Solid Chemical Radiation Dosimeter Semiannual Report

Temperature and X-irradiation strength effects on acid production and color changes in solid chemical radiation dosimete

Solid chemical radiation dosimeter Annual report

Solid chemical system for charged particle dosimetr

MEMS tunable VCSEL light source for ultrahigh speed 60kHz - 1MHz axial scan rate and long range centimeter class OCT imaging

This paper demonstrates new wavelength swept light source technology, MEMS tunable VCSELs, for OCT imaging. The VCSEL achieves a combination of ultrahigh sweep speeds, wide spectral tuning range, flexibility in sweep trajectory, and extremely long coherence length, which cannot be simultaneously achieved with other technologies. A second generation prototype VCSEL is optically pumped at 980nm and a low mass electrostatically tunable mirror enables high speed wavelength tuning centered at ~1310nm with ~110nm of tunable bandwidth. Record coherence length >100mm enables extremely long imaging range. By changing the drive waveform, a single 1310nm VCSEL was driven to sweep at speeds from 100kHz to 1.2MHz axial scan rate with unidirectional and bidirectional high duty cycle sweeps. We demonstrate long range and high resolution 1310nm OCT imaging of the human anterior eye at 100kHz axial scan rate and imaging of biological samples at speeds of 60kHz - 1MHz. A first generation 1050nm device is shown to sweep over 100nm. The results of this study suggest that MEMS based VCSEL swept light source technology has unique performance characteristics and will be a critical technology for future ultrahigh speed and long depth range OCT imaging.National Institutes of Health (U.S.) (2R44CA10167-05)National Institutes of Health (U.S.) (R01-EY011289-25)National Institutes of Health (U.S.) (R01-EY01356-06)National Institutes of Health (U.S.) (R01-EY013178-11)National Institutes of Health (U.S.) (R01-CA075289-15)United States. Air Force Office of Scientific Research (FA9550-10-1-0063)United States. Air Force Office of Scientific Research (FA9550-10-1-0551)Thorlabs, Inc

Reproducibility of a Long-Range Swept-Source Optical Coherence Tomography Ocular Biometry System and Comparison with Clinical Biometers

Objective To demonstrate a novel swept source optical coherence tomography (SS-OCT) imaging device using a vertical cavity surface-emitting laser (VCSEL) capable of imaging the full eye length and to introduce a method using this device for noncontact ocular biometry. To compare the measurements of intraocular distances using this SS-OCT instrument with commercially available optical and ultrasound biometers. To evaluate the intersession reproducibility of measurements of intraocular distances using SS-OCT. Design Evaluation of technology. Participants Twenty eyes of 10 healthy subjects imaged at the New England Eye Center at Tufts Medical Center and Massachusetts Institute of Technology between May and September 2012. Methods Averaged central depth profiles were extracted from volumetric SS-OCT datasets. The intraocular distances, such as central corneal thickness (CCT), aqueous depth (AD), anterior chamber depth (ACD), crystalline lens thickness (LT), vitreous depth (VD), and axial length (AL), were measured and compared with a partial coherence interferometry device (IOLMaster; Carl Zeiss Meditec, Inc., Dublin, CA) and an immersion ultrasound (IUS) A-scan biometer (Axis-II PR; Quantel Medical, Inc., Cournon d'Auvergne Cedex, France). Main Outcome Measures Reproducibility of the measurements of intraocular distances, correlation coefficients, and intraclass correlation coefficients. Results The standard deviations of the repeated measurements of intraocular distances using SS-OCT were 6 μm (CCT), 16 μm (ACD), 14 μm (AD), 13 μm (LT), 14 μm (VD), and 16 μm (AL). Strong correlations among all 3 biometric instruments were found for AL (r > 0.98). The AL measurement using SS-OCT correlates better with the IOLMaster (r=0.998) than with IUS (r=0.984). The SS-OCT and IOLMaster measured higher AL values than ultrasound (175 and 139 μm, respectively). No statistically significant difference in ACD between the optical (SS-OCT or IOLMaster) and ultrasound methods was detected. High intersession reproducibility of SS-OCT measurements of all intraocular distances was observed with intraclass correlation coefficients >0.99. Conclusions The SS-OCT using VCSEL technology enables full eye length imaging and high-precision, noncontact ocular biometry. The measurements with the prototype SS-OCT instrument correlate well with commercial biometers. The SS-OCT biometry has the potential to provide clinically useful comprehensive biometric parameters for pre- and postoperative eye evaluation.National Institutes of Health (U.S.) (Grant R01-EY011289-27)National Institutes of Health (U.S.) (Grant R01-EY013178-12)National Institutes of Health (U.S.) (Grant R01-EY013516-09)National Institutes of Health (U.S.) (Grant R01-EY019029-04)National Institutes of Health (U.S.) (Grant R44EY022864-01)National Institutes of Health (U.S.) (Grant R01-CA075289-16)National Institutes of Health (U.S.) (Grant R01-NS057476-05)National Institutes of Health (U.S.) (Grant R44CA101067-05)United States. Air Force Office of Scientific Research (Grant FA9550-10-1-0551)United States. Air Force Office of Scientific Research (Grant FA9550-10-1-0063)Thorlabs, Inc

Acquisition, processing and display of gated cardiac scintigrams

An improved method for non-traumatic and essentially noninvasive evaluation of left ventricular (LV) function with /sup 99m/Tc as the tracer was developed. This method combines previously used EKG gating techniques for cardiac blood pool visualization with new computerized acquisition, processing and display techniques. An Anger camera, a small computer, and a physiological synchronizer are used to acquire a sequence of eight scintigrams which span the entire cardiac cycle. Under our present protocol two twenty-minute sequences are obtained, one an LAO (50$sup 0$) projection, the other an RAO (30$sup 0$) projection. Subsequently these images are processed on-line with a digital filter to increase definition of the cardiac borders. The eight images are then displayed sequentially on a specially designed electronic monitor to give an impression of the beating heart somewhat analogous to that obtained with invasive contrast angiography. (auth

Recent advances in MEMS-VCSELs for high performance structural and functional SS-OCT imaging

Since the first demonstration of swept source optical coherence tomography (SS-OCT) imaging using widely tunable micro-electromechanical systems vertical cavity surface-emitting lasers (MEMS-VCSELs) in 2011, VCSEL-based SSOCT has advanced in both device and system performance. These advances include extension of MEMS-VCSEL center wavelength to both 1060nm and 1300nm, improved tuning range and tuning speed, new SS-OCT imaging modes, and demonstration of the first electrically pumped devices. Optically pumped devices have demonstrated continuous singlemode tuning range of 150nm at 1300nm and 122nm at 1060nm, representing a fractional tuning range of 11.5%, which is nearly a factor of 3 greater than the best reported MEMS-VCSEL tuning ranges prior to 2011. These tuning ranges have also been achieved with wavelength modulation rates of >500kHz, enabling >1 MHz axial scan rates. In addition, recent electrically pumped devices have exhibited 48.5nm continuous tuning range around 1060nm with 890kHz axial scan rate, representing a factor of two increase in tuning over previously reported electrically pumped MEMS-VCSELs in this wavelength range. New imaging modes enabled by optically pumped devices at 1060nm and 1300nm include full eye length imaging, pulsatile Doppler blood flow imaging, high-speed endoscopic imaging, and hand-held wide-field retinal imaging.National Institutes of Health (U.S.) (Grant R44EY022864-01)National Institutes of Health (U.S.) (Grant R44EY022864-02)National Institutes of Health (U.S.) (Grant R44CA101067-05)National Institutes of Health (U.S.) (Grant R44CA101067-06)National Institutes of Health (U.S.) (Grant R44CA101067-07)National Institutes of Health (U.S.) (Grant R01-EY011289-26)National Institutes of Health (U.S.) (Grant R01-CA075289-15)National Institutes of Health (U.S.) (Grant R01-EY013178-12)National Institutes of Health (U.S.) (Grant R01-EY013516-09)National Institutes of Health (U.S.) (Grant R01-EY018184-05)National Institutes of Health (U.S.) (Grant R01-NS057476-05)United States. Air Force Office of Scientific Research (Grant FA9550-10-1-0551)United States. Air Force Office of Scientific Research (Grant FA9550-12-1-0499)Thorlabs, Inc

Triggered optical coherence tomography for capturing rapid periodic motion

Quantitative cross-sectional imaging of vocal folds during phonation is potentially useful for diagnosis and treatments of laryngeal disorders. Optical coherence tomography (OCT) is a powerful technique, but its relatively low frame rates makes it challenging to visualize rapidly vibrating tissues. Here, we demonstrate a novel method based on triggered laser scanning to capture 4-dimensional (4D) images of samples in motu at audio frequencies over 100 Hz. As proof-of-concept experiments, we applied this technique to imaging the oscillations of biopolymer gels on acoustic vibrators and aerodynamically driven vibrations of the vocal fold in an ex vivo calf larynx model. Our results suggest that triggered 4D OCT may be useful in understanding and assessing the function of vocal folds and developing novel treatments in research and clinical settings

Ultra-high resolution Fourier domain optical coherence tomography for old master paintings

In the last 10 years, Optical Coherence Tomography (OCT) has been successfully applied to art conservation, history and archaeology. OCT has the potential to become a routine non-invasive tool in museums allowing cross-section imaging anywhere on an intact object where there are no other methods of obtaining subsurface information. While current commercial OCTs have shown potential in this field, they are still limited in depth resolution (> 4 μm in paint and varnish) compared to conventional microscopic examination of sampled paint cross-sections (~1 μm). An ultrahigh resolution fiber-based Fourier domain optical coherence tomography system with a constant axial resolution of 1.2 μm in varnish or paint throughout a depth range of 1.5 mm has been developed. While Fourier domain OCT of similar resolution has been demonstrated recently, the sensitivity roll-off of some of these systems are still significant. In contrast, this current system achieved a sensitivity roll-off that is less than 2 dB over a 1.2 mm depth range with an incident power of ~1 mW on the sample. The high resolution and sensitivity of the system makes it convenient to image thin varnish and glaze layers with unprecedented contrast. The non-invasive 'virtual' cross-section images obtained with the system show the thin varnish layers with similar resolution in the depth direction but superior clarity in the layer interfaces when compared with conventional optical microscope images of actual paint sample cross-sections obtained microdestructively

Choriocapillaris and Choroidal Microvasculature Imaging with Ultrahigh Speed OCT Angiography

We demonstrate in vivo choriocapillaris and choroidal microvasculature imaging in normal human subjects using optical coherence tomography (OCT). An ultrahigh speed swept source OCT prototype at 1060 nm wavelengths with a 400 kHz A-scan rate is developed for three-dimensional ultrahigh speed imaging of the posterior eye. OCT angiography is used to image three-dimensional vascular structure without the need for exogenous fluorophores by detecting erythrocyte motion contrast between OCT intensity cross-sectional images acquired rapidly and repeatedly from the same location on the retina. En face OCT angiograms of the choriocapillaris and choroidal vasculature are visualized by acquiring cross-sectional OCT angiograms volumetrically via raster scanning and segmenting the three-dimensional angiographic data at multiple depths below the retinal pigment epithelium (RPE). Fine microvasculature of the choriocapillaris, as well as tightly packed networks of feeding arterioles and draining venules, can be visualized at different en face depths. Panoramic ultra-wide field stitched OCT angiograms of the choriocapillaris spanning ~32 mm on the retina show distinct vascular structures at different fundus locations. Isolated smaller fields at the central fovea and ~6 mm nasal to the fovea at the depths of the choriocapillaris and Sattler's layer show vasculature structures consistent with established architectural morphology from histological and electron micrograph corrosion casting studies. Choriocapillaris imaging was performed in eight healthy volunteers with OCT angiograms successfully acquired from all subjects. These results demonstrate the feasibility of ultrahigh speed OCT for in vivo dye-free choriocapillaris and choroidal vasculature imaging, in addition to conventional structural imaging.National Institutes of Health (U.S.) (NIH R01-EY011289-27)National Institutes of Health (U.S.) (NIH R01-EY013178-12)National Institutes of Health (U.S.) (NIH R44-EY022864-01)National Institutes of Health (U.S.) (NIH R01-CA075289-16)United States. Air Force Office of Scientific Research (AFOSR FA9550-10-1-0551)United States. Air Force Office of Scientific Research (AFOSR FA9550-12-1-0499