Yoshiki Kitsunezuka

Culture-Proven Neonatal Sepsis in Japanese Neonatal Care Units in 2006–2008

Background: Recent Japanese epidemiology of neonatal sepsis and its predominant pathogens has not been reported. It is also unknown whether there are center differences in the incidence of neonatal sepsis, including early-onset sepsis (EOS) and late-onset sepsis (LOS) in Japan. Objectives: To investigate the morbidity and characteristics of neonatal sepsis in recent years and the differences in the incidence of sepsis among Japanese neonatal care units. Methods: We retrospectively collected the data of newborn infants with culture-proven sepsis that occurred in five Japanese centers of perinatal care from 2006 to 2008. The incidence of sepsis was calculated, including EOS and LOS, and compared among centers. Results: Morbidity from sepsis occurred in 51/6,894 (0.74%) infants. The incidence of EOS and LOS was 0.13 and 0.61%, respectively. The incidence of total sepsis and LOS in infants <1,000 g of birth weight was significantly higher than that in infants who weighed >1,000 g at birth, whereas there were no significant differences in the incidence of EOS between the different birth weights. Methicillin-resistant Staphylococcus aureus was the most common pathogen involved in morbidity and mortality of neonatal sepsis. Significant center differences were observed in the incidence of LOS, but not EOS. Conclusions: The majority of culture-proven neonatal sepsis is LOS, which differs among centers, especially in infants who weigh <1,000 g at birth in Japan. We consider that it is important to control nosocomial infection in newborn care units to further reduce the morbidity of neonatal sepsis in Japan.

Pulsation Detection from Noisy Ultrasound-Echo Moving Images of Newborn Baby Head Using Fourier Transform

In order to detect pulsation from a series of noisy ultrasound-echo moving images of a newborn babys head for pediatric diagnosis, a digital image processing system capable of recording at the video rate and processing the recorded series of images was constructed. The time-sequence variations of each pixel value in a series of moving images were analyzed and then an algorithm based on Fourier transform was developed for the pulsation detection, noting that the pulsation associated with blood flow was periodically changed by heartbeat. Pulsation detection for pediatric diagnosis was successfully made from a series of noisy ultrasound-echo moving images of newborn babys head by using the image processing system and the pulsation detection algorithm developed here.

A Real-Time Processing System for Pulsation Detection in Neonatal Cranial Ultrasonogram

In order to observe artery pulsation in the neonatal cranium at the site of pediatric diagnosis, a real-time processing system was developed for continuous detection and display of artery pulsation, from the moving images of the neonatal cranial ultrasonogram. The pulsation images were continuously generated by calculating the absolute difference between each pixel value at the two images corresponding to about half a heartbeat interval. The system was confirmed to process and continuously display at intervals of about 150 ms while capturing the echo images at the video rate of 30 ms, showing that the system performance was good enough to observe the artery pulsation in real-time. By monitoring the pulsation images continuously redisplayed, the critical conditions of the echo image such as the sway of the ultrasound probe could be easily avoided at the site of diagnosis.

Motion analysis of artery pulsation in neonatal cranial ultrasonogram

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.

Effects of Phototherapy on Serum Unbound Bilirubin in Icteric Newborn Infants

Sera from 39 preterm and 35 full-term infants with hyperbilirubinemia, undergoing phototherapy continuously for 48 h, were assayed for unbound bilirubin by the peroxidase oxidation method. Assessment was done to determine the influence of therapeutic exposure to light on the serum unbound bilirubin concentrations in preterm and full-term infants. At 24 and 48 h after initiation of phototherapy, the unbound/total bilirubin ratios, as well, as the serum total and unbound bilirubin levels showed statistically significant declines of values in both preterm and full-term infants. It is concluded that, following phototherapy, the serum levels of unbound bilirubin decline more conspicuously than the decrease in serum total bilirubin levels.

Real-time visualization of pulsatile tissue-motion in B-mode ultrasonogram for assistance in bedside diagnosis of ischemic diseases of neonatal cranium

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.

Three-dimensional shape construction of pulsatile tissue from ultrasonic movies for assistance of clinical diagnosis

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.

Three-dimensional visualization of pulsatile tissue-motion in B-mode ultrasonogram of neonatal cranium

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.

A new imaging technique on strength and phase of pulsatile tissue-motion in brightness-mode ultrasonogram

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.

Bedside assistance in freehand ultrasonic diagnosis by real-time visual feedback of 3D scatter diagram of pulsatile tissue-motion

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.