Biomedical subjects
Publications and source records attributed to T Tagami.
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PURPOSE: This study was designed to compare the sensitivity of T1- and diffusion-weighted images for the assessment of brain maturation in human brains. METHODS: T1- and diffusion-weighted images were obtained in 32 children without neurological abnormalities or growth retardation. The ages at which signal intensity changes of white matter on T1-weighted images and diffusional anisotropy appeared were compared. RESULTS: In the optic radiation, diffusional anisotropy was observed in neonates < 1 month old, whereas signal intensity became high after 1 month old. In the frontal lobe, diffusional anisotropy began to appear after 1 month of age, but signal intensity became high after 6 months of age. These visual findings were confirmed statistically by quantitative analysis using signal intensity ratios and anisotropic ratios. Similar findings were observed in the external capsule and the genu of the corpus callosum. CONCLUSION: In conclusion, diffusional anisotropy is a sensitive indicator of brain maturation in neonates and infants and precedes signal intensity change on T1-weighted images.
Deconvolution analysis was applied to radionuclide renal study. The purpose of this study was to clarify the underlying renal physiology that determines the shape and values of the transfer function. Analysis of the renal models revealed that the initial height of the transfer function is the ratio of the radioactivity extracted by the kidney to that in the input function. In addition, the shape of the transfer function displayed the distribution of the transit times and enabled us to evaluate the percentage of nephrons having a particular transit time. Based on the relation between the input and output function, a new method for measuring GFR or ERPF was developed in which the input function was corrected by the plasma radioactivity at 5 min after injection of the tracer. As one of the advantages of the transfer function, it was proved clinically that the contribution of the blood background is automatically eliminated from the amplitude of the transfer function. From these findings, our method for the measurement of GFR was considered superior to that proposed by Gates and highly useful for routine radionuclide renal study.