Masayuki Fukuzawa

Simulative operation on congenital heart disease using rubber-like urethane stereolithographic biomodels based on 3D datasets of multislice computed tomography

OBJECTIVE Stereolithographic biomodelling is a technique where photosensitive liquid resin is polymerised with a pinpoint laser beam controlled by three-dimensional (3D) datasets. This study was designed to assess whether a stereolithographic biomodelling technique is applicable for precise anatomical diagnosis and simulation surgery of complicated congenital heart disease. METHODS Twelve stereolithographic biomodels were manufactured with multislice computed tomography (MSCT)-based 3D datasets. They were made of photosensitive liquid epoxy or urethane. RESULTS All the solid epoxy and rubber-like urethane biomodels reproduced the complex anatomical structures of the arteries and veins in congenital heart diseases. Furthermore, the rubber-like urethane biomodels allowed the surgeon to cut and suture, thus facilitating the simulation of the surgical operation. CONCLUSIONS Stereolithographic biomodelling is a promising technique for the preoperative practice and simulation of individual surgery. This technique would be useful in the planning of novel and innovative surgical procedures of congenital heart disease.

Correlation between residual strain and electrically active grain boundaries in multicrystalline silicon

We report the correlation between residual strain and electrically active grain boundaries (GBs) in multicrystalline silicon. The former concerns the process yield, and the latter affects the solar cell efficiency. The distribution of strain was imaged by scanning infrared polariscope, and the electrically active GBs were characterized by electron-beam-induced current. Large strain was detected near multitwin boundaries and small-angle GBs. The multitwin boundaries are electrically inactive, while small-angle GBs act as strong recombination centers. It indicates that the electrical activities of GBs are not directly related to the residual strain.

Photoelastic characterization of Si wafers by scanning infrared polariscope

A small amount of birefringence caused by the photoelastic effect from residual strains, crystal-defects-induced strains, and process-induced strains in Si wafers has been measured by using an improved version of a scanning infrared polariscope (SIRP). The SIRP presented here has high sensitivity sufficient to detect the small amount of strain induced near the wafer-supporting finger by the wafer weight itself. It is found that an anomalous amount of strain is induced by slip-line generation during the thermal process and also that a concentric ring pattern of strain is induced by OSF rings. From these results, it is suggested that SIRP is very useful for Si wafer inspection and Si process evaluation in various phases.

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.

Development of an e-learning back-end system for code assessment in elementary programming practice

In this paper, we present an e-learning back-end system which cooperates with a learning management system (LMS). Our back-end system is aimed at fair and effective assessment in a class of elementary programming practice. While most LMSs provide basic functions to support various learning courses, this back-end system complements such conventional LMSs by providing the following specialized functions: syntax check of codes, plagiarism detection, and automated black-box testing. Our specialized back-end system makes a general-purpose LMS more useful for both students and teachers at low cost. The back-end system gets account information about a student from the front-end LMS such as Moodle when a student submits a report. This approach makes the back-end system maintenance-free from user table and enables single sign-on (SSO) for all LMS users. In order to accept simultaneous requests from numerous students and to respond without delay, the system is designed to minimize the amount of file locking and dynamic page generation. The back-end system is used in practical classes, and students of the classes feel no stress on the response time.

Fine structures of residual strain distribution in Fe-doped InP-(100) wafers grown by the LEC and VCZ methods

By using a high-spatial-resolution scanning infrared polariscope, in-plane components of residual strain have been characterized quantitatively in 2′Φ wafers of Fe-doped InP( 100) single crystals grown by the liquid-encapsulated Czochralski (LEC) and the vapor pressure controlled Czochralski (VCZ) methods. The twodimensional distribution maps of LEC-grown wafers reveal characteristic fine structures such as slip-like patterns originated from crystallographic glides during the crystal growth process, highly strained spots and filaments due to inclusions or voids inside the wafer, or due to scratches on the surface. The sliplike patterns are seldom observed in the VCZ-grown wafers. The residual strain value averaged over the whole region of wafer is also examined, together with etch pit density and resistivity, as a function of the solidified fraction. It is found that the residual strain in the Fe-doped InP crystals grown by the LEC and VCZ methods mainly depends on the thermal stress during the growth process rather than on the impurity-hardening effect of Fe.Key words: InP, infrared polariscope, liquid-encapsulated Czochralski (LEC) method, residual strain, vapor pressure controlled Czochralski (VCZ) method

Grain Boundaries in Multicrystalline Si

We report the electrical, structural and mechanical properties of grain boundaries (GBs) in multicrystalline Si (mc-Si) based on electron-beam-induced current (EBIC), transmission electron microscope (TEM), and scanning infrared polariscope (SIRP) characterizations. The recombination activities of GBs are clearly classified with respect to GB character and Fe contamination level. The decoration of Fe impurity at boundary has been approved by annular dark field (ADF) imaging in TEM. Finally, the distribution of residual strain around GBs, and the correlations between strain and electrical properties are discussed.

Effect of Crystallinity on Residual Strain Distribution in Cast-Grown Si

We report the correlation between the crystallinity of ingots grown by the directional solidification technique and the residual strain and dislocation distribution. It was found that mono-like ingots have a 20–25% higher averaged residual strain than multicrystalline Si ingots grown under the same conditions. However the existence of local high-strained areas, which were frequently found in multicrystalline Si ingots, is reduced in mono-like Si ingots. In addition, a reduction in dislocation density was observed. This effect and the decrease in local high strain could be attributed to the decrease in grain boundaries in the mono-like ingots.