1. Articles from Tom Pfeiffer

    1-19 of 19
    1. High-speed fiber scanning endoscope for volumetric multi-megahertz optical coherence tomography

      High-speed fiber scanning endoscope for volumetric multi-megahertz optical coherence tomography

      We present a forward-viewing fiber scanning endoscope (FSE) for high-speed volumetric optical coherence tomography (OCT). The reduction in size of the probe was achieved by substituting the focusing optics by an all-fiber-based imaging system which consists of a combination of scanning single-mode fibers, a glass spacer, made from a step-index multi-mode fiber, and a gradient-index fiber. A lateral resolution of 11 μm was achieved at a working distance of 1.2 mm. The newly designed piezo-based FSE has an outer diameter of 1.6 mm and a rigid length of 13.5 mm. By moving the whole imaging optic in ...

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    2. Ultra low noise Fourier domain mode locked laser for high quality megahertz optical coherence tomography

      Ultra low noise Fourier domain mode locked laser for high quality megahertz optical coherence tomography

      We investigate the origin of high frequency noise in Fourier domain mode locked (FDML) lasers and present an extremely well dispersion compensated setup which virtually eliminates intensity noise and dramatically improves coherence properties. We show optical coherence tomography (OCT) imaging at 3.2 MHz A-scan rate and demonstrate the positive impact of the described improvements on the image quality. Especially in highly scattering samples, at specular reflections and for strong signals at large depth, the noise in optical coherence tomography images is significantly reduced. We also describe a simple model that suggests a passive physical stabilizing mechanism that leads to ...

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    3. High-resolution retinal swept source optical coherence tomography with an ultra-wideband Fourier-domain mode-locked laser at MHz A-scan rates

      High-resolution retinal swept source optical coherence tomography with an ultra-wideband Fourier-domain mode-locked laser at MHz A-scan rates

      We present a new 1060 nm Fourier domain mode locked laser (FDML laser) with a record 143 nm sweep bandwidth at 2∙ 417 kHz = 834 kHz and 120 nm at 1.67 MHz, respectively. We show that not only the bandwidth alone, but also the shape of the spectrum is critical for the resulting axial resolution, because of the specific wavelength-dependent absorption of the vitreous. The theoretical limit of our setup lies at 5.9 µm axial resolution. In vivo MHz-OCT imaging of human retina is performed and the image quality is compared to the previous results acquired with 70 ...

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    4. Feature Of The Week 09/10/2017: Thermo-elastic Optical Coherence Tomography

      Feature Of The Week 09/10/2017: Thermo-elastic  Optical Coherence Tomography

      The conventional OCT image contrast is derived from elastic scattering, and shows the internal structure of the sample. The determination of the tissue type in OCT images usually depends on the interpretation by the image reader. More accurate tissue type contrast may be achieved by new OCT-based imaging modalities, with sensitivity to other physical parameters than scattering alone. Phase-sensitive OCT can detect tissue motion on nanometer-to- micrometer length scales using the phase of the OCT signal. Depending on the nature of the excitation, different functional images can be reconstructed: a mechanical stimulus yields images of tissue elasticity (optical coherence elastography ...

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    5. Thermo-elastic optical coherence tomography

      Thermo-elastic optical coherence tomography

      The absorption of nanosecond laser pulses induces rapid thermo-elastic deformation in tissue. A sub-micrometer scale displacement occurs within a few microseconds after the pulse arrival. In this Letter, we investigate the laser-induced thermo-elastic deformation using a 1.5 MHz phase-sensitive optical coherence tomography (OCT) system. A displacement image can be reconstructed, which enables a new modality of phase-sensitive OCT, called thermo-elastic OCT. An analysis of the results shows that the optical absorption is a dominating factor for the displacement. Thermo-elastic OCT is capable of visualizing inclusions that do not appear on the structural OCT image, providing additional tissue type information.

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    6. Feature tracking for automated volume of interest stabilization on 4D-OCT images

      Feature tracking for automated volume of interest stabilization on 4D-OCT images

      A common representation of volumetric medical image data is the triplanar view (TV), in which the surgeon manually selects slices showing the anatomical structure of interest. In addition to common medical imaging such as MRI or computed tomography, recent advances in the field of optical coherence tomography (OCT) have enabled live processing and volumetric rendering of four-dimensional images of the human body. Due to the region of interest undergoing motion, it is challenging for the surgeon to simultaneously keep track of an object by continuously adjusting the TV to desired slices. To select these slices in subsequent frames automatically, it ...

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    7. Analysis of FDML lasers with meter range coherence

      Analysis of FDML lasers with meter range coherence

      FDML lasers provide sweep rates in the MHz range at wide optical bandwidths, making them ideal sources for high speed OCT. Recently, at lower speed, ultralong-range swept-source OCT has been demonstrated using a tunable vertical cavity surface emitting laser (VCSEL) and also using a Vernier-tunable laser. These sources provide relatively high sweep rates and meter range coherence lengths. In order to achieve similar coherence, we developed an extremely well dispersion compensated Fourier Domain Mode Locked (FDML) laser, running at 3.2 MHz sweep rate and 120 nm spectral bandwidth. We demonstrate that this laser offers meter range coherence and enables ...

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    8. Heartbeat OCT and Motion-Free 3D In Vivo Coronary Artery Microscopy

      Heartbeat OCT and Motion-Free 3D In Vivo Coronary Artery Microscopy

      Intravascular optical coherence tomography (IV-OCT) has gained widespread use over the past few years, offering highly detailed images of coronary artery pathologies and interventions (1) . In contrast to the cross-sectional view, longitudinal sections and 3-dimensional (3D) renderings are affected by cardiac motion artifacts and undersampling, complicating interpretation and measurements (2) . We developed Heartbeat OCT, a new OCT method that achieves up to 4,000 frames/s imaging speed for isotropically sampled volume datasets acquired within the diastolic phase of 1 cardiac cycle to restore 3D IV-OCT image fidelity. In this research letter, we present the first in vivo data acquired ...

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    9. Flexible A-scan rate MHz OCT: computational downscaling by coherent averaging

      Flexible A-scan rate MHz OCT: computational downscaling by coherent averaging

      In order to realize fast OCT-systems with adjustable line rate, we investigate averaging of image data from an FDML based MHz-OCT-system. The line rate can be reduced in software and traded in for increased system sensitivity and image quality. We compare coherent and incoherent averaging to effectively scale down the system speed of a 3.2 MHz FDML OCT system to around 100 kHz in postprocessing. We demonstrate that coherent averaging is possible with MHz systems without special interferometer designs or digital phase stabilisation. We show OCT images of a human finger knuckle joint in vivo with very high quality ...

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    10. Feature Of The Week 12/06/2015: Heartbeat Optical Coherence Tomography

      Feature Of The Week 12/06/2015: Heartbeat Optical Coherence Tomography

      Intravascular optical coherence tomography (IV-OCT) has gained widespread use over the past few years, offering highly detailed images of the coronary artery pathologies and interventions. In contrast to the cross-sectional view, longitudinal sections and three-dimensional (3D) renderings are affected by cardiac motion artifacts and undersampling, complicating interpretation and measurements. We developed Heartbeat OCT, a new OCT method that overcomes these issues. This study aims to demonstrate in vivo Heartbeat OCT in a preclinical setting, imaging eliminating cardiac motion artifacts, undersampling and non-uniform rotational distortion, to generate high-quality OCT volumes. Using a micro motor actuated catheter and a MHz sweep rate ...

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    11. Heartbeat OCT: in vivo intravascular megahertz-optical coherence tomography

      Heartbeat OCT: in vivo intravascular megahertz-optical coherence tomography

      Cardiac motion artifacts, non-uniform rotational distortion and undersampling affect the image quality and the diagnostic impact of intravascular optical coherence tomography (IV-OCT). In this study we demonstrate how these limitations of IV-OCT can be addressed by using an imaging system that we called “Heartbeat OCT”, combining a fast Fourier Domain Mode Locked laser, fast pullback, and a micromotor actuated catheter, designed to examine a coronary vessel in less than one cardiac cycle. We acquired in vivo data sets of two coronary arteries in a porcine heart with both Heartbeat OCT, working at 2.88 MHz A-line rate, 4000 frames/s ...

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    12. Optical coherence tomography guided laser cochleostomy: towards the accuracy on tens of micrometer scale

      Optical coherence tomography guided laser cochleostomy: towards the accuracy on tens of micrometer scale

      Lasers have been proven to be precise tools for bone ablation. Applying no mechanical stress to the patient, they are potentially very suitable for microsurgery on fragile structures such as the inner ear. However, it remains challenging to control the laser-bone ablation without injuring embedded soft tissue. In this work, we demonstrate a closed-loop control of a short-pulsed CO 2 laser to perform laser cochleostomy under the monitoring of an optical coherence tomography (OCT) system. A foresighted detection of the bone-endosteum-perilymph boundary several hundred micrometers before its exposure has been realized. Position and duration of the laser pulses are planned ...

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    13. High definition live 3D-OCT in vivo: design and evaluation of a 4D OCT engine with 1 GVoxel/s

      High definition live 3D-OCT in vivo: design and evaluation of a 4D OCT engine with 1 GVoxel/s

      We present a 1300 nm OCT system for volumetric real-time live OCT acquisition and visualization at 1 billion volume elements per second. All technological challenges and problems associated with such high scanning speed are discussed in detail as well as the solutions. In one configuration, the system acquires, processes and visualizes 26 volumes per second where each volume consists of 320 x 320 depth scans and each depth scan has 400 usable pixels. This is the fastest real-time OCT to date in terms of voxel rate. A 51 Hz volume rate is realized with half the frame number. In both ...

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    14. Feature Of The Week 6/30/13: Ultrafast Intravascular Optical Coherence Tomography Imaging

      Feature Of The Week 6/30/13: Ultrafast Intravascular Optical Coherence Tomography Imaging

      The fastest commercial intravascular optical coherence tomography (OCT) systems acquire 160 frames/second with 500 lines/frame, and the pullback speed is limited to 40 mm∕s. In this situation, the images are under sampled in the pullback direction: Only 12% of the lumen is sampled because the sampling interval of 250 μm is much larger than the transverse resolution, which is approximately 30 μm. In clinical situations, the cardiac motion also affects the OCT acquisition. The pullback procedure for the whole artery takes several seconds. The cardiac motion during acquisition will cause inaccuracy in frame spacing and possibly frame ...

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    15. Ultrahigh-speed intravascular optical coherence tomography imaging at 3200 frames per second

      Ultrahigh-speed intravascular optical coherence tomography imaging at 3200 frames per second

      We demonstrated intravascular OCT imaging with frame rate up to 3.2 kHz (192,000 rpm scanning). This was achieved by using a custom-built catheter in which the circumferential scanning was actuated by a 1.0 mm diameter synchronous motor. The OCT system was based on a Fourier Domain Mode Locked laser operating at an A-line rate of 1.6 MHz. The diameter of the catheter was 1.1 mm at the tip. Ex vivo images of human coronary artery (~78.4 mm length) were acquired at a pullback speed of 100 mm/s. True 3D volumetric imaging of the ...

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    16. Feature Of The Week 6/23/13: Ludwig Maximilian University of Munich Investigates Benefits of Joint Aperture Detection in Ophthalmic MHz OCT

      Feature Of The Week 6/23/13: Ludwig Maximilian University of Munich Investigates Benefits of Joint Aperture Detection in Ophthalmic MHz OCT

      Joint-aperture optical coherence tomography (JA-OCT) is an angle-resolved OCT method, in which illumination from an active channel is simultaneously probed by several passive channels. JA-OCT increases the collection efficiency and effective sensitivity of the OCT system without increasing the power on the sample. Additionally, JA-OCT provides angular scattering information about the sample in a single acquisition, so the OCT imaging speed is not reduced. Thus, JA-OCT is especially suitable for ultra high speed in-vivo imaging. JA-OCT is compared to other angle-resolved techniques, and the relation between joint aperture imaging, adaptive optics, coherent and incoherent compounding is discussed. We present angle-resolved ...

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    17. Intravascular optical coherence tomography imaging at 3200 frames per second

      Intravascular optical coherence tomography imaging at 3200 frames per second

      We demonstrate intravascular optical coherence tomography (OCT) imaging with frame rate up to 3.2 kHz (192,000 rpm scanning). This was achieved by using a custom-built catheter in which the circumferential scanning was actuated by a 1.0 mm diameter synchronous motor. The OCT system, with an imaging depth of 3.7 mm (in air), is based on a Fourier domain mode locked laser operating at an A-line rate of 1.6 MHz. The diameter of the catheter is 1.1 mm at the tip. Ex vivo images of human coronary artery (78.4 mm length) were acquired at ...

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    18. Joint aperture detection for speckle reduction and increased collection efficiency in ophthalmic MHz OCT

      Joint aperture detection for speckle reduction and increased collection efficiency in ophthalmic MHz OCT

      Joint-aperture optical coherence tomography (JA-OCT) is an angle-resolved OCT method, in which illumination from an active channel is simultaneously probed by several passive channels. JA-OCT increases the collection efficiency and effective sensitivity of the OCT system without increasing the power on the sample. Additionally, JA-OCT provides angular scattering information about the sample in a single acquisition, so the OCT imaging speed is not reduced. Thus, JA-OCT is especially suitable for ultra high speed in-vivo imaging. JA-OCT is compared to other angle-resolved techniques, and the relation between joint aperture imaging, adaptive optics, coherent and incoherent compounding is discussed. We present angle-resolved ...

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    19. Chromatic polarization effects of swept waveforms in FDML lasers and fiber spools

      Chromatic polarization effects of swept waveforms in FDML lasers and fiber spools

      We present detailed investigations of chromatic polarization effects, caused by fiber spools used in FDML lasers and buffering spools for rapidly wavelength swept lasers. We introduce a novel wavelength swept FDML laser source, specially tailored for polarization sensitive optical coherence tomography (OCT) which switches between two different linear polarization states separated by 45°, i.e. 90° on the Poincaré sphere. The polarization maintaining laser cavity itself generates a stable linear polarization state and uses an external buffering technique in order to provide alternating polarization states for successive wavelength sweeps. The design of the setup is based on a comprehensive analysis ...

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    1-19 of 19
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  2. Topics in the News

    1. (19 articles) Robert A. Huber
    2. (19 articles) Tom Pfeiffer
    3. (15 articles) Wolfgang Wieser
    4. (12 articles) University of Lübeck
    5. (11 articles) Ludwig Maximilian University of Munich
    6. (8 articles) Gijs van Soest
    7. (8 articles) Tianshi Wang
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    Chromatic polarization effects of swept waveforms in FDML lasers and fiber spools Joint aperture detection for speckle reduction and increased collection efficiency in ophthalmic MHz OCT Intravascular optical coherence tomography imaging at 3200 frames per second Feature Of The Week 6/23/13: Ludwig Maximilian University of Munich Investigates Benefits of Joint Aperture Detection in Ophthalmic MHz OCT Ultrahigh-speed intravascular optical coherence tomography imaging at 3200 frames per second Feature Of The Week 6/30/13: Ultrafast Intravascular Optical Coherence Tomography Imaging High definition live 3D-OCT in vivo: design and evaluation of a 4D OCT engine with 1 GVoxel/s Heartbeat OCT: in vivo intravascular megahertz-optical coherence tomography Feature Of The Week 12/06/2015: Heartbeat Optical Coherence Tomography Feature Of The Week 09/10/2017: Thermo-elastic  Optical Coherence Tomography Notal Vision Engages Wasatch Photonics Bringing AI-Enabled Home-Based Optical Coherence Tomography Closer to Market Semiconductor Lasers and Diode-based Light Sources for Biophotonics (Textbook)