Eric J. Seibel

Ultra-compact fiber-optic two-photon microscope for functional fluorescence imaging in vivo

We present a small, lightweight two-photon fiberscope and demonstrate its suitability for functional imaging in the intact brain. Our device consists of a hollow-core photonic crystal fiber for efficient delivery of near-IR femtosecond laser pulses, a spiral fiber-scanner for resonant beam steering, and a gradient-index lens system for fluorescence excitation, dichroic beam splitting, and signal collection. Fluorescence light is remotely detected using a standard photomultiplier tube. All optical components have 1 mm dimensions and the microscopes headpiece weighs only 0.6 grams. The instrument achieves micrometer resolution at frame rates of typically 25 Hz with a field-of-view of up to 200 microns. We demonstrate functional imaging of calcium signals in Purkinje cell dendrites in the cerebellum of anesthetized rats. The microscope will be easily portable by a rat or mouse and thus should enable functional imaging in freely behaving animals.

Virtual reality pain control during burn wound debridement in the hydrotank.

ObjectiveMost burn-injured patients rate their pain during burn wound debridement as severe to excruciating. We explored the adjunctive use of water-friendly, immersive virtual reality (VR) to distract patients from their pain during burn wound debridement in the hydrotherapy tank (hydrotank). SettingThis study was conducted on inpatients at a major regional burn center. PatientsEleven hospitalized inpatients ages 9 to 40 years (mean age, 27 y) had their burn wounds debrided and dressed while partially submerged in the hydrotank. InterventionAlthough a nurse debrided the burn wound, each patient spent 3 minutes of wound care with no distraction and 3 minutes of wound care in VR during a single wound care session (within-subject condition order randomized). Outcome MeasuresThree 0 to 10 graphic rating scale pain scores (worst pain, time spent thinking about pain, and pain unpleasantness) for each of the 2 treatment conditions served as the primary dependent variables. ResultsPatients reported significantly less pain when distracted with VR [eg, “worst pain” ratings during wound care dropped from “severe” (7.6) to “moderate” (5.1)]. The 6 patients who reported the strongest illusion of “going inside” the virtual world reported the greatest analgesic effect of VR on worst pain ratings, dropping from severe pain (7.2) in the no VR condition to mild pain (3.7) during VR. ConclusionsResults provide the first available evidence from a controlled study that immersive VR can be an effective nonpharmacologic pain reduction technique for burn patients experiencing severe to excruciating pain during wound care. The potential applications of VR analgesia to other painful procedures (eg, movement or exercise therapy) and other pain populations are discussed.

Scanning fiber endoscopy with highly flexible, 1-mm catheterscopes for wide-field, full-color imaging

In modern endoscopy, wide field of view and full color are considered necessary for navigating inside the body, inspecting tissue for disease and guiding interventions such as biopsy or surgery. Current flexible endoscope technologies suffer from reduced resolution when device diameter shrinks. Endoscopic procedures today, using coherent fiber-bundle technology on the scale of 1 mm, are performed with such poor image quality that the clinicians vision meets the criteria for legal blindness. Here, we review a new and versatile scanning fiber-imaging technology and describe its implementation for ultrathin and flexible endoscopy. This scanning fiber endoscope (SFE) or catheterscope enables high-quality, laser-based, video imaging for ultrathin clinical applications, while also providing new options for in vivo biological research of subsurface tissue and high resolution fluorescence imaging.

Virtual Reality as an Adjunctive Non-pharmacologic Analgesic for Acute Burn Pain During Medical Procedures

IntroductionExcessive pain during medical procedures is a widespread problem but is especially problematic during daily wound care of patients with severe burn injuries.MethodsBurn patients report 35–50% reductions in procedural pain while in a distracting immersive virtual reality, and fMRI brain scans show associated reductions in pain-related brain activity during VR. VR distraction appears to be most effective for patients with the highest pain intensity levels. VR is thought to reduce pain by directing patients’ attention into the virtual world, leaving less attention available to process incoming neural signals from pain receptors.ConclusionsWe review evidence from clinical and laboratory research studies exploring Virtual Reality analgesia, concentrating primarily on the work ongoing within our group. We briefly describe how VR pain distraction systems have been tailored to the unique needs of burn patients to date, and speculate about how VR systems could be tailored to the needs of other patient populations in the future.

Three-dimensional imaging of single isolated cell nuclei using optical projection tomography

A method is presented for imaging single isolated cell nuclei in 3D, employing computed tomographic image reconstruction. The system uses a scanning objective lens to create an extended depth-of-field (DOF) image similar to a projection or shadowgram. A microfabricated inverted v-groove allows a microcapillary tube to be rotated with sub-micron precision, and refractive index matching within 0.02 both inside and outside the tube keeps optical distortion low. Cells or bare cell nuclei are injected into the tube and imaged in 250 angular increments from 0 to 180 degrees to collect 250 extended DOF images. After these images are further aligned, the filtered backprojection algorithm is applied to compute the 3D image. To estimate the cutoff spatial frequency in the projection image, a spatial frequency ratio function is calculated by comparing the extended depth-of-field image of a typical cell nucleus to the fixed focus image. To assess loss of resolution from fixed focus image to extended DOF image to 3D reconstructed image, the 10-90% rise distance is measured for a dyed microsphere. The resolution is found to be 0.9 microm for both extended DOF images and 3D reconstructed images. Surface and translucent volume renderings and cross-sectional slices of the 3D images are shown of a stained nucleus from fibroblast and cancer cell cultures with added color histogram mapping to highlight 3D chromatin structure.

Coherent Raman scanning fiber endoscopy

Coherent Raman scattering methods allow for label-free imaging of tissue with chemical contrast and high spatial and temporal resolution. However, their imaging depth in scattering tissue is limited to less than 1 mm, requiring the development of endoscopes to obtain images deep inside the body. Here, we describe a coherent Raman endoscope that provides stimulated Raman scattering images at seven frames per second using a miniaturized fiber scanner, a custom-designed objective lens, and an optimized scheme for collection of scattered light from the tissue. We characterize the system and demonstrate chemical selectivity in mouse tissue images.

Using fMRI to study the neural correlates of virtual reality analgesia

Excessive pain during medical procedures, such as burn wound dressing changes, is a widespread medical problem and is especially challenging for children. This article describes the rationale behind virtual reality (VR) pain distraction, a new non-pharmacologic adjunctive analgesia, and gives a brief summary of empirical studies exploring whether VR reduces clinical procedural pain. Results indicate that patients using VR during painful medical procedures report large reductions in subjective pain. A neuroimaging study measuring the neural correlates of VR analgesia is described in detail. This functional magnetic resonance imaging pain study in healthy volunteers shows that the large drops in subjective pain ratings during VR are accompanied by large drops in pain-related brain activity. Together the clinical and laboratory studies provide converging evidence that VR distraction is a promising new non-pharmacologic pain control technique.

54.3: Modeling and Control of the Resonant Fiber Scanner for Laser Scanning Display or Acquisition

The resonant fiber scanner produces a flying laser spot scan for display or image acquisition purposes. Dynamic nonlinearities during large amplitude vibrations of the resonant fiber scanner result in distortions in the two-dimensional scan pattern and the acquired images. A dynamic model which includes the fibers dynamic nonlinearities has been developed to understand the nonlinear behavior and as the basis of a controller to remove the scan distortion. A robust state-space controller has been implemented to force the resonant fiber scanner to follow a spiral scan pattern. Acquired images at 250×250 pixel resolution demonstrate improved image fidelity over previous images taken with open-loop scanning.

Targeted detection of murine colonic dysplasia in vivo with flexible multispectral scanning fiber endoscopy

Gastrointestinal cancers are heterogeneous and can overexpress several protein targets that can be imaged simultaneously on endoscopy using multiple molecular probes. We aim to demonstrate a multispectral scanning fiber endoscope for wide-field fluorescence detection of colonic dysplasia. Excitation at 440, 532, and 635 nm is delivered into a single spiral scanning fiber, and fluorescence is collected by a ring of light-collecting optical fibers placed around the instrument periphery. Specific-binding peptides are selected with phage display technology using the CPC;Apc mouse model of spontaneous colonic dysplasia. Validation of peptide specificity is performed on flow cytometry and in vivo endoscopy. The peptides KCCFPAQ, AKPGYLS, and LTTHYKL are selected and labeled with 7-diethylaminocoumarin-3-carboxylic acid (DEAC), 5-carboxytetramethylrhodamine (TAMRA), and CF633, respectively. Separate droplets of KCCFPAQ-DEAC, AKPGYLS-TAMRA, and LTTHYKL-CF633 are distinguished at concentrations of 100 and 1 μM. Separate application of the fluorescent-labeled peptides demonstrate specific binding to colonic adenomas. The average target/background ratios are 1.71 ± 0.19 and 1.67 ± 0.12 for KCCFPAQ-DEAC and AKPGYLS-TAMRA, respectively. Administration of these two peptides together results in distinct binding patterns in the blue and green channels. Specific binding of two or more peptides can be distinguished in vivo using a novel multispectral endoscope to localize colonic dysplasia on real-time wide-field imaging.

Single-fiber flexible endoscope: general design for small size, high resolution, and wide field of view

Flexible endoscopes currently used in medicine have a fundamental tradeoff. Either resolution or field of view (FOV) is sacrificed when the scope diameter is less than 3 mm, since the minimum pixel size is usually greater than 4 microns in a pixel-array such as a camera or fiber bundle. Thus, the number of pixels within the image plane determines the minimum size of a conventional scope. However, an image plane is not required for image acquisition using a scanning single-fiber scope. Both high resolution and wide FOV are possible in a scanning single-fiber scope of 1 to 2 mm in diameter. The technical challenge is to produce a two- dimensional scanned beam of light at the distal tip of the scope. By manipulating a resonant fiberoptic cantilever as the optical scanner, various 2-D scan patterns can be produced. The general design concepts and analyses of the fiberoptic scanner for scaling to small size and high resolution/FOV are reviewed. In our initial experimental tests, the size of the photon detector in a fiberoptic scanning scope is demonstrated to not affect image resolution, unlike existing endoscopes with pixel-based detector systems.