Toshinori Maruyama

Study of Positioning Techniques for Skull Radiography using CT images

We describe a new method of positioning techniques in radiology. The positioning technique is important in obtaining an accurate diagnostic information. It is desirable to perform the positioning accurately. As X-ray films are usually used in radiography, the development of the films becomes necessary. In this study, we propose a new positioning training method using digital image processing. We scan the skull phantom by CT and obtain the CT images. We produce the necessary plane images for diagnosis from CT images. We develop a method which produces the plane image of the phantom placed under the X-ray tube in real time. Our method is useful for helping the positioning practice as a teaching material without X-ray exposure and development of X-ray films.

Study of Positioning Techniques for Skull Radiography

We describe a new method of positioning techniques in this paper. The positioning technique is important to obtain accurate diagnostic information in radiography. As X-ray films are usually used in radiography, the development of the films becomes necessary. It is desirable to perform the positioning accurately and to confirm the results of the positioning in short time. In this study, we construct an image database which is related to the positioning image of the phantom and its radiographic image. We develop a system which displays the radiographic image by detecting the position of phantom in real time. Furthermore, we use the V-filter to improve the image quality of radiographic images. The V-filter is effective in extracting the region of interesting accurately. It is expected that our method is useful for acquiring of the positioning techniques

Elimination of Gridlines in X-ray Imaging for Mammography

Mammography X-ray equipment uses the radiographic grid in order to remove the scatter radiation and to improve image contrast. The gridlines, such as striped lines, appear on the film and the gridlines are considered that diagnostic information may be impaired as an artifact. In this study, we developed the image processing technique which eliminated gridlines on films using digital image processing. We exposed the phantom, improved the gridlines image and detected the ripple components of the gridlines image. We could eliminate the gridlines from the calcifications image by using the ripple components of the gridlines image. By using digital image processing techniques, we could eliminate gridlines and extract the region of calcification. It was suggested that the accuracy of the mammographic diagnosis could be improved.

Detection of calcification using high-pass filtered phase image in magnetic resonance imaging for breast cancer screening

To achieve detection of calcifications using magnetic resonance imaging (MRI) for breast cancer screening, we investigated combinations of an echo time (TE) and a high-pass filter size on phase images using a breast phantom. The breast phantom was made from gel area of 0.1 mmol/L gadopentetate dimeglumine and 2.0 wt% agar containing imitation calcifications to simulate calcification in the breast. To use the phase image for calcification assessment, optimization of TE was required since a difference of phase is enhanced at sufficiently long TE. However, longer TE tends to increase the static field inhomogeneity effects. To remove the static field inhomogeneity effects, we employed a high-pass filter processing. Then, several different filter sizes were tested to optimize the visualization of calcification. TE of 48 msec had the highest contrast between imitation calcifications and gel area. The high-pass filter size of 64×64 pixels was able to remove efficiently the background phase effects. The high-pass filtered phase image was able to show imitation calcifications as hyperintense areas. Although the limit of detection of imitation calcifications was 1.0 mm, it suggests a possibility that the high-pass filtered phase image is able to use for breast cancer screening and diagnosis without pain by compression or the use of ionizing radiation.

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.

CT image based training tool for positioning in radiography

An appropriate and quick positioning technique is essential for obtaining accurate diagnostic information in radiography. In this study, a computed tomography (CT) image-based training tool which can assist the students is developed and the X-ray training method using CT images for positioning in radiography is proposed. First, from the CT image data of the phantom scanned beforehand, the three-dimensional (3D) phantom using solid model is constructed and the positioning on a personal computer (PC) using the 3D phantom is performed. Next, the plane image corresponding to the displayed phantom position from the CT image data is calculated. By using our developed tool, it is expected that students could perform the positioning training without having to expose X-rays and develop the films.

CT image-based training system for positioning in radiography

In radiography the human body must be accurately and quickly positioned under X-ray equipment in order to obtain an image of the examined organ. The good positioning skill of the radiological technologist is essential for obtaining accurate diagnostic information of an examined organ and for reducing X-ray exposure in radiography. In this study, we developed a computed tomography (CT) image-based training system which could assist the students to train the positioning practice. By using a personal computer (PC) the positioning could be simulated. First, from the CT image data of the phantom scanned beforehand, we constructed the three-dimensional (3D) phantom based on a solid model and we performed the positioning of the 3D phantom on the PC. Next, we calculated the plane image from the CT image data corresponding to the positioned phantom and displayed the calculated plane image. By using our proposed training system, it was expected that students could perform the positioning training at the same time without having to expose X-rays and develop the films.

Elimination of gridlines in X-ray image

The mammography X-ray equipment uses a radiographic grid in order to remove the scatter radiation and improve image contrast. The grid causes striped lines to appear on the film and may degrade diagnostic information. In this study, we propose a new method which reduces the noise caused by the grid on mammographic film using digital image processing techniques. We considered a method of eliminating gridlines based on the mechanism of gridline appearance and investigated the validity of image filtering. First, we exposed a phantom and selected a region of gridlines for study. We smoothed gridline image based on the line profile. We detected the ripple components of the gridlines and subtracted them from the micro calcifications image. Next we performed median filtering and the V-filtering as a method of image filtering. Then, we calculated the standard deviation of the line profile and signal to noise (SN) ratios in the micro calcifications region. The standard deviations of the line profile processed by the two methods were decreased and the SN ratios of the respective images were increased. The SN ratio of the image processed by median filtering after the V-filtering was approximately equal to that of the image processed by subtracting ripple components. Thus, we could confirm the validity of image filtering. It was found out that our proposed image filtering method was useful for eliminating gridlines in the X-ray image.

Imaging techniques for positioning training in radiography

The positioning skill of the radiological technologist is essential for obtaining accurate diagnostic information of an organ and for reducing X-ray exposure in radiography. We previously reported on the development of a computed tomography (CT) image-based training tool. A three-dimensional phantom was produced by using computer graphics. Positioning was performed on a PC, and the plane image corresponding to the performed positioning was produced and displayed. In this study, the algorithm which produces the plane image from the CT image data was improved in order to obtain an image quality comparable to the X-ray image obtained by the Computed radiography (CR) system. The CT value and linear attenuation coefficient were calculated from the CT image data based on the fundamental interactions between X-rays and an object. By using the linear attenuation coefficient, a plane image with the same image quality as the CR image could be produced.