1,091 results on '"W. Urban"'
Search Results
2. Academic Differences in BSN Admission Routes: Implications for Persistence
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Leslie A. Jennings, Regina W. Urban, and Daisha J. Cipher
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General Nursing ,Education - Abstract
Background: To increase retention of prelicensure nursing students, several routes are used for admission to nursing programs. Students can be accepted as an early matriculation (EM) student at the point of university admission or they can follow a traditional competitive approach (TR) for admission. Method: A retrospective matched cohort study design was used to explore the differences among selected academic variables in two groups of prelicensure undergraduate students ( n = 136) in the same program. Results: EM students had significantly lower science grade point averages (GPAs), pre-program GPAs, and junior-level GPAs than TR students. However, there were no significant differences between the two groups in scores on the RN Fundamentals ATI examination, an important predictor of future NCLEX-RN success. Conclusion: EM students were as successful as their counterparts on standardized examinations in the first semester of a nursing program. More research is needed to understand program outcomes associated with students entering nursing programs via different routes. [ J Nurs Educ . 2023;62(5):302–306.]
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- 2023
3. Ring-and-Lock Interactions in Self-Healable Styrenic Copolymers
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Samruddhi Gaikwad and Marek W. Urban
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Colloid and Surface Chemistry ,General Chemistry ,Biochemistry ,Catalysis - Published
- 2023
4. Evaluating Variability of Commercial Liver Fibrosis Elastography Phantoms
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Yuqi Wang, Shigeto Ono, Matthew P. Johnson, Nicholas B. Larson, Ted Lynch, and Matthew W. Urban
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Acoustics and Ultrasonics ,Radiological and Ultrasound Technology ,Biophysics ,Radiology, Nuclear Medicine and imaging - Published
- 2023
5. Well‐being in acute care nurse managers: A risk analysis of physical and mental health factors
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Shirley D. Martin, Regina W. Urban, Dorothy C. Foglia, Jo Sheree Henson, Viji George, and Tricia McCaslin
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General Medicine ,General Nursing - Published
- 2023
6. Factors Associated With Ultrasound Color Doppler Twinkling by Breast Biopsy Markers: In Vitro and Ex Vivo Evaluation of 35 Commercially Available Markers
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Christine U, Lee, Nicholas B, Larson, Matthew W, Urban, A Lee, Miller, Susheil, Uthamaraj, Mara A, Piltin, James W, Jakub, Asha A, Bhatt, James F, Greenleaf, and Gina K, Hesley
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Radiology, Nuclear Medicine and imaging ,General Medicine - Published
- 2023
7. Improving ultrasound‐based brachytherapy needle conspicuity by applying an echogenic coating
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Eric E, Brost, Bradley J, Stish, Christine U, Lee, Matthew W, Urban, and Christopher L, Deufel
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General Medicine - Abstract
Applicator conspicuity in ultrasound-guided brachytherapy procedures is commonly impaired by imaging artifacts or non-ideal imaging geometry, which can slow down applicator position digitization and increase the geometric uncertainty of the delivered dose distribution.The purpose of this study was to improve the conspicuity of high-dose rate (HDR) brachytherapy needles under B-mode ultrasound imaging by applying an echogenic surface coating. Our hypothesis was that an echogenic coating would reduce artifacts and improve needle visualization within regions of signal degradation.In this study, 17-gauge, 25-cm long titanium HDR brachytherapy needles were coated with acoustically reflective microspheres over a 2.5 cm region starting from the needle tip. Three coating thicknesses (27 μm, 40 μm, 64 μm) were compared against an uncoated control needle. The coated and uncoated needles were imaged using B-mode ultrasound in a tissue-equivalent prostate phantom and in a cadaverous male pelvis using a transrectal probe. Needle conspicuity was assessed under multiple conditions: a single needle implant, an implant with multiple needles between the probe and the needle of interest, and an angled needle implant. All images were assessed qualitatively for needle conspicuity and the presence of artifacts and quantitatively using gray-scale image intensity values.The 64 μm echogenic coating reduced the magnitude of reverberation artifacts by 31 ± 14% and comet tail artifacts by 40-70%. The echogenic coating also improved needle contrast, measured by the relative differences in signal intensity compared with the adjacent environment, when needles were angled up to 30An echogenic surface coating reduced imaging artifacts and improved needle conspicuity under realistic clinical conditions for ultrasound-based prostate or gynecological brachytherapy. The improved conspicuity has the potential to improve the efficiency of needle placement and the accuracy of needle position digitization during brachytherapy procedures. This article is protected by copyright. All rights reserved.
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- 2022
8. Resilience, Stress, Anxiety, and Depression: Exploring the Mental Health of New Graduate Nurses Transitioning to Practice During COVID-19
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Regina W. Urban, Meagan R. Rogers, Tamara L. Eades, Patricia M. Allard, Marlene T. Porter, and Daisha J. Cipher
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Mental Health ,Depression ,Review and Exam Preparation ,Humans ,COVID-19 ,Anxiety ,Education, Nursing, Graduate ,Pandemics ,General Nursing ,Education - Abstract
Background Transitioning to practice during the COVID-19 pandemic multiplied the stressors and challenges typically encountered by new graduate nurses (NGNs), yet research exploring mental health variables of this subset of nurses remains sparse. Method This study used an observational design and convenience sampling. NGN alumni ( n = 192) from a pre-licensure nursing program were surveyed during the summer of 2021 regarding their experiences with resilience, anxiety, depression, and stress while transitioning to practice during the COVID-19 pandemic. Results Participants reported moderate to severe levels of stress (76%), anxiety (27.6%), and depression (31.2%) while transitioning to practice. Most (79%) described themselves as resilient. The highest mean scores for stress, anxiety, and depression occurred during the fourth to eighth month of practice. Conclusion Nursing professional development specialists, managers, and other stakeholders need effective strategies to monitor and promote NGNs' well-being and mental health to prevent burnout and turnover throughout the first year of practice. [ J Contin Educ Nurs . 2022;53(12):533–543.]
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- 2022
9. Combined Reprocessability and Self-Healing in Fluorinated Acrylic-Based Covalent Adaptable Networks (CANs)
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Siyang Wang, Lei Li, and Marek W. Urban
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Polymers and Plastics ,Process Chemistry and Technology ,Organic Chemistry - Published
- 2022
10. Redefining polymer science via multi-stimulus responsiveness
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Siyang Wang and Marek W. Urban
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General Chemical Engineering ,Biochemistry (medical) ,Materials Chemistry ,Environmental Chemistry ,General Chemistry ,Biochemistry - Published
- 2023
11. Self-Healable Acrylic-Based Covalently Adaptable Networks
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Siyang Wang, Lei Li, Qianhui Liu, and Marek W. Urban
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Inorganic Chemistry ,Polymers and Plastics ,Organic Chemistry ,Materials Chemistry - Published
- 2022
12. Stimulus-Responsive Macromolecules in Polymeric Coatings
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Qianhui Liu and Marek W. Urban
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Polymers and Plastics ,Renewable Energy, Sustainability and the Environment ,Materials Chemistry ,Biomedical Engineering ,General Chemistry ,Electrical and Electronic Engineering ,Electronic, Optical and Magnetic Materials - Published
- 2022
13. Supplementary Figures 1 - 3 from USP22 Regulates Oncogenic Signaling Pathways to Drive Lethal Cancer Progression
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Karen E. Knudsen, Steven B. McMahon, Angelo M. DeMarzo, Tapio Visakorpi, Rossitza A. Draganova-Tacheva, Ruth C. Birbe, Jessica L. Hicks, Robyn T. Sussman, Timothy J. Stanek, Mark W. Urban, Matthew J. Schiewer, Jonathan F. Goodwin, Jeffry L. Dean, and Randy S. Schrecengost
- Abstract
PDF file - 176K, Supplementary Figure S1: USP22 Specifically Promotes AR Recruitment to Target Loci. Supplementary Figure 2: Depletion of USP22 can be mediated by multiple sequences.Supplementary Figure S3: AR Ubiquitylation Levels are not Altered in Response to USP22 Depletion.
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- 2023
14. Supplementary Table 1 from USP22 Regulates Oncogenic Signaling Pathways to Drive Lethal Cancer Progression
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Karen E. Knudsen, Steven B. McMahon, Angelo M. DeMarzo, Tapio Visakorpi, Rossitza A. Draganova-Tacheva, Ruth C. Birbe, Jessica L. Hicks, Robyn T. Sussman, Timothy J. Stanek, Mark W. Urban, Matthew J. Schiewer, Jonathan F. Goodwin, Jeffry L. Dean, and Randy S. Schrecengost
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PDF file - 50K, Primer sequences used in manuscript.
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- 2023
15. Data from USP22 Regulates Oncogenic Signaling Pathways to Drive Lethal Cancer Progression
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Karen E. Knudsen, Steven B. McMahon, Angelo M. DeMarzo, Tapio Visakorpi, Rossitza A. Draganova-Tacheva, Ruth C. Birbe, Jessica L. Hicks, Robyn T. Sussman, Timothy J. Stanek, Mark W. Urban, Matthew J. Schiewer, Jonathan F. Goodwin, Jeffry L. Dean, and Randy S. Schrecengost
- Abstract
Increasing evidence links deregulation of the ubiquitin-specific proteases 22 (USP22) deubitiquitylase to cancer development and progression in a select group of tumor types, but its specificity and underlying mechanisms of action are not well defined. Here we show that USP22 is a critical promoter of lethal tumor phenotypes that acts by modulating nuclear receptor and oncogenic signaling. In multiple xenograft models of human cancer, modeling of tumor-associated USP22 deregulation demonstrated that USP22 controls androgen receptor accumulation and signaling, and that it enhances expression of critical target genes coregulated by androgen receptor and MYC. USP22 not only reprogrammed androgen receptor function, but was sufficient to induce the transition to therapeutic resistance. Notably, in vivo depletion experiments revealed that USP22 is critical to maintain phenotypes associated with end-stage disease. This was a significant finding given clinical evidence that USP22 is highly deregulated in tumors, which have achieved therapeutic resistance. Taken together, our findings define USP22 as a critical effector of tumor progression, which drives lethal phenotypes, rationalizing this enzyme as an appealing therapeutic target to treat advanced disease. Cancer Res; 74(1); 272–86. ©2013 AACR.
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- 2023
16. Online prelicensure nursing students' experiences of academic incivility during <scp>COVID</scp> ‐19: A qualitative inquiry
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Sharon T. Wilson, Regina W. Urban, and Jessica G. Smith
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General Nursing - Published
- 2023
17. Using dynamic optical coherence elastography to measure material properties
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Matthew W. Urban, Hsiao-Chuan Liu, and Piotr Kijanka
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- 2023
18. Evaluating phase velocity of capillary waves on thin layer fluids using acoustic radiation force-based optical coherence elastography
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Hsiao-Chuan Liu and Matthew W. Urban
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- 2023
19. Shape Memory‐Induced Self‐Healable Polymers
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Siyang Wang, Dmitriy Davydovich, and Marek W. Urban
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- 2022
20. A New Plane Wave Compounding Scheme Using Phase Compensation for Motion Detection
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Hyoung-Ki Lee, James F. Greenleaf, and Matthew W. Urban
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Acoustics and Ultrasonics ,Phantoms, Imaging ,Elasticity Imaging Techniques ,Ultrasonography, Doppler ,Signal-To-Noise Ratio ,Electrical and Electronic Engineering ,Instrumentation ,Article ,Ultrasonography - Abstract
Plane wave (PW) transmission has enabled multiple new applications such as shear wave elastography, ultrafast Doppler imaging, and functional ultrasound imaging. Plane Wave Compounding (PWC), which coherently sums the echo signals from multiple PW transmits with different angles, is widely used to improve B-mode image quality. When the motion between two speckle images is estimated, PWC suffers from an inherent displacement estimation error. This is derived theoretically and experimentally demonstrated in this work. We show that the phase difference between the acquired data with PW emissions with different angles is related to this error. When the absolute value of the phase difference is larger than π/2, the displacement estimation error occurs. A new scheme, named Initial-Phase-Compensated PWC (IPCPWC) is proposed, which compensates the phase of echo signals from each PW transmit and maintains the absolute value of the phase difference smaller than π/2. The increased signal-to-noise ratio and reduced jitter of IPCPWC in motion data are demonstrated using tissue mimicking phantoms compared to PWC.
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- 2022
21. Association of stress, resilience, and nursing student incivility during COVID‐19
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Jessica G. Smith, Regina W. Urban, and Sharon T. Wilson
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Cross-Sectional Studies ,Incivility ,Faculty, Nursing ,COVID-19 ,Humans ,Education, Nursing, Baccalaureate ,Students, Nursing ,Education, Nursing ,General Nursing - Abstract
Although incivility in nursing education is linked with negative physical and psychological effects on students, it is unclear how resilience and stress interact and relate to student incivility. The purpose was to understand the role of resilience and stress with peer incivility in a sample of prelicensure nursing students during coronavirus disease 2019. The study design was cross-sectional and correlational. Data were from an online survey administered to undergraduate nursing students of one college of nursing in a southwestern US state during September-October 2020. In a sample of 490 students, ordinal regression model results supported that including a stress and resilience interaction term resulted in a nonsignificant effect of stress and resilience, as the main effect correlates on low-level uncivil student behavior. More research is needed to understand the prevalence of stress and resilience at different points in prelicensure nursing education so that targeted interventions can be developed and deployed to assist students.
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- 2022
22. Local strain-induced energy storage as driving force for autogenous scratch closure
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V. Montano, M. W. Urban, S. van der Zwaag, and S. J. Garcia
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Renewable Energy, Sustainability and the Environment ,General Materials Science ,General Chemistry - Abstract
Autonomous through-thickness scratch repair (healing) in coatings requires scratch closure and interfacial molecular sealing. Although qualitative aspects of the first stage of self-healing have been addressed, quantitative description enabling the control over the healing process need further understanding. In this work the polymer-architecture-dependent stored entropic energy during deformation is quantified using the rubber elasticity theory and correlated to the scratch closure degree experimentally observed in microscopic measurements. Using well-defined thermoplastic healing polyurethanes with variable soft phase fraction contents these studies show that pressure-free damage closure of scratches maintaining mechanical integrity during healing is governed by the capability of the polymer to store entropic energy during damage. The storage (and release) of energy is controlled by varying the damage and healing temperatures in relation to the specific viscoelastic length transition (TVLT) and the glass transition temperature (Tg). Damage closure increases linearly with the entropy release and is controlled by two parameters of the network, the junction density and damping factor. If mechanical damage does not lead to storage of mechanical energy healing does not occur.
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- 2022
23. Health-related behaviors, self-rated health, and predictors of stress and well-being in nursing students
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Shirley D. Martin, Regina W. Urban, Ann H. Johnson, Dionne Magner, Jennifer E. Wilson, and Yan Zhang
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Cross-Sectional Studies ,Surveys and Questionnaires ,Health Behavior ,Humans ,Education, Nursing, Baccalaureate ,Students, Nursing ,Self-Compassion ,Stress, Psychological ,General Nursing - Abstract
Nursing students are at increased risk for the consequences of stress on wellbeing. Little is known about nursing students' health promoting behaviors and how these relate to health, stress, and well-being.The purpose was to describe perceived stress and measures of well-being (self-compassion, happiness, and life satisfaction) along with self-reported health promoting behaviors and health status in order to identify factors that could affect stress and well-being in nursing students.A multi-site team employed cross-sectional research methods to explore well-being, stress, and potential physical and emotional health-relevant factors in undergraduate nursing students. Baccalaureate Nursing students from three nursing programs in North Texas participated in a web-based survey. Undergraduate students (n = 417) reported being junior or senior level in a traditional (74.1%) or an alternative nursing training program (on-line, fast-track, or weekend nursing program; 24.9%) in the fall of 2019. Recruitment fliers went to a total of 2264 potential participants via university e-mail. Consenting students completed online surveys collecting demographic and health related factors as well as measures of well-being and stress.More than half (56.6%) of students reported worsening health since starting nursing school. Exercise and meditation were related to higher measures of well-being and lower stress, but this relationship diminished in the multivariate model when considering individual demographic and health related factors. Our multivariate model suggests that self-rated health status remains a main potential predictor of reduced stress and improved well-being.Self-reported health factors are related to wellbeing in nursing students. Targeted interventions to improve well-being among nursing students may be necessary and would fit with national recommendations for nursing education programs. Resiliency skills training with mindfulness practices may help nursing students reduce stress, improve overall well-being, and equip students to avoid burnout and stress-related illness once in the workforce.
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- 2022
24. Evaluation of Robustness of Local Phase Velocity Imaging in Homogenous Tissue-Mimicking Phantoms
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Matthew W. Urban, Hsiao-Chuan Liu, Piotr Kijanka, and Benjamin G. Wood
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Curvilinear coordinates ,Materials science ,Acoustics and Ultrasonics ,Radiological and Ultrasound Technology ,Phantoms, Imaging ,Acoustics ,Physics::Medical Physics ,Isotropy ,Biophysics ,Article ,Imaging phantom ,Region of interest ,Elasticity Imaging Techniques ,Group velocity ,Radiology, Nuclear Medicine and imaging ,Phase velocity ,Dispersion (water waves) ,Acoustic radiation force - Abstract
Shear wave elastography (SWE) is a method of evaluating mechanical properties of soft tissues. Most current implementations of SWE report the group velocity for shear wave velocity, which assumes an elastic, isotropic, homogenous and incompressible tissue. Local Phase Velocity Imaging (LPVI) is a novel method of phase velocity reconstruction that allows for accurate evaluation of shear wave velocity at specified frequencies. This method’s robustness was evaluated in 11 elastic and 8 viscoelastic phantoms using linear and curvilinear arrays. We acquired data with acoustic radiation force push beams with different focal depths and F-numbers and reconstructed phase velocity images over a wide range of frequencies. Regardless of phantom, push beam focal depth, and reconstruction frequency, using an F-number around 3.0 was found to produce the largest usable area in the phase velocity reconstructions. For elastic phantoms scanned with a linear array, the optimal focal depth, frequency range, and maximum region-of interest (ROI) were 20–30 mm, 100–400 Hz, and 2.70 cm(2), respectively. For viscoelastic phantoms scanned with a linear array, the optimal focal depth, frequency, and maximum ROI were 20–30 mm, 100–300 Hz, 1.54 cm(2), respectively. For the curvilinear array in the same phantoms; optimal focal depth, frequency range, and maximum ROIs were 45–60 mm, 100–400 Hz and 100–300 Hz, and 1.54 cm(2), respectively. Further work will be done to evaluate LPVI reconstructions from inclusion phantoms to simulate nonhomogeneous tissues. Additionally, LPVI will be evaluated in larger volume phantoms to account for wave reflection from the containers when using the curvilinear array.
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- 2021
25. Basic physicochemical processes governing self‐healable polymers †
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Siyang Wang and Marek W. Urban
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Physicochemical Processes ,chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Polymer science ,chemistry ,Organic Chemistry ,Materials Chemistry ,Polymer - Published
- 2021
26. Using Ultrasound Color Doppler Twinkling to Identify Biopsy Markers in the Breast and Axilla
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Susheil Uthamaraj, James F. Greenleaf, Matthew W. Urban, Gina K. Hesley, Christine U. Lee, and Nicholas B. Larson
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Acoustics and Ultrasonics ,Radiological and Ultrasound Technology ,medicine.diagnostic_test ,business.industry ,Breast imaging ,Biopsy ,Ultrasound ,Biophysics ,Color doppler ,Axilla ,medicine.anatomical_structure ,Optical imaging ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Ultrasonography, Doppler, Color ,Artifacts ,business ,Nuclear medicine ,Breast ultrasound ,Twinkling ,Ultrasonography - Abstract
In breast radiology, ultrasound detection of biopsy markers or clips for localization purposes is often challenging, especially in the axilla. The purpose of this research was to test the hypothesis that the surface roughness of biopsy clips would elicit a twinkling signature on color Doppler, making them more readily identifiable by ultrasound. Ultrasound color Doppler imaging of 12 biopsy markers was performed and consensus scoring of the degree of twinkling (0 [no twinkling] to 4 [exuberant twinkling]) was obtained for each of the markers. The surface roughness characteristics of the markers were measured using 3-D coherence scanning interferometry. The 3 markers scoring at least 3 for twinkling in vitro were cork, Q and Vision. Of these 3 markers, only the cork marker scored a 4 ex vivo and in cadaveric tissue. Surface roughness metrics demonstrated a positive estimated correlation with the twinkling scores (rho = 0.33, 95% CI = [–0.48 to 0.84]). Of the 12 markers tested, the markers that twinkled corresponded to surface roughness measured with non-contact 3-D optical imaging. Qualitatively, lower color scales and color frequencies optimized twinkling, but the most specific qualitative predictor of confidence in twinkling was insensitivity to changes in color scale and color frequency values.
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- 2021
27. Ultrasonographic Detection and Surgical Retrieval of a Nonmetallic Twinkle Marker in Breast Cancer: Pilot Study
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James W. Jakub, Gina K. Hesley, Nicholas B. Larson, Michael J. Yaszemski, A. Lee Miller, James F. Greenleaf, Matthew W. Urban, and Christine U. Lee
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Oncology ,Technical Development ,Axilla ,Humans ,Radiology, Nuclear Medicine and imaging ,Female ,Breast Neoplasms ,Pilot Projects ,Prospective Studies ,Middle Aged ,Neoadjuvant Therapy - Abstract
PURPOSE: To evaluate the short-term safety of a nonmetallic twinkle marker and compare its conspicuity at color Doppler US with that of standard breast biopsy clips and radioactive seeds by using B-mode US in axillary lymph nodes. MATERIALS AND METHODS: This prospective study (November 2020–July 2021) of participants with node-positive breast cancer who completed chemotherapy involved placing a twinkle marker at the time of preoperative radioactive seed localization. A five-point scoring system (1 = easiest, 5 = most difficult) was used to rate the ease of identifying the clip, seed, and twinkle marker on postlocalization sonograms, mammograms, specimen radiographs, and gross pathologic specimens. Descriptive statistics were used. RESULTS: Eight women (mean age, 57 years ± 16 [SD]) were enrolled. The median scores for US conspicuity of each device were 3.9 (range, 3.7–5.0) for the radioactive seed, 2.4 (range, 1.0–5.0) for the clip, and 2.0 (range, 1.0–4.3) for the twinkle marker. In six of eight participants, the twinkle marker was the most identifiable at US. The seeds, clips, and twinkle markers were scored “very easy” to identify on seven of eight postlocalization mammograms. The surgeon retrieved all eight twinkle markers 1–3 days after localization. In all 16 interpretations, the seeds, clips, and twinkle markers were rated as very easy to identify on specimen radiographs. The clip was the most difficult device to identify at pathologic examination in all participants, and the twinkle marker was the easiest to identify in seven of eight participants. CONCLUSION: This pilot study demonstrates that the safety and ease of US detection of a twinkling tissue marker may be comparable to a biopsy clip. Keywords: Ultrasonography, US-Doppler, Breast, Localization, Surgery Clinical trial registration no. NCT04674852 © RSNA, 2022
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- 2022
28. Nonlinear Least-Squares Estimation of Shear Wave Speeds in Viscoelastic Media
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Nicholas A. Bannon, Matthew W. Urban, and Robert J. McGough
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- 2022
29. A time-domain fractional calculus model for shear wave parameter estimation
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Robert J. McGough and Matthew W. Urban
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- 2022
30. Novel Uses of Ultrasound to Assess Kidney Mechanical Properties
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Andrew D. Rule, Matthew W. Urban, Thomas D. Atwell, and Shigao Chen
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Kidney ,medicine.diagnostic_test ,business.industry ,Renal parenchyma ,Disease progression ,Ultrasound ,General Medicine ,Article ,Focused ultrasound ,Imaging Tool ,medicine.anatomical_structure ,Ultrasound imaging ,Elasticity Imaging Techniques ,Medicine ,Elastography ,business ,Forecasting ,Ultrasonography ,Biomedical engineering - Abstract
Ultrasound is a key imaging tool for the evaluation of the kidney. Over the last two decades, methods to measure the mechanical properties of soft tissues have been developed and used in clinical practice, though the use in the kidney has not been as widespread as for other applications. The mechanical properties of the kidney are determined by the structure and composition of the renal parenchyma as well as the perfusion characteristics. As pathological processes change these factors, the mechanical properties change and can be used for diagnostic purposes as well as monitoring treatment or disease progression. Ultrasound-based elastography methods for evaluating the mechanical properties of the kidney use focused ultrasound beams to perturb the kidney and then high frame rate ultrasound methods are used to measure the resulting motion. The motion is analyzed to estimate the mechanical properties. This review will describe the principles of these methods and discuss several seminal studies related to characterizing the kidney. Additionally, an overview of the clinical use of elastography methods in native and kidney allografts will be provided. Perspectives on future developments and uses of elastography technology along with other complementary ultrasound imaging modalities will be provided.
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- 2021
31. Time-Aligned Plane Wave Compounding Methods for High-Frame-Rate Shear Wave Elastography: Experimental Validation and Performance Assessment on Tissue Phantoms
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Matthew W. Urban, James F. Greenleaf, and Margherita Capriotti
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Pulse repetition frequency ,Time Factors ,Materials science ,Acoustics and Ultrasonics ,Acoustics ,Physics::Medical Physics ,Biophysics ,Plane wave ,Signal-To-Noise Ratio ,01 natural sciences ,Article ,Imaging phantom ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,0103 physical sciences ,Radiology, Nuclear Medicine and imaging ,Acoustic radiation force ,010301 acoustics ,Radiological and Ultrasound Technology ,Phantoms, Imaging ,equipment and supplies ,Frame rate ,Elasticity Imaging Techniques ,Group velocity ,Ultrasonic sensor ,Phase velocity - Abstract
Shear wave elastography (SWE) is an ultrasonic technique able to quantitatively assess the mechanical properties of tissues, combining acoustic radiation force and ultrafast imaging. While utilizing coherent plane wave compounding enhances echo and shear wave motion signal-to-noise ratio (SNR), it also reduces the effective pulse repetition frequency (PRF(e)), affecting the accuracy of the measurements of the motion and, consequently, of the material properties. It is important to maintain both high motion SNR and PRF(e), particularly for the characterization of (material and/or geometrical) dispersive tissues such as arteries. This work proposes a method for SWE measurements with high SNR, while maintaining a high PRF(e), using conventional clinical ultrasound scanners. A time alignment process is applied, after acquiring data from plane wave transmissions at different angles. The time alignment uses interpolation to obtain data points at higher frame rates, and the time-aligned data is compounded to increase the SNR. The method is used for SWE in tissue-mimicking phantoms of various stiffness and is compared to traditional plane wave compounding. An increase of 58% and of 36% in spatial and temporal bandwidth compared to conventional plane wave compounding, respectively, can be achieved for SWE measurements of representative arterial stiffness values. Improvements on phase velocity accuracy and bandwidth in an arterial phantom are also presented, to emphasize the beneficial advantage in dispersive cases.
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- 2021
32. Connecting lived experiences of pre-nursing students during COVID-19 with learner well-being: A qualitative inquiry
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Regina W. Urban, Leslie A. Jennings, and Kendall Darr
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General Nursing - Abstract
To explore pre-nursing students' experiences and identify factors influencing their well-being as learners during COVID-19.A qualitative descriptive design was used.Short answer study data (n = 289) were collected in Fall 2020 as part of a larger IRB-approved survey-based study focused on pre-nursing students. Participants were presented with three short answer questions designed to elicit a description of their experiences as a pre-nursing student. NVivo and reflexive thematic analysis were used to analyse participant responses.Six themes related to learner well-being emerged from the data. Learner well-being was supported by achieving academic goals, experiencing positive feelings about current course content, creating connections with peers and envisioning themselves as nurses in the future. Negative contributors to pre-nursing student well-being included managing fears of program rejection and juggling multiple roles and demands. Online learning necessitated by COVID-19 created opportunities for loneliness and isolation from peers, technological difficulties and additional psychological stress, which also contributed negatively to learner well-being.These findings illustrate pre-nursing students' experiences and provide support for the influence of the learning environment and factors within the individual on the well-being of learners.Students preparing to apply to nursing programs are an understudied population and little is known about their well-being as learners. Survey-based open-ended short answer questions can be utilized to gain rich insight into their experiences. The study themes and sub-themes can be utilized for discussion and reflection in courses with pre-nursing students and as a starting point for additional conversations between pre-nursing students and educators regarding improving the support of well-being in learners. Additional research and evidence-based interventions that promote learner well-being in pre-nursing students are needed as they prepare for nursing program admission and to support their academic progression.Members of the public were not involved in the design or conduct of the study, analysis, or interpretation of the data, or in the preparation of the manuscript because the study focus is on gaining an understanding the experiences of pre-nursing students and their well-being.
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- 2022
33. Acoustic Force Elastography Microscopy
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Hsiao-Chuan Liu, Bipin Gaihre, Piotr Kijanka, Lichun Lu, and Matthew W. Urban
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Biomedical Engineering - Abstract
Hydrogel scaffolds have attracted attention to develop cellular therapy and tissue engineering platforms for regenerative medicine applications. Among factors, local mechanical properties of scaffolds drive the functionalities of cell niche. Dynamic mechanical analysis (DMA), the standard method to characterize mechanical properties of hydrogels, restricts development in tissue engineering because the measurement provides a single elasticity value for the sample, requires direct contact, and represents a destructive evaluation preventing longitudinal studies on the same sample. We propose a novel technique, acoustic force elastography microscopy (AFEM), to evaluate elastic properties of tissue engineering scaffolds.AFEM can resolve localized and two-dimensional (2D) elastic properties of both transparent and opaque materials with advantages of being non-contact and non-destructive. Gelatin hydrogels, neat synthetic oligo[poly(ethylene glycol)fumarate] (OPF) scaffolds, OPF hydroxyapatite nanocomposite scaffolds and ex vivo biological tissue were examined with AFEM to evaluate the elastic modulus. These measurements of Young's modulus range from approximately 2 kPa to over 100 kPa were evaluated and are in good agreement with finite element simulations, surface wave measurements, and DMA tests.The AFEM can resolve localized and 2D elastic properties of hydrogels, scaffolds and thin biological tissues. These materials can either be transparent or non-transparent and their evaluation can be done in a non-contact and non-destructive manner, thereby facilitating longitudinal evaluation.AFEM is a promising technique to quantify elastic properties of scaffolds for tissue engineering and will be applied to provide new insights for exploring elastic changes of cell-laden scaffolds for tissue engineering and material science.
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- 2022
34. Low-spin excitations in Br89 populated in β− decay of Se89
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T. Rząca-Urban, K. Sieja, M. Czerwiński, J. Kurpeta, M. Pomorski, W. Urban, J. Wiśniewski, M. Wróblewski, L. Canete, T. Eronen, S. Geldhof, A. Jokinen, A. Kankainen, I. D. Moore, D. Nesterenko, H. Penttilä, I. Pohjalainen, S. Rinta-Antila, A. de Roubin, and M. Vilén
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- 2022
35. Hydrogen Permeability of Self-Healing Copolymers for Use in Hydrogen Delivery Applications
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Dale Hitchcock, Timothy Krentz, Anastasia Mullins, Charles James, Qianhui Liu, Siyang Wang, Samruddhi Gaikwad, and Marek W. Urban
- Abstract
Safe and reliable fueling components are essential for large scale deployment of H2 fuel. Field data has shown that existing materials used in dispensing hoses do not meet current standards for component reliability. Currently modern copolymerization methods are under investigation to create a new platform for inner hose technologies using self-healable copolymers. Ideally these inexpensive self-healable copolymer inner layers will reduce the cost of H2 delivery hoses and extend their service life beyond 25,000 refills. In this work gas driven hydrogen permeability measurements were performed on a variety of self-healing copolymer membranes all of which have exhibited excellent self-healing properties in previous studies. Copolymers were prepared with Poly(2,2,2-trifluoroethyl methacrylate/n-butyl acrylate) [p(TFEMA/nBA)] and Poly(methyl methacrylate/nbutyl acrylate) [p(MMA/nBA)]. Measurements were performed through a range of temperatures and source pressures. Additionally, the effects of composition, copolymer ratio, and molecular weight on the hydrogen permeability, solubility, and diffusivity were all studied. As expected, hydrogen permeation through the samples is proportional to the source pressure and inversely proportional to the molecular weight of the polymer. In general, the self-healing copolymers exhibit hydrogen permeabilities consistent with literature data for similar elastomers. These results suggest this class of self-healable copolymers may be promising candidates for use as inexpensive inner layers in hydrogen dispensing hoses with extended service life.
- Published
- 2022
36. New β -decay spectroscopy of the Te137 nucleus
- Author
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M. Si, R. Lozeva, H. Naïdja, A. Blanc, J.-M. Daugas, F. Didierjean, G. Duchêne, U. Köster, T. Kurtukian-Nieto, F. Le Blanc, P. Mutti, M. Ramdhane, and W. Urban
- Published
- 2022
37. Phase Velocity Estimation With Expanded Bandwidth in Viscoelastic Phantoms and Tissues
- Author
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Piotr Kijanka and Matthew W. Urban
- Subjects
Shear waves ,Materials science ,Swine ,Frequency band ,Acoustics ,Physics::Medical Physics ,Article ,Imaging phantom ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Dispersion (optics) ,Animals ,Electrical and Electronic Engineering ,Acoustic radiation force ,Fourier Analysis ,Radiological and Ultrasound Technology ,Phantoms, Imaging ,Viscosity ,Velocity dispersion ,Computer Science Applications ,Wavelength ,Elasticity Imaging Techniques ,Phase velocity ,Algorithms ,Software - Abstract
Ultrasound shear wave elastography (SWE) is a technique used to measure mechanical properties to evaluate healthy and pathological soft tissues. SWE typically employs an acoustic radiation force (ARF) to generate laterally propagating shear waves that are tracked in the spatiotemporal domains, and algorithms are used to estimate the wave velocity. The tissue viscoelasticity is often examined through analyzing the shear wave phase velocity dispersion curves, which is the variation of phase velocity with frequency or wavelength. A number of available methods to estimate dispersion exist, which can differ in resolution and variance. Moreover, most of these techniques reconstruct dispersion curves for a limited frequency band. In this work, we propose a novel method used for dispersion curve calculation. Our unique approach uses a generalized Stockwell transformation combined with a slant frequency-wavenumber analysis (GST-SFK). We tested the GST-SFK method on numerical phantom data generated using a finite-difference-based method in tissue-mimicking viscoelastic media. In addition, we evaluated the method on numerical shear wave motion data with different amounts of white Gaussian noise added. Additionally, we performed tests on data from custom-made tissue-mimicking viscoelastic phantom experiments, ex vivo porcine liver measurements, and in vivo liver tissue experiments. We compared results from our method with two other techniques used for estimating shear wave phase velocity: the two-dimensional Fourier transform (2D-FT) and the eigenvector (EV) method. Tests carried out revealed that the GST-SFK method provides dispersion curve estimates with lower errors over a wider frequency band in comparison to the 2D-FT and EV methods. In addition, the GST-SFK provides expanded bandwidth by a factor of two or more to be used for phase velocity estimation, which is meaningful for a tissue dispersion analysis in vivo .
- Published
- 2021
38. PHSPP06 Presentation Time: 3:20 PM
- Author
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Eric Brost, Susheil Uthamaraj, Matthew W. Urban, Christine U. Lee, and Christopher L. Deufel
- Subjects
Oncology ,Radiology, Nuclear Medicine and imaging - Published
- 2022
39. Twinkling-guided ultrasound detection of polymethyl methacrylate as a potential breast biopsy marker: a comparative investigation
- Author
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Christine U. Lee, Matthew W. Urban, A. Lee Miller, Susheil Uthamaraj, James W. Jakub, Gina K. Hesley, Benjamin G. Wood, Nathan J. Brinkman, James L. Herrick, Nicholas B. Larson, Michael J. Yaszemski, and James F. Greenleaf
- Subjects
Radiology, Nuclear Medicine and imaging - Abstract
Since its first description 25 years ago, color Doppler twinkling has been a compelling ultrasound feature in diagnosing urinary stones. While the fundamental cause of twinkling remains elusive, the distinctive twinkling signature is diagnostically valuable in clinical practice. It can be inferred that if an entity twinkles, it empirically has certain physical features. This work investigates a manipulable polymeric material, polymethyl methacrylate (PMMA), which twinkles and has measurable surface roughness and porosity that likely contribute to twinkling. Comparative investigation of these structural properties and of the twinkling signatures of breast biopsy markers made from PMMA and selected commercially available markers showed how twinkling can improve ultrasound detection of devices intentionally designed to twinkle. While this specific application of detecting breast biopsy markers by twinkling may provide a way to approach an unmet need in the care of patients with breast cancer, this work ultimately provides a platform from which the keys to unlocking the fundamental physics of twinkling can be rigorously explored.
- Published
- 2022
40. Tri-Phasic Size- and Janus Balance-Tunable Colloidal Nanoparticles (JNPs)
- Author
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Chunliang Lu and Marek W. Urban
- Subjects
Acrylate ,Materials science ,Polymers and Plastics ,Organic Chemistry ,Nanoparticle ,Emulsion polymerization ,Methacrylate ,Lower critical solution temperature ,Inorganic Chemistry ,Crystallography ,chemistry.chemical_compound ,chemistry ,Phase (matter) ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Methyl methacrylate - Abstract
These studies show synthesis of triphasic size- and Janus balance (JB)-tunable nanoparticles (JNPs) utilizing a two-step emulsion polymerization of pentafluorostyrene (PFS) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) and n-butyl acrylate (nBA) in the presence of poly(methyl methacrylate (MMA)/nBA) nanoparticle seeds. Each JNP consists of three phase-separated copolymers: p(MMA/nBA) core, temperature, and pH-responsive (p(DMAEMA/nBA)) phase capable of reversible size and shape changes, and shape-adoptable (p(PFS/nBA)) phase. Due to built-in second-order lower critical solution temperature (II-LCST) transition of p(DMAEMA/nBA) copolymer, macromolecular segments collapse when temperature increases from 30 to 45 °C, resulting in size and shape changes. The p(DMAEMA/nBA) and p(MMA/nBA) phases within each JNP assume concave, flat, or convex shapes, forcing p(PFS/nBA) phase to adopt convex, planar, or concave interfacial curvatures, respectively. As a result, the JB can be tuned from 3.78 to 0.72. The prese...
- Published
- 2022
41. Measurement of wave propagation through a tube using dual transducers for elastography in arteries
- Author
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Hyoung-Ki Lee, Charles B Capron, Hsiao-Chuan Liu, Tuhin Roy, Murthy N Guddati, James F Greenleaf, and Matthew W Urban
- Subjects
Motion ,Radiological and Ultrasound Technology ,Phantoms, Imaging ,Transducers ,Elasticity Imaging Techniques ,Radiology, Nuclear Medicine and imaging ,Arteries - Abstract
Objective. Measuring waves induced with acoustic radiation force (ARF) in arteries has been studied over the last decade. To date, it remains a challenge to quantitatively assess the local arterial biomechanical properties. The cylindrical shape and waveguide behavior of waves propagating in the arterial wall pose complexities to determining the mechanical properties of the artery. Approach. In this paper, an artery-mimicking tube in water is examined utilizing three-dimensional measurements. The cross-section of the tube is measured while a transducer is translated over 41 different positions along the length of the tube. Motion in the radial direction is calculated using two components of motion which are measured from the two orthogonal views of the cross-section. This enables more accurate estimation of motion along the circumference of tube. Main results. The results provide more information to categorize the motion in tube wall into two types of responses: a transient response and a steady state response. The transient response is caused by ARF application and the waves travel along the length of the tube for a relatively short period of time. This corresponds to the axial and circumferential propagating waves. The two circumferential waves travel along the circumference of tube in CW (clockwise) and CCW (counter-clockwise) direction and result in a standing wave. By using a directional filter, the two waves were successfully separated, and their propagation was more clearly visualized. As a steady state response, a circumferential mode is generated showing a symmetric motion (i.e. the proximal and distal walls move in the opposite direction) following the transient response. Significance. This study provides a more comprehensive understanding of the waves produced in an artery-mimicking tube with ARF application, which will provide opportunities for improving measurement of arterial mechanical properties.
- Published
- 2022
42. 1α,25-Dihydroxyvitamin D3 Encapsulated in Nanoparticles Prevents Venous Neointimal Hyperplasia and Stenosis in Porcine Arteriovenous Fistulas
- Author
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Avishek K. Singh, Thanila A. Macedo, Chuanqi Cai, Ravinder J. Singh, Sanjay Misra, Chenglei Zhao, Sreenivasulu Kilari, Matthew W. Urban, Michael L. Simeon, Hyunjoon Kong, Elazer R. Edelman, Edwin A. Takahashi, and Rajiv Kumar
- Subjects
Neointimal hyperplasia ,Pathology ,medicine.medical_specialty ,medicine.diagnostic_test ,Chemistry ,Hemodynamics ,Lumen (anatomy) ,General Medicine ,medicine.disease ,Stenosis ,medicine.anatomical_structure ,Restenosis ,Nephrology ,Fibrosis ,Adventitia ,Angiography ,medicine - Abstract
Background Few therapies prevent venous neointimal hyperplasia (VNH) and venous stenosis (VS) formation in arteriovenous fistulas (AVF). Expression of the immediate early response gene X-1 (Iex-1), also known as Ier3, is associated with VNH and stenosis in murine AVFs. The study aimed to determine if local release of Ier3 long-acting inhibitor 1α,25(OH)2D3 from poly(lactic-co-glycolic acid) (PLGA) nanoparticles embedded in a thermosensitive Pluronic F127 hydrogel (1,25 NP) could affect VNH/VS formation in a large animal model. Methods Immediately after AVF creation in a porcine model of renal failure, 1,25 NP or vehicle control was injected into the adventitia space of AVF outflow veins. Scanning electron microscopy and dynamic light scattering characterized drug and control nanoparticles. Animals were sacrificed 3 and 28 days later for gene expression, immunohistologic, magnetic resonance imaging and angiography, and ultrasound analyses. Whole transcriptome RNA sequencing with differential gene expression analysis was performed on outflow veins of AVF. Results Encapsulation of 1α,25(OH)2D3 in PLGA nanoparticles formed nanoparticles of uniform size that were similar to nanoparticles without 1α,25(OH)2D3. The 1,25 NP-treated AVFs exhibited lower VNH/VS, Ier3 gene expression, and IER-3, MCP-1, CD68, HIF-1α, and VEGF-A immunostaining, fibrosis, and proliferation. Blood flow and lumen area increased significantly, whereas peak systolic velocity and wall shear stress decreased. Treatment increased Young's modulus and correlated with histologic assessment of fibrosis and with no evidence of vascular calcification. RNA sequencing analysis showed changes in the expression of genes associated with inflammatory, TGFβ1, and apoptotic pathways. Conclusions Local release of 1,25 NP improves AVF flow and hemodynamics, and reduces stenosis in association with reduction in inflammation, apoptosis, and fibrosis in a porcine model of arteriovenous fistula.
- Published
- 2021
43. Radiological Society of North America/Quantitative Imaging Biomarker Alliance Shear Wave Speed Bias Quantification in Elastic and Viscoelastic Phantoms
- Author
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Brian S. Garra, Pengfei Song, Timothy J. Hall, Todd N. Erpelding, Stephen J. Rosenzweig, Stephen A. McAleavey, Mark L. Palmeri, Matthew W. Urban, Richard L. Ehman, Gilles Guenette, Glen McLaughlin, Mathieu Couade, Véronique Miette, Shigao Chen, Ted Lynch, Michael MacDonald, Hua Xie, Paul L. Carson, Manish Dhyani, D. Cody Morris, Lindsey C. Carlson, Yoko Okamura, Derek Y. Chan, Yufeng Deng, Arinc Ozturk, Michael H. Wang, Zaegyoo Hah, Nancy A. Obuchowski, Richard G. Barr, Ned C. Rouze, Jun Chen, Anthony E. Samir, Vijay Shamdasani, Shana Fielding, Keith A. Wear, Andy Milkowski, David J. Napolitano, Bo Qiang, Kathryn R. Nightingale, Ravi Managuli, Siyun Yang, Gee Albert, Kingshuk Roy Choudhury, and Yuling Chen
- Subjects
030219 obstetrics & reproductive medicine ,Radiological and Ultrasound Technology ,Phantoms, Imaging ,business.industry ,Ultrasound ,Article ,Elasticity ,Viscoelasticity ,Imaging phantom ,030218 nuclear medicine & medical imaging ,Magnetic resonance elastography ,Shear (sheet metal) ,03 medical and health sciences ,0302 clinical medicine ,North America ,Elasticity Imaging Techniques ,Humans ,Medicine ,Radiology, Nuclear Medicine and imaging ,Ultrasonic sensor ,Elasticity (economics) ,business ,Acoustic radiation force ,Biomarkers ,Biomedical engineering - Abstract
OBJECTIVES—: To quantify the bias of shear wave speed (SWS) measurements between different commercial ultrasonic shear elasticity systems and a magnetic resonance elastography (MRE) system in elastic and viscoelastic phantoms. METHODS—: Two elastic phantoms, representing healthy through fibrotic liver, were measured with 5 different ultrasound platforms, and 3 viscoelastic phantoms, representing healthy through fibrotic liver tissue, were measured with 12 different ultrasound platforms. Measurements were performed with different systems at different sites, at 3 focal depths, and with different appraisers. The SWS bias across the systems was quantified as a function of the system, site, focal depth, and appraiser. A single MRE research system was also used to characterize these phantoms using discrete frequencies from 60 to 500 Hz. RESULTS—: The SWS from different systems had mean difference 95% confidence intervals of ±0.145 m/s (±9.6%) across both elastic phantoms and ± 0.340 m/s (±15.3%) across the viscoelastic phantoms. The focal depth and appraiser were less significant sources of SWS variability than the system and site. Magnetic resonance elastography best matched the ultrasonic SWS in the viscoelastic phantoms using a 140 Hz source but had a − 0.27 ± 0.027-m/s (−12.2% ± 1.2%) bias when using the clinically implemented 60-Hz vibration source. CONCLUSIONS—: Shear wave speed reconstruction across different manufacturer systems is more consistent in elastic than viscoelastic phantoms, with a mean difference bias of < ±10% in all cases. Magnetic resonance elastographic measurements in the elastic and viscoelastic phantoms best match the ultrasound systems with a 140-Hz excitation but have a significant negative bias operating at 60 Hz. This study establishes a foundation for meaningful comparison of SWS measurements made with different platforms.
- Published
- 2021
44. Improving group velocity based estimates of arterial stiffness
- Author
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Charles Capron, Tuhin Roy, Murthy Guddati, and Matthew W. Urban
- Subjects
Acoustics and Ultrasonics ,Arts and Humanities (miscellaneous) - Abstract
Arterial stiffness is a predictor of cardiovascular diseases, the leading causes of death worldwide. Ultrasound-based methods that measure arterial wave propagation have promise for evaluating local stiffness in vivo. However, geometric properties of arteries cause dispersion, invalidating typical assumptions underlying the relationship between shear modulus G and group velocity cg, which clinical implementations of ultrasound shear wave elastography do not consider. Here, we examine the dependence of these estimates on geometry and evaluate alternative approaches. Wave motion in the proximal wall of an artery after application of focused acoustic radiation force is simulated with a semi-analytical finite element (SAFE) model, and cg is estimated using a time-to-peak algorithm to determine G with several methods. First, the value of G a clinical scanner would report is calculated assuming a bulk medium. Second, a pulse wave velocity (PWV)-based G estimate is calculated by taking cg = PWV and applying the Moens–Korteweg equation. Third, we develop an interpolation-based method to provide a corrected G estimate using data generated by the SAFE model. Simulation results show severe geometry-dependent bias with the bulk method, which is partially ameliorated with the PWV method and substantially improved with the interpolation approach. Results are validated using arterial phantoms.
- Published
- 2023
45. Using 3D printed structures to evaluate the potential causes of the color Doppler twinkling signature
- Author
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Benjamin Wood, Renc Saracaydin, Christine Lee, and Matthew W. Urban
- Subjects
Acoustics and Ultrasonics ,Arts and Humanities (miscellaneous) - Abstract
The color Doppler twinkling artifact has been attributed to existing microbubbles or cavitation occurring on objects like kidney stones, some breast biopsy markers, and sandpaper. The grooves of helical constructs that twinkle may provide sufficient locations for bubble retention and/or cavitation. We developed six half-cylinders that replicate the geometry of twinkling helical constructs with a micro 3D-printing process to explore how their characteristics relate to twinkling. Four copies of each design including a control were created. The cylinders had pitch (groove-to-groove distance) of 87.5–343 μm and amplitude (groove depth) of 41.5–209 μm. The cylinders were submerged in degassed water and optically imaged before and after ultrasound to visualize bubbles on the cylinders. The cylinders remained submerged while scanning with color Doppler at frequencies from 3.1 to 6.3 MHz with a General Electric Logiq E9 scanner and 9L linear array transducer. Two designs that showed twinkling characteristics were further examined. The presence or absence of bubbles on these designs was confirmed with microscopy, and the resulting twinkling behavior was investigated. This work shows strong evidence that both existing visible bubbles and either cavitation or ultrasound wave interactions with patterned or rough surfaces are significant factors in producing the twinkling signature.
- Published
- 2023
46. Progress in atomic-resolution aberration corrected conventional transmission electron microscopy (CTEM)
- Author
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Knut W. Urban, Juri Barthel, Lothar Houben, Chun-Lin Jia, Lei Jin, Markus Lentzen, Shao-Bo Mi, Andreas Thust, and Karsten Tillmann
- Subjects
ddc:530 ,General Materials Science - Abstract
Transmission electron microscopy is an indispensable tool in modern materials science. It enables the structure of materials to be studied with high spatial resolution, and thus makes a decisive contribution to the fact that it is now possible to understand the microstructure-related physical and chemical characteristics and to correlate these with the macroscopic materials properties. It was tantamount to a paradigm shift when electron microscopy reached atomic resolution in the late 1990s due to the invention of aberration-corrected electron optics. It is now generally accepted practice to perform picometer-scale measurements and chemical analyses with reference to single atomic units. This review has three objectives. Microscopy in atomic dimensions is applied quantum physics. The consequences of this for practical work and for the understanding and application of the results shall be worked out. Typical applications in materials science will be used to show what can be done with this kind of microscopy and where its limitations lie. In the absence of relevant monographs, the aim is to provide an introduction to this new type of electron microscopy and to enable the reader to access the literature in which special issues are addressed. The paper begins with a brief presentation of the principles of optical aberration correction. It then discusses the fundamentals of atomic imaging and covers typical examples of practical applications to problems in modern materials science. It is emphasized that in atomic-resolution electron microscopy the quantitative interpretation of the images must always be based on the solution of the quantum physical and optical problem on a computer.
- Published
- 2023
47. Shear wave elastography: From dispersion matching to full waveform inversion
- Author
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Murthy Guddati, Tuhin Roy, Abdelrahman M. Elmeliegy, and Matthew W. Urban
- Subjects
Acoustics and Ultrasonics ,Arts and Humanities (miscellaneous) - Abstract
Shear Wave Elastography (SWE) involves estimating mechanical properties through inversion, i.e., matching measured and simulated propagation characteristics of shear waves in the tissue. The accuracy of the estimated properties depends significantly on the specific characteristics/responses that are being matched. These could range from simple group velocity to dispersion curves and to full-wave response (particle velocity measurements). Using specific applications of arterial, liver, and tumor elstography, we illustrate that effective SWE is performed by resorting to an inversion approach, or combination of inversion approaches, guided by the underlying physics. To this end, we present inversion approaches ranging from matching dispersion characteristics to matching full waveform responses and provide rationale for choosing the appropriate technique(s) depending on the problem at hand.
- Published
- 2023
48. Crosstalk analysis of comb detection for measuring shear wave propagation
- Author
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Hyungkyi Lee, Philip M. Holmes, James Greenleaf, and Matthew W. Urban
- Subjects
Acoustics and Ultrasonics ,Arts and Humanities (miscellaneous) - Abstract
Applications, such as shear wave elastography and Doppler imaging, require high frame rates. Plane wave compounding (PWC) is widely used for these applications. Comb detection was proposed to combine the high frame rate of PWC and the high signal quality of focused beam scanning. Comb detection transmits multiple focused beams simultaneously to increase the frame rate. These comb beams are scanned laterally to cover the whole region-of-interest. The simultaneous multiple transmission of focused beams causes crosstalk between neighboring beams. Transmit crosstalk is related to the pressure field of transmit beams, and receive crosstalk is determined by the beam profile of receive beamforming. In this study, we varied f-number (F/N) and apodization window and measured their effects on crosstalk based on the pressure field and an arterial wall simulation using Field II. For transmit design, transmit apodization with a Hamming window significantly reduced crosstalk compared to a rectangular window and transmit F/N had little impact on the crosstalk. Regarding receive beamforming, a Hamming window led to lower crosstalk than the rectangular window and F/N from 1 to 5 suppressed crosstalk to below 30 dB. The effects of crosstalk in shear wave motion data from phantom experiments were also analyzed. Comb detection showed less motion artifact than PWC in phantom experiments.
- Published
- 2023
49. Nonlinear least-squares estimation of shear modulus and shear viscosity in viscoelastic media
- Author
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Nicholas A. Bannon, Matthew W. Urban, and Robert J. McGough
- Subjects
Acoustics and Ultrasonics ,Arts and Humanities (miscellaneous) - Abstract
Time-domain estimates of the shear wave speed are obtained by performing cross-correlations or by evaluating the time-to-peak for two laterally separated shear wave particle velocity waveforms, where the distance divided by the propagation time yields an approximate value for the shear wave speed. Challenges associated with these time-domain estimation approaches include increasing errors as the shear viscosity increases and the absence of an estimated value for the shear viscosity parameter which is responsible for the rapid attenuation of shear waves in soft tissue. To obtain a time-domain estimate of the shear viscosity that also provides an estimate for the shear wave speed, a nonlinear least squares estimation approach is applied to three-dimensional (3D) shear wave particle velocities computed for a shear elasticity of 1.5 kPa, shear viscosities of 1, 2, 3, and 4 Pa.s, and a realistic simulated 3D acoustic radiation force excitation. The results show cross-correlations tend to over-estimate the value of the shear wave speed, the nonlinear least squares approach tends to under-estimate the value of the shear wave speed, and the nonlinear least square approach produces more accurate estimates as the shear viscosity increases. Two-dimensional maps of each estimated parameter are also shown.
- Published
- 2023
50. Limitations of the Caputo time-fractional wave equation when applied to shear waves in pig liver
- Author
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Robert J. McGough and Matthew W. Urban
- Subjects
Acoustics and Ultrasonics ,Arts and Humanities (miscellaneous) - Abstract
When applied to compressional waves, the Caputo time-fractional wave equation describes power law attenuation in soft tissue. However, when applied to shear waves, the Caputo wave equation produces some unexpected behavior. To demonstrate examples of the time-domain waveforms generated by this fractional calculus model, the Caputo wave equation is numerically evaluated for multiple orders of the time-fractional derivative between 0 and 1, for an extended range of values for the relaxation time, and for a fixed value of the shear wave speed extracted from ex vivo pig liver. The computed waveforms are then compared to the measured shear wave particle velocities obtained from ex vivo pig liver. These comparisons reveal that the full-width at half maximum (FWHM) of the positive component of the main shear wave particle velocity waveform measured in pig liver is at least an order of magnitude greater than the FWHM obtained from the Caputo wave equation for all parameter combinations evaluated. These preliminary results indicate that the Caputo wave equation produces time-domain waveforms that are inconsistent with measured shear wave data in pig liver and that further efforts are required to establish more effective fractional calculus models for shear waves in soft tissue.
- Published
- 2023
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