With a view to improving the correlation of liver scintigraphy using ^<99m>Tc-DTPA-galactosyl human serum albumin(GSA)with hepatic function as indicated by indices such as LHL15, HH15, and laboratory data, the present study was carried out to set up a calibration curve(CC)for visual analysis. The application of 7 patterns of CC with different settings to a 1-min image(5 to 6 minutes after radiotracer injection)in 98 cases led to the preparation of 686 images whose correlation with hepatic function was examined by 15 observers via the grade classification of a five-point scoring system using visual analysis. The grade classification was as follows : grade 1(faint cardiac blood-pool image), grade 2(slight cardiac blood-pool image compared with liver uptake), grade 3(almost the same appearance of cardiac blood-pool image and that of liver uptake), grade 4(intense cardiac blood-pool image associated with possible liver uptake), and grade 5(very slight liver uptake). The five-point scoring system could be used for CC slopes of 4.21, 4.79 and 2.79(the above coorelation was strongest for 4.21). The significance of inter-grade group differences in ICGR15, LHL15 and heart/liver ratio was examined according to slope. With the CC slope of 4.21, a significant inter-grade group difference was observed between grades 1 and 2, grades 2 and 3, grades 3 and 4, grades 4 and 5. In conclusion, when the value of the CC slope was 4.2, it was considered appropriate for grade classification on a five-point scoring system using visual analysis.
The visual evaluation of x-ray images is very useful. We applied two different methods of evaluation for breast computed radiography(CR)images in this work : one method was an analytical evaluation that detected the strongest "RE" parameter, while the other method was a preference evaluation that selected the most suitable "RE" parameter. We found little difference when the analytical method was used for the evaluation of breast CR images, whereas remakable differences were obtained with the preference method. To conclude, it is very important to use a proper method in the visual evaluation of x-ray images.
Relative convertsion factor(Gx)measurement with certain reappearance is necessary for the management of fatigue over the course of time in an image intensifier(I.I.). Therefore it is desirable to make the measurement method as close as possible to the Japanese Industrial Sandards(JIS). We studied a relative Gx measurement method on the premise that it is done by the user. Study of both output luminance and exposure rate indicated that Gx depends on radiation quality. The exposure rate increased by up to about 10% as a result of back scatter from the I.I. when measuring. We measured luminance through the first lens because it is difficult to measure I.I. output fluorescence by output luminance. When the distance between first lens and the luminance meter is within 30cm to 120cm, output luminance is not influenced by measurement distance. When measuring reflection luminance from the distributor mirror, we must pay attention to the distribution rate. A luminance measurement area within the cine iris diameter makes it possible to measure from the cine camera output.
The double-echo steady-state(DESS)sequence is a technique for contrast improvement for differentiating fluid from tissue in the knee. This study was designed to evaluate the performance of the DESS sequence in detecting structures in the knee in comparion with other sequences. The same asymptomatic knees were imaged in both the sagittal and coronal planes using various pulse sequences : T_1-, T_2- and proton density-weighted spin echo, T_2-weighted fast spin echo, three-dimensional FISP and three-dimensional DESS. Our results suggest that DESS imaging provides good visualization and satisfactory diagnosis for the any structure in the knee, and is especially useful for evaluation of catilage and joint effusion. Furthermore, as this sequence provides three-dimensional acquisition, it is possible to generate the required planes using the multiplanar reformation technique.
When the PMT and preamplifier are out of order, it is impossible to make a correct diagnosis because of defects on the scintigram. However, repair of the equipment may take a long time. In order to perform emergent whole-body scintigrams in the event of such breakdowns, we have developed a new approach named the lead-shield method. The major principles of this method involve placing a lead shield on the gamma camera such that it corresponds to the area of the abnormal PMT and making use of the normal area of the detector. The lead shield, 2mm thick and 1.5 times as wide as the defect on a planar image, was situated perpendicular to the scan plane of the whole-body scintigram. The results showed that whole-body scintigrams obtained by the lead-shield method had the same quality as those obtained by the conventional method, and the spatial resolution and uniformity showed nearly no change despite some disadvantages such as lower sensitivity and shorter scan length. The lead-shield method can be a useful tool for the performance of whole-body scintigrams in cases of emergency, when the PMT and preamplifier are out of order.
Using a questionnaire we investigated whether radiation exposure is correctly understood by medical doctors(n=140), nurses(n=496)and the general public(n=236). Thirty-three percent of medical doctors, 53% of nurses and the general public did not know who is legally allowed to irradiate the human body. Forty-five percent of doctors, 63% of nurses and 48% of the general public complained of anxiety about radiation injury. Fifty-six percent of patients did not ask medical doctors or nurses for an explanation of the risk of exposure. Moreover, 64% of doctors did not explain the risk to patients. In addition, 21% of doctors, 46% of nurses and general public incorrectly understood that x-rays remain in the examination room. Twenty-seven percent of doctors, 49% of nurses and 80% of the general public did not know the "ten-day rule". In conclusion, the results of this questionnaire indicated that basic knowledge about radiation exposure was not adequate. To protect against medical radiation exposure, personnel who are licensed to irradiate to the human body should be well recognized by medical staff and the general public. It is also important that informed consent for radiological examinations be based on fundamental knowledge about radiation exposure. Therefore, to reach a general consensus on radiological examinations and to reduce individual exposure, general public education regarding radiation protection is required. Postgraduate education on radiation protection for medical doctors and nurses is also strongly recommended.