39 results on '"Niedermayr T"'
Search Results
2. Ultrahigh energy resolution gamma-ray spectrometers for precision measurements of uranium enrichment
- Author
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Ali, S., Hau, I. D., Niedermayr, T. R., and Friedrich, S.
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- 2008
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3. Development of a Digital Signal Readout System for Large TES Arrays
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Dreyer, J. G., Hennig, W., Tan, H., Niedermayr, T., Breus, D., Drury, O. B., Warburton, W. K., and Friedrich, S.
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- 2008
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4. Unfolding of cryogenic neutron spectra
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Niedermayr, T., Hau, I.D., Burger, A., Roy, U.N., Bell, Z.W., and Friedrich, S.
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- 2007
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5. Six Sigma-driven Automated Plan Check (APC) Tool Enhances Safety and Efficiency in External Beam Radiation Therapy
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Kovalchuk, N., primary, Liu, S., additional, Lim, S., additional, Bertini, J., additional, Bush, K., additional, Lewis, J.M., additional, Pham, D., additional, Yang, Y., additional, Niedermayr, T., additional, Skinner, L., additional, Beadle, B.M., additional, and Xing, L., additional
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- 2020
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6. OC-1036: Intensity Modulated Ir-192 Brachytherapy Using 3D Printed Shielded Applicators
- Author
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Skinner, L., primary, Niedermayr, T., additional, Perl, J., additional, Prionas, N., additional, Benjamin, F., additional, and Kidd, E., additional
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- 2020
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7. Gamma-ray imaging with a coaxial HPGe detector
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Niedermayr, T., Vetter, K., Mihailescu, L., Schmid, G.J., Beckedahl, D., Blair, J., and Kammeraad, J.
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- 2005
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8. Microcalorimeter design for fast-neutron spectroscopy
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Niedermayr, T., Hau, I.D., Miyazaki, T., Terracol, S., Burger, A., Lamberti, V.E., Bell, Z.W., Vujic, J.L., Labov, S.E., and Friedrich, S.
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- 2004
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9. Optimizing Efficiency and Safety in External Beam Radiotherapy Using Automated Plan Check (APC) Tool and Six Sigma Methodology
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Liu, S., primary, Bush, K., additional, Bertini, J., additional, FU, Y., additional, Lewis, J.M., additional, Pham, D., additional, Yang, Y., additional, Niedermayr, T., additional, Skinner, L., additional, Xing, L., additional, Beadle, B.M., additional, Hsu, A., additional, and Kovalchuk, N., additional
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- 2019
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10. A superconducting detector endstation for high-resolution energy-dispersive SR-XRF
- Author
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Friedrich, S., Niedermayr, T., Drury, O., Cunningham, M.F., van den Berg, M.L., Ullom, J.N., Loshak, A., Funk, T., Cramer, S.P., Batteux, J.D., See, E., Frank, M., and Labov, S.E.
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- 2001
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11. Superconducting Detector System for High-Resolution Energy-Dispersive Soft X-Ray Spectroscopy
- Author
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Friedrich, S, primary, Niedermayr, T, additional, Drury, O, additional, Funk, T, additional, Frank, M, additional, Labov, S E, additional, and Cramer, S, additional
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- 2001
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12. Hydrogenated carbon clusters produced by highly charged ion impact on solid C_{84}
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Thomas Schlathölter, Newman, M. W., Niedermayr, T. R., Machicane, G. A., Mcdonald, J. W., Schenkel, T., Ronnie Hoekstra, Hamza, A. V., KVI - Center for Advanced Radiation Technology, and Research unit Astroparticle Physics
- Subjects
SLOW ,SURFACES ,DISTRIBUTIONS ,SPECTRA ,FRAGMENTATION ,C-60 ,EMISSION ,FULLERENE - Abstract
The emission of small (hydrogenated) carbon cluster ions: CnHm+ (n = 2-22) upon highly charged Xeq+ (q = 20- 14) impact on C-84 surfaces is studied by means of time-of-flight secundary ion mass spectrometry. The respective stage of hydrogenation/protonation of a certain carbon cluster ion C-n(+) is a strong indication for its geometrical structure. From the cluster ion yield as a function of cluster size it can be concluded, that the hydrogenation takes place after the initial carbon cluster formation. The carbon clusters seem to be emitted as art entity in agreement with "equilibrium" and "shock wave" models.
- Published
- 2000
13. SU‐E‐T‐234: Use of GafChromic RTQA Film for Head Leakage Tests
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Deufel, C, primary, Remmes, N, additional, Niedermayr, T, additional, and Harms, T, additional
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- 2011
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14. SU-FF-T-594: Effect of IGRT Motivated Margin Reduction in Postprostatectomy IMRT Plans
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Niedermayr, T, primary and Herman, M, additional
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- 2009
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15. TU-FF-A3-03: Individual and Group Setup Margins with KV Imaging for Daily Patient Positioning
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Niedermayr, T, primary and Herman, MG, additional
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- 2008
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16. Radiotherapie bei Patientinnen mit plastischer Rekonstrukton bei Mammakarzinom
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Schratter-Sehn, AU, primary, Brinda-Raitmayr, K, additional, Niedermayr, T, additional, and Deutinger, M, additional
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- 2006
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17. Internal dielectronic excitation in highly charged ions colliding with surfaces
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Machicoane, G. A., primary, Schenkel, T., additional, Niedermayr, T. R., additional, Newmann, M. W., additional, Hamza, A. V., additional, Barnes, A. V., additional, McDonald, J. W., additional, Tanis, J. A., additional, and Schneider, D. H., additional
- Published
- 2002
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18. First-generation hybrid compact Compton imager.
- Author
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Cunningham, M., Burks, M., Chivers, D., Cork, C., Fabris, L., Gunter, D., Krings, T., Lange, D., Hull, E., Mihailescu, L., Nelson, K., Niedermayr, T., Protic, D., Valentine, J., Vetter, K., and Wright, D.
- Published
- 2005
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19. Imaging performance of the Si/Ge hybrid Compton imager.
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Burks, M., Chivers, D., Cork, C., Cunningham, M., Fabris, L., Gunter, D., Hull, E., Lange, D., Manini, H., Mihailescu, L., Nelson, K., Niedermayr, T., Valentine, J., Vetter, K., and Wright, D.
- Published
- 2005
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20. Hollow Atoms Above Dielectrics And Metals.
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Briand, J.P., Daveau, S., Benhachoum, M., Niedermayr, T., Friedrich, S., Xie, Z., Machicoane, G., Hitz, D., Girard, A., and Melin, G.
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IONS ,METALLIC surfaces ,INSULATING materials ,ELECTRON capture ,SURFACES (Physics) - Abstract
Slow highly charged ions approaching surfaces at very close distances (∼nm) are known to capture many electrons in highly excited states forming hollow atoms(1)(2). These hollow atoms quickly decay to their ground states through a long cascade of autoionization processes( Auger transitions) which may be balanced , as these ions are still close to the surface, by a series of electron captures. This actual sequence of many events of capture and autoionization, alternate or not, is not experimentally known to date, and depends on the charge of the ions and of the capture processes which may be very different above metals and insulators. We review in this paper two new experiments on the kinematics of fully decelerated highly charged ions(Ar18+) above dielectric and metal surfaces, and on the behavior of ions of lower charge states (O7+ and Ne9+) above the same surfaces. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2003
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21. The effects of radiation on (1,3,5 - triamino - 2,4,6 - trinitrobenzene) TATB studied by time-of-flight secondary ion mass spectrometry
- Author
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McDonald, J. W., primary, Schenkel, T., additional, Newman, M. W., additional, Overturf, G., additional, Gregg, H., additional, Niedermayr, T. R., additional, Barnes, A. V., additional, Schneider, D. H. G., additional, Mowat, I. A., additional, and Hamza, A. V., additional
- Published
- 2001
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22. A multichannel cryogenic detector system for synchrotron-based x-ray spectroscopy.
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Friedrich, S., Niedermayr, T., Funk, T., Drury, O., van den Berg, M. L., Cunningham, M. F., Ullom, J. N., Loshak, A., Cramer, S. P., Frank, M., and Labov, S. E.
- Subjects
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X-ray spectroscopy , *DETECTORS , *LOW temperature engineering - Abstract
Fluorescence-detected x-ray absorption spectroscopy probes the fine structure of electronic energy levels with sub-eV resolution by scanning a monochromatic synchrotron beam through the corresponding absorption edge and measuring the intensity of the resulting x-ray fluorescence. For dilute samples, grating spectrometers lack the detection efficiency and conventional Si(Li) or Ge detectors often lack the energy resolution to separate the weak fluorescence signal from strong nearby emission lines. We have built a high-resolution, highefficiency cryogenic detector system for synchrotron-based soft x-ray spectroscopy. The sensor is a 3 x 3 array of 200 µm x 200 µm superconducting Nb-A1-A1Ox-A1-Nb tunnel junctions with an energy resolution of ≈15 eV below 1 keV and a total count rate capability of ≈100,000 counts/second. This sensor array is cooled to below 0.4K by a two-stage adiabatic demagnetization refrigerator while held at the end of a 40-cm-long cold finger that can be inserted into a UHV sample chamber for x-ray fluorescence measurements. We present absorption spectra of dilute compounds (≈ 1000 ppm) and will discuss spectrometer performance with respect to the analysis of metalloproteins. [ABSTRACT FROM AUTHOR]
- Published
- 2002
23. X-ray spectroscopy of ion-surface interactions using superconducting tunnel junctions.
- Author
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Niedermayr, T., Friedrich, S., Cunningham, M. F., Frank, M., Briand, J. P., and Labov, S. E.
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X-ray spectroscopy , *DETECTORS , *SEMICONDUCTOR junctions - Abstract
We have conducted low energy X-ray spectroscopy of ion/surface interactions with superconducting tunnel junction (STJ) detectors. The STJ detectors (Nb-Al-AlOx-Al-Nb) developed at the Lawrence Livermore National Laboratory have a high energy resolution and a high count-rate capability. The detectors are operated in an adiabatic demagnetization refrigerator with 60 mK base temperature at the end of a 40 cm long cold finger, which can be inserted into a UHV sample chamber connected to an ion source. We have studied the . interaction of Ar[sup +], O[sup 7+], N[sup 6+] and C[sup 5+] with various targets (Au, SiH and SiO[sub 2]) at a kinetic energy of 10 keV/q. The resolution of 12-15 eV below 1 keV allows the different satellite lines emitted by these ions to be separated. [ABSTRACT FROM AUTHOR]
- Published
- 2002
24. Deposition of Potential Energy in Solids by Slow, Highly Charged Ions
- Author
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Schenkel, T., primary, Barnes, A. V., additional, Niedermayr, T. R., additional, Hattass, M., additional, Newman, M. W., additional, Machicoane, G. A., additional, McDonald, J. W., additional, Hamza, A. V., additional, and Schneider, D. H., additional
- Published
- 1999
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25. Charge Equilibration Time of Slow, Highly Charged Ions in Solids
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Hattass, M., primary, Schenkel, T., additional, Hamza, A. V., additional, Barnes, A. V., additional, Newman, M. W., additional, McDonald, J. W., additional, Niedermayr, T. R., additional, Machicoane, G. A., additional, and Schneider, D. H., additional
- Published
- 1999
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26. Electronic sputtering of solids by slow, highly charged ions: Fundamentals and applications
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Schenkel, T., Newman, M. W., Niedermayr, T. R., Machicoane, G. A., McDonald, J. W., Barnes, A. V., Hamza, A. V., Banks, J. C., Doyle, B. L., and Wu, K. J.
- Published
- 2000
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27. High energy resolution fast-neutron spectrometers
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Hau, I. D., Niedermayr, T., Bell, Z. W., Lamberti, V. E., Burger, A., Roy, U., and Stephan Friedrich
28. Auto-delineation of treatment target volume for radiation therapy using large language model-aided multimodal learning.
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Rajendran P, Chen Y, Qiu L, Niedermayr T, Liu W, Buyyounouski M, Bagshaw H, Han B, Yang Y, Kovalchuk N, Gu X, Hancock S, Xing L, and Dai X
- Abstract
Purpose: Artificial intelligence (AI)-aided methods have made significant progress in the auto-delineation of normal tissues. However, these approaches struggle with the auto-contouring of radiotherapy target volume. Our goal is to model the delineation of target volume as a clinical decision-making problem, resolved by leveraging large language model-aided multimodal learning approaches., Methods and Materials: A vision-language model, termed Medformer, has been developed, employing the hierarchical vision transformer as its backbone, and incorporating large language models to extract text-rich features. The contextually embedded linguistic features are seamlessly integrated into visual features for language-aware visual encoding through the visual language attention module. Metrics, including Dice similarity coefficient (DSC), intersection over union (IOU), and 95th percentile Hausdorff distance (HD95), were used to quantitatively evaluate the performance of our model. The evaluation was conducted on an in-house prostate cancer dataset and a public oropharyngeal carcinoma (OPC) dataset, totaling 668 subjects., Results: Our Medformer achieved a DSC of 0.81 ± 0.10 versus 0.72 ± 0.10, IOU of 0.73 ± 0.12 versus 0.65 ± 0.09, and HD95 of 9.86 ± 9.77 mm versus 19.13 ± 12.96 mm for delineation of gross tumor volume (GTV) on the prostate cancer dataset. Similarly, on the OPC dataset, it achieved a DSC of 0.77 ± 0.11 versus 0.72 ± 0.09, IOU of 0.70 ± 0.09 versus 0.65 ± 0.07, and HD95 of 7.52 ± 4.8 mm versus 13.63 ± 7.13 mm, representing significant improvements (p < 0.05). For delineating the clinical target volume (CTV), Medformer achieved a DSC of 0.91 ± 0.04, IOU of 0.85 ± 0.05, and HD95 of 2.98 ± 1.60 mm, comparable to other state-of-the-art algorithms., Conclusions: Auto-delineation of the treatment target based on multimodal learning outperforms conventional approaches that rely purely on visual features. Our method could be adopted into routine practice to rapidly contour CTV/GTV., Competing Interests: Declaration of competing interest None, (Copyright © 2024. Published by Elsevier Inc.)
- Published
- 2024
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29. Design approach and benefits of the 3D-printed vaginal individualized applicator (VIA).
- Author
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Ewongwo A, Niedermayr T, and Kidd EA
- Subjects
- Humans, Female, Uterine Cervical Neoplasms radiotherapy, Equipment Design, Middle Aged, Aged, Adult, Needles, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted methods, Brachytherapy instrumentation, Brachytherapy methods, Printing, Three-Dimensional, Vagina
- Abstract
Purpose: Interstitial gynecologic brachytherapy necessitates precise needle placement, requiring time and expertise. We aimed to simplify interstitial procedures and facilitate optimal needle distribution with individualized vaginal templates to guide interstitial needles., Materials/methods: We developed the 3D-printed vaginal individualized applicator (VIA), a cylindrical template containing individualized internal channels that guide interstitial needles to cover the tumor extent. Eight patients underwent VIA only interstitial implants (VIA only), and five intact cervical cases were treated using tandem and customized VIA (VIA + T). Procedure length, number of needles utilized and dosimetric measures were evaluated., Results: VIA was successfully designed and used clinically for 24 procedures (8 VIA only, 16 VIA + T). Average procedure needle insertion time reduced from 80.9 min for traditional interstitial to 42.9 min for VIA only, approximately 47% shorter with a similar mean high risk CTV volume (28.3 cc VIA only vs. 32.4 cc) and excellent dosimetry with average CTV V100% (94.3% and 94.4%). VIA + T was particularly useful in patients with small vaginal canals and large tumor size. For the five VIA + T patients average tumor size was 68.0cc (range 26.6-143.5 cc). VIA + T procedures were approximately 20% shorter than hybrid procedures with other applicators with mean length of 20.1 min and an average of 6.8 needles (range 3-12)., Conclusion: Our novel 3D-printed VIA facilitates gynecologic interstitial brachytherapy by simplifying needle placement, reducing procedure time, and maintaining excellent dosimetry. VIA can be customized for various clinical scenarios, particularly beneficial for large tumors or small vaginal canals., (Copyright © 2024 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2024
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30. Development and clinical implementation of simple needle attachment post placement interstitial template (SNAPP-IT) enabling a shorter, more direct needle path while preserving tumor visualization.
- Author
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Baniel CC, Hui C, Franco PA, Niedermayr T, and Kidd EA
- Subjects
- Female, Humans, Vagina diagnostic imaging, Needles, Radiotherapy Dosage, Brachytherapy methods, Genital Neoplasms, Female diagnostic imaging, Genital Neoplasms, Female radiotherapy, Vaginal Neoplasms
- Abstract
Purpose: Historical gynecologic interstitial brachytherapy templates block direct tumor visualization during needle placement, presenting an opportunity for clinical innovation to develop a novel interstitial template allowing direct tumor visualization during needle insertion., Methods and Materials: We designed and implemented a novel interstitial template, simple needle attachment post placement interstitial template (SNAPP-IT), that allowed direct visualization of the target vaginal tumor during interstitial needle placement while maintaining the ability to individually secure needles to the template, allow a vaginal cylinder, suture holes for securing to the perineum, MRI compatibility and sterilizable for repeat use. Procedure outcomes including procedure time, needle path lengths, and plan dosimetry were prospectively captured in a patient database., Results: Forty gynecologic interstitial brachytherapy cases were recorded (20 SNAPP-IT, 20 traditional templates). Needle insertion depth was reduced using the SNAPP-IT in comparison with traditional interstitial templates (11.8 cm vs. 3.6 cm, p < 0.0001). The average CTV volume was 25.6 cc for SNAPP-IT and 20.7 cc for traditional; both methods averaged a similar number of needles (15.8, 15.6). Dosimetric constraints were similarly met in both treatment groups. Procedures performed using the SNAPP-IT were shorter compared with those performed with traditional interstitial devices (83.4 minutes vs. 100.7 minutes) and there were no post-operative infections in the SNAPP-IT group., Conclusions: Implementation of a novel gynecologic interstitial brachytherapy template (SNAPP-IT) reduced procedure times, allowed direct tumor visualization, and decreased needle insertion depth. SNAPP-IT provides a useful alternative approach for vaginal interstitial brachytherapy, may increase brachytherapist efficiency with complex procedures and potentially expands access to interstitial brachytherapy., (Copyright © 2023 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2024
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31. Developing Next-Generation 3-Dimensional Printing for Cervical Cancer Hybrid Brachytherapy: A Guided Interstitial Technique Enabling Improved Flexibility, Dosimetry, and Efficiency.
- Author
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Marar M, Niedermayr T, and Kidd EA
- Subjects
- Female, Humans, Retrospective Studies, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted methods, Printing, Three-Dimensional, Uterine Cervical Neoplasms diagnostic imaging, Uterine Cervical Neoplasms radiotherapy, Brachytherapy methods
- Abstract
Purpose: We developed a 3-dimensionally (3D) printed tandem anchored radially guiding interstitial template (TARGIT) to increase the simplicity of intracavitary/interstitial technique for tandem-and-ovoid (T&O) procedures in cervical cancer brachytherapy. This study compared dosimetry and procedure logistics between T&O implants using the original TARGIT versus the next-generation TARGIT-Flexible-eXtended (TARGIT-FX) 3D-printed template designed for practice-changing ease-of-use with further simplified needle insertion and increased flexibility in needle placement., Methods and Materials: This single-institution retrospective cohort study included patients undergoing T&O brachytherapy as part of definitive cervical cancer treatment. Procedures used the original TARGIT from November 2019 through February 2022 and the TARGIT-FX from March 2022 through November 2022. The FX design features full extension to the vaginal introitus with 9 needle channels and allows for needle additions or depth adjustments intraprocedure and after computed tomography/magnetic resonance imaging., Results: A total of 148 implants were performed, 68 (46%) with TARGIT and 80 (54%) with TARGIT-FX, across 41 patients. Across implants, the TARGIT-FX achieved higher mean V100% (+2.8%, P = .0019), and across patients, the TARGIT-FX achieved higher D90 (+2.0 Gy, P = .037) and higher D98 (+2.7 Gy, P = .016) compared with the original TARGIT. Doses to organs at risk were overall similar between templates. Procedure times for TARGIT-FX implants were 30% shorter on average than for those using the original TARGIT (P < .0001), and 28% shorter on average for the subset of implants with high-risk clinical target volume ≥30 cc (P = .013). All residents (100%, N = 6) surveyed regarding the TARGIT-FX indicated ease-of-use for needle insertion and interest in applying the technique in future practice., Conclusions: The TARGIT-FX achieved shorter procedure times with increased tumor coverage and similar normal tissue sparing compared with the previously applied TARGIT and illustrates the potential of 3D printing to enhance efficiency and shorten the learning curve for intracavitary/interstitial procedure technique in cervical cancer brachytherapy., (Copyright © 2023 Elsevier Inc. All rights reserved.)
- Published
- 2023
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32. Radio-luminescent imaging for rapid, high-resolution eye plaque loading verification.
- Author
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Yan H, De Jean P, Grafil E, Ashraf R, Niedermayr T, Astrahan M, Mruthyunjaya P, Beadle B, Xing L, and Liu W
- Subjects
- Humans, Iodine Radioisotopes therapeutic use, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted methods, Monte Carlo Method, Radiometry methods, Brachytherapy methods, Eye Neoplasms radiotherapy
- Abstract
Background: Eye plaque brachytherapy is currently an optimal therapy for intraocular cancers. Due to the lack of an effective and practical technique to measure the seed radioactivity distribution, current quality assurance (QA) practice according to the American Association of Physicists in Medicine TG129 only stipulates that the plaque assembly be visually inspected. Consequently, uniform seed activity is routinely adopted to avoid possible loading mistakes of differential seed loading. However, modulated dose delivery, which represents a general trend in radiotherapy to provide more personalized treatment for a given tumor and patient, requires differential activities in the loaded seeds., Purpose: In this study, a fast and low-cost radio-luminescent imaging and dose calculating system to verify the seed activity distribution for differential loading was developed., Methods: A proof-of-concept system consisting of a thin scintillator sheet coupled to a camera/lens system was constructed. A seed-loaded plaque can be placed directly on the scintillator surface with the radioactive seeds facing the scintillator. The camera system collects the radioluminescent signal generated by the scintillator on its opposite side. The predicted dose distribution in the scintillator's sensitive layer was calculated using a Monte Carlo simulation with the planned plaque loading pattern of I-125 seeds. Quantitative comparisons of the distribution of relative measured signal intensity and that of the relative predicted dose in the sensitive layer were performed by gamma analysis, similar to intensity-modulated radiation therapy QA., Results: Data analyses showed high gamma (3%/0.3 mm, global, 20% threshold) passing rates for correct seed loadings and low passing rates with distinguished high gamma value area for incorrect loadings, indicating that possible errors may be detected. The measurement and analysis only required a few extra minutes, significantly shorter than the time to assay the extra verification seeds the physicist already must perform as recommended by TG129., Conclusions: Radio-luminescent QA can be used to facilitate and assure the implementation of intensity-modulated, customized plaque loading., (© 2022 American Association of Physicists in Medicine.)
- Published
- 2023
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33. Applying 3D-Printed Templates in High-Dose-Rate Brachytherapy for Cervix Cancer: Simplified Needle Insertion for Optimized Dosimetry.
- Author
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Marar M, Simiele E, Niedermayr T, and Kidd EA
- Subjects
- Female, Humans, Printing, Three-Dimensional, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted methods, Retrospective Studies, Brachytherapy methods, Uterine Cervical Neoplasms pathology, Uterine Cervical Neoplasms radiotherapy
- Abstract
Purpose: In cervical cancer brachytherapy, adding interstitial needles to intracavitary applicators can enhance dosimetry by improving target coverage while limiting normal tissue dose. However, its use is limited to a subset of practitioners with appropriate technical skill. We designed tandem anchored radially guiding interstitial templates (TARGITs) with a 3-dimensional (3D) printing workflow to optimize needle placement and facilitate greater ease-of-use of intracavitary/interstitial (IC/IS) technique. This study compared dosimetry and procedure characteristics between tandem and ovoid (T&O) implants using TARGIT technique versus non-TARGIT technique., Methods and Materials: This single-institution retrospective cohort study included patients undergoing T&O brachytherapy as part of definitive radiation treatment for cervical cancer between February 2017 and January 2021. TARGIT technique was implemented from November 2019 onwards; all prior procedures involved non-TARGIT technique using a no needle or freehand needle approach. Target coverage, dose to organs at risk, and procedure times were evaluated and compared between TARGIT technique and non-TARGIT technique., Results: The cohort included 70 patients with cervical cancer who underwent 302 T&O procedures: 68 (23%) with TARGIT technique and 234 (77%) with non-TARGIT technique, which included 133 no needle and 101 freehand needle implants. TARGIT implants involved longer average procedure times (+6.3 minutes, P < .0001). TARGIT implants achieved a higher mean high-risk clinical target volume V100% than non-TARGIT implants (+4.4%, P = .001), including for large tumors 30 cm
3 or greater (+8.1%, P = .002). Average D90 was 4.6 Gy higher and average D98 was 3.2 Gy higher for TARGIT technique compared with non-TARGIT technique (P = .006 and P = .02). Total treatment doses to rectum, bowel, and bladder were not significantly different for TARGIT versus non-TARGIT technique., Conclusions: The 3D-printed TARGIT approach to T&O brachytherapy achieved greater tumor coverage while sparing normal tissues, particularly for large tumor volumes, with only a slight increase in average procedure time. TARGIT represents a creative technological solution for increasing accessibility of advanced IC/IS brachytherapy technique for cervical cancer definitive radiation treatment., (Copyright © 2022 Elsevier Inc. All rights reserved.)- Published
- 2022
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34. MR to ultrasound image registration with segmentation-based learning for HDR prostate brachytherapy.
- Author
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Chen Y, Xing L, Yu L, Liu W, Pooya Fahimian B, Niedermayr T, Bagshaw HP, Buyyounouski M, and Han B
- Subjects
- Humans, Image Processing, Computer-Assisted, Magnetic Resonance Imaging, Male, Ultrasonography, Brachytherapy, Prostatic Neoplasms diagnostic imaging, Prostatic Neoplasms radiotherapy
- Abstract
Purpose: Propagation of contours from high-quality magnetic resonance (MR) images to treatment planning ultrasound (US) images with severe needle artifacts is a challenging task, which can greatly aid the organ contouring in high dose rate (HDR) prostate brachytherapy. In this study, a deep learning approach was developed to automatize this registration procedure for HDR brachytherapy practice., Methods: Because of the lack of training labels and difficulty of accurate registration from inferior image quality, a new segmentation-based registration framework was proposed for this multi-modality image registration problem. The framework consisted of two segmentation networks and a deformable registration network, based on the weakly -supervised registration strategy. Specifically, two 3D V-Nets were trained for the prostate segmentation on the MR and US images separately, to generate the weak supervision labels for the registration network training. Besides the image pair, the corresponding prostate probability maps from the segmentation were further fed to the registration network to predict the deformation matrix, and an augmentation method was designed to randomly scale the input and label probability maps during the registration network training. The overlap between the deformed and fixed prostate contours was analyzed to evaluate the registration accuracy. Three datasets were collected from our institution for the MR and US image segmentation networks, and the registration network learning, which contained 121, 104, and 63 patient cases, respectively., Results: The mean Dice similarity coefficient (DSC) results of the two prostate segmentation networks are 0.86 ± 0.05 and 0.90 ± 0.03, for MR images and the US images after the needle insertion, respectively. The mean DSC, center-of-mass (COM) distance, Hausdorff distance (HD), and averaged symmetric surface distance (ASSD) results for the registration of manual prostate contours were 0.87 ± 0.05, 1.70 ± 0.89 mm, 7.21 ± 2.07 mm, 1.61 ± 0.64 mm, respectively. By providing the prostate probability map from the segmentation to the registration network, as well as applying the random map augmentation method, the evaluation results of the four metrics were all improved, such as an increase in DSC from 0.83 ± 0.08 to 0.86 ± 0.06 and from 0.86 ± 0.06 to 0.87 ± 0.05, respectively., Conclusions: A novel segmentation-based registration framework was proposed to automatically register prostate MR images to the treatment planning US images with metal artifacts, which not only largely saved the labor work on the data preparation, but also improved the registration accuracy. The evaluation results showed the potential of this approach in HDR prostate brachytherapy practice., (© 2021 American Association of Physicists in Medicine.)
- Published
- 2021
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35. Intensity modulated Ir-192 brachytherapy using high-Z 3D printed applicators.
- Author
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Skinner LB, Niedermayr T, Prionas N, Perl J, Fahimian B, and Kidd EA
- Subjects
- Algorithms, Female, Humans, Monte Carlo Method, Plastics, Radiometry, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted, Tungsten, Brachytherapy instrumentation, Iridium Radioisotopes therapeutic use, Printing, Three-Dimensional, Radiotherapy, Intensity-Modulated instrumentation
- Abstract
Gynecologic cancers are often asymmetric, yet current Ir-192 brachytherapy techniques provide only limited radial modulation of the dose. The shielded solutions investigated here solve this by providing the ability to modulate between highly asymmetric and radially symmetric dose distributions at a given location. To find applicator designs that can modulate between full dose and less than 50% dose, at the dimensions of the urethra, a 2D calculation algorithm was developed to narrow down the search space. Two shielding design types were then further investigated using Monte Carlo and Boltzmann-solver dose calculation algorithms. 3D printing techniques using ISO 10993 certified biocompatible plastics and 3D printable tungsten-loaded plastics were tested. It was also found that shadowing effects set by the shape of the shielding cannot be easily modulated out, hence careful design is required. The shielded applicator designs investigated here, allow for reduction of the dose by over 50% at 5 mm from the applicator surface in desired regions, while also allowing radially symmetric dose with isodose line deviations less than 0.5 mm from circular. The shielding designs were also chosen with treatment delivery time in mind. Treatment times for these shielded designs were found to be less than 1.4 times longer than a 6-channel unshielded cylinder for the equivalent fully symmetric dose distribution. The 2D calculation methods developed here provide a simple way to rapidly evaluate shielding designs, while the 3D printing techniques also allow for devices with novel shapes to be rapidly prototyped. Both TOPAS Monte Carlo and Acuros BV calculations show that significant dose shaping and organ at risk sparing can be achieved without significantly compromising the plan in regions that require the full dose.
- Published
- 2020
- Full Text
- View/download PDF
36. Factor 10 Expedience of Monthly Linac Quality Assurance via an Ion Chamber Array and Automation Scripts.
- Author
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Skinner LB, Yang Y, Hsu A, Xing L, Yu AS, and Niedermayr T
- Subjects
- Automation, Humans, Radiometry, Reproducibility of Results, Time Factors, Particle Accelerators instrumentation, Particle Accelerators standards, Quality Assurance, Health Care methods, Quality Assurance, Health Care standards
- Abstract
Purpose: While critical for safe and accurate radiotherapy, monthly quality assurance of medical linear accelerators is time-consuming and takes physics resources away from other valuable tasks. The previous methods at our institution required 5 hours to perform the mechanical and dosimetric monthly linear accelerator quality assurance tests. An improved workflow was developed to perform these tests with higher accuracy, with fewer error pathways, in significantly less time., Methods: A commercial ion chamber array (IC profiler, Sun Nuclear, Melbourne, Florida) is combined with automation scripts to consolidate monthly linear accelerator QA. The array was used to measure output, flatness, symmetry, jaw positions, gated dose constancy, energy constancy, collimator walkout, crosshair centering, and dosimetric leaf gap constancy. Treatment plans were combined with automation scripts that interface with Sun Nuclear's graphical user interface. This workflow was implemented on a standard Varian clinac, with no special adaptations, and can be easily applied to other C-arm linear accelerators., Results: These methods enable, in 30 minutes, measurement and analysis of 20 of the 26 dosimetric and mechanical monthly tests recommended by TG-142. This method also reduces uncertainties in the measured beam profile constancy, beam energy constancy, field size, and jaw position tests, compared to our previous methods. One drawback is the increased uncertainty associated with output constancy. Output differences between IC profiler and farmer chamber in plastic water measurements over a 6-month period, across 4 machines, were found to have a 0.3% standard deviation for photons and a 0.5% standard deviation for electrons, which is sufficient for verifying output accuracy according to TG-142 guidelines. To minimize error pathways, automation scripts which apply the required settings, as well as check the exported data file integrity were employed., Conclusions: The equipment, procedure, and scripts used here reduce the time burden of routine quality assurance tests and in most instances improve precision over our previous methods.
- Published
- 2019
- Full Text
- View/download PDF
37. Dosimetric quality and evolution of edema after low-dose-rate brachytherapy for small prostates: implications for the use of newer isotopes.
- Author
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Kovtun KA, Wolfsberger L, Niedermayr T, Sugar EN, Graham PL, Murciano-Goroff Y, Beard C, D'Amico AV, Martin NE, Orio PF, and Nguyen PL
- Subjects
- Aged, Brachytherapy methods, Humans, Iodine Radioisotopes adverse effects, Iodine Radioisotopes therapeutic use, Magnetic Resonance Imaging, Male, Middle Aged, Organ Size, Radiometry, Rectum, Retrospective Studies, Urethra, Brachytherapy adverse effects, Edema etiology, Prostate anatomy & histology, Prostatic Neoplasms radiotherapy, Radiation Injuries
- Abstract
Purpose: To characterize prostate swelling and dosimetry in patients with small prostate volumes (PVs) undergoing brachytherapy., Methods and Materials: We studied 25 patients with PV <25 cc (range, 15.1-24.8) and 65 patients with PV ≥25 cc (range, 25.0-66.2) based on three-dimensional ultrasound contours who underwent brachytherapy monotherapy with intraoperative planning. Postoperative Days 1 and 30 dosimetry was done by CT-MRI fusion., Results: Small PVs had greater Day 1 swelling than large PVs (32.5% increase in volume vs. 23.7%, p = 0.04), but by Day 30, swelling was minimal and not significantly different (p = 0.44). Small PVs had greater seed and needle densities at implant (p < 0.001). Rectal and urethral doses were nearly identical by Day 30 (small PV rectum receiving 100% of the prescription dose [145 Gy] [V100] = 0.32 cc; large PV rectum V100 = 0.33 cc, p = 0.99; small PV urethra receiving 150% of the prescription dose [145 Gy] [V150] = 0.20, large PV urethra V150 = 0.20, p = 0.91). Swelling at Day 1 created some cool implants (rate dose that covers 90% of the prostate volume [D90 <140 Gy = 12.0% and 9.4% for the small and large PV groups, respectively, p = 0.71), but Day 30 planning target volume coverage was excellent (rate D90 <140 Gy = 0% for both groups)., Conclusions: Although smaller prostates have greater Day 1 swelling, good Day 30 dosimetry can be achieved, making them excellent candidates for (125)I seeds (half-life [t½] = 60 days). Smaller prostates may be suboptimal for shorter t½ sources such as (131)Cs (t½ = 9.7 days), in which the majority of the dose may be delivered to an edematous gland, unless the planning is adjusted to anticipate the edema., (Copyright © 2014 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2014
- Full Text
- View/download PDF
38. Cine EPID evaluation of two non-commercial techniques for DIBH.
- Author
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Jensen C, Urribarri J, Cail D, Rottmann J, Mishra P, Lingos T, Niedermayr T, and Berbeco R
- Subjects
- Breast Neoplasms physiopathology, Electrical Equipment and Supplies, Humans, Lasers, Breast Neoplasms radiotherapy, Breath Holding, Molecular Imaging instrumentation, Radiotherapy, Image-Guided instrumentation
- Abstract
Purpose: To evaluate the efficacy of two noncommercial techniques for deep inspiration breathhold (DIBH) treatment of left-sided breast cancer (LSBC) using cine electronic portal imaging device (EPID) images., Methods: 23,875 EPID images of 65 patients treated for LSBC at two different cancer treatment centers were retrieved. At the Milford Regional Cancer Center, DIBH stability was maintained by visual alignment of inroom lasers and patient skin tattoos (TAT). At the South Shore Hospital, a distance-measuring laser device (RTSSD) was implemented. For both centers,cine EPID images were acquired at least once per week during beam-on. Chest wall position relative to image boundary was measured and tracked over the course of treatment for every patient and treatment fraction for which data were acquired., Results: Median intrabeam chest motion was 0.31 mm for the TAT method and 0.37 mm for the RTSSD method. The maximum excursions exceeded our treatment protocol threshold of 3 mm in 0.3% of cases (TAT) and 1.2% of cases (RTSSD). The authors did not observe a clinically significant difference between the two datasets., Conclusions: Both noncommercial techniques for monitoring the DIBH location provided DIBH stability within the predetermined treatment protocol parameters (<3 mm). The intreatment imaging offered by the EPID operating in cine mode facilitates retrospective analysis and validation of both techniques.
- Published
- 2014
- Full Text
- View/download PDF
39. Using four-dimensional computed tomography images to optimize the internal target volume when using volume-modulated arc therapy to treat moving targets.
- Author
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Yakoumakis N, Winey B, Killoran J, Mayo C, Niedermayr T, Panayiotakis G, Lingos T, and Court L
- Subjects
- Four-Dimensional Computed Tomography, Humans, Organs at Risk, Radiotherapy Dosage, Radiotherapy, Intensity-Modulated, Tumor Burden, Lung Neoplasms radiotherapy, Movement physiology, Radiographic Image Interpretation, Computer-Assisted, Radiotherapy Planning, Computer-Assisted
- Abstract
In this work we used 4D dose calculations, which include the effects of shape deformations, to investigate an alternative approach to creating the ITV. We hypothesized that instead of needing images from all the breathing phases in the 4D CT dataset to create the outer envelope used for treatment planning, it is possible to exclude images from the phases closest to the inhale phase. We used 4D CT images from 10 patients with lung cancer. For each patient, we drew a gross tumor volume on the exhale-phase image and propagated this to the images from other phases in the 4D CT dataset using commercial image registration software. We created four different ITVs using the N phases closest to the exhale phase (where N = 10, 8, 7, 6). For each ITV contour, we created a volume-modulated arc therapy plan on the exhale-phase CT and normalized it so that the prescribed dose covered at least 95% of the ITV. Each plan was applied to CT images from each CT phase (phases 1-10), and the calculated doses were then mapped to the exhale phase using deformable registration. The effect of the motion was quantified using the dose to 95% of the target on the exhale phase (D95) and tumor control probability. For the three-dimensional and 4D dose calculations of the plan where N = 10, differences in the D95 value varied from 3% to 14%, with an average difference of 7%. For 9 of the 10 patients, the reduction in D95 was less than 5% if eight phases were used to create the ITV. For three of the 10 patients, the reduction in the D95 was less than 5% if seven phases were used to create the ITV. We were unsuccessful in creating a general rule that could be used to create the ITV. Some reduction (8/10 phases) was possible for most, but not all, of the patients, and the ITV reduction was small.
- Published
- 2012
- Full Text
- View/download PDF
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