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  1. AU="Ripken, Tammo"
  2. AU="Koekkoek, W A C Kristine"
  3. AU="Hatas, Andrew"
  4. AU="McGregor, T"
  5. AU="De Nisco, Carlo"
  6. AU="Robert A. Harrington"
  7. AU="Xu, Yi-Ming"
  8. AU=Kurokawa Tomohiro
  9. AU="Aggarwal, Samarth"
  10. AU="Lee E. Brown"
  11. AU="Breen, G"
  12. AU="Leung, Tara"

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  1. Artikel ; Online: Imperfect refractive index matching in scanning laser optical tomography and a method for digital correction.

    Hill, Ole / Wollweber, Merve / Biermann, Tobias / Ripken, Tammo / Lachmayer, Roland

    Journal of biomedical optics

    2024  Band 29, Heft 6, Seite(n) 66004

    Abstract: Significance: Scanning laser optical tomography (SLOT) is a volumetric multi-modal imaging technique that is comparable to optical projection tomography and computer tomography. Image quality is crucially dependent on matching the refractive indexes ( ... ...

    Abstract Significance: Scanning laser optical tomography (SLOT) is a volumetric multi-modal imaging technique that is comparable to optical projection tomography and computer tomography. Image quality is crucially dependent on matching the refractive indexes (RIs) of the sample and surrounding medium, but RI matching often requires some effort and is never perfect.
    Aim: Reducing the burden of RI matching between the immersion medium and sample in biomedical imaging is a challenging and interesting task. We aim at implementing a post processing strategy for correcting SLOT measurements that have errors caused by RI mismatch.
    Approach: To better understand the problems with poorly matched Ris, simulated SLOT measurements with imperfect RI matching of the sample and medium are performed and presented here. A method to correct distorted measurements was developed and is presented and evaluated. This method is then applied to a sample containing fluorescent polystyrene beads and a sample made of olydimethylsiloxane with embedded fluorescent nanoparticles.
    Results: From the simulations, it is evident that measurements with an RI mismatch larger than 0.02 and no correction yield considerably worse results compared to perfectly matched measurements. RI mismatches larger than 0.05 make it almost impossible to resolve finer details and structures. By contrast, the simulations imply that a measurement with an RI mismatch of up to 0.1 can still yield reasonable results if the presented correction method is applied. The experiments validate the simulated results for an RI mismatch of about 0.09.
    Conclusions: The method significantly improves the SLOT image quality for samples with imperfectly matched Ris. Although the absolutely best imaging quality will be achieved with perfect RI matching, these results pave the way for imaging in SLOT with RI mismatches while maintaining high image quality.
    Mesh-Begriff(e) Tomography, Optical/methods ; Refractometry/methods ; Image Processing, Computer-Assisted/methods ; Algorithms ; Computer Simulation ; Phantoms, Imaging
    Sprache Englisch
    Erscheinungsdatum 2024-05-15
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 1309154-2
    ISSN 1560-2281 ; 1083-3668
    ISSN (online) 1560-2281
    ISSN 1083-3668
    DOI 10.1117/1.JBO.29.6.066004
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  2. Artikel ; Online: Acoustic stimulation of the human round window by laser-induced nonlinear optoacoustics.

    Lengert, Liza / Tomanek, Michael / Ghoncheh, Mohammad / Lohmann, Hinnerk / Prenzler, Nils / Kalies, Stefan / Johannsmeier, Sonja / Ripken, Tammo / Heisterkamp, Alexander / Maier, Hannes

    Scientific reports

    2024  Band 14, Heft 1, Seite(n) 8214

    Abstract: The feasibility of low frequency pure tone generation in the inner ear by laser-induced nonlinear optoacoustic effect at the round window was demonstrated in three human cadaveric temporal bones (TB) using an integral pulse density modulation (IPDM). ... ...

    Abstract The feasibility of low frequency pure tone generation in the inner ear by laser-induced nonlinear optoacoustic effect at the round window was demonstrated in three human cadaveric temporal bones (TB) using an integral pulse density modulation (IPDM). Nanosecond laser pulses with a wavelength in the near-infrared (NIR) region were delivered to the round window niche by an optical fiber with two spherical lenses glued to the end and a viscous gel at the site of the laser focus. Using IPDM, acoustic tones with frequencies between 20 Hz and 1 kHz were generated in the inner ear. The sound pressures in scala tympani and vestibuli were recorded and the intracochlear pressure difference (ICPD) was used to calculate the equivalent sound pressure level (eq. dB SPL) as an equivalent for perceived loudness. The results demonstrate that the optoacoustic effect produced sound pressure levels ranging from 140 eq. dB SPL at low frequencies ≤ 200 Hz to 90 eq. dB SPL at 1 kHz. Therefore, the produced sound pressure level is potentially sufficient for patients requiring acoustic low frequency stimulation. Hence, the presented method offers a potentially viable solution in the future to provide the acoustic stimulus component in combined electro-acoustic stimulation with a cochlear implant.
    Mesh-Begriff(e) Humans ; Acoustic Stimulation ; Round Window, Ear/physiology ; Sound ; Scala Tympani/physiology ; Lasers ; Cochlea/physiology
    Sprache Englisch
    Erscheinungsdatum 2024-04-08
    Erscheinungsland England
    Dokumenttyp Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-024-58129-0
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  3. Artikel ; Online: Optoacoustic tones generated by nanosecond laser pulses can cover the entire human hearing range.

    Lengert, Liza / Lohmann, Hinnerk / Johannsmeier, Sonja / Ripken, Tammo / Maier, Hannes / Heisterkamp, Alexander / Kalies, Stefan

    Journal of biophotonics

    2022  Band 15, Heft 11, Seite(n) e202200161

    Abstract: The aim of this work is to generate defined tones that cover the human hearing range in aqueous media for a later application in middle or inner ear implants. In our experiments, we investigated the characteristics of single laser pulses and pulse trains ...

    Abstract The aim of this work is to generate defined tones that cover the human hearing range in aqueous media for a later application in middle or inner ear implants. In our experiments, we investigated the characteristics of single laser pulses and pulse trains with different laser repetition rates of nanosecond laser pulses that were focused into aqueous media in a small volume. The frequency of the generated tones was limited by the spectral properties of the single acoustic pulses, which depended on the medium. Tones with fundamental frequencies above 8 kHz were generated using laser pulses focused into water. By replacing water with gel, tones between 500 Hz and 20 kHz could be produced. The generation of tones in the low-frequency range was only possible when laser pulse trains with pulse density modulated pulse patterns were applied in gel. This enabled the generation of tones between 20 Hz and 2 kHz. Consequently, the combination of different pulse patterns for the different frequency ranges allows generating optoacoustic tones between 20 Hz and 20 kHz in gel. Thus, we can cover the complete range of human hearing through optoacoustically generated tones.
    Mesh-Begriff(e) Humans ; Hearing ; Acoustics ; Lasers ; Water
    Chemische Substanzen Water (059QF0KO0R)
    Sprache Englisch
    Erscheinungsdatum 2022-08-16
    Erscheinungsland Germany
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2390063-5
    ISSN 1864-0648 ; 1864-063X
    ISSN (online) 1864-0648
    ISSN 1864-063X
    DOI 10.1002/jbio.202200161
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  4. Artikel: Imaging and quantification of the tumor microenvironment of triple negative breast cancer using TPEF and scanning laser optical tomography.

    Kamin, Hannes / Nolte, Lena / Bleilevens, Andreas / Stickeler, Elmar / Heinemann, Dag / Maurer, Jochen / Johannsmeier, Sonja / Ripken, Tammo

    Biomedical optics express

    2023  Band 14, Heft 9, Seite(n) 4579–4593

    Abstract: Triple-negative breast cancer is an aggressive subtype of breast cancer that has a poor five-year survival rate. The tumor's extracellular matrix is a major compartment of its microenvironment and influences the proliferation, migration and the formation ...

    Abstract Triple-negative breast cancer is an aggressive subtype of breast cancer that has a poor five-year survival rate. The tumor's extracellular matrix is a major compartment of its microenvironment and influences the proliferation, migration and the formation of metastases. The study of such dependencies requires methods to analyze the tumor matrix in its native form. In this work, the limits of SHG-microscopy, namely limited penetration depth, sample size and specificity, are addressed by correlative three-dimensional imaging. We present the combination of scanning laser optical tomography (SLOT) and multiphoton microscopy, to depict the matrix collagen on different scales. Both methods can be used complementarily to generate full-volume views and allow for in-depth analysis. Additionally, we explore the use of SHG as a contrast mechanism for complex samples in SLOT. It was possible to depict the overall collagen structure and specific fibers using marker free imaging on different scales. An appropriate sample preparation enables the fixation of the structures while simultaneously conserving the fluorescence of antibody staining. We find that SHG is a suitable contrast mechanism to depict matrix collagen even in complex samples and using SLOT. The insights presented here shall further facilitate the study of the tumor extracellular matrix by correlative 3d imaging.
    Sprache Englisch
    Erscheinungsdatum 2023-08-10
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 2572216-5
    ISSN 2156-7085
    ISSN 2156-7085
    DOI 10.1364/BOE.494181
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  5. Buch ; Online ; Dissertation / Habilitation: Anwendung von MHz-fs-Lasern in der Ophthalmologie und Erarbeitung eines Therapiekonzeptes für die laserassistierte Behandlung der Alterssichtigkeit

    Ripken, Tammo

    2007  

    Abstract: Femtosekundenlaser, Ultrakurzpulslaser, MHz-Repetitionsraten, Nanojoule, Photodisruption, fs-LASIK, ... ...

    Verfasserangabe von Tammo Ripken
    Abstract Femtosekundenlaser, Ultrakurzpulslaser, MHz-Repetitionsraten, Nanojoule, Photodisruption, fs-LASIK, Presbyopie
    Sprache Deutsch
    Umfang Online-Ressource (153 S. = 51,2 Mb)
    Verlag Technische Informationsbibliothek u. Universitätsbibliothek
    Erscheinungsort Hannover
    Dokumenttyp Buch ; Online ; Dissertation / Habilitation
    Dissertation / Habilitation Univ., Diss.--Hannover, 2007
    Datenquelle Katalog der Technische Informationsbibliothek Hannover

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  6. Buch ; Online ; Dissertation / Habilitation: Anwendung von MHz-fs-Lasern in der Ophthalmologie und Erarbeitung eines Therapiekonzeptes für die laserassistierte Behandlung der Alterssichtigkeit

    Ripken, Tammo

    2007  

    Abstract: Femtosekundenlaser, Ultrakurzpulslaser, MHz-Repetitionsraten, Nanojoule, Photodisruption, fs-LASIK, ... ...

    Verfasserangabe von Tammo Ripken
    Abstract Femtosekundenlaser, Ultrakurzpulslaser, MHz-Repetitionsraten, Nanojoule, Photodisruption, fs-LASIK, Presbyopie
    Sprache Deutsch
    Umfang Online-Ressource (153 S. = 51,2 Mb)
    Verlag Technische Informationsbibliothek u. Universitätsbibliothek
    Erscheinungsort Hannover
    Dokumenttyp Buch ; Online ; Dissertation / Habilitation
    Dissertation / Habilitation Univ., Diss.--Hannover, 2007
    Datenquelle Ehemaliges Sondersammelgebiet Küsten- und Hochseefischerei

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  7. Artikel ; Online: Measurement of tear resistance after manual capsulorhexis and femtosecond laser-assisted capsulotomy of crystalline lenses.

    Patzlaff-Günther, Mandy / Fromm, Michael / Kern, Thomas / Bartram, Martin / Schwäblein, Anna / Heinemann, Dag / Johannsmeier, Sonja / Framme, Carsten / Ripken, Tammo

    Lasers in medical science

    2021  Band 37, Heft 3, Seite(n) 1891–1897

    Abstract: Background: In this study, the tear resistance of porcine lens capsules after continuous curvilinear capsulorhexis (CCC) and femtosecond (fs)-laser-assisted capsulotomy for cataract surgery (FLC) with different laser parameters is measured with a custom- ...

    Abstract Background: In this study, the tear resistance of porcine lens capsules after continuous curvilinear capsulorhexis (CCC) and femtosecond (fs)-laser-assisted capsulotomy for cataract surgery (FLC) with different laser parameters is measured with a custom-made testing setup.
    Methods: Forty-five fresh porcine lenses were randomly chosen for CCC (n = 15) or FLC 1 (n = 15) and FLC 2 (n = 15). The FLC 1-group was treated with smaller spot distances than the FLC 2-group. The force necessary to break the opening of the anterior capsule and the maximum displacement were measured.
    Results: The mean tear resistance of the CCC-group (150 ± 70 mN) was higher than that of the FLC 1-group (60 ± 20 mN) and the FLC 2-group (30 ± 20 mN).
    Conclusion: It could be shown that CCC leads to a significantly higher tear resistance of the opening than FLC in porcine lenses. The femtosecond laser group demonstrated that smaller spot distances lead to a higher tear resistance.
    Mesh-Begriff(e) Animals ; Anterior Capsule of the Lens/surgery ; Capsulorhexis ; Cataract Extraction ; Laser Therapy ; Lasers ; Swine
    Sprache Englisch
    Erscheinungsdatum 2021-10-29
    Erscheinungsland England
    Dokumenttyp Journal Article
    ZDB-ID 632808-8
    ISSN 1435-604X ; 0268-8921
    ISSN (online) 1435-604X
    ISSN 0268-8921
    DOI 10.1007/s10103-021-03448-1
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  8. Artikel ; Online: Corneal riboflavin gradients and UV-absorption characteristics after topical application of riboflavin in concentrations ranging from 0.1 to 0.5.

    Franke, Maximilian A D / Landes, Timm / Seiler, Theo G / Khayyat, Diaa / Johannsmeier, Sonja / Heinemann, Dag / Ripken, Tammo

    Experimental eye research

    2021  Band 213, Seite(n) 108842

    Abstract: Avoiding damage of the endothelial cells, especially in thin corneas, remains a challenge in corneal collagen crosslinking (CXL). Knowledge of the riboflavin gradients and the UV absorption characteristics after topical application of riboflavin in ... ...

    Abstract Avoiding damage of the endothelial cells, especially in thin corneas, remains a challenge in corneal collagen crosslinking (CXL). Knowledge of the riboflavin gradients and the UV absorption characteristics after topical application of riboflavin in concentrations ranging from 0.1% to 0.5% could optimize the treatment. In this study, we present a model to calculate the UV-intensity depending on the corneal thickness. Ten groups of de-epithelialized porcine corneas were divided into 2 subgroups. Five groups received an imbibition of 10 min and the other five groups for 30 min. The applied riboflavin concentrations were 0.1%, 0.2%, 0.3%, 0.4% and 0.5% diluted in a 15% dextran solution for each subgroup. After the imbibition process, two-photon fluorescence microscopy was used to determine fluorescence intensity, which was compared to samples after saturation, yielding the absolute riboflavin concentration gradient of the cornea. The extinction coefficient of riboflavin solutions was measured using a spectrophotometer. Combining the obtained riboflavin concentrations and the extinction coefficients, a depth-dependent UV-intensity profile was calculated for each group. With increasing corneal depth, the riboflavin concentration decreased for all imbibition solutions and application times. The diffusion coefficients of 10 min imbibition time were higher than for 30 min. A higher RF concentration and a longer imbibition time resulted in higher UV-absorption and a lower UV-intensity in the depth of the cornea. Calculated UV-transmission was 6 percentage points lower compared to the measured transmission. By increasing the riboflavin concentration of the imbibition solution, a substantially higher UV-absorption inside the cornea is achieved. This offers a simple treatment option to control the depth of crosslinking e.g. in thin corneas, resulting in a lower risk of endothelial damage.
    Mesh-Begriff(e) Absorption, Radiation/drug effects ; Administration, Ophthalmic ; Animals ; Corneal Pachymetry ; Corneal Stroma/metabolism ; Corneal Stroma/radiation effects ; Cross-Linking Reagents ; Microscopy, Fluorescence, Multiphoton ; Ophthalmic Solutions ; Photochemotherapy ; Photosensitizing Agents/administration & dosage ; Photosensitizing Agents/pharmacokinetics ; Riboflavin/administration & dosage ; Riboflavin/pharmacokinetics ; Swine ; Ultraviolet Rays
    Chemische Substanzen Cross-Linking Reagents ; Ophthalmic Solutions ; Photosensitizing Agents ; Riboflavin (TLM2976OFR)
    Sprache Englisch
    Erscheinungsdatum 2021-11-16
    Erscheinungsland England
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 80122-7
    ISSN 1096-0007 ; 0014-4835
    ISSN (online) 1096-0007
    ISSN 0014-4835
    DOI 10.1016/j.exer.2021.108842
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  9. Artikel ; Online: Femtosecond laser induced step-like structures inside transparent hydrogel due to laser induced threshold reduction.

    Saerchen, Emanuel / Liedtke-Gruener, Susann / Kopp, Maximilian / Heisterkamp, Alexander / Lubatschowski, Holger / Ripken, Tammo

    PloS one

    2019  Band 14, Heft 9, Seite(n) e0222293

    Abstract: In the area of laser material processing, versatile applications for cutting glasses and transparent polymers exist. However, parasitic effects such as the creation of step-like structures appear when laser cutting inside a transparent material. To date, ...

    Abstract In the area of laser material processing, versatile applications for cutting glasses and transparent polymers exist. However, parasitic effects such as the creation of step-like structures appear when laser cutting inside a transparent material. To date, these structures were only described empirically. This work establishes the physical and chemical mechanisms behind the observed effects and describes the influence of process and material parameters onto the creation of step-like structures in hydrogel, Dihydroxyethylmethacrylat (HEMA). By focusing laser pulses in HEMA, reduced pulse separation distance below 50 nm and rise in pulse energy enhances the creation of unintended step-like structures. Spatial resolved Raman-spectroscopy was used to measure the laser induced chemical modification, which results into a reduced breakdown threshold. The reduction in threshold influences the position of optical breakdown for the succeeding laser pulses and consequently leads to the step-like structures. Additionally, the experimental findings were supplemented with numerical simulations of the influence of reduced damage threshold onto the position of optical breakdown. In summary, chemical material change was defined as cause of the step-like structures. Furthermore, the parameters to avoid these structures were identified.
    Mesh-Begriff(e) Hydrogels/chemistry ; Lasers ; Light ; Spectrum Analysis, Raman/methods
    Chemische Substanzen Hydrogels
    Sprache Englisch
    Erscheinungsdatum 2019-09-17
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 1932-6203
    ISSN (online) 1932-6203
    DOI 10.1371/journal.pone.0222293
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  10. Buch ; Dissertation / Habilitation: Anwendung von MHz-fs-Lasern in der Ophthalmologie und Erarbeitung eines Therapiekonzeptes für die laserassistierte Behandlung der Alterssichtigkeit

    Ripken, Tammo

    2007  

    Verfasserangabe von Tammo Ripken
    Sprache Deutsch
    Umfang VIII, 145 S., Ill., graph. Darst.
    Dokumenttyp Buch ; Dissertation / Habilitation
    Dissertation / Habilitation Univ., Diss.--Hannover, 2007
    Datenquelle Katalog der Technische Informationsbibliothek Hannover

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