Reprojection Method(RPM)using computed tomography(CT)data can create simulating images of plain X-ray film. We could create material extracted images by selecting projected CT values, and created tomographic images by selecting spatial values. Virtual X-ray source can be set anywhere. So it can create stereographic images composed of a pair of beam's eye view, and can create panoramic images to set the source inside the volume data. Since RPM does not need the binaryzation process, the densities of the image reflect the original CT value of each voxel. RPM using CT data is a useful method to get the most information regarding X-ray attenuation and to cope with the fast scan CT system.
To examine the ability of magnetic resonance imaging to visualize the diamagnetic susceptibility effects of calcification, phantom experiments using small lead balls in a dilute solution of copper chloride in water were carried out. Gradient echo phase images of the phantoms were obtained using varying imaging parameters(TR, TE, flip angle, slice thickness), and phase shift due to the lead balls was measured. Five choroid plexuses and three pineal glands with calcification were also examined using gradient echo phase images. As a result, it could be seen that the phase shift increased in proportion to both echo time and the ratio held by lead and calcification in a voxel(partial volume effect), and was independent of repetition time and flip angle. It could be confirmed that the gradient echo phase images are useful for detecting the diamagnetic susceptibility effects of calcification.
Two types of imaging plates(HR and ST)are used for the Fuji Computed Radiography Systems. ST has about two times the speed and about a 50% resolution at 2 cycles/mm compared with HR. Therefore, there is less moise with ST in comparison with HR at the same incident dose for imaging plates. In this study, the noise of HR and that of ST with the same resolution using image processing was studied. As a result, the noise of ST with image processing was seen as being lower than that of HR at the same incident dose for imaging plates. It could be concluded that the image quality of ST with high resolution by image processing is superior to HR under the same incident dose conditions.
As a basic study on the echo trigger pulse propagation in the human body in relation to the Extracorporeal Shock Wave Lithotripter, an investigation on the problems of propagation and convergence of ultrasonic pulses ejected from arc-shaped piezoceramic transducers into the human body model was carried out, together with a comparative study of the results of a computer simulation with those of the experiment. The numerical analysis was performed using a newly-devised method similar to the so-called FE-TD method widely used for analyzing electromagnetic fields.
Mathematical model of Wiener supectrum of radiographic mottle was derived. Radiographic mottle is composed of quantum mottle, structure mottle and film granularity. Especialy, the Wiener spectrum of structure mottle is expressed as a function of inverse relative exposure and square MTF of screen film system. As one applications of the Wiener spectrum equation, Wiener spectral values as a function of density coverage can be calculated by using BRH's published data of Lanex Fine/OG system at 1.0 of density. Then a requirment for decreasing film granularity in relatively higher density area nay be obtained. Finally, NEQ(u)is expressed as a function of density and spatial frequency.
The clinical heating properties of a RF interstitial hyperthermia unit was clarified using thermography and thermocouples. In addition, optimal spacing of an implanted needle in case of 192-iridium brachytherapy with interstitial hyperthermia was discussed. It was found that the spacing of an implanted needle should be between 1-1.5 cm, electrodes implanted must remain in parallel, the number of those implanted need to be even, and the frequency mode must be non-coherent when the effective thermal dose area(>42℃)is 60-80% of the volume surrounded by the electrodes, reapectively. In case of hyperthermia, in combination with iridium wires, it was found to be close to 1 cm clinically.
Recently, an increasing number of asymmetric screen-film systems have been becoming to be used for radiographs. In this paper, some of the characteristics of asymmetric system including reversal development are discussed. Then, the unsharp masking MTF is derived from it's overall MTF which have already been obtained in the other our investigation. Consequently, the edge enhanced clinical radiograph of a hand bone is demonstrated by using the asymmetric screen-film system.
Currently, in Japan, mass screening for breast cancer is conducted by palpation. However, this type of mass screening presents problems due to variations in doctor's ability to detect cancer, and regarding the difficulty of detecting nonpalpable lesions. To solve this problem, it is necessary to introduce mammography, which is already well established in many countries in the West. The fast step is the development and standardization of equipment and techniques for mammography. Concerned groups are already working on the preparation of guidelines for standardization. This paper presents an outline of guidelines of mammography and related information.
Currnetly, in Japan, plans are being developed for introducing mammography examinations as a breast cancer screeing procedure. The International Electrotechnical Commission(IEC)has an active role to in establishing standards for mammography. To prepare a draft of national standards for mammography units, and discuss the draft of the IEC standards, the Japan Industries Association of Radiation Apparatus(JIRA)established last year a new technical subcommittee(Subcommittee SC-2205). The subcommittee also supports the Japan Radiological Society Committee on "Making Guidelines for Mammography" in preparation of protocols for the performance of the mammography System and the establishment of quality control standards. In this sumposium, we introduce our proposals for the basic performance of the mammography units and quality control standards in mammographic screening.
The most important thing in mammographic breast cancer screening is the false negative case as lesseing as possible. In analysis 51 cases breast cancer patient's mammogram, 3 cases(5.9%)is false negatine interpretations by tumor tissues is overlapping of glandular breast tissues and tumor size is little. The effectiveness and success of mammographic screening depends on consistent production of high-resolution, high-contrast, low-dose mammographic images. High quality mammograms will higher the detection rate of early breast cancer, and many women will savedd from breast cancer.
I had trainning about the breast cancer mass screening system and mammography technic in Finland from the 2nd of February to the 29th of March in 1994. A nationwide mammography screening program started in Finland in 1987. Screening covers women aged 50-59 years. Personal invitation letters are sent and two-view(cranio-caudal and medio latelo oblique)screen-film mammography are performed as the only screening examination with two year intervals. Participation has averaged 89% and the breast cancer detection rate has averaged 0.36% from 1987 to 1991. The quality control of mammography unit and image is guided by law and checked by the Medical Physicist of the Finnsh Center for Radiation and Nuclear Safety on an irregular basis, but at least once every 5 years.
Breast examinations have generally been performed in specialized hospitals, resulting in wide variation in the techniques used at different facilities. In order to standardize mammographic techniques, the Japanese Society of Radiological Technology established a working group. The purpose of the group was to spread and promote the knowlege and the practices of mammography. The group held seminars on mammography at each branch of the society over a period of two years, from 1992 to 1994. In this symposium, we report on the issue of introducing X-ray mammography into the breast cancer screening procedure based on analysis of the problems and considerations of the facilities, which were brought up in the course of the seminars or expressed in the questionnaire afterward.