Sachiko Goto

Detection of defects at BGA solder joints by using X-ray imaging

In the surface mount technology, a ball grid array (BGA) has been used in the production of PC boards. This paper deals with the detection of defects at BGA solder joints in PC boards by using X-ray imaging. Types of defects at BGA solder joints are solder bridge, missing connection, solder voids, open connection and misregistration of parts. The problems of image analysis for the detection of defects at BGA solder joints are the detection accuracy and image processing time according to the speed of the production line. To get the design data for the development of the inspection system used in the surface mount process, it is important to develop image analysis techniques based on X-ray image data. At the first step of our study, we attempt to detect the characteristics of the solder bridges based on the image analysis technique.

Analysis of BGA defects by tomographic images

To improve the cost of performance in manufacturing IC packages, it is required to inspect BGA defects in the online process. The problems of image analysis for the detection of defects are the detection accuracy and image processing time according to a line speed of production. Using the X-ray penetration equipment, we have captured images of an IC package to search an abnormal BGA. To get design data for the development of the inspection system, which can be used easily in the surface mount process, we tried to capture the tomographic images utilizing the latest imaging techniques.

Measurement of patient exposure dose on X-ray screening mammography

X-ray mammography is the most effective method to produce a high photographic sensitivity in the early detection of breast cancer in which palpation is impossible. Mammography can be adapted to a screening check aimed at discovering abnormal remarks in females without the subjective symptom. However, in order to justify examining a seemingly healthy group in screening mammography, it is necessary to perform with an appreciation of the risk of carcinogenesis that may be associated with the absorbed radiation dose to the breast (patient exposure dose), and to guarantee an optimization of radiological protection. To do so, it is necessary to control the individual patient exposure dose in screening mammography. Moreover, when estimating patient exposure doses, it is important that breast composition is investigated objectively. In this study, a breast dosimetry system that includes digitization of a mammogram for investigating the individual breast composition was built on the basis of the dosimetry method for quality control of screening mammography. It is thought that this system has 10% or less of an error factor including the error determination of breast composition. Patient exposure doses of 124 examples from 76 patients in Japan were actually estimated by this system. Their values were clearly lower than the maximum acceptable dose recommended by the American College of Radiology and Japan.

Observation of activation brain areas in response to the stimulation by the right hand movement of Kawahira method using fMRI

The purpose of this paper is to investigate the contribution of 3.0 T (tesla) functional magnetic resonance imaging (3T-fMRI) to analysis of effecti veness of various approaches to stroke rehabilitation. Using fMRI, we observed the activation of brain structures in response to stimulation to the right hand by Kwahira method that is intensive exercise therapy.

The phantom for quality evaluations of the nonlinear noise reduction filter in multidetector row computed tomography

In this paper we propose the phantom for quality evaluations of the nonlinear noise reduction filter in multidetector row computed tomography (MDCT). A nonlinear filter is a filter whose output is not proportional to its input (CT number or contrast value). Generally, a standard phantom for CT cannot be used for the quality evaluation of such a filter. The maximum feature of our phantom is being able to obtain edge spread functions of a maximum of six edge intensities under the influence of a certain maximum contrast by choosing a slice position...The edge-preserving adaptive filter for selectively eliminating noise in low-dose scanning known as the Quantum Denoising System (QDS) developed by Toshiba Medical Systems was chosen as a nonlinear noise reduction filter for this study. For evaluation of the filter characteristics, three types of evaluation, the noise statistical values (mean and standard deviation of CT numbers), noise characteristics (noise Wiener spectrum, WS) and resolution characteristics (modulation transfer function, MTF) were measured using the phantom. As a result, the statistics value of obtained noise, and WS and MTF were able to demonstrate the performance of the filter clearly. Further, our phantom was able to investigate the capability of edge-preserving adaptive filters such as QDS using MTFs with different edge intensities. As compared with a digital phantom, our actual phantom is considered to be a useful tool in order to know the overall processing results containing the feature of each CT scanner and reconstruction filter of manufacturing companies and the performance of a nonlinear noise reduction filter.

Increasing the sensitivity of the dosimetry system for high energy x-rays, using Gafchromic EBT film and a flat-bed scanner with sharp cut filters

To increase the sensitivity of the dosimetry system for high energy x-rays, using Gafchromic EBT film (International Specialty Products) and a flat-bed scanner with transparency unit (ES-2200 or Expression 1680, Epson, Inc.), the optimal sharp cut (SC) filters like optical filters to be added to the scanner were investigated. Gafchromic EBT film (EBT) has the absorption spectrum with a maximum absorption band centered at 636 nm. Consequently the response of EBT will be enhanced by measurement with red light and can be very significantly increased by using a red filter while making scanner measurements. In our research, employed SC filters were SC filter 54, 56, 58, 60 and 62 (product made from Fuji film). SC filters are defined as filters that cut off as much as possible of the wavelength light shorter than a specific wavelength, while transmitting as much of longer wavelength light as possible, within a wavelength range of 350 nm to 800 nm. Generally, it is ideal to use a narrow band pass filter. However we didn’t employ the filter because the transmissivity of the filter of film type is low or the thickness of glass type filter is large, so it is unsuitable for a flat-bed scanner. Film pieces of EBT were exposed to the following doses: 0.3 – 10.0 Gy with the 6 MV x-rays from a linear accelerator. The irradiated film pieces to which the SC filter was added were scanned and the scan data of red channel was converted into optical density. Furthermore the optical density was divided by the absorbed dose and the value was estimated as sensitivity. EBT with SC filter 62 with 50% of transmissivity at 620 nm was about 1.48 times more sensitive on the average than without a SC filter.

Measurement of Breast Density on Digital Mammograms

We built a estimating system of individual breast density from digital mammograms by using breast tissue equivalent phantoms that are able to change the mixture ratio of adipose and glandular tissue and the thickness. The method was compared with a visual assessment of breast density by the radiologists as a gold standard. The clinical image data set that consisted of 49 mammograms of 21 patients were analyzed. The average of the estimated glandular rate was 35.0%, while varying from 12.0% to 67.0%. This system can apply in clinical practice such as the visual estimation of breast density

Exploration of brain activations by passive hand movements and subject's intention based on Kawahira method using 3T-fMRI

To investigate the contribution of 3.0 T functional magnetic resonance imaging (fMRI) to analysis of effectiveness of various approaches to stroke rehabilitation, we explored brain activations by passive hand movements and subjects intention based on the repetitive facilitation exercises (RFEs) shown by KKawahira.

Detection of calcification in human breast using phase image of magnetic resonance imaging

This paper discusses about detection of calcification using phase image of MRI. Furthermore, high-pass filtered phase images of a human breast were evaluated by various echo time.

Reduction of scan time for phase image of 3T magnetic resonance imaging to detect of calcification

The high-pass filtered phase image was able to show calcification as hyperintense areas by using 3T MR equipment with a very strong magnetic field. In a T1-weighted Fast Field Echo (T1FFE) sequence, reduction of scan time is possible by adding a shifted echo parameter, although unwrapping processing technique needs to be improved.