets (i.e., calibration error) were introduced for each control point of the plan separately for X1 and X2 leaf banks. Offsets were from - 2 to 2 mm with a 0.5 mm increment. The modified files were imported into the planning system for forward dose recalculation. The original plan served as the reference. The generalized equivalent uniform dose (gEUD) was used as the biological index for the targets, rectum, parotid glands, brainstem, and spinal cord. Each plan was recalculated on a CT scan of a 27 cm diameter cylindrical phantom with a contoured 0.6 cc ion chamber. Dose to ion chamber and 3D gamma analysis were compared to the reference plan. QA pass criteria: (1) at least 95% of voxels with a dose cutoff of 50% of maximum dose have to pass at 3 mm/3% and (2) dose to chamber within 2% of the reference dose. Results: For prostate cases, differences in PTV and rectum gEUD greater than 2% were identified. However, a larger proportion of plans leading to greater than 2% difference in prostate PTV gEUD passed the ion chamber QA but not 3D gamma QA. A similar trend was found for the rectum gEUD. For head and neck IMRT, the QA pass criteria flagged plans leading to greater than 4% differences in PTV gEUD and greater than 5% differences in the maximum dose to brainstem. If pass criteria were relaxed to 90% for gamma and 3% for ion chamber QA, plans leading to a 5% difference in PTV gEUD and a 5%-8% difference in

  6. ARIZONA INDIAN RESERVATIONS

    EPA Science Inventory

    Polygon coverage of all Indian Reservations in Arizona. Reservation boundaries are compiled from multiple sources and are derived from several different source scales. Information such as reservation type, primary tribe name and location source are included with the coverage. A...

  7. REGION 9 INDIAN RESERVATIONS

    EPA Science Inventory

    Polygon coverage of all Indian Reservations in US EPA Region 9 (California, Arizona and Nevada). Reservation boundaries are compiled from multiple sources and are derived from several different source scales. Information such as reservation type, primary tribe name and location...

  8. NEVADA INDIAN RESERVATIONS

    EPA Science Inventory

    Polygon coverage of all Indian Reservations in Nevada. Reservation boundaries are compiled from multiple sources and are derived from several different source scales. Information such as reservation type, primary tribe name and location source are included with the coverage. As...

  9. Reserve battery

    SciTech Connect

    Thiess, G.H.

    1988-12-27

    A reserve battery is described comprising: a battery cell compartment; an electrolyte reservoir containing pressurized electrolyte fluid; an elongate member formed of rigid material having interior walls defining a closed orifice between the battery cell compartment and the electrolyte fluid reservoir; and the elongate member including a groove adjacent the orifice to define a frangible portion such that upon angular displacement of the elongate member the elongate member is severed at the frangible portion to open the orifice and allow pressurized electrolyte fluid to be conveyed through the orifice to the battery cell compartment.

  10. Commitment to Study as a Technique to Improve Exam Performance.

    ERIC Educational Resources Information Center

    Leeming, Frank C.

    1997-01-01

    Reports on a technique that could increase study time by reducing procrastination. Randomly selected college students (N=197) made written commitments to study for an exam. Students in the commitment condition reported significantly more study time than did students in a control group; they also performed significantly better on the exam. (RJM)

  11. An Expanded Framework for Analyzing General Chemistry Exams

    ERIC Educational Resources Information Center

    Smith, K. Christopher; Nakhleh, Mary B.; Bretz, Stacey Lowery

    2010-01-01

    This paper describes an expanded framework to aid chemical educators in constructing exams for their courses. The framework has three primary levels: definition, algorithmic, and conceptual. These primary levels have often been used in chemical education research to analyze and describe exam questions, but in this study the definition,…

  12. Gender Differences in STEM Related Advanced Placement Exams

    ERIC Educational Resources Information Center

    Morris, Jill B.

    2013-01-01

    Purpose: The purpose of this study was to examine differences between boys and girls in their performance on STEM related AP exams. Specifically, gender differences were examined for the following STEM related AP exams: Calculus AB, Calculus BC, Physics B, Physics C: Electricity and Magnetism, Physics C: Mechanics, Chemistry, and Computer Science…

  13. The Red Effect, Anxiety, and Exam Performance: A Multistudy Examination

    ERIC Educational Resources Information Center

    Smajic, Adnan; Merritt, Stephanie; Banister, Christina; Blinebry, Amanda

    2014-01-01

    Laboratory studies have established a negative relationship between the color red and academic performance. This research examined whether this effect would generalize to classroom performance and whether anxiety and negative affect might mediate the effect. In two studies, students taking classroom exams were randomly assigned an exam color. We…

  14. Preparing Students to Take SOA/CAS Exam FM/2

    ERIC Educational Resources Information Center

    Marchand, Richard J.

    2014-01-01

    This paper provides suggestions for preparing students to take the actuarial examination on financial mathematics, SOA/CAS Exam FM/2. It is based on current practices employed at Slippery Rock University, a small public liberal arts university. Detailed descriptions of our Theory of Interest course and subsequent Exam FM/2 prep course are provided…

  15. Problematizing High School Certificate Exam in Pakistan: A Washback Perspective

    ERIC Educational Resources Information Center

    Jilani, Raana

    2009-01-01

    This paper describes and evaluates the Higher-Secondary School Certificate (HSC) exam in Pakistan that has been in place in its present form for more than thirty years. The author recounts her experience as a teacher of English in a representative high school in Pakistan and, reflecting on the impact of high school public exam, she argues that the…

  16. Prior-to-Exam: What Activities Enhance Performance?

    ERIC Educational Resources Information Center

    Rhoads, C. J.; Healy, Therese

    2013-01-01

    Can instructors impact their student performance by recommending an activity just prior to taking an exam? In this study, college students were randomly assigned to one of three treatment groups (study, exercise, or meditation) or a control group. Each group was given two different types of tests; a traditional concept exam, and a non-traditional…

  17. EXPOSURE ANALYSIS MODELING SYSTEM (EXAMS): USER MANUAL AND SYSTEM DOCUMENTATION

    EPA Science Inventory

    The Exposure Analysis Modeling System (EXAMS) was designed for rapid evaluation of the behavior of synthetic organic chemicals in aquatic ecosystems. From the chemistry of a compound and the relevant transport and physical/chemical characteristics of the ecosystem, EXAMS computes...

  18. High School Exit Exams and "Mis"measurement

    ERIC Educational Resources Information Center

    Tienken, Christopher H.

    2011-01-01

    Test score validity takes center stage in the debate over the use of high school exit exams. Scant literature addresses the amount of conditional standard error of measurement (CSEM) present in individual student results on high school exit exams. The purpose of this study is to fill a void in the literature and add a national review of the CSEM,…

  19. Should I Give the Exam before or after the Break?

    ERIC Educational Resources Information Center

    O'Connor, Kevin J.

    2014-01-01

    This study was designed to help faculty make decisions about when to administer an exam in relation to an in-semester break. Students in multiple sections of an undergraduate educational psychology class were assigned to take an exam either before or after a scheduled 5-day break (Thursday-Monday). A multiple regression analysis revealed the break…

  20. A Laboratory Practical Exam for High School Chemistry

    ERIC Educational Resources Information Center

    Rhodes, Michelle M.

    2010-01-01

    A station-based laboratory practical exam for first-year high school chemistry students is described. Students move individually through six stations meant to authentically assess both basic lab skills and problem-solving skills utilized throughout the year. The exam can be completed in an approximately 85 min lab period and can be easily adapted…

  1. Approaches to Studying and Academic Performance in Short Essay Exams

    ERIC Educational Resources Information Center

    Minbashian, Amirali; Huon, Gail F.; Bird, Kevin D.

    2004-01-01

    Previous research has generally failed to find a relation between the way students approach the task of studying and their exam grades. The present study investigated why it is that a deep approach to studying, which has been shown to result in a higher quality of learning, does not consistently result in higher exam grades. The participants in…

  2. Crib Sheets and Exam Performance in a Data Structures Course

    ERIC Educational Resources Information Center

    Hamouda, Sally; Shaffer, Clifford A.

    2016-01-01

    In this paper, we study the relationship between the use of "crib sheets" or "cheat sheets" and performance on in-class exams. Our extensive survey of the existing literature shows that it is not decisive on the questions of when or whether crib sheets actually help students to either perform better on an exam or better learn…

  3. Relationships between preclinical course grades and standardized exam performance.

    PubMed

    Hu, Yinin; Martindale, James R; LeGallo, Robin D; White, Casey B; McGahren, Eugene D; Schroen, Anneke T

    2016-05-01

    Success in residency matching is largely contingent upon standardized exam scores. Identifying predictors of standardized exam performance could promote primary intervention and lead to design insights for preclinical courses. We hypothesized that clinically relevant courses with an emphasis on higher-order cognitive understanding are most strongly associated with performance on United States Medical Licensing Examination Step exams and National Board of Medical Examiners clinical subject exams. Academic data from students between 2007 and 2012 were collected. Preclinical course scores and standardized exam scores were used for statistical modeling with multiple linear regression. Preclinical courses were categorized as having either a basic science or a clinical knowledge focus. Medical College Admissions Test scores were included as an additional predictive variable. The study sample comprised 795 graduating medical students. Median score on Step 1 was 234 (interquartile range 219-245.5), and 10.2 % (81/795) scored lower than one standard deviation below the national average (205). Pathology course score was the strongest predictor of performance on all clinical subject exams and Step exams, outperforming the Medical College Admissions Test in strength of association. Using Pathology score <75 as a screening metric for Step 1 score <205 results in sensitivity and specificity of 37 and 97 %, respectively, and a likelihood ratio of 11.9. Performance in Pathology, a clinically relevant course with case-based learning, is significantly related to subsequent performance on standardized exams. Multiple linear regression is useful for identifying courses that have potential as risk stratifiers. PMID:26363626

  4. Relationships between Preclinical Course Grades and Standardized Exam Performance

    ERIC Educational Resources Information Center

    Hu, Yinin; Martindale, James R.; LeGallo, Robin D.; White, Casey B.; McGahren, Eugene D.; Schroen, Anneke T.

    2016-01-01

    Success in residency matching is largely contingent upon standardized exam scores. Identifying predictors of standardized exam performance could promote primary intervention and lead to design insights for preclinical courses. We hypothesized that clinically relevant courses with an emphasis on higher-order cognitive understanding are most…

  5. Writing about testing worries boosts exam performance in the classroom.

    PubMed

    Ramirez, Gerardo; Beilock, Sian L

    2011-01-14

    Two laboratory and two randomized field experiments tested a psychological intervention designed to improve students' scores on high-stakes exams and to increase our understanding of why pressure-filled exam situations undermine some students' performance. We expected that sitting for an important exam leads to worries about the situation and its consequences that undermine test performance. We tested whether having students write down their thoughts about an upcoming test could improve test performance. The intervention, a brief expressive writing assignment that occurred immediately before taking an important test, significantly improved students' exam scores, especially for students habitually anxious about test taking. Simply writing about one's worries before a high-stakes exam can boost test scores. PMID:21233387

  6. Cognitive Difficulty and Format of Exams Predicts Gender and Socioeconomic Gaps in Exam Performance of Students in Introductory Biology Courses

    PubMed Central

    Wright, Christian D.; Eddy, Sarah L.; Wenderoth, Mary Pat; Abshire, Elizabeth; Blankenbiller, Margaret; Brownell, Sara E.

    2016-01-01

    Recent reform efforts in undergraduate biology have recommended transforming course exams to test at more cognitively challenging levels, which may mean including more cognitively challenging and more constructed-response questions on assessments. However, changing the characteristics of exams could result in bias against historically underserved groups. In this study, we examined whether and to what extent the characteristics of instructor-generated tests impact the exam performance of male and female and middle/high- and low-socioeconomic status (SES) students enrolled in introductory biology courses. We collected exam scores for 4810 students from 87 unique exams taken across 3 yr of the introductory biology series at a large research university. We determined the median Bloom’s level and the percentage of constructed-response questions for each exam. Despite controlling for prior academic ability in our models, we found that males and middle/high-SES students were disproportionately favored as the Bloom’s level of exams increased. Additionally, middle/high-SES students were favored as the proportion of constructed-response questions on exams increased. Given that we controlled for prior academic ability, our findings do not likely reflect differences in academic ability level. We discuss possible explanations for our findings and how they might impact how we assess our students. PMID:27252299

  7. Comparability of Semester and Exit Exam Grades: Long-Term Effect of the Implementation of State-Wide Exit Exams

    ERIC Educational Resources Information Center

    Maag Merki, Katharina; Holmeier, Monika

    2015-01-01

    A goal in many countries is to institute state-wide exams to base student assessment more firmly on norms for all classes. This raises the question as to the extent to which greater standardization of grading practice can be reached by implementing state-wide exit exams. Since there is a lack of longitudinal studies, we analyzed the effect of the…

  8. The Impact of Statewide Exit Exams: A Descriptive Case Study of Three German States with Differing Low Stakes Exam Regimes

    ERIC Educational Resources Information Center

    van Ackeren, Isabell; Block, Rainer; Klein, E. Dominique; Kuhn, Svenja M.

    2012-01-01

    In this article we present results from a study investigating the impact of three state exit exam systems on teaching and learning in college-preparatory schools. The study compares one state with a traditionally more centralized exam regime, one state that is more de-centralized and one state that has recently switched to more centralized…

  9. Cognitive Difficulty and Format of Exams Predicts Gender and Socioeconomic Gaps in Exam Performance of Students in Introductory Biology Courses

    ERIC Educational Resources Information Center

    Wright, Christian D.; Eddy, Sarah L.; Wenderoth, Mary Pat; Abshire, Elizabeth; Blankenbiller, Margaret; Brownell, Sara E.

    2016-01-01

    Recent reform efforts in undergraduate biology have recommended transforming course exams to test at more cognitively challenging levels, which may mean including more cognitively challenging and more constructed-response questions on assessments. However, changing the characteristics of exams could result in bias against historically underserved…

  10. Cognitive Difficulty and Format of Exams Predicts Gender and Socioeconomic Gaps in Exam Performance of Students in Introductory Biology Courses.

    PubMed

    Wright, Christian D; Eddy, Sarah L; Wenderoth, Mary Pat; Abshire, Elizabeth; Blankenbiller, Margaret; Brownell, Sara E

    2016-01-01

    Recent reform efforts in undergraduate biology have recommended transforming course exams to test at more cognitively challenging levels, which may mean including more cognitively challenging and more constructed-response questions on assessments. However, changing the characteristics of exams could result in bias against historically underserved groups. In this study, we examined whether and to what extent the characteristics of instructor-generated tests impact the exam performance of male and female and middle/high- and low-socioeconomic status (SES) students enrolled in introductory biology courses. We collected exam scores for 4810 students from 87 unique exams taken across 3 yr of the introductory biology series at a large research university. We determined the median Bloom's level and the percentage of constructed-response questions for each exam. Despite controlling for prior academic ability in our models, we found that males and middle/high-SES students were disproportionately favored as the Bloom's level of exams increased. Additionally, middle/high-SES students were favored as the proportion of constructed-response questions on exams increased. Given that we controlled for prior academic ability, our findings do not likely reflect differences in academic ability level. We discuss possible explanations for our findings and how they might impact how we assess our students. PMID:27252299

  11. 76 FR 4375 - In the Matter of Certain MLC Flash Memory Devices and Products Containing Same; Notice of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-25

    ...''). 74 FR 43723-4 (August 27, 2009). The complaint, as amended and supplemented, alleges violations of... COMMISSION In the Matter of Certain MLC Flash Memory Devices and Products Containing Same; Notice of... flash memory devices and products containing same by reason of infringement of certain claims of...

  12. SU-E-T-613: Dosimetric Consequences of Systematic MLC Leaf Positioning Errors

    SciTech Connect

    Kathuria, K; Siebers, J

    2014-06-01

    Purpose: The purpose of this study is to determine the dosimetric consequences of systematic MLC leaf positioning errors for clinical IMRT patient plans so as to establish detection tolerances for quality assurance programs. Materials and Methods: Dosimetric consequences were simulated by extracting mlc delivery instructions from the TPS, altering the file by the specified error, reloading the delivery instructions into the TPS, recomputing dose, and extracting dose-volume metrics for one head-andneck and one prostate patient. Machine error was simulated by offsetting MLC leaves in Pinnacle in a systematic way. Three different algorithms were followed for these systematic offsets, and are as follows: a systematic sequential one-leaf offset (one leaf offset in one segment per beam), a systematic uniform one-leaf offset (same one leaf offset per segment per beam) and a systematic offset of a given number of leaves picked uniformly at random from a given number of segments (5 out of 10 total). Dose to the PTV and normal tissue was simulated. Results: A systematic 5 mm offset of 1 leaf for all delivery segments of all beams resulted in a maximum PTV D98 deviation of 1%. Results showed very low dose error in all reasonably possible machine configurations, rare or otherwise, which could be simulated. Very low error in dose to PTV and OARs was shown in all possible cases of one leaf per beam per segment being offset (<1%), or that of only one leaf per beam being offset (<.2%). The errors resulting from a high number of adjacent leaves (maximum of 5 out of 60 total leaf-pairs) being simultaneously offset in many (5) of the control points (total 10–18 in all beams) per beam, in both the PTV and the OARs analyzed, were similarly low (<2–3%). Conclusions: The above results show that patient shifts and anatomical changes are the main source of errors in dose delivered, not machine delivery. These two sources of error are “visually complementary” and uncorrelated

  13. SU-E-T-633: Dose Differences in Lung Cancer SBRT: The Influences of MLC Width

    SciTech Connect

    Chen, J; Yin, Y

    2014-06-15

    Purpose: The aim is to compare the plan dose distribution of lung SBRT with MLCs in different width. Methods: Cases with phase INSCLC were enrolled. 9 cases were undergone 4D-CT scanning in the supine position with both arms raised. 3D-CT images without IV contrast were afterwards acquired with 3mm thickness and used for dose calculations. ITV was generated by using the inspiration and expiration images. The ITV can be expanded by geometric set-up uncertainty (5 mm) to generate the PTV. All chest normal tissues including chest wall were contoured by doctors. A total dose of 55 Gy will be given in 5 fractions within 10–14 days with an inter fraction interval of 2–3 days. Guided by the RTOG trial 3502 protocol, 11–13 non-coplanar fields with 6MV photon were arranged. Three types of MLCs with width of 3mm, 5mm and 10mm at isocenter position, were used separately to generate a CRT plan for each case. Monte Carlo algorithm was applied to dose calculation. All plans were adjusted as possible to meet the dose constraints. Dose-volume parameters from plans as followed were compared and analysized: PTV V55Gy, COMPTV D70% (70% of normalization dose), volume A (body minus PTV), and R100% and R50% (the ratio of x% of prescription dose isoline volume to PTV volume). Results: MLCs, 3mm and 5mm wide, played the identical roles on dosimetry of the plans, excluding the parameter volume A (p<0.05). On the contrary, MLC with width of 10mm was significantly inferior to the other two types on most parameters (p<0.05). For R50%, all types contributed equally (p>0.05). Conclusion: For lung cancer SBRT, MLC width had influence to dosimetry, especially in irradiation area. Small size MLC, e.g. 3mm and 5mm, are helpful to generate a high quality treatment plan, which could meet the strict criteria for targets and OAR.

  14. Theoretical and experimental validation of treatment planning for narrow MLC defined photon fields.

    PubMed

    Lydon, J M

    2005-06-01

    In intensity modulated radiotherapy (IMRT), the use of small fields where electronic equilibrium does not exist is becoming more common and presents difficulties for both the measurement and calculation of dose to such fields. Pinnacle(3) (Version 6.2b) allows the user to specify a total minimum open area for each IMRT segment, which can result in sub-segments with widths of only a few millimetres. The dose for 6 MV narrow MLC defined fields between 0.1 and 3 cm in width was investigated using Kodak extended dose range film (EDR2), ionization chamber and MOSFET dosimeters and BEAMnrc Monte Carlo calculations, and these results were used to determine the accuracy of Pinnacle(3) dose calculation for narrow MLC segments. The incident fluences calculated by Pinnacle(3) and BEAMnrc were also compared. Results show that if a fluence and dose grid resolution of 0.1 cm is used, Pinnacle(3) dose agrees with the EDR2 and BEAMnrc to within 5% for field widths between 0.5 and 3.0 cm. However, Pinnacle(3) will underestimate the dose by up to 45% for the 0.1 and 0.3 cm wide fields. It is shown that the source size in the Pinnacle(3) beam model and both the fluence and dose grid resolutions have a significant effect on the accuracy of dose calculation for field widths of 1.0 cm and less. For single segment fields, Pinnacle(3) agrees with EDR2 and BEAMnrc to within 0.1 cm at the field edges and underestimates the penumbra width by up to 0.08 cm. Results for multiple segment fields showed that an MLC transmission of 1.7% and a 0.06 cm inward shift of MLCs prior to beam delivery gave the closest agreement between Pinnacle(3) and measurement. The multiple segment fields also revealed a pattern of low dose troughs of up to 7% in the Pinnacle(3) dose profiles. PMID:15901964

  15. SU-E-T-425: Spherical Dose Distributions for Radiosurgery Using a Standardized MLC Plan

    SciTech Connect

    Popple, R; Brezovich, I; Wu, X; Fiveash, J

    2014-06-01

    Purpose: To investigate a standardized MLC treatment plan to generate small spherical dose distributions. Methods: The static virtual cone plan comprised six table positions with clockwise and counterclockwise arcs having collimator angles 45 and 135 degrees, respectively, at each position. The central two leaves of a 2.5 mm leaf width MLC were set to a constant gap. Control points were weighted proportional to the sine of the gantry angle. Plans were created for the 10 MV flattening-filter-free beam of a TrueBeam STx (Varian Medical Systems) with gaps of 1, 1.5, 2, and 3 mm and were delivered to a phantom containing radiochromic film. Dose was calculated using the Eclipse AAA (Varian Medical Systems). A dynamic plan in which the table and gantry moved simultaneously with 1.5 mm gap was also created and delivered using the TrueBeam developer mode. Results: The full-width-half-max (FWHM) varied with leaf gap, ranging from 5.2 to 6.2 mm. Calculated FWHM was smaller than measured by 0.7 mm for the 1 mm gap and ≤ 0.4 mm for the larger gaps. The measured-to-calculated dose ratio was 0.93, 0.96, 1.01, and 0.99 for 1 mm, 1.5 mm, 2 mm, and 3 mm gaps, respectively. The dynamic results were the same as the static. The position deviations between the phantom target position and the center of the dose distribution were < 0.4 mm. Conclusion: The virtual cone can deliver spherical dose distributions suitable for radio surgery of small targets such as the trigeminal nerve. The Eclipse AAA accurately calculates the expected dose, particularly for leaf gap ≥ 1.5 mm. The measured dose distribution is slightly larger than the calculation, which is likely due to systematic leaf position error, isocenter variation due to gantry sag and table eccentricity, and inaccuracy in MLC leaf end modeling.

  16. Matching marine reserve design to reserve objectives.

    PubMed Central

    Halpern, Benjamin S; Warner, Robert R

    2003-01-01

    Recent interest in using marine reserves for marine resource management and conservation has largely been driven by the hope that reserves might counteract declines in fish populations and protect the biodiversity of the seas. However, the creation of reserves has led to dissension from some interested groups, such as fishermen, who fear that reserves will do more harm than good. These perceived differences in the effect of marine reserves on various stakeholder interests has led to a contentious debate over their merit. We argue here that recent findings in marine ecology suggest that this debate is largely unnecessary, and that a single general design of a network of reserves of moderate size and variable spacing can meet the needs and goals of most stakeholders interested in marine resources. Given the high fecundity of most marine organisms and recent evidence for limited distance of larval dispersal, it is likely that reserves can both maintain their own biodiversity and service nearby non-reserve areas. In particular, spillover of larger organisms and dispersal of larvae to areas outside reserves can lead to reserves sustaining or even increasing local fisheries. Ultimately, the success of any reserve network requires attention to the uncertainty and variability in dispersal patterns of marine organisms, clear statements of goals by all stakeholder groups and proper evaluation of reserve performance. PMID:14561299

  17. Evaluation of dosimetric effect caused by slowing with multi-leaf collimator (MLC) leaves for volumetric modulated arc therapy (VMAT)

    PubMed Central

    Wang, Iris Z.; Kumaraswamy, Lalith K.; Podgorsak, Matthew B.

    2016-01-01

    Background This study is to report 1) the sensitivity of intensity modulated radiation therapy (IMRT) QA method for clinical volumetric modulated arc therapy (VMAT) plans with multi-leaf collimator (MLC) leaf errors that will not trigger MLC interlock during beam delivery; 2) the effect of non-beam-hold MLC leaf errors on the quality of VMAT plan dose delivery. Materials and methods. Eleven VMAT plans were selected and modified using an in-house developed software. For each control point of a VMAT arc, MLC leaves with the highest speed (1.87-1.95 cm/s) were set to move at the maximal allowable speed (2.3 cm/s), which resulted in a leaf position difference of less than 2 mm. The modified plans were considered as ‘standard’ plans, and the original plans were treated as the ‘slowing MLC’ plans for simulating ‘standard’ plans with leaves moving at relatively lower speed. The measurement of each ‘slowing MLC’ plan using MapCHECK®2 was compared with calculated planar dose of the ‘standard’ plan with respect to absolute dose Van Dyk distance-to-agreement (DTA) comparisons using 3%/3 mm and 2%/2 mm criteria. Results All ‘slowing MLC’ plans passed the 90% pass rate threshold using 3%/3 mm criteria while one brain and three anal VMAT cases were below 90% with 2%/2 mm criteria. For ten out of eleven cases, DVH comparisons between ‘standard’ and ‘slowing MLC’ plans demonstrated minimal dosimetric changes in targets and organs-at-risk. Conclusions For highly modulated VMAT plans, pass rate threshold (90%) using 3%/3mm criteria is not sensitive in detecting MLC leaf errors that will not trigger the MLC leaf interlock. However, the consequential effects of non-beam hold MLC errors on target and OAR doses are negligible, which supports the reliability of current patient-specific IMRT quality assurance (QA) method for VMAT plans. PMID:27069458

  18. SU-E-T-122: Dosimetric Comparison Between Cone, HDMLC and MicroMLC for the Treatment of Trigeminal Neuralgia

    SciTech Connect

    Vacca, N; Caussa, L; Filipuzzi, M; Garrigo, E; Venencia, C

    2014-06-01

    Purpose: The purpose of this work was to evaluate the dosimetric characteristics of three collimation systems, 5mm circular cone (Brainlab) and square fields of 5mm with HDMLC (Varian) and microMLC Moduleaf, Siemens) for trigeminal neuralgia treatment. Methods: A TPS Iplan v4.5 BrainLAB was used to do treatment plans for each collimations system in a square solid water phantom with isocenter at 5cm depth. Single field and treatment plan including 11 arcs with fix field and 100° gantry range was made for each collimation systems. EBT3 films were positioned at isocenter in a coronal plane to measured dose distribution for all geometries. Films were digitized with a Vidar DosimetryPro Red scanner with a resolution of 89dpi and RIT113v6.1 software was used for analysis. Penumbra region (80%–20%), FWHM and dose percentage at 5mm and 10mm from CAX were determined. All profiles were normalized at CAX. Results: For single beam the penumbra (FWHM) was 1.5mm (5.3mm) for the cone, 1.9mm (5.5mm) for HDMLC and 1.8mm (5.4mm) for the microMLC. Dose percentage at 5mm was 6.9% for cone, 12.5% for HDMLC and 8.7% for the microMLC. For treatment plan the penumbra (FWHM) was 2.58mm (5.47mm) for the cone, 2.8mm (5.84mm) for HDMLC and 2.58mm (6.09mm) for the microMLC. Dose perecentage at 5mm was 13.1% for cone, 16.1% for HDMLC, 15.2% for the microMLC. Conclusion: The cone has a dose falloff larger than the microMLC and HDMLC, by its reduced penumbra, this translates into better protection of surrounding healthy tissue, however, the microMLC and HDMLC have similar accuracy to cone.

  19. High-Dose Spatially Fractionated GRID Radiation Therapy (SFGRT): A Comparison of Treatment Outcomes With Cerrobend vs. MLC SFGRT

    SciTech Connect

    Neuner, Geoffrey; Mohiuddin, Majid M.; Vander Walde, Noam; Goloubeva, Olga; Ha, Jonathan; Yu, Cedric X.; Regine, William F.

    2012-04-01

    Purpose: Spatially fractionated GRID radiotherapy (SFGRT) using a customized Cerrobend block has been used to improve response rates in patients with bulky tumors. The clinical efficacy of our own multileaf collimator (MLC) technique is unknown. We undertook a retrospective analysis to compare clinical response rates attained using these two techniques. Methods and Materials: Seventy-nine patients with bulky tumors (median diameter, 7.6 cm; range, 4-30 cm) treated with SFGRT were reviewed. Between 2003 and late 2005, the Cerrobend block technique (n = 39) was used. Between late 2005 and 2008, SFGRT was delivered using MLC-shaped fields (n = 40). Dose was prescribed to dmax (depth of maximum dose) and was typically 15 Gy. Eighty percent of patients in both groups received external beam radiotherapy in addition to SFGRT. The two-sided Fisher-Freeman-Halton test was used to compare pain and mass effect response rates between the two groups. Results: Sixty-one patients (77%) were treated for palliative intent and 18 (23%) for curative intent. The majority of patients had either lung or head-and-neck primaries in both groups; the most frequent site of SFGRT application was the neck. The majority of patients complained of either pain (65%) or mass effect (58%) at intake. Overall response rates for pain and mass response were no different between the Cerrobend and MLC groups: pain, 75% and 74%, respectively (p = 0.50), and mass effect, 67% and 73%, respectively (p = 0.85). The majority of toxicities were Grade 1 or 2, and only 3 patients had late Grade 3-4 toxicities. Conclusions: MLC-based and Cerrobend-based SFGRT have comparable and encouraging response rates when used either in the palliative or curative setting. MLC-based SGFRT should allow clinics to more easily adopt this novel treatment approach for the treatment of bulky tumors.

  20. Dosimetric evaluation of photon dose calculation under jaw and MLC shielding

    SciTech Connect

    Fogliata, A.; Clivio, A.; Vanetti, E.; Nicolini, G.; Belosi, M. F.; Cozzi, L.

    2013-10-15

    Purpose: The accuracy of photon dose calculation algorithms in out-of-field regions is often neglected, despite its importance for organs at risk and peripheral dose evaluation. The present work has assessed this for the anisotropic analytical algorithm (AAA) and the Acuros-XB algorithms implemented in the Eclipse treatment planning system. Specifically, the regions shielded by the jaw, or the MLC, or both MLC and jaw for flattened and unflattened beams have been studied.Methods: The accuracy in out-of-field dose under different conditions was studied for two different algorithms. Measured depth doses out of the field, for different field sizes and various distances from the beam edge were compared with the corresponding AAA and Acuros-XB calculations in water. Four volumetric modulated arc therapy plans (in the RapidArc form) were optimized in a water equivalent phantom, PTW Octavius, to obtain a region always shielded by the MLC (or MLC and jaw) during the delivery. Doses to different points located in the shielded region and in a target-like structure were measured with an ion chamber, and results were compared with the AAA and Acuros-XB calculations. Photon beams of 6 and 10 MV, flattened and unflattened were used for the tests.Results: Good agreement between calculated and measured depth doses was found using both algorithms for all points measured at depth greater than 3 cm. The mean dose differences (±1SD) were −8%± 16%, −3%± 15%, −16%± 18%, and −9%± 16% for measurements vs AAA calculations and −10%± 14%, −5%± 12%, −19%± 17%, and −13%± 14% for Acuros-XB, for 6X, 6 flattening-filter free (FFF), 10X, and 10FFF beams, respectively. The same figures for dose differences relative to the open beam central axis dose were: −0.1%± 0.3%, 0.0%± 0.4%, −0.3%± 0.3%, and −0.1%± 0.3% for AAA and −0.2%± 0.4%, −0.1%± 0.4%, −0.5%± 0.5%, and −0.3%± 0.4% for Acuros-XB. Buildup dose was overestimated with AAA, while Acuros-XB gave

  1. Beamlet based direct aperture optimization for MERT using a photon MLC

    SciTech Connect

    Henzen, D. Manser, P.; Frei, D.; Volken, W.; Born, E. J.; Joosten, A.; Lössl, K.; Aebersold, D. M.; Chatelain, C.; Fix, M. K.; Neuenschwander, H.; Stampanoni, M. F. M.

    2014-12-15

    Purpose: A beamlet based direct aperture optimization (DAO) for modulated electron radiotherapy (MERT) using photon multileaf collimator (pMLC) shaped electron fields is developed and investigated. Methods: The Swiss Monte Carlo Plan (SMCP) allows the calculation of dose distributions for pMLC shaped electron beams. SMCP is interfaced with the Eclipse TPS (Varian Medical Systems, Palo Alto, CA) which can thus be included into the inverse treatment planning process for MERT. This process starts with the import of a CT-scan into Eclipse, the contouring of the target and the organs at risk (OARs), and the choice of the initial electron beam directions. For each electron beam, the number of apertures, their energy, and initial shape are defined. Furthermore, the DAO requires dose–volume constraints for the structures contoured. In order to carry out the DAO efficiently, the initial electron beams are divided into a grid of beamlets. For each of those, the dose distribution is precalculated using a modified electron beam model, resulting in a dose list for each beamlet and energy. Then the DAO is carried out, leading to a set of optimal apertures and corresponding weights. These optimal apertures are now converted into pMLC shaped segments and the dose calculation for each segment is performed. For these dose distributions, a weight optimization process is launched in order to minimize the differences between the dose distribution using the optimal apertures and the pMLC segments. Finally, a deliverable dose distribution for the MERT plan is obtained and loaded back into Eclipse for evaluation. For an idealized water phantom geometry, a MERT treatment plan is created and compared to the plan obtained using a previously developed forward planning strategy. Further, MERT treatment plans for three clinical situations (breast, chest wall, and parotid metastasis of a squamous cell skin carcinoma) are created using the developed inverse planning strategy. The MERT plans are

  2. Performance analysis of exam gloves used for aseptic rodent surgery.

    PubMed

    LeMoine, Dana M; Bergdall, Valerie K; Freed, Carrie

    2015-05-01

    Aseptic technique includes the use of sterile surgical gloves for survival surgeries in rodents to minimize the incidence of infections. Exam gloves are much less expensive than are surgical gloves and may represent a cost-effective, readily available option for use in rodent surgery. This study examined the effectiveness of surface disinfection of exam gloves with 70% isopropyl alcohol or a solution of hydrogen peroxide and peracetic acid (HP-PA) in reducing bacterial contamination. Performance levels for asepsis were met when gloves were negative for bacterial contamination after surface disinfection and sham 'exertion' activity. According to these criteria, 94% of HP-PA-disinfected gloves passed, compared with 47% of alcohol-disinfected gloves. In addition, the effect of autoclaving on the integrity of exam gloves was examined, given that autoclaving is another readily available option for aseptic preparation. Performance criteria for glove integrity after autoclaving consisted of: the ability to don the gloves followed by successful simulation of wound closure and completion of stretch tests without tearing or observable defects. Using this criteria, 98% of autoclaved nitrile exam gloves and 76% of autoclaved latex exam gloves met performance expectations compared with the performance of standard surgical gloves (88% nitrile, 100% latex). The results of this study support the use of HP-PA-disinfected latex and nitrile exam gloves or autoclaved nitrile exam gloves as viable cost-effective alternatives to sterile surgical gloves for rodent surgeries. PMID:26045458

  3. Performance Analysis of Exam Gloves Used for Aseptic Rodent Surgery

    PubMed Central

    LeMoine, Dana M; Bergdall, Valerie K; Freed, Carrie

    2015-01-01

    Aseptic technique includes the use of sterile surgical gloves for survival surgeries in rodents to minimize the incidence of infections. Exam gloves are much less expensive than are surgical gloves and may represent a cost-effective, readily available option for use in rodent surgery. This study examined the effectiveness of surface disinfection of exam gloves with 70% isopropyl alcohol or a solution of hydrogen peroxide and peracetic acid (HP–PA) in reducing bacterial contamination. Performance levels for asepsis were met when gloves were negative for bacterial contamination after surface disinfection and sham ‘exertion’ activity. According to these criteria, 94% of HP–PA-disinfected gloves passed, compared with 47% of alcohol-disinfected gloves. In addition, the effect of autoclaving on the integrity of exam gloves was examined, given that autoclaving is another readily available option for aseptic preparation. Performance criteria for glove integrity after autoclaving consisted of: the ability to don the gloves followed by successful simulation of wound closure and completion of stretch tests without tearing or observable defects. Using this criteria, 98% of autoclaved nitrile exam gloves and 76% of autoclaved latex exam gloves met performance expectations compared with the performance of standard surgical gloves (88% nitrile, 100% latex). The results of this study support the use of HP–PA-disinfected latex and nitrile exam gloves or autoclaved nitrile exam gloves as viable cost-effective alternatives to sterile surgical gloves for rodent surgeries. PMID:26045458

  4. Evaluation of MLC leaf positioning accuracy for static and dynamic IMRT treatments using DAVID in vivo dosimetric system.

    PubMed

    Karagoz, Gulay; Zorlu, Faruk; Yeginer, Mete; Yildiz, Demet; Ozyigit, Gokhan

    2016-01-01

    Accuracy and precision of leaf positioning in multileaf collimators (MLCs) are significant factors for the accuracy of IMRT treatments. This study aimed to inves-tigate the accuracy and repeatability of the MLC leaf positioning via the DAVID invivo dosimetric system for dynamic and static MLC systems. The DAVID system was designed as multiwire transmission ionization chamber which is placed in accessory holder of linear accelerators. Each wire of DAVID system corresponds to a MLC leaf-pair to verify the leaf positioning accuracy during IMRT treatment and QA. In this study, verifications of IMRT plans of five head and neck (H&N) and five prostate patients treated in a Varian DHX linear accelerator with 80-leaf MLC were performed using DAVID system. Before DAVID-based dosimetry, Electronics Portal Imaging Device (EPID) and PTW 2D ARRAY dosimetry system were used for 2D verification of each plan. The measurements taken by DAVID system in the first day of the treatments were used as reference for the following measurements taken over the next four weeks. The deviations in leaf positioning were evaluated by "Total Deviation (TD)" parameter calculated by DAVID software. The delivered IMRT plans were originally prepared using dynamic MLC method. The same plans were subsequently calculated based on static MLC method with three different intensity levels of five (IL5), 10 (IL10) and 20 (IL20) in order to compare the performances of MLC leaf positioning repeatability for dynamic and static IMRT plans. The leaf positioning accuracy is also evaluated by analyzing DynaLog files based on error histograms and root mean square (RMS) errors of leaf pairs' positions. Moreover, a correlation analysis between simultaneously taken DAVID and EPID measurements and DynaLog file recordings was subsequently performed. In the analysis of DAVID outputs, the overall deviations of dynamic MLC-based IMRT calculated from the deviations of the four weeks were found as 0.55% ± 0.57% and 1.48% ± 0

  5. Assessment of MLC tracking performance during hypofractionated prostate radiotherapy using real-time dose reconstruction.

    PubMed

    Fast, M F; Kamerling, C P; Ziegenhein, P; Menten, M J; Bedford, J L; Nill, S; Oelfke, U

    2016-02-21

    By adapting to the actual patient anatomy during treatment, tracked multi-leaf collimator (MLC) treatment deliveries offer an opportunity for margin reduction and healthy tissue sparing. This is assumed to be especially relevant for hypofractionated protocols in which intrafractional motion does not easily average out. In order to confidently deliver tracked treatments with potentially reduced margins, it is necessary to monitor not only the patient anatomy but also the actually delivered dose during irradiation. In this study, we present a novel real-time online dose reconstruction tool which calculates actually delivered dose based on pre-calculated dose influence data in less than 10 ms at a rate of 25 Hz. Using this tool we investigate the impact of clinical target volume (CTV) to planning target volume (PTV) margins on CTV coverage and organ-at-risk dose. On our research linear accelerator, a set of four different CTV-to-PTV margins were tested for three patient cases subject to four different motion conditions. Based on this data, we can conclude that tracking eliminates dose cold spots which can occur in the CTV during conventional deliveries even for the smallest CTV-to-PTV margin of 1 mm. Changes of organ-at-risk dose do occur frequently during MLC tracking and are not negligible in some cases. Intrafractional dose reconstruction is expected to become an important element in any attempt of re-planning the treatment plan during the delivery based on the observed anatomy of the day. PMID:26816273

  6. FLEX: A Modular Software Architecture for Flight License Exam

    NASA Astrophysics Data System (ADS)

    Arsan, Taner; Saka, Hamit Emre; Sahin, Ceyhun

    This paper is about the design and implementation of an examination system based on World Wide Web. It is called FLEX-Flight License Exam Software. We designed and implemented flexible and modular software architecture. The implemented system has basic specifications such as appending questions in system, building exams with these appended questions and making students to take these exams. There are three different types of users with different authorizations. These are system administrator, operators and students. System administrator operates and maintains the system, and also audits the system integrity. The system administrator can not be able to change the result of exams and can not take an exam. Operator module includes instructors. Operators have some privileges such as preparing exams, entering questions, changing the existing questions and etc. Students can log on the system and can be accessed to exams by a certain URL. The other characteristic of our system is that operators and system administrator are not able to delete questions due to the security problems. Exam questions can be inserted on their topics and lectures in the database. Thus; operators and system administrator can easily choose questions. When all these are taken into consideration, FLEX software provides opportunities to many students to take exams at the same time in safe, reliable and user friendly conditions. It is also reliable examination system for the authorized aviation administration companies. Web development platform - LAMP; Linux, Apache web server, MySQL, Object-oriented scripting Language - PHP are used for developing the system and page structures are developed by Content Management System - CMS.

  7. Computer-aided training exam creation and personnel records management

    SciTech Connect

    Lawton, R.K.; Louche, K.A.

    1985-11-01

    A problem has existed in nuclear power plant training departments about how to choose questions for examinations without instructor bias, how to permanently store this exam so that it can be reconstructed, how to statistically analyze class, instructor, and student performance, and how to keep accurate, easily accessible records of all training. The design of the software package discussed in the paper is such that a complete record of classes, quizzes, exams, instructors, and analysis is available for each trainee. The need for classes is automatically available from the computer with randomly created exams available on request.

  8. Keep Your Vision Healthy: Learn About Comprehensive Dilated Eye Exams

    MedlinePlus

    ... please review our exit disclaimer . Subscribe Keep Your Vision Healthy Learn About Comprehensive Dilated Eye Exams People ... should have their eyesight tested to keep their vision at its best. Children usually have vision screening ...

  9. Preparticipation Exams: How To Detect a Teenage Crisis.

    PubMed

    Donahue, P

    1990-09-01

    Drug abuse, suicide, murder, accidents, and sexual problems are epidemic among teenagers. Sport-specific examinations do not address these adolescent risk factors, but the author tells how they can be uncovered in a preparticipation exam. PMID:27447584

  10. Do Weekly Quizzes Improve Student Performance on General Biology Exams?

    ERIC Educational Resources Information Center

    Haberyan, Kurt A.

    2003-01-01

    Evaluates the impact of quizzes on student performance among non-biology major freshmen. Administers weekly quizzes and compares with the control group who experience no quizzes. Reports no significant improvement in exam scores. (YDS)

  11. Routine Eye Exams See Vision Problems You Miss

    MedlinePlus

    ... news/fullstory_159863.html Routine Eye Exams See Vision Problems You Miss Older people and those who ... half of people with no new symptoms or vision problems receive new prescriptions or treatment changes as ...

  12. Verification of dosimetric accuracy on the TrueBeam STx: Rounded leaf effect of the high definition MLC

    SciTech Connect

    Kielar, Kayla N.; Mok, Ed; Hsu, Annie; Wang Lei; Luxton, Gary

    2012-10-15

    Purpose: The dosimetric leaf gap (DLG) in the Varian Eclipse treatment planning system is determined during commissioning and is used to model the effect of the rounded leaf-end of the multileaf collimator (MLC). This parameter attempts to model the physical difference between the radiation and light field and account for inherent leakage between leaf tips. With the increased use of single fraction high dose treatments requiring larger monitor units comes an enhanced concern in the accuracy of leakage calculations, as it accounts for much of the patient dose. This study serves to verify the dosimetric accuracy of the algorithm used to model the rounded leaf effect for the TrueBeam STx, and describes a methodology for determining best-practice parameter values, given the novel capabilities of the linear accelerator such as flattening filter free (FFF) treatments and a high definition MLC (HDMLC). Methods: During commissioning, the nominal MLC position was verified and the DLG parameter was determined using MLC-defined field sizes and moving gap tests, as is common in clinical testing. Treatment plans were created, and the DLG was optimized to achieve less than 1% difference between measured and calculated dose. The DLG value found was tested on treatment plans for all energies (6 MV, 10 MV, 15 MV, 6 MV FFF, 10 MV FFF) and modalities (3D conventional, IMRT, conformal arc, VMAT) available on the TrueBeam STx. Results: The DLG parameter found during the initial MLC testing did not match the leaf gap modeling parameter that provided the most accurate dose delivery in clinical treatment plans. Using the physical leaf gap size as the DLG for the HDMLC can lead to 5% differences in measured and calculated doses. Conclusions: Separate optimization of the DLG parameter using end-to-end tests must be performed to ensure dosimetric accuracy in the modeling of the rounded leaf ends for the Eclipse treatment planning system. The difference in leaf gap modeling versus physical

  13. Successful student remediation following repeated failures on the HESI exam.

    PubMed

    English, Jujuan B; Gordon, Debra K

    2006-01-01

    A problem-based remediation plan was developed and implemented to improve the clinical reasoning abilities and standardized test taking abilities of 9 students following 2 failures of the HESI exam. Prior to implementation students were assessed for learning needs, presence of anxiety, and learning styles. After completing the remediation sessions, all students successfully passes the HESI Exam with scores of 99.99. PMID:16913567

  14. Successful student remediation following repeated failures on the HESI exam.

    PubMed

    English, Jujuan B; Gordon, Debra K

    2004-01-01

    A problem-based remediation plan was developed and implemented to improve the clinical reasoning abilities and standardized test taking abilities of 9 students following 2 failures of the HESI exam. Prior to implementation students were assessed for learning needs, presence of anxiety, and learning styles. After completing the remediation sessions, all students successfully passed the HESI Exam with scores of 99.99. PMID:15586125

  15. Successful student remediation following repeated failures on the HESI Exam.

    PubMed

    English, Jujuan B; Gordon, Debra K

    2008-01-01

    A problem-based remediation plan was developed and implemented to improve the clinical reasoning abilities and standardized test taking abilities of 9 students following 2 failures of the HESI exam. Prior to implementation students were assessed for learning needs, presence of anxiety, and learning styles. After completing the remediation sessions, all students successfully passes the HESI Exam with scores of 99.99. PMID:18791396

  16. Reserve battery

    SciTech Connect

    Theiss, G.H.

    1990-05-15

    This patent describes a reserve battery. It comprises: a battery cell compartment defined by housing walls surrounding rounding battery cells and having an open top; a lower bulkhead member spanning the open top of the battery cell compartment and having fill tubes depending from a downwardly facing surface of the lower bulkhead member, one fill tube being provided for each of the battery cells, and each fill tube having internal walls defining a passageway between the interior of the battery cell compartment and an upwardly facing surface of the lower bulkhead member; an upper bulkhead member having a downwardly facing surface opposite and spaced apart from the upwardly facing surface of the lower bulkhead member to form a bulkhead cavity; an elastic reservoir bag in an expanded state containing an electrolyte fluid under pressure and having an opening connected to a passageway to the bulkhead cavity; operable means for sealing the passageway between the reservoir bag opening and the cavity; and housing walls defining a containment for the reservoir bag.

  17. Does Question Structure Affect Exam Performance in the Geosciences?

    NASA Astrophysics Data System (ADS)

    Day, E. A.; D'Arcy, M. K.; Craig, L.; Streule, M. J.; Passmore, E.; Irving, J. C. E.

    2015-12-01

    The jump to university level exams can be challenging for some students, often resulting in poor marks, which may be detrimental to their confidence and ultimately affect their overall degree class. Previous studies have found that question structure can have a strong impact on the performance of students in college level exams (see Gibson et al., 2015, for a discussion of its impact on physics undergraduates). Here, we investigate the effect of question structure on the exam results of geology and geophysics undergraduate students. Specifically, we analyse the performance of students in questions that have a 'scaffolded' framework and compare them to their performance in open-ended questions and coursework. We also investigate if observed differences in exam performance are correlated with the educational background and gender of students, amongst other factors. It is important for all students to be able to access their degree courses, no matter what their backgrounds may be. Broadening participation in the geosciences relies on removing systematic barriers to achievement. Therefore we recommend that exams are either structured with scaffolding in questions at lower levels, or students are explicitly prepared for this transition. We also recommend that longitudinal studies of exam performance are conducted within individual departments, and this work outlines one approach to analysing performance data.

  18. Crib sheets and exam performance in a data structures course

    NASA Astrophysics Data System (ADS)

    Hamouda, Sally; Shaffer, Clifford A.

    2016-01-01

    In this paper, we study the relationship between the use of "crib sheets" or "cheat sheets" and performance on in-class exams. Our extensive survey of the existing literature shows that it is not decisive on the questions of when or whether crib sheets actually help students to either perform better on an exam or better learn the material. We report on our own detailed analysis for a body of crib sheets created for the final exam in a junior-level Data Structures and Algorithms course. We wanted to determine whether there is any feature of the crib sheets that correlates to good exam scores. Exam performance was compared against a number of potential indicators for quality in a crib sheet. We have found that students performed significantly better on questions at the comprehension level of Bloom's taxonomy when their crib sheet contained good information on the topic, while performance on questions at higher levels of the taxonomy did not show correlation to crib sheet contents. We have also seen that students at certain levels of performance on the final exam (specifically, medium-to-high performance) did relatively better on certain questions than other students at that performance level when they had good coverage of that question's topic on their crib sheet.

  19. A Molecular Dynamics Study and Free Energy Analysis of Complexes between the Mlc1p Protein and Two IQ Motif Peptides

    PubMed Central

    Ganoth, Assaf; Friedman, Ran; Nachliel, Esther; Gutman, Menachem

    2006-01-01

    The Mlc1p protein from the budding yeast Saccharomyces cerevisiae is a Calmodulin-like protein, which interacts with IQ-motif peptides located at the yeast's myosin neck. In this study, we report a molecular dynamics study of the Mlc1p-IQ2 protein-peptide complex, starting with its crystal structure, and investigate its dynamics in an aqueous solution. The results are compared with those obtained by a previous study, where we followed the solution structure of the Mlc1p-IQ4 protein-peptide complex by molecular dynamics simulations. After the simulations, we performed an interaction free-energy analysis using the molecular mechanics Poisson-Boltzmann surface area approach. Based on the dynamics of the Mlc1p-IQ protein-peptide complexes, the structure of the light-chain-binding domain of myosin V from the yeast S. cerevisiae is discussed. PMID:16844751

  20. AFFORDABLE MULTI-LAYER CERAMIC (MLC) MANUFACTURING FOR POWER SYSTEMS (AMPS)

    SciTech Connect

    E.A. Barringer, Ph.D.

    2002-11-27

    McDermott Technology, Inc. (MTI) is attempting to develop high-performance, cost-competitive solid oxide fuel cell (SOFC) power systems. Recognizing the challenges and limitations facing the development of SOFC stacks comprised of electrode-supported cells and metallic interconnects, McDermott Technology, Inc. (MTI) has chosen to pursue an alternate path to commercialization. MTI is developing a multi-layer, co-fired, planar SOFC stack that will provide superior performance and reliability at reduced costs relative to competing designs. The MTI approach combines state-of-the-art SOFC materials with the manufacturing technology and infrastructure established for multi-layer ceramic (MLC) packages for the microelectronics industry. The rationale for using MLC packaging technology is that high quality, low-cost manufacturing has been demonstrated at high volumes. With the proper selection of SOFC materials, implementation of MLC fabrication methods offers unique designs for stacks (cells and interconnects) that are not possible through traditional fabrication methods. The MTI approach eliminates use of metal interconnects and ceramic-metal seals, which are primary sources of stack performance degradation. Co-fired cells are less susceptible to thermal cycling stresses by using material compositions that have closely matched coefficients of thermal expansion between the cell and the interconnect. The development of this SOFC stack technology was initiated in October 1999 under the DOE cosponsored program entitled ''Affordable Multi-layer Ceramic Manufacturing for Power Systems (AMPS)''. The AMPS Program was conducted as a two-phase program: Phase I--Feasibility Assessment (10/99--9/00); and Phase II--Process Development for Co-fired Stacks (10/00-3/02). This report provides a summary of the results from Phase I and a more detailed review of the results for Phase II. Phase I demonstrated the feasibility for fabricating multi-layer, co-fired cells and interconnects and

  1. Comparison of two Classification methods (MLC and SVM) to extract land use and land cover in Johor Malaysia

    NASA Astrophysics Data System (ADS)

    Rokni Deilmai, B.; Ahmad, B. Bin; Zabihi, H.

    2014-06-01

    Mapping is essential for the analysis of the land use and land cover, which influence many environmental processes and properties. For the purpose of the creation of land cover maps, it is important to minimize error. These errors will propagate into later analyses based on these land cover maps. The reliability of land cover maps derived from remotely sensed data depends on an accurate classification. In this study, we have analyzed multispectral data using two different classifiers including Maximum Likelihood Classifier (MLC) and Support Vector Machine (SVM). To pursue this aim, Landsat Thematic Mapper data and identical field-based training sample datasets in Johor Malaysia used for each classification method, which results indicate in five land cover classes forest, oil palm, urban area, water, rubber. Classification results indicate that SVM was more accurate than MLC. With demonstrated capability to produce reliable cover results, the SVM methods should be especially useful for land cover classification.

  2. The fish (IMRT) needs a bicycle (MLC)? The bicycle factories seem flourishing; not so the goldfish-bowl factories.

    PubMed

    Webb, S

    2011-07-01

    In this brief letter the arguments of Sherouse in 2002, that the delivery of intensity-modulated radiation therapy (IMRT) does not necessarily require a multileaf collimator (MLC), are extended with specific reference to the possibility to use the jaws-only (JO) of an accelerator or some moving mask. With reference to the work in the last decade to develop JO IMRT the argument is made that it is not just the limitations of JO that are precluding its commercial development but also the commercial/business and reimbursement situations. A new moving-mask-IMRT technique that has high monitor-unit (MU) efficiency, but low MU per component, is illustrated. The letter is intended to stimulate debate and is not a criticism by the author of current MLC-based IMRT. PMID:21292523

  3. SU-C-BRB-04: Characteristics and Performance Evaluation of the First Commercial MLC for a Robotic Delivery System

    SciTech Connect

    Fuerweger, C; Prins, P; Coskan, H; Heijmen, B

    2015-06-15

    Purpose: To assess characteristics and performance of the “Incise™” MLC (41 leaf pairs, 2.5mm width, FFF linac) mounted on the robotic SRS/SBRT platform “CyberKnife M6™” in a pre-clinical 5 months (11/2014–03/2015) test period. Methods: Beam properties were measured with unshielded diodes and EBT3 film. The CyberKnife workspace for MLC was analyzed by transforming robot node coordinates (cranial / body paths) into Euler geometry. Bayouth tests for leaf / bank position accuracy were performed in standard (A/P) and clinically relevant non-standard positions, before and after exercising the MLC for 10+ minutes. Total system and delivery accuracy were assessed in End-to-End tests and dosimetric verification of exemplary plans. Stability over time was evaluated in Picket-Fence-and adapted Winston-Lutz-tests (AQA) for different collimator angles. Results: Penumbrae (80–20%, with 100%=2*dose at inflection point; SAD 80cm; 10cm depth) parallel / perpendicular to leaf motion were 2.87/2.64mm for the smallest (0×76×0.75cm{sup 2}) and 5.34/4.94mm for the largest (9.76×9.75cm{sup 2}) square field. MLC circular field penumbrae exceeded fixed cones by 10–20% (e.g. 60mm: 4.0 vs. 3.6mm; 20mm: 3.6 vs. 2.9mm). Interleaf leakage was <0.5%. Clinically accessible workspace with MLC covered (non-coplanar) gantry angles of [-113°;+112°] (cranial) and [-108°;+102°] (body), and collimator angles of [-100°;+107°] (cranial) and [-91°;+100°] (body). Average leaf position offsets were ≤0.2mm in 14 standard A/P Bayouth tests and ≤0.6mm in 8 non-standard direction tests. Pre-test MLC exercise increased jaggedness (range ±0.3mm vs. ±0.5mm) and allowed to identify one malfunctioning leaf motor. Total system accuracy with MLC was 0.39±0.06mm in 6 End-to-End tests. Picket-Fence and AQA showed no adverse trends during the test period. Conclusion: The Incise™ MLC for CyberKnife M6™ displayed high accuracy and mechanical stability over the test period. The

  4. Employing Computer-Administered Exams in General Psychology: Student Anxiety and Expectations

    ERIC Educational Resources Information Center

    Schult, Carolyn A.; McIntosh, John L.

    2004-01-01

    Computer-administered exams offer many advantages, but instructors may be reluctant to use them due to concerns that computer anxiety may increase student test anxiety. Introductory psychology students (N = 265) completed surveys prior to their first exam about their anxiety related to the upcoming exam, computers in general, and taking exams on…

  5. Going Green and Using Less Paper to Print Exams: Student Performance, Completion Time, and Preference

    ERIC Educational Resources Information Center

    O'Connor, Kevin J.

    2014-01-01

    Two studies measured the impact on student exam performance and exam completion time of strategies aimed to reduce the amount of paper used for printing multiple-choice course exams. Study 1 compared single-sided to double-sided printed exams. Study 2 compared a single-column arrangement of multiple-choice answer options to a space (and paper)…

  6. Image-based dynamic MLC tracking of moving targets during intensity modulated arc therapy

    PubMed Central

    Poulsen, Per Rugaard; Fledelius, Walther; Cho, Byungchul; Keall, Paul

    2012-01-01

    Purpose Intensity modulated arc therapy (IMAT) enables efficient and highly conformal dose delivery. However, intrafraction motion may compromise the delivered target dose distribution. Dynamic MLC (DMLC) tracking can potentially mitigate the impact of target motion on the dose. The purpose of this study was to use a single kV imager for DMLC tracking during IMAT and to investigate the ability of this tracking to maintain the dose distribution. Methods A motion phantom carrying a 2D ion chamber array and build-up material with an embedded gold marker reproduced eight representative tumor trajectories(four lung tumors,four prostate). For each trajectory, a low and high intensity modulated IMAT plan were delivered with and without DMLC tracking. The 3D real-time target position signal for tracking was provided by fluoroscopic kV images acquired immediately before and during treatment. For each image, the 3D position of the embedded marker was estimated from the imaged 2D position by a probability based method. The MLC leaves were continuously refitted to the estimated 3D position. For lung, prediction was used to compensate for the tracking latency. The delivered 2D dose distributions were measured with the ion chamber array and compared with a reference dose distribution delivered without target motion using a 3%/3mm γ-test. Results For lung tumor motion, tracking reduced the mean γ-failure rate from 38% to 0.7% for low modulation IMAT plans and from 44% to 2.8% for high modulation plans. For prostate, the γ-failure rate reduction was from 19% to 0% (low modulation) and from 20% to 2.7% (high modulation). The dominating contributor to the residual γ-failures during tracking was target localization errors for most lung cases and leaf fitting for most prostate cases. Conclusion Image-based tracking for IMAT was demonstrated for the first time. The tracking greatly improved the dose distributions to moving targets. PMID:22401924

  7. Technical Note: Motion-perturbation method applied to dosimetry of dynamic MLC target tracking—A proof-of-concept

    SciTech Connect

    Feygelman, Vladimir Tonner, Brian; Hunt, Dylan; Zhang, Geoffrey; Moros, Eduardo; Stambaugh, Cassandra; Nelms, Benjamin E.

    2015-11-15

    Purpose: Previous studies show that dose to a moving target can be estimated using 4D measurement-guided dose reconstruction based on a process called virtual motion simulation, or VMS. A potential extension of VMS is to estimate dose during dynamic multileaf collimator (MLC)-tracking treatments. The authors introduce a modified VMS method and quantify its performance as proof-of-concept for tracking applications. Methods: Direct measurements with a moving biplanar diode array were used to verify accuracy of the VMS dose estimates. A tracking environment for variably sized circular MLC apertures was simulated by sending preprogrammed control points to the MLC while simultaneously moving the accelerator treatment table. Sensitivity of the method to simulated tracking latency (0–700 ms) was also studied. Potential applicability of VMS to fast changing beam apertures was evaluated by modeling, based on the demonstrated dependence of the cumulative dose on the temporal dose gradient. Results: When physical and virtual latencies were matched, the agreement rates (2% global/2 mm gamma) between the VMS and the biplanar dosimeter were above 96%. When compared to their own reference dose (0 induced latency), the agreement rates for VMS and biplanar array track closely up to 200 ms of induced latency with 10% low-dose cutoff threshold and 300 ms with 50% cutoff. Time-resolved measurements suggest that even in the modulated beams, the error in the cumulative dose introduced by the 200 ms VMS time resolution is not likely to exceed 0.5%. Conclusions: Based on current results and prior benchmarks of VMS accuracy, the authors postulate that this approach should be applicable to any MLC-tracking treatments where leaf speeds do not exceed those of the current Varian accelerators.

  8. Immunosuppressant MPA Modulates Tight Junction through Epigenetic Activation of MLCK/MLC-2 Pathway via p38MAPK

    PubMed Central

    Khan, Niamat; Pantakani, D. V. Krishna; Binder, Lutz; Qasim, Muhammad; Asif, Abdul R.

    2015-01-01

    Background: Mycophenolic acid (MPA) is an important immunosuppressive drug (ISD) prescribed to prevent graft rejection in the organ transplanted patients, however, its use is also associated with adverse side effects like sporadic gastrointestinal (GI) disturbances. Recently, we reported the MPA induced tight junctions (TJs) deregulation which involves MLCK/MLC-2 pathway. Here, we investigated the global histone acetylation as well as gene-specific chromatin signature of several genes associated with TJs regulation in Caco-2 cells after MPA treatment. Results: The epigenetic analysis shows that MPA treatment increases the global histone acetylation levels as well as the enrichment for transcriptional active histone modification mark (H3K4me3) at promoter regions of p38MAPK, ATF-2, MLCK, and MLC-2. In contrast, the promoter region of occludin was enriched for transcriptional repressive histone modification mark (H3K27me3) after MPA treatment. In line with the chromatin status, MPA treatment increased the expression of p38MAPK, ATF-2, MLCK, and MLC-2 both at transcriptional and translational level, while occludin expression was negatively influenced. Interestingly, the MPA induced gene expression changes and functional properties of Caco-2 cells could be blocked by the inhibition of p38MAPK using a chemical inhibitor (SB203580). Conclusions: Collectively, our results highlight that MPA disrupts the structure of TJs via p38MAPK-dependent activation of MLCK/MLC-2 pathway that results in decreased integrity of Caco-2 monolayer. These results led us to suggest that p38MAPK-mediated lose integrity of epithelial monolayer could be the possible cause of GI disturbance (barrier dysfunction) in the intestine, leading to leaky style diarrhea observed in the organ-transplanted patients treated with MPA. PMID:26733876

  9. A dosimetric evaluation of the Eclipse AAA algorithm and Millennium 120 MLC for cranial intensity-modulated radiosurgery

    SciTech Connect

    Calvo Ortega, Juan Francisco Moragues, Sandra; Pozo, Miquel; José, Sol San; Puertas, Enrique; Fernández, Jaime; Casals, Joan

    2014-07-01

    The aim of this study is to assess the accuracy of a convolution-based algorithm (anisotropic analytical algorithm [AAA]) implemented in the Eclipse planning system for intensity-modulated radiosurgery (IMRS) planning of small cranial targets by using a 5-mm leaf-width multileaf collimator (MLC). Overall, 24 patient-based IMRS plans for cranial lesions of variable size (0.3 to 15.1 cc) were planned (Eclipse, AAA, version 10.0.28) using fixed field-based IMRS produced by a Varian linear accelerator equipped with a 120 MLC (5-mm width on central leaves). Plan accuracy was evaluated according to phantom-based measurements performed with radiochromic film (EBT2, ISP, Wayne, NJ). Film 2D dose distributions were performed with the FilmQA Pro software (version 2011, Ashland, OH) by using the triple-channel dosimetry method. Comparison between computed and measured 2D dose distributions was performed using the gamma method (3%/1 mm). Performance of the MLC was checked by inspection of the DynaLog files created by the linear accelerator during the delivery of each dynamic field. The absolute difference between the calculated and measured isocenter doses for all the IMRS plans was 2.5% ± 2.1%. The gamma evaluation method resulted in high average passing rates of 98.9% ± 1.4% (red channel) and 98.9% ± 1.5% (blue and green channels). DynaLog file analysis revealed a maximum root mean square error of 0.46 mm. According to our results, we conclude that the Eclipse/AAA algorithm provides accurate cranial IMRS dose distributions that may be accurately delivered by a Varian linac equipped with a Millennium 120 MLC.

  10. Dosimetric comparison between two MLC systems commonly used for stereotactic radiosurgery and radiotherapy: a Monte Carlo and experimental study.

    PubMed

    Asnaashari, K; Chow, James C L; Heydarian, Mostafa

    2013-06-01

    In this work dosimetric parameters of two multi-leaf collimator (MLC) systems, namely the beam modulator (BM), which is the MLC commercial name for Elekta "Synergy S" linear accelerator and Radionics micro-MLC (MMLC), are compared using measurements and Monte Carlo simulations. Dosimetric parameters, such as percentage depth doses (PDDs), in-plane and cross-plane dose profiles, and penumbras for different depths and field sizes of the 6 MV photon beams were measured using ionization chamber and a water tank. The collimator leakages were measured using radiographic films. MMLC and BM were modeled using the EGSnrc-based BEAMnrc Monte Carlo code and above dosimetric parameters were calculated. The energy fluence spectra for the two MLCs were also determined using the BEAMnrc and BEAMDP. Dosimetric parameters of the two MLCs were similar, except for penumbras. Leaf-side and leaf-end 80-20% dose penumbras at 10 cm depth for a 10×10 cm(2) field size were 4.8 and 5.1mm for MMLC and 5.3 mm and 6.3 mm for BM, respectively. Both Radionics MMLC and Elekta BM can be used effectively based on their dosimetric characteristics for stereotactic radiosurgery and radiotherapy, although the former showed slightly sharper dose penumbra especially in the leaf-end direction. PMID:22658764