bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term changes in weed occurrence, yield and use of herbicides in maize in south‐western Germany, with implications for the determination of economic thresholds
Authors: Keller M , Böhringer N , Möhring J , Rueda‐Ayala V , Gutjahr C , Gerhards R 
Published: July 2014

SummaryIn 393 field experiments in Baden‐Württemberg region in south‐western Germany, herbicide efficacy, yield loss and crop tolerance of maize (Zea mays) were investigated between 1981 and 2011. The collected data served to determine changes in weed frequencies, in herbicide use, yield loss functions and economic thresholds (ETs). Over 60 weed species were reported. Chenopodium album and Galium aparine were the most frequent broad‐leaved weeds, the former becoming more frequent over time. Species of the genera Lamium, Polygonum, Veronica and Matricaria occurred in about every fifth trial. Alopecurus myosuroides and Echinochloa crus‐galli were the most frequent grass weeds; the former declining in frequency by 1.1% per year, the latter increasing by 1.5%. Results suggest a weed population shift towards thermophilic species. aceto‐lactate‐synthase and 4‐HPPD‐inhibitor herbicides became important in the 1990s. Pendimethalin and bromoxynil have been integral components of weed control since the 1980s. ETs, the point at which weed control operations provide economic returns over input costs, ranged between 3.7% and 5.8% relative weed coverage. Without weed control, no yield increase was found over 24 years. Yield increased by 0.2 t ha−1 year−1, if weeds were controlled chemically. Despite intensive use of effective herbicides in maize, problematic weed species abundance and yield losses due to weed competition have increased in Baden‐Württemberg over a period of 30 years.
A novel adaptive discrete cosine transform‐domain filter for gap‐inpainting of high resolution PET scanners
Authors: Shih Cheng‐Ting , Wu Jay , Lin Hsin‐Hon , Chang Shu‐Jun , Chuang Keh‐Shih 
Published: July 2014

Purpose:Several positron emission tomography (PET) scanners with special detector block arrangements have been developed in recent years to improve the resolution of PET images. However, the discontinuous detector blocks cause gaps in the sinogram. This study proposes an adaptive discrete cosine transform‐based (aDCT) filter for gap‐inpainting.Methods:The gap‐corrupted sinogram was morphologically closed and subsequently converted to the DCT domain. A certain number of the largest coefficients in the DCT spectrum were identified to determine the low‐frequency preservation region. The weighting factors for the remaining coefficients were determined by an exponential weighting function. The aDCT filter was constructed and applied to two digital phantoms and a simulated phantom introduced with various levels of noise.Results:For the Shepp‐Logan head phantom, the aDCT filter filled the gaps effectively. For the Jaszczak phantom, no secondary artifacts were induced after aDCT filtering. The percent mean square error and mean structure similarity of the aDCT filter were superior to those of the DCT2 filter at all noise levels. For the simulated striatal dopamine innervation study, the aDCT filter recovered the shape of the striatum and restored the striatum to reference activity ratios to the ideal value.Conclusions:The proposed aDCT filter can recover the missing gap data in the sinogram and improve the image quality and quantitative accuracy of PET images.
SU‐E‐P‐11: Gurukkul – A Cloud Based Resident Management System
Authors: Palaniswaamy G , Morrow A , Oddiraju S , Gutti V , Rangaraj D 
Published: July 2014

Aim:To evaluate Gurukkul, a commercially available software tool that can help residency programs maintain documentation and compliance with accreditation standards. It helps both the resident and residency program to effectively manage responsibilities. Materials: Gurukkul has different modules to track resident progress and help manage the program effectively.Administration: ‐Three levels of access: admin, mentor and resident; each with different rights to appropriately upload documents, edit and review information enabling the program compliance with accreditation standards. Management: ‐Configure, view and edit several modules to track and review resident progress such as: Rotation description, Rotation schedule, Course and Seminar management. ‐Checklists to evaluate resident competency in each rotation. ‐Alerts, reminders and notifications of upcoming deadlines, pending tasks and approvals.Performance: ‐View reports tracking individual and group performance throughout the program. ‐Enable accountability by tracking time of completion and approval of tasks. ‐Dashboard to view current activities and alerts Evaluation: ‐360° evaluations for residents, faculty and program tailored to institutional performance metrics. Self‐assessment: ‐Configure, schedule and administer testing materials linked to rotation topics. ‐Guide education through question‐based approach.Results:Advantages: Organized platform for managing residency program. Performance monitor and dashboard ensure timeliness of tasks. Self‐assessment modules better prepare residents for rotation exams. Reading and competency checklists help complete assigned tasks. Timelines were met after using this system unlike before where we used to miss reports and resident presentations. Administration and documentation time reduced significantly as they were better organized and readily available. Reduces administration/documentation time. Helpful during accreditation site visits. Disadvantages: Time‐consuming initial setup.Conclusion:This tool is multi‐functional as: residency program management, resident management, resident learning resource, resident and program evaluation. It relieves documentation and management time from faculty and residents that can be used towards actual learning. Dashboards keep everyone up‐to‐date. Specifically, it can help immensely during accreditation site visits.Dr. Rangaraj is the founder of Crux Quality Solutions LLC which markets Gurukkul.
SU‐C‐17A‐06: Motion Compensation in Dynamic Contrast Enhanced MRI
Authors: Liu W , Sung K , Ruan D 
Published: July 2014

Purpose:To apply a newly developed shape‐based registration scheme for motion compensation in MR urography and verify its efficacy in facilitating quantitative functional analysis.Methods:We have recently developed a shape‐based registration scheme that is robust w.r.t. intensity inconsistency. In this study, we utilized this robust registration tool to estimate kidney motion during the MRU scans and compensate for such motion to facilitate the quantitative functional analysis. To validate the efficacy of this scheme, MRU analysis was performed on dataset acquired from sedated subjects to obtain ground‐truth (motion‐free) functional estimates. Physiologically sound motion was then simulated to synthesize image sequences influenced by respiratory motion. Quantitative assessment and comparison were performed amongst ground‐truth, calculations without and with motion compensation for the following set of functional parameters: the contrast dynamic of the left and right cortex, medulla and aorta, the Patlak number and the globular filtration rate (GFR) based on the Patalk‐Rutland model, and the Patlak differential renal function (pDRF).Results:Without motion compensation, the generated relative enhancement curves contained large fluctuations and the estimated GFR values were underestimated by 26% (75.4 ml/min) and 30% (95.3 ml/min) compared with the ground truth of 101.9ml/min and 134.3ml/min for the left and right kidney respectively. Such large errors could result in misleading diagnosis if a typical threshold of 90ml/min were used to determine renal function abnormality. Upon proposed motion compensation, the relative enhancement curves were much smoother and the GFR estimation errors for the left and right kidneys reduced to 0.4% and 1.6% respectively, demonstrating the advantage of the introduced motion compensation method.Conclusion:The developed motion compensation method has demonstrated its ability to facilitate quantitative MRU functional analysis, with improved accuracy of pharmacokinetic modeling and quantitative parameter estimations. Future work will consider incorporating more complex and realistic pharmacokinetic models into the MRU analysis.
SU‐C‐18A‐05: Registration Accuracy of MR‐Based Images to On‐Board Megavoltage Cone‐Beam CT for Brain Patient Setup
Authors: Pinnaduwage D S , Chen J , Descovich M , Hwang Ken‐Ping , Pouliot J 
Published: July 2014

Purpose:To quantify the difference in isocenter shifts when co‐registering MR and MR‐based pseudo CTs (pCT) with on‐board megavoltage conebeam CT (CBCT) images.Methods:Fast Spoiled Gradient Echo MRs were used to generate pCTs (research version of Advantage Sim MD™, GE Healthcare) for ten patients who had prior brain radiotherapy. The planning CT (rCT) for each was co‐registered with the MR, and the plan isocenter and two other reference points were transferred to the MR and pCT. CBCT images (with the machine isocenter) from a single treatment day were coregistered with the 3 test images (MR, pCT and rCT), by two observers and by an automated registration algorithm. The reference points were used to calculate patient shifts and rotations from the registrations. The shifts calculated from the test image registrations were compared to each other and to the shifts performed by the therapists who treated the patients on that day.Results:The average difference in absolute value between the isocenter shifts from the MR‐, pCT‐ and rCT‐CBCT registrations, and the therapist shifts, were 2.02, 3.01 and 0.89 mm (craniocaudal), 1.14, 1.34 and 0.46 mm (lateral), and 1.37, 3.43 and 1.43 mm (vertical), respectively. The MR‐ and pCT‐CBCT registrations differed by 1.99, and 2.53 mm (craniocaudal), 1.36, and 1.37 mm (lateral), and 0.74 and 2.34 mm (vertical), respectively, from the average rCT‐CBCT shifts. On average, differences of 2.39 (craniocaudal), 1.28 (lateral) and 2.84 mm (vertical) were seen between the MR and pCT shifts. Rotations relative to the CBCT coordinate system were on average <2° for the MR and rCT, and <6° for the pCT.Conclusion:In this study, FSPGR MR‐CBCT registrations were more precise compared to the pCT‐CBCT registrations. For improved accuracy, MR sequences that are optimal for bony anatomy visualization are necessary.GE healthcare has provided a research version of Advantage Sim MD to UCSF. No financial support was provided.
SU‐C‐18A‐06: Tracking Fuzzy Border Using Geodesic Curve and Its Application to Liver Segmentation On Planning CT
Authors: Yuan Y , Chao M , Sheu R , Rosenzweig K , Lo Y 
Published: July 2014

Purpose:To investigate the feasibility of using geodesic curves to track fuzzy borders between liver and chest wall and to evaluate how it could improve the performance of automatic liver segmentation on treatment planning CT images.Methods:The performance of automatic liver segmentation usually suffers from the fuzzy borders between liver and the adjacent chest wall due to similar HU values on non‐contrast‐enhanced planning CT images. To address this issue, geodesic curves were used to track these fuzzy borders. We first constructed a horizontal gradient map on the coronal‐view images. After automatically identifying one starting and one ending point, a minimal distance map (MDM) was constructed by evolving a front starting from an infinitesimal circle around the ending point to every pixel on the image. The value of each point in MDM represents the minimal distance from the point to the ending point, which combines both arc length and gradient magnitude along the path. The front evolution was numerically solved by fast‐marching method. We coupled this method with our automatic liver segmentation method, in which an initial contour was firstly estimated by adaptive thresholding and then a distance‐regularized geodesic active contour model was used to further refine the contour. Besides visual assessment, dice similarity coefficient (DSC) was calculated to quantitatively compare the computer‐generated contours with manual outlines.Results:This study included five patients with 597 CT slices who received SBRT liver treatment. We observed clear separation between liver and chest wall after delineation. The results of automatic segmentation were in excellent agreement with manual outlines, yielding all DSCs higher than 0.9 with mean of 0.93.Conclusion:The preliminary results demonstrate that geodesic curve can be used to track fuzzy borders between liver and chest wall, and thus to improve the performance of automatic liver segmentation on planning CT images.
SU‐C‐18C‐05: Evaluation of Endovascular Procedures Using Precise Patient Specific Phantoms Created Using Additive Manufacturing
Authors: Russ M , Iacobucci G , Wood R , O' Hara R , Rudin S , Ionita C 
Published: July 2014

Purpose:The development of patient specific models for endovascular procedures using additive manufacturing.Methods:The work to be presented is composed of two parts: manufacturing and testing of patientspecific phantoms. Phantom manufacturing began with acquisition of 3D patient data and segmentation for the generation of a printable STL file. The models were printed using a Polyjet printer, Objet Eden260V. Once printed, the phantoms were cleaned of support material, and tested for geometric accuracy as compared to the original patient specific data. Imaging validation using x‐ray angiography and qualitative evaluation of mechanical properties were also performed during an endovascular image‐guided intervention. Several iterations of phantoms have been printed and tested, and optimal design parameters have been determined for a favorable manufactured output.Results:The most challenging aspect of phantom manufacturing, as experienced in both simple and complex phantoms, is the removal of support material. Cleaning support material from inside of vessels can be mechanically difficult due to tortuous designs, and must be performed delicately to prevent wall rupture. Phantoms required NaOH baths and high‐pressure washing to eliminate all support materials. Phantom accuracy testing showed size variations of 120μm, a very good agreement with the original design. Interventionists experienced similar back pressure from phantoms when testing mechanical behavior in simulated clinical procedures.Conclusion:This process can serve as a viable tool for procedures and devices, and present unique learning opportunities for the endovascular field as a whole.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation
SU‐D‐18A‐06: Variation of Controlled Breath Hold From CT Simulation to Treatment and Its Dosimetric Impact for Left‐Sided Breast Radiotherapy with a Real‐Time Optical Tracking System
Authors: Mittauer K , Deraniyagala R , Li J , Lu B , Liu C , Lightsey J , Yan G 
Published: July 2014

Purpose:Different breath‐hold (BH) maneuvers (abdominal breathing vs. chest breathing) during CT simulation and treatment can lead to chest wall positional variation. The purpose of this study is to quantify the variation of active breathing control (ABC)‐assisted BH and estimate its dosimetric impact for left‐sided whole‐breast radiotherapy with a real‐time optical tracking system (OTS).Methods:Seven breast cancer patients were included. An in‐house OTS tracked an infrared (IR) marker affixed over the xiphoid process of the patient at CT simulation and throughout the treatment course to measure BH variations. Correlation between the IR marker and the breast was studied for dosimetric purposes. The positional variations of 860 BHs were retrospectively incorporated into treatment plans to assess their dosimetric impact on breast and cardiac organs (heart and left anterior descending artery [LAD]).Results:The mean intrafraction variations were 2.8 mm, 2.7 mm, and 1.6 mm in the anteroposterior (AP), craniocaudal (CC), and mediolateral (ML) directions, respectively. Mean stability in any direction was within 1.5 mm. A general trend of BH undershoot at treatment relative to CT simulation was observed with an average of 4.4 mm, 3.6 mm, and 0.1 mm in the AP, CC, and ML directions, respectively. Undershoot up to 12.6 mm was observed for individual patients. The difference between the planned and delivered dose to breast targets was negligible. The average planned/delivered mean heart doses, mean LAD doses, and max LAD doses were 1.4/2.1, 7.4/15.7, and 18.6/31.0 Gy, respectively.Conclusion:Systematic undershoot was observed in ABC‐assisted BHs from CT simulation to treatment. Its dosimetric impact on breast coverage was minimized with image guidance, but the benefits of cardiac organ sparing were degraded. A real‐time tracking system can be used in junction with the ABC device to improve BH reproducibility.
SU‐D‐18C‐02: Feasibility of Using a Short ASL Scan for Calibrating Cerebral Blood Flow Obtained From DSC‐MRI
Authors: Wang P , Chang T , Huang K , Yeh C , Chien C , Wai Y , Lee T , Liu H 
Published: July 2014

Purpose:This study aimed to evaluate the feasibility of using a short arterial spin labeling (ASL) scan for calibrating the dynamic susceptibility contrast‐ (DSC‐) MRI in a group of patients with internal carotid artery stenosis.Methods:Six patients with unilateral ICA stenosis enrolled in the study on a 3T clinical MRI scanner. The ASL‐cerebral blood flow (‐CBF) maps were calculated by averaging different number of dynamic points (N=1‐45) acquired by using a Q2TIPS sequence. For DSC perfusion analysis, arterial input function was selected to derive the relative cerebral blood flow (rCBF) map and the delay (Tmax) map. Patient‐specific CF was calculated from the mean ASL‐ and DSC‐CBF obtained from three different masks: (1)Tmax< 3s, (2)combined gray matter mask with mask 1, (3)mask 2 with large vessels removed. One CF value was created for each number of averages by using each of the three masks for calibrating the DSC‐CBF map. The CF value of the largest number of averages (NL=45) was used to determine the acceptable range(< 10%, <15%, and <20%) of CF values corresponding to the minimally acceptable number of average (NS) for each patient.Results:Comparing DSC CBF maps corrected by CF values of NL (CBFL) in ACA, MCA and PCA territories, all masks resulted in smaller CBF on the ipsilateral side than the contralateral side of the MCA territory(p<.05). The values obtained from mask 1 were significantly different than the mask 3(p<.05). Using mask 3, the medium values of Ns were 4(<10%), 2(<15%) and 2(<20%), with the worst case scenario (maximum Ns) of 25, 4, and 4, respectively.Conclusion:This study found that reliable calibration of DSC‐CBF can be achieved from a short pulsed ASL scan. We suggested use a mask based on the Tmax threshold, the inclusion of gray matter only and the exclusion of large vessels for performing the calibration.
SU‐D‐18C‐03: In Vivo MR Imaging Using a Combined Single‐Point Dixon and Phase‐Sensitive Inversion Recovery Technique
Authors: Son J , Hazle J , Ma J 
Published: July 2014

Purpose:To demonstrate combined single‐point Dixon water/fat separation and phase sensitive inversion recovery imaging in in vivo brain images acquired in a single scan.Methods:A single inversion recovery image is acquired with an inversion‐time (TI) selected to maximize the dynamic range of the longitudinal magnetization of the water signals and at an echo time (TE) to introduce an orthogonal phase‐difference (i.e. 90°) between the fat and water signals. In the image reconstruction, spatially smooth background phase errors due to static magnetic field inhomogeneity are estimated by applying a region growing based phase correction algorithm: the algorithm first determines spatial phase jumps of 180° and then the second spatial phase jumps of 90°. After the background phase‐errors are removed from the acquired image, phase sensitive inversion recovery (PSIR) water‐only image and a separate fat‐only image can be generated as the real and imaginary parts of the phase‐corrected image, respectively.Results:The pulse sequence was implemented on a 3T whole‐body clinical scanner and a single brain image of a healthy volunteer was acquired. The acquired image was confirmed to contain an orthogonal phase difference between water and fat boundaries and 180o phase difference between the boundaries of long and short T1‐water tissues. The background phase errors were successfully determined and removed by the proposed phase correction algorithm and uniformly separated fat‐only and PSIR water‐only images were reconstructed without artefacts.Conclusion:We demonstrated combined single‐point Dixon water/fat separation and PSIR imaging in in vivo brain images acquired in a single scan. Such images can be useful when fat suppression and enhanced T1‐contrast are desired. Potential areas of application may include imaging of the brain or myocardium.
SU‐D‐18C‐06: Initial Experience with Implementing MRI Safety Guidelines for Patients with Pacemakers – Medical Physicist Perspective
Authors: James J , Place V , Edmonson H , Felmlee J , Pooley R , Panda A 
Published: July 2014

Purpose:Several institutions have developed MRI guidelines for patients with MR‐unsafe or MR‐conditional pacemakers. Here we highlight the role of a medical physicist in implementing these guidelines for non‐pacemaker dependent patients. Guidelines: Implementing these guidelines requires involvement from several medical specialties and a strong collaboration with the site MRI supervisor to develop a structured workflow. A medical physicist is required to be present during the scan to supervise the MR scanning and to maintain a safety checklist that ensures: 1) uninterrupted patient communication with the technologist, 2) continuous patient physiologic monitoring (e.g. blood pressure and electrocardiography) by a trained nurse, 3) redundant patient vitals monitoring (e.g. pulse oximetry) due to the possibility of in vivo electrocardiography reading fluctuations during image acquisition. A radiologist is strongly recommended to be available to review the images before patients are discharged from the scanner. Pacemaker MRI should be restricted to 1.5T field strength. The MRI sequences should be optimized by the physicist with regards to: a) SAR: limited to <1.5 W/Kg for MR‐unsafe pacemakers in normal operating mode, b) RF exposure time: <30 min, c) Coils: use T/R coils but not restricted to such, d) Artifacts: further optimization of sequences whenever image quality is compromised due to the pacemaker. In particular, cardiac, breast and left‐shoulder MRIs are most susceptible to these artifacts. Possible strategies to lower the SAR include: a) BW reduction, 2) echo‐train‐length reduction, 3) increase TR, 4) decrease number of averages, 5) decrease flip angle, 6) reduce slices and/or a combination of all the options.Conclusion:A medical physicist in collaboration with the MR supervisor plays an important role in the supervision/implementation of safe MR scanning of pacemaker patients. Developing and establishing a workflow has enabled our institution to scan over 30 patients with pacemakers without complications, including 3 cardiac MR exams.