OBJECTIVE: To investigate the basic characteristics of degradable gelatin microspheres (GMSs), including their embolic behavior and degradation periods when they are used as embolic materials in the renal arteries of rabbit models. MATERIALS AND METHODS: Based on the GMS particle size, 24 kidneys were divided into 3 groups of eight kidneys, and each group was embolized with a different GMS particle size (group 1: 35-100 micrometer, group 2: 100-200 micrometer, and group 3: 200-300 micrometer). From each group, two rabbits were sacrificed immediately after embolization (day 0), and a pair of rabbits from each group underwent an angiogram and were sacrificed on days 3, 7, and 14, respectively, after embolization. The level of arterial occlusion, the pathological changes in the renal parenchyma, and the degradation of the GMSs were evaluated angiographically and histologically. RESULTS: A follow-up angiogram on days 0, 3, 7, and 14 revealed the presence of wedge-shaped poorly-enhanced areas in the parenchymal phase as seen in all groups. The size of these areas tended to increase with the particle diameter, and persisted up to day 14. On days 3, 7, and 14, parenchymal infarctions were observed histologically in all cases, and this observation corresponded with the parenchyma being supplied by the embolized arteries. GMSs of group 1 mainly reached the interlobular arteries, while those of group 3 mainly reached the interlobar arteries. In all but two cases, the GMSs were identified histologically even on day 14, and sequential degradation was histologically identified in all GMS groups. CONCLUSION: GMSs can be used as degradable embolic materials which can control the level of embolization.
Animals ; Biocompatible Materials ; Disease Models, Animal ; Embolization, Therapeutic/*methods ; Female ; Follow-Up Studies ; *Gelatin ; Kidney/blood supply ; *Microspheres ; Particle Size ; Rabbits ; Renal Artery/drug effects/pathology/radiography ; Renal Artery Obstruction/*chemically induced ; Severity of Illness Index ; Time Factors

Data from the first trial of the computer-based nationwide common achievement test in medicine, carried out from February through July in 2002, were analyzed to evaluate the applicability of the item-response theory. The trial test was designed to cover 6 areas of the core curriculum and included a total of 2791 items. For each area, 3 to 40 items were chosen randomly and administered to 5693 students in the fourth to sixth years; the responses of 5676 of these students were analyzed with specifically designed computer systems. Each student was presented with 100 items. The itemresponse patterns were analyzed with a 3-parameter logistic model (item discrimination, item difficulty, and guessing parameter). The main findings were: 1) Item difficulty and the percentage of correct answers were strongly correlated (r=-0.969to-0.982). 2) Item discrimination and the point-biserial correlation were moderately strongly correlated (r=0.304 to 0.511). 3) The estimated abilities and the percentage of correct answers were strongly correlated (r=0.810 to 0.945). 4) The mean ability increased with school year. 5) The correlation coefficients among the 6 curriculum area ability scores were less than 0.6. Because the nationwide common achievement test was designed to randomly present items to each student, the item-response theory can be used to adjust the differences among test sets. The first trial test was designed without considering the item-response theory, but the second trial test was administered with a design better suited for comparison. Results of an analysis of the second trial will be reported soon.