Hendrik Spahr

Doktorand (PhD-Student)


Institut für Biomedizinische Optik
Peter-Monnik-Weg 4
23562 Lübeck

Gebäude MFC7, Raum 4. OG

Email:
Phone:
+49 (0)451 3101 3294
Fax:
+49 (0)451 3101 3204

2018

  • Sudkamp, Helge and Hillmann, Dierck and Koch, Peter and Endt, Malte vom and Spahr, Hendrik and Münst, Michael and Pfäffle, Clara and Birngruber, Reginald and Hüttmann, Gereon: Simple approach for aberration-corrected OCT imaging of the human retina. Optics Letters, no. 43, pp. 4224, 2018
    BibTeX Link
    @article{Sudkamp2018a,
       author = {Sudkamp, Helge and Hillmann, Dierck and Koch, Peter and Endt, Malte vom and Spahr, Hendrik and Münst, Michael and Pfäffle, Clara and Birngruber, Reginald and Hüttmann, Gereon},
       title = {Simple approach for aberration-corrected OCT imaging of the human retina},
       journal = {Optics Letters},
       volume = {43},
       number = {17},
       pages = {4224},
       ISSN = {0146-9592
    1539-4794},
       DOI = {10.1364/ol.43.004224},
       year = {2018},
       type = {Journal Article},
       keyword = {Retome}
    }
    
  • Hendrik Spahr and Clara Pfäffle and Peter Koch and Helge Sudkamp and Gereon Hüttmann and Dierck Hillmann: Interferometric detection of 3D motion using computational subapertures in optical coherence tomography. Opt. Express, no. 26, pp. 18803-18816, OSA, Jul, 2018
    BibTeX Link Link
    @article{Spahr:18,
    author = {Hendrik Spahr, Clara Pfäffle, Peter Koch, Helge Sudkamp, Gereon Hüttmann und Dierck Hillmann},
    journal = {Opt. Express},
    keywords = {Funktion, Fullfield},
    number = {15},
    pages = {18803--18816},
    publisher = {OSA},
    title = {Interferometric detection of 3D motion using computational subapertures in optical coherence tomography},
    volume = {26},
    month = {Jul},
    year = {2018},
    url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-26-15-18803},
    doi = {10.1364/OE.26.018803},
    abstract = {Doppler optical coherence tomography (OCT) quantifies axial motion with high precision, whereas lateral motion cannot be detected by a mere evaluation of phase changes. This problem was solved by the introduction of three-beam Doppler OCT, which, however, entails a high experimental effort. Here, we present the numerical analogue to this experimental approach. Phase-stable complex-valued OCT datasets, recorded with full-field swept-source OCT, are filtered in the Fourier domain to limit imaging to different computational subapertures. These are used to calculate all three components of the motion vector with interferometric precision. As known from conventional Doppler OCT for axial motion only, the achievable accuracy exceeds the actual imaging resolution by orders of magnitude in all three dimensions. The feasibility of this method is first demonstrated by quantifying micro-rotation of a scattering sample. Subsequently, a potential application is explored by recording the 3D motion vector field of tissue during laser photocoagulation in ex-vivo porcine retina.},
    }
    
    
  • Hinnerk Schulz-Hildebrandt and Michael Münter and Martin Ahrens and Hendrik Spahr and Dierck Hillmann and Peter König and Gereon Hüttmann: Coherence and diffraction limited resolution in microscopic OCT by a unified approach for the correction of dispersion and aberrations. in 2nd Canterbury Conference on OCT with Emphasis on Broadband Optical Sources, no. 10591, pp. 105910O, 2018
    BibTeX Link
    @inproceedings{Schulz-Hildebrandt2018a,
    title = {Coherence and diffraction limited resolution in microscopic OCT by a unified approach for the correction of dispersion and aberrations},
    author = {Hinnerk Schulz-Hildebrandt and Michael M\"{u}nter and Martin Ahrens and Hendrik Spahr and Dierck Hillmann and Peter K\"{o}nig and Gereon H\"{u}ttmann},
    doi = {10.1117/12.2303755},
    isbn = {9781510616745},
    year = {2018},
    date = {2018-03-05},
    booktitle = {2nd Canterbury Conference on OCT with Emphasis on Broadband Optical Sources},
    volume = {10591},
    pages = {105910O},
    abstract = {Optical coherence tomography (OCT) images scattering tissues with 5 to 15 μm resolution. This is usually not sufficient for a distinction of cellular and subcellular structures. Increasing axial and lateral resolution and compensation of artifacts caused by dispersion and aberrations is required to achieve cellular and subcellular resolution. This includes defocus which limit the usable depth of field at high lateral resolution. OCT gives access the phase of the scattered light and hence correction of dispersion and aberrations is possible by numerical algorithms. Here we present a unified dispersion/aberration correction which is based on a polynomial parameterization of the phase error and an optimization of the image quality using Shannon’s entropy. For validation, a supercontinuum light sources and a costume-made spectrometer with 400 nm bandwidth were combined with a high NA microscope objective in a setup for tissue and small animal imaging. Using this setup and computation corrections, volumetric imaging at 1.5 μm resolution is possible. Cellular and near cellular resolution is demonstrated in porcine cornea and the drosophila larva, when computational correction of dispersion and aberrations is used. Due to the excellent correction of the used microscope objective, defocus was the main contribution to the aberrations. In addition, higher aberrations caused by the sample itself were successfully corrected. Dispersion and aberrations are closely related artifacts in microscopic OCT imaging. Hence they can be corrected in the same way by optimization of the image quality. This way microscopic resolution is easily achieved in OCT imaging of static biological tissues.},
    keywords = {OCM},
    pubstate = {published},
    tppubtype = {inproceedings}
    }

2017

  • Pfäffle, Clara and Spahr, Hendrik and Hillmann, Dierck and Sudkamp, Helge and Franke, Gesa and Koch, Peter and Hüttmann, Gereon: Reduction of frame rate in full-field swept-source optical coherence tomography by numerical motion correction [Invited]. Biomedical Optics Express, no. 8, pp. 1499-1511, 2017
    BibTeX Link
    @article{Pfäffle2017,
       author = {Pfäffle, Clara and Spahr, Hendrik and Hillmann, Dierck and Sudkamp, Helge and Franke, Gesa and Koch, Peter and Hüttmann, Gereon},
       title = {Reduction of frame rate in full-field swept-source optical coherence tomography by numerical motion correction [Invited]},
       journal = {Biomedical Optics Express},
       volume = {8},
       number = {3},
       pages = {1499-1511},
       keywords = {Image reconstruction-restoration
    Optical coherence tomography},
       url = {http://www.osapublishing.org/boe/abstract.cfm?URI=boe-8-3-1499},
       year = {2017},
       type = {Journal Article}
    }
    
  • Hillmann, Dierck and Spahr, Hendrik and Sudkamp, Helge and Hain, Carola and Hinkel, Laura and Franke, Gesa and Hüttmann, Gereon: Off-axis reference beam for full-field swept-source OCT and holoscopy. Optics Express, no. 25, pp. 27770-27784, 2017
    BibTeX Link
    @article{Hillmann2017,
       author = {Hillmann, Dierck and Spahr, Hendrik and Sudkamp, Helge and Hain, Carola and Hinkel, Laura and Franke, Gesa and Hüttmann, Gereon},
       title = {Off-axis reference beam for full-field swept-source OCT and holoscopy},
       journal = {Optics Express},
       volume = {25},
       number = {22},
       pages = {27770-27784},
       DOI = {10.1364/OE.25.027770},
       year = {2017},
       type = {Journal Article}
    }
    

2016

  • Huttmann, Gereon and Moltmann, Moritz and Spahr, Hendrik and Tode, Jan and de Roeck, Anna and Theisen-Kunde, Dirk and Birngruber, Reginald and Koinzer, Stefan and Brinkmann, Ralf: Retinal lesion formation during photocoagulation investigated by high-speed 1060 nm Doppler-OCT: first clinical results. Investigative Ophthalmology & Visual Science, no. 57, pp. 5852-5852, 2016
    BibTeX Link
    @article{Hüttmann2016,
       author = {Huttmann, Gereon and Moltmann, Moritz and Spahr, Hendrik and Tode, Jan and de Roeck, Anna and Theisen-Kunde, Dirk and Birngruber, Reginald and Koinzer, Stefan and Brinkmann, Ralf},
       title = {Retinal lesion formation during photocoagulation investigated by high-speed 1060 nm Doppler-OCT: first clinical results},
       journal = {Investigative Ophthalmology & Visual Science},
       volume = {57},
       number = {12},
       pages = {5852-5852},
       abstract = {Abstract Purpose : The molecular processes during heating with a photocoagulation laser, particularly in sub-visible or mere thermal stimulation treatment, have only partly been understood, and different theories exist that try to explain its clinical efficacy. Optical coherence tomography (OCT) was successfully used to grade lesions with high accuracy 1 hour after the treatments and beyond. During the irradiation, changes in tissue scattering and, by use of the Doppler signal, tissue motion caused by thermal expansion and coagulation-induced tissue contraction were shown to correlate ex-vivo and in rabbits with the strength of photocoagulation lesions. Aim of this study was to validate feasibility and reproducibility of these results in humans. Methods : In an ongoing study more than 100 lesions of three patients have been imaged with a slitlamp-based OCT (1060 nm, 90,000 A-scans/s) with varying irradiance during laser exposure. Durations of the exposure were 50 ms and 200 ms; spot size was 300 µm. Eye movements and heart beat were corrected by cross-correlation of the images. Increased tissue scattering and movement of the neuronal retina due to thermal expansion were determined from the image sequences with 3 ms temporal resolution. Results : In the first treatments with this prototype device, we received acceptable image quality in 1/3 of the lesions. Changes in the neuronal retina were successful visualized during and after the laser irradiation, demonstrating the feasibility of a real-time assessment of initial effects of photocoagulation in humans. Lesion visibility in standard, reflection-based OCT was much weaker during treatment compared to 1 hour afterwards. Increased tissue scattering was observed in stronger lesions already during the laser irradiation. At reduced irradiance, scattering increase was only observed after the end of irradiation. However, tissue motion towards the vitreous was still observed in these cases. Conclusions : In conclusion, high-speed OCT recording during photocoagulation measures initial tissue changes during photocoagulation in humans. It may enhance our understanding of the tissue dynamics right after laser irradiation. It may provide useful information for a real-time dosage control as well. This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.},
       ISSN = {1552-5783},
       url = {http://dx.doi.org/},
       year = {2016},
       type = {Journal Article}
    }
    
  • Sudkamp, Helge and Koch, Peter and Spahr, Hendrik and Hillmann, Dierck and Franke, Gesa and Münst, Michael and Reinholz, Fred and Birngruber, Reginald and Hüttmann, Gereon: In-vivo retinal imaging with off-axis full-field time-domain optical coherence tomography. Optics Letters, no. 41, pp. 4987-4990, 2016
    BibTeX Link
    @article{Sudkamp2016,
       author = {Sudkamp, Helge and Koch, Peter and Spahr, Hendrik and Hillmann, Dierck and Franke, Gesa and Münst, Michael and Reinholz, Fred and Birngruber, Reginald and Hüttmann, Gereon},
       title = {In-vivo retinal imaging with off-axis full-field time-domain optical coherence tomography},
       journal = {Optics Letters},
       volume = {41},
       number = {21},
       pages = {4987-4990},
       abstract = {With a simple setup, mainly composed of a low coherence light source and a camera, full-field optical coherence tomography (FF-OCT) allows volumetric tissue imaging. However, fringe washout constrains its use in retinal imaging. Here, we present a novel motion-insensitive approach to FF-OCT, which introduces path-length differences between the reference and the sample light in neighboring pixels using an off-axis reference beam. The temporal carrier frequency in scanned time-domain OCT is replaced by a spatial carrier frequency. Volumetric in-vivo FF-OCT measurements of the human retina were acquired in only 1.3 s, comparable to the acquisition times of current clinically used OCT devices.},
       keywords = {Imaging systems
    Coherence imaging
    Optical coherence tomography
    Frequency filtering
    Interferometric imaging},
    DOI = {10.1364/OL.41.004987}
     url= {https://www.osapublishing.org/ol/abstract.cfm?uri=ol-41-21-4987}  
       year = {2016},
       type = {Journal Article}
    }
    
  • Hillmann, Dierck and Spahr, Hendrik and Pfäffle, Clara and Sudkamp, Helge and Franke, Gesa and Hüttmann, Gereon: In vivo optical imaging of physiological responses to photostimulation in human photoreceptors. PNAS Early Edition, pp. 1-6, 2016
    BibTeX Link
    @article{Hillmann2016,
       author = {Hillmann, Dierck and Spahr, Hendrik and Pfäffle, Clara and Sudkamp, Helge and Franke, Gesa and Hüttmann, Gereon},
       title = {In vivo optical imaging of physiological responses to photostimulation in human photoreceptors},
       journal = {PNAS Early Edition},
       pages = {1-6},
       abstract = {Noninvasive functional imaging of molecular and cellular processes of vision may have immense impact on research and clinical diagnostics. Although suitable intrinsic optical signals (IOSs) have been observed ex vivo and in immobilized animals in vivo, detecting IOSs of photoreceptor activity in living humans was cumbersome and time consuming. Here, we observed clear spatially and temporally resolved changes in the optical path length of the photoreceptor outer segment as a response to an optical stimulus in the living human eye. To witness these changes, we evaluated phase data obtained with a parallelized and computationally aberration-corrected optical coherence tomography system. The noninvasive detection of optical path length changes shows neuronal photoreceptor activity of single cones in living human retina, and therefore, it may provide diagnostic options in ophthalmology and neurology and could provide insights into visual phototransduction in humans.},
       url = {http://www.pnas.org/content/early/2016/10/10/1606428113.abstract},
       year = {2016},
       type = {Journal Article}
    }
    
  • Spahr, H. and Hillmann, D. and Hain, C. and Pfäffle, C. and Sudkamp, H. and Franke, G. and Koch, P. and Hüttmann, G.: Darstellung von Blutfluss und Pulsation in retinalen Gefäßen mit Full-Field-Swept-Source-OCT. Klin Monatsbl Augenheilkd, no. 233, pp. 1324-1330, 2016
    BibTeX Link
    @article{Spahr2016,
       author = {Spahr, H. and Hillmann, D. and Hain, C. and Pfäffle, C. and Sudkamp, H. and Franke, G. and Koch, P. and Hüttmann, G.},
       title = {Darstellung von Blutfluss und Pulsation in retinalen Gefäßen mit Full-Field-Swept-Source-OCT},
       journal = {Klin Monatsbl Augenheilkd},
       volume = {233},
       number = {12},
       pages = {1324-1330},
       ISSN = {0023-2165},
       DOI = {10.1055/s-0042-120279},
       year = {2016},
       type = {Journal Article}
    }
    
  • Hillmann, Dierck and Spahr, Hendrik and Hain, Carola and Sudkamp, Helge and Franke, Gesa and Pfäffle, Clara and Winter, Christian and Hüttmann, Gereon: Aberration-free volumetric high-speed imaging of in vivo retina. Scientific Reports, no. 6, pp. 1-11, 2016
    BibTeX Link
    @article{Hillmann2016,
       author = {Hillmann, Dierck and Spahr, Hendrik and Hain, Carola and Sudkamp, Helge and Franke, Gesa and Pfäffle, Clara and Winter, Christian and Hüttmann, Gereon},
       title = {Aberration-free volumetric high-speed imaging of in vivo retina},
       journal = {Scientific Reports},
       volume = {6},
       pages = {1-11},
       url = {http://dx.doi.org/10.1038/srep35209},
       year = {2016},
       type = {Journal Article}
    }
    

2015

  • Spahr, Hendrik and Hillmann, Dierck and Hain, Carola and Pfäffle, Clara and Sudkamp, Helge and Franke, Gesa and Hüttmann, Gereon: Imaging pulse wave propagation in human retinal vessels using full-field swept-source optical coherence tomography. Optics Letters, no. 40, pp. 4771-4774, 2015
    BibTeX Link Link
    @article{Spahr2015,
       author = {Spahr, Hendrik and Hillmann, Dierck and Hain, Carola and Pfäffle, Clara and Sudkamp, Helge and Franke, Gesa and Hüttmann, Gereon},
       title = {Imaging pulse wave propagation in human retinal vessels using full-field swept-source optical coherence tomography},
       journal = {Optics Letters},
       volume = {40},
       number = {20},
       pages = {4771-4774},
       abstract = {We demonstrate a new noninvasive method to assess biomechanical properties of the retinal vascular system. Phase-sensitive full-field swept-source optical coherence tomography (PhS-FF-SS-OCT) is used to investigate retinal vascular dynamics at unprecedented temporal resolution. The motion of retinal tissue that is induced by expansion of the vessels therein is measured with an accuracy of about 10 nm. The pulse shapes of arterial and venous pulsations, their temporal delays, as well as the frequency-dependent pulse propagation through the capillary bed, are determined. For the first time, imaging speed and motion sensitivity are sufficient for a direct measurement of pulse waves propagating with more than 600 mm/s in retinal vessels of a healthy young subject.},
       keywords = {Optical coherence tomography
    Ophthalmology
    Time-resolved imaging
    Functional monitoring and imaging},
       DOI = {10.1364/OL.40.004771},
       url = {http://ol.osa.org/abstract.cfm?URI=ol-40-20-4771},
       year = {2015},
       type = {Journal Article}
    }
    
  • Spahr, Hendrik and Hain, Carola and Sudkamp, Helge and Franke, Gesa and Hillmann, Dierck and Huttmann, Gereon: Functional Microangiography of in vivo human retina by Full-Field OCT. Investigative Ophthalmology & Visual Science, no. 56, pp. 5974-5974, 2015
    BibTeX Link
    @article{Spahr2015,
       author = {Spahr, Hendrik and Hain, Carola and Sudkamp, Helge and Franke, Gesa and Hillmann, Dierck and Huttmann, Gereon},
       title = {Functional Microangiography of in vivo human retina by Full-Field OCT},
       journal = {Investigative Ophthalmology & Visual Science},
       volume = {56},
       number = {7},
       pages = {5974-5974},
       abstract = { PurposeOCT based functional microangiography of the retina requires high speed acquisition of a large number of volumetric datasets. Imaging speed of conventional scanning OCT devices is limited by the applicable radiant power and the mechanics used to scan the focused beam over the desired field of view. Full-Field Swept-Source OCT (FF-SS-OCT) resolves both issues, using an areal illumination, which dramatically increases the allowed amount of radiation, and an ultrafast camera for a highly parallelized acquisition.  MethodsThe retina of healthy volunteers was illuminated with wavelengths between 816 and 867 nm by the extended beam of a tunable laser (Broadsweeper, Superlum). Retinal irradiance was below the maximum permissable exposure (MPE). Light backscattered from the retina was imaged onto an ultrafast CMOS camera (SA-Z, Photron), where it interfered with an extended reference beam. From a series of interference images at different wavelengths, volumetric OCT images of the retina were reconstructed.  ResultsWe demonstrate in vivo retinal imaging at 9.9 billion voxels per second (40 million A-scans/s with 256 axial pixels). Sacrificing depth resolution by reducing the number of axial pixels, the A-scan rate was increased to more than 1 billion A-scans per second. FF-SS-OCT allowed imaging of all important retinal structures with good quality at unprecedented imaging speed (see fig. 1). Fast volumetric imaging at up to 3000 volumes/s was used to visualize small capillaries and to analyze the pulsation of retinal arteries and veins (see fig. 2). Imaging time for an area of 4 mm x 2 mm (896 x 368 A-scans) was only 316 µs. The high volume rate and the inherent phase stability enabled quantitative measurement of the change of retinal thickness due to blood pulsation with approx. 10 nm precision. A delay of the venous pulsation with respect to the arteries was observed (approx. 11 ms). The amplitudes of higher frequency components of the venous pulsation were considerably attenuated.  ConclusionsFF-SS-OCT provides fast volumetric imaging of the retina with good image quality. The capillary network can be analyzed with high spatial and temporal resolution. Analysis of retinal pulsation may provide information on pathological changes of vessels and capillaries. Angiographic OCT acquired with the FF-SS-OCT setup. Functional angiography showing the pulsation of retinal artery and vein.},
       ISSN = {1552-5783},
       url = {http://dx.doi.org/},
       year = {2015},
       type = {Journal Article}
    }
    
  • Horstmann, J. and Spahr, H. and Buj, C. and Munter, M. and Brinkmann, R.: Full-field speckle interferometry for non-contact photoacoustic tomography. Phys Med Biol, no. 60, pp. 4045-58, 2015
    BibTeX Link
    @article{Horstmann2015,
       author = {Horstmann, J. and Spahr, H. and Buj, C. and Munter, M. and Brinkmann, R.},
       title = {Full-field speckle interferometry for non-contact photoacoustic tomography},
       journal = {Phys Med Biol},
       volume = {60},
       number = {10},
       pages = {4045-58},
       note = {1361-6560
       abstract = {A full-field speckle interferometry method for non-contact and prospectively high speed Photoacoustic Tomography is introduced and evaluated as proof of concept. Thermoelastic pressure induced changes of the objects topography are acquired in a repetitive mode without any physical contact to the object. In order to obtain high acquisition speed, the object surface is illuminated by laser pulses and imaged onto a high speed camera chip. In a repetitive triple pulse mode, surface displacements can be acquired with nanometre sensitivity and an adjustable sampling rate of e.g. 20 MHz with a total acquisition time far below one second using kHz repetition rate lasers. Due to recurring interferometric referencing, the method is insensitive to thermal drift of the object due to previous pulses or other motion. The size of the investigated area and the spatial and temporal resolution of the detection are scalable. In this study, the approach is validated by measuring a silicone phantom and a porcine skin phantom with embedded silicone absorbers. The reconstruction of the absorbers is presented in 2D and 3D. The sensitivity of the measurement with respect to the photoacoustic detection is discussed. Potentially, Photoacoustic Imaging can be brought a step closer towards non-anaesthetized in vivo imaging and new medical applications not allowing acoustic contact, such as neurosurgical monitoring or burnt skin investigation.},
       ISSN = {0031-9155},
       DOI = {10.1088/0031-9155/60/10/4045},
       year = {2015},
       type = {Journal Article}
    }
    

  • Spahr, Hendrik and Hillmann, Dierck and Hain, Carola and Pfäffle, Clara and Sudkamp, Helge and Franke, Gesa and Hüttmann, Gereon: Imaging vascular dynamics in human retina using full-field swept-source optical coherence tomography (Conference Presentation). no. 9697, pp. 96970E-96970E-1,
    BibTeX Link
    @inproceedings{Spahr2016,
       author = {Spahr, Hendrik and Hillmann, Dierck and Hain, Carola and Pfäffle, Clara and Sudkamp, Helge and Franke, Gesa and Hüttmann, Gereon},
       title = {Imaging vascular dynamics in human retina using full-field swept-source optical coherence tomography (Conference Presentation)},
       volume = {9697},
       pages = {96970E-96970E-1},
       note = {10.1117/12.2214303},
       abstract = {We demonstrate a new non-invasive method to assess the functional condition of the retinal vascular system. Phase-sensitive full-field swept-source optical coherence tomography (PhS-FF-SS-OCT) is used to investigate retinal vascular dynamics at unprecedented temporal resolution. Motion of retinal tissue, that is induced by expansion of the vessels therein, is measured with an accuracy of about 10 nm. The pulse shape of arterial and venous pulsation, their temporal delay as well as the frequency dependent pulse propagation through the capillary bed are determined. For the first time, imaging speed and motion sensitivity are sufficient for a direct measurement of pulse waves propagating with more than 600 mm/s in retinal vessels of a healthy young subject.},
       url = {http://dx.doi.org/10.1117/12.2214303},
       type = {Conference Proceedings}
    }
    
  • Spahr, Hendrik and Rudolph, Linda and Muller, Heike and Birngruber, Reginald and Huttmann, Gereon: Imaging of photothermal tissue expansion via phase sensitive optical coherence tomography. no. 8213, pp. 82131S, SPIE,
    BibTeX
    @inproceedings{Spahr2012,
       author = {Spahr, Hendrik and Rudolph, Linda and Muller, Heike and Birngruber, Reginald and Huttmann, Gereon},
       title = {Imaging of photothermal tissue expansion via phase sensitive optical coherence tomography},
       editor = {Joseph, A. Izatt and James, G. Fujimoto and Valery, V. Tuchin},
       publisher = {SPIE},
       volume = {8213},
       pages = {82131S},
    
    }