Effect of echo artifacts on characterization of pulsatile tissues has been examined in neonatal cranial ultrasonic movies by characterizing pulsatile intensities with different regions of interest (ROIs). The pulsatile tissue, which is a key point in pediatric diagnosis of brain tissue, was detected from a heartbeat-frequency component in Fourier transform of a time-variation of 64 samples of echo intensity at each pixel in a movie fragment. The averages of pulsatile intensity and power were evaluated in two ROIs: common fan-shape and individual cranial-shape. The area of pulsatile region was also evaluated as the number of pixels where the pulsatile intensity exceeds a proper threshold. The extracranial pulsatile region was found mainly in the sections where mirror image was dominant echo artifact. There was significant difference of pulsatile area between two ROIs especially in the specific sections where mirror image was included, suggesting the suitability of cranial-shape ROI for statistical study on pulsatile tissues in brain. The normalized average of pulsatile power in the cranial-shape ROI exhibited most similar tendency to the normalized pulsatile area which was treated as a conventional measure in spite of its requirement of thresholding. It suggests the potential of pulsatile power as an alternative measure for pulsatile area in further statistical study of pulsatile tissues because it was neither affected by echo artifacts nor threshold.
Subject motion in a large number of diffusion weighted images (DWIs) for q-space analysis was detected and corrected by using a simple protocol to add multiple interleaved b0 images between each DWI set and at the very end of data acquisition. The realignment matrix was determined from each b0 image with respect to the first b0 image and the matrix was used to realign not only the b0 image itself but also its subsequent DWI set. Degree of improvement in q-space analysis was estimated by calculating total residual sum of squares (RSS) in bi-exponential curve fitting process and also on the fractional anisotropy (FA) of zero displacement (ZDP). The large RSS regions were considerably diminished by realignment at the edges between cerebral gyri and sulci and at the ventricle boundaries in the original images. The large RSS regions around basal ganglia and near the ventricles were kept even by realignment but considerably suppressed with the averaged b0 image for decay-curve estimation. The volume average of RSS was reduced by the maximum of 77% in four volunteers’ results with both the realignment and the averaged b0 images. The FA-ZDP images revealed the improvement by realignment such as the contrast of corpus callosum and suppression of abnormal FA at cerebral sulcus. The number of additional b0 images accounted for 3% of the total number of DWIs, which suggests its feasibility for future clinical application.
In order to detect the pulsatile tissues in neonatal cranial ultrasonic movies by avoiding probe-motion artifact, a time-frequency analysis has been performed in several movie fragments at typical three scenes: (a) a brain-lost, (b) a brain-captured and probe-stabilized, and (c) a brain-captured and probe-swayed ones. The pulsatile tissue, which is a key point of pediatric diagnosis, had successfully detected with an algorithm based on Fourier transform but it had required us to extract the probe-stabilized scene manually by visual observation of the movie. A spatial mean square of echo intensity Etot and a total AC power Ptot over a fan-shape of field of view were evaluated according to a power spectrum of a time-variation of 64 samples of echo intensity at each pixel in each movie fragment split from actual B-mode ultrasonic movies taken at coronal sections of a neonate. The results revealed that (1) significant low Etot was found at the brain-lost scene rather than that at the other scenes, and (2) lower Ptot was found at the probe-stabilized scene rather than the probe-swayed ones. This fact strongly suggests that the Etot and Ptot are promising features for automatic extraction of probe-stabilized scenes. It must lead to detect the pulsatile tissues selectively by avoiding probe-motion artifact and to realize systematic analysis of the whole of our extensive movie archives, which is useful not only for retrospective study of ischemic diseases but also for bedside diagnosis to stabilize the freehand ultrasonic probe.
By developing a computer-aided modeling system, the 3D shapes of infant's heart have been constructed interactively
from quality-limited CT images for rapid prototyping of biomodels. The 3D model was obtained by following interactive
steps: (1) rough region cropping, (2) outline extraction in each slice with locally-optimized threshold, (3) verification and
correction of outline overlap, (4) 3D surface generation of inside wall, (5) connection of inside walls, (6) 3D surface
generation of outside wall, (7) synthesis of self-consistent 3D surface. The manufactured biomodels revealed
characteristic 3D shapes of heart such as left atrium and ventricle, aortic arch and right auricle. Their real shape of cavity
and vessel is suitable for surgery planning and simulation. It is a clear advantage over so-called "blood-pool" model
which is massive and often found in 3D visualization of CT images as volume rendering perspective. The developed
system contributed both to quality improvement and to modeling-time reduction, which may suggest a practical approach
to establish a routine process for manufacturing heart biomodels. Further study on the system performance is now still in
progress.
Computational defect imaging has been performed in commercial substrates for electronic and photonic devices by
combining the transmission profile acquired with an imaging type of linear polariscope and the computational algorithm
to extract a small amount of birefringence. The computational images of phase retardation δ exhibited spatial
inhomogeneity of defect-induced birefringence in GaP, LiNbO3, and SiC substrates, which were not detected by
conventional 'visual inspection' based on simple optical refraction or transmission because of poor sensitivity. The
typical imaging time was less than 30 seconds for 3-inch diameter substrate with the spatial resolution of 200 μm, while
that by scanning polariscope was 2 hours to get the same spatial resolution. Since our proposed technique have been
achieved high sensitivity, short imaging time, and wide coverage of substrate materials, which are practical advantages
over the laboratory-scale apparatus such as X-ray topography and electron microscope, it is useful for nondestructive
inspection of various commercial substrates in production of electronic and photonic devices.
By real-time visual feedback of 3D scatter diagram of pulsatile tissue-motion, freehand ultrasonic diagnosis of neonatal
ischemic diseases has been assisted at the bedside. The 2D ultrasonic movie was taken with a conventional ultrasonic
apparatus (ATL HDI5000) and ultrasonic probes of 5-7 MHz with the compact tilt-sensor to measure the probe
orientation. The real-time 3D visualization was realized by developing an extended version of the PC-based visualization
system. The software was originally developed on the DirectX platform and optimized with the streaming SIMD
extensions. The 3D scatter diagram of the latest pulsatile tissues has been continuously generated and visualized as
projection image with the ultrasonic movie in the current section more than 15 fps. It revealed the 3D structure of
pulsatile tissues such as middle and posterior cerebral arteries, Willis ring and cerebellar arteries, in which pediatricians
have great interests in the blood flow because asphyxiated and/or low-birth-weight neonates have a high risk of ischemic
diseases such as hypoxic-ischemic encephalopathy and periventricular leukomalacia. Since the pulsatile tissue-motion is
due to local blood flow, it can be concluded that the system developed in this work is very useful to assist freehand
ultrasonic diagnosis of ischemic diseases in the neonatal cranium.
Three-dimensional shape of pulsatile tissue due to blood flow, which is one of key diagnostic features in ischemia, has
been constructed from 2D ultrasonic movies for assisting clinical diagnosis. The 2D ultrasonic movies
(640x480pixels/frame, 8bits/pixel, 33ms/frame) were taken with a conventional ultrasonic apparatus and an ultrasonic
probe, while measuring the probe orientations with a compact tilt-sensor. The 2D images of pulsatile strength were
obtained from each 2D ultrasonic movie by evaluating a heartbeat-frequency component calculated by Fourier transform
of a series of pixel values sampled at each pixel. The 2D pulsatile images were projected into a 3D domain to obtain a
3D grid of pulsatile strength according to the probe orientations. The 3D shape of pulsatile tissue was constructed by
determining the iso-surfaces of appropriate strength in the 3D grid. The shapes of pulsatile tissue examined in neonatal
crania clearly represented the 3D structures of several arteries such as middle cerebral artery, which is useful for
diagnosis of ischemic diseases. Since our technique is based on feature extraction in tissue dynamics, it is also useful for
homogeneous tissue, for which conventional 3D ultrasonogram is unsuitable due to unclear tissue boundary.
Pulsatile tissue-motion in the B-mode ultrasonogram of neonatal cranium has been visualized in the three-dimensional
(3-D) domain. A movie of 2-D ultrasonogram (640×480pixels/frame, 8bits/pixel, 33ms/frame), which was taken with a
conventional ultrasonogram apparatus (ATL HDI5000) and an ultrasonic probe combined with a compact tilt-sensor,
was captured and recorded together with the orientations of probe into a 2-D visualization system developed by
ourselves. The pulsatile strength was evaluated from a heartbeat-frequency component calculated by Fourier transform
of a series of pixel values as a function of time sampled at each pixel of the 2-D ultrasonogram. The 3-D image of
pulsatile strength was obtained by projecting the pulsatile strength on the several sections at different orientations of
probe. The 3-D images of pulsatile-strength clearly described characteristic 3-D structures of arteries such as the anterior,
middle and posterior cerebral arteries, Willis ring and cerebellar arteries. Since our technique is completely noninvasive,
it is very useful for neonates rested completely at incubators. Furthermore, it is effective approach to obtain a useful 3-D
ultrasonogram even in homogeneous tissues other than brain tissues, because it is easy to recognize the tissue boundary
by selective detection of special tissues with their own motion characteristics.
By developing a real-time visualization system, pulsatile tissue-motion caused by artery pulsation of blood flow has been
visualized continuously from a video stream of ultrasonogram in brightness mode. The system concurrently executes the
three processes: (1) capturing an input B-mode video stream (640×480 pixels/frame, 30 fps) into a ring buffer of 256
frames, (2) detecting intensity and phase of pulsatile tissue-motion at each pixel from a heartbeat-frequency component
in Fourier transform of a series of pixel value through the latest 64 frames as a function of time, and (3) generating an
output video-stream of pulsatile-phase image, in which the motion phase is superimposed as color gradation on an input
video-stream when the motion intensity exceeds a proper threshold. By optimizing the visualization software with the
streaming SIMD extensions, the pulsatile-phase image has been continuously updated at more than 10 fps, which was
enough to observe pulsatile tissue-motion in real time. Compared to the retrospective technique, the real-time
visualization had clear advantages not only in enabling bedside observation and quick snapshot of pulsatile tissue-motion
but also in giving useful feedback to probe handling for avoiding unwanted motion-artifacts, which may strongly assist
pediatricians in bedside diagnosis of ischemic diseases.
A new imaging technique has been developed for observing both strength and phase of pulsatile tissue-motion in a movie of brightness-mode ultrasonogram. The pulsatile tissue-motion is determined by evaluating the heartbeat-frequency component in Fourier transform of a series of pixel value as a function of time at each pixel in a movie of ultrasonogram (640x480pixels/frame, 8bit/pixel, 33ms/frame) taken by a conventional ultrasonograph apparatus (ATL HDI5000). In order to visualize both the strength and the phase of the pulsatile tissue-motion, we propose a pulsatile-phase image that is obtained by superimposition of color gradation proportional to the motion phase on the original ultrasonogram only at which the motion strength exceeds a proper threshold. The pulsatile-phase image obtained from a cranial ultrasonogram of normal neonate clearly reveals that the motion region gives good agreement with the anatomical shape and position of the middle cerebral artery and the corpus callosum. The motion phase is fluctuated with the shape of arteries revealing local obstruction of blood flow. The pulsatile-phase images in the neonates with asphyxia at birth reveal decreases of the motion region and increases of the phase fluctuation due to the weakness and local disturbance of blood flow, which is useful for pediatric diagnosis.
In order to develop a nondestructive technique for inspection of optical-grade LN wafers used as substrate to fabricate optoelectronic devices such as electro-optic modulator, a scanning IR polariscope (SIRP), which was developed to measure a small amount of residual strain in optically isotropic GaAs wafers, has been employed. It is demonstrated that the sensitivity of SIRP adopted for LN wafers is high enough to detect the change in refractive index caused by crystal defects, down to the order of 10-7. X-ray topography measurement is also carried out to confirm the usefulness of SIRP as an inspection tool of crystal defects in optical-grade LN wafers.
Using an optical-flow technique, we have quantitatively analyzed tissue motion due to artery pulsation accompanied with blood flow in a neonatal cranial ultrasonogram. The tissue motion vector was successfully calculated at each pixel in a series of echo images (32 frames, 640 X 480 pixels/frame, 8 bits/pixel, 33 ms/frame) taken in the brightness mode by using an ultrasound probe of 5.0 MHz. The optical-flow technique used was a gradient method combined with local optimization for 3 X 3 neighbors. From 2D mappings of tissue motion vectors and their time-sequence variations, it was found that the tissue motion due to artery pulsation revealed periodic to-and-fro motion synchronized with heartbeat (300 - 500 ms), clearly distinguishing from unwanted non-periodic motion due to the sway of neonatal head during diagnosis.
By using a high-sensitivity high-spatial-resolution scanning infrared polariscope, we have quantitatively measured a small amount of birefringence induced by residual strain in commercial wafers of III-V compound crystals. From the measurement results in commercial (100) wafers of GaAs grown by the liquid encapsulated Czhocralski method, it is found that the 2D distribution maps of absolute difference (Delta) n between the principal refractive indices exhibit fourfold symmetry accompanying some fine structure such as stripes or line-segment patterns. The magnitude of (Delta) n is about 5 X 10-5 in maximum and the principal axes of birefringence are approximately radially or tangentially aligned. From the detailed analysis of photoelastic effect on the (100) wafers, the in-plane components of residual strains: Syy - Szz and 2Syz are deduced from the measured (Delta) n and the principal angle of birefringence (psi) .
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