For implementation of computer-aided diagnostic systems for chest radiographs in the clinical environment, it is necessary to correctly identify two view positions [posteroanterior (PA) and lateral views] and four orientations (upward, downward, leftward, and rightward)for chest radiographs. In picture archiving and communication system (PACS), the information on the view position and orientation for chest radiographs is often not recorded or is recorded incorrectly. The purpose of this study was to develop a computerized method for correctly identifying view position and orientation for chest radiographs by using a template matching technique. Our basic approach is to find the most similar template to an unknown chest image by examining the similarity of the unknown chest image with a number of templates for PA and lateral views at the four image orientations, and to determine simultaneously the view position and orientation for the unknown chest image. All upward templates were produced from the PA or lateral images for upward orientation for various patient sizes. By rotating the upward templates, we produced the templates for downward, leftward, and rightward orientations. To evaluate the similarity of a test image with all templates, the cross-correlation values of the test image with all templates were obtained. The view position and image orientation for the unknown image was considered to be identical to those for the template with which the largest cross-correlation value was obtained. Our results indicated that all cases of 200 PA and 200 lateral views were correctly identified in terms of the view position and image orientation.
Our study was carried out to compare and evaluate two types of grids(single and cross types)for the removal of scattered X-rays exclusive to mammography in an ACR-specified 156 model phantom using fuzzy measure theory (fuzzy measure and its fuzzy integration). When three simulated shadows of the breast phantom (fibrous, calcified, and tumor) were integrated, the cross grid (Gc) showed a slightly higher evaluation value than the single grid (Gs). In addition, when two shadows were combined or each shadow was alone, the Gc was evaluated as 2% or 3% higher. It is difficult to determine the physical properties of a grid for removal of scattered X-rays exclusive to the breast considering the structure of equipment, but if a visual and subjective evaluation is quantitatively conducted by applying fuzzy kinetics, comparison and evaluation can be carried out.
SPECT images reconstructed by the ordered subsets expectation maximization (OS-EM) method are known to have fewer artifacts induced by the nearly high-count background organs. The aim of this study was to determine whether the OS-EM method is effective in reducing artifacts induced by the high radioactivity of liver compared with the filtered back projection (FBP) method using a heart phantom with a liver object. Heart and liver phantoms were laid to overlap each other by 2 cm, and the liver/heart radioactivity(L/H) ratios were 0:1, 2:1, and 6:1. Short axial images of cardiac SPECT were reconstructed by OS-EM and the filtered back projection (FBP) method, and counts profiles were obtained for both methods. In both methods of image reconstruction, artifactual higher counts in the inferior wall of the heart were observed as the L/H ratio increased. When compared with the L/H ratio of 0:1, the increase in relative counts of the L/H ratio of 2:1 in the inferior wall showed a similar value for both methods(OS-EM: +9.7%, FBP: +11.6%). With the L/H ratio of 6:1, the OS-EM method showed a lesser increase in relative counts of the inferior wall than with the FBP method (OS-EM: +24.5%, FBP: +38.9%). Moreover, the areas of increased counts were smaller. In conclusion, the OS-EM method was thought to be more useful than the FBP method in reducing the increase in artifactual counts caused by the high radioactivity of liver.
We constructed an Electronic Medical Record (EMR) and Picture Archiving and Communication System (PACS) in December 1999, and established a satellite clinic 5 km away from the core hospital in November 2001. Both medical doctors and patients were exchanged between the two institutes. Because it was necessary for both institutes to use the same medical information and medical images, we re-constructed both the PACS and EMR using high-speed cable network technology.
The essential factors for an immobilization device in pediatric CT are 1)absence of artifacts, 2) safety, 3)no disturbance of the patient's sedation, and 4)ease of handling. We evaluated the suitability of a commercially available vacuum-type immobilization device designed for radiation therapy (Vac-Lok) that meets these requisites. There were no artifacts in scans of the water phantom. The device easily immobilized the patient, was quick to release, and was superior to previous immobilization systems, according to replies to a questionnaire administered to physicians, technologists, and nurses. Schedule delays were reduced by using this device to examine sedated patients (up to 1 year of age). Despite these advantages, the device was too small to immobilize both extremities together when examining older patients. In order to overcome this problem, we invented a special immobilization device for pediatric CT. The new device could be applied to taller patients, up to 85 cm in height (the average height of 2-year-old infants), and was able to contribute to efficient utilization of the examination room.
The X-ray Systems Study Group, in an attempt to determine the current status and changes in the state of X-ray equipment, reception systems, and equipment control, conducted investigational research by distributing a questionnaire survey to 400 facilities. The rate of recovery was 33%. The capacity of transformers has been increasing in spite of the three-phase 415 V decrease in the power supply of X-ray equipment. Among high-voltage generators, inverter-type X-ray equipment accounted for 81.3% of units. The ratio of the X-ray tube of a conventional rotational system to that of a high-speed rotational system was 1:3, and 54.9% had target angles of 12°. Many X-ray tubes had a heat capacity of less than 200-300 kHU. The body parts that had the shortest times on radiography were adult chest and pediatric chest. In many cases, the shortest time used was 10 msec. Facilities in which the shortest time was less than 10 msec accounted for almost half of the total number. Facilities where the radiation dose of radiography had decreased showed 1/4 of the digitalization whole. Measurement was carried out when the equipment was bought in 94.9% of facilities, and measurement when the service contract was finished was done in 77.1% of the responding facilities.
X-ray equipment has seen advances in inverters and the digitalization of reception systems. The X-ray Systems Study Group, in order to examine changes in the conditions of radiography, including pediatric radiography, variations in shortest irradiation time, and standardization of the conditions of radiography, carried out investigative research using a questionnaire survey that was sent to 400 facilities. The recovery rate was 33%. In terms of the reception system, half of the general radiography systems were using computed radiography (CR). Seventy percent of respondents used an intensifying screen and film (S EF) in stomach double-contrast radiography. About 80% used digital radiography (DR) and digital subtraction angiography (DSA) in aorta abdominalis angiography. At least 70% of high-voltage generators were of the inverter type. The conditions of radiography were not greatly influenced by changes in reception systems and X-ray equipment. Many pediatric radiographies were carried out by radiological technologists. We consider it useful to conduct such survey investigations.