Yoshihiro Takeda

Phase tomography by X-ray talbot interferometry for biological imaging

The X-ray phase tomography of biological samples is reported, which is based on X-ray Talbot interferometry. Its imaging principle is described in detail, and imaging results obtained for a cancerous rabbit liver and a mouse tail with synchrotron radiation are presented. Because an amplitude grating is needed to construct an X-ray Talbot interferometer, a high-aspect-ratio grating pattern was fabricated by X-ray lithography and gold electroplating. X-ray Talbot interferometry has an advantage that it functions with polychromatic cone-beam X-rays. Finally, the compatibility with a compact X-ray source is discussed.

High-speed X-ray phase imaging and X-ray phase tomography with Talbot interferometer and white synchrotron radiation

X-ray Talbot interferometry, which uses two transmission gratings, has the advantage that broad energy bandwidth x-rays can be used. We demonstrate the use of white synchrotron radiation for high-speed X-ray phase imaging and tomography in combination with an X-ray Talbot interferometer. The moiré fringe visibility over 20% was attained, enabling quantitative phase measurement. X-ray phase images with a frame rate of 500 f/s and an X-ray phase tomogram with a scan time of 0.5 s were obtained successfully. This result suggests a breakthrough for time-resolved three-dimensional observation of objects that weakly absorb X-rays, such as soft material and biological objects.

Efficiency of capturing a phase image using cone-beam x-ray Talbot interferometry

We assesses the efficiency of x-ray Talbot interferometry (XTI), a technique based on the Talbot effect for measuring a wavefront gradient, in terms of how quickly it can capture a high-quality phase image with a large signal-to-noise ratio for a given incident photon number. Photon statistics cause errors in the phase of the moiré fringes and impose a detection limit on the wavefront gradient. The relation between the incident photon number and the detection limit is determined, and a figure of merit of XTI for a monochromatic cone beam is then defined. The dependence of the figure of merit on optical system parameters, such as grating pitch and position, is then discussed. The effects of varying the pattern height and linewidth of the second grating are shown for rectangular and trapezoidal teeth. Finally, we show how to design a practical cone-beam Talbot interferometer for certain boundary conditions.

Formation and ejection of cluster ions from a liquid beam of aniline-ethanol solution by laser photoionization

Abstract A simple technique for making a continuous liquid flow in a vacuum (liquid beam) was developed and combined with multiphoton ionization and time-of-flight mass spectrometry. This technique was applied to the resonance two-photon ionization of aniline in ethanol (0.2–3 M). Binary cluster ions of aniline and ethanol together with a trace amount of aniline cluster ions were ejected from a liquid beam of an aniline—ethanol solution when the liquid beam was irradiated by a 270 nm laser exceeding a certain threshold power. The dependence of the threshold power on the aniline concentration reveals that Coulomb explosion of the ions produced in the liquid beam causes ion ejection from the beam. The critical ion density for the Coulomb explosion was found to be independent of the aniline concentration in the range of 0.2–3 M. The finding suggests that clusters of aniline molecules are formed in the ethanol solution.

X-Ray Phase Imaging with Single Phase Grating

X-ray phase imaging with a single phase grating based on the fractional Talbot effect is described. A phase grating with an 8 µm pitch was placed behind a weakly absorbing object and illuminated with partially coherent 17.7 keV X-rays. Intensity patterns downstream of the grating were recorded with a high-resolution image detector. By the fringe scanning method, an X-ray wavefront inclination by the object was obtained. Phase tomography was performed and the three-dimensional structure of a piece of a polymer blend was revealed with an 8 µm spatial resolution and a 9 mg/cm3 detection limit of density deviation.

Differential Phase X-ray Imaging Microscopy with X-ray Talbot Interferometer

A new type of differential phase X-ray imaging microscopy attained by combination of an X-ray imaging microscope and an X-ray Talbot interferometer is described. An X-ray Talbot interferometer was set up so that a moire-fringe pattern appeared on the image plane of an X-ray imaging microscope. The wavefront inclination (differential phase shift) caused by a weakly absorbing polymer sample was measured from the fringes using the fringe-scanning method and with a spatial resolution of 1 µm. Phase tomography was also performed and the internal structures of a piece of polymer blend were depicted.

Sensitivity of X-ray Phase Imaging Based on Talbot Interferometry

The sensitivity of X-ray phase imaging based on Talbot interferometry is discussed. In order to evaluate the superiority of the technique to the conventional absorption-contrast method, which relies on X-ray absorption, a criterion is proposed. An experimental result of X-ray phase imaging with a Talbot interferometer is compared with the criterion. The criterion is also available for X-ray phase imaging based on Talbot–Lau interferometry. The advantage of X-ray phase imaging based on Talbot(–Lau) interferometry is more prominent when smaller structures are observed with smaller pixels.

Microcrystal delivery by pulsed liquid droplet for serial femtosecond crystallography

A liquid-droplet injector has been developed that delivers pristine microcrystals to an X-ray irradiation area for conducting serial femtosecond crystallography (SFX) with an X-ray free-electron laser (XFEL). By finely tuning the pulsed liquid droplets in time and space, a high hit rate of the XFEL pulses to microcrystals in the droplets was achieved for measurements using 5 µm tetragonal lysozyme crystals, which produced 4265 indexable diffraction images in about 30 min. The structure was determined at a resolution of 2.3 Å from <0.3 mg of protein. With further improvements such as reduction of the droplet size, liquid droplets have considerable potential as a crystal carrier for SFX with low sample consumption.

Impaired Vibration of Auditory Ossicles in Osteopetrotic Mice

In the middle ear, a chain of three tiny bones (ie, malleus, incus, and stapes) vibrates to transmit sound from the tympanic membrane to the inner ear. Little is known about whether and how bone-resorbing osteoclasts play a role in the vibration of auditory ossicles. We analyzed hearing function and morphological features of auditory ossicles in osteopetrotic mice, which lack osteoclasts because of the deficiency of either cytokine RANKL or transcription factor c-Fos. The auditory brainstem response showed that mice of both genotypes experienced hearing loss, and laser Doppler vibrometry revealed that the malleus behind the tympanic membrane failed to vibrate. Histological analysis and X-ray tomographic microscopy using synchrotron radiation showed that auditory ossicles in osteopetrotic mice were thicker and more cartilaginous than those in control mice. Most interestingly, the malleal processus brevis touched the medial wall of the tympanic cavity in osteopetrotic mice, which was also the case for c-Src kinase-deficient mice (with normal numbers of nonresorbing osteoclasts). Osteopetrotic mice showed a smaller volume of the tympanic cavity but had larger auditory ossicles compared with controls. These data suggest that osteoclastic bone resorption is required for thinning of auditory ossicles and enlargement of the tympanic cavity so that auditory ossicles vibrate freely.

Biomedical imaging by Talbot-type x-ray phase tomography

An X-ray Talbot interferometer for X-ray phase imaging and tomography was constructed using an amplitude grating of a gold pattern 8 μm in pitch and 30 μm in height developed by X-ray lithography and gold electroplating. The effective area of the grating was 20 mm x 20 mm, and was fully illuminated by synchrotron radiation at beamline 20XU, SPring-8, Japan. Almost whole body of a fish 3 cm in length was observed by phase tomography. Resulting images obtained with 0.07 nm and 0.045 nm X-rays revealed organs with bones in the same view successfully. A preliminary result of the combination with an X-ray imaging microscope is also presented, which was attempted to attain a higher spatial resolution. Finally, prospects of the compatibility with a conventional X-ray generator are discussed for practical applications such as clinical diagnoses.